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Power Dictionary

A-H - Ampere-Hour

AC - See "Alternating Current"

ACB - Air Circuit Breaker

Accuracy - The degree of uncertainty for which a measured value agrees the ideal value.

Accuracy Class - A number used to indicate the accuracy range of a measurement transducer, according to the defined standard.

Active Material (Battery) - Material which reacts chemically to produce electrical energy when the cell discharges. The material returns to its original state during the charging process.

Active Power - A term used for power when it is necessary to distinguish among Apparent Power, Complex Power and its components, and Active and Reactive Power.

Adjustment - The operation intended to bring a transducer into a state of performance suitable for its use.

Air Blast Breakers - A variety of high voltage circuit breakers that use a blast of compressed air to blow-out the arc when the contacts open. Normally, such breakers only were built for transmission class circuit breakers.

AIS - Air Insulated Switchgear

Al - The chemical symbol for aluminum.

Alarm - A signal for attracting attention to some abnormal event.

All-or-Nothing Relay - An electrical relay which is intended to be energized by a quantity, whose value is either higher than that at which it picks up or lower than that at which it drops out.

Alley Arm - A side brace for a cross arm that is not loaded (balanced) evenly.

Alley Roadway (Lighting) - Narrow public ways within a block, generally used for vehicular access to the rear of abutting properties.

Alligator - A specialized tool attached to a hot stick used to tie a wire or cable into an insulator.

Alloy - A metal formed by the combination of two or more metals.

Alternating Current - An electric current that reverses direction at regular intervals, having a magnitude that varies continuously in a sinusoidal manner.

Ambient Temperature - The temperature surrounding an object.

American Wire Gage (AWG) - A standard system used in the United States for designating the size of an electrical conductor based on a geometric progression between two conductor sizes.

AMF (Lighting) - Average Maintained Foot-candles

Amorphous Semiconductor - A non-crystalline semiconductor material used in photovoltaic panel construction. It is easier and less costly to manufacture than crystalline, but is less efficient and degrades over time. It is also known as thin film.

Ampacity - The current in amperes that a conductor can carry continuously under given conditions of use without exceeding its temperature rating.

Ampere - The unit expressing the rate of flow of an electric current. One ampere is the current produced by a difference in potential of one volt across a resistance of one ohm; an electric current flowing at the rate of one coulomb per second.

Ampere-Hour - The use of one Ampere for one hour.

Ampere-hour capacity (storage battery) - The number of ampere-hours that can be delivered under specified conditions of temperature, rate of discharge, and final voltage.

Ampere-hour meter - An electric meter that measures and registers the integral, with respect to time, of the current of a circuit in which it is connected.

Anchor - A device that supports and holds in place conductors when they are terminated at a pole or structure. The anchor is buried and attached to the pole by way of guy wire to counteract the mechanical forces of these conductors.

Anneal - The process of controlled heating and cooling of a metal. In wire and cable products, copper and aluminum are annealed to increase flexibility while maintaining adequate strength.

Anode - 1) The positive electrode that emits positive ions and attracts negative ions, within a voltaic cell or other such device. 2) The positive pole of a battery.

Apparent Power (volt-amps) - The product of the applied voltage and current in an ac circuit. Apparent power, or volt-amps, is not the true power of the circuit because the power factor is not considered in the calculation.

Arc - A discharge of electricity through air or a gas.

Arc Flash - An arcing fault is the flow of current through the air between phase conductors or phase and neutral or ground. An arcing fault can release tremendous amounts of concentrated radiant energy at the point of the arcing in a small fraction of a second result

Armor Rod - An outer metal layer applied to a cable for mechanical protection. Armor Rods are comprised of factory formed wire, designed to be applied to a range of conductor sizes.

Array - For photovoltaic systems, a number of photovoltaic modules connected together to provide a single electrical output. Also see "Photovoltaic Array".

Arrester - Short for Surge Arrester, a device that limits surge voltage by diverting it.

Askeral - A generic term for a group of synthetic, fire-resistant, chlorinated aromatic hydrocarbons used as electrical insulated fluids.

ATC - Available Transfer Capacity

ATP - Alternative Transient Program

Automatic line sectionalizer - A self-contained circuit-opening device that automatically opens the main electrical circuit after sensing and responding to a predetermined number of successive main current impulses.

Automatic Recloser - An automatic switch used to open then reclose following an over current event on a distribution voltage (medium voltage) line.

Autonomous Photovoltaic System - A stand-alone Photovoltaic system that has no back-up generating source. The system may or may not include storage batteries.

Autotransformer - A transformer in which at least two windings have a common section. They are use to either "buck" or "boost" the incoming line voltage.

Auxiliary Power - The power required for correct operation of an electrical or electronic device, supplied via an external auxiliary power source rather than the line being measured.

Auxiliary Relay - An all-or-nothing relay energized via another relay. An example is a measuring relay, for the purpose of providing higher rated contacts, or introducing a time delay, or providing multiple outputs from a single input.

Average Maintained Foot-candles (Lighting) - (ILL x CU x LLF)/(PS x RW)

Azimuth - The angle between true north and the projection of a surface normal to the horizontal plane, measured clockwise from the north. As applied to a Photovoltaic array, 180 degrees azimuth means the array faces south.

Baker Board - An insulated platform used to work above the ground on a pole.

Balanced Load - Refers to an equal loading on each of the three phases of a three phase system...

Balanced polyphase system - A polyphase system in which both the currents and voltages are symmetrical.

Ballast - A device that by means of inductance, capacitance, or resistance, singly or in combination, limits the lamp current of a fluorescent or high intensity discharge lamp. It provides the necessary circuit conditions (voltage, current and wave form) for start

Bandwidth - The data carrying capacity of a transmission path, measured in bits or bytes per second.

Bank - A group of electrical devices, usually transformers or capacitors, connected in a way to increase capacity or to inter connect as three-phase.

Basic impulse level (BIL) - A reference impulse (voltage) insulation strength expressed in terms of the peak value of the withstand voltage of a standard impulse voltage wave. It is used to express the ability of electrical equipment such as transformers to withstand certain levels

Basic Insulation Level - A design voltage level for electrical apparatus that refers to a short duration (1.2 x 50 microsecond) crest voltage and is used to measure the ability of an insulation system to withstand high surge voltage.

Battery - A combination of two or more chemical cells connected together electronically to produce electrical energy.

Battery Tray - A contained with a base and walls for holding several cells or batteries.

Bay-O-Net - A fusing device frequently used to protect transformers and downstream devices. A Bay-O-Net fuse may include a Partial Range Current Limiting Fuse in series with n under oil fuse link.

Beam Spread - With regard to outdoor light, the angle between the two directions in a plane in which the intensity is equal to a stated percentage of the maximum beam intensity. The percentage is typically 10% for floodlights and 50% for roadway luminaries.

Belt - Refers to a lineman's climbing belt.

Bias Current - The current used as a bias quantity in a biased relay.

Biased Relay - A relay in which the characteristics are modified by the introduction of some quantity, and which is usually in opposition to the actuating quantity.

Bikeway (Lighting) - Any road, street, path or way that is specifically designated as being open to bicycle travel, regardless of whether such facilities are designed for the exclusive use of bicycles.

BIL - 1) See Basic Insulation Level. 2) See Basic Impulse Level.

Blackout - The complete interruption of load to an electric utility customer or group of customers.

Blowing - The act of installing fiber optic cable into a duct using air pressure.

Bonding - The joining of metallic parts to form an electrically conductive path that will ensure electrical continuity and the capacity to conduct any current to be present in a safe manner.

Boomer - A lineman that moves from job to job.

Boost Charge - A charge applied to a battery which is already near a state of full charge, usually of short duration.

Booster Transformer - A current transformer whose primary winding is in series with the catenary and secondary winding in the return conductor of a classically-fed A.C. overhead electrified railway.

Breakdown Voltage - The voltage at which a dielectric material fails.

Breaker - See "Circuit breaker".

Brownout - Refers to a reduction of voltage on the system. This dims the lights as a means of conserving energy.

Buck - The act of lowering the voltage.

Bucket - A basket or platform that supports one or more linemen attached to a boom of a truck.

Bucket Truck - An aerial lift truck used to lift men high enough to work on overhead lines.

Building Wire - Conductors and cables used in commercial building construction.

Bulb - The outer enclosure of a light source; usually glass or quartz.

Bull Line - Heavy line used to pull wire or cable into a conduit or into an overhead configuration.

Bull Wheel - A reel device used to hold tension during the wire installation process.

Bunched Stranding - A term applied to a number of wires twisted together in one direction in one operation without regard to their geometric arrangement.

Bundle - Multiple cables used to form one phase of an overhead circuit.

Burden - Load imposed by an electronic or electrical device on the measured input circuit, expressed in volt-amps.

Bus - A conductor, which may be a solid bar or pipe, normally made of aluminum or copper, used to connect one or more circuits to a common interface. An example would be the bus used to connect a substation transformer to the outgoing circuits.

Bushing - An insulator having a conductor through it, used to connect equipment to a power source.

Bushing Well - See Universal Bushing Well.

C - Centigrade or Celsius

C-Rate - Battery discharge current in amperes; numerically equal to rated capacity of a cell in ampere-hours.

C2H4 - Ethylene.

C2H6 - Ethane.

Cable - A term generally applied to the larger sizes of bare or weatherproofed (covered) and insulated conductors. It is also applied to describe a number of insulated conductors twisted or grouped together.

Cable Cleaner - A chemical compound used to clean dirt, residual insulation & semi con and other foreign material from an insulated cable during the termination process.

Cable Pulling Lubricant - A chemical compound used to reduce pulling tension by lubricating a cable when pulled into a duct or conduit.

Cable Sheath - The outermost covering of a cable providing overall protection

Cable Tray - A rigid structural system used to support cables and raceways. Types of cable trays include ladder, ventilated trough, ventilated channel, and solid bottom

CAIDI - A distribution circuit reliability average interruption duration index. It represents the average time required to restore service to the average customer per sustained interruptions.

CAIFI - The customer average interruption frequency index. It is designed to show trends in customers interrupted and helps to show the number of customers affected out of the whole customer base.

Calibration - Adjustment of a device so the output is within a specified range for particular values of the input.

Calorie - A calorie is the energy required to raise one gram of water one degree Celsius at one atmosphere. The onset of second-degree burns may occur at 1.2 calories per centimeter squared per second.

Can - Slang for an overhead transformer.

Candela (cd) - The standard unit for luminous intensity. One candela is equal to one lumen per steradian.

Candlepower - Luminous intensity expressed in candelas.

Candlepower Distribution Curve - A curve, generally polar, representing the variation of luminous intensity of a lamp or luminaire in a plane through the light center.

Capacitor - An electrical device having Capacitance.

Capacitor bank - An assembly of capacitors and switching equipment, controls, etc., required for a complete operating installation.

Capacitor Voltage Transformer - A voltage transformer that uses capacitors to obtain a voltage divider effect. It is utilized at EHV voltages instead of an electromagnetic VT for cost and size purposes.

Capacity (Battery) - The quantity of electricity delivered by a battery under specific conditions, usually expressed in ampere-hours.

Cathode - 1) The negative electrode, that emits electrons or gives off negative ions and toward which positive ions move or collect in a voltaic cell or other such device. 2) The negative pole of a battery.

CB - Circuit Breaker

Cell (Battery) - An electrochemical device composed of positive and negative plates, separator, and electrolyte which is capable of storing electrical energy.

Cell (Photovoltaic) - See "Photovoltaic Cell".

Cell Voltage (Battery) - See "Nominal Voltage (Battery)".

Cell-Reversal (Battery) - Reversing of polarity within a cell of a multi-cell battery due to over discharge.

CH2H2 - Acetylene

CH4 - Methane.

Characteristic Angle - The angle between the vectors representing two of the energizing quantities applied to a relay used for the declaration of the performance.

Characteristic Curve - A plot or curve displaying the operating values of the characteristic quantities corresponding to various values or combinations of the energizing quantities.

Characteristic Impedance Ratio (C.I.R.) - The maximum value of the system impedance ratio for which the relay performance remains within the prescribed limits of accuracy.

Charge (Battery) - The conversion of electrical energy from an external source, into chemical energy within a cell or battery.

Charge Controller - An electronic device which regulates the voltage applied to a battery or battery bank.

Charge Rate (Battery) - The rate at which current is applied to a secondary cell or battery to restore its capacity.

Charge-Retention (Battery) - The tendency of a charges cell or battery to resist self-discharge.

Check Protection System - An auxiliary protection system intended to prevent tripping due to inadvertent operation of the main protection system.

Cherry Picker - An aerial lift truck. Also see Bucket Truck.

Chlorinated Polyethylene - Chlorinated Polyethylene. CPE, a thermoplastic compound, is used to jacket certain types of power cable.

Choker - A Sling.

Circuit - A conductive path over which an electric charge may flow.

Circuit Breaker - A device that can be used to manually open or close a circuit, and to automatically open a circuit at a predetermined level of over current without damage to itself.

Circuit Insulation Voltage - The highest circuit voltage to earth on which a circuit of a transducer may be used and which determines its voltage test.

Circuit Switchers - Circuit-Switchers are multipurpose switching and protection devices.

Circuit Voltage - The greatest root-mean-square (effective) difference of potential between any two conductors of the circuit.

Circular-Mil (cmil) - The area of a circle with a diameter of one mil (1/1000 inch), used to describe the cross-sectional area of a conductor. One cmil equals approximately 0.0000008 square inches.

Class Index - A number which designates an accuracy class.

Clearing Time - The total time needed for a protective device such as a fuse or circuit breaker to clear a fault.

CLF - Refer to "Current Limiting Fuse".

Climbers - Hooks for climbing poles that are attached to a lineman's boots.

Closing Impulse Time - The time during which a closing impulse is given to the circuit breaker.

Closing Time - Referring to a circuit breaker it is the necessary time for it to close, beginning with the time of energizing of the closing circuit until contact is made in the CB.

CO - Carbon Monoxide.

Coefficient of Utilization (CU) - The percentage of light generated within a luninaire which ultimately strikes the work surface. It is usually expressed as a decimal percentage.

Coffin Hoist - A chain hoist of any type.

Coil Loss - Power loss in a transformer due to the flow of current. These losses are present only when the transformer is serving a load.

Cold - Refers to non-energized equipment, lines or circuits.

Combination Unilay - A stranding configuration that uses two strand sizes to achieve a 3% reduction in the conductor diameter without compression

Come-a-long - A wire grip for holding a conductor or strand under tension.

Compact Stranding - A stranding configuration with concentric strands in which each layer is passed through a compacting die to reduce the conductor diameter by approximately 10%

Compliance Voltage - The specified maximum voltage that a transducer (or other device) current output must be able to supply while maintaining a specified accuracy.

Compound - An insulating or jacketing material made by mixing two or more ingredients

Compressed - A stranding configuration with concentric strands in which either all layers or the outer layer only is passed through a die to reduce the conductor diameter by 3%

Compression Splice - A compression connector used to join two conductors. There are different designs used for overhead and underground conductors. For overhead conductors, there are different designs for limited and full tension applications.

Concentrator (Photovoltaic) - See "Photovoltaic Concentrator".

Concentric Stranding - A stranding configuration in which individual wires are stranded concentrically with no reduction in overall diameter.

Conduct - The ability of two conductors separated by a dielectric to store electricity when a potential difference exists between the conductors.

Conductivity - The capability of a conductor to carry electricity, usually expressed as a percent of the conductivity of a same sized conductor of soft copper

Conductor - 1) A wire or combination of wires suitable for carrying an electrical current. Conductors may be insulated or bare. 2) Any material that allows electrons to flow through it.

Conductor Loss - See "Coil Loss".

Conductor Shield - A semiconducting material, normally cross-linked polyethylene, applied over the conductor to provide a smooth and compatible interface between the conductor and insulation.

Conduit - A channel for holding and protecting conductors and cables, made of metal or an insulating material, usually circular in cross section like a pipe. Also referred to as Duct.

Conduit Fill - Volumetric measurement of the duct space occupied by the cables inside, expressed as a percent.

Conjunctive Test - A parametric or specific test of a protection system on all components and auxiliary equipment that are connected.

Connector - A conductive coupling device used to connect conductors together.

Constant Current Charge - Charging technique where the output current of the charge source is held constant.

Constant Potential Charge - Charging technique where the output voltage of the charge source is held constant and the current is limited only by the resistance of the battery.

Continuity Test - A test performed on a conductor to determine if it is unbroken throughout its length

Continuous - See Continuous Rating.

Continuous Load - An electrical load in which the maximum current is expected to continue for three hours or more

Continuous Rating - The constant voltage or current that a device is capable of sustaining. This is a design parameter of the device.

Conversion Coefficient - The relationship of the value of the measured to the corresponding value of the output.

Coordination - Relating to the protection of the power system, the process of coordinating the fuse, breakers and reclosers of a system so to allow the downstream devices to operate first.

Copolymer - Chains of unlike molecules that are chemically bonded together

Core Balance Current Transformer - A ring-type current transformer in which all primary conductors are passed through the aperture making any secondary current proportional to any imbalance in current.

Core Loss - Power loss in a transformer due to excitation of the magnetic circuit (core). No load losses are present at all times when the transformer has voltage applied.

Corona - See Corona Discharge.

Corona Discharge - An electrical discharge at the surface of a conductor accompanied by the ionization of the surrounding atmosphere. It can be accompanied by light and audible noise.

Coulomb - A unit of electric charge in SI units (International System of Units). A Coulomb is the quantity of electric charge that passes any cross-section of a conductor in one second when the current is maintained constant at one ampere.

Counter EMF - Voltage or cell or battery opposing the voltage of the charging source.

Counting Relay - A relay that counts the number of times it is energized and actuates an output after a desired count has been reached.

Cover - Top surface section of the handhole for closing the top access opening of the box section.

CPE - Chlorinated Polyethylene. CPE is a thermoplastic compound that is used to jacket certain types of power cable.

Creepage Distance - The shortest distance between two conductors as measured along the device that separates them. Creepage Distance is normally a design parameter of insulators or insulating bushings.

Crest - See Crest Value.

Crest Value - The maximum value of a wave form. This is normally associated with electrical fault magnitude or transients.

Cross-Linked Polyethylene (XLPE) - A Common thermoset insulation material for building wire and cable. It undergoes a cross linking chemical reaction during a curing process that causes the compound molecules to bond, forming heavier molecules.

CSP - Completely Self-Protected transformer.

CST - Customer Subsurface Transformer.

CT - See "Current Transformer".

CTC - See Competition Transition Charge.

Cu - The chemical symbol for copper.

CU (Lighting) - Coefficient of Utilization

Current - The movement of electrons in a conductor measured in Amperes.

Current Limiting Fuse - A fuse designed to reduce damaging extremely high current.

Current Transducer - A transducer used for the measurement of A.C. current.

Current Transformer - A transformer used to measure the amount of current flowing in a circuit by sending a lower representative current to a measuring device such as a meter.

Current Transformer Ratio - 1) the ratio of primary amps divided by secondary amps. 2) The current ratio provided by the windings of the CT.

Cut Off Voltage - Battery Voltage reached at the termination of a discharge. Also Known as the End Point Voltage (EPV).

Cutoff Angle (Lighting) - With regard to an outdoor lighting luminaire, the angle between the vertical axis and the first line of sight at which the bare light source is not visible.

Cutoff, Full (Lighting) - A luminary light distribution with zero candela at an angle of 90 degrees or above and not more than 10% of emitted light above 80 degrees.

Cutoff, Non (Lighting) - A luminary light distribution where there is no Candela restriction at any angle.

Cutoff, Semi (Lighting) - A luminary light distribution with 5% candela at an angle of 90 degrees or above and not more than 20% of emitted light above 80 degrees.

Cutout - See "Fused Cutout".

Cycle - In Alternating current, the change of the poles from negative to positive and back.

Cycle (Battery) - A sequence of discharge followed by a charge, or a charge followed by a discharge, of a battery under specific conditions.

DA Bolt - A Double Arming Bolt.

dB - See "decibel".

DC - See "Direct Current".

De-energized - Free from any electrical connection to a source of potential difference and from electrical charge. A circuit is not truly de-energized until protective grounds have been installed.

De-ionization Time - The time required for dispersion of ionized air after a fault is cleared so that the arc will not re-strike on re-energization.

Dead Front - Generally refers to equipment that is connected without exposed conductor. Dead front equipment is normally connected with elbows.

Dead Time - The time between the fault arc being extinguished and the circuit breaker contacts re-mating.

decibel - A logarithmic mathematical ratio that indicates a devices electric or acoustic signal to that of another

Deep Discharge (Battery) - Withdrawal of 50% or more of the rated capacity of a cell or battery.

Delta - A three phase connection where each phase is connected in series with the next, separated by a phase rotation of 120 degrees.

Delta-Wye - Refers to a transformer that is connected Delta on the primary side and Wye on the secondary.

Dependent Time Measuring Relay - A measuring relay for which times depend, in a specified manner, on the value of the characteristic quantity.

Depth of Discharge - The portion of the nominal capacity from a cell or battery taken out during each discharge cycle, expressed in percent. Shallow Depth of Discharge is considered as 10% or less. Deep Discharge is considered 50% or more.

Derating - Calculations that reduce standard tabulated ratings based, generally based on ambient temperature or proximity to a heat source.

Design Load - The actual, expected load or loads that a device or structure will support in service.

Design Test - Tests done to equipment to verify the design meets certain established characteristics or standards.

Device Control Point - Local keypad on device level to control the switchgear often combined with local or remote switch.

DFT - Discrete Fourier Transform

Dielectric - 1) Any electrical insulating medium between two conductors. 2) The medium used to provide electrical isolation or separation.

Dielectric Constant - A number that describes the dielectric strength of a material relative to a vacuum, which has a dielectric constant of one.

Dielectric Grease - A silicone based chemical compound used to seal and lubricate connections between medium voltage connectors such as cable termination elbows.

Dielectric Strength - The maximum voltage an insulation system can withstand before breakdown, expressed in volts per mil of insulation thickness.

Dielectric Test - A test that is used to verify an insulation system. A voltage is applied of a specific magnitude for a specific period of time.

Dielectric Withstand - The ability of insulating materials and spacing's to withstand specified overvoltage's for a specified time (one minute unless otherwise stated) without flashover or puncture.

Dielectric Withstand Voltage Test - The test to determine Dielectric Withstand.

Dip Tolerance (Lighting) - With regard to outdoor lighting, the percentage of instantaneous voltage variation from normal that is required to extinguish a light source.

Direct Current - Electric current in which electrons flow in one direction only. Opposite of alternating current.

Direct-on-Line - A method of motor starting, which full line voltage is applied to a stationary motor.

Directional Relay - A protection relay in which the tripping decision is dependent in part upon the direction in which the measured quantity is flowing.

Discharge (Battery) - The conversion of the chemical energy of a cell or battery into electrical energy and withdrawal of the electrical energy into a load.

Discharge Current - The surge current that is dissipated through a surge arrester.

Discharge Rate (Battery) - The rate of current flow from a cell or battery.

Disconnect Switch - A simple switch that is used to disconnect an electrical circuit. It may or may not have the ability open while the circuit is loaded.

Discrimination - The ability of a power protection system to differentiate between the conditions it was intended to operate and those it was not intended for.

Distribution System - A term used to describe that part of an electric power system that distributes the electricity to consumers from a bulk power location such as a substation. It includes all lines and equipment beyond the substation fence.

Distribution Transformer - A transformer that reduces voltage from the supply lines to a lower voltage needed for direct connection to operate consumer devices.

Distribution Voltage - A nominal operating voltage of up tp 38kV.

Door - The fuse tube of a fused cutout.

Double Arming Bolt - A special long bolt used to assemble two cross arms, one on each side of the pole.

Draw-Lead - A cable or solid conductor that has one end connected to the transformer or a reactor winding and the other end drawn through the bushing hollow tube and connected to the top terminal of the bushing.

Drawing - The process of reducing a cylindrical rod or wire to a desired diameter by pulling the wire through dies.

Drop-Out - A relay drops out when it moves from the energized position to the un-energized position.

Dry Charge (Battery) - The process by which the electrodes are formed and assembled in a charged state. The cell or battery is activated when electrolyte is added.

Dry-Type Transformers - Transformers that use only dry-type materials for insulation. These have no oils or cooling fluids and rely on the circulation of air about the coils to provide necessary cooling.

Dual Voltage Switch - A switch used to select primary windings of a transformer.

Dual Voltage Transformer - A transformer that has switched windings allowing its use on two different primary voltages.

Duct - A channel for holding and protecting conductors and cables, made of metal or an insulating material, usually circular in cross section like a pipe. Also referred to as Conduit.

Duct Bank - Two or more ducts or conduits used as part of a system.

Earth Fault Protection System - A protection system which is designed to excite during faults to earth.

Earthing Transformer - A three-phase transformer intended essentially to provide a neutral point to a power system for the purpose of grounding.

Eddy Current - The current that is generated in a transformer core due to the induced voltage in each lamination. It is proportional to the square of the lamination thickness and to the square of the frequency.

Effective Internal Resistance (Battery) - The apparent opposition to current within a battery that manifests itself as a drop in battery voltage proportional to discharge current. Its value is dependent on battery design, state-of-charge, temperature and age.

Effective Power (Watts) - See "Watt"

Effective Range - The range of values of the characteristic quantity or quantities. For example the energizing quantities to which the relay will respond and satisfy the requirements to precision.

Effective Setting - The setting of a protection system including the effects of current transformers, this effective setting can be expressed in terms of primary current or secondary current from the current transformers.

Effectively Grounded - Intentionally connected conductors or electric equipment to earth, where the connection and conductors are of sufficiently low impedance to allow the conducting of an intended current.

Efficiency (Lighting) - A ratio of light emitted from a luminaire to the light produced by the bare lamp.

EHV - See "Extra High Voltage".

Elbow - A device used to connect a medium voltage cable (4-35KV nominal) to an electrical component such as a switch or transformer.

Electrical Hazard - A dangerous condition such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast.

Electrical Relay - A device designed to produce sudden predetermined changes in one or more electrical circuits after the appearance of certain conditions in the controlling circuit.

Electrical Safety - Recognizing hazards associated with the use of electrical energy and taking precautions so that hazards do not cause injury or death.

Electrically Safe Work Condition - A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.

Electricity - The flow of electrons through a conducting medium.

Electrolyte (Battery) - In a lead-acid battery, the electrolyte is sulfuric acid diluted with water. It is a conductor and also a supplier of hydrogen and sulfate ions for the reaction.

Electromechanical Relay - An electrical relay in which the designed response is excited by a relative mechanical movement of elements under the action of a current in the input circuit.

Electromotive Force - Potential causing electricity to flow in a closed circuit.

Elongation - The amount (% length) that a conductor or other material can stretch before breaking when a pulling force is applied.

Embedded Generation - Generation that is connected to a distribution system possibly at LV instead of HV.

EMS - See Energy Management System

End Point Voltage - Battery Voltage reached at the termination of a discharge. Also Known as the Cut Off Voltage.

End-of-Discharge Voltage - The voltage of a battery at the termination of a discharge but before the discharge is stopped.

End-Point Voltage - The Cell or Battery voltage at which point the rated discharge capacity has been delivered at a specific Rate-of-Discharge.

Energy - That which does work or is capable of doing work. Electricity is energy that is measured in kilowatt hours.

Energy Management System - A system in which a dispatcher can monitor and control the flow of electric power by opening and closing switches to route electricity or to isolate a part of the system for maintenance.

Entrainment (Battery) - The process whereby gasses generated in the cell carry electrolyte through the vent cap.

EPDM - Ethylene Propylene Dione Monimer. This is a synthetic rubber compound used as insulation in making electrical components.

EPR - Ethylene Propylene Rubber, a synthetic rubber compound that is used as cable insulation.

Eutectic - An alloy used to form the melting point of a fuse. It is frequently silver or tin based.

Exciting Current - The magnetizing current of a device such as a transformer. Also known a field current.

Extra High Voltage - An electrical system or cable designed to operate at 345kv (nominal) or higher.

Extrusion - The application of a semi-solid rubber or plastic material such as PVC onto a conductor

F - Fahrenheit

FA - Forced-Air, a cooling classification for transformers now classified as ONAF. Oil type, Forced circulation through cooling (i.e. cooling pumps) and natural convection flow in windings.

Farad - The capacitance value of a capacitor of which there appears a potential difference of one volt when it is charged by a quantity of electricity equal to one coulomb.

FAT - Factory acceptance test. Validation procedures witnessed by the customer at the factory.

Fault Close Rating - The ability, in amps, of a switching device to "close" into a fault of specific magnitude, without excessive arcing.

Fault Current - The current that flows as a result of a short-circuit condition.

Fault Indicator - A device installed on a conductor to determine if current exceeded the indicator's current rating. Fault indicators sense using use the magnetic field induced by load current.

Feeder - A three phase distribution line circuit used as a source to other three phase and single phase circuits.

Ferro resonance - In transformers, an over-voltage condition that can occur when the core is excited through capacitance in series with the inductor.

Field Current - The magnetizing current of a device such as a transformer. Also known as exciting current.

Fill - In conduit or cable tray installations, the portion of the total cross-sectional area of the tray or conduit that can be occupied by conductors or cables

Filler - A material used in multiconductor cable to occupy large interstices formed by the cable assembly. Also, a material added to an insulation compound to add volume and increase impact resistance

Fixed Capacitor Bank - A capacitor bank installed with no automatic switching device. The bank is manually switched on and off. Also see "Capacitor Bank".

Flame Resistance - The ability of insulation or jacketing material to resist the support and conveyance of fire.

Flash Hazard - A dangerous condition associated with the release of energy caused by an electric arc.

Flash Protection Boundary - An approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur.

Flash Suit - A complete FR clothing and equipment system that covers the entire body, except for the hands and feet. This includes pants, jacket, and bee-keeper-type hood fitted with a face shield.

Flashover - An unintended electrical discharge to ground or another phase. Flashovers can occur between two conductors, across insulators to ground or equipment bushings to ground.

Float Charge - A method of maintaining a cell or battery in a charged condition by continuous, long-term, constant voltage charging at a level sufficient to balance self-discharge.

Float Charge (Battery)MTI - A continuous low rate charge that compensates for the self discharge rate of a battery. Also known as Trickle Charge.

Flooded Cell - A cell design that incorporates an excess amount of electrolyte.

Fluorescent Lamp - A low pressure Mercury, electric discharge lamp in which a fluorescing coating (Phosphor) transforms some of the ultraviolet energy generated by the discharge into light.

Foot-candle (fc) - Standard unit of measure for illumination on a surface. The Average foot-candle level on a square surface is equal to the lumens striking the surface, divided by the area of the surface.

FPI - Fault Passage Indicator

Frequency - In ac systems, the rate at which the current changes direction, expressed in hertz (cycles per second); A measure of the number of complete cycles of a wave-form per unit of time.

Frequency Transducer - A transducer used for the measurement of the frequency of an A.C. electrical quantity.

Full Scale Output - The specified maximum output value for which the stated accuracy condition applies

Fuse - A device installed in the conductive path with a predetermined melting point coordinated to load current. Fuses are used to protect equipment from over current conditions and damage.

Fuse Arcing Time - The amount of time required to extinguish the arc and clear the circuit.

Fuse Link - A replaceable fuse element used in a Fused Cutout.

Fuse Melt Time - The time needed for a fuse element to melt, thereby initiating operation of the fuse. Also known as Melt Time.

Fused Cutout - A device, normally installed overhead, that is used to fuse a line or electrical apparatus.

Gassing (Battery) - The evolution of gas from one or more of the electrodes in a cell. Gassing commonly results from local action (self discharge) or from the electrolysis of water in the electrolyte during charging.

Gel - A chemical compound used to seal and mechanically cushion fiber optic filament in a cable. The cleaners used to remove are made by American Polywater.

Gel Cleaner - A chemical based cleaner used to remove the gel in a fiber optic cable. Gel cleaner is made by American Polywater Corp.

Generator Step-Up (GSU) - Generator step up is done by transformers directly connected to the generator output terminals. This is usually done via busbars in large generating stations. They normally have a high voltage in secondary and high current in primary.

GF - Ground Fault

Gin - A device used for temporary lifting.

GIS - Gas Insulated Switchgear (usually SF6).

Glare - A sensation of uncomfortable brightness, usually coming from a luminaire at angles between horizontal and 45 degrees below horizontal.

Gnd - Ground

Grease - 1) Slang for Cable Pulling Lubricant, a chemical compound used to reduce pulling tension by lubricating a cable when pulled into a duct or conduit. 2) Slang for Dielectric Grease, a silicone based chemical compound used to seal and lubricate connections

Grip All Stick - See Shotgun Stick.

Ground - 1. An electrical term meaning to connect to the earth. 2. A conducting connection, whether intentional or accidental by which an electric circuit, or equipment, is connected to the earth or some conducting body that serves in place of the earth.

Ground Fault - An undesired current path between ground and an electrical potential.

Grunt - A lineman's helper.

Gut - Slang for "Line Hose".

Guy Strain Insulator - An insulator, normally porcelain, used to electrically isolate one part of a down guy from another. Guy Strain Insulators are made by Porcelain Products.

H2 - Hydrogen.

H20-44 - See "H20"

Hard Drawn - Wire that has been drawn to its specific size and not annealed.

Hard Line - A Steel Pulling line. Also see Bull Line.

Harmonic - A sinusoidal component of the voltage that is a multiple of the fundamental wave frequency.

Harmonic Distortion - The presence of harmonics that change an AC waveform from sinusoidal to complex. They can cause unacceptable disturbance to electronic equipment.

Heat Run Test - A test that is used to determine the increase in operating temperature at a given load.

Helical - Wrapped in a spiral fashion. Refers to the way the strands of a conductor are laid.

Henry - The meter-kilogram-second unit of inductance, equal to the inductance of a circuit in which an electromotive force of one volt is produced by a current in the circuit which varies at the rate of one ampere per second.

HID - High Intensity Discharge

High Intensity Discharge (HID) Lamp - An electric discharge lamp in which the light producing arc is stabilized. Examples of HID lamps include High Pressure Sodium, Metal Halide and Mercury Vapor.

High Pot - A test done to confirm the reliability of an insulation system where a high voltage is applied.

High Pressure Sodium (HPS) Lamp - A High Intensity Discharge light source in which the arc tube's primary internal element is Sodium Vapor.

High Voltage - An electrical system or cable designed to operate between 46kv and 230kv.

High Voltage System - An electric power system having a maximum roo-mean-square ac voltage above 72.5 kilovolts (kv).

High-speed reclosing - A re-closing scheme where re-closure is carried out without any time delay other than required for deionization.

Horsepower - A unit of work. When used to show power usage, one horsepower is equivalent to 746 watts.

Hose - Slang for "Line Hose".

Hot - Refers to an energized conductor or apparatus.

Hot Arm - A device that is used to temporarily extend a conductor beyond the cross arm it was on.

Hotstick - An insulated stick, usually made of fiberglass, that is used to work energized overhead conductors and operate electrical equipment that is overhead, underground and pad mounted.

HPS - High Pressure Sodium

HRC - High Rupturing Capacity (applicable to fuses).

HSR - High Speed Re-closing.

HV - High Voltage.

Hybrid Photovoltaic System - A photovoltaic system that includes other sources of electric generation such as wind or fossil fuel.

Hydrometer - A float type instrument used to determine the state-of-charge of a battery by measuring the specific gravity of the battery electrolyte (i.e., the amount of sulfuric acid in the electrolyte).

I - Current

I.D.M.T. - Inverse Definite Minimum Time.

I/O - Input/Output

I2t - Current Squared times time. This is an electrical quantity that is used to determine energy to a protective device, such as a circuit breaker or fuse.

IED - Intelligent Electronic Device. Equipment containing a microprocessor and software used to implement one or more functions in relation to an item of electrical equipment. IED is a generic term used to describe any microprocessor-based equipment, apart from

IGBT - Insulated Gate Bipolar Transistor

ILL (Lighting) - Initial Lamp Lumens

Impedance - 1) The total opposing force to the flow of current in an ac circuit. 2) The combination of resistance and reactance affecting the flow of an alternating current generally expressed in ohms.

Impulse - A current surge

Impulse Test - Tests to confirm that the insulation level is sufficient to withstand overvoltages, such as those caused by lightning strikes and switching.

Incandescent Lamp - A lamp in which light is produced by a filament heated to incandescence by an electric current.

Incident Energy - The amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. Often measured in calories per centimeter squared. (cal/cm²)

Independent Time Measuring Relay - A measuring relay, the specified time for which can be considered as being independent, within specific limits, of the value of the characteristic quantity.

Induced Current - Current in a conductor resulting from a nearby electromagnetic field.

Induced Voltage - A voltage produced in a circuit from a nearby electric field.

Inductance - 1) The property of a circuit in which a change in current induces an electro motive force. 2) Magnetic component of impedance.

Initial Lamp Lumens (Lighting) - (AMF x PS x RW)/(CU x LLF)

Input Quantity - The quantity, or one of the quantities, which constitute the signals received by the transducer form the measured system.

Inrush Current - The initial surge of current experienced before the load resistance of impedance increases to its normal operating value.

Instantaneous Relay - A relay that operates and resets with no intentional time delay.

Instrument Transformer - A transformer that is only designed to reduce current or voltage from a primary value to a lower value secondary that can be applied to a meter or instrument, at a proportional safer level.

Insulated Gate Bipolar Transistor - A special design of transistor that is suitable for handling high voltages and currents. Often used in static power control equipment such as inverters, or controlled rectifiers, due to the flexibility of control of the output.

Insulation - Sunlight, direct of diffuse, from incident solar radiation. It is equal to approximately 1000 watts per square meter at high noon. Not to be confused with insulation.

Intensity (Lighting) - The brightness of light in a given direction. Luminous intensity may be expressed in Candelas (cd) or in Lumens.

Intermediate Class Arrester - Surge arresters with a high energy handling capability. These are generally voltage classed at 3-120kV.

Internal Impedance (Battery) - The opposition to the flow of alternating current at a particular frequency in a cell or battery at a specific state-of-charge and temperature.

Internal Resistance (Battery) - The opposition or resistance to the flow of Direct Electric Current within a cell or battery; The sum of the ionic and electronic resistance of the cell components.

International System of Units (SI) - A universal system of units in which the following six units of measure are considered basic: meter, kilogram, second, ampere, Kelvin degree and candela.

Interrupter Switch - A switch equipped with an interrupter for making or breaking connections under load

Interrupting Rating - The rating of a device to interrupt the flow of power or current, generally applied to a circuit breaker or a switch.

Interruption - The loss of electric service to one or more customers or other facilities. It is the result of one or more component outages.

Interruption Duration - The period from the initiation of an interruption to a customer or other facility to the time the service is restored.

Interruption, Momentary - An interruption of a duration limited to the period required to restore service by automatic or supervisory controlled switching operations or by manual switching at locations where operators are immediately available.

Interruption, Sustained - Any interruption not classified as momentary. Any interruption longer that five (5) minutes.

Interstices - The space between two or more objects, such as the individual strands in a stranded conductor or conductors in a cable.

Intrinsic Error - An error determined when the transducer is under reference conditions.

Inverse Time Delay Relay - A dependent time delay relay having an operating time which is an inverse function of the electrical characteristic quantity.

Inverter - A device that converts DC electricity into single or multiphase AC electricity.

Ion - Part of a molecule or group of atoms, positively or negatively charged, that transports electricity.

Isolation - 1) A non-conductive material used to seperate conducting materials in a circuit. 2) The non-conductive material used in the manufacture of insulated cables.

Isolation Link - A metal link used in series with a fusing device that melts and prevents refusing/re-enerization of a transformer.

Jacket - A covering over insulated conductors for the purpose of electrical, chemical, and physical protection.

Joule - 1) Work done by the force of one neutron when its point of application moves through the distance of one meter in the direction of the force. 2) One watt-second.

Jumper - An electrical connection between two points.

Junction, 200 Amp - A "200 Amp Junction" is a molded synthetic and composite device used to connect two or more 200 Amp rated cables operating at Meduim Voltage (4-35KV nominal). Connections to the cables are made via "200 Amp Elbows".

Junction, 600 Amp - A "600 Amp Junction" is a molded synthetic and composite device used to connect two or more 600 or 900 Amp rated cables operating at Meduim Voltage (4-35KV nominal). Connections to the cables are made via "T-Bodies".

Kilo - A prefix indicating one (1) thousand.

Kilowatt - 1000 watts of real power. Expressed at kW.

Kilowatt Hour - The use of one thousand watts for one hour.

Knee-Point e.m.f. - Result of when a sinusoidal e.m.f. is applied to the secondary terminals of a current transformer is increased by 10% causes the exciting current to increase by 50%.

kVA - 1) Apparent Power expressed in Thousand Volt-Amps. 2) Kilovolt Ampere rating designates the output which a transformer can deliver at rated voltage and frequency without exceeding a specified temperature rise.

KVAR - KVAR is the measure of additional reactive current flow which occurs when the voltage and current flow are not perfectly in phase.

kW - See "Kilowatt".

kWh - See "Kilowatt Hour"

L - A symbol used to express inductance. The unit of measure is a "Henry".

Lag - The condition where the current is delayed in time with respect to the voltage in an ac circuit (for example, an inductive load).

Lamp - A complete light source unit, usually consisting of a light generating element (arc tube or filament), support hardware, enclosing envelope and base.

Lateral Circuit - A tap-off line to take primary distribution from the main power line to a nearby load center.

Lateral Light Distribution - Lateral light distributions are classified by IES distribution Types I, II, III, IV and V. In general, the larger the number, the more is projected across the roadway.

Lay Direction - 1) The direction in which the wires of a conductor are twisted. 2) The twist of conductors in a cable.

Lay Length - The distance required to complete one revolution of helically laid strands of wires.

LDC - A Line Drop Compensator is utilized to provide constant voltage at the load.

LDD - Luminaire Dirt Depreciation Factor

Lead - The condition where the current precedes in time with respect to the voltage in an ac circuit (for example, a capacitive load).

Lead Acid (Battery) - Term used in conjunction with a cell or battery that utilizes lead and lead peroxide as the active plate materials in a diluted electrolyte solution of sulfuric acid and water. The nominal cell voltage is 2.1 volts.

Lead Acid Battery - The assembly of one or more cells with an electrolyte based on dilute sulfuric acid and water, a positive electrode of lead dioxide and negative electrodes of lead. Lead Acid batteries all use the same basic chemistry.

Lead Dioxide (Battery) - The higher oxide of lead present in charged positive plates. It is frequently referred to as lead peroxide.

Lead Sulfate - A lead salt formed by the action of sulfuric acid on lead oxide during paste mixing and formation. It is also formed electromechanically when a battery is discharged.

LED - Light Emitting Diode

Light - Energy that is capable of exciting the retina and producing a visual sensation.

Light Loss Factor (LLF) - A factor used in calculating luminance after a given period of time and under given conditions. It takes into account temperature and voltage variations, dirt accumulation on luminaire and lit surfaces, lamp depreciation, maintenance procedures and atmos

Light Traffic - A grade level Box or Cover rating. See "Incidental Light Traffic".

Lighting Arrester - A device that protects power lines and equipment against high voltage lighting surges and switching surges. Connected from line to ground potential, the device has a very high resistance to current flow at normal voltages.

Lighting Maintenance Factor (MF) - The result of time-dependent depreciation effects must be considered in the initial design.

Lightning - Lightning is a powerful natural electrostatic discharge produced during a thunderstorm. Lightning's abrupt electric discharge is accompanied by the emission of light.

Lightning & Switching Impulses - A distinction is made between Lightning and Switching impulses on the basis of duration of the wave front. Impulses with wave-front durations of up to a few tens of microseconds are in general considered to be lightning impulses.

Limit Switch - A protective device used to open or close electrical circuits when certain limits, such as temperature or pressure, are reached.

Limited Approach Boundary - An approach limit at a distance from an exposed live part within which a shock hazard exists.

Limiting Value of the output current - The upper limit of the output current which cannot, by design be exceeded under any conditions.

Line - Refers to the conductor in an overhead or underground distribution or transmission line.

Line Traps - High voltage lines can be used to transmit R. F. carrier signals for the purposes of voice communication, remote signaling and control. The frequency range from 30 to 500 kHz has proven to be advantageous for high frequency carrier transmission.

Liner - Cloth gloves used to line the inside of a rubber insulating glove.

LLF (Lighting) - Light Loss Factor

Load - 1) The amount of electrical power required by connected electrical equipment. 2) The total impedance of all the items in the output circuit.

Load break - Refers to a group of rubber insulating products used to electrically connect apparatus with which load can be separated manually.

Load Loss - See "Coil Loss".

Local Control Mode - When set for a given control point it means that the commands can be issued from this point.

Long Distribution (Lighting) - A luminary is classified as having a long light distribution when its max candlepower point falls between 3.75MH - 6.0MH TRL. The maximum luminaire spacing-to-mounting height ratio is generally 12.0 or less.

Long-Term Stability - The stability over a period of one year.

LPW - Lumens Per Watt

Lube - Slang for "Cable Pulling Lubricant".

Lumen - Standard unit of measure for light flux or light energy. Lamp light output is measured in Lumens.

Lumens Per Watt (LPW) - The ratio of light energy output (Lumens) to electrical energy input (Watts).

Luminaire - A complete lighting unit consisting of a light source with a means of distribution (reflector and/or refractor), lamp positioning (socket), lamp protection (housing) and a provision for power connection.

Luminaire Dirt Depreciation (LDD) - The accumulation of dirt on luminaires results in a loss of light output on the road. This loss is known as the LDD factor and is determined by estimating the dirt category from the graph below.

Luminance - The density of the luminous flux incident on a surface. It is the quotient of the luminous flux multiplied by the area of the surface when the later is uniformly illuminated.

Lux - The SI unit of luminance. One lux is one lumen per square meter.

LV - Low Voltage

Main Protection - The protection system which is normally expected to operate in response to a fault in the protected zone.

Maximum Permissible Values of the input current and voltage - Values of current and voltage assigned by the manufacturer which the transducer will withstand indefinitely without damage.

MCC - Motor Control Center

MCCB - Molded Case Circuit Breaker

Measured - A quantity subjected to measurement.

Measuring Element - A unit or module of a transducer which converts the measurand, or part of the measurand into a corresponding signal.

Measuring Range - The part of the span where the performance complies with the accuracy requirements.

Measuring Relay - An electrical relay intended to switch when its characteristics quantity, under specified conditions and with a specified accuracy attains its operating value.

Medium Distribution (Lighting) - A luminary is classified as having a medium light distribution when its max candlepower point falls between 2.25MH - 3.75MH TRL. The maximum luminaire spacing-to-mounting height ratio is generally 7.5 or less.

Medium Voltage - An electrical system or cable designed to operate between 1kv and 38kv.

Megohmmeter - A testing device that applies a DC voltage and measures the resistance (in millions of ohms) offered by conductor's or equipment insulation.

Melt Time - The time needed for a fuse element to melt, thereby initiating operation of the fuse. Also known as Fuse Melt Time.

Mercury Vapor Lamp (MV) - An HID light source in which the arc tube's primary internal element is Mercury Vapor.

Messenger - A bare wire used to support power or communications cables suspended overhead.

Metal Clad (Switchgear) - An expression used by some manufactures to describe a category of medium voltage switchgear equipment where the circuit breakers are all enclosed in grounded, sheet-steel enclosures.

Metal Enclosed (Switchgear) - An expression used by some manufacturers to describe a category of low voltage, 600 volt class switchgear equipment, where the circuit breakers are all enclosed in grounded, sheet-steel enclosures.

Metal Halide Lamp (MH) - An HID light source in which the arc tube's primary internal element is Mercury Vapor in combination with Halides (salts or iodides) of other metals such as Sodium or Scandium.

Metering (non-tariff) - Values computed depending on the values of digital or analog inputs during variable periods.

Metering (tariff) - Energy values computed from digital and/or analog inputs during variable periods and dedicated to energy measurement for billing purposes.

MHR (Lighting) - Mounting Height Ratio

Micro- - One-millionth

Mil - One-thousandth of an inch (0.001 inch)

Mobile Transformer - A transformer that often is mounted on a leak proof base and can be installed and operated in a semi-trailer, box truck or sea freight container.

Module (Photovoltaic) - See "Photovoltaic Module".

Momentary Rating - The rating of a device to withstand momentary, very high current, without incurring damage.

Mortality Curve - A graphic representation of lamp burnout as a function of time.

Motion Resistant Conductor - ACSR with Motion Resistant Variable Profile.

MOV - Metal Oxide Varistor

MRO - Maintenance and Repair

MTW - Machine tool wire, used for electrical connections inside equipment.

Multi-Crystalline (Photovoltaic) - A material that is solidified at such a rate that many small crystals (crystallites) form. The atoms within a single crystallite are symmetrically arranged, whereas the crystallites are jumbled together.

Multi-element transducer - A transducer having two or more measuring elements. The signals from the individual elements are combined to produce an output signal corresponding to the measurand.

Multi-section transducer - A transducer having two or more independent measuring circuits for one or more functions.

Multi-shot reclosing - A re-closing scheme that permits more than one re-closing operation of a CB after a fault occurs before lock-out occurs.

MV - See "Medium Voltage".

MVA - Apparent Power expressed in Million Volt-Amps.

MW - Mega Watt, one million watts.

MWH - Mega Watt Hour, the use of one million watts for one hour.

N/C - Normally Closed

N/O - Normally Open

Nameplate Rating - The normal maximum operating rating applied to a piece of electrical equipment. This can include Volts, Amps, horsepower, kW, or any other specific item specification for the equipment.

Neutral Conductor - In multiphase circuits, the conductor used to carry unbalanced current. In single-phase systems, the conductor used for a return current path.

Neutral Ground Reactor - A reactor used to connect the neutral point of a three phase system to ground. Neutral Ground Reactors are used to limit ground fault current on Neutral Grounded (WYE) systems.

Neutral Grounding Resistor - A device that connects the neutral point of a three phase system to ground. Neutral Grounding Resistors are used to limit ground fault current on Neutral Grounded (WYE) systems.

Nickel Cadmium Battery - The assembly of one or more cells with an alkaline electrolyte, a positive electrode of nickel oxide and negative electrodes of cadmium.

No Load Loss - See "Core Loss".

Nominal - The normal operating value.

Nominal Capacity (Battery) - A designation by the battery manufacturer which helps identify a particular cell model and also provides an approximation of capacity. It is normally expressed in ampere-hours at a given discharge current.

Nominal Voltage - A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class.

Nominal Voltage (Battery) - Voltage of a fully charged cell or battery when delivering rated capacity at a specific discharge rate. The nominal voltage per cell is 2V for Lead Acid, 1.2V for Nickel-Cadmium, 1.2V for Nickel Metal Hydride and 3.9V for Lithium Ion (small cells only).

Non-cutoff (Lighting) - Luminaire light distribution is classified as non-cutoff when there is no candlepower limitation in the zone above max candlepower.

Non-Halogen Ethylene Copolymers - Non-Halogen Ethylene Copolymers combine attributes of polyethylene and polypropylene to produce cable insulating and jacketing compounds with superior fire protection. Unlike other ethylene compounds, these do not contain chemicals from the Halogen group

Non-Load break - Refers to a group of rubber insulating products that cannot be separated under load. Also see Loadbreak.

Notching Relay - A relay which switches in response to a specific number of applied impulses.

NPS - Negative Phase Sequence

Nylon - For Wire and Cable applications, Nylon, a thermoplastic compound, is used exclusively as a jacketing material. Nylon Jackets provide the insulation system a high degree of mechanical and chemical protection.

OA - Oil-Air, a cooling classification for transformers now classified as ONAN. Oil type, Natural convection flow through cooling equipment and in windings, & Air external cooling medium.

Off Peak Power - Power supplied during designated periods of low power system demand.

Off-Load Tap Changer - A tap changer that is not designed for operation while the transformer is supplying load.

OHL - Overhead Line

Ohm - A unit of electrical resistance defined as the resistance of a circuit with a voltage of one volt and a current flow of one ampere.

Ohm's Law - E=IR; I=E/R; R=E/I; Where E = Voltage impressed on a circuit, I = current flowing in a circuit and R = circuit resistance. Ohm's Law is used for calculating voltage drop, fault current and other characteristics of an electrical circuit.

Oil Breakers - A type of high voltage circuit breaker using mineral oil as both an insulator and an interrupting medium.

OLTC - See "On Load Tap Changer"

On Load Tap Changer - A tap changer that can be operated while the transformer is supplying load.

One-Axis Tracking (Photovoltaic) - A system capable of rotating about one axis for tracking of the sun.

Open Link - A fuse used on overhead electrical distribution systems that is held in place by two springs. This device and its holder have generally been replaced by Fused Cutouts where the fuse element in an arc tube.

Open-Circuit Voltage (Battery) - The voltage of a cell or battery when it is not delivering or receiving power.

Opening Time - For a CB the time between energizing of the trip coil and the instant of contact parting. With a relay the operating time is defined as the time which elapses between the application of a characteristic quantity and the instant when the relay operates.

Operating Current - The current used by a lamp and ballast combination during normal operation.

Operating Current (of a relay) - The current at which a relay will pick up.

Operating time Characteristic - The curve depicting the relationship between different values of the characteristic quantity applied to a relay and the corresponding values of operating time.

Operating Value - The limiting value of the characteristic quantity at which the relay actually operates.

OPGW - Optical Ground Wire - a ground wire that includes optical fibers to provide a communications link.

Oscillograph - An instrument for measuring alternating electric current or voltage by capturing the wave form.

Outage - The state of a component or part of a power system that is not available for service because of some event associated with the component of power system.

Outage, Forced - 1. An outage that results from conditions directly associated with a power system component requiring that it be taken out of service either automatically or after switching operations can be performed.

Outage, Scheduled - An outage that results from intentionally taking a power system out of service, normally for maintenance or replacement.

Output common mode interface voltage - An unwanted alternating voltage which exists between each of the output terminals and a reference point.

Output Current of a transducer - The current produced by the transducer which is an analog function of the measurand.

Output Load - The total effective resistance of the circuits and apparatus connected externally across the output terminals.

Output series mode interface voltage - An unwanted alternating voltage appearing in series between the output terminals and the load.

Output Span - The algebraic difference between the lower and upper nominal values of the output signal.

Over current Relay - A protection relay whose tripping decision is related to the degree by which the measured current exceeds a set value.

Over range - The specified maximum operating point for which the stated accuracy condition applies.

Overcharge (battery) - The forcing of current through a cell after all the active material has been converted to the charged state (after 100% charged). The result will be the decomposition of water in the electrolyte into hydrogen and oxygen gas

Overload - The specified maximum magnitude of the input quantity that can be applied for a specified period of time without causing damage.

Oxygen Recombination - The process by which oxygen generated at the positive plate during charge reacts with the pure lead material of the negative plate and in the presence of sulfuric acid and reforms water.

Pad Mounted Transformer - A transformer that is mounted on a pad (usually concrete or polycrete) that is used for underground service. Pad mounted transformers are available in single phase and three phase configurations.

Parallel Connection - In the case of DC circuits, a way of joining two or more electrical devices or wires by connecting positive leads and negative leads together.

Parametric Conjuctive Test - A conjunctive test that ascertains the range of values of each parameter for which the test meets specific performance requirements.

Parking Bushing - A bushing that is designed to accept a 200a elbow. Parking bushings are used to "Park" a hot cable that is terminated with a 200 Amp rated elbow.

Parkway - Sometimes referred to as a rating for Grade Level Boxes or Covers rating. See "Incidental Light Traffic".

Pasted Plate (Battery) - Paste in which the active material is applied as a paste to a conductive grid.

PCB - Printed circuit board.

PCC - Point of Common Coupling.

PE - Polyethylene. PE is a thermoplastic wire and cable insulating material that is also used for cable jacketing.

Peak to Peak - The amplitude of the ac wave form from its positive peak to its negative peak.

PED - Power Electronic Device.

PF - Power Factor

Phase Angle - The angular displacement between a current and voltage waveform, measured in degrees or radians.

Phase Angle Transducer - A transducer used for the measurement of the phase angle between two a.c. electrical quantities having the same frequency.

Photovoltaic - Refers to the conversion of light into electricity.

Photovoltaic Array - An interconnected system of photovoltaic modules that function as a single electricity producing unit.

Photovoltaic Cell - The smallest semiconductor element within a photovoltaic module to perform the immediate conversion of light into electrical energy (DC Voltage and DC Current).

Photovoltaic Concentrator - A Photovoltaic module that uses optical elements to increase the amount of sunlight incident on a Photovoltaic cell. Concentrating arrays must track the sun. Efficiency is increased, but lifespan is decreased because of the high heat.

Photovoltaic Conversion Efficiency - The ratio of electric energy produced by a photovoltaic device to the energy from sunlight incident unpn the cell.

Photovoltaic Efficiency - The ratio of electric power produced by a cell at any instant to the power of the sunlight striking the photovoltaic cell. This is typically 9% to 14% for commercially available cells.

Photovoltaic Module - The smallest environmentally protected, essentially planar assembly of solar cells and ancillary parts, such as interconnections, terminals and protective devices such as diodes intended to generate dc power under unconcentrated sunlight.

Photovoltaic Panel - Often used interchangeably with Photovoltaic Module. Especially in one-module systems , but more accurately used to refer to a physically connected collection of modules (i.e., a laminate string of modules used to achieve a required voltage and current).

Photovoltaic Stand-Alone System - An autonomous or hybrid photovoltaic system not connected to a grid. The system may or may not have storage but most have require a battery.

Photovoltaic System - A complete set of components for converting sunlight into electricity by the Photovoltaic process, including the array and balance of system devices.

Pick up ratio - The ratio of the limiting values of the characteristic quantity at which the relay resets and operates. This value is sometimes called the differential relay.

Pick-up - A relay is said to 'pick-up' when it changes from the de-energized position to the energized position.

Pilot Channel - A means of interconnecting between relaying points for the purpose of protection.

Pilot Line - A cord or rope used to pull a heavier rope that will be used to pull a conductor into place.

Plante Plate (Battery) - Plate made of pure lead.

Plate (Battery) - The electrode of a cell consisting of a current collector and a positive or negative active material.

Plug Setting Multiple - A term used in conjunction with electromechanical relays, denoting the ratio of the fault current setting of the relay.

Pocket Current Transformer - A round or toroidal core transformer mounted on bushings of power transformers, bulk oil circuit breaker, and other dead tank circuit breakers.

Polarity - 1) The electrical Term used to denote the voltage relationship to a reference potential (+). 2) With regard to Transformers, Polarity is the indication of the direction of the current flow through the high voltage terminals with respect to the direction of current flow through the low voltage teminals.

Pole Spacing (Lighting) - (ILL x CU x LLF)/(AMF x RW)

Polycrystalline - See "Multi Crystalline".

Polyethylene - A thermoplastic material composed of ethylene polymers. Polyethylene has excellent electrical and mechanical properties and is used an insulating material in cable.

Polyphase - A polyphase system is a means of distributing alternating current electrical power.

Polyvinyl Chloride - Polyvinyl Chloride. PVC, a thermoplastic compound, is a commonly used Wire and Cable insulation and jacketing material.

Pot - 1) Slang for an overhead transformer. 2) Short for "Potential".

Potential - The voltage in a circuit. Reference is usually to the AC Voltage.

Potential Transformer - A transformer used to lower the voltage at a set ratio so that the voltage can be measured by instruments and meters at a safe representative level.

POW - Point-on-Wave. Point-on-wave switching is the process to control moment of switching to minimize the effects (inrush currents, over-voltages).

Power - Rate at which energy is released or consumed, expressed in watts.

Power Electronics Device - An electronic device (e.g. thyristor or IGBT) or assembly of such devices (e.g. inverter). Typically used in a power transmission system to provide smooth control of output of an item of plant.

Power Factor - The ratio of energy consumed (watts) versus the product of input voltage (volts) times input current (amps).

Power Line Carrier Communication - A mean of transmitting information over a power transmission line by using a carrier frequency superimposed on the normal power frequency.

Power Transformer - A large transformer, generally larger than 1,000 kVA in capacity.

Protected Zone - The portion of a power system protected by a given protection system or a part of that protection system.

Protection Equipment - The apparatus, including protection relay, transformers and ancillary equipment, for use in a protection system.

Protection Relay - A relay designed to initiate disconnection of a part of an electrical installation or to a warning signal, in the case of a fault or other abnormal condition in the installation.

Protection Scheme - The coordinated arrangements for the protection of one or more elements of a power system. A protection scheme may compromise several protection systems.

Protection System - A combination of protection equipment designed to secure, under pre-determined conditions, usually abnormal, the disconnection of an element of a power system, or to give an alarm signal, or both.

PS (Lighting) - Pole Spacing

psi - Pounds per square inch

PT - See "Potential Transformer".

Pull - A noun referring to the installation of one or more cables.

Pull Tension - The tension in pounds or kilograms required to pull a cable or wire into a duct or conduit or into an overhead location.

Pulling - The act of installing one or more cables.

PV - See "Photovoltaic"

PVC - Polyvinyl chloride, a common thermoplastic insulation and jacketing material used to manufacture building wire and other types of wire and cable. It is also used in the manufacture of plastic conduit.

Raceway - An enclosed channel designed expressly for holding conductors and cables, including conduit and tubing, wire ways, and bus ways.

Range - Nominal operating limits, specified by the lowest calibration point to the highest calibration point.

Rated Capacity (Battery) - The number of Amp-Hours a battery can deliver under specific conditions (rate of discharge, end voltage, temperature).

Rated Lamp Life - With regard to lighting, the point in time when 50% of a statistically significant number of lamps has failed.

Rated Output - The output at standard calibration.

Rating - The nominal value of an energizing quantity that appears in the designation of a relay. The nominal value usually corresponding to the CT and VT secondary ratings.

Ratio Correction - A feature of digital relays that enables compensation to be carried out for a CT or VT ratio that is not ideal.

RCD - Residual Current Device. A protection device which is actuated by the residual current.

Reactance - The opposition of inductance and capacitance to alternating current equal to the product of the sine of the angular phase difference between the current and voltage.

Reactive Power - A component of apparent power (volt-amps) which does not produce any real power (watts). It is measured in VARs volt-amps reactive.

Reading - The expected output at a given input value.

Real Power - The average value of the instantaneous product of volts and amps over a fixed period of time in an AC circuit.

Recloser - A switching device that rapidly recloses a power switch after it has been opened by an overload. In reclosing the power feed to the line, the device tests the circuit to determine if the problem is still there. If not, power is not unnecessarily interrupt

Recombination (Battery) - State in which the hydrogen and oxygen gasses normally formed within the battery cell during charging are recombined to form water.

Reel - A cylinder device used to hold wire and cable until installed. There are standard reel sizes that are used in the electrical industry that are either wood (non-returnable) or steel (returnable).

Reference range - A specific range of values of an influence quantity within which the transducer complies with the requirements concerning intrinsic errors.

Reference value - A specified single value of an influence quantity at which the transducer complies with the requirements concerning intrinsic errors.

Refererence Conditions - Conditions of use for a transducer prescribed for performance testing, or to ensure valid comparison of results of measurement.

Reflector - A device used to re-direct the luminous flux from a light source by the process of reflection.

Refractor - A device used to re-direct the luminous flux from a light source by the process of refraction.

Regulating Transformer - A transformer used to vary the voltage, or phase angle, of an output circuit. It controls the output within specified limits and compensates for fluctuations of load and input voltage.

Regulator - A device that is used to control the voltage of a circuit by raising and lowering it.

Reinforced Polymer Motor - Also referred to as "RPM". See "Polymer Concrete".

Relay - Numerical - A protection relay which utilizes a digital signal processor to execute the protection algorithms in software.

Relays - Distance - Relays used on transmission lines that use a variety of sensors and measurements to determine when an unusual condition exists at some distance, out on the transmission circuit.

Relays - Over-current - Protective relays used on power systems that detect excessive currents and send signals to protective devices, such as power circuit breakers.

Relays - Voltage - Protective relays used on power systems that detect when line voltage has gone outside of an acceptable range, either up or down, and send a signal to a protective device or system.

Resealable Cap (Battery) - A safety vent valve which is capable of closing after each pressure release from within a cell.

Resetting value - The limiting value of the characteristic quantity at which the relay returns to its initial position.

Residual Current - The algebraic sum, in a multi-phase system, of all the line currents.

Residual Voltage - The algebraic sum, in a multi-phase system, of all the line-to-earth voltages.

Resistance - The opposition to current flow, expressed in ohms.

Restricted Approach Boundary - An approach limit at a distance form an exposed live part within which there is an increased risk of shock, due to electrical arc over combined with inadvertent movement, for personnel working in close proximity to the live part.

RHH - A rubber or XLPE insulated conductor designed to be used at operating temperatures up to 90 degrees Celsius in dry locations.

RHH-2 - A rubber or XLPE insulated, moisture resistant conductor designed to be used at operating temperatures up to 90 degrees Celsius in dry and wet locations.

Ridge Pin - A device that allows the mounting of a pin type insulator to a pole. The ridge pin is bolted to the top of the pole and the insulator is screwed onto the threads at its top.

Ripple - The magnitude of AC fluctuation in a DC signal, after filtering. Ripple is usually expressed as a percentage of rated output.

Ripple Content of the Output - With steady-state input conditions, the peak-to-peak value of the fluctuating component of the output.

Riser Pole - A pole used to transition from overhead and underground cables.

Root-Mean-Square - The effective value of alternating current or voltage. The RMS value equates an AC current or voltage to a DC current or voltage that provides the same power transfer.

RPM - Reinforced Polymer Mortar. See "Polymer Concrete".

S.I.R. - System Impedance Ratio

Sag - The amount of vertical displacement of an overhead conductor between support points. Sag is a consideration when designing a pole or tower line and will be a determining consideration in the overall height of the structure. Sag varies with the temperature.

SAIDA - A distribution system reliability measure of the system average interruption duration index. It is commonly measured in customer minutes of interruption and is commonly used as an electric service performance metric.

SAIFI - A distribution system reliability measure of the system average interruption frequency index. It measures sustained outages and interruptions and is a metric for the entire power system.

SAT - Site Acceptance Test. Validation procedures for equipment executed with the customer on site.

Scaling Resistor - A resistor added to an output circuit of measurement equipment to provide a scaled voltage output. The output is not a "true" voltage output and may be susceptible to loading errors.

Schematic Diagram - A diagram which shows, by means of graphic symbols, the electrical connections and functions of a circuit.

Sealed Cell (Battery) - Cells that are free from routine maintenance and can be operated without regard to position.

Self Discharge (Battery) - The decrease in the state of charge of a battery or cell, over a period of time, due to internal electro-chemical losses.

Semi-Con - The semi-conducting material extruded over the insulation on medium voltage insulated cables.

Semi-Crystalline - See "Multi-Crystalline".

Semi-cutoff (Lighting) - Luminaire light distribution is classified as semi-cutoff when the candlepower per 1000 lamp lumens does not numerically exceed 50 (5.0%) at an angle of 90 degrees above nadir (horizontal), and 200 (20%) at a vertical angle of 80 degrees above nadir.

Separator (Battery) - A porous, insulating material placed between plates of opposed polarities, to prevent internal short circuits.

SER - Service Entrance Cable.

Series Connection - For DC circuits, a way of joining batteries, electrical devices and wires in such a way that positive leads are connected to negative leads. This is generally done to increase voltage.

Service Life (Battery) - The total period of useful life of a battery, normally expressed in the total number of Charge/Discharge cycles.

Shock Hazard - A dangerous electrical condition associated with the possible release of energy caused by contact or approach to energized parts.

Short Circuit - 1. A load that occurs when at ungrounded conductor comes into contact with another conductor or grounded object. 2. An abnormal connection of relatively low impedance, whether made intentionally or by accident, between two points of different potential.

Shotgun Stick - A specialized hot stick that allows the capture of certain types of clamps and devices in its hook. It is also called a "Grip All" stick.

SI - See "International System of Units".

Sidewall Pressure - The force exerted on a cable as it is dragged around a bend. The longer the pull and the tighter the bend radius, the higher the sidewall pressure will become.

Silicon - A chemical element (Si), atomic number 14, semi-metallic in nature, dark gray, that is an excellent semiconducting material and is the most common semiconducting material used in making photovoltaic devices.

Single Element Transducer - A transducer having one measuring element.

Single Phase - Single Phase electric power refers to the distribution of electric power using a system in which the voltage is taken from one Phase of a three Phase source.

Single-Phase - This implies a power supply or a load that uses only two wires for power.

Single-Shot Reclosing - An auto-reclose sequence that provides only one reclosing operation, lock-out of the CB occurring if it subsequently trips.

Sintered Plate (Battery) - The plate of an alkaline cell, the support of which is made of sintered metal powder, and into which the active material is introduced.

Skin Effect - In an ac system, the tendency of the outer portion of a conductor to carry more of the current as the frequency of the ac increases.

Sky Wire - See "Static Wire"

Sleeve - See "Compression Splice".

Soap - Slang for "Cable Pulling Lubricant".

SOE - Sequence of Events

Solar Cell - See "Photovoltaic Cell".

Solar Energy - Energy from the sun. The heat that builds up on surfaces exposed to the sun is an example.

SOTF - Switch on to Fault (protection).

Spacing-to-Mounting Height Ratio - Ratio specification used to insure that fixtures are adequately spaded, thus preventing "hotspots"

Span - 1) Refers to the distance between two poles of a transmission or distribution line. 2) The algebraic difference between the upper and lower values of a range.

Spark Test - A high-voltage test performed on certain types of conductor during manufacture to ensure the insulation is free from defects.

Specific Conjuctive Test - A conjunctive test using specific values of each of the parameters.

Specific-Gravity (Battery) - The weight of the electrolyte compared to the weight of an equal volume of pure water. It is used to measure the strength or percentage of sulfuric acid in the electrolyte.

Spill Light - Unwanted light directed onto a neighboring property. Also referred to Light Trespass.

Spring Winding Time - For spring-closed CB's, the time for the spring to be fully charged after a closing operation.

Stability - The ability of a device to maintain its performance characteristics over a specified period of time.

Stability Limits of a Protection System - The r.m.s. value of the symmetrical component of the through fault current up to which the protection system remains stable.

Stability of a Protection System - The quantity whereby a protection system remains inoperative under all conditions other than those for which it is specifically designed to operate.

Stability of Transducer - The ability of a transducer to keep its performance characteristics unchanged during a specified time, all conditions remaining constant.

Standard calibration - The nominal point at which a measurement device is adjusted.

Starter - A device used in conjunction with a ballast for the purpose of starting an electric discharge lamp.

Starting Current - Current required by the ballast during initial arc tube ignition. Current changes as lamp reaches normal operating light level.

Starting Relay - A unit relay which responds to abnormal conditions and initiates the operation of other elements of the protection system.

Starved Cell (Battery) - A cell containing little or no free fluid electrolyte solution. This enables gasses to reach electrode surfaces readily, and permits relative high rates of recombination.

STATCOM - A particular type of Static Var Compensator, in which Power Electronic Devices such as GTO's are used to generate the reactive power required, rather than capacitors and inductors.

State of Charge (Battery) - The available amp-hours in a battery at any point of time. State of Charge is determined by the amount of sulfuric acid remaining in the electrolyte at the time of testing or by the stabilized open circuit voltage.

Static Relay - An electrical relay in which the designed response is developed by electronic, magnetic, optical or other components without mechanical motion. Excludes relays using digital technology.

Static Var Compensator - A device that supplies or consumes reactive power comprised solely of static equipment. It is shunt-connected on transmission lines to provide reactive power compensation.

Static Wire - A wire placed above the phase wires of a distribution of transmission circuit to protect against lightning. It is normally galvanized or aluminized steel.

STC - Short Time Current rating of a CT.

Stick - See Hotstick.

Stinger - Slang for the wire connecting a fused cutout or switch to a transformer bushing.

Storage Conditions - The conditions defined by means of ranges of the influence quantities, such as temperature, or any special conditions, within which the transducer may be stored (non-operating) without damage.

Strand - One of the wires that made up a stranded conductor.

Stranded Conductor - A conductor made by twisting together a group of wire strands.

Stringing - The act of installing overhead electrical wire or conductor.

Stringing Block - A sheave used to support and allow movement of a cable that is being installed. These are normally used overhead but there are also specialized designs used at the entrance to a conduit system.

Stringing Dolly - See "Stringing Block".

Sub-Transmission System - A high voltage system that takes power from the highest voltage transmission system, reduces it to a lower voltage for more convenient transmission to nearby load centers, delivering power to distribution substations or the largest industrial plants.

Sulfation (Battery) - The formation of lead sulfate of such physical properties that it is extremely difficult, if not impossible, to reconvert it to active material.

Sulfur-Hexafluoride (SF6) - A very dense, inert, non-conducting gas used inside high voltage equipment to insulate conducting components from surfaces at ground potential. It also is used as an interrupting medium in high voltage circuit breakers.

Super Draw Lead - Also known as a split conductor. Historically bushings offered a draw lead rating of 400 amps, but by using Trench's split conductor in COTA bushings the draw leads now have ratings of 3,000 amps.

Surge Arrester - See Arrester.

Surge Withstand - A measure of an electrical device's ability to withstand high-voltage or high-frequency transients of short duration without damage.

Sweeling (Battery) - The swelling or bulging of a battery case that results from cell vents not allowing enough internal pressure to be relieved.

Switchgear - A general term covering switching and interrupting devices and their combination with associated control, metering, protective and regulating devices.

Switching Impulses - See "Lightning and Switching Impulses".

Switching Surges - A high voltage spike that occurs when current flowing in a highly inductive circuit, or a long transmission line, is suddenly interrupted.

System Disturbance Time - The time between fault inception and CB contacts making on successful re-closure.

System Impedance Ratio - The ratio of the power system source impedance to the impedance of the protected zone.

T&D - Transmission and Distribution.

T-Body - A device used to terminate main feeder cables operating at medium voltages (4-35KV nominal). T-Bodies are molded from synthetic rubber and are electrically shielded.

Tag Line - A rope used to control the position of equipment being lifted. This is not to be confused with the rope used to actually lift the equipment.

Tap Changer - A mechanism usually fitted to the primary winding of a transformer, to alter the turns ratio of the transformer by small discrete amounts over a defined range.

Temper - The softness of a metal; terms such as soft-drawn, dead soft, annealed, and semi-annealed are used to describe tempers used for conductor metals.

Temperature Rise - The increase in temperature that results when electrical load is carried by electrical equipment.

Tensile Strength - The greatest longitudinal force that a substance can bear without tearing apart or rupturing; also called ultimate tensile strength.

Tension - The force in pounds of kilograms on a conductor installed overhead. Too much tension on an overhead line can contribute to mechanical failure.

Termination - 1) The act of preparing the connection or transition of an insulating cable. 2) The device that transitions an underground cable to an overhead cable or wire.

Terminator - A device used to transition between overhead and underground, medium and high voltage conductors.

TF - The Transfer Function of a device usually an element of a control system.

TFE - A Heat-resistant insulation compound made with tetrafluoroethylene (Teflon).

Thermal Expansion - The expansion of a material when subjected to heat.

Thermoplastic - A plastic compound that will soften and melt with sufficient heat. Thermoplastic insulation compounds are used to manufacture certain types of electrical cables.

Thermoset - A plastic compound that will not remelt. Thermoset insulation compounds are used to manufacture certain types of cables.

THHN - A thermoplastic-insulated, nylon-jacketed conductor designed for use in dry locations and an operating temperature of up to 90 degrees Celsius

Thin Film - See "Amorphous Semiconductor"

Thin Film (Photovoltaic) - A layer of semiconductor material, such as copper indium diselenide, cadmium telluride, gallium arsenide, or amorphous silicon, a few microns or less in thickness, used to make photovoltaic cells.

Three Phase - Three-phase refers to one circuit consisting of three conductors where the current and voltage in each conductor (phase) is 120° out of phase with each other phase.

Three Wire - See Delta.

Three-Phase - Multiple phase power supply or load that uses at least three wires where a different voltage phase from a common generator is carried between each pair of wires.

Through Fault Current - The current flowing through a protected zone to a fault beyond that zone.

Thumper - A high voltage device used to locate an underground cable fault. The device applies a high voltage to the faulted cable with a resulting discharge to ground at the location of the fault.

THW - A thermoplastic insulated, moisture resistant conductor designed for use in wet or dry locations and an operating temperature of up to 75 degrees Celsius.

THWN-2 - A thermoplastic insulated, nylon-jacketed, moisture resistant conductor designed for use in wet or dry locations and an operating temperature of up to 75 degrees Celsius.

Tie - A wire device that connects a conductor to an insulator.

Time Delay - A delay intentionally introduced into the operation of a relay system.

Time Delay Relay - A relay having an intentional delaying device.

Tow Axis Tracking (Photovoltaic) - A photovoltaic system capable rotating on two axes (vertical and horizontal) to track the sun for maximum efficiency of the solar array.

TPI - Tap Position Indicator for transformers.

Tracking Array (Photovoltaic) - A photovoltaic array that follows the path of the sun to maximize the solar incident on the photovoltaic surface.

Transducer - A device for converting an electrical signal into a usable direct current or voltage for measurement purposes.

Transducer Error - The actual value of the output minus the intended value of the output expressed algebraically.

Transducer Factor - The product of the current transformer ratio (CTR) and the voltage transformer ratio (VTR). Also called the power ratio.

Transducer with Live Zero - A transducer which gives a predetermined output other than zero when the measurand is zero.

Transducer with Suppressed Zero - A transducer whose output is zero when the measurand is less than a certain value.

Transformer - An electro-magnetic device used to change the voltage in an alternating current electrical circuit.

Transformer Bank - See "Bank".

Transformer Insulation - This is the material that is used to provide electrical insulation between transformer windings at different voltage levels and also between the energized parts and the metal tank of the transformer.

Transformer Ratio - When used in reference to Instrument Transformers, this is simply the ratio of transformation of one or more transformers used in the circuit. If both Cts and VTs are included, the transformer ratio is the product of the CT and the VT.

Transformer Voltage Regulators - Mechanisms that use multiple voltage taps on a transformer-like device to adjust voltage on a power line.

Transient - See "Voltage Transient"

Transmission System - Normally, the highest voltage network of an electric utility system. This is the portion of the system that carries high power over the longest distances. Typically operating at voltages in excess of 100 kV, and most usually at 200 kV and above.

Traveler - See "Stringing Block".

Tree Wire - A type of Overhead Distribution Wire that is insulated for momentary contact with tree branches and used as a primary voltage conductor.

Treeing - Water treeing is a form of cable insulation degradation where micochannels, that often appear as a tree-like structure in the insulation, develop due to a complex interaction of water, electrical stress, impurities and imperfections.

Trickle Charge (Battery) - A continuous low rate charge that compensates for the self discharge rate of a battery. Also known as Float Charge.

True RMS Amps - 1) The effective value of an AC signal. For an amp signal, true RMS is a precise method of stating the amp value regardless of waveform distortion. 2) An AC measurement which is equal in power transfer capability to a corresponding DC current.

True RMS volts - 1) The effective value of an AC voltage value regardless of the waveform distortion. 2) An AC measurement which is equal power transfer capability to a corresponding DC voltage.

TRXLP - Tree Retardant Cross Linked Polyethylene. A thermoset plastic compound that is used for insulation of wire and cable containing an anti-treeing compound.

Tubular Plate (Battery) - A positive plate which is composed of assembly of porous tubes of perforated metal or tissure with or without a central current collector spine. The active material is placed within the tube.

Tungsten Halogen Lamp - A gas-filled tungsten halogen lamp containing a certain proportion of halogens.

UD - Underground Distribution

UF - A thermoplastic insulated, underground feeder conductor or cable designed for use in wet locations, including direct burial.

UHV - See "Ultra High Voltage".

Ultra High Voltage (UFV) - Transmission systems in the ac voltage exceeds 800,000 volts.

Unbalanced Loads - Refers to an unequal loading of the phases in a three-phase system.

Underground Residential Distribution - (URD) Refers to the system of electric utility equipment that is installed below grade.

Underground Utility Structure - An enclosure for use underground that may be either a handhole or manhole.

Unidirectional Unit - Allows inputs to be measured in one direction only. The stated output range indicates the minimum and maximum input levels.

Unit Electrical Relay - A single relay that can be used alone or in combinations with others.

Unit Protection - A protection system that is designed to operate only for abnormal conditions within a clearly defined zone of the power system.

Universal Bushing Well - This 200 amp rated component is used as part of a system to terminate medium voltage cables to transformers, switchgear and other electrical equipment.

Unrestricted Protection - A protection system which has no clearly defined zone of operation and which achieves selective operation only by time grading.

UPS - Uninterruptable Power Supply

URD - Underground Residential Distribution.

USE - Underground Service Entrance conductor or cable.

V - Voltage; Volt.

VA - 1) Electrical capacity or electrical load, expressed as Volts x Amps. 2) Volt Ampere rating designates the output which a transformer can deliver at rated voltage and frequency without exceeding a specified temperature rise.

VAC - Volts AC.

Vacuum Circuit Breakers - Circuit breakers, normally applied at medium voltages, that use vacuum interrupters to extinguish the electrical arc and shut-off flowing current.

Vacuum Interrupter - A sealed "bottle" containing contacts of a switch inside a very high vacuum. When the contacts are parted in the vacuum, as there is no gas in the bottle to ionize, the current flow is quickly extinguished.

Valve Regulated Sealed Cell (Battery) - A battery in which the cells are closed but have a valve which allows the escape of gas if the internal pressure exceeds a predetermined value (pressure).

Vapor Phase - In the core-type transformer, the core-and-coil assembly is independent of the tank, so that the assembly is allowed to completely dry.

VAR - Volt Ampere Reactive. Also see "Reactive Power".

VCB - Vacuum Circuit Breaker.

VDC - Volts DC.

Vector Group Compensation - A feature of digital and numerical relays that compensates for the phase angle shift that occurs in transformers due to use of dissimilar winding connections. For example transformers connected in delta/star.

Veiling Luminance - A luminance superimposed on the retinal image which reduces its contrast. It is this veiling effect produced by bright sources or areas in the visual field that results in reduced visual performance and visibility.

Vent Cap (Battery) - The plug on top of a cell that can be removed to check and change the level of the electrolyte.

Vent Valve (Battery) - A normally sealed mechanism which allows the controlled escape of gasses from within a cell.

Venting (Battery) - The release of gas from a cell, either controlled (through a vent) or accidental.

Volt - A unit of electromotive force. The electrical potential needed to produce one ampere of current with a resistance of one ohm.

Voltage Class - The general strength of electrical insulation on a device, determining the maximum continuous voltage that can be applied between the conducting parts and ground potential, without damaging the insulation.

Voltage Drop - The loss of voltage in a circuit when current flows.

Voltage Gradient - See "Voltage Drop"

Voltage Rating - The normal voltage to be applied to an electrical device to provide for proper operation.

Voltage Regulation - The maintenance of a voltage level between two established set points, compensating for transformer and/or line voltage deviation, caused by load current. The voltage change is affected by the magnitude and the power factor of the load current.

Voltage Spread - The difference between maximum and minimum voltages.

Voltage Swells - Voltage Swells are momentary (typically a few milliseconds to a few seconds duration) over-voltage conditions which can be caused by such things as a sudden decrease in electrical load or a short circuit occurring on electrical conductors.

Voltage Transducer - A transducer used for the measurement of a.c. voltage.

Voltage Transformer - Transformer used to accurately scale ac voltages up or down, or to provide isolation. Generally used to scale large primary or bus voltages to usable values for measuring purposes

Voltage Transformer Ratio - The ratio of primary volts divided by secondary volts

Voltage Transients - A transient (sometimes called impulse) is an extremely fast disturbance (millionths of a second to a few milliseconds) evidenced by a sharp change in voltage.

Voltage Withstand Test - A field or factory test in which a conductor or electrical equipment is subjected to a higher than normal AC or DC voltage to test its insulation system.

VT - See "Potential Transformer".

Watt - 1) With ac measurements, effective power (measured in Watts) equals the product of voltage, current, and power factor (the cosine of the phase angle between the current and the voltage). Watts=EI cosine(Theta).

Watt-Hour - 1) A unit of work equal to the power of one watt operating for one hour. 2) 3600 Joules.

Wire - A strand or group of strands of electrically conductive material, normally copper or aluminum.

Wire Lubricant - A chemical compound used to reduce pulling tension by lubricating a cable when pulled into a duct or conduit.

Working Near - Refers to working near live parts. Any activity inside a limited approach boundary.

Working On - Refers to working on live parts. Coming in contact with live parts with the hands, feet, or other body parts, with tools, probes, or test equipment, regardless of the personal protective equipment a person is using.

Wye - A three phase, four-wire electrical configuration where each of the individual phases is connected to a common point, the "center" of the Y. This common point normally is connected to an electrical ground.

X - Reactance expressed in Ohms.

XHHW-2 - An XLPE insulated, moisture resistant conductor designed for use in wet or dry locations and an operating temperature of up to 90 degrees Celsius.

XLP - See "XLPE"

XLPE - Cross-Linked Polyethylene. A thermo set plastic compound that is used for insulation of wire and cable.

Y - See "Wye".

Yield Strength - The force required to stretch a material.

Z - Impedance

Zero Crossing - The point at which a sinusoidal voltage or current waveform crosses the zero reference axis.

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July 9-11 2013 San Fransisco, USA.

Greenergy Argentina

July 10-12 2013 Buenos Aires, Argentina.

EnterSolar+ Brasil

July 17-19 2013 Sao Paulo, Brazil.

Solarcon India

August 01-03 2013 Banglore, India.

Renewable Energy Conference & Exhibition

August 08-10 2013 Nariabi, Kenya.

Ghuangzhou International Solar Photovoltaic, Biomass and Wind Energy Exhibition

August 19-21 2013 Guangzhou, China.

Solar-Hydro-Bio-Wind Energy Liveweek

August 29-30 2013 Banglore, India.

Brasil Windpower

September 03-05 2013 Rio, Brazil.

Expo Solar

September 04-06 2013 Goyang, Korea.

Expo Geothermal

September 04-06 2013 Denizli, Turkey.

Renewable Energy Technology Conference & Exhibition

September 09-11 2013 Wahington DC, USA.

Combodia Internation Power-Transmission-Distribution & Electrical Engineering Show

September 10-12 2013 Phnom Penh, Combodia.

Power Industry India

September 11-12 2013 New Delhi, India.

All Energy Turkey

September 11-12 2013 Istanbul, Turkey.

Renewable Energy India

September 12-14 2013 Greater Noida, India.

Turkmen Energy Exhibition

September 12-14 2013 Ashkabad, Tukemenistan.

Solar Asia Expo

September 17-19 2013 Kuala Lampur, Malaysia.

World Renewable Energy Technology Congress & Expo

September 25-27 2013 New Delhi, India.

Power Nigeria

October 02-04 2013 Lagos, Nigeria.

Energy Solutions London

October 09-10 2013 London, UK.

China Wind Power

october 16-18 2013 Beijing, China.

Renewable UK Conference & Exhibition

November 05-07 2013 Birmingham, UK.

China Sourcing Fare: Solar and Energy Saving Products

November 07-09 2013 Johannesburg, SA.

InterSolar India

November 12-14 2013 Mumbai, India.

Veitnam Energy Forum & Expo

November 13-15 2013 Hanoi, Vietnam.

25th Power-Gen International

November 12-14, 2013 Orlando, FL USA.

Vietnam Energy Forum & Expo

November 13-15 2013 Hanoi, Vietnam.

Solar Philipines Exhibition & Conference

November 14-15 2013 Manila, Philipines.

IG China

November 20-22 2013 Chengdu, China.

Green Expo France

November 26-28 2013 Lyon, France.

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