A
A
1) Amperes; Amps. 2) Area. For cables Area is expressed in Circular Mils.
AA
1) The Aluminum Association. 2) Refers to All Aluminum as in All Aluminum Conductor.
AAAC
All Aluminum Alloy Conductor.
AAC
All Aluminum Conductor.
AAC/TW
All Aluminum Conductor, Trapezoidal-Shaped Aluminum Strands.
AASHTO
American Association of Safety Highway Traffic Officials.
ACAR
All Aluminum Conductor, Aluminum Alloy Reinforced.
ACB
Air Circuit Breaker.
Access Point
A wireless networked device usually connected to a wireless LAN used to access the wired LAN.
Accuracy Class
A number used to indicate the accuracy range of a measurement transducer, according to the defined standard.
ACSR
Aluminum Conductor Steel Reinforced.
ACSR/AW
Aluminum Conductor, Aluminum Clad Steel Reinforced.
ACSR/TW
ACSR conductor made using Trapezoidal Wire construction.
ACSS
Aluminum Conductor Steel Supported. This is a conductor that is generally used for overhead transmission construction. ACSS is often preferred over ACSR because of its superior sag characteristics.
ACSS/AW
Aluminum Conductor, Aluminum Clad Steel Supported.
ACSS/TW
ACSS conductor made using Trapezoidal Wire construction.
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.
Admittance
The reciprocal of Impedance (1/Z).
AEIC
Association of Edison Illuminating Companies.
Aeolian Vibration
A natural forced vibration caused by wind flowing over a conductor. This occurs at alternate wind induced vortices and at wind speeds typically at 8 to 12 MPH.
Aerial Cable
An assembly of insulated conductors installed on a pole or similar overhead structures. It may be self supporting or attached to a messenger cable.
AFCI
Arc Fault Circuit Interrupter.
AFD
Adjustable Frequency Drive.
AFI
Arc Fault Interrupter.
AIC
Arc Interrupting Current.
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.
Alley Arm
A side brace for a cross arm that is not loaded (balanced) evenly.
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.
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.
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.
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.
ANSI
American National Standards Institute. ANSI is located at 1430 Broadway, New York, NY 10018.
Antenna Gain
An antenna’s transmission power, provided as a ratio of its output (send) signal strength to its input (receive) signal strength, normally expressed in dBi. The higher the dBi, the stronger the antenna.
Anti-Pumping Device
A feature incorporated in a Circuit Breaker or re-closing scheme to prevent repeated operation where the closing impulse lasts longer than the sum of the relay and CB operating times.
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.
Arcing Time
The time between instant of separation of the CB contacts and the instant of arc excitation.
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.
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.
ASTM
American Society for Testing and Materials. ASTM is located at 1916 Race Street, Philadelphia, PA 19103.
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. Most battery systems are designed for a certain minimum number of days or operation before recharging is needed should sufficie.
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.
AWG
American Wire Gauge.
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.
A-H
Ampere-Hour
A/D Conversion
The process of converting an analogue signal into an equivalent digital one utilizing an A/D converter.
B
Balanced polyphase system
A polyphase system in which both the currents and voltages are symmetrical.
Bandwidth
The data carrying capacity of a transmission path, measured in bits or bytes per second.
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 Cell
An electrochemical device composed of positive and negative plates, separator, and electrolyte which is capable of storing electrical energy.
Battery Tray
A contained unit 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.
Beacon
In wireless networking, a beacon is a packet sent by a connected device to inform other devices of its presence and readiness.
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.
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.
Bias Current
The current used as a bias quantity in a biased relay.
Blowing
The act of installing fiber optic cable into a duct using air pressure.
Bluetooth
A wireless computing and telecommunications specification that defines how mobile personal computing devices work with each other and with regular computers and phone systems within a close range.
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.
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.
Boost Charge
A charge applied to a battery which is already near a state of full charge, usually of short duration.
Breakdown Voltage
The voltage at which a dielectric material fails.
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.
Bulb Envelope
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.
BURD
Buried Urban Residential Distribution.
Burden
Load imposed by an electronic or electrical device on the measured input circuit, expressed in volt-amps.
Buried Urban Residential Distribution
Refers to the system of electric utility equipment installed below grade.
Bushing
An insulator having a conductor through it, used to connect equipment to a power source.
C
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.
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.
Category 5 Cable
Also known as “Cat 5”, this cable is used for fast ethernet and telephone communications. The cable is constructed of 4 twisted pair of copper wire.
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.
CDMA
Code Division Multiple Access. CMDA is a technique used mainly with personal communications devices such as mobile phones that digitizes the conversation and tags it with a special frequency code. The data is then scattered across the frequency band.
Cell-Reversal (Battery)
Reversing of polarity within a cell of a multi-cell battery due to over discharge.
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 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 (Battery)
The conversion of electrical energy from an external source, into chemical energy within a cell or battery.
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.
Chlorinated Polyethylene
Chlorinated Polyethylene. CPE, a thermoplastic compound, is used to jacket certain types of power cable.
CH2H2
Acetylene.
CH4
Methane.
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 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.
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.
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.
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. Load losses vary by the square of the current magnitude. Load losses are composed of losses due to the current flow through the resistance of the conductors (the copper loss) as well as eddy losses in the windings, magnetic friction in the core known as hysteresis, and stray losses due to current flow through other components.
Collector Roadway (Lighting)
The distributor and collector roadways servicing traffic between major and local roadways. These are roadways used mainly for traffic movements within residential, commercial and industrial areas.
Compliance Voltage
The specified maximum voltage that a transducer (or other device) current output must be able to supply while maintaining a specified accuracy.
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.
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 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.
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.
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.
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 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 crossection 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.
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 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.
Cu
The chemical symbol for copper.
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. For example, a CT that is rated to carry 200 Amps in the primary and 5 Amps in the secondary, would have a CT ratio of 200 to 5 or 40:1.
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.
Cut Off Voltage
Battery Voltage reached at the termination of a discharge. Also Known as the End Point Voltage (EPV).
CU (Lighting)
Coefficient of Utilization.
Cycle
In Alternating current, the change of the poles from negative to positive and back.
C-Rate
Battery discharge current in amperes; numerically equal to rated capacity of a cell in ampere-hours.
C2H4
Ethylene.
C2H6
Ethane.
D
DA Bolt
A Double Arming Bolt.
Deep Discharge (Battery)
Withdrawal of 50% or more of the rated capacity of a cell or battery.
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.
DES
Data Encryption Standard. DES is an encryption, method that uses an algorithm for private key encryption, in which the sender uses the same private key as the recipient uses to decode it.
Design Load
The actual, expected load or loads that a device or structure will support in service.
Device Control Point
Local keypad on device level to control the switchgear often combined with local or remote switch.
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.
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.
Digital Signal Processing
A technique for the processing of digital signals by various filter algorithms to obtain some desired output.
Digital Signal Processor
A microprocessor optimized in hardware design and software instruction set for the processing of analog signals digitally. This is achieved by DFT and similar techniques.
Dipole Antenna
A type of antenna commonly used in wireless networking devices. It has a signal range of 360 degrees horizontally and 75 degrees vertically.
Dip Tolerance (Lighting)
With regard to outdoor lighting, the percentage of instantaneous voltage variation from normal that is required to extinguish a light source.
Directional Relay
A protection relay in which the tripping decision is dependent in part upon the direction in which the measured quantity is flowing.
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.
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.
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.
Disconnect Switch
A simple switch that is used to disconnect an electrical circuit. It may or may not have the ability open while the circut is loaded.
Distortion Factor
The ratio between the r.m.s. value of the harmonic content and the r.m.s. value of the non-sinusoidal quantity.
Distribution Automation
A system consisting of line equipment, communications infrastructure, and information technology that is used to gather intelligence about a distribution system. It provides analysis and control in order to optimize operating efficiency and reliability.
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.
Disturbed Network Protocol
A proprietary communication protocol used on secondary networks between HMI, substation computers or bay computers and protective devices.
DMZ
Demilitarized Zone. Networking has corrupted the term and used it to refer to an unprotected subnet connected to a local network, but outside the protection of a firewall.
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.
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.
DTIM
Delivery Traffic Indication Message. A DTIM is a signal sent as part of a beacon by an access point to a client device in sleep mode, alerting it that a packet of data awaits delivery.
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 Bank
A Duct Bank is two or more ducts or conduits used as part of a system.
E
E85
A fuel with 85% ethanol and 15% gasoline blend.
Earthing Transformer
A three-phase transformer intended essentially to provide a neutral point to a power system for the purpose of grounding.
Earth Fault Protection System
A protection system which is designed to excite during faults to earth.
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.
EEI
Edison Electric Institute.
EERA
Electrical Equipment Representatives Association. EERA is an association of electrical manufacturers representatives. Additional information on EERA can be found at www.eera.org. Young & Company is a member of EERA.
EH2 rim
The specialized rim design that is used with some run-flat tires.
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.
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.
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.
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.
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.
electric servo motors
Also referred to as an electric actuator, a motor that provides movement to operate the air doors in an air box to control air temperature and air movement.
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.
Embedded Generation
Generation that is connected to a distribution system possibly at LV instead of HV.
EMTP
Electromagnetic Transients Program.
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.
Entrainment (Battery)
The process whereby gasses generated in the cell carry electrolyte through the vent cap.
EPDM
Ethylene Propylene Dione Monomer. 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.
EPROM
Electrically Programmable Read Only Memory.
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.
F
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.
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.
Field Current
The magnetizing current of a device such as a transformer. Also known as exciting current.
Flame Resistance
The ability of insulation or jacketing material to resist the support and conveyance of fire.
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.
Flash Hazard
A dangerous condition associated with the release of energy caused by an electric arc.
Flash Hazard Analysis
A study investigating a worker’s potential exposure to arc-flash energy, conducted for the purpose of injury prevention, the determination of safe work practices, and the appropriate levels of PPE.
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.
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.
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.
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.
Fused Cutout
A device, normally installed overhead, that is used to fuse a line or electrical apparatus.
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.
G
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.
Generator
A device that converts mechanical energy into electrical energy.
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.
GIS
Gas Insulated Switchgear (usually SF6).
GMT
Greenwich Mean Time.
Gnd
Ground.
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.
GTO
Gate Turn-off Thyristor.
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.
H
H
Henry.
Hard Drawn
Wire that has been drawn to its specific size and not annealed.
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.
Hazard Risk Category
Categories defined by NFPA 70E-2004 to explain protection levels needed when performing tasks. The values range from 1 to 4. ATPV rated PPE is required for categories 1 through 4 as follows: 1- 4 cal/cm²; 2- 8 cal/cm²; 3- 25 cal/cm²; 4- 40 cal/cm².
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.
Hertz
1) A unit of frequency equal to one cycle per second. 2) In alternating current, the changing of the negative and positive poles.
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 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.
Hookstick
An insulated stick, usually made of fiberglass, that is used to work energized overhead conductors and operate electrical equipment.
Horsepower
A unit of work. When used to show power usage, one horsepower is equivalent to 746 watts.
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).
H2
Hydrogen.
I
ICEA
Insulated Cable Engineers Association. ICEA is located at P.O. Box P, Southe Yarmouth, MA 02664.
ICT
Interposing Current Transformer (software implemented).
IEC
International Electrotechnical Commission.
IEEE
Institute of Electrical and Electronics Engineers. Pronounced “eye-triple-E”, this non-profit U.S. engineering organization develops, promotes, and reviews standards within the electronics, computer and electric power industries.
IESNA
Illuminating Engineering Society of North America. Founded in 1906, IESNA is the recognized technical authority on illumination.
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 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.
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
1) The property of a circuit in which a change in current induces an electro motive force. 2) Magnetic component of impedance.
Influence Quantity
A quantity which is not the subject of the measurement but which influences the value of the output signal for a constant value of the measurand.
Inrush Current
The initial surge of current experienced before the load resistance of impedance increases to its normal operating value.
Insolation
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.
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
1) A non-conductive material used on a conductor to separate conducting materials in a circuit. 2) The non-conductive material used in the manufacture of insulated cables.
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.
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.
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.
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.
ISM Band
The 2.4GHz frequency spectrum. ISM is actually synonymous with 2.4GHz, however it stands for Industrial, Scientific and Medical.
Isolation Link
A metal link used in series with a fusing device that melts and prevents refusing/re-enerization of a transformer.
Isotropic Antenna
A theoretical, ideal antenna having a signal range of 360 degrees. It is used as a baseline for measuring a real antenna’s strength signal, in dBi, where i represents Isotropic Antenna.
I.D.M.T.
Inverse Definite Minimum Time.
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.
J
Jake Fitting
A commonly used term for ascrew-in type connector or coupling for flexiblemetal conduit.
Jake Box
Old work switch box.
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.
Joist
Horizontal beams that extend from wallto wall and support the floor or ceiling –typically 2 in. x 10 in., 2 in. x 8 in. or 2 in. x 6 in.
Junction Box
an enclosure used forsplitting circuits into different branches. In ajunction box, wires connect only to each other,never to a switch, receptacle, or fixture.
K
kcmil
One thousand circular-mils.
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.
L
L
A symbol used to express inductance. The unit of measure is a “Henry”.
Ladder Diagram (LD)
One of the IEC 61131-3 programming languages.
Lag
The condition where the current is delayed in time with respect to the voltage in an ac circuit (for example, an inductive load).
Lateral Circuit
A tap-off line to take primary distribution from the main power line to a nearby load center.
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.
LCD
Liquid Crystal Display.
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 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.
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.
Limited Approach Boundary
A pump that transfers fuel from the fuel tank to the fuel injection system; also called a transfer pump or supply pump.
Limiting Value of the output current
The upper limit of the output current which cannot, by design be exceeded under any conditions.
Limit Switch
A protective device used to open or close electrical circuits when certain limits, such as temperature or pressure, are reached.
Line Hose
A rubber dielectric cover for conductor that is used to electrically isolate a worker from an energized conductor. Line hose is made by W.H. Salisbury & Company.
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. Loadbreak products are manufactured by T&B Elastimold.
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.
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.
Lux
The SI unit of luminance. One lux is one lumen per square meter.
LV
Low Voltage.
M
MAC address
Media Access Control address is a unique numeric identifier assigned to each device connected to an Ethernet network. It is used for data transmission and security functions.
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.
Mean-Sensing Transducer
A transducer which measures the mean or average value of the input waveform but which is adjusted to give an output corresponding to the r.m.s. value of the input when that input is sinusoidal.
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.
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.
Mid Point Sectioning Substation
A substation located at the electrical interface of two sections of electrified railway. It contains provision for the coupling of the sections electrically in the event of loss of supply to one section.
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.
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.
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.
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
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.
NEC
National Electrical Code (NFPA-70).
NEMA
An accrediting body for secondary and post-secondary automotive training programs; an independent, nonprofit organization under the umbrella of the ASE.
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 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.
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.
NFPA
The National Fire Protection Association.
NFPA 70E Standard
Standard that provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized.
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.
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.
Notching Relay
A relay which switches in response to a specific number of applied impulses.
NPS
Negative Phase Sequence.
O
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.
Omni directional Antenna
This is like a dipole antenna because it radiates its signal 360 degrees horizontally; however, its signal is flatter than a dipole’s allowing for higher gain.
One-Axis Tracking (Photovoltaic)
A system capable of rotating about one axis for tracking of the sun.
On Load Tap Changer
A tap changer that can be operated while the transformer is supplying load.
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.
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 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.
OPGW
Optical Ground Wire a ground wire that includes optical fibers to provide a communications link.
OSHA 29 CFR 1910, Subpart S-Electrical
Occupational Safety and Health Standards. Section 1910 Subpart S-Electrical Standard number 1910.333 specifically addresses Standards for Work Practices.
OSI 7-layer model
The Open System Interconnection 7-layer model is a model developed by ISO for modeling of a communications network.
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.
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.
P
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.
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.
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.
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.
PLC
Programmable Logic Controller. A specialized computer for implementing control sequences using software.
Plug Setting Multiple
A term used in conjunction with electromechanical relays, denoting the ratio of the fault current setting of the relay.
Point of Common Communication
The interface between an in-plant network containing embedded generation and the utility distribution network to which the in-plant network is connected.
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.
Polyethylene
A thermoplastic material composed of ethylene polymers. Polyethylene has excellent electrical and mechanical properties and is used an insulating material in cable.
Polyvinyl Chloride
Polyvinyl Chloride. PVC, a thermoplastic compound, is a commonly used Wire and Cable insulation and jacketing material.
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 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 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.
Prohibited Approach Boundary
An approach limit at a distance from an exposed live part within which work is considered the same as making contact with the live part.
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.
Q
Quick-Fit
Keyhole mounting system.
R
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.
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.
Real Power
The average value of the instantaneous product of volts and amps over a fixed period of time in an AC circuit.
Recombination (Battery)
State in which the hydrogen and oxygen gasses normally formed within the battery cell during charging are recombined to form water.
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.
Relay
A relay is an electrically operated switch.
Remote Control Point
The remote control point is a SCADA interface. Several RCP’s may be managed with connections are done at a gateway or at substation computers.
Resealable Cap (Battery)
A safety vent valve which is capable of closing after each pressure release from within a cell.
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.
Reversible Output Current
An output current which reverses polarity in response to a change of sign or direction of the measurand.
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.
RJ-11
Registered Jack 11. Standard telephone connector which has a tab that snaps into the socket and must be pressed to be removed from telephone or socket. Usually houses two wires but is capable of housing up to four.
RJ-45
Registered Jack 45. Connectors used to connect computers to LANs or phones with many lines. It is able to house up 8 wires that is twice as many wires as the RJ-11.
RMU
Ring Main Unit.
ROCOF
Rate of Change of Frequency.
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.
RTU
Remote Terminal Unit. An IED used specifically for interfacing between a computer and other devices. Sometimes may include control, monitoring, or storage functions.
S
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.
SCADA
Supervisory Control and Data Acquisition.
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.
SCP
Substation Control Point. HMI computers at substation level allowing the operators to control the substation.
SCS
Substation Control System.
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.
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 Entrance Cable
The conductors (electrical cable with multiple wires) that connect and carry the electrical current the service conductors (drop or lateral) above ground to the service equipment of the building. It can also be used as a panel feeder and in branch circuits.
Service Life (Battery)
The total period of useful life of a battery, normally expressed in the total number of Charge/Discharge cycles.
SEU
Service entrance cable.
SFC
Sequential Function Chart. One of the IEC 61131-3 programming languages.
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 abnorman connection of relatively low impedance, whether made intentionally or by accident, between two points of different potential.
Short Distribution (Lighting)
A luminary is classified as having a short light distribution when its max candlepower point falls between 1.0MH 2.25MH TRL. The maximum luminaire spacing-to-mounting height ratio is generally 4.5 or less.
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.
Simplex Communications System
A communications system in which data can only travel in one direction.
Single Element Transducer
A transducer having one measuring element.
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.
SOTF
Switch on to Fault (protection).
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.
Spring Winding Time
For spring-closed CB’s, the time for the spring to be fully charged after a closing operation.
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.
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.
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.
Stranded Conductor
A conductor made by twisting together a group of wire strands.
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 blocks are manufactured by Bethea.
Substation Configuration Language
Normalized configuration language for substation modeling as expected by IEC 61850-6.
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 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.
Switching Surges
A high voltage spike that occurs when current flowing in a highly inductive circuit, or a long transmission line, is suddenly interrupted.
Switch, Network
A Switch connects Client systems and servers together to create a network. It selects the path that the data packet will take to its destination by opening and closing an electrical circuit.
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.
S.I.R.
System Impedance Ratio.
T
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.
Tensile Strength
The greatest longitudinal force that a substance can bear without tearing apart or rupturing; also called ultimate tensile strength.
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.
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.
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.
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.
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.
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.
Twisted Pair
Telephone companies commonly run twisted pairs of cooper wires to each customer household. The pairs consist of two insulated cooper wires twisted into a spiral pattern. These wires are capable of transferring both voice as well as data.
U
UCA
Utility Communications Architecture.
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. Universal Bushing Wells are manufactured by the Elastimold Division of Thomas & Betts.
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.
USMA
Utility Supply Management Alliance, a utility industry conference held annually that is focused on the supplier/customer relationship.
V
V
Voltage; Volt.
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).
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.
Venting (Battery)
The release of gas from a cell, either controlled (through a vent) or accidental.
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.
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 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 Transducer
A transducer used for the measurement of a.c. 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.
VR Cable
AAC or ACSR with Vibration Resistant Twisted Pair Construction.
W
Watt
The standard unit of measure used for electric power.
Watt-Hour
1) A unit of work equal to the power of one watt operating for one hour. 2) 3600 Joules.
Wattmeter
The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit.
Waveform
A graphical representation of electrical cycles which shows the amount of variation in amplitude over some period of time.
Wire Lubricant
A chemical compound used to reduce pulling tension by lubricating a cable when pulled into a duct or conduit.
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
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.
XLPE
Cross-Linked Polyethylene. A thermo set plastic compound that is used for insulation of wire and cable.
Z
Z
Impedance.
Zero Crossing
The point at which a sinusoidal voltage or current waveform crosses the zero reference axis.