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Arc Voltage - The reaction of a circuit's inductance to the rate of current change in the circuit; E = L(di/dt); when a current-limiting fuse operates, there is an associated arc voltage on the system.

Arrester Voltage Rating - RMS value of the maximum 60 Hz voltage to which an arrester should be subjected, even under transient conditions.

Breakdown Voltage - Voltage at which material fails.

Discharge Voltage - The voltage that appears across an arrester conducting surge current, expressed in terms of crest value of voltage that occurs during flow of surge current of a specified wave shape. The crest value of the discharge voltage for a standard 8 X 20 microsecond current wave should be less than the BIL of the protected equipment by suitable margin of protection of not less than 20%.

Dual Voltage Switch - A switch used to change the primary voltage of a transformer (refer to dual voltage transformer).

Dual Voltage Transformer - A transformer that consists of two separate windings which can be connected in series to handle a specified voltage and kVA, or in parallel to handle the same kVA at one half the series connected voltage. The voltage is changed by operating a dual voltage switch.

Duty-Cycle Voltage Rating - The designated maximum permissible voltage between terminals at which the arrester is designed to perform its duty cycle.

Extra-Low-Voltage - see definition for Voltage

Extra-Low-Voltage Power Circuit - A circuit, such as valve operator and similar circuits, that is neither a remote control circuit nor a signal circuit, but that operates at not more than 30V and that is supplied from a transformer or other device restricted in its rated output to 1000 VA and approved for the purpose, but in which the current is not limited in accordance with the requirements for a Class 2 circuit.

Fuse Maximum Operating Voltage - The maximum voltage that a fuse can properly operate at with assured clearing.

Gradient, Voltage - The voltage drop, or electrical difference, between two given points.

High-voltage - see definition for Voltage.

High Voltage and Low Voltage Windings - Terms used to distinguish the winding having the greater voltage rating from that having the lesser in two-winding transformers. The terminations on the high voltage windings are identified by H₁, H₂, etc., and on the low voltage by X₁, X₂, etc.

Low-Voltage - see definition for Voltage.

Low-Voltage Protection - A device that operates on the reduction or failure of voltage to cause and maintain the interruption of power to the main circuit.

Low-Voltage Release - A device that operates on the reduction or failure of voltage to cause interruption of power to the main circuit, but not to prevent its re-establishment on the return of voltage to a safe operating value.

Maximum Continuous Operating Voltage - MCOV - The maximum designated root-square (rms) value of power frequency voltage that may be applied continuously between the terminals of the arrester.

Overvoltage - A voltage above the normal rated voltage or the maximum operating voltage of a device or circuit. A direct test overvoltage is a voltage above the peak of the line alternating voltage.

Photovoltaic - see definition for Solar Photovoltaic Systems

Power-Frequency Withstand Voltage - A specified RMS test voltage at power frequency that will not cause a disruptive discharge.

Primary Voltage Rating - Designates the input circuit voltage for which the primary winding is designed.

Radio-Influence Voltage (RIV) - A high frequency voltage, generated by all sources of ionization current, that appears at the terminals of electric power apparatus or on power circuits.

Recovery Voltage - The voltage potential established across the open electrodes of an overcurrent protection device after clearing the circuit at a current zero; a term used to designate the voltage impressed by the circuit upon the interrupting device after interruption of the current at or about the time of a natural current zero.

Reference Voltage (Vref) - The lowest peak value independent of polarity of power frequency voltage, divided by the square root of 2, required to produce a resistive component of current equal to the reference current of the equipment or element, i.e., the reference voltage of a multi-unit arrester is the sum of the reference voltages of the series units. The voltage level shall be specified by the manufacturer.

Secondary Voltage Rating - Designates the load circuit voltage for which the secondary winding (winding on the output side) is designed.

Solar Photovoltaic Systems - The total components and subsystems that in combination convert solar energy into electrical energy suitable for connection to a utilization load.

Solar AC Module - A complete, environmentally protected assembly of interconnected solar cells, inverter, and other components designed to generate ac power.

Solar Array - A mechanical integrated assembly of modules or panels with a support structure and foundation, tracking, and other components as required, to form a power producing unit.

Interconnected Solar System - A solar photovoltaic system that operates in parallel with, and that may deliver power to, another system such as a supply authority system.

Solar Module - The smallest complete, environmentally protected assembly of interconnected solar cells.

Solar Panel - An assembly of modules, mechanically fastened together and prewired to form a self-contained unit.

Photovoltaic Output Circuit - Circuit conductors between the photovoltaic source circuit(s) and the power conditioning unit or direct-current utilization equipment.

Photovoltaic Power Source - An array or aggregate of arrays that generates direct-current power at system voltage and current.

Photovoltaic Source Circuit - Conductors between modules and from modules to the common connection point(s) of the direct-current system.

Power Conditioning Unit - Equipment that is used to change voltage level or waveform, or otherwise alter or regulate the output of a photovoltaic power source.

Power Conditioning Unit Output Circuit - Conductors between the power conditioning unit and the connection to the service, distribution, or utilization equipment.

Solar Cell - The basic photovoltaic device that generates electricity when exposed to light.

Stress, Voltage - A transient current of voltage usually associated with lighting or switching.

System Voltage - The RMS power frequency voltage from line-to-line as distinguished from the voltage from line-to-neutral.

Temporary Overvoltage (TOV) - A temporary overvoltage is define as an excursion of power frequency voltage above the normal line-to-ground value. Such excursions are of variable magnitude and duration.

Volt (V) - The unit of measure for voltage.

Volt-Amperes (VA) - The current flowing in a circuit multiplied by the voltage of that circuit. An expression of the output rating of a transformer.

Voltage - Electric pressure; the force which causes current to flow through an electrical conductor.

High Voltage - Any voltage above 750 V.

Low Voltage - Any voltage from 31 to 750 V inclusive.

Extra-Low-Voltage - Any voltage up to and including 30 V.

Step Voltage - The potential difference between two points on the earth's surface separated by a distance of one pace, assumed to be 1 m in the direction of maximum voltage gradient.

Touch Voltage - The potential difference between a grounded metal structure and a point on the earth's surface separated by a distance equal to normal maximum horizontal reach.

Voltage of a Circuit - The greatest root-mean-square (effective) voltage between any two conductors of the circuit concerned.

Voltage-to-Ground - The voltage between any given live ungrounded part and any grounded part in the case of grounded circuits, or the greatest voltage existing in the circuit in the case of ungrounded circuits.

Voltage Regulation - For a transformer, the change in secondary voltage which occurs when the load is reduced from rated value to zero, with the values of all other quantities remaining unchanged. The regulation may be expressed in percent (or per unit) on the basis of the rated secondary voltage at full load.

Voltage Regulator - An electrical device on an electric system that keeps voltage which is supplied to customers at a constant level, usually around 120 volts, regardless of load fluctuations.

Withstand Voltage - The highest value of applied voltage at which equipment will not flash over.