**For an updated glossary, please visit our FAQ page.**

**Alternating Current** - current that reverses its direction of flow periodically (Hz).

**Ampere** - a unit of measure for the rate of current flow

**Apparent Power** - applied voltage multiplied by current in an AC circuit. This value would not take the power factor into account. Unit is volt amperes. (VA).

**Balanced Load** - AC power system using more than two wires, where the current and voltage are of equal value in each energized conductor.

**Bandwidth** - the range of frequencies over which an instrument provides accurate measurement

**Billing Consumption** - total amount of energy consumed during a predetermined period(usually 28-33 days).

**Consumption (active energy)** - actual electrical energy used measured in kilowatt hours (kWh) by the watt hour meter, regardless of the power factor.

**Crest Factor** - the ratio of the peak value of a wave form (voltage or current) to the RMS value.

**Current Transformer** - an instrument accessory which detects current flow without breaking

the circuit under test. An AC transformer, usually

step-down; typical ratio listing would be 1000:1. This would indicate 1000A on the primary and 1A on the secondary.

**Current Transformer Ratio** - the ratio of primary amperes divided by secondary amperes.

**Delta Connection** - a circuit formed by connecting three electrical devices in series to form

a closed loop; most often used in three-phase connections.

**Demand (active, real or true power)** - the power which is actually consumed by the load. The measurement takes the power factor into account.

**Derating Factor** - a number defined as 1.414 x average RMS phase current/peak phase current. This factor, when applied to the rated load of a transformer, gives an indication as to the percent loading that is reasonable when that transformer must service nonlinear loads.

**Displacement Power Factor** - the difference between apparent power and true power when only the phase relationship of voltage and current at the fundamental are taken into account.

**Distortion Factor (%DF)** - total harmonic Distortion referenced the total RMS signal (THD-R).

**Distortion Power Factor** - the difference between apparent power and true power frequencies.

**Frequency** - the number of complete cycles of AC voltage which occurs during one second (Hz).

**Harmonics** - current or voltages which have frequencies that are integer multiples of the fundamental power frequency; common and sometimes dangerous in nonlinear loads.

**Heating Effect** - temperature increase in electrical distribution equipment caused by an increase in RMS current.

**Impedance** - the total opposition to alternating current flow in an electrical circuit (Z).

**Inductive Reactance** - the force which acts as a resistance in an inductor to limit the flow of current. The force creates a leading power factor in AC circuits.

**Initiator Pulses** - electrical impulses generated from utility revenue meters. Each pulse indicates a specific number of watts consumed. These pulses are used within energy analyzers to measure energy consumption and demand.

**K Factor** - a number based on the harmonic content of load current that determines the maximum safe loading on a power source.

**K-Rated Transformers** - a transformer that is rated or designed to serve as the source for a predefined capacity of harmonic current.

**Peak Demand (maximum RMS power)** - the highest average load during a specified time interval (kW).

**Phase** - time relationship between current and voltage in AC circuits.

**Potential Transformer** - an instrument transformer used to step down high voltage potentials to lower levels acceptable for the input of electrical test instruments.

**Power Factor** - the ratio of true power (watts) to apparent power (volt amperes). Expressed in decimal form, e.g. .98.

**Ratchet Demand** - determining the billing demand based upon a pre-established peak average

demand (usually at 75%, 80% or 100% of the pre-established peak).

**Reactance** - the opposition to current flow in an AC circuit introduced through inductance or capacitance.

**Reactive Compensation Power** - the reactive power to be applied to an AC network for power factor correction; adding capacitance in order to bring the voltage and current waveform in phase.

**Reactive Power (kvar)** - power which is actually “borrowed” from the load and returned to the power source each cycle; unused power.

**Resolution** - the smallest unit value that an instrument can measure.

**Resonance** - when the inductance in the system and the natural capacitance of the system, or added capacitors, form a tuned circuit resonant at one or more of the harmonic frequencies produced by nonlinear loads.

**RS-232** - a computer interface connector used to connect serial devices such as instruments for information transfer.

**Sensitivity** - the smallest input that will provide a specified output.

**Skin Effect** - phenomenon in which high harmonic frequencies cause electrons to flow to the outer sides of a conductor, reducing its cross-sectional diameter, and hence its ampacity rating.

**Sliding Demand** - calculating average demand by averaging the average demand over several

successive time intervals, advancing one interval at a time.

**THD (%THD, Total Harmonic Distortion)** - the contribution of all harmonic frequency currents or voltages to the fundamental current or voltage, expressed as a percentage of the fundamental.

**THDF (Transformer Harmonic Derating Factor)** - method of calculating transformer derating established by CBEMA for phase-to-neutral loads.

**True RMS** - capability to accurately measure the value of AC voltage and current having a non sinusoidal waveform as well as sinusoidal wave forms.

**Unbalanced Load** - an AC power system using more than two wires where the current is not equal in the current-carrying wires due to an uneven loading of the phases.

**Watt** - the measure of real power. It is the power expended when one ampere of direct current flows through a resistance of one ohm.

**Wye Connection** - a connection of three components made in such a manner that one end of each component is connected; generally used to connect devices to a three-phase power system.

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