Power & Energy Terms Glossary
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)
Is total power flowing
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
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
This measurement takes the power factor into account
Derating Factor: a number defined as 1.414x average RMS phase current/peak phase current
When applied to the rated load of a transformer, this factor 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 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 (ex: .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
Also described as 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
Also known as 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, formed a tuned circuit resonant at one of 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