Measurement Computing WavePort 312P rev.1.0 - Manual (Page 80)

Glossary
11-4 Glossary PowerVista/312 User’s Manual
Resonance
A condition where elements of a circuit match impedance to form a total high impedance that resists current
flow at a given frequency, causes amplification of injected harmonic currents, and typically results in above
normal voltage distortion.
Sag
A sag is a short duration (0.5 to 60 cycles) reduction in RMS voltage caused by a fault on a portion of the power
system, or the energizing of large loads (i.e. induction motors). A sag will dip in voltage and then return without
interruption.
Swell
A swell is a short duration (0.5 to 60 cycles) increase in RMS voltage caused by sudden decrease in load or
other power system events. A swell will increase in voltage and then return without interruption.
Short-Circuit Ratio
The ratio of the symmetrical short-circuit current a selected point (typically the Point of Common Coupling
(PCC)), to the total plant or bus load current.
Telephone Influence Factor (TIF)
For a voltage or current wave in an electric supply circuit, the ratio of the square root of the sum of the squares
of the weighted root-mean-square values of all the sine-wave components (including alternating current waves
both fundamental and harmonic) to the root-mean-square value (unweighted) of the entire wave.
Telephone Interference
Interference on telephone circuits caused by magnetic and/or electrostatic (capacitive) coupling of a telephone
circuit with a power distribution circuit.
Total Demand Distortion (TDD)
The total root-sum-square harmonic current distortion, in percent of the maximum demand load current (15 or
30 min demand). Harmonic currents in amps are divided by a specified maximum demand load current before
processing via root-sum-square.