132
Power Quality Analyzer PowerPad
®
IV Model 8345
THD
Total harmonic distortion is the percentage of harmonics in a
signal, referred to the RMS value of the fundamental (%f) or to the
total RMS value without DC (%r)
U
Phase-to-phase voltage or voltage between phases
u
0
Voltage zero (or homopolar) sequence unbalance ratio
u
2
Voltage negative (or inverse) sequence unbalance ratio (neutral
connected) or phase-to-phase voltage (neutral disconnected)
U
1
= U
12
Phase-to-phase voltage between phases 1 and 2
U
2
= U
23
Phase-to-phase voltage between phases 2 and 3
U
3
= U
31
Phase-to-phase voltage between phases 3 and 1
U-h
Harmonics in phase-to-phase voltage
U
c
Declared supply voltage (normally Uc = U
N
)
U
cf
Crest factor of the phase-to-phase voltage (line voltage)
U
d
Distorting phase-to-phase RMS voltage
U
DC
Phase-to-phase DC voltage
U
din
Declared input voltage (U
din
= U
c
x transducer ratio)
Uh
Harmonic of the phase-to-phase voltage
U
pk+
Maximum peak phase-to-phase voltage
U
pk-
Minimum peak phase-to-phase voltage
U
N
Nominal network voltage
Declared
supply voltage
Declared input
voltage
U
N
U
din
U
c
Electrical
input signal
Input
signal to be
measured
Measurement
result
Check of the
measurement
Nominal
voltage of the
network
Electrical
network
Power supply
contract
Measurement
transformer
Measuring
instrument
Checking
instrument
Report
instrument
Networks that have a nominal voltage of 100 V < U
N
> 1000 V have standard
voltages of:
■
Phase-to-earth voltages: 120 V, 230 V, 347 V, 400 V
■
Phase-to-phase voltages: 208 V, 230 V, 240 V, 400 V, 480 V, 600 V,
690 V, 1000 V
Some countries have standard voltages of: