A3 Power Analysis; Power Quality - GE Power Quality Meter Series Instruction Manual

5.4 A3 POWER ANALYSIS

5.4 A3 POWER ANALYSIS
]] ACTUAL VALUES
]] A3 POWER ANALYSIS
MESSAGE
MESSAGE

] POWER QUALITY

] VALUES
5
Figure 5–17: ACTUAL VALUES PAGE 3 – POWER QUALITY VALUES
Ia / Ib / Ic CREST FACTOR: The crest factor describes how much the load current can vary from a pure sine
wave while maintaining the system's full rating. A completely linear load (pure sine wave) has a crest factor of
⁄
2 1 0.707 ( ), which is the ratio of the peak value of sine wave to its rms value. Typically, the crest factor can
range from 2 to 2.5.
Ia/Ib/Ic THDF: Transformer Harmonic Derating Factor (THDF), also known as CBEMA factor, is defined as the
crest factor of a pure sine wave (
where lower order harmonics are dominant. In a case where higher order harmonics are present, it may be
necessary to use a more precise method (K-factor) of calculating the derating factor. This method also does
not take into consideration the losses associated with rated eddy current in the transformer. The PQMPC soft-
ware provides the K-factor method of calculating the derating factor, which is defined on a per unit basis as fol-
lows:
h
max
∑
×
K I
=
h
h 1
=
where: I = rms current at harmonic h, in per unit of rated rms load current
h
5-24
MESSAGE
2 ) divided by the measured crest factor. This method is useful in cases
2
h
PQM Power Quality Meter
ACTUAL
]] ACTUAL VALUES
]] A4 PRODUCT INFO
Ia CREST FACTOR =
1.233
Ib CREST FACTOR =
1.008
Ic CREST FACTOR =
1.000
Ia THDF = 0.944
Ib THDF = 0.999
Ic THDF = 0.988
5 MONITORING
5.4.1 POWER QUALITY
GE Power Management