PPA5xx/15xx user manual
12-1
12 Harmonic analyser
The HARM mode of the PPA5xx/15xx computes multiple
DFTs on the input waveforms in real time.
There are two modes of operation: difference THD, and
series harmonics. Series harmonic mode includes options
for THD, TIF, THF, TRD, TDD and phase. There is also an
option of a series harmonic bargraph display (PPA15xx
only) which shows both the voltage and current harmonics
simultaneously.
In difference THD mode, the THD (Total Harmonic
Distortion) is computed from the rms and fundamental:
THD = 1/h
1
√ ( rms
² -
h
1
²)
In series THD mode, the THD is computed from a series of
up to 50 harmonics.
i = n
THD = 1/h
1
√
h
i
² where h
i
is the i
th
harmonic
i = 2
TIF (Telephone Influence Factor) is similar to THD but each
harmonic has a weighting factor applied to reflect the
severity of the potential interference of that harmonic on
telephone communication.
i = n
TIF = 1/rms √
(h
i
x t
i
)²
i = 1
where h
i
is the i
th
harmonic
and t
i
is the i
th
weighting factor
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