Distortion measurement
The distortion measurement module measures harmonics up to the 11th harmonic. The
total harmonic distortion THD for voltage is calculated from the measured harmonic
components with the formula
THD
V
V
k
N
k
=
=
∑
2
2
1
GUID-EF4F9D27-6E81-4697-B02C-EDBBD68CE9A8 V1 EN
(Equation 29)
V
k
k
th
harmonic component
V
1
the voltage fundamental component amplitude
Demand calculation
The demand value for THD is calculated separately for each phase. If any of the calculated
demand THD values is above the set alarm limit
THD alarm limit
, the
ALARM
output is
activated.
The demand calculation window is set with the
Demand interval
setting. It has seven
window lengths from "1 minute" to "180 minutes". The window type can be set with the
Demand window
setting. The available options are "Sliding" and "Non-sliding".
The activation of the
BLOCK
input blocks the
ALARM
output.
8.2.5
Application
PQVPH provides a method for monitoring the power quality by means of the voltage
waveform distortion. PQVPH provides a short-term three-second average and long-term
demand for THD.
8.2.6
Signals
Table 344:
PQVPH Input signals
Name
Type
Default
Description
V_A_AB
SIGNAL
0
Phase A voltage
V_B_BC
SIGNAL
0
Phase B voltage
V_C_CA
SIGNAL
0
Phase C voltage
BLOCK
BOOLEAN
0=False
Block signal for all binary outputs
Section 8
1MRS240050-IB C
Power quality measurement functions
418
REF615R
Technical Manual
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