ABB RELION 620 Series Technical Manual page 680

Section 8
Power quality measurement functions
8.2.5
8.2.6
674
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
N 2
∑
V
k = 2 k
THD =
V
1
GUID-EF4F9D27-6E81-4697-B02C-EDBBD68CE9A8 V1 EN
V
th
k harmonic component
k
V the voltage fundamental component amplitude
1
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.
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.
Signals
Table 512: PQVPH Input signals
Name Type
V_A_AB SIGNAL
V_B_BC SIGNAL
V_C_CA SIGNAL
BLOCK BOOLEAN
Default Description
0 Phase A voltage
0 Phase B voltage
0 Phase C voltage
0=False Block signal for all binary outputs
1MAC504801-IB E
(Equation 102)
620 series ANSI
Technical Manual