ABB Relion 620 Series - Application; Signals; Settings

U
k
k
th
harmonic component
U
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.
10.2.5 Application
VMHAI provides a method for monitoring the power quality by means of the voltage
waveform distortion. VMHAI provides a short-term three-second average and long-
term demand for THD.
10.2.6 Signals
Table 1036: VMHAI Input signals
Name Type Default Description
U_A_AB SIGNAL 0 Phase-to-earth volt-
age A or phase-to-
phase voltage AB
U_B_BC SIGNAL 0 Phase-to-earth volt-
age B or phase-to-
phase voltage BC
U_C_CA SIGNAL 0 Phase-to-earth volt-
age C or phase-to-
phase voltage CA
BLOCK BOOLEAN 0=False Block signal for all bi-
nary outputs
Table 1037: VMHAI Output signals
Name
Type Description
ALARM BOOLEAN Alarm signal for THD
10.2.7 Settings
1MRS757644 H
Power quality measurement functions
620 series
Technical Manual
1087