6 VOLTAGE TRANSFORMER SUPERVISION
The Voltage Transformer Supervision (VTS) function detects failure of the AC voltage inputs to the IED. If
the IED misinterprets this as a failure of the actual phase voltages on the power system, it could result in
unecessary tripping of a circuit breaker. To prevent this, the VTS detects voltage input failures which are not
caused by a failure of the power system phase voltage.
The MiCOM P747 does this by looking at each zone. For each zone, if VTS detects a differential current and
a voltage drop, it blocks the VT for that zone. This prevents the busbar differential element from signalling a
fault for that zone and tripping a circuit breaker.
Ordinal Signal Name Source Type Response
Description
1080 VT Chk Block Z1 Software VT Check Protection event
This DDB signal indicates that the VT supervision blocks tripping of the busbar differential element for Zone 1
1081 VT Chk Block Z2 Software VT Check Protection event
This DDB signal indicates that the VT supervision blocks tripping of the busbar differential element for Zone 2
1082 VT Chk Block Z3 Software VT Check Protection event
This DDB signal indicates that the VT supervision blocks tripping of the busbar differential element for Zone 3
1083 VT Chk Block Z4 Software VT Check Protection event
This DDB signal indicates that the VT supervision blocks tripping of the busbar differential element for Zone 4
MiCOM P747 Chapter 6 - Monitoring and Control
P747-TM-EN-1 187
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