Does anyone out there have any experience of the application of Vtm (Voltage-controlled time-multiplier) protection on a high Voltage distribution system?
I believe the system is based on overcurrent relays which are arranged to reduce their time multipler settings as the system Voltage falls...
Thanks, DEPU.
We do indeed employ a log time delay (several seconds) on the NVD relay in order to give time for other earth fault protection to operate.
I am more concerned with the application of a Voltage-measuring relay connected to a set of capacitor VTs. Some of our older sites have...
Perhaps I should attempt to clarify the situation:
The magnitude of neutral Voltage displacement we are looking to detect on the 33kV system is 5kV. (This is a nominal value, as the 33kV system is effectively unearthed once the source 33kV CB has opened.)
We use NVD protection to guard...
I work for a UK distribution network operator.
We fit Neutral Voltage Displacement protection on our 33/11kV delta-star transformers in order to detect and clear earth-faults backfed from the 11kV busbars.
Traditionally, the NVD protection signal has been derived from a star-connected set of...
