electod66
New member
I would like some help with a recent event,
We have a radial fed 13.8kv system fed from 2 sources to a main Tie Tie Main system, we had a 1/2 amp fuse of 3 on a PT providing power to metering on main 1 open but started failing and causing asserting and de-asserting of protection 4 days prior to the event, we were called out for loss of power to our 4160 volt service fed from the 13.8kv system thru a transformer, this service has 2 5000 hp synch motors and 2 1250 charge pump motors that were all operating at the time of the event. upon arrival we found the M1 main open but service still available from the provider, the tie was closed but we had no 4160 volt power, we had an under-voltage relay at the 4160 volt switchgear tripped and the 86 LO relay rolled, we could not reset the under-voltage relay, thought was it was failed because the double barrel 300 amp 13.8kv fuses did not show to be blown or open upon first inspection, testing was completed with the relay bypassed and 2 phases were identified as having no power, upon further investigation dressed out in arc flash gear rated for the incident energy, two double barrel fuses of the 3 sets were found blown. We noticed that there was obvious voltage anomalies on the feeder protection relay from the source feeder so we requested from the provided to de-energize the feeder so we could safely pull the PT drawer there was no obvious blown fuse so we proceeded to remove them to test them when it was noticed that the center fuse was warm in the center of the fuse but indicator was not protruding to indicate a blown fuse that's when we identified that the center fuse was open.
we are now investigating the cause of the transfer from the main without the loss of power from the provider and no identified faults on any of the systems.
our theory is that for some reason the failing fuse initiated a transfer that should have been blocked by the Under-voltage relay protection until the bus voltage had depleted to a safe tie close range (25%)
apparently that did not happen and the tie closed with enough voltage still present to keep the motor from shutting down and attempting to run causing a failure of the 13.8vk fuses.
any theories would be greatly appreciatted
We have a radial fed 13.8kv system fed from 2 sources to a main Tie Tie Main system, we had a 1/2 amp fuse of 3 on a PT providing power to metering on main 1 open but started failing and causing asserting and de-asserting of protection 4 days prior to the event, we were called out for loss of power to our 4160 volt service fed from the 13.8kv system thru a transformer, this service has 2 5000 hp synch motors and 2 1250 charge pump motors that were all operating at the time of the event. upon arrival we found the M1 main open but service still available from the provider, the tie was closed but we had no 4160 volt power, we had an under-voltage relay at the 4160 volt switchgear tripped and the 86 LO relay rolled, we could not reset the under-voltage relay, thought was it was failed because the double barrel 300 amp 13.8kv fuses did not show to be blown or open upon first inspection, testing was completed with the relay bypassed and 2 phases were identified as having no power, upon further investigation dressed out in arc flash gear rated for the incident energy, two double barrel fuses of the 3 sets were found blown. We noticed that there was obvious voltage anomalies on the feeder protection relay from the source feeder so we requested from the provided to de-energize the feeder so we could safely pull the PT drawer there was no obvious blown fuse so we proceeded to remove them to test them when it was noticed that the center fuse was warm in the center of the fuse but indicator was not protruding to indicate a blown fuse that's when we identified that the center fuse was open.
we are now investigating the cause of the transfer from the main without the loss of power from the provider and no identified faults on any of the systems.
our theory is that for some reason the failing fuse initiated a transfer that should have been blocked by the Under-voltage relay protection until the bus voltage had depleted to a safe tie close range (25%)
apparently that did not happen and the tie closed with enough voltage still present to keep the motor from shutting down and attempting to run causing a failure of the 13.8vk fuses.
any theories would be greatly appreciatted
