12,470 fuse (QA200) melting- Could capacitors cause problems?
12,470 fuse (QA200) melting- Could capacitors cause problems?
(OP)
About once a month a QA200 fuse clears on the utility riser at our plant. There has been no indication as to why it blows. We have a 2000 KVA 12470-> 480volt transformer. On the load (480v)side beyond the main CB there is a fixed bank of 400 KVar caps installed. We have had no indication of faults in the load side, and in fact, as soon as the fuse is replaced we can start up and run everything as normal. The Utility is at a loss to explain the problem. My question is "can the fixed caps be creating problems on the line side of the transformer causing the fuse to heat?"






RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
On the other hand, if your transformer is loaded close to rated and you have an additional harmonic load added to that, your fuse will perhaps overheat. But that harmonic has to come from the transformer primary and propagate through transformer to capacitors. And that is normally not possible - the 12,5 kV side is usually relatively free from harmonics.
Switching the secondary directly to the capacitor bank *could* be the reason for large peaks. But again, the capacitor bank is only 20 % of transformer - so that should not happen either.
I would put a transient recorder there (three voltages, three currents - and fast enough to sample at least every millisecond, faster is better. Then just sit and wait to see what the reason is.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
Putting on a recorder would be my first suggestion also, but you may want to look at the fuse and fuseholder with an IR camera to make sure there is no bad connection causing heat in the fuse.
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
Thanks all,
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
If this is a wye/delta transformer with the primary neutral connected, a fault elswhere on the system can blow a primary fuse. In this case here will be increased primary current and increased current in the delta, but the secondary monmitoring will not be "in the delta" and so will not see the secondary current.
My primary suspicion would be a hot connection on the energised side of the cutout. It may not be readily apparent visually. If not the first time, by the second or third time they replaced the fuse the linemen would have cleaned and inspected the removable fuse holder. The crossarm mounted hardware is more difficult to examine because it can not be approached closely, safely.
respectfully
RE: 12,470 fuse (QA200) melting- Could capacitors cause problems?
I would be looking for primary underground cable problems.