It could be Vibration. I had the same problem. Some breakers styles seem to be more prone to this then others. The ones I had were GE tri-pack MCB between 100 amps and 400 amps rated. Do you have any rotating equipment that could cause this.
Also, maybe the breaker is bad.
Your brushless exciter has diodes mounted internally that produce the DC current for the generator field. You should isloate these individually and test them. You may have one or two bad ones.
We use Protest but I was of the impresson that it was only used with the Doble equipment. I could be wrong. wont be the first time! I would be very interested if I am so please let me know.
The current unbalance is the result of the 2.8% voltage unbalance. The 25 HP motor you gave as an example will have 4 amps of Negative Sequence Current as a result. This current causes additional heating in the motor windings mostly around the end turns. Typically, motors are designed to...
We use the Doble test set and have found it very durable. This is important to use because we are always transporting it to the job site. Some of the other equipment we have had from Multi-Amp and Omnicron have been less dependable.
Also, whatever system you go with you should plan on it...
Depending on what the cable is installed in you may be able to locate the bad section of "A" Phase cable and repair it with a splice. It could have been damaged during pulling in. "B" and "C" phase megger readings are about what you would expect for good cable. How old is this cable? That...
I have personally experienced a similar situation. The end conclusion was that when a near by co-gen plant was experiencing some vibration problems with thier mechanical equipment it would create a resonant vibration in the breaker panels. We determined this by installing a vibration monitor...
I would have to agree with Busbar that installing an OLTC on an existing unit may not be practical. However, you do often see an auto transformer installed ahead of an existing transformer to regulate primary side voltage.
Cost considerations would probably be the major issue.
One of my customers who is a fairly large generating facility is have trouble with one phase of the LV side of his step up transformer (Showing hot with an IR scan).
This unit is under warranty so the manufacture is involved. We have performed several resistance tests of the connecting lead...
It is very common to have an ammeter in the same circuit as the protection device. It is usually not economically practical to have separate CT's for simple indicating meters.
I have never had a situation where an ammeter failed during a fault. If this is a concern then an ammeter selector...
I have had bad experiences testing older paper insulated lead jacketed cables in the past. I had one job where the customer's engineer insisted on a 3X DC hipot on all his 15+ yr old feeders. Needless to say several of them failed and cost him an extensive amount of money. Without hipot...
I work for a testing contractor so naturally my first response is "Do It ALL" because it's all good. However, since sometimes budgetary conserns out way what I personally would like to see done, Here is what I would consider the order of priority for tranformers over 3000 KVA...
