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Check the phase current logs at the same time the voltage rise was observed. If the current did not change then it is a voltage measurement fault.

Was the generator connected to a grid or load at the time. If so Could the over-voltage come from the load side, and not the generator ? However it would be very unusual for a Grid or load to only impact one phase. You mention 11kV as as the 1-phase voltage. What is the normal Line-to-Line...

Thanks. Happened In the Factory Test.

A bushing failed on a 50/60MVA 110/20kV ONAN/ONAF transformer during FAT yesterday. The failure occurred a few seconds into the high voltage 50Hz test after the transformer tank had been on pressure test for about 16 hours. The porcelain surrounding paper insulation on the inner side of the...

Thanks KJLRSA. Have calculated that LC resonant frequency is 177Hz, 197 Hz with 4 caps, 228 Hz with 3 caps, 279Hz with 2 caps. Do you think it will be OK if after reducing the number of capacitors the resonant frequency is not within 10Hz of a harmonic of 50Hz e.g. if it is not close to 200...

We have a 1000kVAR de-tuned 11kV PFC bank and want to de-rate it to 400kVAr. It consists of air cored reactors in series with five capacitors. It was not designed to correct for specific harmonics. Is there any reason why we cannot simply disconnect three of the capacitors?

That is what I am trying to find out. We did a project a number of years ago and this same issue came up, but with shorter cable. The generator supplier advised that the setup was just satisfactory. Nobody can now remember why this point was raised. The only thing I can speculate is that...

Designing a 10kV generator installation with about 300 meters between alternator and breaker. Concerns raised that cable length may be aproblem. Apart from burden on CT's which is OK are there any factors e.g. capacitances that limits cable length. Thanks.

Anybody can relate experience ( good or otherwise) with refined product radar tank gauging systems such as Endress & Hauser FMR5xx , Saab -Rosemount REX RTG3xxx. Thanks in anticipation.

You might consider what REF is going to achieve. I would say it has the possibility to reduce the extent of damage in the event of a fault. I have seen REF and DIFF faults that resulted in easy to repair damage. If it is a small tranformer say 1 or 2MVA then the replacement might be on more or...

Can you determine if the corrosion is from inside to outside or vice-versa. Hole corrosion generally exhibits a decreasing hole diameter from the surface on the side the corrosion is active. Cases I have seen appear as if somebody took a drill and drilled just to the the point of break-through...

I completed a 4 x 2MW centralised Standby that appears similar to your proposal. We choose LV gensets stepped up to 20kV because LV 2MW are more standard units. No great problems there. Big question is how to get this central system up and running on grid failure. Energising distribution...

No need to have a lightning down conductor. No need to have an air termination if the top of the tower is high enough to shield the uppermost antennae or they are a type that have integral lightning conductors. Connect the very bottom of the tower to the lightning ground e.g. where the...

We are installing an FM200 system. A customer's engineer raised a concern about having the FM200 bottles in the manned control room. He said he read somewhere that FM200 bottles should not be located in manned control rooms. We can't easily relocate except outdoors which I think is a bad...

No Code restriction that I am aware of. I have built a few plants this way. Apart from cost saving another advantage is that it solves a grounding issue - assuming you are using a YD traffo with the Y on the HV side the D winding would be unearthed and could float up to the HV potential unless...

I am not familiar with US standard voltages. I assume that 480V is line to line. Now if you step up to 480 Line to Neutral you can generally use the same rating switcgear and insulation as most equipment is rated at least 600V Line to Neutral. This would reduce the current to about 60% and...

In something similar I came across about 40% of the overcurrent trips on main LV breakers failed to trip. The breakers in question all tripped in response to manual operation. The trip coil mechanisms were seized or open circuit.

You may find that the serrated washer is a dissimilar metal to the brass gland and (possibly) steel box. As water can access the crevice you would have significant corrosion in a short time. I would focus first on getting a good weathertight seal by having a soft seal e.g. nylon washer between...

If you have symbols assocaited with the cpntacts you could use a symbols naming convention that indicates if the contact is Close to Trip or Open to Trip. e.g. I12.5 Overcurrent Trip (CTT), I12.6 Emergency Stop (OTT)

Thanks to all.