Single phase voltage drop on a generator
Single phase voltage drop on a generator
(OP)
We have a small hydro with an 11kV/400V 500kVA Dy transformer. On the LV bus we have 30kW motor load (compressors). A 400V 300kVA (synchronous gen) hydro scheme synchs at 400V to this bus via motorised CB. The plant has been in operation for about three years. Just lately we have developed a fault where we get a neg sequence voltage trip after synch. We see three currents (about equal) and then one voltage on the generator drops from 230V to about 160V. Before synch, no problems, bus voltages also fine as measured when compressor loads are running, so no loss of HV fuse which would be an obvious solution. Generator windings and cables all tested low ohms so no large resistance in windings or cables. Unit synchs ok, and no neg seq at run up. Never seen this before and it has us stumped. Any suggestions out there. High resistance in CB contacts a possibility.... we have to strip the board to measure?






RE: Single phase voltage drop on a generator
Is your generator neutral grounded?
Have you meggered your generator windings for an intermittent fault? Do it immediately after a trip. Some faults are temperature related and only show up when the unit is at or near normal operating temperature.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single phase voltage drop on a generator
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single phase voltage drop on a generator
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Single phase voltage drop on a generator
RE: Single phase voltage drop on a generator
Bill
--------------------
"Why not the best?"
Jimmy Carter