We had recently a blackout due to a Buchholz trip of a 132/6,3kV YNyn 18,75MVA due to a downstream phase to phase short-circuit.
I knew that occasionally Buchholz trip might be faster than phase protection relays; but only in case of an internal fault. In this case, there are 3 phase protection...
Synchronous motor 3800hp 6300V 259A 50hz 250rpm P.F.=1 brushless type. Exciter field=7.1Amps Exciter output =144.5V 135Amps. 2 different controlled rectifier bridges (for auto/hand PF control mode) feeding the exciter field.
The motor load is a reciprocating compressor. Suction and...
The trouble is on a Pennwalt rotating Vibro-screen with direct on-line 1,5Hp 380V 2,3Amps 50Hz 720rpm induction motor (no frequency converter).
http://files.engineering.com/getfile.aspx?folder=e712cc45-a251-4944-9baa-5f4252355198&file=R-00814_209703____1.1.pdf
The screen was working properly...
