Arc suppression device issues
Thread Content
Our company has encountered an arc suppression and harmonic elimination alarm in the PT cabinet for the primary power supply; it indicates arc grounding in phase B, and the arc suppression device activated to ground the metal of phase B. The secondary power supply system also activated its protection mechanism. Unit 1 could be reset, but Unit 2 couldn’t be reset under any circumstances. After about two hours, the protective fuse of Unit 2 blew, and the upstream substation informed that the ground fault had been resolved. During that time, a 700KW motor was started. After shutting down the motor, a 5000V megohmmeter was used to test the insulation of the motor and cables relative to ground, and the values were both above 200 MΩ. About an hour later, the motor was started again and operated normally. The voltage readings on Controller No. 1 are abnormal: Ua=60.17v, Ub=60.20v, Uc=60.27v, and U△=60.17v. On Panel No. 2, the voltage readings are Ua=60.18v, Ub=60.17v, Uc=60.17v, and U△=3.17v. The fault point cannot be located. Is the voltage of U△ for unit 1 at 60.17 normal? If it’s not normal, why is no alarm triggered?
Upon inspection by the device manufacturer, the abnormal voltage was caused by incorrect wiring of the harmonic suppression device. The blowing of the high-voltage current-limiting fuse is caused by a cable grounding fault in the upstream substation
It’s very valuable practical experience; I’ve learned from it, and in the future we’ll all pay attention to such issues. Thank you to the original poster for sharing this experience.