Failure of Buchloz Relay

Sorry, we can't solve your problem for you - only YOU can do that. But we can give you some suggestions what to do:

1. Hire a reputable electrical testing contractor who knows transformers, relays, and HV testing to test the 50MVA transformer and its relay to determine if it is the transformer that has an internal fault or internal gas generation (that's what the Buchholz is designed to detect), or if the relay or some other component in the breaker's tripping scheme is falsely operating.

2. Take steps to reduce the frequency of your severe (I assume that is what you meant) earth faults, such as increased clearing of vegetation near overhead lines, larger insulators and/or guards to prevent animal contacts, better maintenance to clean off contamination that could cause tracking or flashover, etc.

3. Get your facility on a regular program of electrical testing and maintenance to head off (many) problems before they occur.