It's been a long time since I've logged on to this forum. I spent a lot time here back when I was working in the Electrical Contracting world. I'm currently working in a 600 MW Cogen Facility. We have a recurring problem with our 125 VDC station battery system. A ground on the positive bus will mysteriously appear, stick around for a while, and then vanish. It's a nuance more than anything. The trouble is that affects the secondary trip circuits for our Oil Filled Circuit Breakers, Gas Breakers, Breaker Failure Relays, Sudden Pressure Relays on our GSU's (Generator Step-Up Transformers), 86GT Lockout Relays, etc, etc, etc. So, systematically turning off breakers until I find the affected circuit is NOT an option. What I'm looking for may not exist. I'm looking for reading material on how to work on DC systems in industrial plants in hopes that I can develop a strategy to resolve this problem. Any help is appreciated.