The lubrication oil pumps of turbo generator bearing are fed by outgoing of an emergency panel in power plant as illustrated in below figure. The control circuit of mentioned AC panel is supplied by power station safe (of course not very safe) uninterruptable DC system. Due to an unknown reason, the DC power supply interrupts for a little time and restore after many seconded. This accident was the beginning of many interval problems in systems. After restore of dc supply, suddenly the incoming circuit breaker of emergency panel trips due to mal-function of relevant under voltage relay without any distortion of AC supply. This outage of ac supply in emergency panel caused a disastrous in power plant. When we lost ac supply of lubrication oil pumps, you can guess bad condition of turbine and generator bearings.
You can see three various schematic diagrams which could be used by protection system designers as following figures.
How can you choose the best wiring design for prevention of accident from below three submitted plans?