After a solenoid dropped into a sump and caused an electrical short, wiring in the PLC cubicle melted together causing major issues. The protection systems had not worked as designed, causing the damage to occur.
A BRS Engineer went to site during the next available shutdown to point-to-point the circuits to determine the source of the fault and possible methods to rectify the situation. Over the course of the 3 days on site it was determined that the cause of the fault was due to incorrectly isolated neutrals between MCC12 and MCC13, resulting in the protective equipment on both supplies to be bypassed. Errors and failures had periodically occurred on the PLC since the last PLC changeover in the early 2000’s, but the wires melting was the largest failure to date, leading to the investigation.