This 2500 Switchboard has three sections; 1st section is the feeder section where the incoming Conductors attach to the buss via terminal blocks (90c or 75c). The 2nd section is the 2500 main breaker section fed horizontally by the 1st section, then to the 3rd section which feeds a few 300 amp breakers then vertically to a 2000 amp breaker which feeds the riser buss.
The FP&L vault is about 65' away, there where 8 PVC conduits with 500 MCMs feeding under ground to the 2500 amp Switchboard. The feeders failed just about at the PVC 90's leaving the FP&L Vault. This as you can imagine caused a horrific Arc fault sending a plasma ball 65' down line into switchboard via the magnetic pulse produced during the event. In the main electrical room which is about 25' x 40'. The blast blew out the steel double louvered doors, blew the glass out of a vehicle driving by, blew out all double drywalls in the electrical room and stair case nocking over people exiting through that area, launched a fire hose cabinet that was flush mount in the block wall, sent steam and smoke debris through out electrical room and portions of the parking garage. Yet, there was little damage done to the FP&L vault where the event took place compared to the damage sustained in the electrical room.
To make a long story semi-short, I brought in an electrical engineer, we had a field conversation which led to replacing the 500's with 7 parallel 400 MCM THHN with all components rated at 90c we calculated over 2660 amps and the city gave us a permit with these calculations. Why did we pull only 7 runs and not 8??? Because 1 run was burnt into the PVC conduit and could not be removed ( we even tried a 3/4 ton 4x4 pickup to pull it out)
Now the insurance company's engineer want proof that all components are rated at 90C to achieve the 2500 amp rating, the reason for my initial question. These engineers did a week long power study on the building we brought on line. The highest ampere recording was 365 amps across all three phases.
We did what was deemed a temporary repair to the building to get all tenants back in. The equipment took a heavy blow and we are in negotiations in replace the Switchboard. I did have a Eaton sales Engineer in to propose a replacement cost. The Westinghouse archives are not available to anyone.....
I will try to upload some pictures. Second thought, I'm going to have to edit (large file size) these to post them here.
Thanks, Chas.
