This old switchgear has been in use since 1920! It was powered off a high voltage transformer (Y-DELTA windings, 11,400V / 250V delta, ungrounded on the load side) across the driveway next to the building.
We received a service call Monday at 9am. about partial power loss at the complex.
Since we have performed service work there before and the complex has high voltage through out, the two "old farts" were dispatched to see what the problem was.
We arrived and met the maintenance electrician with the keys to the vault. We checked the high voltage meter on the outside of the vault and the phase indicators said that we lost "B" phase.
The customer phoned the POCO and they dispatched a crew.
Upon their arrival, we entered the vault. They checked the 25A 11,400V fuses and found "B" was blown.
Since there was no way to drop the load on the secondaries, (those knife switches were protected by a block wall located 21" directly in front of them)the POCO had to transfer other customers off of that grid to a temporary grid leaving this customer the only one live.
After 2 hours time, POCO returned. This time they brought 2 supervisors, two high votage crews and a transformer tech to test the transformer when it was down for the fuse replacement. The transformer has a date on it of 1908.
Because NO ONE of us present was willing to step in and throw those knife switches, even with hot gloves and a hot stick, the POCO had to drop the grid remotely via computer contol.
Once they did, the testing began. Since we could not effectively isolate the tramsformer secondaries, (because NO ONE was willing to throw the switches closed if we opened them now)the test was canceled after several inspections by us and the POCO crews.
The crew replaced the high voltage fuse. They ordered all of us back to a safe distance (duh!)and switched the transformer back on line via live cell phone person to person conversation and computer control downtown.
When the switch was made, the overhead service drop to the next building with the knife switches began to dance up and down and make a terrible noise. The cell phone conversation was "shut it down, shut it down, shut it down".
Houston, we have a problem.
Since there were 3 separate overhead drops to the building and only one of them was dancing, we cut the wires and taped them off.
The POCO then gave the command to re-energize the grid again. This time, no problem. Two out of the three were good.
As you look at the knife switches, the one on the top right was the one with the short.
Notice the sixth photo. There is a "U" shaped thingy bolted between the line side of the switch and the load side. Those are the "fusable links". They are made of a composit of copper and lead and have no rating markings on them. They still look fine!
Yesterday after installing a temporary service drop and reconnecting all of the loads you see in the photos, (23 wire splices) we reenergized the complex.
I am glad my company has taken the time and expence to train all of the field employees in the OSHA 30 Safety class. Not that we were dumb before that, but having the proper training and knowledge most likely saved a few lives durring this service call.
The complex has contracted with us to install two new 480V services to replace the old one here.
The way we originally got this client was through a service call back in the summer when one of their other high voltage swicthgear blew them of the grid and several other clients. Because of our professionalism and our unwillingness to compromise safety standards during this service call, they naturally called us first when they went down.
Yes, safety does pay. It's just like anything else of value, it takes an investment.
I will follow up with photos of the new switchgear.