I was once working for a small company building electrical equipment. We mostly worked on "medium voltage" equipment, you know 2400 to 69000 VAC.
For one project we had large banks of ultracapacitor in a cabinet. Fully charged it was around 1200 VDC. This thing was in the prototyping stage, and we were testing a control system on a Saturday morning.
So we charge it using a large AC/DC converter, fully charged, everything worked beautifully. We start a discharge cycle converting the DC back to AC. Uh oh, it starts pulling way too much current. Flames start to shoot out of the AC/DC converter. Fuck. BANG. Fuse blown.
We assess the damage... the AC/DC unit is totally shot. And someone (me) is going to have to analyze what caused the failure. Otherwise everything with the capacitor cabinet seems okay, but the thing is still charged to 1090 VDC and the fuse is blown. Check with the mechanical engineer that designed the cabinet. Turns out the fuse can't be changed (can't be accessed) while the cabinet is charged and the cabinet can't be discharged because the fuse is blown. Well that isn't good.
The only thing we could do was discharge it into a load bank (think large toaster) by connecting something directly to the copper busbar live at 1090 VDC. So one of the commissioning guys volunteered. He put on some high voltage gloves, stood on a plastic mat, and connected some jumper cables someone had in their car to the bus bar. He stepped back and someone else threw the switch on the load bank and it discharged without incident.
You would think if you guys were working on those AC voltages, you'd have an arc flash suit on hand and he would have also put on an arc flash suit to do that.
For one project we had large banks of ultracapacitor in a cabinet. Fully charged it was around 1200 VDC. This thing was in the prototyping stage, and we were testing a control system on a Saturday morning.
So we charge it using a large AC/DC converter, fully charged, everything worked beautifully. We start a discharge cycle converting the DC back to AC. Uh oh, it starts pulling way too much current. Flames start to shoot out of the AC/DC converter. Fuck. BANG. Fuse blown.
We assess the damage... the AC/DC unit is totally shot. And someone (me) is going to have to analyze what caused the failure. Otherwise everything with the capacitor cabinet seems okay, but the thing is still charged to 1090 VDC and the fuse is blown. Check with the mechanical engineer that designed the cabinet. Turns out the fuse can't be changed (can't be accessed) while the cabinet is charged and the cabinet can't be discharged because the fuse is blown. Well that isn't good.
The only thing we could do was discharge it into a load bank (think large toaster) by connecting something directly to the copper busbar live at 1090 VDC. So one of the commissioning guys volunteered. He put on some high voltage gloves, stood on a plastic mat, and connected some jumper cables someone had in their car to the bus bar. He stepped back and someone else threw the switch on the load bank and it discharged without incident.
There were some design revisions after that.