ITE:EL has been tripping off due to HV sparks. Usually this also trips ITE:Q1/2. These are sitting in side-by-side racks.

The working theory is that HV sparks are returning to ground through the EL and quads, tripping them off. Possibly this is the result of a changed low impedance ground path. How this change happened could be either something we did during shutdown or the changes we made in TM3, no clear evidence yet.

The goal of these changes is to stop the EL and quads from tripping, assuming the sparks are travelling through the ground.

Possible routes through ground to the EL power supply:

1. Through controls. EL is controlled by a canbus card. Preliminary investigations by Mike Rowe make it look like the canbus reads the PSU max voltage (60kV), then the staton bit trips, then after a while of trying to talk to the power supply, the statdrv is turned off. It is not clear why the power supply is turning itself off, since it doesn't seem to have a trip or protection circuit inside. To be further investigated.
2. Through the AC ground.
3. Through the shield on the output voltage conductor that runs to the pit.
4. Through the EL wire and conductor itself.

Current attempts to mitigate the tripping:

• Add an isolation step to the AC power, in case it is coming through AC ground (option #2).
• Add ferrites on the controls lines (option #1, this was done earlier and no effect has been seen).
• Add transient voltage suppresors on the Vmon, Imon, Vprog and Iprog control cables (option #1).
• Replace grounding cable with a grounding strip where the grounding wire used to be on ITE:EL. The ground wire was a braid, so probably not too bad, so not sure if this will help.
• Improve the connection between the two grounding bars in the racks. The grounding bar for th EL supply is well connected to the copper ground strip from ITE, but only connected through a small cable to the grounding bar for the quads. A copper foil sheet was added between them and the previously used wire was disconnected on the quad side bar..