Aurelia and I investigated this current limit issue May 8th. First, By separating TM3 from TCS. we found the problem is on TCS side. We did a Megga test on TM3 as well. TM3 is good at 1KV megga test. After that, The insulators between TCS to ground is test. they are good which could hold 1G ohm at 1000V megga test. So the problem should be on power supply side  including power supply itself ,cables and transformer. Later, Tom and John found the TCS bias HV cable from power supply to HV chase top in faraday cage is broken down. It can not hold 5KV on HV test now. This cable should hold 100KV. But not this time. Tom also found  the adapter on Faraday cage could be designed in a better way. The broken cable was removed yesterday. John and Tom will order an exactly same cable from Glassmen.