Title should have been week of grounds
Monday
Had a job testing distribution feeders for a new data center,
1st set of feeders was a 3-phase 4-wire 2000 amp feeder, 5-sets of 600-kcmil, DEAD short phase to phase, phase to ground I have never seen this on a new installation, so before contacting the contractor, I decided to triple check everything, I could not find any issues. Finally decided to involve the contractor, we isolated all feeders and conductors and rang everyone out. What had happened was the supply house set parallel feeders out, gray one end yellow other, brown one end orange the other, yellow one end brown the other, orange one end gray the other. This has been a high pressure job 80+ hours a week 35 guys during the week 50-70 on the weekend, fast track.
Anyway reconnected and everything megged fine.
Tuesday:
Went to a job to test a new service main with GFP protection, Megger, micro-ohm and test the GFP at all factory presets for current and timed operation at as found delay. The neutral was bonded to ground on the load side of the residual neutral CT, A NEC violation and will affect the GFP operation with possible Main trips under normal operation and desensitizing during fault conditions. I told the contractor they need to relocate this connection, they informed me the electrical inspector requires them to ground this way and they have done numerous services like this (Not to mention the other contractors in the same area). Now I'll need to contact the inspection department and make friends I guess.
Wednesday
Had a call to check a UPS that would not go to bypass when on generator, found the system input side distribution was a 3-phase 4-wire wire but all loads were distributed at 480 VAC 3-phase 3-wire, when on generator voltage was phase to phase A/B-480, B/C-480, C/A-480, phase to ground A-0, B-480, C-480. Obvious answer is ungrounded generator. Sure enough checked the generator and the neutral was not bonded, with no neutral to the building this was expected based upon the voltage. I isolated all the loads and megged the feeders A-10,000 ohms, B-540 meg-ohms, C-612 meg-ohms. Long conduit runs and a pain to repull, decided to open all J-boxes to look for possible ground connection. I Found a split bolt connector on A phase shorted to ground, and evidence of past fault at this location, which most likely is from a B or C phase fault downstream at some point.
This is a very tight 12x12 trough, I will put a 36x36x12 extension on the box and install Polaris taps.
Not sure what Thursday has instore but one thing for sure I will not look at any ground connections.
