High resistance grounding of 240 Delta System

[ferguson]

240 volt Delta power is supplied to our plant through 2-750 Kva utility transformers. We recently had a ground on one phase through a small capacitor on a 240v 1-phase air conditioning motor. Somehow this caused voltage phase to ground to go as high as 560 volts intermittantly. I've been told that we can establish an "artificial neutral" by using zig-zag transformers in combination with resistors that will provide a ground reference and limit the phase to ground voltage. Are there vendors that supply a "one-box" solution? I'm not an EE so I can't engineer it myself. Any advice appreciated.
Steve Ferguson

 

[redtrumpet]

Check out

http://www.ipc-resistors.com.

Also all the big boys like GE, Cutler-Hammer, Square D, etc. can probably help you out. Also try searching this forum, I know this topic has been covered before.

 

[busbar]

Related discussion in threads 238-9005, 238-3370, 237-7403, 238-6870, 238-10998.

An example of high-resistance grounding is:

http://www.geindustrial.com/industrialsystems/switchgear/notes/GEI-72116.pdf

 

[BJC]

If you have a 3 wire open delta system I'm guessing the utiliy is splitting the output of one of the transformers and suppling the 120/240 system from it. It's very common practice.
If you don't have this kind of system then you should have a 240-240/120 volt single phase transformer that supplies the 120 for receptacles, lighting etc.
If you have a "wild leg" system the utility has grounded the center tap of one transformer. This is grounded conductor ( neutral) of you existing 120/240 volt system. It's a "wild leg" systems
and it cannot be converted to a high resistance grounded system by adding a resistor.