4160 Volts System . From Transformer to Resistor must Cable must be insulated for system voltage (4160 ). 250.186 (B) 2011 NEC. Question from load side of Resistor to ground. Insulated & rated for 4160 also???? Please state code section. Yoopersup
13.8 Primary 4160 Secondary. Resistor added in Field (Not Factory) done all the time. From XO on Transformer Wire insulated for 4160 to Resistor. They have From Load of resistor to Ground bare copper. I feel per 250.186 (B) it must be 4160 insulated to Ground even after resistor . Because its a Neutral going to ground. 250.186 (C). It doesn't Change from a Neutral just because it goes thur a resister. Yes it then feeds switchgear which feeds 2 large motor loads. Its on the riser I sent you some time back. I called the Manufacturer of the Resistor Gard & he said he'd get back to me.
Talked to Four Electrical Engineers on this. Answers all over the place. Two said bare ground wire off resistor to ground OK One said 600 Volt insulated to ground. One said 4160 volt (Same as Phase conductors to Ground ) I Personality think 600 volt insulated from load side of resistor to ground be fine. Any comments ?? This is an Impedance Grounded System per 250.186 NEC. Becoming more common in Industrial & Mining.
It sounds like a Grounding Electrode Conductor to me. This is not intended to carry the unbalanced circuit current (neutral) it is just establishing a ground reference for the separately derived service.
250.186 Calls it a Neutral & says it must be insulated at least up to the resister same as Phase conductors .(250.186 (B)& (C). I also talked to the Manufacturer (Gard) & he agreeded up to the Resister it MUST be insulated same voltage as Phase conductors. It's after the Resister I get mixed info.
From XO to the resistor I agree, any voltage drop across the resistor will show up on this conductor but on the grounded side, it should stay ground. You also have the issue with a bare wire on the XO side being unintentionally grounded and shunting out the resistor. (defeating the purpose). It makes perfect sense to insulate that conductor.