35kV Wind Farm NGR design

[JBUDA54]

My background is Industrial so I am coming into this arena with little to no Utility experience. I am working on a design tie a 12 ohm NGR to a wye delta grounding XFMR (The Fault current of the NGR is 1658A for 10sec.) The L-L voltage is 34.5kV. During a fault the NGR can see as much as 20kV at its terminals. During normal non-faulted conditions the resistor can handle 75A continuously at 385 deg C. I believe I should have the GF Relay trip the power source at 50A if the CT detects 5A. I am putting a metal chain link fence around the resistors and grounding XFMR. I am trying to determine what fence spacing I need to maintain for the NGR's. If I look at NEC 110.31 Voltages from 600-13.8kV require 5' (Or do I use the 20kV line item of 9' in the event that a fault occurs?). This fenced area will have signage to keep out people while the line is energized. We are putting these components into a footprint and would like to keep our boumndaries to a minimum. Is there a utility code for NGR fenced areas? If not do I use NEC 110.31? I am lookikng for some guidance towards codes or standards that address this particular design.

 

[Marmite]

Under normal safety in design principles which apply regardless of your jurisdiction, it is much better to eliminate the hazard rather than control it. Why not use a metal clad resistor with a cable box? These things are cheap, and you can eliminate the hazard of exposed connections.
Regards
Marmite

 

[JBUDA54]

I came into the project late and I don't believe we have the ability to change the PO without schedule and cost implications. I agree with your proposal and this will be my approach going forward! I have learned that the NESC is the code for substations and that the 10' from live parts to fencing has to be maintained.

 

[bacon4life]

The NESC 10.6 foot value applies to the substation perimeter fencing and is based on excluding intruders and unqualified personnel. If this is simply a supplemental barrier inside of the substation to guard live parts from qualified workers, section 124.c.3 would apply. When we use this type of setup around capacitor banks, the gate is kirk key interlocked with the disconnecting means. Also note the height requirement of 7 feet versus 3.5 feet.