NEC 250.36 Equpment Bonding Jumper

philly

Senior Member
If a High Impedance Ground resistor is installed at the secondary of wye transformer winding I understand the requirement of 250.36 (E) & (G) to install an Equpment bonding jumper between the grounded side of the resistor and the downstream disconnect sized per 250.66 or 25.0.36 depending on where the GEC is located (at resistor vs downstream disconnect means).

For an MV system (5kV, or 15kV) does this equipment bonding jumper need to be a fully insulated cable or does it only need to be rated for 600V? Based on its location on the grounded side of the resistor I believe it only needs to be rated for 600V?

Also with this being a separately derived system, are the secondary conductors between transformer secondary and downstream disconnecting means required to still have a supply side bonding jumper (SSBJ) per 250.30 or an ECG per 250.122, or is the bonding jumper in 250.36 for this application intended to take the place of this for return path for fault current?
 

ron

Senior Member
For a review of the terminology used (for me mostly), here is a graphic I swiped from a website for 480 - 1000V.

Are you asking about what is described in 250.187(D) Equipment Grounding Conductors for >1000V?
Equipment grounding conductors shall be permitted to be bare and shall be electrically connected to the ground bus and grounding electrode conductor.
1683994441648.png

This graphic is from 250.187, also from that helpful website
1683994938936.png
 
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