Overhead ground wires(OHGW)

[woodye]

I have a 66-kV system where the OHGW for shielding is on a different structure than the phase conductors. This type of configuration is mentioned in IEEE std 1243-1997 section 8.3. The structures are both single steel poles. The poles will be grounded with less than 50 ohms resistance to ground. The soil in the are is very poor 3000 ohm-meters.

How should the two poles be connected?

I am concerned that if I bond the two directly together the ground potential rise, caused by a lighting strike on the OHGW, will cause my phase conductors to flashover.

But, if I don't bond them electricaly the touch potential, on the conductor pole, will be a problem.

 

[ItAintMe]

Bond them together. As long as the spans are not too long and the earthwire is continuous, and you do what you can to keep footing resistance low (eg deep rods - how is the soil deeper in the ground?), then the voltage rise at any pole shouldn't be too high and you shouldn't have too much trouble with flashovers. Provided you have proper insulation co-ordination and choose insulators with the right withstand voltage (see the standards).

It all depends on the risks you are facing - are there a lot of people regularly near the poles, so you want step potential kept low? or do you require higher reliability on a rural line? More questions than answers eh?

 

[tgott]

I agree with ItAintMe, bond them together. If the static were on the same structure you would rely on the proper insulators with the right withstand voltage to avoid phase flashover, so just approach it as if they are on the same structure.