hi-pot on 20 miles transmission line

[JLuc]

Hi,

simple question: is it possible to do a hi-pot test on a 20 miles overhead transmission line (11.5 kV). What kind of problems could we run into due to the length of the wire to test. The line is off since 1 year and we need to test it before putting it back on.

Thank you.

JL

 

[rcw retired EE]

The line charging current will probalby trip your DC hipot test set on overcurrent. Above 30 kV, corona current will probably trip it if the leakage current doesn't.

You could do an AC hipot, but it will take a pretty hefty unit to keep the line charged.

Usual practice of the line contractors I have worked with (not that many) is a thorough visual inspection, then energize the line. Some would do a low voltage AC injection test on shorter lines just to prove there were no grounds still hanging.

 

[itsmoked]

Have you done a complete visual inspection?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

The surge arresters located on every transformer primary will prevent meaningful hi-pot testing unless all transformers are disconnected.

With a 20-mile line, I'd be concerned about hi-potting some things that don't like being hi-potted. I don't think a dc high-pot test is going to tell you much and I would doubt that you could actually do it with a normal test set.

 

[Marmite]

I agree with the other posts. I'm from a utility background and I've never known overhead lines be overvoltage tested, either when newly constructed, or when being recommissioned after an outage. The line really needs to be patrolled and a note made of all the defects, cracked insulators, broken stay wires, tree clearance issues, any working grounds left on etc which should be rectified before it is energised. Even if the line did successfully pass an overvoltage test that would not, in my view, discharge your obligations in terms of ensuring that it's safe to make live. Somebody could have built a house under it, or stolen a few spans of conductor. Do a patrol, fix the defects and preferably energise from a rated fault making device with autoreclosers disabled and sensitive earth fault proection enabled if fitted.
Regards
Marmite