airport lighting problem

[dfsmith]

I have a runway lighting circuit that is currently inop.
It is powered by a 10kw 6.6a constant current power supply,which tests o.k.I have tested both output wires to ground and do have a high resistance path. I also have tested across the output wires at the CCR and have a very high restance path[32k ohms].I believe I have a damaged wire that is going to ground. My question are:
1- What are the most common reasons for series circuit failure.
2-What value resistance should I expect to see at the CCR end of the circuit. The wire length is approx 8k ft, and there are about 80 transformers in the loop.
3-Are there any "best way" troubleshooting techniques I should try.

One other factor to consider is the fact that almost all of the transformers are currently buried in 18 in of frozen New Hampshire ground and the current outside temp is -5F.
I do believe I have isolated the bad wire, but as yet havent jumped it out.
Iwould be greatful for any advice or guidence with this problem.
Thanks
Dave

 

[advidana]

the frozen ground will buckle and can break your wires or damage the lamp coils. you need to run your wires below the frost line.

 

[busbar]

It may be time to call in a specialized lighting-service firm. You are dealing with well over 1kV open circuit, and ‘600-volt’ tools and troubleshooting techniques do not mesh with that.

 

[jraef]

The old Hevi-Duty transformer type CCRs are now made by Flightlight. They may be able to offer some ideas as well.

http://www.flightlight.com/airportlighting/3.0.1/3.0.1.html

Quando Omni Flunkus Moritati

 

[Heydave]

What many people do not realize is that insulation wears out with time and voltage and is not "water proof". The usual causes of series failure are physical damage from humans, rodents, insects, ice, or ground movement. Water will corrode conductors when current flows through it and since insulation is not truley water proof, it will fail. Since the impedance is probably not very well controlled time domain relfectometry is out. Capacitence measurement may be used to get an idea of the distance to the fault but it sounds as if this environment my not be very good for it. Probably the best method is tone tracing with an "A" frame to track down the ground fault. Rebar and conduit will make even this method difficult.

 

[dfsmith]

Thanks for the helpful advice. The problem has been located and repaired. It ended up being a bad transformer in the series loop.A note of interest, the area around this fialed transformer got so hot that it turned a basketball sized area of snad and gravel around it to a solid chunk of something like glass. Goes to show you the power of high voltage! Thanks Again.