Medium voltage cable testing requirements

[jeff.monell]

I need some help on where to find the requirements for medium voltage cable testing. I am a generator field service technician for a major heavy equipment manufacturer and my company wants us to perform load bank witness testing on 2.5 Meg 13,200 VAC generators at our shop outside the service bays with no genset output breaker and untested cable. We will be connecting 15kv cable to the primary side of a transformer and 4/0welding cable from the secondary side of the transformer to a 3.3 Meg 480 VAC resistive/reactive load bank. I've always been taught medium voltage cable/connections should be hi-pot tested prior to energizing however I don't know where to find the requirements. I've looked in the NFPA 70E but it doesn't cover this application. The cable we use for testing is 15kv cable that has been transported, rolled, unrolled, walked on, driven on, and stored in the shop on a shelf somewhere. Makes me nervous, especially because it would be some of our junior shop personnel performing the testing. One of our other branches just does a visual cable check, makes the connections and does their testing. This makes it difficult because our branch gets the "well the other branch does it" conversation. The management will usually accept what I say and back me up on it but during the tough economic times, a few more bucks for outside vendor testing and rental of a medium voltage breaker raises eyebrows as we don't have the ability to perform hi-pot testing. I would just like the documentation to back up my testing recommendations. Any help would be greatly appreciated.

 

[zog]

I need some help on where to find the requirements for medium voltage cable testing. I am a generator field service technician for a major heavy equipment manufacturer and my company wants us to perform load bank witness testing on 2.5 Meg 13,200 VAC generators at our shop outside the service bays with no genset output breaker and untested cable. We will be connecting 15kv cable to the primary side of a transformer and 4/0welding cable from the secondary side of the transformer to a 3.3 Meg 480 VAC resistive/reactive load bank. I've always been taught medium voltage cable/connections should be hi-pot tested prior to energizing however I don't know where to find the requirements. I've looked in the NFPA 70E but it doesn't cover this application. The cable we use for testing is 15kv cable that has been transported, rolled, unrolled, walked on, driven on, and stored in the shop on a shelf somewhere. Makes me nervous, especially because it would be some of our junior shop personnel performing the testing. One of our other branches just does a visual cable check, makes the connections and does their testing. This makes it difficult because our branch gets the "well the other branch does it" conversation. The management will usually accept what I say and back me up on it but during the tough economic times, a few more bucks for outside vendor testing and rental of a medium voltage breaker raises eyebrows as we don't have the ability to perform hi-pot testing. I would just like the documentation to back up my testing recommendations. Any help would be greatly appreciated.

DC hi-pot testing is now considered a destructive test on service aged MV cables and should not be used. An AC-hipot test is good but depending on the length of the cable power frequency AC testing is usually not practical so a VLF AC test is typically used for dielectric strength testing. Even better condition assement tests ar Tan Delta and/or Partial Discharge.

ANSI/NETA MTS only allow for AC, VLF, TD, and PD tests on MV cable >5 years old.
IEEE std 400 (And std 576) Agrees as does the ICEA and IEC.

Now you have a different situation, as I understand this is a cable used for testing and I am guessing it is relativly short. And you are not concerned about condition assesment, just to see if the cable can be safely used.

If my assumptions are correct I would do a AC power frequency hipot test, or if it is a long cable a VLF test.

 

[zog]

Oh, and welcome to the forum.