Megging long cable run

[Ken9876]

I have a 4/0 copper, tinned, rubber insulated messenger cable 4 wires total. Length is about 3700' are there any special considerations when meggering this, such as test time? Normal voltage is 277/480 on this system.

 

[Power Tech]

I have a 4/0 copper, tinned, rubber insulated messenger cable 4 wires total. Length is about 3700' are there any special considerations when meggering this, such as test time? Normal voltage is 277/480 on this system.

If you're using the Fluke? Push the button hold it down until it loads up. Hopefully loads up.

 

[zog]

I have a 4/0 copper, tinned, rubber insulated messenger cable 4 wires total. Length is about 3700' are there any special considerations when meggering this, such as test time? Normal voltage is 277/480 on this system.

60 seconds or until the reading stablizes. You better have a megger with some oomph, thats a long run.

 

[Ken9876]

60 seconds or until the reading stablizes. You better have a megger with some oomph, thats a long run.

What kind of oomph?, I have a small hand crack Greenlee or a hand held Fluke

 

[Doug S.]

Use the hand-crank, and bring an apprentice.

 

[Cow]

More like, use the hand crank and hook up a drill.

 

[zog]

What kind of oomph?, I have a small hand crack Greenlee or a hand held Fluke

Neither will be accurate, you need for 2 of the 3 currents to decay to get a real leakage current (Indicated in Megohms) value. The absorbsion currents and polarization currents will take a while to decay, that is a lot of domains to align. If it is on a spool you might as well just make up a number.

 

[Ken9876]

Neither will be accurate, you need for 2 of the 3 currents to decay to get a real leakage current (Indicated in Megohms) value. The absorbsion currents and polarization currents will take a while to decay, that is a lot of domains to align. If it is on a spool you might as well just make up a number.

No spool, it's been hanging in free air over salt water, under a bridge for 25 years. The cable can only be seen at two or three spots, and even then it's very hard to see clearly.

Thanks for the info.

Oh and since this is my idea to check it and no one else cares I'll be cranking.

 

[zog]

No spool, it's been hanging in free air over salt water, under a bridge for 25 years. The cable can only be seen at two or three spots, and even then it's very hard to see clearly.

Thanks for the info.

Oh and since this is my idea to check it and no one else cares I'll be cranking.

We care. Let us know what you find.

 

[ItsHot]

More like, use the hand crank and hook up a drill.

LOL !!:grin::grin:

 

[BJ Conner]

BJ Conner

BJ Conner

Cables are long capicators. just touching it to ground may not be enough. Charge can "bleed" out of the insulation for a time after it has been grounded. You can come back in 30 minutes or so and get zpped. How much and how long it will hold the charge vary.

 

[farmaped]

If I were acceptance testing a new 5kV cable, not too concerned about the IR result, just confirming it is OK to energize, is there a cable length that the Hi-Pot becomes somehwat useless?

 

[zog]

Cables are long capicators. just touching it to ground may not be enough. Charge can "bleed" out of the insulation for a time after it has been grounded. You can come back in 30 minutes or so and get zpped. How much and how long it will hold the charge vary.

4 times the test time is usually considered adequte in the testing world.

 

[zog]

If I were acceptance testing a new 5kV cable, not too concerned about the IR result, just confirming it is OK to energize, is there a cable length that the Hi-Pot becomes somehwat useless?

Nobody said anything about a hi-pot test, lets not get started on hi-potting cables.