Megging long cable run

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Ken9876

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Jersey Shore
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.
 
Ken9876 said:
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.
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If you're using the Fluke? Push the button hold it down until it loads up. Hopefully loads up.
 
Ken9876 said:
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.
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60 seconds or until the reading stablizes. You better have a megger with some oomph, thats a long run.
 
Ken9876 said:
What kind of oomph?, I have a small hand crack Greenlee or a hand held Fluke
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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.
 
zog said:
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.
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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.
 
Ken9876 said:
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.
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We care. Let us know what you find.
 
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.
 
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?
 
BJ Conner said:
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.
Click to expand...

4 times the test time is usually considered adequte in the testing world.
 
farmaped said:
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?
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Nobody said anything about a hi-pot test, lets not get started on hi-potting cables.
 
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