#3/0 Cable Resistance Test..Fail or Pass

[ndwade]

Hello All,

I recently had a a set of #3/0 Cooling Tower feeders Megged for their resistance. Two of the feeders had meg ohm results in the 1500Mohm range - 2500Meg ohm range. The readings were corrected to 40 degrees and tested at 2000V.

One of the feeders (L3 or C phase) had a resistance reading of only 729Mohm @2000V. This is almost 50% less than the resistance for the other two feeders.

Should this cable be condemmed and considered to have failed the resistance test?

Also, what IEEE standard speaks to this resistance test for a #3/0 cable and what does it say...Fail or Pass?

Attached are the readings we took.

Any help would be much appreciated in determining if we need to replace this cable based on this information and some industry standards that are foreign to me.

Thanks

 

[DTR2011]

Need more information about the cables.

Voltage rating, insulation type. Are there any splices, accessories included?

 

[alehman]

The low resistance is certainly suspect. Whether that's enough to warrant replacement depends on the application. If a forced outage would be very expensive or inconvenient, you might consider replacing it. If it's not so critical, you could wait a while and check it again (or not).

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.