ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
Permit Snafus...AHJs and Contractors Jump in
by sparky. 04/28/17 08:11 PM
Electrode boilers question
by annemarie1. 04/27/17 01:40 PM
Why cables look like they do
by LongRunner. 04/26/17 09:36 AM
Dimmable LED 2x4 lay in fixtures
by HotLine1. 04/24/17 05:43 PM
Old decora style outlets
by Lostazhell. 04/22/17 07:59 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
234,898 Are you busy
169,704 Re: Forum
162,928 Need opinion
Who's Online Now
0 registered members (), 60 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#81416 - 08/12/02 02:48 PM Insulation Resistance  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
From Norm Koon:

I have a question concerning cables that are approximately 45 years old.

The insulation resistance test read as follows:

Air Temp 82 deg F
One Minute Megohm readings Ph A 1220 Ph B 2540 Ph C 484
Ten Minute Megohm readings Ph A 1470 Ph B 4100 Ph C 510
PI Index Ph A 1.11 Ph B 1.61 Ph C 1.05

Given this test data, would it be advisable to reuse these cables?

These cables are partly running underground, inside a basement and outdoors, so
an accurate temperature reading was not used. The temperature is only the outside
air temperature. Also they are still hooked up to the primary bushings of the transformer.

So they are not true readings of the cables. I was wondering if the disparity of the readings could be due to leakage on the transformer bushings. The test voltage was 2500 vdc. The system voltage is 6900 volts ac.


Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#81417 - 08/12/02 04:21 PM Re: Insulation Resistance  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
"...still hooked up to the primary" should make individual readings meaningless, unless I misinterpreted something.


#81418 - 08/12/02 04:34 PM Re: Insulation Resistance  
Bob  Offline
Member
Joined: Feb 2002
Posts: 182
Mobile, AL, USA
Norm
The 2500 volt DC test does not provide an adequate check of the insulation integrity.
Is the cable in use now? I would want to Hi Pot test the cable. New 15 kv cable is tested at about 60 kv but that is not what you want on cable this old. Check with the mfg annd see if they can give you a value to test the cable.



Member Spotlight
waymag
waymag
dallas, texas, USA
Posts: 67
Joined: January 2002
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.009s Queries: 14 (0.002s) Memory: 0.7519 MB (Peak: 0.8736 MB) Zlib enabled. Server Time: 2017-04-29 01:47:24 UTC