Previous in Forum: Two 110V Appliances in Series Running Off 230V?   Next in Forum: Earthing Gensets (Revisiting Thread �8929)
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
10 comments
Rate Comments: Nested
jamil_valuetech
Participant

Join Date: Aug 2011
Posts: 4

Megger Testing

08/04/2011 1:55 AM

Is it good to have Megger testing / Insulation testing done for a circuit, where we are using single core wires?

My earlier understanding is the Megger is mostly recommended for multi-core Cables, and not single wires running in PVC duct, can someone clarify?

Also I would like to know how it will be done in case of Wires? a friend showed me he used to do it by placing both testing leads copper of a multi-core Cable, run the Rotar until it reached 150/200 and then take readings. (he was using a really old fashion megger tester).

I on the other hand intend to do Insulation test for Single wires, if not MEGGER, please advise.

Regards.
Register to Reply
Pathfinder Tags: insulation megger
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
Tornado
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
Good Answers: 795
#1

Re: MEGGER TESTING

08/04/2011 2:03 AM

Megger™ testing is applicable to single conductors. After all, in testing a motor wiring vs frame or ground, you are testing a single conductor.

__________________
 In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Chook
Commentator

Join Date: Mar 2011
Location: off the beaten track, not quite whoop whoop nor humptydoo
Posts: 57
#2

Re: MEGGER TESTING

08/04/2011 2:07 AM

what are you testing? surely more than one length of cable...?

__________________
 Everything works out in the end, just not neccessarily how you want
Register to Reply
jamil_valuetech
Participant

Join Date: Aug 2011
Posts: 4
#3
In reply to #2

Re: MEGGER TESTING

08/04/2011 4:48 AM

The are providing complete Portable Cabin, camps.

this Means Cabins layed apart, and hooked up with the large Gen-set, with underground cabling.

Customer needs to test his cabins from the Electrical wiring, etc perspective.

As the cabins may consist of 1-phase equipment, such as Fridge, micro, computer, lights, AC, etc as well as 3-phase equipment such as Commercial Kitchen equipments, Laundry equipment, etc.

Mostly the internal wiring is done using single core wire ranging from 2.5mm² to 16mm², consisting of 3ph., Neutral & E.

To cover all possible risks, potential areas are to be inspected, this could start from checking Insulation of wires, continuity, resistance with 'Earth', etc.

Any else checks anyone can add? I would like to hear.

One of their client mentioned Meggering, thats what confused me the most.
Register to Reply
TonyS
Guru
United Kingdom - Member - New Member

Join Date: Aug 2010
Location: Resting under the Major Oak
Posts: 4347
Good Answers: 181
#4
In reply to #3

Re: MEGGER TESTING

08/04/2011 6:25 AM

All circuits should be tested to your local equivalent of BS7671:2008

__________________
 The reports of my death are greatly exaggerated.
Register to Reply
cuba_pete
Guru

Join Date: Dec 2010
Posts: 1895
Good Answers: 44
#5
In reply to #3

Re: MEGGER TESTING

08/04/2011 12:17 PM

One purpose of the megger is for insulation testing. The purpose of testing single lengths of cable is to verify the integrity of the insulation up to the rated value. This helps to insure ground faults are not part of your installation.

You could just install it all blindly and plug in a thumper and hope for the best.
Register to Reply
2
brich
Guru

Join Date: Oct 2009
Location: sometimes Wales,UK.. was Libya, now Oman!
Posts: 1715
Good Answers: 117
#6

Re: Megger Testing

08/05/2011 2:44 AM

In this particular case, taken as read, where you are where you are running single wires inside PVC duct it is ALWAYS good sense and should be standard practice to "megger" each circuit, that is between "live-netural-earth" of EVERY circuit, and between other circuits to ensure that there is no short or damage to the insulation of each conductor of each circuit to each conductor and between conductors of circuits to the conductors of the other circuits running in the ducting.

You must remember that a "Megger" (which is a trade name) is an "insulation tester", and will only test insulation. AS you are pulling in or running your single core cables, either one at a time or in bunches of three for each circuit, even in PVC, you can "nick or cut" the insulation, therefore you MUST test each core in each circuit and each circuit to the others.

What I would be looking for in short runs of cable, that is of less than 100 meters is almost "infinity", for the cabin circuit tested from the local fuse/breaker board. For the underground cable the same.

I would suggest that you first test for continuity with a "Fluke" to ensure that your circuits are OK, then using (even that very old "Megger") test between each conductor in that circuit using the "Mohm" scale on the "Megger".

After testing each separate circuit, then test between each circuit conductor, until all conductors are tested.

__________________
 The square root of nothing is what you make it!
Register to Reply Good Answer (Score 2)
No more Good Answers.
jamil_valuetech
Participant

Join Date: Aug 2011
Posts: 4
#9
In reply to #6

Re: Megger Testing

08/06/2011 5:04 AM

Thanks for the very detailed reply. I really appreciate and yes, is is very helpful.

I would be comfortable in a few clarification, which would be difficult explaining in plain text, I will make a sketch on Monday, hopefully, to confirm my understanding.

Thanks again...
Register to Reply
fixitorelse
Guru

Join Date: Aug 2010
Posts: 687
Good Answers: 21
#7

Re: Megger Testing

08/05/2011 8:09 AM

As Birch stated, but also make sure your mains are off at the breaker boxes before hitting them with the high voltages from megger.
Register to Reply
jamil_valuetech
Participant

Join Date: Aug 2011
Posts: 4
#10
In reply to #7

Re: Megger Testing

08/06/2011 5:06 AM

thanks,

what is better, to disconnect the E and N as well?
Register to Reply
Vinu_Answers
Commentator
Engineering Fields - Power Engineering - Power Engineering Passion Engineering Fields - Electrical Engineering - Engineering Passion India - Member - New Member

Join Date: Mar 2011
Location: Noida, (U.P.), India.
Posts: 99
Good Answers: 6
#8

Re: Megger Testing

08/06/2011 3:20 AM

During the manufacturing process non-uniformities may develop in the dielectric insulation either in the form of conductive impurities in the material or in the form of mechanical imperfections in the dielectric affecting the quality of the cable. Which may lead to cable failure in future. Insulation resistance / Meggar test helps in detecting these imperfections. So, test to be carried out on both single and multi-core cables.

Vinu_Answers Sure_Answers

__________________
 Sure Answers Always
Register to Reply
Register to Reply
Have a Different Question?
10 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

brich (1); Chook (1); cuba_pete (1); fixitorelse (1); jamil_valuetech (3); TonyS (1); Tornado (1); Vinu_Answers (1)

Previous in Forum: Two 110V Appliances in Series Running Off 230V?   Next in Forum: Earthing Gensets (Revisiting Thread �8929)

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (108 right now)
Show Members
Advertisement