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Join Date: Sep 2013
Posts: 31

Comparison Of Surge Comparison, Polarisation Index and Tan Delta Tests

03/22/2017 8:59 AM

Dear sir,

Kindly distinguish how to use PI test results and Tan Delta tests.Both are dealing with insulation value only.Which test should be used at what time?How to decide to go for Tan Delta test or PI test? How to interpretate surge comparison test? Which test is superior?TanDelta test or PI test.If we are doing these tests,then,what is the requirement for IR test and HV test? Kindly explain.

Regards,

NVRSrinivas

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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
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#1

Re: Comparison Of Surge Comparison, Polarisation Index And Tan Delta Tests

03/22/2017 10:45 AM

Why does the organisation not know why the tests being advocated are being carried out (rhetorical question - NNTR)? As mentioned in the duplicate thread on this topic, there is absolutely no point in carrying out any of these tests if the protocol needed to carry out the test and establish where the pass/fail boundary lies has not been established beforehand!

There is no point in asking the forum to guess what the organisation's criteria actually are.

If the organisation has no criteria, then it needs to subcontract-out the testing to an organisation that does, like the motor manufacturer as one possibility or a local independent testing house as a second. CR4 is not is not in a position to do this. Obviously.

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Join Date: May 2010
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#2

Re: Comparison Of Surge Comparison, Polarisation Index and Tan Delta Tests

03/22/2017 3:21 PM

In addition to PWS's comments about the requirements, specifications, and criteria for the tests, you must also understand what these tests are intended to measure.

Insulation resistance (and associated Polarization Index calculation PI) is a DC test of insulation. It stresses the insulation to determine its capability to "hold" at values approaching what would be peak of AC voltage. It can be a destructive test for insulation, with the intent that if there is a weakness in the insulation, it will fail.

Tan delta is an AC test at voltages that can approach the nominal operating voltage. It can measure aspects of the insulation quality that the DC tests cannot, as well as pointing to some possible causes of the problem. Tan delta (and the similar Doble Insulation Power Factor test) treats the insulation system as a set of linked capacitors, and looks at their interaction when energized through leakage currents and power losses.

Surge test is just what it says - a test to determine whether the insulation will withstand a voltage surge.

If you want to understand where and how these tests are applied, you would do well to purchase yourself a copy of the InterNational Electrical Testing Association's (NETA) Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems and The ANSI/NETA Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems. They are very instructive resources. You can find them at the NETA web site:

http://www.netaworld.org/standards

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
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#3

Re: Comparison Of Surge Comparison, Polarisation Index and Tan Delta Tests

03/23/2017 4:53 AM

A test without a pass/fail boundary is just a measurement.

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