All electrical installations and equipment comply with insulation resistance specifications so they can operate safely. Whether it involves the connection cables. IR Testing for Low voltage. Circuit voltage, Test voltage, IR Value(Min). Extra Low Voltage, V DC, MΩ. Up to V except for above. These minimum IR testing voltages must always be adhered to in order to accurately measure the Insulation Resistance in all electrical equipment. Any test .

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Three winding transformer 1. Where any equipment is disconnected for testing purposes, it must be subjected to its own insulation test, using a voltage which is not likely to result in damage. Premium Membership Premium membership gives you an access to specialized technical articles and extra premium content electrical guides and software.

Ronal Manuel Nov 09, Premium Membership Get i.r.testnig to premium electrical guides, technical articles and much more! Krishnaiah Oct 24, IR Value at Maintenance Time.

It was found that the reading was less with oil than without oil. Avoid meggering when the transformer is under vacuum.

Tech Power System Control ,B. For electric motorwe used a insulation tester to measure the resistance of motor winding with earthing E. O.r.testing and Low Voltage Installations- At a pressure of V applied between each live conductor and earth for a period of one minute, the insulation resistance of medium and low voltage installations shall be at least 1 Mega i.r.teting or as specified by the Bureau of Indian Standards] from time to time.


What should b d megger range n what is d value?? Its urgent, Plz help. Electrical engineering practitioners should always read and understand the appropriate guidance, incorrect information is misleading.

Measurement of insulation resistance (IR) – Part 2

Megger Value of HV 6. A meenashankar Jan 07, Voltage Rating Of Equipment.

The primary source of information is described within IEEE, IEC or national standards which must be reviewed before embarking upon electrical engineering works or projects. Qaisar Feb 02, IR Value for Substation Equipment 9. Sir,one 40MVA Transformer which was in service for 3 years. A little knowledge is dangerous. I think is tertiary winding. Dear Sir, I need to know the HV and Megger test voltage value and routine tests to be performed for medium voltage 6.

Thanks for your article.

For insulation testing, we need to disconnect from panel or equipment and keep them isolated from power supply. Tashi Tobgay Sep 16, Leave a Comment Click here to i.rt.esting reply. Sami Rashed Dec 29, Thank u so much sir….

Luckily after searching in the web your article showed up. In the case of a very large installation where there are many earth paths in parallel, the reading would be expected to be lower. Auto transformer two i.r.etsting 1. We need to test winding to winding and winding to ground E. For any installation, the insulation resistance measured shall not be less than: Apply the test voltage and note the reading.

Benefits of Permanently Installed Automatic Insulation Resistance (IR) Testing: Part 1 of 3

The example you stated mention some thing in contrary See Below. Value below which Insulation is not acceptable etc.


I.f.testing most dc armature and ac windings built after about form wound coils. I just have doubt that one of the examples of insulation temperature correction factors is given with a probable mistake from the point I looked to the insulator. An electrician performed Insulation Resistance test on Low Voltage cable between a Generator and switchboard.

Benefits of Permanently Installed Automatic Insulation Resistance (IR) Testing: Part 3 of 3

This current dissipates no energy and is not harmful, but we wish to measure the resistance of the insulation, so DC Voltage is used to prevent reactance from being included in the measurement. All LV surge diverter earth connections are to be disconnected during the test. Due i.r.tesring site constraints the cable could not be disconnected at both ends of the installation, however the circuit breakers were switched off at both ends leaving the neutral and earth connected.

Value at 60 seconds after application of the test voltage is referred to as the Insulation Resistance of the transformer at the test temperature. Guard the terminals to eliminate surface leakage over terminal bushings.

Samer Alamouri Jun 30, Dear Sir Thanks for all this good work that you have done.