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Capacitance & Tan Delta Test

Insulation Resistance

It is desirable to have Insulation Resistance as high as possible consistent with acceptable mechanical, chemical and heat resisting properties.

This test is to detect the conductive impurities or mechanical imperfections in the dielectric which affect the quality of insulation

The insulation resistance test can detect if this connection is loose. It can also detect whether there are other, undesired and inadvertent, grounds. If the intentional core ground is intact, the resultant resistance should be very low. To check for unintentional core grounds, remove the intentional ground and Megger between the core and the grounded transformer tank. This test should produce very high resistance indicating that an unintentional ground is not present. This test is to supplement DGA that shows generation of hot metal gases (methane, ethane, and ethylene) and to indicate if a spurious, unintentional core ground is the problem. Experience can help locate the source of the problem.

Polarization Index

Polarization Index test that it can provide an indication of insulation quality in ten minutes for very large equipment that might take very long time to get fully charged.

DC Absorption

DC Resistance

Leakage Current Test