Answer / raghavendran

Tan Delta test is performed on transformers to test the
insulation strength of its Bushings,Oil,Winding - winding
insulation Strength.It is also called as dielectric
Dissipation factor.it is measured by applying Voltage across
the Insulation and the intensity of the charging current say
(Ic) and resistive current (Ir).the value of Ir should be
low and thus denoting that the insulation is good.

Answer / praveen

Tan Delta, also called Loss Angle or Dissipation Factor testing, is a diagnostic method of testing cables to determine the quality of the cable insulation.In a perfect capacitor, the voltage and current are phase shifted 90 degrees and the current through the insulation is capacitive. If there are impurities in the insulation the resistance of the insulation decreases, resulting in an increase in resistive current through the insulation. It is no longer a perfect capacitor. The current and voltage will no longer be shifted 90 degrees. It will be something less than 90 degrees. The extent to which the phase shift is less than 90 degrees is indicative of the level of insulation contamination, hence quality/reliability. This “Loss Angle” is measured and analyzed.

Answer / vinod

same

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