1. TAN DELTA TEST FOR POWER TRANSFORMERS

2. TAN DELTA(INSULATION DISSIPATION FACTOR)
Tan delta is the insulation power factor & is equal to the ratio of power dissipated in the insulation in watts to the product of effective voltage & current in volt ampere when tested under sinusoidal voltage.

3. PROCEDURE All windings immersed in insulating liquid.
All windings shortcircuited using bare braided jumper such that jumper shall not be allowed to sag.
All bushings in place.
Temperature of winding & insulation liquid near to the reference temperature(27 degree).
All bushings cleaned properly.
Transformer earthed properly.

4. Neutral,star point of 3 phase winding connected to other bushing of that winding by means of short jumper.
Tan delta is then tested between below combinations,
a. HV to EARTH
b. LV to EARTH
c. HV to LV.

5. TEST SETUP TRANSFORMER SPECIFICATONS RATING-100 MVA
VOLTAGE CLASS-33KV/220KV
Yyn-0
COOLING-OFAF
INSTRUMENT MAKE-OMICRON
APPLIED VOLTAGE-10KV

6. LV TO EARTH TESTING

7. HV TO EARTH TESTING

8. LV-HV TESTING

9. TAN-DELTA TEST RESULTS
WINDING TAN-DELTA LV TO EARTH HV TO EARTH LV TO HV