Book of Power system protection

1 - Insulation Resistance Test

 Used to measure the insulation resistance of the transformer components.
 Apply HV DC then measure resistance.
 Indicate the condition of the insulation.

2 - Insulation Resistance Test
 Used to measure the turns ratio of the transformer (Primary and Secondary Windings.
 Apply voltage on winding then measure the voltage induced in the other winding.
 Percentage between voltages is the turns ratio of the primary and secondary windings.
 Accurate test.
 East to perform.

3 - Winding Resistance Test

 Used to measure the resistance of the transformer windings (primary and secondary).
 Done using LV DC source + Multimeter.

4 - Polarity Test

 Conducted to verify the polarity of the transformer windings.
 Apply DC source to the primary then measure secondary voltage.
 Polarity of the windings determined based on the direction of the induced voltage in the secondary winding.
 Simple and quick.
 Prevent damage of the transformer during installation.

5 - Open Circuit Test

 Performed to determine:
No Load Losses.
Magnetizing Current.
 Keep the secondary open circuited then apply voltage on the primary winding, then measure the primary (current and voltage).
 Calculate (No-Load Losses & Magnetizing Current).
 Determine the equivalent circuit then calc Efficiency and Regulation.

6 - Short Circuit Test

 Performed to determine:
Full Load Current.
Transformer Impedance.
 Keep the secondary short circuited then apply voltage to the primary winding, then measure the primary (current and voltage).
 Calculate (Full-Load Current & Impedance).
 Determine Winding Resistance.
 Determine Leakage Inductance.

7 - Sweep Frequency Response Analysis (SFRA)

 Non-destructive test used to detect any changes in the transformer mechanical structure.
 It can detect Winding Deformation or Shorted-Turns.
 It makes comprehensive assessment of the transformer condition.