Schneider Electric P3U30 and Schneider Electric P5T30 at a 6.6kV system.

The testing scope included verification of key protection functions:

  51 – Overcurrent Protection

• IDMT (Inverse Definite Minimum Time)

• DMT (Definite Time)

  51N – Earth Fault Protection

• IDMT

• DMT

Focus areas during testing:

Pickup current accuracy

Time-current characteristic (IDMT curve) verification

Definite time delay performance

Stability and repeatability of tripping

Proper coordination with system protection scheme

Through detailed secondary injection testing, relay performance was validated against design settings to ensure selective and reliable fault clearance.

Working with both overcurrent and transformer differential protection schemes provides deeper insight into maintaining system stability and equipment safety in modern power networks.