Experiment - 7


To Study the over-current relay and the effect of PSM and TSM.


  1. Over Current Relay setup
  2. PC Power Chord


Fig 7.1: Connection Diagram of Overcurrent Relay Setup


  1. Switch ON the power supply.
  2. Switch ON the MCB ON/OFF switch.
  3. Press the start button S1 so that LED (marked START) glows.
  4. Start varying the current for the corresponding value using current adjustment knob provided on the left side of the Relay setup module.
  5. After setting the fault current, press the stop button S2 and also press the reset button of the stop clock to make the displayed time to zero.
  6. Now press the start button S1. The stop clock starts counting and when relay trips, it stops counting.
  7. When the relay coil trips, the disc returns to the normal (original) position. Note down the relay current from the relay-current meter and trip time from the stop clock.
  8. Repeat the above procedure from step 5 for various fault currents.