15. Analysis of the causes of operation of the RCD and an algorithm for troubleshooting the electrical installation

When the RCD trips, it is necessary to determine the type of malfunction in the electrical installation. In this case, the following is the order of actions of the electric power plant servicing personnel.

Rectify the RCD. If the RCD is cocked, it means that in the electrical installation there was a leakage of current to the ground caused by an unstable or short-term failure of the insulation. In this case, it is necessary to carry out a general control of the insulation state. To test the operation of the RCD by pressing the "Test" button.
If the RCD is cocked and instantly operates, it means that either in the electrical installation there is a defect in the insulation of any electrical receiver, wiring, wiring harnesses of the electrical board, or the RCD is defective. In this case, you must do the following:
  1. Disconnect all circuit breakers of the group circuits protected by the RCD.

    If the circuit breakers are single-pole or three-pole and do not open the neutral conductors, then taking into account that the current leakage is possible from the neutral conductor, it may be necessary to disconnect all the zero working conductors from the busbar to detect a defective circuit.

  2. Rectify the RCD.
  3. If the RCD is cocked, check the operation of the RCD by pressing the "Test" button. Instantaneous tripping of the RCD means that it is OK, but there is a leakage current in the protected circuit.
  4. Consistently turn on the circuit breakers.
  5. If the RCD is triggered when a certain circuit breaker is switched on, it means that there is insulation damage in the circuit of this switch.
  6. Disconnect or disconnect all the electric receivers in the circuit of the circuit breaker, upon activation of which the RCD has tripped.
  7. Rectify the RCD.
  8. If the RCD is cocked, it means that the insulation fault is in one of the electrical receivers.
  9. Consistently switch on each electrical receiver of the circuit.
  10. The RCD is activated when a certain electrical receiver is switched on.
  11. Disconnect the defective electrical receiver.
  12. Connect all electrical receivers (except defective ones), cock the RCD, make sure that the RCD does not work. Test the operation of the RCD by pressing the "Test" button.

Notes:

As per item 8. If the RCD is not cocked for all the disconnected receivers of this circuit, this means that the insulation of the wiring is defective.

As per item 3. If the RCD is not cocked, it means that there is a fault in the insulation of the wiring of the electrical board or the failure of the RCD.