How to Detect a Fault in an Electrical System

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Learn how to detect a fault in an electrical system and what to do in case of a power cut.

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Learning how to identify a fault in an electrical system is key to becoming a top electrician as well as for troubleshooting when you experience a power cut in your home. This video will show you how to locate a fault and how to minimise disruption to your electrical system while you fix the problem.

Translated by Anne Duthoit

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In this video, you will learn how to detect a fault in an electrical system.

A fault in an electrical system is indicated by a local or general power cut that is triggered by the protective circuit breaker system in the electrical panel.

It must be localized and repaired before turning the power back on.

In order to isolate the fault you need to go to your electrical panel.

This operation is applicable in two situations.

The first, which involves the residual current protection, triggers a general power cut, and the second, which concerns protection against surges and short circuits, triggers a local power cut on the circuit.


The residual current protection in the electrical panel protects the user from dangerous contact with a live wire.

If there is a fault, the protection lever will be in the down position.

The source of the fault must then be found.

Turn all the circuit breakers to the OFF position after the residual current protection system is triggered. Also keep the residual current protection system open.

Then turn the residual current protection system back on. Then turn back on, one after the other, each of the protection systems that had been triggered

The protection which, when it is put in the UP position, causes the residual current system to be triggered simultaneously, will indicate the faulty circuit.

Keep the protection system for the faulty circuit open, in the down position. Turn the residual current protection system back on, then the other protection systems in the down position to use the rest of the system that is not faulty.

The faulty circuit is now isolated. The specific cause of the fault can now be sought.


In this case, only a single lever will be triggered.

The circuit breaker controls the risk of a surge or a short circuit. A surge is caused by the use of one or several appliances that use more current than the load level covered by the system. A short circuit is caused by a contact between the two conductors that provide the circuit’s power supply.

Please note: Turn the circuit breaker back on only after you have identified the cause of the fault.

You now know how to repair a fault in an electrical system.

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