Over Current & Earth Fault Relay

what is the voltage and current involved, and under which code are u working?

Why not do your own homework?

OVERCURRENT & EARTH FAULT RELAYS Objective: To study t

Electrical wiring codes are different from country to country. They also change depending on the type of location within that country. Consult your regional code standards. CR4 is not the provider of your code standards.

...nor does it provide training with those standards and certification of competence.

Yes, if you want proper co-ordination

The O/C and E/F relay in Main Board is provided

1. To suit rating of the switch board

2. Protect Distribution transformer or Feeder from Over load.

3. Protect cables from Transformer secondary to the Board or Feeder cable.

The O/C and E/F relay for down stream feeders is provided:

1. To protect cables supplying that feeder.

2. To ensure power to remaining loads connected to same Board is not disrupted for fault on a particular downstream feeder or consumer.

3. The probability of phase to earth fault is always higher than phase to phase fault - hence a properly set E/F relay will

3.1 Provide desired discrimination.

3.2 Avoid subjecting downstream cables and equipment to longer duration of fault.

So depending upon ratings (where HRC fuse is not feasible). it is preferred that all downstream feeders have suitable O/C and E/F protection.