Prospective Earth and Short Circuit Current, Earth Fault Impedence

steve100 · Oct 23, 2011

Hi

I'm curent sudying for my 2330 and we have starting looking at the above, however I getting a little muddled/confused. Can someone please help me with some definitions and the us of the following, why we look at them?

Prospevtive Short Circuit Current?
Prospective Earth Fault Current?
Earth Fault Loop
Short Circuit Loop

Also what is the difference between an earth fault and a fault between line and earth?

Any help and clarity would be greatly appreciated!

Steve

needasparks · Oct 23, 2011

You use the findings of 3 & 4 to find out 1 & 2

These are used to determin the overcurrent device is correct.

telectrix · Oct 23, 2011

Prospevtive Short Circuit Current? fault current between line and neutral
Prospective Earth Fault Current? fault current between line and eartrh
Earth Fault Loop the fault current path, usually expressed as efli, the resistance of the earth fault path
Short Circuit Loop assume the same for a L/N short circuit.

Also what is the difference between an earth fault and a fault between line and earth? none.

edit: an earth fault can also be a fault between N and E

steve100 · Oct 23, 2011

Hi

Thanks, so I prosume that the impedence for both 3 and 4 should be low so that the high current flows to operate the protective devices in time?

Also, can you tell me what is the difference between an earth fault and a fault between line and earth?

Cheers

telectrix · Oct 23, 2011

correct, the lower the impedance, the higher the current, and so the faster the overcurrent device will operate. and see my last post for the 2nd bit.

SirKit Breaker · Oct 23, 2011

Tel has given some good info to help you as he always does, but if you need to get your head around it all then get hold of Guidance note 3. This explains and illustrates in detail everything you are asking, and its only a few quid. This book will pay for itself over and over again if you wish to progress in the industry.

Cheers...........Howard.