# Re: Faults in Electrical Systems (back to basics)

Home Electrical Engineering Forum General Discussion Faults in Electrical Systems (back to basics) Re: Faults in Electrical Systems (back to basics)

#13055
Spir Georges GHALI
Participant

Dear Mr. Mill

Refer to this topic, I want to draw your attention that according to the IE… definitions, we have 2 kinds of faults can happen in any Electrical Network that are :

• Overcurrent Faults
• Earth Faults

Where the “ Overcurrent Faults ” are divided as follow :

1- Over-Load Fault where his percentage is between “ 15-20 % ” to “ 50-80 % ” of “ ILoad ”.

2- Short Circuit Fault where his percentage is more than “ ≈150 % ” of “ I ” and may be achieved to “ 10 time ” or even more.

Also the “ Short Circuit Faults ” are classified depending on his kind as following :

1. 3 Phases Short Circuit with or without Neutral ( possibility : ≈ 5-10% ) : the flown current is the biggest one.
2. 2 Phases Short Circuit with or without Neutral ( possibility : ≈ 10-20% ) : the flown current is “ ≈ 86% of 3 phases short circuit current ”.
3. 1 Phase & Neutral Short Circuit ( possibility : ≈ 70-80% ) : the flown current is the smallest one comparing with 1 or 2.

Rem. : it’s not necessary that a Short Circuit Fault be connected also to the Earth.

By the way, the figure no. 2 in the Topic is not relative to the 2nd fault “ Phase to Phase Fault ” ( it’s the same as no. 3 ).