Value of fault current

[Neelesh]

We calculate maximum fault current in the system to determine switchgear, cable, busbar etc. rating.

However to set the protection relay we may require to know minimum value of fault current. Is it right?
As far as I know, to set protection relay following parameters are to be known to us
1)System damage curve
2)System short time withstand
3)Inrush currents if any

Is there any other parameter to look at while setting protection relays?

 

[ron]

Re: Value of fault current

Every type of relay has a particular protection characteristic. So you would need to know the max and min of that component of power.
ie. what is the maximum phase angle difference that your system can tolerate before a 25 relay (synch check) should be considered acceptable. There is no manufacturers cut sheet to determine some of these, its experience. For example, whether your system can tolerate a 10% or 15% undervoltage before you trip the main breaker will be a judgment call based on experience. Protective relaying is more of an art than a science.