Protective Relay Setting With Cable Charging Current

[mrg397cs]

I have a long 13.8 kV cable with a large charging current. The cable terminates at a transfomer. Load current is 25% of the cable charging current. How do I set the 51 function on the cable protective relay?

 

[redfurry]

The same way you normally do. Find a setting suitably higher than peak load current and suitably lower than the minimum fault current.

The only difference in your case is that the power in the cable under normal load will have a very low leading power factor. But for overcurrent protection of the cable, the power factor doesn't matter, only the Amps matter.

 

[slavag]

Hi.
What redfurry saied, isn't importnat level of load for the 51 setting. You need think about load only for 49 function, overload.
Charging current is only important for differential protection.

Good Luck.
Slava