Negative sequence (Symmetrical component)

[sarayut]

I'd like to know how do i find I2 (Negative sequence current) if I know Ia, Ib and Ic but don't know angle (in normal system_not fault)? My system's 3 phases 3 wires.

 

[SirAskalot]

You need to specify what you mean by "normal system_not fault"?

Is the load balanced? If so, you know the angles relative to each other. You can then use the symmetrical transformation to find if there is a negative sequence current.

http://en.wikipedia.org/wiki/Symmetrical_components

 

[sarayut]

Thank you very much for answer!, "Normal system_not fault" mean imbalance situation in distribution system. For example Ia= 85 A, Ib= 92 A and Ic= 90 A. I'd like to know I2 for set the I2 pick up to detect low fault current.