A novel concept for voltage collapse protection based on local phasors

Voltage collapse is basically a dynamic phenomenon with rather slow dynamics. Therefore mostly static methods based on the system Jacobian matrix were proposed for its analysis. Because of computational burden these methods are slow and not appropriate for estimating the proximity of power system to voltage collapse in real time. Therefore a new scheme for protection against voltage collapse based on local phasors is proposed. Detection of critical lines instead of critical nodes is used. The difference between apparent power flows on the receiving and the sending end of the line is used for computation of voltage collapse indicator. According to the developed protection scheme, the relay sends a triggering signal to reactive power sources to increase reactive power production. Because of the computational simplicity the proposed protection scheme can be used for on-line system monitoring as well as for off-line analyses.