Algorithms of phase and current comparison protection for transmission lines

The paper presents a concept of a highspeed phase/current comparison protection (PCCP) based on the digital evaluation of the differences both in phase angle and instant values of the current waveforms measured at the protected line terminals. Signal processing algorithms immune to direct current and highfrequency components, harmonics and current transformer saturation are described. The results of faults offline simulations for transmission system model with frequencydependent parameters estimated in time domain are used for the analysis of the PCCP schemes performance during inzone and outzone faults.