Study On Comparing Phase Criterion Of Operating Component In Phase Differential Carrier Protection

Phase differential carrier protection is one of main protections of HV and UHV transmission line,because it can protect the whole line and act in good time . The criterion of operating component is a key to operating performance of protection. Traditional phase differential carrier protection adopt comparing the phase of I? 1+K I? 2 as the criterion to differentiate internal and external faults. In general condition it can meet the need of protections. But because of the effect of load currents and capacitance currents, operating performance of protection using this criterion is not satisfactory, especially on long HUV transmission line.A new criterion which compares the phase of ? I? 1+ I? 2 is proposed in this paper in ord to improve operating performance of protection. It is found by theoretical analysis that adopting positive-sequence currents can clear up the influence of load currents and reduce the influence of capacitance currents and increase the ability of resisting transition resistance.It can also improve the sensitive character of protection under internal faults by adding negative-sequence currents to operating currents. In addition,The paper analyse compensating capacitance currents to the new criterion and other factor which can affect the new criterion. It can be proved by theoretical analysis that the new criterion can basically meet the need of protections of HV and UHV transmission line.The paper also uses ATP to set up simulate model of 500kV system , and uses MATLAB to dispose the simulating result . at the same time, the new criterion has been contrasted with the criterion of the I? 1+K I? 2 and ? I? 1 by simulating.The results of emulation show the new criterion can improve operating performance of protection greatly.