Protection Of Research On The Impact. The Cvt Transient Right Direction

Nowadays the capacitor voltage transformer (CVT) has been more and more widely used in electrical power system since it's cheap, won't cause ferroresonance and many other advantages. However, CVT's transient performance is not very good compared with TV and under some severe conditions it may have negative effects on relay protection. In this case, it is very important to study the transients of CVT, analyze the effects of CVT on protection, and bring forward the solutions respectively.This paper has mainly completed these tasks: analyzed the influence of CVT's transient noise on distance protection and directional protection and achieved many useful conclusions;focused on the zero-sequence and negative-sequence directional protection and made a great deal of simulation by ATP to prove these former conclusions;based on all of the above, finally brought out a new directional protection method which was evaluated by a great amount of simulation. It combined zero-sequence and negative-sequence directional protection together and added a voltage threshold to avoid the misjudgement caused by CVT's transients.