Research Of Transmission Line Protection With High Series Compensated Degrees Capacitance

According to UHV power grid planning, the distance of most hydropower andcoal-electricity UHV station to the first falling point are even more400km, thetransmission capacity is restricted to transient stability. In order to make full use of eachchannel of UHV AC transmission capacity, installation of series compensation in thelong distance transmission lines is a reasonable choice. Because of the π connectiontransformation, the series compensation increased brings influence on the lineprotection, the study of the high degree of series compensation effect on line protectionhas important theoretical and practical significance.Firstly, this paper analysis the electric characteristics of transmission line with highseries compensated degrees capacitance after the fault, including inverse current,inverse voltage, low frequency components, etc., and the results were evaluated bysimulation. During the analysis progress, the influence of the MOV is considered, theinfluence factors of reverse current and reverse voltage is analyzed.The influence of transmission line with high series compensated degreescapacitance on line protection is analyzed. For current differential protection, reversecurrent will affect the current phase of the both sides of the line after the fault, and willreduce the sensitivity of the current differential protection; For distance protection,affected by the reverse current and reverse voltage, protection measured impedance andphase of polarization voltage will be affected, further cause the maloperation andmisstrip of the distance protection; For directional element, reverse voltage and reversecurrent will affect the judgment result of the direction element.According to existing problems of transmission line protection, a method oftransmission line protection performance with high series compensated degreescapacitance coping with reverse current is proposed, and gives a protection scheme.Finally, summarizes all the paper, discusses the research results of this paper, andlists out the further research directions.