Charging Current Compensation for Distance Protection

One difficulty of the application of line protections to long transmission lines is the influence of the large capacitance of the line. When a fault occurs on a long line, relatively large magnitude harmonic components of current and voltage are superimposed on the fundamental frequency component due to the large capacitance of the line. This harmonic component can cause oscillation of the distance measurement. It is difficult to remove the harmonic component completely because the order of the harmonic component varies with several conditions. Our research has shown that the degree of oscillation can be reduced significantly by compensating for the charging current in the impedance calculation. This proposed charging current compensation (CCC) method provides an excellent result under all conditions. In this paper, the calculation method of CCC is introduced and good performance of CCC for the application to long overhead lines and to the long cable line is proven based on Alternative Transient Program simulations.