Hidenari Amo

Charging current compensation for distance protection

When a distance relay is applied to a long transmission line, the capacitance of the transmission line causes oscillation of the distance measurement, although the exact nature of the phenomenon has never been clearly defined. Our research has shown that the degree of oscillation can be reduced significantly by introducing charging current to the circuit model to be solved by the distance relay. In this paper, the undesirable influence of charging current on distance protection is introduced, after which the effect of charging current compensation for a distance relay is proven by practical simulations. Furthermore, the advantage of this method of charging current compensation as opposed to other methods is also explained.

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.