A compensation algorithm based distance protection considering frequency-dependent parameters

The distributing and frequency-dependent parameter characteristics of ultra-high voltage (UHV) long transmission lines lead to the nonlinear relationship between the measured impedance of conventional distance protection and fault distance. The harmonics are remarkable in the early failure period, and only if the frequency-dependent parameter characteristics are considered, the long transmission line distance protection could action correctly. A new distance protection case that considering the frequency-dependent parameters is proposed. Based on electromagnetic field theory and long transmission equations, the calculation of voltage and current in frequency-dependent parameters transmission line is decomposed to the calculation in distributing parameters transmission line and the concatenation of a compensation algorithm, which could be transformed to a finite impulse response (FIR) filter. According to this, the voltage and current of the terminal of the distance section could be calculated from the measuring point, and the distance protection can be set by the fault location. Simulation results show that this new method is fast and accurate in both time domain and action.