Study On The Accurate Fault Location System For Long Transmission Line

Accurate fault location for high-voltage transmission line can greatly lessen the time needed for patrolling line and quicken the power restoration. It is significantly important to the secure and economic operation of power system.Accurate fault location algorithms using data synchronically sampled from all ends of the line based on GPS are presented in this paper. The following work has been done.For long and ultra-long transmission lines, an algorithm using distributed parameter line model and based on finite difference method is presented for the first time in this paper. In the algorithm, phase components are converted to modal components firstly; then the numerical solution for transmission line wave equations is obtained in the modal domain using finite difference method; by the exclusiveness of the voltage on the fault point, the fault position is determined based on the above numerical solution. Accurate distributed parameter line model is adopted, so the algorithm can well reflect the wave characteristic and real operating condition of transmission line. Its model error is little. Quanta of various frequencies all fulfill the line wave equations. The fault location result is obtained directly from the wave equations, so the algorithm is highly adaptive to sampled data. It can locate faults accurately even when there exists highly transient process.For the transmission lines having installed series compensating capacitor, an algorithm based on differential equation method is presented for the first time in this paper. In the algorithm, phase components are converted to modal components firstly; then correspondent line-mode component is chosen to calculate the fault position according to the fault type. The mathematical model of the algorithm is differential equation that considers the transient process. Compared with conventional algorithms using phasors of fundamental frequency, the algorithm can overcome the influence of aperiodic component in the fault currents, and the data window used can be small. So the algorithm can accurately locate the fault position both in transient faults and in stabilized faults. First, two fault points located in both sides of the compensating capacitor can be determined. Then, according to the principle that the voltage of real fault point calculated by data collected at both sides of transmission line must be equal, the real fault location can be decided.Plenty of digital simulations are performed on the algorithms using the PSB(Power System Blockset) toolbox of MATLAB. And factors, which affect theaccuracy of the algorithms, are analyzed. Simulation results show that thealgorithms presented in this paper are highly accurate and robust. From the view ofengineering application, the accuracy is affected neither by fault position, fault type, fault resistance, system frequency, the operation model of power system, nor by variance of the zero-sequence parameters basically.The hardware and software realization of the corresponding fault locator is also presented in this paper concisely. Plenty of dynamic simulations are performed on the fault locator by using Real-Time Digital Simulation (RTDS) system to verify the algorithms presented in this paper. Simulation results show that highly accurate and robust results can be obtained by using the algorithms and the locator. These sufficiently prove that the algorithms are feasible and accurate; the locator is practical and reliable.