Research Of Transmission Line Relay Protection And Fault Location System Based On Transient Current Travelling Waves

The accuracy and rapidity of fault diagnosis are getting more demanding, with the continuous improvement of the transmitted power and voltage of the transmission line. The traditional methods of analysis the steady-state power frequency have been unable to meet the actual demand. The transient protections have fast response to fault, don’t affect by phenomenon of power frequency, such as transition resistance, system oscillation, current transformer saturation, and protection logic is simple, not demanding filtering requirements as well. When a fault occurs in power system, the relay protection and fault location system must selectively act in accordance to different types of faults, clear the fault line quickly and reliably, locate the fault of the transmission line and accurately find the point of failure, restore power supply quickly. All this have a very important role in the entire power system security and stability and economic operation.This paper studies the theory of wavelet transform and the transient current of transmission line. On that basis, transforms the mode component of the transient fault with db4wavelet after phase-to-module transformation, extracts the current characteristics of the fault traveling wave by wavelet transform, then exploits the relationship between wavelet transform maximal modulus to construct the criterion of fault type recognition, later proposes the criterion, which only need zero-mode component to qualitative analysis. The algorithm uses the polarity of zero-mode component only to determine the ground fault and non-ground fault, doesn’t participate in follow-up judgment. This can effectively eliminate the adverse impact of distortion of the zero-mode component in the communication process to the elections, so the new algorithm improves the reliability of action of relay protection.In this paper, fault location algorithm has been systematically studied, compared to the existing fault location algorithm, analyzed the inadequacies of the previous algorithm, proposed a new fault location algorithm, which combines wavelet transform and correlation method. The new algorithm chooses a different line-mode component for different types of failure to fault location. It is more accurate in positioning than a single line-mode component in the past. In addition, the algorithm uses wavelet transform to extract the characteristics of the traveling wave current, and then uses the correlation method to judge the type of the reflected wave. The advantages of the two methods combine to overcome the shortcomings of the wavelet transform method, which can’t accurately identify the type of the reflected wave, and the shortcomings of the correlation method, which is difficult to identify the data window length and traveling wave head, so the new algorithm improves the accuracy of fault location.The new start-up mode on the system, which combine the center point of the bus voltage threshold detection and the A-phase current mutation detection together, in this paper, effectively overcome the problem of the traditional over-voltage detection method, which the system does not start or delay start, when the system occurs three-phase short circuit.In the environment of Matlab/Simulink, the paper modeled on500kV both ends of the transmission line, simulated different types of faults, writ the fault diagnosis procedures according to the proposed new algorithm and verified the new algorithm. On the LabVIEW platform, the paper completed the overall design of the transmission line relay protection and fault location system under the modular design ideas. Using simulated failure data as input, a full line random failures test has been done.