Transmission Line Fault Location And Detection

With the rapid development of the national economy, which has promoted a great stride to Chinese electricity utility, long-distance transmission lines have got an important significance to the operation of the power grid. Once a transmission line failure has happened, how to find the point of failure quickly and accurately has an important significance to shorten the power recovery time of the non-fault areas. The unnecessary economic losses like shutdown and stagnant production caused by the power failure can be reduced to a lower level. So the research of fault location has an important significance. In this thesis, several aspects have been studied and discussed deeply based on fault analysis method in order to solve the problem of detecting the fault location in high voltage long distance transmission line.Firstly, the development history and the research status at home and abroad of the fault location method have been proposed in this thesis. The single-terminal fault location method and double-terminal fault location method were derived and the advantage and disadvantage of the two methods have been compared at the same time. When deriving the principle of single-terminal fault location, it can be found that the precision of this fault location result can be affected by the changes of the system impedance and the size of the transition resistance. Aiming at the shortcomings and defects of the single-terminal fault location method, the double-terminal fault location method has made up its defects and increased the precision. But the most difficulty of the double-terminal fault location method is the real-time synchronization of the double-terminal data detection, it is difficult to realize the complete synchronization under existing condition. Although the GPS can maximization the precision of the synchronization, but the cost is too high.Aiming at these problems, a fault location algorithm based on the phase characteristics of hyperbolic tangent function and double-ended asynchronous was proposed on the basis of distributed parameter model. The first step of this method is to gross orientation the line with double-terminal data according to hyperbolic tangent function. The kirchhoff law was used to translated the equation based on the distributed parameter model. The hyperbolic tangent function is structured by assuming the fault point has been detected, and the odd function characteristics of the hyperbolic tangent function which has only one zero-crossing is used to make the location. Only if the assuming fault point coincides to the fault point, function is zero. This method eliminates the effects of the location result from false root. Because of the using of double-terminal fault location method, so the synchronization error of the double-terminal data is bigger. The second step of this method is to correct the result of the fault location with double-terminal asynchronous method aiming at the problem of double-terminal data asynchronous. An asynchrony time is set to establish two equations before and after the fault with the characteristic which the voltages are equal from the two terminals to the fault point. The asynchrony time is canceled to get the correction equation which can correct the fault location result and realize the final fault location. The simulation results show that this method cannot be affected by the factor of incidence angle, transition resistance and fault type, and has a better robustness.Finally, the traveling wave method was proposed in this thesis. And the test of impulse-voltage method has been made, which shows the accuracy and rapidity of the traveling wave method. At the same time, traveling wave method also gets a shortcoming. When the fault point happens at the range hole of traveling wave method, the accurate fault point detecting by traveling wave method cannot be detected.All the new methods can be realized at the existing condition and have a certain application value. The simulation of the test can prove the effectiveness of this method.