Abstract Electric power system is composed of generator, transformer, power line and load components, used for electricity production, transmission, distribution and consumption of a variety of electrical equipment in a certain manner as a whole. In power system operation process, will inevitably fails. Despite the failure probability is very small, the duration is not long, but the consequences are often very serious. The fault analysis of power system and fault location is a very important link. When a fault of an electric power system will cause the following situations: ( 1) connected with the short circuit and a power supply of the electrical equipment in current increases rapidly. ( 2) the fault point around electrical equipment voltage drop, but from the point of failure of the electrical distance is, the voltage drop more quickly, and even down to zero. ( 3) so that the power system stability is destroyed. ( 4) a circuit starting end of voltage and current of the ratio between the measured impedance changes will occur. Is due to a short circuit would have severe consequences, thus caused the high attention. In addition to eliminate the cause short-circuit reason, still should be in short circuit fault happens to take timely measures to minimize losses, short circuit, such as the use of protective relaying fault isolation, at the right place install reactor to limit the short circuit current, the automatic reclosing of eliminating instantaneous fault makes the system back to normal as soon as possible.
