Study On Short Circuit Fault Calculation Method Of Distribution Network

The fault calculation methods in distribution networks are basic calculation in distribution network plan and design, fault analysis, relay setting and coordination and are required to have good calculation speed and high calculation efficiency.The key problems of holding up the speed and efficiency of fault calculation in distribution networks are how to simulate network operations and short circuit faults well.By network changing, the ports are constructed and a unified method is given to simulate loop-opening and short circuit faults. The loop-opening and short circuit faults simulation method is unified and simple and can simulate any kind of fault easily, including double-point-to-earth fault.Based on the above simulation, the faulted weakly meshed network is divided into two networks:one is the pure radial symmetrical network and the other is the unsymmetrical network to simulate loop-opening and short circuit faults. At the new ports boundary, according to the multi-dimensional Thevenin theorem and Ohm's law, using phase-sequence parameter transformation method, the ports injection current calculation formulas are obtained. According to the relationship among node injection current, branch current, and node voltage in radial network, the branch current and node voltage calculation method is given. A new method to calculate short circuit faults in distribution networks is presented. This fault calculation is totally based on the branch impedance parameters in radial network instead of node impedance parameters. So the method is adaptive to network operation and is highly efficient. The non-fault branch currents and node voltages calculation are easy and direct.Based on the proposed algorithm, a program is designed for fault calculation and is implemented in a distribution network. This approach has been proved generality and computationally efficiency.