Research And Application Of Controlled Reclosing Strategy For 10kV Distribution Network

Reclosing can greatly improve the supply reliability of power system, however when reclosing at permanent fault, the followed huge current will be an enormous pressure to power system. In order to realize security reclosing at 10kV power distribution network, through combining with controlled switching technology, two-phase synchronous controlled reclosing strategy has been used to complete the reclosing. The pair combinations in three phases were reclosed synchronously in turn at optimal voltage phase angle to control the reclosing current peak value and duration time. The parameters of reclosing circuit can be identifying by a parameter identify algorithm, and the fault type can be determine by compared the calculated periodic component peak value with the preset threshold value of permanent fault.Firstly, this paper carries on simulation analysis to controlled reclosing theory, and obtains conclusion that the reclosing voltage phase is the key point to decide the reclosing current peak value and duration time. According to simulation analysis of reclosing parameter identification algorithm,135° and 315° has been selected as the optimal reclosing phase. Finally, the simulation result of controlled reclosing process show that, based on high-speed actuator, reclosing current peak value and duration time can be significantly reduce when using controlled reclosing theory.Based on the theory of controlled reclosing and requirement of processing speed and sequence control, choosing FPGA as main control chip, a controlled reclosing control system was designed. The design idea and the function of hardware circuit have been introduced in detail. The software design of the control system was accomplished by Verilog HDL language. The program correctness was verified by Modelsim simulation results of controlled sequence and output of key module programs, such as data acquisition and reclosing algorithm.The reclosing control system usually works in high voltage and magnetic environment, so, it must have excellent electromagnetic compatibility. This paper tests the working reliability of the control system from three aspects, such as power frequency magnetic field, electrical fast transient burst, damping oscillation wave. Preset phase reclosing and fault type detection experiment is been conducted by using low-voltage reclosing circuit test platform. Results of experiment indicated that the control system can reclose at preset phase and the error is less than 5°, the circuit parameter identification algorithm can accomplish the calculation within 6ms, the fault type can be accurately determine. The control system can implement the controlled reclosing strategy.