配电网合环冲击电流计算方法及其简化计算公式

配电网合环操作可能产生较大的冲击电流,影响电网的安全稳定运行。为此提出一种配电网合环冲击电流计算方法,并推导了较准确的非合环支路冲击电流解析计算公式。基于最佳频率下合环前后的潮流和戴维南定理,计算合环冲击电流衰减时间常数;基于额定频率下合环前后的潮流结果和最佳频率法计算获得的衰减时间常数,计算合环冲击电流及非合环支路电流。最后,对不同方法(包括PSCAD/EMTDC暂态仿真)计算冲击电流的结果进行比较分析,验证了所提方法的实用性和有效性。算例结果同时表明某些非合环支路的冲击电流比合环支路冲击电流要大,表明非合环支路冲击电流简化计算公式及其计算校验是非常必要的。

Methods and Simplified Formulas for Calculating Surge Currents from Loop Closing in Distribution Networks

The loop closing operation of a distribution network may generate a rather large surge current affecting safe and stable distribution network operation. A method for calculating the surge current from loop closing in distribution networks is proposed, and the accurate analytic formulas for calculating the surge currents of non-closing branches are deduced. Based on the Thevenin's theorem and the power flows before and after loop closing operation at optimum frequency, the decay time constant is computed. Based on the decay time constant and the power flow results before and after loop closing operation at the rated frequency, the surge currents of loop closing branch and non-closing branches can be calculated. Finally, the computing results of different methods, including PSCAD/EMTDC transient simulation, are compared and the results show the practicality and validity of the proposed method. Moreover, the results also show that the surge currents of some non-closing branches are larger than that of the closing branches. Thus it is quite necessary to check the surge currents of non-closing branches.