中文说明：本程序是用节点导纳矩阵计算三相短路电流输入数据--形成节点阻抗矩阵--选择故障点---计算短路电流----计算个节点电压---计算指定支路的电流
English Description：
This program is to use node admittance matrix to calculate input data of three-phase short-circuit current - form node impedance matrix - select fault point - calculate short-circuit current - calculate node voltage - calculate current of specified branch