电力电缆的零序电流保护方案

电力电缆的零序阻抗随零序电流的大小而改变,如果采用恒定值的零序阻抗来进行零序电流保护的整定,容易导致保护的不正确动作.由于电缆线路的零序阻抗是零序电流的函数,提出了基于迭代算法的零序电流保护的方案.利用经验公式来确定零序阻抗初始迭代值;采用最小二乘法对阻抗-电流曲线进行拟合求取零序阻抗;利用修正后的零序阻抗再次计算短路电流,直至前后2次计算出的接地电流的误差满足迭代精度要求.按照在线计算的零序阻抗值进行零序电流保护的整定,使得保护的特性适应于当前的电流值.保护的整定完全由装置自动完成,对当前系统的运行方式具有较好的自适应性.

Zero Sequence Current Protection for Power Cable

The zero sequence impedance of the cable changes with the zero sequence current as the zero sequence current flows inthe ground and the sheathing simultaneously. If the constant zero sequence impedance is used to set the current, me zero sequence current protection can not operate correctly. Considering the zero sequence impedance of the cable to be the function of the current, the adaptive zero sequence current protection is proposed based on lteratlve algorithm. the initial value is obtained according to the empirical formula. The zero sequence impedance is solved through the fitting of the impedance-current curve by the least square method. The setting value of the protection is finished automatically by the protection device and adapts well the present operation mode of the power system.