中文说明：
介绍了假定输入为正弦量的算法，半周积分算法突变量电流算法，傅里叶级数算法，并且利用MATLAB Simulink仿真了110KV的3段电流保护。
English Description：
This paper introduces the algorithm of assuming that the input is sinusoidal, half cycle integration algorithm, sudden variable current algorithm, Fourier series algorithm, and uses MATLAB Simulink to simulate the 110kV three section current protection.