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系统故障时,谐波会使距离保护的基波阻抗特性圆发生畸变,导致保护拒动和误动,保护范围缩短,严重时会发生无选择性动作。其中三次谐波影响最严重,五次谐波影响次之,谐波次数越高影响越小。保护采用R-L模型算法,利用切比雪夫II型低通数字滤波器加零点设计法,具体针对110kV线路的数学模型,削弱200Hz以上的频率分量,降低线路中分布电容的影响,达到有效提高保护可靠性的目的。
When the system is faulty, the harmonics will make the circle of fundamental impedance characteristic of distance protection distorted, which will lead to the protection of rejection and misoperation, the shortening of protection range and the non-selective action in severe cases. Among them, the third harmonic has the most serious influence, the fifth harmonic has the second, the higher the harmonic frequency, the smaller the impact. Protection using RL model algorithm, the use of Chebyshev II low-pass digital filter plus zero design, specifically for the 110kV line mathematical model, weakened more than 200Hz frequency components, reducing the distribution of capacitance in the circuit to effectively improve the protection of reliable Sexual purpose.