Abstract: Long cable laying will lead to the increase of ground capacitance, cause great interference to the secondary control loop, and then affect the normal operation of electrical equipment.The influence of ground capacitance of long cable on the secondary electrical locking loop was analyzed.Ground circuit capacitance and the maximum allowable cable length were calculated theoretically.Besides, corresponding improvement measures were put forward for the influence of distributed ground capacitance of long cable on the secondary control locking loop, which improved the reliability of logic operation of anti-error locking in the station and provided a reliable guarantee for safe and stable operation of the power grid.