井下电气设备和电缆电网的严重事故,是由短路电流(特别是经接地电阻和电弧的短路时)保护的不满意动作,和没有排除电动机在断相状态下工作的有效保护引起的。当保护连接处的电流超过被保护线路的工作电流时,已知的过电流保护便瞬时动作。在长距离辐射状电缆的煤矿井下区段电网中, Downhole electrical equipment and cable power grid serious accidents, short-circuit current (especially by the grounding resistance and arc short circuit) to protect the unsatisfactory action, and did not rule out the motor in the phase-off state of the effective protection of work caused. When the current at the protection connection exceeds the operating current of the protected line, the known overcurrent protection operates instantaneously. In long-distance radial cable coal mine section of the grid,