Based on the analysis of main fault types of LV (Low Voltage) flameproof motor, the negative sequence protection principle is proposed for its asymmetric short circuit fault and open phase fault.

通过分析低压隔爆电动机的主要故障类型，针对不对称性短路故障和断相故障提出了采用负序保护原理进行保护的方案。

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This paper presents that the protection for the phase to phase fault should be composed of high frequency teleprotection channel and overreached distance relay.

提出只有将高频通道、超范围距离元件配合构成允许式纵联距离保护，才能保护同杆双回线跨线不接地故障。

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Electrical products which have LCD time counter, Layer sensor, Three-phase AC fault protection relay and so on.

其中电器类产品有液晶显示计时计数器、平层感应器、断相错相三相交流保护继电器等等。

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