Microprocessor distance protection set is one of the most important protections for high - pressure transmission lines . when high pressure transmission line occurs fault , due to it ' s high voltage level , faults brings big impact to power system and users . the closer the faults occur , the bigger impact it brings 高压线路发生故障时，由于电压等级高，涉及面大，对于电力系统以及电力用户冲击很大；高压线路故障地点距离保护安装处越近，对于电力系统以及电力用户的冲击越大；距离保护的近区故障快速动作具有很重要的意义，本文基于上述目的研究微机距离保护的反时限。
A simple and easy operating criterion is put forward in accordance with the relation between positive - sequence component and negative - sequence component of stator current when the motor is in unbalance and single phase broken . based on analyzing the traditional inverse time - lag overloading protection of motors , an inverse time - lag operating equation with accumulating stator current is achieved , according to the differential equation of the heating and cooling while the current flows into the conductor 在分析电动机传统的反时限过负荷保护的基础上，根据导体中流过电流时的发热、散热微分方程得到了累加定子电流的反时限过负荷保护动作方程，经简化后得到累加定子电流的实用的反时限特性递推公式。
The device can protect start - up status and running status of asynchronous motors by differential protection , over current protection , negative - sequence current protection , zero - sequence current protection , inverse time current protection , under - voltage protection and so on , can measure every kind of electricity , and can process the function of telecontrol , telemetering and telecommunication 其依靠电流差动、速断、负序过流、反时限、零序过流和低电压等保护方法实现了片电动机的运行、启动和自启动过程进行保护，并实现各种电量的计量，同时具有遥控、遥测、遥信的功能。
