基于过渡电阻计算的距离保护

Ground distance relay based on fault resistance calculation

单相接地故障是高压输电线路最常见的故障类型,但发生接地故障时高过渡电阻的存在容易引起距离保护拒动或误动。为了提高距离保护的可靠性,本文以输电线路单相接地为例利用对称分量法找出传统接地距离保护的原理性缺陷,提出了一种基于保护处监测到的有功功率计算过渡电阻的新方法,这种补偿的方法改进了距离保护的判据,具有对过渡电阻的自适应性,根据过渡电阻的大小自动补偿附加测量阻抗。本论文又分析了过渡电阻、两侧电源电势相位差δ对距离保护阻抗测量的影响。从ATP仿真结果知,对于各种类型的接地故障,尤其对高阻接地故障,保护表现出令人满意的性能,这种新方法解决了距离保护的拒动问题。

The single-phase earth fault is the most common fault type on high voltage transmission lines. But the high fault resistance may result in tripping missing or maloperation of distance relays. In order to improve the reliability of distance relays, this paper takes single phase to ground fault of high voltage transmission lines as an example, and uses a symmetrical component method to find out inherent defect of the traditional distance protection. Then, a new compensation method based on fault resistance calculation is presented. The fault resistance calculation is based on monitoring the active power at the relay point. The compensation method improves criterion of distance relays. It can adapt to different earth resistance, and the compensation component is changed with the different earth-fault resistance adaptively. Moreover, this paper analyses effects of fault resistance and phase difference between electric sources on two ends on impedance estimation of distance protection. From simulation results of ATP, the relay shows satisfactory performances under various fault conditions especially for the ground faults with high fault resistance. This new compensation method avoids the under-reach problem in ground distance relays.