超高压电网反时限零序过流保护简化整定方法

随着国内超高压电网中传统四段式定时限零序电流保护的整定配合越来越困难,反时限零序过流保护作为后备保护逐渐得到应用。但目前其定值整定多依赖工程经验,缺乏理论支撑,给实际应用带来诸多限制。为此,首先结合超高压电网变电站装设接地变压器的结构特点,分析了零序网络电流的自然差异分布特性,给出了简化整定的理论基础。然后提出采用全网统一定值整定原则的反时限零序过流保护简化整定方法。最后通过理论分析说明了简化整定后仍可保证选择性与灵敏性。利用国内某区域电网500 kV局部输电网算例进行计算,其结果证明了所提简化整定方法有效且合理。

A novel simplified relay coordination method for inverse-time zero-sequence overcurrent relays applied in an extra-high voltage power grid

With the increasing difficulty of coordination of conventional four-stage definite-time zero-sequence current relays in the domestic Extra-High Voltage (EHV) power grid, inverse-time zero-sequence overcurrent relays are gradually applied as backup protection. However, the settings of inverse-time relays are determined according to engineering experience rather than theoretical analysis. Such action brings many restrictions to its practical application. To this end, this paper first combines the structural characteristics of grounding transformers installed in the EHV power grid substations and analyzes the natural distribution difference characteristics of zero-sequence current to show the theoretical basis of the simplified setting. Then, the coordination method based on the unified setting principle of inverse-time zero-sequence relays is proposed. Finally, the paper proves that selectivity and sensitivity are still guaranteed after simplification via theoretical analysis. The proposed method is applied to the 500 kV partial transmission network of the domestic certain power grid. The results show that the proposed simplified relay coordination method is effective and reasonable. This work is supported by Science and Technology Project of Northeast Branch of State Grid Corporation of China (No. SGDB0000DKJS1900180).