第27卷 第28期 2007年10月 中 国 电 机 工 程 学 报

Proceedings of the CSEE Vol.27 No.28 Oct. 2007

©2007 Chin.Soc.for Elec.Eng.

(2007) 28-0059-07 中图分类号：TM77 文献标识码：A 学科分类号：470 10 文章编号：0258-8013

远距离输电线路等传变瞬时值差动保护

文明浩，陈德树，尹项根，张 哲

（华中科技大学电力安全与高效湖北省重点实验室，湖北省 武汉市 430074）

Long Transmission Line Current Differential Protection by Using Instantaneous

Value After Equal Transfer Processes

WEN Ming-hao, CHEN De-shu, YIN Xiang-gen, ZHANG Zhe

(Electric Power Security and High Efficiency Lab, Huazhong University of Science and Technology,

Wuhan 430074, Hubei Province, China)

ABSTRACT: It is revealed that the interaction between transient voltage and current still satisfies a uniform transmission line's distributed parameters model after distributed voltage and current pass through the same linear circuit. The distribution of voltage is a liner function along the transmission line when its frequency is near power frequency. On the basic of the analytical results, a new scheme of long transmission line current differential protection by using instantaneous value after equal transfer processes was presented. The voltage and current have equal transfer processes from primary electrical quantities to instantaneous values used by differential protection. At first the current sampling values pass through virtual digital CVTs. And then the voltage and current sampling values are processed by a low pass filter. According to the instantaneous value of transmission line voltage, the current instantaneous values of shunt reactors and Π equivalent circuit capacitance can be calculated. After removing these two kinds of current, sampling value differential protection based on all components and fault component can be applied. The results calculated by ATP show that the proposed technique has highly reliability, a short operation time, excellent performance under high-resistance earth-fault conditions and phase selection ability.

KEY WORDS：long transmission line; current differential protection by using instantaneous value after equal transfer processes; distributing capacitance; capacitive voltage transformer; shunt reactor; relay protection

摘要：研究表明线路分布电压、电流经过相同的线性电路传变后，其相互关系仍符合原线路分布参数模型，工频附近的

基金项目：国家自然科学基金项目(50477046)。

Project Supported by National Natural Science Foundation of China (50477046)．

电压信号在线路上接近线性分布。在此基础上，提出一种用于远距离输电线路保护的等传变瞬时值差动保护方法，该方法从线路一次电气量到用于差动保护计算的瞬时值，电压和电流经过的传变环节基本相同。首先将电流采样值经虚拟数字CVT处理，然后对电压和电流采样值通过相同的低通滤波处理。由线路电压瞬时值分别实时计算出流入并联电抗器和流入线路Π型等值电路两侧电容的电流瞬时值，再从线路每侧电流除去这两部分电流，用得到的新电流瞬时值作常规采样值差动和故障分量采样值差动保护计算。ATP仿真表明，等传变瞬时值差动保护可靠性高、动作速度快、耐过渡电阻能力强、具有选相能力。

关键词：远距离输电线路；等传变瞬时值差动；分布电容；电容式电压互感器；并联电抗器；继电保护

0 引言

远距离输电线路一般是500 kV以上电压等级的长线路，其发生内部故障时，需要由继电保护装置迅速将故障切除，以减少事故损害程度。差动保护是500 kV以上电压等级的线路主保护之一，它能无延时的切除故障，但是为了保证远距离输电线路差动保护正确、可靠、有选择性的工作，必须克服一个主要障碍，即外部故障和正常运行时，输电线路的分布电容电流不要造成差动保护误动作，且在内部故障时，不要因采取技术措施而降低保护装置的灵敏度。

由于分采样值差动保护[1-2]主要应用于短线路，

布电容电流问题，目前还不能作为远距离线路的主保护。现有技术中对分布电容电流问题，国内外采用最多的技术是提高差动保护的动作门槛和基于相量差动保护[3-4]的电容电流补偿算法。这两种技术有如下不足：①提高差动保护的动作门槛将明显降低