基于电子式互感器双A/D采样的差动保护可靠性方案研究

Research of the differential protection reliability scheme based on the electronic transformer double A/D sampling

分析了智能变电站中电子式互感器双A/D采样的理论偏差及采样数据异常造成差动保护误动作的临界条件,在此基础上提出了一种基于电子式互感器双A/D采样的差动保护可靠性方案。该方案基于采样值瞬时值判别,设置绝对偏差判据和相对误差判据,两个判据协同工作,当仅有一个采样点数据异常时,采用线性插值算法对修复,连续两个采样点异常时闭锁保护。通过理论分析和仿真验证可知,该方案可以有效保证差动保护在双A/D正常工作时不会误闭锁、任何时候一路A/D异常时能可靠闭锁、在双A/D偶尔异常时仍能可靠工作。该方案可靠性高、运算量小、易于实现、并具备一定的容错能力,有着广泛推广的现实意义。

The theory error of electronic instrument transformer double A/D sampling in smart substation and the abnormal sampling data can cause the differential protection misoperation. We analyze the critical conditions of this misoperation, and put forward a reliable scheme for differential protection based on double A/D sampling of electronic transformer. The scheme is based on sample instantaneous value judging, setting absolute deviation criterion and relative error criterion. The two criterion work together. When only one sample point gets abnormal data, we use linear interpolation algorithm to repair, and when successive two sample points have anomalies, we use latch-up protection. Theoretical analysis and simulation results show that the scheme can effectively guarantee the double A/D will not get latch-up protection mistakenly in normal work, when one of A/D is abnormal, it can get latch-up protection any time, and when double A/D is occasionally abnormal, protection device can still work reliably. The scheme shows a high reliability, small amount of calculation, certain anti-interference ability, and is easy to carry out, which can be widely applied in practice.