考虑输电线路动态热特性的自适应过负荷保护方法

Adaptive overload protection method considering the dynamic thermal characteristics of a transmission line

随着电力系统规模不断扩大、电网互联和复杂程度不断提高,线路过负荷导致的过载主导型连锁故障风险日趋增大。现有研究未计及过负荷线路功率的动态变化,缺乏对线路允许过负荷时间的动态刻画,可能导致因线路过快切除而引发连锁故障或因延迟切除而造成线路损坏。针对过负荷线路功率变化引起的动态热特性,分析了过负荷线路温升速度的影响因素,解析了线路允许过负荷时间的动态特征,进而提出了基于线路功率监测预估动态允许过负荷时间的自适应过负荷保护思想。通过建立线路动态热平衡方程,提出了预估线路动态允许过负荷时间的计算方法,从而提出了基于动态允许过负荷时间的自适应过负荷保护方法。仿真算例表明,该方法充分考虑了过负荷线路功率变化下的动态温升过程,能够在保证线路安全的前提下,最大限度地延缓线路的切除,有效降低连锁故障的风险。

As the scale of power systems expands and the interconnection extent and complexity of the power grid increase, the risk of overload-dominated cascading failures caused by line overload is increasing. Existing research does not take into account the dynamic changes of overload line flows, and lacks dynamic descriptions of the allowable overload time. This may lead to cascading failures due to too quickly cut or line damage due to delayed cut. In view of the dynamic thermal characteristics caused by a power change of the overloaded line, analyzing the influencing factors of temperature rise speed of the overload line, and the dynamic characteristics of line allowable overload time, an adaptive overload protection idea based on line flow monitoring estimated dynamic allowable overload time is proposed. Through establishing a line dynamic thermal balance equation, a calculation method of estimated dynamic allowable overload time is proposed. Then an adaptive overload protection method based on dynamic allowable overload time is proposed. The case study shows that the method fully considers the dynamic temperature rise process under a power variation of the overload line. It also delays the line removal time to the greatest extent and effectively reduces the risk of cascading failure thus helping to ensure the security of the line.