配电网的安全距离:定义与方法

Security Distance of Distribution Network:Definition and Method

提出配电网安全距离的严格定义,并基于安全距离发展出新的安全评价方法。安全距离是当前状态(工作点)到安全边界的距离,是安全评价的关键数据。首先,该文规范了配电网安全距离的定义,将其分为几何安全距离(geometric security distance,GSD)和馈线安全距离(feeder security distance,FSD),并给出两者的计算公式。其次,分析了两种安全距离的物理意义:GSD能得到多个馈线负荷同时变化时的保守负荷裕度;FSD能够得到单个馈线负荷变化的精确负荷裕度。再次,该文全面分析了安全距离在安全评价中的用途,并提出了基于工作点位移的安全评价新方法。该方法利用新工作点的位移信息和原工作点的安全距离,能更方便快捷地得到新工作点的安全评价结果,适合实际运行中实时跟踪评价工作点的变化。最后,通过算例比较了GSD和FSD的计算结果以及两者在安全评价上的精度和速度。该文研究有助于对配电网安全距离的规范与深入认识,所发展的新方法使得安全距离可以更有效地用于在线安全评价。

The rigorous definition of the security distance in distribution network was proposed, and a new security evaluation method based on security distance was developed. Security distance of distribution network is the distance from the current state （operating point） to the security boundaries, and it is critical data for security evaluation. Firstly, a rigorous definition of security distance was proposed, in which two kinds of security distances were defined, including geometric security distance （GSD） and feeder security distance （FSD）. The calculation formulas were also presented. Secondly, the application of the security distance in security evaluation was analyzed. It is found that GSD can provide conservative security margin of multiple feeder loads; and FSD can provide accurate security margin of single feeder load. Furthermore, a new security evaluation method based on operating point displacement and security distance was proposed. This method uses both the displacement of the new point and the security information of the original point to obtain the security evaluation results of the new point. It is much faster than conventional security distance method, which is suitable for real time tracking and security evaluation for changing operating points in real operation. Finally, the results of FSD and GSD as well as the accuracy and speed of the proposed method are verified and compared in the case study. The research is helpful to understand the security distance of distribution network; and makes the security distance more efficient for online security evaluation application.