Research on the Application of Smart Substation Area Protection

The outline of the national grid corporation's relay protection technology is proposed to study the substation area protection based on the multi-interval information of substation to improve the backup protection performance. In this paper, in order to reduce the action time of the line distance II period of backup protection, the location of line fault is identified by using the sampling at each interval for substation area and protection action information. Meanwhile, in order to avoid the action of backup protection to expand the power outage, this paper studies the scheme of identifying line longitudinal faults accurately and then trip faults rapidly by using analog information for substation area combined with fault line phase current characteristics. This paper also discusses how to distinguish the fault of high impedance grounding and the current secondary circuit break by using substation area information.

I. Introduction

With the expansion of power grid, the operation mode is changeable, and the backup protection is increasingly complex. A large number of applications for autotransformer, ultra-short circuit or short circuit group lead to the difficulty of whole setting and the insufficient sensitivity of remote backup protection. According to the principle of "strengthening primary protection and optimizing back-up protection", the capability to adopt the complex large networks by improving backup protection performance is studied. Due to the limited information, the stage backup protection which is according to the interval configuration could cooperate only depend on the protection of the fixed value and the action time, it is cannot be optimized in principle. Substation area protection is an important part of smart substation hierarchical protection^[1]–[2]. Based on smart substation network data sharing, substation area protection control device could achieve the functions of redundancy, optimization, supplementation and automatic control for protection in station, as well as the function of information interaction between multiple stations by comprehensive utilizing the information which contains the components for interstation multi-interval circuit, electric parameters, DO and local protection device status, etc.. At present, the protection of smart substation is mainly configured with the function of 110kV line backup protection, backup automatic switch and simple bus differential protection^[3]–[6], with low utilization level of substation area information mining. Others are basically the optimization of differential protection or backup protection by using wide-area information^[7]–[10], which is limited by the influence of synchronization and communication of sampling data between substations. This paper tries to make use of the substation area sampling and protection action information, also make comprehensive judgment combined with the fault calculation of line interval to achieve the purpose of optimizing the action speed for line distance backup protection. 220kV and above transmission lines are generally equipped with longitudinal fiber differential protection as the main protection.