# A Fault Section Location Method for Distribution Networks Based on Divide-and-Conquer
## 1 Introduction  
Distribution network fault location is important in improving power system supply reliability as a prerequisite for fault isolation and power supply restoration [1; 2]. Modern power distribution systems mostly adopt multi-sectioned and multi-linked network structures so that faults can be limited to a smaller area to meet the increasingly demanding power supply service needs of electricity consumers [3]. However, the increase in the number of sections reduces the supply radius, resulting in insignificant differences in the magnitude of short-circuit currents in adjacent lines, which makes the fault location method based on the traditional three-stage current protection principle no longer applicable [4]. In the meantime, the problems of network scaling, distortion of fault information, and multiple faults in extreme cases also put higher requirements and challenges on the accuracy and speed of fault location [5]. Along with the construction of distribution automation and the development of communication technology, feeder terminal units (FTUs) and other intelligent monitoring devices have become popular [6]. The FTU installed at the intelligent switch can be equipped with fault current detection elements and adaptively adjust the action threshold of the fault current detection elements according to the operation mode of the system [7]. After a fault in the distribution network, the FTU compares the current flowing at the switch with the preset threshold to determine whether a short-circuit current is flowing at the switch, and it reports the fault detection results to the fault location decision host,which applies the fault location algorithm to identify the fault location [8; 9]. The basic working principle of the fault location method for distribution networks based on FTU fault information is shown in Figure 1. This method has the advantages of small data communication and convenient implementation, and it has gradually become the main means of fault location in medium-voltage distribution networks [10; 11]. Distribution network fault location methods based on FTU fault information mainly include four types: the first type is based on matrix algorithm fault location methods, the second type is based on intelligent optimization algorithm fault location methods, the third type is based on linear integer programming model fault location methods, and the fourth type is fault location methods based on hierarchical optimization models. 1. Matrix algorithm-based fault location methods for distribution networks. The basic principle of this method is to construct a fault discrimination matrix based on the topology of the distribution network and the fault information reported by FTUs and locate the faulty equipment via comprehensive analysis of the fault discrimination matrix [12; 13]. The matrix algorithm has the advantages of simple principles and fast calculation speed. However, in actual engineering, FTUs are usually installed outdoors and work in harsh environments, resulting in possible misreporting or omission of the reported information. When the fault information is distorted, the matrix constructed by the algorithm cannot correctly reflect the real fault situation, thereby causing the algorithm function to fail [14]. Reference [15] proposes using the adjacency of FTUs measurement points to correct the fault information. Reference [16] proposes introducing telemetry data to check the localization results. However, these methods are only valid for partial cases of fault information distortion [17], and the fault tolerance process of the algorithm additionally increases fault location time. With the expansion of the network scale, the number of FTU measurement points increases, and the probability of fault information distortion increases; thus, the method is difficult to apply to the fault location problem of large distribution networks. 2. Fault location methods based on the intelligent optimization algorithm.