Study On Power Grid Wide Area Backup Protection Algorithm For Fault Identification

With the development of the power grid, the traditional backup protection whose decision is based on the local protection information is no longer adaptive to the complicated and volatile power grid operation mode. It is significant to make up for the weakness of traditional backup protection with the application of wide area backup protection. The wide area backup protection utilizes multiple node measurements to locate the fault component. Then according to the present protection and breaker conditions, wide area backup protection will remove the fault element as soon as possible in the minimal scale. This paper introduces the base theory of wide area backup protection, and then focus on the wide area backup protection algorithm for fault identification. The main work is as follows.In the first part, a wide area backup protection algorithm for fault line identification is proposed which takes account of both direction information and distance information of local line as well as the adjacent lines to locate the fault element. Furthermore, the differential protection and over-current protection information of the adjacent transformers are used to help identifying the fault. Firstly, correlation matrix according to the topological relationship between lines and the IEDs is defined. Secondly, the association weight factor is set. Thirdly, the integrated protection values are calculated. Finally, the fault line can be located by the comparison of the integrated protection value and the fault threshold value of each line in the scope. In this paper, the IEEE5-generator14-bus system is taken for example to verify the correctness of the proposed algorithm. Different fault conditions contain transformers and ring networks are taken into considering respectively. Afterwards, enumeration method, tolerance factor and Monte-Carlo method are respectively used to study the fault-tolerance performance of the proposed algorithm. The results show that the proposed algorithm is simple and reliable with good fault-tolerance performance.In the second part, a wide area backup protection algorithm for fault bus identification is proposed which make use of the electrical measurements and protection information. The algorithm utilizes bus sequence voltage and line sequence current phase, and also both direction information and distance information of the adjacent lines to identify the fault bus. In this paper, the IEEE5-generator14-bus system is taken for example to verify the correctness of the proposed algorithm, the simulation model of PSCAD/EMTDC is built to test the validation of algorithm in the condition that the fault component is a bus or a line.