Study On Wide-area Backup Protection Based On Differential Active Power And Sections Weighed Matching

Because of the enlargement of power system scale and power grid interconnection,the traditional protection faces many diff-iculties in setting and cooperation.Due to using only local measurement information,the traditional protection can't play the best effect with the development of power system.With the popularization and application of wide area measurement technology,it is a good way to use wide area information to identify fault accurately and ensure power security.Furthermore,the setting of wide area backup protection is relatively simple,and does not need to cooperate with time,so more and more attention of the experts and scholars has been paid by the wide area backup protection.In this paper,the structure of the wide area backup protection system is introduced firstly,and the principle of the existing wide area backup protection algorithm is summarized.The poor performance of the existing algorithms facing capacitive current,load current and fault resistance is analyzed,and also the fault tolerance of the algorithm when the number of error bits in the traditional protection starting signal is higher.A wide area backup protection algorithm based on differential active power is studied in this paper.One-bus-spaced-placement strategy is utilized to distribute finite PMUs.The grid is divided into several protection areas.By calculating sequence differential active power of each region and comparing with the threshold,the fault zone is identified.In the fault zone,the fault line is identified by the magnitude of the estimated voltage amplitude firstly,and the differential active power of each line is calculated when the amplitude of the estimated voltages is very close to each other.The difference between the differential active power of the fault line and normal line is analyzed,and then the criterion for the identification of fault line is given.Lots of simulation experiments on the IEEE39 test system verify that the algorithm can accurately identify fault line in various types of fault,in despite of distribution of capacitance and line load.Eventually,the algorithm in this paper can identify the fault line correctly when the transition resistance reaches to 300 Q.A wide area backup protection algorithm based on sections weighed matching is proposed in the paper.The line is divided into 5 sections broadly according to the setting range of traditional protection.The real protection vector and expected protection vectors for multi-section faults are constructed by using several kinds of wide-area traditional protections.The multi-section weighed fault matching function is established to calculate the fault matching degrees for five faulted sections.The detecting criteria and process are given.The simulation testing using enumeration method illustrates the validity of multi-section weighed fault matching and detecting algorithm.It has 100%accuracy rate under 5 bits error of wide-area protections.The influence factors for fault tolerance are analyzed on the choosing wide-area protections,as well as topological structure of power grid and the fault threshold.