Research On Fault Location Method Of Distribution Network With High Fault Tolerance

In recent years,China’s power development plan has made a clear requirement that the investment focus of the power grid be shifted to the distribution network,and the working priorities be given to optimizing the distribution grid structure and enhancing the level of system intelligence;promoting the development of renewable energy to meet the needs of distributed power consumption demand;continuously improving the quality of power supply to ensure the use of electricity by the people on regular basis.As an important infrastructure directly supplying power to consumers,the distribution network is closely related to the production and life of the broad masses of people.Comprehensively improving the intelligence level of the distribution network and enhancing the safety and stability of its operation has become the current research focus.To this end,this paper has carried out the following work:In this paper,the control mode of distributed feeder automation is analyzed in depth,and on the basis of this,combined with the operating characteristics of distributed feeder automation,a recognition and storage scheme that adapts to the dynamic changes of the distribution network topology is proposed.In this scheme,the feeder terminal unit(FTU)performs information interaction through peer-to-peer communication to identify and obtain the topology information of the adjacent upstream and downstream FTUs,combined with its own topology information to form local topology information and eventually being stored.The scheme is not limited by the scale of the distribution network,as well has good flexibility.When the topology of any local distribution network changes,only the relevant FTUs need to be powered on to identify.In addition to topology identification technology,accurate fault section location is also one of the key technologies for distribution automation.Considering that in the distributed control system,each FTU being able to make decision independently,this paper draws on the faulttolerance principle in the Byzantine General problem,a causal relationship model between the feeder state and overcurrent information in algebraic form is established by exchanging the communication frequency for trust,and the possible fault section can be located by the decision information.This scheme rules out the effect of missed reporting of overcurrent information in principle,yet the fault tolerance performance for the distortion phenomenon of maloperation is not desirable.In aim of solving above-mentioned issue,this paper introduces Bayesian probability model to evaluate the possible fault sections,and the posterior probability is adopted to find the fault section that can perfectly explain the overcurrent information.The benefits of this method are that it tackles the problem of the centralized fault location being limited by the information transmission distance and the information processing capability of the master station,and for complex distribution networks with T-type coupling nodes,the fault segment location algorithm proposed in this paper can make accurate identification of single or multiple fault into realization.In terms of the high-permeability distribution network of Inverter-Interfaced Distributed Generation(IIDG),based on its controlling features and fault characteristics,a mathematical equivalent model considering IIDG control strategy is established,coming along with a new pilot protection scheme based on calculated fault current.This scheme merely needs to use the bus voltage to solve the calculated fault current injected into the bus,and on the basis of the criterion that the sum of the calculated fault current injected into the bus is not zero,to find the fault bus,and then locate the fault section,determine the fault type.The scheme eliminates the influence of IIDG’s capacity and access location from the protection principle,which is suitable for both distributed control systems and traditional centralized control system in distribution networks.The simulation results show that the scheme can accurately locate the faulty section and has a strong ability to withstand transient resistance.