| After the concept of ’Strong Smart Grid’ was put forward,the smart substation plays an important role of the smart grid construction.As an important component in the substation,the bus adopts a distributed protection scheme.Decentralized,in-situ,and digital sampling make it difficult to guarantee the data synchronization collected at each interval.The widely-used synchronization method based on a clock source heavily relies on the stability of external devices.Therefore,developing a protection scheme based on self-synchronization technology has profound meaning for distributed bus protection and smart substation protection.This article introduces self-synchronization technology to distributed bus protection,explores the development and application schemes of self-synchronization technology.And feasibility tests were conducted.The main work of the thesis is as follows.Analyzing the difference between smart substations and traditional substations,the advantages and problems of decentralized sampling.The differences in data acquisition,transmission processing and protection settings between distributed bus protection and traditional centralized bus protection are analyzed.A self-synchronization scheme for realizing the data synchronization of the bus protection is proposed.This scheme is based on the premise that the fault signal can reach the busbar intervals at the same time.Taking the fault time as the starting point of each interval data processing to achieve synchronization.This synchronization scheme does not rely on external synchronization clocks.It has high synchronization accuracy and reliability.Two kinds of fault-time detection algorithms were studied.The accuracy of the two algorithms was compared and analyzed.The possible error range is given and the feasibility of the application of fault-time detection algorithm in smart substation was verified.Proposing a self-synchronized implementation scheme for distributed bus differential protection.The specific implementation scheme of the self-synchronous bus differential protection algorithm in protection methods such as master and no-master station protection mode,direct mining direct jump mode,and net mining network jumping mode is described in detail.The concept of the minimum synchronization error allowing angle was proposed to characterize the synchronization error enduring capacity of the distributed bus differential protection.The specific relationship between the synchronous error angle and the differential current is deduced,descriping the influence of the synchronous error on the differential current.The theoretical values of the minimum synchronous error allowing angle under the various and combined influencing factors are obtained.The simulation verifies the accuracy of the theoretical analysis.The synchronization error allowing angle can be used to determine whether the synchronization error generated by each link is within the allowable range.It can also be used to verify whether the bus synchronization method can meet the bus protection requirements.Proposing a scheme for quickly determining the synchronization error allowing angle based on the busbar structure,which can provide a practical reference for the bus protection designer and the on-site operation personnel.On the platform of RTDS,using GTNET-SV module and GTNET board to achieve data collection,transmission and processing that meet the IEC6180-9-2 standard.A comprehensive simulation test was conducted on the accuracy of the fault time detection,the design of the self-synchronizing scheme for the direct sampling mode and the network sampling mode,and the synchronous error tolerance capability of the bus differential protection.The results show that the self-synchronization scheme proposed in this paper not only satisfies the requirements of distributed bus protection,but also satisfies the station domain protection,effectively solving the data out-of-synchronization problems caused by decentralized and in-situ sampling in smart substations. |
