A Novel Wide Area Backup Protection System

According to recent studies,the mal-operation or fail-to-trip of protection is determined as one of the origins to raise and propagate major power system disturbances. Backup protections in fault clearance system have the task to operate only when the primary protection fails to operate or when the primary protection is temporarily out of service. The recent complexity and enlargement of power systems makes it difficult to coordinate operation times and reaches among relays especially. In the existed relay protection system,mal-operations of backup protection contribute a lot to system security and stability;furthermore,they are main reasons to system cascade tripping.To solve this problem,an intelligent analyzing and controlling function is added to key process of protection functionality. Therefore,a novel wide-area backup protection system is reported in this paper.First,the background of the paper is described,based on analyzing the disadvantage of traditional backup protection, a novel way to solve the problem is put forward. Then,some key problems in making wide area backup protection are described. To treat with large quantities of information in wide area backup protection,an information fusion system is designed,which has three layers: data layer, character layer, strategy layer,and data flows from data layer to character layer,then to strategy layer.Furthermore,D-S theory is utilized to deal with incorrect,inexact and lost of data. In the proposed backup protection system,the fault unit is selected in virtue of conventional pilot relay protection,and the fault location functions are made up of some kinds of line directional components. Such as negative sequence,zero sequence component direction function and impedance direction function,With the components, the fault unit is deduced. Detail characteristics of the three direction functions are being analyzed,simulation result validates the correctness of the design.Furthermore, a novel decision-making system is put forward for wide-area backup protection system based on CORBA and hybrid MAS system,MAS and CORBA technique is utilized, to realize control and coordinate inside the system on time,moreover,mobile agent is adopted to send or get data from other part of the system. The configuration and function of each agent is described. Service functions in CORBA make each part of the proposed system communicate each other.The communication system for wide area backup protection system is also designed, the system is made up of switching system,router and optic-fiber networks. Measures are taken to make the queue delay of the proposed system as small as possible,and reduce the delay in the network node and prevent data from being abandoned. So TCP and UDP protocol are employed in transport layer. In order to realize perfect QoS,the MPLS/Diffserv network can be utilized in wide area backup protection. Network simulation is made, the delay time of the result can be accepted by wide area protection system.Based on the above researches, the detail structure and function design of the proposed wide area backup protection system is described. The proposed system comprises a master system and several local units. The system is arranged as three layers. The bottom layer consists of PMUs with additional protection functionality. The next layer consists of several Local Backup Protection Centers (LBPCs) , each of which interfaces directly with a number of PMUs. The top layer, System Backup Protection Center (SBPC), acts as the coordinator for the LBPCs. Connected together via fiber-optic communication links, these devices can process intelligent algorithms based on data collected locally. Local part of the proposed wide-area backup system samples vital signals for backup protection system,and then deliver pre-processed results to SBPC via fiber-optic communications between the substation and SBPC. Based on the precise location of the fault,SBPC makes a strategy in several ways to guarantee the global security of the protected region, including coordinate with breaker failure strategy, overload strategy, reclosing strategy and so on. LBPCs perform the correlative operations on the spot, and then fault will be isolated rationally. Based on the dynamic experiment data, the superior performance of the proposed technique is validated in regard of the speed of response, computational burden and reliability.At the end of the thesis,the whole paper is summarized and some future work is discussed.