Font Size: a A A

Study On Wide Area Protection System Structure And Fault Determination Algorithm

Posted on:2006-11-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:W CongFull Text:PDF
GTID:1102360182476842Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
With the implementation of development stratagem about "transmit electricity from west to east, north supports power supply to south and vice versa, connect power grids nationwide", three huge interconnected power girds in north, middle and south of China will come into being. The situation of large scale power girds and long transmission distances are new problems brought forward for relaying protection system and stability control system, which must operate more efficiently and reliably than ever before to meet high requirements. Effective relaying protection and stability control system should not only protect electrical devices from being damaged by fault, but also protect power from collapse by severe disturbances. They are the most important protective measures for large scale power grids to operate stably and reliably.Stability control measures known as famous "Three Defensive Lines" in China has been brought into effect sine 1980's and achieved excellent operation results. Several large scale blackouts have been avoided and plenty of experiences to insure power grids operate stably and reliably have been accumulated. With the enlargement and interconnection of power grids, traditional "Three Defensive Lines" is difficult to meet higher requirements than before. Because traditional "Three Defensive Lines" are formed by several unaided relaying protection and stability control measures, which operate based on local electrical quantities and without necessary cooperation each other. In sometimes, relaying protection or stability control measures operate correctly, but power grids will lose its stability. A wide area protection system to meet the requirements of "Three Defensive Lines" is proposed in this thesis. The definition of this wide area protection system is proposed from the point of view in functions it should possess. Some critical issues of system structure, functions configuration, communication system and so on about this wide area protection are discussed. The wide area protection system proposed in this thesis combines traditional "Three Defensive Lines" with emerging conception of wide area protection system, operatesbased on wide area information, and reflects power system operation status dynamically and factually. A wide area protection system to meet the requirements of "Three Defensive Lines" integrates functions of traditional "Three Defensive Lines" into one system to achieve cooperation and harmony among every defensive line. The control goal of this wide area protection system is to prevent power system from being collapsed when suffering from sever disturbances with optimized protection and control measures, that is reduce disturbance affected area and blackout times.A wide area relaying protection algorithm based on longitudinal comparison principle is proposed. By executing this algorithm based on fault direction information of wide area IEDs near fault, the fault site can be easily located and effective tripping strategies can be implemented. Wide area relaying protection system adopts distributed structure, fault locations algorithm is implemented in IED. After fault occurrence, every IED near fault site knows where the fault locates correctly. IED can provide not only fast primary relaying protection functions, but also fast backup protection functions. The selectivity of wide area relaying protection system is achieved based on wide area fault information instead of different operation time delay. So it is convenient to set setting values and operation time delay for relaying protection functions.A wide area relaying protection algorithm based on current differential principle is proposed. The current differential theory in wide area relaying protection system is the same with ordinary one, the difference is that the former utilizes wide area current and can provide current differential protection for wide area. Because current differential theory has better performances than the other theories, wide area current differential relaying protection system can provide protection functions with excellent performances. In order to lighten the pressure of communication caused by transmitting large quantities of analog sampling data as well as guarantee the rapidness and reliability of wide area relaying protection system, "Searching Method" is proposed to determine protection zone and associated area for IED. Protection zone and associated area can change according to topology of power grids. When faultoccurs, 1 ED exchanges fault current only within its protection zone with its assoeiated IEDs.The concept of "N-l" in relaying protection system is proposed by referencing that concept in power system analysis field. "N-l" in relaying protection system mainly contains protection miss operation, maloperation, circuit breaker failure and communication system failure, which will damage the performance of relaying protection system. The strategies against relaying protection system "N-l" status are discussed. Some special problems exist in relaying protection systems are analyzed and resolving measures are proposed based on wide area information. The performances of these two wide area relaying protection systems are compared.GSE (Genetic Substation Event) and SAV (Sampling Analog Values) models in IEC61850 are studied. They are proposed to apply in transmitting fault direction information in wide area longitudinal comparison relaying piolection system, and fault current information in wide area current differential relaying protection system.Ethernet is proposed to accomplish communication functions in substation LAN. In order to investigate the performance of Ethernet, special communication system simulation software —OPNET (Optimum Network Performance) is utilized to .simulate some critical parameters such as Ethernet delay, data diagram dropped, network traffic under typical communication environment. Simulation results show that Ethernet is sufficient to act as communication system in wide area protection system.Project supported by National Natural Science Foundation of China (50477041) and Xuji Electric Power Special Foundation.
Keywords/Search Tags:Three defensive lines, wide area protection system, longitudinal comparison principle, current differential principle, "N-l "in relaying protection system, IEC61850, communication, Ethernet, OPNET
PDF Full Text Request
Related items