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Research On Predigesting 220-500kV Transmission Line Protecting Scheme And Regulations Of Backup Relay Coordination

Posted on:2008-12-01Degree:MasterType:Thesis
Country:ChinaCandidate:L CaiFull Text:PDF
GTID:2132360272968877Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
Protection Relays are the basis of safeguarding modern large scale power grid. Backup relays'functions are operating when main relays fail to operate. The latest regulations of backup relays'coordination were published in 1994, when micro-computer relays were regarded as high-level relays. Now, they're just basic protecting scheme for high-voltage transmission line. The importance of backup relays has been declined, so the protecting scheme and coordination regulations of backup relays should be changed corresponding to this situation. This paper studied on predigesting protecting scheme and regulations of relay coordination.This paper made a summery of developmental history and status quo of protection relay in power grid, explained the importance and feasibility of predigesting back-up protecting scheme and coordination regulations. On this basis this paper analysed the settings of backup relays. The Xibei Rigional 330kV power grid was taken as an example to demonstrate the defects of current coordination regulations with practical statistics. And the coordination regulations of Jiangxi, Guizhou, Yunnan, Xibei and Hebei provincial power grid are compared in order to learn from others'strong points to offset one's weakness.This paper introduced domecratic situation of predigesting coordination regulations, include several grids'practical regulations in detail and their performance.This paper proposed a novel method for caculating coverage of zero-sequence relays based on node impendance matrix. A node impedance matrix has a smaller change than a node admittance matrix when the network topology changes. This algorithm uses this advantage of node impedance matrix, directly derives the analytic function of protect coverage corresponding to failure of the system. This algorithm can get a more precise result through less calculation, and needn't special treatment when some related lines are mutual inductance lines. This method can improve settings'performance and make it more convient for coordination between inhomogeneous relays.Based on conclusions of previous chapters, the paper listed several schemes of predigesting zero-sequence relays, analysed both advantages and disadvantages of each scheme, resolved coordinational problems between zero-sequence relays of transformers and transmission lines after predigestion. This paper also analysed principles and regulations of distance relays, introduced apparent impendance caculating method, proposed a scheme of predigesting distance relays and emphasized on strengthening supervisory measures after predigestion.Finally, this paper briefly discussed the principles of inverse-time relays, including types, characteristics and domestic situations of inverse-time relays, researched on setting inverse-time relays and coordination between inverse-time and definite-time relays, proposed a new protecting scheme which combined inverse-time and definite-time relays, and validated its feasibility through a sample.
Keywords/Search Tags:Protection relay, Setting calculation, Predigest coordination regulations, Inverse-time relay
PDF Full Text Request
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