Research On Electromagnetic Transient Characteristic Of UHV Circuit Breaker In Reclosing Process

The development of the UHV transmission technology conforms to nation conditonsthat economy developed areas do not agree with energy-rich region. The UHV transmissiontechnology can not only realize long-distance transmission of large capacity, but also is thebasic skeleton of the future smart grid. Due to the special status of UHV power grid, so thesafety of the UHV transmission lines, and stable operation is extremely important. Highvoltage circuit breaker is an important equipment of ensuring safe and reliable operation ofthe system, so research of the open circuit characteristics of circuit breaker under faultcondition, and improving the breaking ability of circuit breaker has very importantengineering significance.In this paper, from the perspective of system, using the north of Zhebei to the west ofShanghai and Jindongnan to Nanyang two UHV transmission lines as the background, on thebasis of theoretical analysis, and the simulation model used for calculation is established.Transient recovery voltage before and after the reclosing of circuit breaker are studied.Based on a AC breaker reclosing open circuit fault of Yi min DC converter, the short-circuitcurrent zero drift problem of secondary breaking has carried on the detailed research.First of all, the first break after the fault before reclosing is studied. According to theprinciple of the circuit and KVL, transient recovery voltage characteristics of short line faultand terminal fault are analyzed. On the basis of the UHV single and double transmissionlines, circuit simulation models are established. Then transient recovery voltage of short linefault and terminal fault in two lines are studied, laying a foundation for the followinganalysis of secondary breaking features after reclosing.Secondly, according to electric field distribution under different separations in theprocess of action and the breakdown criterion, the gas critical breakdown field strength ofcircuit breaker contact clearance is obtained. Pre breakdown process of circuit breakercontacts in the process of reclosing is established. And according to the switch arc theory,simulation breakdown process, circuit breaker switching arc model is set up.In advance to join the breakdown process, transient recovery voltage of the secondarybreak after reclosing is studied, then compared with the first open characteristics. By theanalysis of transient recovery voltage characteristic of the different fault types and fault location, the worst of the transient recovery voltage peak and the rate of climb and thebraking measure are obtained.