Research On The Electromagnetic Transient Problems With Their Effect Caused By The Operation Of Discnnector In GIS

With the constantly development of power system, our nation has proposed a project of ultra-high voltage transmission to meet the demand of large capacity and far distant transmission. The research of UHV transmission and transformation power system has strongthened the efficient utilization of source and rational layout of power grid, which is benefit for long-term development of power grid and operation of security, stability and economy. In order to supply the theotical support and data reference for the construction and operation of UHV substation in the future, one of critical problems in UHV project that the electromagnetic transient problem caused by the operation of disconnector is reaearched sysematiclly in this paper.This problem was clarified from two aspects that the transient occurred inside of GIS and outside GIS based on the features of the problem.The equivalent calculated models of lumped parameter appliances and distrbuted parameter appliances were derivated in their transient characteristics. The inner transient circuit of GIS was modeled according to the running mode of GIS and operation style of DS. The coupled relationship among three phases was decoupled by means of multi-conductor transmission model and phase-mode transiformation method, thus the enclosure transmission characteristic model of GIS was set up with its layout. By connecting inner transient circuit of GIS with enclosure transmission characteristic model of GIS, an integral transient model of GIS was obtained. The effect of some factors that the residual voltage on unoperated bus and other ones on VFTO of operated phase was studied,too. Results demonstrated that VFTOs calculated on ondition of considering enclosure transmission characteristic model of GIS was more apprximate to actual ones, whose high frequency was somewhat broader than those of calculated on iglected enclosure transmission characteristic model of GIS, but the basic oscillation frequency was nearly the same on both of the two conditions. The residual voltage on unoperated phase may impact on VFTO of operated phase, but not all the values of VFTO on each point increaed with the increment of residual voltage on unoperated phase.Secondly, the transient enclosure voltage rising caused by the operation of disconnector was calculated on the basis of enclosure earthing styles, and its influencial factors were also analyzed. Eventually,the VFTC and TEV were analyzed by comparison, then the passways of electromagnetic interference were discussed, and some measurements to resist the transient electromagnetic interference were proposed. The TEV values were varied with distinct operation styles of disconnector,the maximum of which reached about 50kV occurred on the earthing point of outlet line bushing or inlet line bushing with its main frequency ranged from 1～8MHz. The magnitudes of TEV on outlet line duct were symmetric for the symmetric layout of GIS. The TEV caused by operation phase B DS is higher than that of caused by operation phaseA DS when the three phases enclosure configured horizontally. Both of increasing the nrmber of grounding lead at the same point and earthed on many points can decline the peak of TEV, however, when the number of grounding lead exceed two, it can't get a good effect to let the TEV go down.