| Disconnector switching operation will produce complex electromagnetic transientphenomenon in GIS, part of the electromagnetic transient process occurred in the interiorof GIS produce very fast transient overvoltage(VFTO),another part of theelectromagnetic transient process occurred external overvoltage between the GIS shelland the earth,which affect GIS secondary monitoring,measurement, protection and otherequipment work properly,that is transient enclosure voltage (TEV). GIS voltage level isgetting higher and higher, the insulation problems caused by VFTO and TEV get moreand more attention. In-depth study to the VFTO and TEV problem is an important issueto ensure the safe operation of the substation, and it has important guiding significance onUHV GIS substation forward construction and operation.Currently, limited by test and the actual experimental conditions，the primary meansof researching VFTO and TEV is computer simulation. In the process of VFTO andTEV simulation, building a complete、accurate transient model will improve transientvoltage calculation accuracy. This paper fouses on study from the following aspects:Discussing effect of disconnector parallel resistance on VFTO amplitude, frequencyand rise time, and discussed in detail the fast and slow GIS disconnector parallelresistance heat capacity, pointe out that disconnector is installed resistance also needs toconsider the actual situation of the substation、switch operating speed and resistance heatcapacity; Research the effect of disconnector operating speed on the residual charge andrekindle number, also pointe out that the disconnector operating speed has impact onthe arc pre-breakdown and arcing time characteristics.In computational process of VFTO,it is the critical factor that accurate description toarc produced in the process of disconnector operation,which has a great deal of effect onthe calculaton precision of VFTO. Dynamic arcing model was presented based onsegmental arcing model. In the pre-breakdown stage, hyperbolic resistance was used in themodel to consider the impact of breakdown delay time on VFTO waveform; in the extinction phase, complete Mayr model was established to describe the dynamic physicalprocesses of arc. Taking1100kV station as an example, paper calculated the amplitude,frequency and gradient of VFTO on the condition of two arcing models, and discussed theinfluence of breakdown delay time to VFTO waveform. It is found that VFTO has highermagnitude, higher frequency and higher gradient under dynamic arcing model; breakdowndelay time affects the initial rise time and amplitude of VFTO. By comparing simulationresults with the measured data, it is found that dynamic arcing model is the furtherimprovement of segmental arcing model and has great significance for improving theaccuracy of VFTO simulation.On the basis of dynamic arc model, paper discuss from thegap breakdown, high-frequency arc extinction criterion,building GIS disconnect switchingarc model to reflect repeatedly renewed, and simulate to VFTO based on this model.Due to high frequency effect, The MOA transient process is very complex,so it isnecessary to conduct in-depth research. The accuracy of MOA model is particularlyimportant, Currently,MOA electrical model under VFTO has not yet reached aconsensus. Based on analysising commonly MOA model, full consideration of thedynamic characteristics of the MOA in the high-frequency steep wave, this paperestablish the MOA dynamic transient model under VFTO. Taking UHV GIS substationas example, paper study the efftec of the MOA polarization model and the dynamictransient model to VFTO。The results show that, on condition of MOA dynamic transientmodel, VFTO has lower peak and increased high-frequency component and the shortestduration, and it is more suitable for VFTO simulation modeling.On the basis of theory of the multi-conductor transmission lines,GIS externaltransient model is modeled, combining with internal GIS model and The transient groundnetwork considered the mutual inductance role,this paper establish GIS overallsimulation model, On the one hand, the maximum values and spectral characteristics ofVFTO and TEV are analyzed in details. By comparison with the measured waveform,show that the simulation results on condition of GIS overall model are closer to the actualresults. Detailed analysis of the main TEV factors,put forward corresponding suppressionmeasures,it play a guiding role in the design and installation of GIS substation. |
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