Study on transient enclosure voltage generated by GIS operation and its suppression method

Abstract

TEV (transient enclosure voltage), with large amplitude and high frequency, which affect the normal operation of the GIS secondary equipment. This paper is based on the theory of multi-conductor transmission line. The coupled relationship among three phases was decoupled by means of phase-mode transformation method, thus the enclosure transmission characteristic model of GIS is established. On the basis of this, the GIS enclosure transmission characteristic model, the internal conductor transient circuit model and the grounding network transient model is combined. Taking an 1100kV GIS as an example, a complete GIS high frequency transient mathematical model is established. The transient enclosure voltage on the GIS is calculated according to the new high frequency transient model. The result shows that the maximum of the TEV values occurs on the shell of outlet line bushing or inlet line bushing. Moreover, the size of the grounding grid mesh and the number of ground lines is analyzed for the effect on the TEV peak. Under the same conditions, the results show that the smaller the mesh size is, the smaller the amplitude of the TEV is. Otherwise, increasing the number of grounding lead at the same point and earthed on many points can decline the peak of TEV, however, when the number of grounding exceed four, TEV amplitude reduction rate of less than 5%.