Study on the impact of VFTO electromagnetic interference on electronic transformers in 500 kV GIS substation

With the widespread use of the gas insulated switchgear (GIS), the harm of very fast transient overvoltage (VFTO) caused by the disconnecting switch (DS) and the circuit breaker (CB) operation becomes increasingly obvious. One 500 kV GIS smart substation is used as a prototype to study the impact of VFTO electromagnetic interference on electronic transformers in 500 kV GIS substation. Base on the noise source and the transmission pathway, a noise coupling model has been set up in order to analyze the VFTO electromagnetic interference on electronic transformers qualitatively. It has been found that the decrease of the coupling capacity of transformer, i.e. CL, and CN, will contribute to the low noise coupling effect of VFTO. The conclusion shows that the most effective method for interference reduction is to revise CL, CN in the low frequency and add low band filter and shielding box in the high frequency. It has been proved by experimental data that the VFTO maximum amplitude is reduced from 9.9 kV to 0.61 V by using this method. © 2016, The editorial office of Transaction of China Electrotechnical Society. All right reserved.