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Very fast transient overvoltage (VFTO) generated by an operating disconnector is one of the main reasons for electromagnetic disturbance in gas-insulated switchgear (GIS) substations. Generally, the amplitude of VFTO can be used as one of the references for the insulation design of GIS primary electric power equipment, so it is necessary to obtain its accurate amplitude. In this study, a new VFTO measuring sensor is developed and its measurement performance is demonstrated through hundreds of operations by a disconnector in a 220 kV GIS test circuit. The validation shows that the low cut-off frequency of the new VFTO measuring sensor has been greatly expanded to 0.01 mHz, which is improved by about 50% compared with the old sensor. The measurement accuracy of amplitude of VFTO micro-pulse improves greatly by about 80% compared with the old one. Thus, the new VFTO measuring sensor can fully meet the measurement needs of trapped charge voltage, power frequency voltage, and high-frequency transient voltage in VFTO waveform. It can be used to provide more accurate data support for insulation design of GIS primary power electric equipment in extra-high voltage (EHV) and ultra-high voltage (UHV) GIS substations.

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In the lightning impulse test, the 10 kV fusion voltage transformer intelligent component acquisition port often suffers from functional failure or breakdown. In this paper, experimental measurement and inversion calculation were used to study the electromagnetic disturbance level of smart component acquisition port. During the inversion calculation, the applicability of the dual exponential function model, Heidler function model, and impulse function model as the primary source for describing the lightning impulse device were compared and analyzed. The results show that the double exponential model was used as the calculation source of the primary side lightning waveform, and the inversion calculation results were in good agreement with the actual measurement. In addition, the effects of the primary side lightning voltage peak, wave head, and wave tail parameters on the maximum amplitude of the disturbance waveform calculated by inversion are discussed and analyzed. Based on the analysis results, a sufficient inversion calculation parameter was proposed to estimate the disturbance level of the intelligent component acquisition port. Finally, the measured results were compared and discussed with the IEC 61439 assessment level, and it was suggested that the assessment level of fusion equipment should be modified. INDEX TERMS Electromagnetic interference (EMI), lightning impact test, inversion calculation, port disturbance voltage, smart component, lightning model.

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