Research On GIS External VFTO Measurement Method Based On Differentiating–Integrating Principle

Compared with the traditional Air-Insulated Substation?AIS?,the fully enclosed Gas-Insulated Substation?GIS?filling with SF₆ insulation medium has a small footprint,good insulation,high safety factor,and arc extinguishing.These characteristics make it widely used in modern substations.However,operating equipment such as disconnect switches and circuit breakers can generate very fast transient overvoltages?VFTO?,which seriously affects the safety of GIS internal and external equipment.Accurately detecting VFTO is the first step for researchers to reduce the harm caused by VFTO.Existing VFTO sensors are generally large in size and complicated to install,and need to modify the GIS structure,which cannot be installed on existing GIS equipment.In order to solve the above disadvantages of complex VFTO sensor installation and the need to reform the GIS structure,a miniaturized external VFTO measurement system based on the principle of capacitive voltage divider and differentiating–integrating measurement system was developed in this thesis.Based on the equivalent circuit of the sensor and the differentiating–integrating circuit,this thesis analyzes the main factors that limit the bandwidth of the measurement system.The special sensor structure design and optimization of the arrangement of the differentiating–integrating circuit components increase the bandwidth of the measurement system.Meanwhile,a calibration platform for the voltage division ratio calibration and a ns-level pulse generator are designed.In the laboratory environment,the miniaturized VFTO measurement system developed in this thesis is calibrated by frequency-domain sweep calibration experiments,time-domain square-wave calibration experiments,and voltage division ratio calibration experiments.A comparison test was carried out with the built-in VFTO sensor of the standardized high-voltage calibration platform of Yunnan Power Grid Co.,Ltd.According to the results of calibration experiments and comparative experiments,the developed miniaturized VFTO measurement system has a power frequency division ratio of 1:49881 and a±3 d B bandwidth of 50 Hz to more than 100 MHz.Both dynamic and static characteristics meet VFTO measurement requirements.This measurement system was used to measure VFTO in Dali 500 k V substation GIS under specific conditions.The measured time and frequency domain waveforms conformed to the definition of standard VFTO in GB/T 18132.1.Test results show that the measurement system meets VFTO measurement requirements and can be applied to actual VFTO measurement.