Abstract
Disconnect switch and circuit breakers operations in gas insulated switchgear (GIS) systems may produce very fast transient overvoltage (VFTO). Detecting VFTO is the first step for researchers to reduce the damage to other equipment of the substation caused by VFTO. Most of the existing sensors used for VFTO are generally bulky, complex to install, and require modification of the GIS structure. In this paper, a miniaturized measurement system that uses capacitive voltage divider and differentiating–integrating circuit is proposed. A special sensor structure and optimized differentiating–integrating circuit components arrangement were designed to increase the bandwidth of the measurement system. The frequency-domain, time-domain and voltage divide calibration experiment was performed, and a comparison experiment with an internal VFTO sensor was conducted. The measurement system was applied in the 500 kV GIS substation, and the VFTO measurement under specific conditions was carried out. The measured time domain and frequency domain waveforms conformed to the definition of standard VFTO according to IEC 60,071. It was found that the proposed measurement system meets VFTO measurement requirements and can be applied to actual VFTO measurements.
Highlights
Gas-insulated substation (GIS), an equipment filling with SF6, has been widely used in power systems since the 1960s
According to IEC60071-1, the frequency component of very fast transient overvoltage (VFTO) is composed of three parts: (1) in the GIS HV busbar, a very high frequency component formed by several slight changes in wave impedance, up to 100 MHz; (2) at the end of the GIS HV busbar and the end of the cable or overhead line, the high-frequency component formed by the significant change in the wave impedance causes reflections up to 30 MHz and (3) low-frequency components caused by external large-capacitance equipment resonance ranging from 0.1 to 5 MHz, such as capacitive
This paper focused on the design and optimization of the VFTO measurement system
Summary
Gas-insulated substation (GIS), an equipment filling with SF6 , has been widely used in power systems since the 1960s. For the GIS hand hole method, it has the advantages of wide frequency band, it needs to modify GIS structural that is put into operation, and the modification process is complicated, which is not allowed by the power department. After the system is tested and verified, we compared it with a standard internal VFTO sensor to confirm the system meets VFTO measuring requirements, and a field measurement in 500 kV Dali Substation is done. The parameters of this measurement system are not affected by the installation method, and the frequency band is similar to the internal sensor, which can accurately measure the VFTO signal. This paper has five parts: Section 1 is the introduction; Section 2 is the design, optimization and simulation of the measurement system; Section 3 describes calibration and verify of the measurement system; Section 4 shows a field test to measuring VFTO signal using this measurement system and Section 5 presents the conclusions
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