Simulation and measurement of PD-induced electromagnetic wave leakage in GIS with metal belt

Abstract

Analysis of the transmission and leakage characteristics of partial discharge (PD) signal in Gas Insulated Switchgear (GIS) is of great importance for PD detection. Traditional connector of two GIS tanks is a disc insulator, so the leakage of PD signal is easily detected. Recently, to improve the performance of GIS, the disc insulator is often sealed by a metal belt and an aperture is made in the metal belt for PD detection. The leakage of PD is weak and the PD detection is delicate. This paper is devoted to the theoretical and experimental study of the transmission and leakage characteristics of the PD signals in such GIS. The electric field in the GIS and the characteristics of the leaked signals are simulated with software Ansoft HFSS. The PD source is assimilated by two simple models: "line feed" and "waveguide feed". The simulation results show that the frequency band and amplitude of the leaked signals depend on the size of the aperture and the distance of the detector from the GIS. A novel ultra wideband planar antenna is developed and a full experiment setup is built to validate the simulation and to test the characteristics of the leaked PD signal. The transmission coefficient S 21 has been measured with a vector network analyzer. The experimental results correspond better to the simulation data with "line feed" than "waveguide feed". But the prediction of the frequency characteristics by the dipole model is very different from the experiment results in the high frequency domain. Furthermore, we show by the experiments that the amplitude and frequency profile of the transmission coefficient S 21 is sensible to the position of the PD source in the GIS.Index Terms -Electromagnetic leakage, gas insulated switchgear (GIS), partial discharge (PD), transmission coefficient.

On the Electromagnetic Wave Behavior Due to Partial Discharge in Gas Insulated Switchgears: State-of-Art Review

“…Thus, the outer tanks of GIS do not provide perfect grounding for the EM waves since tanks are not perfect coaxial waveguides. In the event of PD, such configuration would result in leakage of EM waves outside the tank [9]. The apertures act as slot antennas allowing the electric field to propagate outside the tank at resonance frequencies.…”

“…Recently, the use of basin-type insulators with an external metallic cover is prevalent. Such spacer type provides better grounding for the GIS tank, prevents spacer corrosion with air, and reduces EM waves from leaking outside the tank in the event of PD [9], [39].…”

“…For bush type Spacers, EM waves can easily leave the tank through the dielectric spacer [9]. S. Kaneko et al [75] built a FDTD model for a GIS with slits formed by the bolts connecting the GIS tubes together.…”

“…Different kinds of external sensors are used to detect the event of PD. The most commonly used types of external sensors are the bi-conical log periodic antenna, Horn antenna, loop antenna, dipole antenna, and some kinds of planar antennas including Fractal antenna, patch antenna (asymmetric and symmetric), and Spiral antenna [9], [39], [74], [77], [78]. Horn antennas have higher sensitivity at high frequencies whereas log-periodic antennas have better sensitivity at low frequencies.…”

“…GISs are widely used in power system utilities because of the high reliability, safety, robustness, environmental aspects, and reduced space [9], [10]. Such devices have been commercially introduced in the 1970s and are widely used in substations.…”