In this study, the partial discharge (PD) characteristics of nonuniform electric fields in SF6 and SF6/N2 gases from PD inception to intermittent breakdown under negative dc voltage were systematically studied. The effects of the gas mixture ratio and electric field distortion on the PD characteristics were analyzed in terms of PD inception voltage (PDIV), PD amplitude, PD repetition frequency, and time-resolved PD (TRPD) patterns. The PDIV of SF6/N2 was higher than that of SF6 within a certain range of gas mixture ratios, which is related to the degree of electric field distortion. The greater the degree of electrical field distortion, the greater the range of gas mixing ratios, in which the PDIV of SF6/N2 was higher than that of SF6. The difference in the value of PDIV also increased with an increase in the degree of electrical field distortion. The PD amplitude and PD repetition frequency in SF6/N2 gradually increased with increasing applied voltage. Moreover, the smaller the SF6 content, the greater the PD amplitude and repetition frequency. In SF6, the PD amplitude significantly increased and the PD repetition frequency significantly decreased when the applied voltage increased to a high value. The shape features of the TRPD patterns in both SF6 and SF6/N2 changed with an increase in the applied voltage, but the change in SF6 was more obvious than that in SF6/N2.

Insulation and mechanical defects are the main reasons of the power equipment fault, the former could generate partial discharge (PD) which can be detected by acoustic emission (AE) sensor, the other one can be evaluated by vibration and temperature variation. However, the two defects are detected and analyzed independently in traditional detection, the importance of multi-signal interaction and fusion analysis is ignored. To realize multi-signal synchronous detection and associated analysis, and improve the accuracy and efficiency of state evaluation of power equipment, a novel integrated electronics piezoelectric (IEPE) AE-vibration-temperature combined intelligent sensor is proposed and developed in this paper. Reasonable structure design and components customization enable the sensor to acquire signals simultaneously. Meanwhile, integrated transducer electronic data sheet (TEDS) and data processing circuit intelligentize the combined sensor. The primary detection parameters of the sensor are acquired in the calibration experiments. In PD, vibration and temperature joint experiment, it is verified that the combined sensor is more sensitive and multifunctional. Besides, a new fusion analysis diagram, vibration-phase resolved partial discharge (V-PRPD), is proposed to characterise the correlation between PD and vibration.

UHF (ultra high frequency) method has been widely used in PD (partial discharge) detection for its high sensitivity. The resonance, distortion, and attenuation appearing in the propagation process of UHF signals in GIS (gas insulated switchgear) will influence the real situation of PD detection. Therefore, it is necessary to investigate the effect of GIS components such as disconnectors or high voltage conductors on the propagation characteristics of PD‐induced UHF signals in various voltage classes GIS. The factors of PD signals propagation characteristics in axial and radial directions are both analysed to avoid the effect caused by placement of sensor in this paper. First, the simulation models of GIS are built based on FDTD (finite difference time domain) method. Then the propagation characteristics of PD‐induced UHF signals are studied in the GIS with different disconnector gap lengths and different high voltage conductor radii. Finally, the reliability of the simulation results is verified by compared with laboratory tests. The disconnector gap and the change of conductor radii can both result in the signals attenuation which rises highest in the direction of 180°. The lower the GIS class voltage is, the larger the attenuation of signals after passing through disconnector gap is.

In this study, to improve the sensitivity and accuracy of the detection of surface partial discharge (PD) in gas insulation switchgears (GISs), a combination of ultra‐high frequency (UHF) and optical methods is proposed based on an integrated sensor. The PD triggered by a fixed metal needle defect attached to the spacer is detected from PD inception to flashover in a real GIS. The characteristics of UHF and optical signals under different applied voltages are compared and analysed in terms of PD waveform, Phase Resolved Partial Discharge (PRPD) pattern, PD count and amplitude. The results show that the surface discharge process can be precisely divided into three stages according to the combined characteristics of the UHF and optical signals. The comparison of the two detection methods shows that the optical method can detect the weak avalanche PD under low voltage while UHF cannot, so it can detect more PDs than UHF method in an AC cycle. In addition, with the deterioration of solid insulation material, the amplitude of the optical signal increases significantly while the amplitude of the UHF signal only increases slightly.

The gas state of the insulating gas significantly impacts the development and extent of the partial discharge (PD) in gas insulated switchgear (GIS). Correlating these two factors allows for a more comprehensive diagnosis of insulation defects. At present, the ultra-high frequency (UHF) method has been widely used for PD detection in GIS. However, measurements of the insulating gas’s state in the field are primarily conducted offline or at gas valves, providing ineffective data for reference. To address this challenge, this paper introduces a novel composite sensor capable of simultaneous UHF and gas state measurements. Building upon the disc-type UHF sensor structure, the composite sensor integrates a gas state sensing unit with the microelectromechanical systems (MEMS) sensor as the core. A robust shielding shell is designed through finite element simulation to ensure the safety of the sensor, with the maximum induced voltage and electric field strength on the sensing unit measuring 0.28V and 414V/m, respectively. The average UHF measurement sensitivity of the composite sensor reaches 13.3mm. In addition, the composite sensor exhibits low errors (±0.2°C, ±3kPa and ±10μL/L), high consistency and repeatability in temperature, pressure and moisture measurement. Finally, the composite sensor has demonstrated its capability to simultaneously and safely detect PD signals and the gas state within GIS.

Rogowski coil is the most common sensor for measuring alternating and impulse currents. At present, the coil has been used to measure the current with the frequency from Hz to GHz. Amperes law has been the basic of Rogowski coil measurement principle. However, Amperes law is just an approximate theory of full current theory when the frequency is low. Therefore, full current theory should be adopted instead of Amperes law to support the measurement of Rogoweki Coil under high frequency. In this paper, the exact expression of magnetic field through the coil based on full current is presented. Furthermore, the error between the result based on Amperes law and full current law is discussed. The results shown that the error will increase with the increasing of frequency and radius of coil. The error will be 10% when the frequency is 50 MHz and about 200% when the frequency is 1 GHz at the 0.3 m radius.