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The extraction of current characteristics from the opening and closing coils is a crucial method for monitoring the state of high-voltage circuit breakers. Based on the waveform patterns of the opening and closing coil currents in high-voltage circuit breakers， the paper investigates a corner point extraction method of current waveform based on local thresholds of curvature scale space （CCS）. Subsequently， the characteristic curves of current at actual corner points are used to precisely monitor the mechanical state of high-voltage circuit breakers. Calculations based on the measured opening and closing coil currents from high-voltage circuit breakers in a specific substation indicate that the proposed local threshold method of the CCS can accurately identify the waveform features of the opening and closing coil currents. The mechanical state monitoring of high-voltage circuit breakers based on the characteristic curves of opening and closing coil currents shows excellent results. The research findings can provide crucial references for the mechanical state monitoring of high-voltage circuit breakers.

An increase in moisture content within GIS （gas insulated switchgear） can compromise its insulation integrity. To monitor insulation gas humidity inside GIS， a humidity sensor using dual-cone microfibers is developed. Firstly， utilizing beam propagation method （BPM）， the optical field of the dual-cone microfibers is simulated to investigate their field distribution and mode interference theory. This analysis reveals the correlation between SF6 and moisture content. Subsequently， the fused biconical taper （FBT） is used to fabricate the dual-cone microfiber humidity sensor and conduct humidity sensing experiments. Based on the experimental data， it is determined that the humidity sensor using dual-cone microfibers exhibits a detection sensitivity of -51.75 pm/%RH， enabling continuous online monitoring of humidity levels in electrical equipment.

Moisture ingress is one of the major causes of aging in oil–paper insulated transformers; the measurement of the moisture content of the insulating material is thus necessary during transformer disassembly for maintenance. One critical engineering consideration is the need for rapid and nondestructive moisture content measurement of the oil–paper insulation to minimize the power-outage time. Herein, a rapid characterization method for the moisture content of oil–paper insulation based on the dielectric response obtained using a microstrip petal-like ring resonator (MPRR) is proposed. The geometric parameters of the resonator and dielectric response model were established based on simulations and theoretical analysis. The geometry of the resonant ring was optimized by modifying the originally circular ring structure of the microstrip ring resonator (MRR) into a petal-like ring structure; this increases the number of resonant peaks from five to seven in the frequency range of 0.5–6.0 GHz for the same electrode area. The effects of the coupling mode, coupling gap, and microstrip ring size on the resonance characteristics of the MPRR were simulated and analyzed. Compared with the MRR, the MPRR has the advantages of a reduced fundamental resonant frequency and a smaller resonant-ring area that improves radiation efficiency. The impact of moisture content on the dielectric response of the pressboard obtained using the MPRR was studied. A moisture-calculation equation based on the measured dielectric response for a selected type of pressboard was established by the Lasso regression. The results of verification experiments show that the error of the proposed method is sufficient for practical applications. [ABSTRACT FROM AUTHOR]