Abstract At present, gas-insulated switchgear (GIS) is extensively employed in the power system. However, there is currently a lack of effective monitoring methods for the discharge phenomena caused by tiny defects on the surface of its basin insulators. As a non-electrical detection technology, the optical detection method is ideal for detecting discharge phenomena in low-light environments inside GIS. This paper constructs a structural model of a linear GIS, uses optical simulation software to study the optical signal propagation characteristics of different discharge sources on the insulator surface inside the GIS, and proposes the requirements and arrangement methods of optical sensors for detecting weak discharges inside the GIS. The research results show that in linear GIS, the total radiated light power of the spherical light source close to the pressure equalizing cover on each detection surface is significantly lower than other light sources, and the farther the distance between the detection surface and the light source, the more obvious the attenuation of the optical signal. Based on the propagation characteristics of optical signals, a deployment strategy and sensitivity requirements are proposed for the optical sensor installed at the central position of the linear GIS chamber. The research conclusions of this article provide an important reference for the application of optical sensors in detecting internal defect discharges in GIS.

The ethylene-propylene-diene terpolymer modified with norbornene serves as a critical insulating material for high-voltage direct current cable accessories. However, due to its inherent non-polar characteristics, ENB-EPDM exhibits limited processability, thereby necessitating polar grafting modifications to improve compatibility and processing performance. Conventional grafting approaches, although effective in enhancing processability, often introduce polar functional groups that may compromise the material's electrical insulation properties, thus presenting challenges for HVDC applications. This study systematically evaluates the influence of three distinct polar grafting agents (acrylic acid, methyl acrylate, and glyceryl monooleate) on the electrical performance of ENB-EPDM. Quantum chemical analyses were conducted to investigate the molecular behavior of the grafted materials under applied electric fields. The results indicate that GMO-grafted ENB-EPDM exhibits a larger frontier orbital energy gap under strong electric fields compared to the unmodified polymer. Furthermore, infrared spectroscopy analysis reveals a blue shift in the carboxyl stretching vibration peak of the grafted system under identical field conditions, suggesting enhanced molecular structural stability induced by polar grafting. Notably, the strategic incorporation of GMO not only improves processability but also preserves and enhances electrical insulation performance by optimizing the electronic structure of ENB-EPDM. These findings provide a robust theoretical foundation for the design and development of advanced insulating materials for high-performance HVDC cable systems.

To improve the measurement accuracy of direct current (DC) electric field measurement devices in ion flow fields, it is necessary to consider the impact of space charges on the calibration of DC electric field measurements. In this paper, a simulation model of a DC electric field generation apparatus involving space charges is established based on the dilute material transfer principle, and the influence of the applied voltage and gap distance of the apparatus on the calibration results of the DC electric field measurement device is analyzed. Limitations on the electric field calibration of the generation apparatus in the presence of high electric intensities are identified and discussed. The electric field intensity relative error at different gap distances increases as the electric field intensity increases, and an optimal calibration electric field level and an optimal calibration position are identified, both of which increase with an increase in the gap distance.

Defects in GIS can be effectively detected by detecting the partial discharge (PD). The common methods of detecting partial discharge are pulse current, ultrasonic and UHF (ultra-high frequency). However, the results of different methods may be different due to the different physical quantities detected. It is important to research the differences between the PD detection methods for the PD detection and analysis. In this study, we designed metal protrusion defects in GIS, including protrusion on the conductor and enclosure. Then, we detected the PD of defects using pulse current, UHF and ultrasonic methods at the same time. The PRPD patterns, maximum discharge amplitude of different defects and PD inception voltage (PDIV) detected by the three methods were analyzed. The PRPD patterns and discharge amplitude of the different methods were very similar to each other, but the PDIVs were different. It can be concluded that the process from the PD inception to breakdown can be divided into four sections based on the PRPD and the maximum discharge amplitude. The similarity between the three methods is because their signals are all related to the pulse current during the PD process, and differences in their PDIVs are caused by the differences in sensitivity. The sensitivity of the pulse current is the lowest among the three methods due to its poor anti-jamming capability. The sensitivity of UHF is higher, and that of ultrasonic is the highest.

Based on the finite element simulation software, the magnetic field-structure force field simulation model is established to obtain the magnetic field and stress distribution around the reactor; the calculated Maxwell force and magnetostrictive force of the core and Lorentz force of the winding are used as the excitation, and the vibration displacements of the core reactor are obtained; the vibration displacements of the core at different positions are extracted, and the distribution law of the vibration characteristics of the core is obtained. On this basis, considering the influence of stress on the core reactor, the vibration displacement of the core reactor under different stresses is analyzed, and the results show that the stress has a significant influence on the reactor, and the above study has important guiding significance for reducing the vibration of the core reactor.

The output static optical power of the developed y-cut z-propagation Ti:LiNbO3 optical waveguide electric field sensor has been tested under the temperature changes from 5°C to 35°C. The results show that the static optical power has decreased for 866.6 µW, corresponding to a change of 32.79° in the static operating point φB and an electric field measurement error exceeding 10%. Based on the finite element method, the light wave modes in the optical waveguide have been simulated. The results reveal that there is a small Ez component in both the quasi-TE and TM modes, causing φB to be affected not only by the thermal expansion effect but also by the thermal-optic effect. It has been calculated that the effects of thermal-optic and thermal expansion on φB are approximately -0.3301∘/∘C and 0.0087°/°C, respectively, resulting within 5-35°C, the static optical power variation is approximately -267.94µW, with a rate of change is -8.93µW/∘C. Furthermore, the influence of temperature on the birefringence of the sensor output polarization-maintaining fiber (PMF) has been considered and analyzed. It has been found that the phase difference of the slow and fast light waves changes by -3.050rad/K when the length of the PMF is 1488 mm. As a result, considering the effects of thermo-optical and thermal expansion as well as the influence of the PMF, the sensor output static optical power changes -868.86µW, with temperature changes from 5°C to 35°C, which is consistent with the experiment results.

Gas insulated lines (GIL) are renowned for their compact design, high insulation strength, and environmental sustainability, making them a highly reliable and cost-effective choice for power systems. Ensuring the safe operation of gas-insulated lines is crucial for maintaining the reliability of the power grid. This paper proposes a method for abnormal vibration sensing of gas-insulated lines based on an optical fiber interferometer. Utilizing the high-frequency carrier method, the interference of field noise in acoustic vibration signal detection is reduced, and phase information is demodulated using the differential cross-correlation algorithm. In the field application, the abnormal sound and vibration signal is detected, which is finally confirmed to be the metal collision and impact sound caused by the stress release of the head bolt caused by thermal expansion and shrinkage, which verifies the effectiveness of the proposed method.

We designed, fabricated, and experimentally investigated a fully dielectric three-dimensional (3D) intensity electric field sensor, based on the transverse and longitudinal modulations using two crystals. The 3D electric field measurement is achieved by utilizing a lithium niobate (LN) crystal for the 2D measurement and simultaneously a bismuth silicate oxide (BSO) crystal for the 1D measurement. Compared with existing 3D electric field sensors, the developed sensor features structural optimization by using only two crystals. Finally, experimental results show that the sensor linear measurable electric field ranges in the x, y, and z axes are 4.56 to 371 kV/m, 6.83 to 349 kV/m, and 3.77 to 362 kV/m, respectively. When the electric field strengths are 35.2, 60.0, and 77.9 kV/m, and the 3D electric field sensor is rotated 360 deg in the xoz and xoy planes, the maximum measurement errors are 4.79% and 5.71%, respectively.

Based on the Pockels effect of the lithium niobate crystal, an optical field mill DC electric field sensor has been developed. The structural parameters of the rotating shield electrode are optimized by using the COMSOL Multiphysics simulation software. When the inner radius of the shield electrode r = 5 mm, the outer radius R = 25 mm, and the vertical distance between the sensing electrode and the shield electrode d = 2 mm, achieving the maximum modulation field amplitude and optimal performance. Finally, the rotating shield electrode is incorporated with an asymmetric Mach–Zehnder interferometer optical waveguide, resulting in a field mill DC electric field sensor. Experimental results show that the sensor can transfer a DC electric field into an AC electric field with a frequency of 222.2 Hz. The sensitivity of the sensor is determined to be 0.54 mV/(kV/m), with a minimum detectable electric field of 0.37 kV/m. Under a 1 dB compression condition, the maximum undistorted measurable DC electric field Emax is 179.5 kV/m.

In order to gain a clear understanding of the internal electric field changes under three typical faults in the bushing, this paper constructed an 800kV bushing simulation model. A calculation method and fault simulation method for the electric field inside the bushing under electrothermal coupling were proposed, and the range and distribution of the electric field under typical faults were obtained. The results showed that the strength under the three faults reached 3.347 times, 6.24 times, and 2.72 times that of the normal field, respectively, which were positively correlated with the particle radius size and the number of core breakdown layers, and would seriously affect insulation.

By analytical analysis and TCAD device simulation, the physical mechanisms behind the dynamic avalanche and resulting current filament during IGCT turn-off are revealed. It is demonstrated that dynamic avalanche can greatly increase the turn-off time and loss of the device, and with the $\alpha_{pnp}$ increasing, the avalanche-generated current filament becomes stronger and moves slower, which will weaken the ruggedness of the device at the turn-off.

Epoxy resin (EP) is an outstanding polymer material known for its low cost, ease of preparation, excellent electrical insulation properties, mechanical strength, and chemical stability. It is widely used in high- and ultra-high-voltage power transmission and transformation equipment. However, as voltage levels continue to increase, EP materials are gradually failing to meet the performance demands of operational environments. Thus, the development of high-performance epoxy resin materials has become crucial. In this study, a combined treatment using plasma and a fluorine-containing coupling agent was employed to fluorinate graphene nanosheets (GNSs), resulting in DFGNSs. Different concentrations of GNSs/DFGNS-modified EP composites were prepared, and their effects on enhancing the surface insulation properties were studied. Tests on surface flashover voltage, surface charge dissipation, trap distribution, and surface resistivity demonstrated that both GNSs and DFGNSs significantly improve the insulation properties of EP materials. Optimal improvement was achieved with a DFGNS content of 0.2 wt%, where the flashover voltage increased by 16.23%.

Direct fluorination has demonstrated efficacy in modulating the surface electrical properties of epoxy insulators and preventing surface charge accumulation. Comparative corona treatments were conducted on both surface fluorinated (modified) epoxy samples and untreated (virgin/original) samples using a modified electrode setup in a nitrogen (N2) atmosphere. The purpose was to evaluate the resistance of the modified epoxy surface layer against corona discharge. The results of ATR-IR analysis and SEM surface and cross-sectional imaging indicate that corona treatment did not alter the chemical composition of the fluorinated sample or the thickness of the fluorinated layer. Based on assessments of potential decay and water contact angle measurements, the surface conductivity of the modified sample was decreased by corona treatment. The wettability of fluorinated sample remained unchanged after corona treatment, and no soluble degradation products were produced. Conversely, the surface conductivity of the virgin sample exhibited an increase following corona treatment, accompanied by the formation of soluble degradation products. These results confirm that direct fluorination improves the epoxy insulator's discharge resistance in N2 and provides technical support for enhancing the electrical performance of epoxy insulators in gas insulated equipment. (c) 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In H-LCC applications, RB-IGCT needs to operate reliably after continuous switching cycles. The primary challenge is ensuring that the junction temperature of the device remains within safe limits during and after these cycles. Accurate yet simple estimation of junction temperature fluctuations is crucial for device safety. This paper proposed a Foster thermal resistance and capacitor network model based on a simplified power consumption function. The model's accuracy was verified using the Temperature Sensitive Electrical Parameter method. Results indicate that the relative deviation between the junction temperature values obtained from both methods does not exceed 1.1%, confirming the model's reliability.

针对南阳站中国首台/套户外1 100 kV特高压气体绝缘金属封闭输电线路(GIL),文中首先介绍了户外特高压GIL管壳结构的几何构型特点和静力学服役特性;然后,结合相关行业标准,从弹性力学角度分析评述了户外特高压GIL管壳结构的柔性设计技术和应力强度分析理论,并梳理了南阳站户外特高压GIL管壳结构强度试验的不足之处;最后以南阳站1 100 kV户外GIL管壳结构为试验研究对象,于中国首次进行了基于温升应变的日照环境下户外GIL壳体结构的温升形变试验研究,并应用热应力和第三强度分析理论,分析评价了管线结构的温升形变和强度特性,为类似GIL管壳结构的柔性设计和静力学强度评价提供了相应的试验分析基础和技术指导.

Accurate prediction for the corrosion status of grounding electrodes is critical for the safe and stable operation of power systems. However, the corrosion rate of grounding electrodes changes dramatically with the soil environmental parameters, making it hard to be precisely predicted. To address this problem, a deep learning method was proposed to numerically predict the corrosion rate of a galvanized carbon steel grounding electrode in this paper. The long-short term memory method is selected as the modeling algorithm, and also chosen as the hidden layer for the Recurrent Neural Network, while the soil environmental parameters are used as input features. The predicted results match well with the experimental data when evaluated using different soil parameters, such as soil moisture, chloride (Cl-) concentrations, and sulfate (SO42-) concentrations. The threshold corrosion rate related to each parameter is obtained to estimate the corrosion rate with more accuracy. We proposed a deep learning method to numerically predict the corrosion rate of a galvanized carbon steel grounding electrode in this paper. The long-short term memory method is selected as the modeling algorithm, and also chosen as the hidden layer for the recurrent neural network, while the soil environmental parameters are used as input features. The predicted results match well with the experimental data when evaluated using different soil parameters, such as soil moisture, chloride (Cl-) concentrations, and sulfate (SO42- )concentrations. The threshold corrosion rate related to each parameter is obtained to estimate the corrosion rate with more accuracy.image

由于光纤具有抗电磁干扰、高带宽、高绝缘等特性,在换流阀通讯和晶闸管触发中,占据重要的地位.针对换流阀触发光纤故障的现场实例,首先通过对光纤故障点处宏观及微观的形貌分析,确定了光纤故障类型为局部放电,随后利用有限元法对换流阀屏蔽罩及光纤进行了等比例建模及电场计算,分析了光纤故障点处出现局部放电的原因.结果表明,当光纤轴向电阻率分布不均匀时,易与相邻光纤发生局部放电;当光纤在安装过程中,没有被光纤盖板钳制电位时,光纤与盖板之间极易发生局部放电.本文结果可为换流阀触发光纤的安装提供一定的技术支持.

雷击输电杆塔时,通过接地装置流入大地电流和流过地线的电流都会在附近埋地管道的防腐层上形成干扰电压,对管道形成威胁.本研究利用频域矩量法结合时频转化的方法,建立了雷击输电杆塔时附近埋地管道防腐层电压的计算模型,给出了土壤电阻率、管道与输电线路的间距、管道尺寸、防腐层电阻率和防腐层厚度对防腐层电压的影响,并对安装排流带和改变杆塔接地装置结构的防护措施的效果进行了计算,结果表明合理的布置排流带和改变接地装置结构,可降低管道防腐层的电压.

针对传统火灾探测器在火灾检测方面的不足,传统的图像识别技术对于火灾预测精度不高的问题,采用基于改进的RFBNet算法进行火灾识别.本算法在原来的RFBNet算法的框架上进行改动,采用自适应特征提取优化特征提取操作、反卷积增强融合和增强型软性非极大值抑制,通过提高网络的特征提取能力、加强层级联系和减少重叠目标的漏检率来提高小目标物体的识别精度低和识别准确率低的问题.实验表明,该方法可以有效识别出火灾,识别精度达到93.5％,优于RFBNet算法,速度上也满足实时性要求.