DC total electric field measurement under highvoltage direct current (HVDC) transmission lines suffers from inherent challenges of electric field distortion caused by sensor grounding and interference from corona ions. To address these issues, this article develops a ground-free differentialrotation dual-probe field mill. The sensor consists of two identically structured split-cylinder probes coaxially mounted on a common motor shaft but operating at different rotational speeds, together with peripheral signal processing circuits. Each probe comprises multiple fan-shaped cylindrical metal mantles with uniform dimensions, a motor, a photodetector integrated with a grating and a slot-type photoelectric sensor, and a slip ring. Four key innovations are incorporated. Corona discharge tips on the mantle surface enable potential clamping via charge leakage. Multifan-shaped cylindrical metal mantles enhance electric field measurement sensitivity and resolution. Dual probes with differential signal processing suppress corona ion interference. A dedicated hardware circuit performs weak signal conditioning, polarity discrimination, and signal output. The field mill was comprehensively validated using laboratory calibration systems, reduced-scale conductor models, and field tests on the +/- 800 kV UHVDC Zhalute-Guanggu transmission line. Laboratory results demonstrate excellent linear response in ion-containing electric fields, with relative deviations from simulated values within +/- 2.15% under corona conditions, matching the accuracy of conventional shutter-type field mills. Field measurements show consistent trends with traditional devices in both perpendicular and parallel cross sections of the transmission line, confirming stable operation in engineering environments. These results verify that the proposed field mill effectively mitigates grounding-induced distortion and corona ion interference, meeting the requirements of engineering applications. The main limitation is slightly inferior measurement repeatability compared to shutter-type field mills, and future work will focus on optimizing probe rotation stability and signal processing algorithms to improve measurement consistency, thereby facilitating broader application in electromagnetic environment evaluation of HVDC transmission lines.

ABSTRACT The low pressure in high‐altitude areas exacerbates the issue of audible noise (AN) caused by intense corona discharge on the conductor surface. This problem is a critical factor in the structural design and conductor selection for extra‐high‐voltage and ultrahigh‐voltage (UHV) AC transmission lines. The study of spectrum characteristics is vital for understanding the intrinsic properties of AN. However, there is a lack of studies on the AN spectrum properties of practical bundled conductors at high altitudes, which makes it difficult to accurately guide power line construction in high‐altitude regions. The high‐altitude UHV corona cage in Yangbajing, Tibet, was used in this work to investigate the noise spectrum properties of three conductor types: 6 × LGJ500, 8 × LGJ630 and 10 × LGJ630. The conductors' 1/3‐octave frequency noise characteristics and AN equivalent A‐weighted levels under different electric field strengths under heavy rain were measured. Then, the correlation between the 8‐kHz characteristic frequency level and the AN A‐weighted sound level in high‐altitude regions was investigated. Finally, the A‐weighted acoustic power levels of AN at three altitudes of Wuhan, Xining and Yangbajing were compared and analysed. The results of this study can provide certain guidance for power companies' high‐altitude power line designs.

Audible noise (AN) is a critical parameter in the economic and environmental design of extra-high voltage (EHV) AC transmission lines, especially in high-altitude regions. Although several altitude correction factors and AN prediction methods have been proposed based on corona cage tests and long-term observations, the accuracy remains uncertain owing to the limited measurement data from high-altitude transmission lines. This study addresses this gap through long-term observations of four EHV transmission lines on the Tibetan Plateau, combined with existing corona cage test results. The cumulative distribution of AN in rainy weather was obtained from various observation stations. By comparing measured values from stations at different altitudes and combining the experimental results from a movable corona cage, an altitude correction method for AN was developed. Subsequently, by comparing statistical data from four high-altitude observation stations with predicted results from different approaches, the predicted values were found to be overestimated. An improved prediction method for AN in rainy weather was proposed. Additionally, based on the statistical differences observed over one year at multiple long-term observation stations, a method for evaluating AN under varying weather conditions was investigated. A predictive model for AN under different rainfall conditions was developed based on correlation and multiple regression analyses, and its accuracy was validated. The findings of this study provide a crucial reference for the prediction and evaluation of AN from EHV AC transmission lines in high-altitude regions.

Radio interference (RI) is a critical factor in the design of extra-high voltage (EHV) transmission lines at high altitudes. To address the insufficient field data of RI on high-altitude transmission lines, the lack of adequate validation for existing RI prediction methods, and the difficulty in assessing RI levels under various meteorological parameters, this study investigated prediction methods for RI in high-altitude AC transmission lines based on long-term observations. First, the altitude correction factors for RI were investigated by comparing long-term observational data from different altitudes and results of movable corona cage tests. Second, a more accurate RI prediction method for high-altitude transmission lines was proposed by comparing the long-term measured data from four high-altitude observation stations with the predicted values derived from various formulae. Finally, correlation and multiple regression analyses were employed to develop RI prediction models considering the effects of different meteorological parameters under both rainy and fair weather conditions. The accuracy of these models was validated using actual measurement data. The findings provide important references for the prediction and evaluation of RI from EHV AC transmission lines at high altitudes.

Audible noise has become a critical constraint in the construction of high-altitude ultra-high-voltage alternating current (UHV AC) projects. Currently, there is a lack of research on audible noise from UHV AC transmission conductors under extreme altitudes above 4000 m. This study, conducted at the Yangbajing High-Altitude Test Base in Tibet (4300m), employed a UHV corona cage and a BK sound measurement system to investigate the audible noise characteristics of three typical conductor configurations—8 × LGJ-1000, 10 × LGJ-630, and 12 × LGJ-500—under both dry and rain conditions. The audible noise levels under varying surface electric field strengths were systematically measured, and the coupling effects of rainfall and electric field intensity on noise generation at extreme altitudes were analyzed. Furthermore, using a typical 1000kV UHV AC single-circuit transmission tower configuration, a sound power calculation method was applied to evaluate the audible noise of transmission lines at 4300 m altitude. The findings provide essential references for the design and construction of UHV AC transmission lines in extremely high-altitude regions.

Compared to plain areas, the corona discharge phenomenon and audible noise (AN) problem of AC transmission lines are more prominent under the low pressure condition of high altitude environment, which has become a significant challenge in the research of transmission technology for extra-high voltage (EHV) and ultra-high voltage (UHV). Nevertheless, there has been scant research into the AN levels of transmission lines above 3000 m, making it challenging to effectively guide the design of lines in high-altitude regions for power utilities. To address this, this study utilized the high-altitude UHV corona cage in Yangbajing, Tibet (altitude: 4300 m), to conduct a detailed study on the sound pressure level (SPL) of seven types of bundled conductors under heavy rain conditions. The experimental data were summarized and the impacts of conductor design parameters and electric field (E-field) intensities on the acoustic power density level (LPWL) were studied. Subsequently, a linear regression analysis method was used to propose an empirical formula for the A-weighted LPWL suitable for an altitude of 4300 m under heavy rain conditions. Finally, through comparing the measured data at two altitude locations—Wuhan (23 m) and Yangbajing (4300 m)—the altitude correction values for AN were derived, and it was examined how the surface E-field intensity and conductor parameters affected the correction results. In high-altitude areas, the study findings presented in the work can serve as a valuable data source for the conductor selection of AC transmission lines construction.

Using X-ray detectors to inspect power lines can promptly identify defects and eliminate potential hazards. However, during operation, X-ray detectors require equal potential at the input/output, which can lead to arc discharge of suspended potential conductors, creating intense electromagnetic changes that severely disrupt the normal operation of the X-ray detector. This paper analyzes the potential impacts of such arc discharge on X-ray detectors and establishes a three-dimensional model. The FDTD and TLM hybrid algorithm is used for simulation analysis of the power density inside the X-ray detector, the induced voltage in the internal and external cables under the influence of the arc discharge field, and electromagnetic compatibility assessment. Finally, the induced current in the external cables is measured, with the simulation results matching the measured results well. When X-ray detectors are applied in power line environments, the internal high-speed circuits, embedded computers, and CCDs need to be reinforced with electromagnetic protection. The induced voltage on the RJ45 connecting the inside and outside of the X-ray detector reaches 21.89V, requiring transient overvoltage suppression at the interface.

Corona loss is an important factor in the construction of ultra-high voltage (UHV) alternating current (AC) transmission lines. There is little research on the corona loss associated with multiple bundle conductors for UHV AC projects situated at altitudes exceeding 4000 m. To address this gap, this paper conducted a study at the Yangbajing Experimental Base in Tibet at an altitude of 4300m. Utilizing a large UHV corona cage and an integrated photoelectric corona loss measurement system, the study investigated the corona loss characteristics of two types of 8-bundle test conductors under dry, heavy rain, and wet conditions. The investigation yielded corona loss values under varying field strengths and analyzed the impact of rainfall and field strength on conductor corona losses at extreme altitudes. Subsequently, by taking the 1000 kV UHV AC single circuit transmission project as an example, the equivalent method of corona loss was employed to evaluate the corona loss of transmission line conductors at an altitude of 4300 m. The research results can serve as a reference for the construction of UHV AC transmission lines in extremely high-altitude areas of China.

To ensure the safe operation of live working robots in strong electromagnetic environments, this paper conducts simulation calculations on the electric field distribution process when robots enter and exit the equipotential of 500 kV lines. First, finite element models of 500 kV typical single-circuit and doublecircuit lines on the same tower are established to analyze the electrostatic field distribution, surface potential, and capacitance matrix at different positions during the robot’s up-and-down line process. It is found that: the electric field strength at the tip of the robot and the hanging device is the largest, exceeding the average corona onset field strength of line fittings ($30 \mathrm{kV} / \mathrm{cm}$). Before the robot undergoes potential transfer, it basically reaches saturation when the distance from the conductor is within $\mathbf{0. 1 m}$ but not in contact with the conductor, which is about 80% of the conductor voltage; the capacitance to ground stabilizes when the distance from the conductor is within 0.1 m but not in contact with the conductor. When the arcing distance is between 10 50 cm, the capacitance value is between $70-140 \mathrm{pF}$. The research results provide key data support for the anti-electromagnetic interference design of live working robots, which is of great significance for improving the reliability of robots in high-voltage environments.

为了减轻5G基站天线引入变电站后对站内敏感设备带来的电磁干扰,并对站内各监测设备处的5G信号进行优化,提出了一种基于多目标粒子群算法的变电站5G基站天线布点方法,即以变电站敏感设备处的射频场强不能超过规定的电磁兼容抗扰度限值为约束条件,以站内监测设备接受信号的Pareto最优解作为目标函数,采用多目标粒子群算法在变电站相关布点区域内寻找出最合适的基站天线布点.以500 kV官渡变电站为例,按照其内部实际的空间布局,利用本文算法得到4种天线布点安装方案,都能使得站内所有敏感设备处的射频场强低于10 V/m抗扰度限值,同时还能使得站内各监测设备处的平均信号分别提升3.77、6.37、4.34、4.58 dB,监测设备信号的方差分别减少了 15.07％,12.64％,14.62％,14.78％,说明了本文算法即可以在一定程度上提升监测设备处的信号强度,还能使得站内各监测设备处信号的离散程度减小,使得信号在监测设备处覆盖更稳定,能为实际工程中变电站内5G基站天线的布点提供一定的参考.

5G (fifth generation) signals have small coverage and poor stability, and 5G channels are prone to loss in substations densely populated with metal equipment. Due to the particularity of the spatial layout in the substation, traditional physical or statistical channel models cannot accurately calculate the 5G channel loss in the substation. Therefore, this paper introduces the basic idea of ray tracing algorithm for studying ray propagation. Based on the geometric optics theory of ray propagation, the effective channel path of 5G signal in substation is found. Through the electromagnetic reflection theory and consistent diffraction theory, the energy loss caused by signal reflection and diffraction is calculated. Combined with the relationship between the free space loss of 5G signal on the transceiver path and the change of electric field, the solution method of 5G channel loss in substation is deduced. According to this method, (the influence of signal receiver height, 5G antenna height and its spatial position in horizontal and vertical directions on 5G channel loss of substation is studied in turn. By optimizing the layout of communication facilities according to the influence law, the reliability of 5G channel in substation can be realized).

The total electric field in HVDC (High-Voltage Direct Current) transmission projects is closely related to corona discharge on the conductors and greatly influenced by the surrounding environmental conditions. Currently, there is no comprehensive theoretical analysis method to fully understand the complex coupled effects of various weather parameters on DC electric field. In this paper, a long-term monitoring point was established beneath a ±800 kV bipolar HVDC transmission line in China, and continuous monitoring was conducted for one year to obtain statistical results of the ground-level electric field and weather parameters. Three methods, namely the Spearman correlation coefficient, the Elastic Net Regression model, and the SHAP values based on the XGBoost model, were employed to analyze the most significant weather parameters affecting the ground-level electric field beneath the poles. The research findings contribute to a better understanding of the impact of weather parameters on the total electric field.

This article proposes an interharmonic pulse-width-modulation (PWM) technique, which is based on the linear continuous phase modulations of asymmetrical optimal pulse patterns synchronously. It can move any low-order harmonic component to be a specific interharmonic without any phase angle difference, and does not change other frequency components, improving the output voltage quality. The frequency shift range of harmonic is explored by the switching frequency lower than 1kHz for high power converters of utility application. It is helpful to avoid exciting the LC filter or LCL filter and consequently to prevent interharmonic resonances for power systems with high penetration of inverter-based renewable power generators. Finally, the effectiveness is verified by the experiment results.

In order to reduce the electromagnetic interference caused by the introduction of the 5G base station antenna into the substation to the sensitive equipment in the station, and to optimize the 5G signal at each monitoring device in the station, a method for 5G base station antenna placement in the substation based on the multi-objective particle swarm algorithm is proposed, namely, The radio frequency field strength at the sensitive equipment of the substation cannot exceed the specified electromagnetic compatibility immunity limit as the constraint condition, and the Pareto optimal solution of the signal received by the monitoring equipment in the station is used as the objective function. Find the most suitable base station antenna layout. Taking the 500 kV Guandu substation as an example, according to its actual internal space layout, four antenna layout installation schemes are obtained by using the algorithm in this paper, which can make the radio frequency field strength at all sensitive equipment in the station lower than the 10 V/m immunity limit, and at the same time It can also increase the average signal of each monitoring equipment in the station by 3.77, 6.37, 4.34 and 4.58 dB respectively, and the variance of the monitoring equipment signal is reduced by 15.07, 12.64, 14.62 and 14.78

Due to the complexity of the spatial layout of metal equipment in the substation, the traditional geometric modeling method cannot accurately calculate the 5G channel loss in the substation. Due to the short wavelength of the 5G signal, it can be seen as ray propagation. Therefore, this paper introduces the basic idea of ray tracing algorithm. Based on the geometric optics theory of ray propagation, the reflection point and diffraction point are determined by using the spatial geometric characteristics of signal reflection and diffraction, and the effective channel path of 5G signal in substation is traced. Then, the energy loss caused by the reflection and diffraction of the signal is calculated by the electromagnetic reflection theory and the consistent diffraction theory. Combined with the relationship between the free space loss and the electric field change of the 5G signal on the transceiver path, the solution method of the 5G channel loss in the substation is derived.

When a live working robot enters/leaves a high-voltage conductor, the induced discharge will cause violent electromagnetic field changes, which may cause the robot to refuse to move, misuse or even damage. In order to clarify the AC induction discharge characteristics of live working robots, an AC induction discharge test system and a pulse current measurement system conforming to the IEC 61000-4-2 standard are established. The induction discharge test of the robot is carried out in an anechoic chamber. The robot’s arcing current was measured using a broadband pulse current sensor and a floating oscilloscope. The measurement results show that the rise time of a single current pulse is 0.2-10ns, the duration is about 800ns, the frequency is within 1.3GHz, and the main energy is concentrated within 100MHz. As the gap between the robot and the conductor decreases, the number of induced discharge current pulses increases, the pulse amplitude increases first, and then decreases when it reaches a certain value. As the voltage increases, the AC induced discharge current of the robot also increases. The magnitude of the robot’s AC induced discharge current is related to the robot’s capacitance to ground. The larger the capacitance to ground, the larger the discharge current. Through the statistical analysis of 2000 sets of measurement data, the regression formulas of the induced discharge current and voltage, capacitance and the gap between the robot and the wire are obtained. The results show that the AC induced discharge of the robot is different from the electrostatic discharge. According to the test results and the current regression formula, the electromagnetic interference protection design of the robot and the electromagnetic compatibility standard of the robot can be formulated.

—The smart electricity meter (SEM) is a critical element of the smart grid, so power supply company and customers pay many attentions to its service life. SEM is directly employed in the power grid, and there is serious harmonic pollution. The traditional life prediction method of SEM has not considered the influence of the harmonic factor on the reliable life of the SEM, this paper proposes a novel life prediction method of SEM based on the harmonic factor. Based on the data of reliability harmonic test, the harmonic factor is extracted and integrated into the meter life prediction model to improve the accuracy of the prediction. The comparison between the prediction of multiple models of SEMs and the results of accelerated life testing verifies that the method has high accuracy.

Under the irradiation of electromagnetic waves from the 5G base station antenna, the densely distributed equipment in the substation produces a strong secondary scattering phenomenon due to the coupling effect, which may have a great impact on the solution of the electromagnetic scattering field in the substation. Therefore, on the basis of the electromagnetic scattering of electrically large targets in traditional wide-area space, this paper proposes a scattering field calculation method that considers the mutual coupling of electrical equipment in substations. The accuracy of the algorithm is verified by the actual measurement of the 500kV Guandu substation. Taking the 500kV Guandu substation as an example, the algorithm is used to solve the electric field strength near the electrical equipment under different antenna powers and inclination angles of the 5G base station antenna, it is then compared to traditional algorithms. The results show that when the 5G base station antenna power is 200W and the inclination angle is 10°, the secondary scattering between substation equipment is the most serious.

With the rapid development of 5G communication technology and the widespread application of micrometeorological online monitoring equipment, the electromagnetic interference of 5G base station antennas on shared towers to micro-meteorological online monitoring equipment arranged on the same tower has attracted widespread attention. To this end, according to the working principle of 5G base station antennas, analyze the interference mechanism of 5G base station antennas on micro-meteorological online monitoring equipment; Combining the principle of the array antenna and the theory of electrically large-size metal scatterers, a mathematical model of electromagnetic interference of 5G base station antennas on the micro-meteorological online monitoring equipment under the background of the tower is established; Taking the actual shared tower as an example, the electromagnetic interference simulation model of the 5G base station antenna to the micro-meteorological online monitoring equipment was established, and the electromagnetic interference law of the 5G base station antenna to the micro-meteorological online monitoring equipment was calculated under different antenna numbers, powers and inclination angles., Provides a certain theoretical basis for the subsequent study of the electromagnetic environment of shared towers.

With the development of extra-high voltage and ultra-high voltage transmission line in China, the reradiation interference generated by induced current on the surface of transmission steel tower becomes more serious to the radio station in the vicinity. In this paper, the calculation method for reradiation interference of transmission steel tower based on method of moment is analyzed. And in order to reduce the impedance matrix storage data in the memory space and the number of iterations in the calculation, the preprocessing of matrix sparse and diagonal norm precondition is presented to improve the performance of the conjugate gradient algorithm for the reradiation interference calculation. The reradiation interference of a standard 500 kV transmission steel tower is calculated using the improved conjugate gradient algorithm. And the results show that the algorithm enhances the convergence and stability after preprocessing and is suitable to calculate the reradiation interference of super-large metal truss structure target.