Dynamic line rating (DLR) is an important approach to relieving thermal constraints on transmission lines. However, existing studies lack operational boundary evaluations based on long-term field data, and the short-term fluctuation risk of real-time dynamic ampacity limits its application in dispatch. Therefore, this paper proposes a dispatchable dynamic line rating (DDLR) evaluation method incorporating short-term drop risk constraints. An integrated DLR monitoring device was developed and deployed. Based on long-term field measurements of a 110 kV line, the uprating benefits, meteorological driving mechanisms, uprating sustainability, and short-term drop risks of DLR were systematically evaluated. On this basis, combined with the K-nearest neighbor conditional quantile regression method, the DDLR index was constructed. Results show that the measured dynamic ampacity is dominated by wind speed, averaging 1.23 times the static line rating (SLR), and possesses uprating potential for 86.31% of the time, though capacity shrinkage risks exist under adverse cooling conditions such as low wind speeds. Under a nominal 90% reliability constraint for 10-min rolling dispatch, the proposed DDLR exceeds the SLR for 68.18% of the time, achieving an average capacity increase of 12.40% over SLR. This study can provide a reference for the engineering application and operational dispatch of DLR technology.

Real-time vibration monitoring for oil-immersed transformer windings is critical for power grid digitalization, yet traditional fluid-structure interaction (FSI) simulations remain computationally prohibitive. This paper proposes a Domainless fluid inertia equivalent(DFIE) method that eliminates flow domain meshing by discretizing fluid velocity potential and added mass directly on the winding boundary. The method couples with structural dynamics to form a simplified 'structure-inertia' equation, bypassing global flow field calculations. Compared with the global FSI method, DFIE reduces the calculation time by 99.38% and the memory occupation by 26.43% while maintaining the calculation accuracy (error within 5%), which breaks through the core bottleneck that the traditional method's 'accuracy-efficiency' is difficult to balance. The multi-condition vibration test carried out on the customized 10 kV oil-immersed distribution transformer experimental platform further verifies the effectiveness of the method : the average relative error of the vibration acceleration amplitude between the simulation and the experiment is 3.35% (within 3.5%). Crucially, the direct sensor placement on the transformer coil surface resolves prior validation gaps. The method enables rapid multi-condition vibration evaluation for dynamic stiffness optimization and fault early-warning model training, directly addressing measurement-validated engineering solutions. By breaking the 'accuracy-efficiency' trade-off, DFIE provides a practical path for real-time transformer monitoring in smart grids.

Researching the measurement of DC total electric field with space charges (Poisson field) can help establish a monitoring system for the electromagnetic environment of UHVDC transmission lines and protect the health of the ecological environment. This paper proposes a DC total electric field optical measurement method based on the Pockels effect and probe self-rotation modulation. It can address the issues of internal charge drift and external charge accumulation in traditional optical probes when measuring DC electric fields with space charges. Theoretical analysis was conducted on measurement under probe rotation, and the optical modulation system was integrated into a probe with dimensions of 60 mm x 30 mm x 20 mm. A self-rotating platform for the probe was designed, and the influence of rotation mode on the results was analyzed. It was found that the sensitivity was higher when using the horizontal-horizontal mode. The signal processing system was tested, showing that the probe retained around 50 % of its original output when rotating at low speeds (frequency 1-3 Hz), fully meeting the measurement requirements. The test platform has been constructed, and the probe's sensitivity was assessed under an AC electric field and validated under a DC electric field. Finally, the optical method proposed in this paper was used to measure the DC total electric field with space charges under a small model of a unipolar HVDC transmission line. Five locations under the line were selected as measurement points, and the results were compared with those obtained from a field mill probe and numerical simulation. This comparison indicates that the proposed method agrees with experimental and simulation results. The average sensitivity of the self-rotating optical probe was 3.71 mV/(kV/m). The error did not exceed 5 % in high-field strength areas (above 20 kV/m) and was also controlled within 15 % in low-field strength areas (below 20 kV/m).

With the development of deep-sea wind power, the temperature hotspots of submarine cables in J-tubes are getting increasing attention. Currently, the relevant standards do not provide a thermal rating method for such cable sections, and the only studies are difficult to apply in practice. This study derived an analytical solution for calculating the derating in ampacity of submarine cables within J-tubes. The proposed approach is efficient and readily integrated with IEC-related standards. Initially, an indoor experiment was conducted to validate the correctness of the analytical model. Subsequently, a numerical example utilizing an actual HVDC submarine cable is presented, demonstrating increased cable conductor temperature within the J-tube and a corresponding reduction in ampacity. A derating factor is employed to quantify the extent of ampacity reduction, which is a function of the J-tube length, outer diameter, ambient temperature, wind speed, and solar radiation intensity. It turns out that once the J-tube air section's length exceeds approximately 60 times the cable outer diameter, the transmission circuit ampacity can be based on the value installed in the infinite J-tube. Furthermore, factors resulting in substantial cable ampacity reduction, such as high solar radiation intensity, may yield a derating factor approaching 0.6.

The increasing permeability of renewable energy render the traditional static security analysis method based on deterministic load flow no longer applicable. In power systems with uncertain renewable energy sources, probabilistic load flow (PLF) analysis must be conducted to achieve static security analysis of the power system by examining voltage and branch load flow during the operation. This paper proposes a PLF calculation method based on C-type Gram-Charlier series expansion and cumulant (CGC-CM), which can determine the distribution characteristics of bus voltage and branch transmission power. The proposed method solves the problem of negative values in the calculation of PLF for the results of the traditional A-type Gram-Charlier series expansion (AGC) method. Additionally, three typical wind and photovoltaic power generation output scenarios are created using k-means clustering, followed by an assessment of the static security of the power system. In this paper, the accuracy and efficiency of the algorithm is verified using the IEEE30 test system. Besides, it is observed that the static stability of the power system decreases with an increase in wind and photovoltaic power output. Subsequently, a real power system model was established and demonstrated that the branch capacity increase can improve the stability of the system operation.

Due to the enclosed air interlayer in the J-tube section, it has the potential to limit the current-carrying capacity of offshore wind farm export cables. The standard calculations outlined in the IEC guidelines are deemed inadequate for this unique laying method. Conducting fluid simulations can be time-consuming and challenging to implement in practical engineering scenarios. This article introduces a rapid calculation approach for determining the current-carrying capacity of submarine cables in J-tube sections, utilizing a semi-empirical correlation formula for natural convection in a vertical enclosed annular space and an axial heat transfer model for submarine cables. A comparative analysis between the proposed method and thermal-fluid coupling numerical simulations demonstrates the effectiveness of the proposed approach.

The ion flow field of UHVDC transmission lines is greatly affected by wind, especially in high-altitude areas where the regional and gradient differences in wind speed are significant. To accurately provide the required wind speed verification values for line parameter design, a numerical simulation method based on Weibull-WSE-UFEM is proposed in this paper. Weibull function is used to construct the probability distribution of wind speed in the studied area based on real data, and the maximum value within the appropriate range is selected as the wind speed verification value for the location of the wind speed sensor. Wind Shear Exponent (WSE) is used to expand the verification values at different positions in the vertical direction. Upstream Finite Element Method (UFEM) is used to calculate ion flow field and the verification values are used as the input wind speeds in different height nodes. The method was applied to a real high-altitude UHVDC transmission line case and the theoretical minimum height of line to ground was obtained. The results indicate that the method has certain guiding significance for the design of UHVDC transmission lines in high-altitude areas.

In order to study the influence of drizzle weather on the total electric field of ultrahigh-voltage direct current (UHVDC) transmission lines, an ion flow field model considering drizzle weather is established. This model calculates not only the positive and negative ions but also the charged tiny water droplets, dust particles, and falling raindrops, enabling accurate simulation of the total electric field in drizzle weather. Meanwhile, the ion flow field model is solved by the improved upstream finite element method. First, the influence factors and mechanism of drizzle weather on the ion flow field of UHVDC transmission lines are studied in this article. Then, the improved upstream finite element method is used to solve the ion flow field under different degrees of drizzle weather. Finally, the influence rule of drizzle weather on the total electric field at ground level is obtained. In this article, the accuracy of the ion flow field model is proved by the measurement data of the ground-level ion flow field of the +/- 800-kV UHVDC transmission line from Chuxiong to Suidong. The research results show that the ion flow field of drizzle weather at ground level is larger than that of sunny weather. With the degree increase of drizzle weather, the peak value and distribution curve of the ground-level total electric field gradually increases. This article has a guiding role for the construction and the safe operation of UHVDC transmission lines considering drizzle weather.

As an important indicator of the electromagnetic environment of UHVDC transmission lines, the ion flow field needs to be quickly calculated and updated in case to meet the requirement in building a digital twin of the power transmission system. This paper is based on the UFEM and starts from two aspects: electric field intensity convergence and charge density convergence. a) An adaptive iteration factor for charge density update is introduced, which can automatically control the iteration speed according to the change degree of electric field intensity, ensuring the rapid and stable update of charge density. b) On this basis, a half-error term is added to the charge density update formula. This controllable disturbance has little impact on the convergence of the charge density, but can greatly accelerate the convergence of the electric field intensity. Their combined effect greatly reduces the iteration steps required for the entire solution. A coaxial cylindrical model with analytical solutions and a real +/- 800 kV UHVDC transmission line project with test results are used to verify the method. In terms of accuracy, the numerical calculation results are exactly the same as the analytical solutions and are basically consistent with the test results. In terms of speed, compared with traditional fixed factors, after using the adaptive iteration factor, the iteration steps are reduced by up to 75%. In addition, after adding the half-error term, the iteration steps are further reduced by 32%. This method can strongly support the application of digital twin technology in power transmission.

The insulator surface charge buildup issue is a significant element impacting the electric field on the insulator surface in HVDC transmission. The electrostatic probe method is used to measure the surface potential of various insulators under the corona situation in order to acquire insulator surface charge buildup and dissipation regularity under DC high voltage. A charge density inversion approach for curved surfaces is suggested in this study. The chosen measurement points are used to create triangular meshes from the curved surface. Based on the measured potential, surface charge density is inversed. According to the findings, an insulator with a PRTV coating on its surface is easily charged. The surface potential attenuation trend of the insulator shed sprayed with PRTV coating is exponential attenuation. The peak value of insulator shed sprayed with PRTV coating surface charge density is about −0.5μC/m2.

The resistive current of metal oxide arrester (MOA) is an important parameter for evaluating the aging condition of arrester. To extract the resistive component from the full current, the phase angle between the full current and the busbar voltage must be known. In conventional measurement, the voltage signal needs to be acquired from the secondary side of the capacitor voltage transformer (CVT), so there is a risk of short circuit to trigger equipment damage. To solve the above problems, a non-contact measurement method for the busbar voltage phase of substation arrester is proposed. By placing suitable electric field probe under the arrester, the busbar voltage phase is derived from the electric field information. Moreover, models of ultra-high voltage (UHV) substation arresters based on actual operation are constructed to verify this method, and the optimal placement of probes is given. The results show that the error is relatively minimum when the electric field probe is placed between the arrester and the CVT and is 1.3 m - 2 m away from the arrester. In addition, the arrangement of double detection points proposed can not only obtain the phase sequence of the three-phase voltage of the power grid, but also average the measurement errors.

Gas insulated transmission line (GIL) is widely used for large-capacity power transmission in complex environment, and has the characteristics of long distance and totally enclosed structure. When the insulation fault occurs inside GIL, its metal shell structure makes it more difficult to monitor through optical, electrical and other physical quantities. Considering the rapidity and accuracy of positioning, the propagation of sound waves along the GIL sheath is a commonly used method in GIL on-site PD testing and running state online monitoring for fault positioning. This paper establishes a high-pressure GIL acoustic propagation simulation model based on pipe acoustics theory, analyzes the frequency dispersion and mode distribution of acoustic waves along the GIL shell, determines an appropriate fault location strategy based on the propagation velocity and attenuation of the selected acoustic wave mode, and carries out experiments to verify it. The results of the research show that the low order bending wave F(1,1) propagated along the GIL shell has good positioning characteristics, and the propagation velocity conforms to the dispersion curve distribution. By taking into account the attenuation and delay of the acoustic wave passing through epoxy insulators or expansion joints in the fault localization strategy, the localization accuracy can be improved by 60%. And this positioning strategy was verified to be effective in the GIL insulation fault localization test conducted in the field.

Due to the varieties of actual operation conditions of the transmission lines and complex surrounding environment, safety accidents caused by entering the danger range of live lines by mistake often occur. Aiming at the problem that it is difficult for the staff to judge whether the transmission line is electrified during the operation and maintenance of the transmission line, based on the space electric field detection technology, this paper proposes an effective and simple method to judge the electrification of the transmission line by adding an electric field probe on the top of the crane arm. It establishes a three-dimensional finite element model of an extendable crane to analyze the influence of crane intrusion and suspension length of crane arm hook on the electric field distribution near the transmission line. According to different operation conditions of the line, the paper proposes the characteristic positions, characteristic components and criteria of live circuit identification. The results show when the characteristic position is right below 4 m of the double-circuit line and the characteristic component is the electric field intensity component at the side of the crane, the operation state of the transmission line is determined as double-circuit electrification if the difference between the characteristic components of the right and the left probes is within 50%. While if the characteristic component of the probe at one side is more than three times of that the other probe, the circuit at this side is determined as single electrification state.

The proportion of resistive current in the leakage current of lightning arrester is very small, and it is difficult to judge the health state of lightning arrester directly by the leakage current in the degraded state. In view of the problem that it is difficult to extract the resistive current from the leakage current of 500 kV arrester, the spatial capacitance matrix of the arrester is obtained through fine modeling of the arrester and simulation calculation. Based on the resistance capacitance network theory and the field circuit coupling method, the accurate equivalent network model of 500 kV arrester is constructed. Based on the idea of partial capacitance concentration equivalence, a fast extraction method of resistive current is proposed, which improves the accuracy and efficiency of 500 kV arrester resistive current extraction, and is verified by the field measured data. Finally, the applicability of the calculation method is verified by analyzing the inconsistent resistance of each phase. The results show that the phase error of the proposed method is within 4

When the traditional tower circle method is used to calculate the lightning parameters of transmission lines, because the radius of the tower circle is far greater than the span, there will be many overlapping areas. The lightning parameters in the overlap areas will be calculated many times, it will not only increase the calculation amount, but also lead to inaccurate results. In this paper, a new statistical method for lightning parameters of transmission lines is proposed. The line corridors are divided into block rectangles of equal size, which are close to each other as much as possible to reduce the impact of overlap. Taking the 500kV Xianmeng I transmission line as an example, the lightning density of each tower is calculated by block method and the lightning risk assessment is carried out. Compared with the traditional method, the results of the block method can better reflect the lightning parameter characteristics of the local tower.

Real-time synchronization and high fidelity are the most important features of the digital twin technology. When constructing the digital twin of power equipment in flexible DC transmission technology, the simulation analysis based on transient electric field is accurate, but the real-time is difficult to guarantee due to complex structure and various working conditions. In order to reduce the delay caused by the solution as much as possible, starting from the type of excitation source, an electric field equivalent method for AC/DC hybrid electric equipment adapted to digital twin with low latency is proposed: electrostatic field equivalent is used under power frequency AC or impulse voltage excitation, and constant electric field equivalent is used under typical DC voltage at the converter station. The method has been theoretically deduced in detail and verified by using a RC voltage divider model. The results show that the method proposed in this paper can shorten the solution time to 6.4% of the original, and ensure that the error after equivalence is within 5 & PTSTHOUSND;. Finally the method is actually applied to the digital twin electric field analysis of a power supply transformer for 535 kV DC circuit breaker. The time required for solving is 40 min and 14 s. It can fully meet the demand of the dispatching department to update and calibrate the electric field once every hour and ensure safe and stable operation of equipment without corona.

作为柔性直流输电中的关键设备，干式直流支撑用电容器在运行时由于散热条件较差，其内部温升分布呈现明显的不均匀性，严重影响电容器的使用寿命。为此，以某型号高压大容量干式直流支撑用电容器为研究对象，提出了电容器的电热耦合分析模型，考虑了汇流排上电流密度分布特性对电容器整体温升的影响，通过试验验证了所提出模型的准确性，并利用NSGA-Ⅱ遗传算法对铜排的结构参数进行了多目标优化。结果表明，汇流铜排上的发热功率占电容器总发热功率的18.7%，计算时必须予以考虑；当铜排的厚度为1.3 mm，宽度为55 mm时，电容器的温升优化效果最好，所提出的优化方案能够有效降低电容器的运行温度。研究成果对干式直流电容器的温升计算与优化有一定的指导意义。

The accumulation of space charge on the insulation surface can affects the distribution of the total electric field. The surface charge distribution characteristics of dielectrics under negative corona have been studied using spherical plate gaps in this paper. In order to measure the surface potential of three insulating materials under the influence of a DC corona by vibrating electrostatic probe. The experiment tested the surface potential of silicone rubber circular specimen and two umbrella-type disks with different curvatures under negative corona in a spherical gap. Afterwards, a new inversion algorithm was proposed in order to convert the surface potential to a surface charge density. Potential spots were found on the surface of silicone rubber, and the degree of charge clustering of umbrella-type disks was positively correlated with curvature. This experiment will serve as a foundation for future research on the surface charge distribution characteristics of insulation in HVDC corona equipment. Meanwhile, it can also be applied to optimize the insulation design.

鉴于近年来极端天气不断出现,以往的雷电统计规律和趋势与当前的实际情况之间有较大的差异,对线路防雷评估带来较大的误差.通过对华中区域数十条500 kV线路走廊10 km范围内近年的落雷数据进行分析,从含后续回击的主放电、不含后续回击的主放电以及后续回击3种类型分析该区域雷电放电的相关规律,发现含后续回击的主放电次数最少.对不同极性的落雷进行分析,发现负极性放电的比例随放电类型统计方式的不同有很大的不同,正极性放电总数中不含后续回击的主放电占比为79.33％.提出了熵权法,考虑主放电及后续回击参数对线路跳闸的影响,对实际线路的加权计算表明实际线路中雷击跳闸主要是含后续回击的主放电及后续回击引起的,验证了方法的正确性.