Superconducting synchronous condensers have the capability of quick reactive power regulation and play an important role in maintaining the stability of renewable energy grid. In this paper, electromagnetic design of a 50 Mvar, 10.5 kV high temperature superconducting (HTS) synchronous condenser is proposed, and reactive power compensation ability is simulated. For the rotor, only the yoke is retained. The field winding adopts YBCO superconducting coated conductor, and the six racetrack coils of each magnetic pole are stacked radially in a sinusoidal shape. The stator adopts non-magnetic stator teeth, and armature windings are distributed at two layers and composed of thin Litz copper wires. According to the formula derivation and the finite element simulation model, the reactance parameters of the steady-state, transient and sub-transient operation are solved. By changing the magnitude of the field current, the reactive power output performance of the superconducting condenser is obtained. The HTS synchronous condenser is connected to the 330 kV collection station, and the transient response of the HTS synchronous condenser and the conventional synchronous condenser is compared and analyzed when a three-phase short-circuit grounding fault occurs. The simulation results validate the design scheme and provide a theoretical basis for manufacturing a prototype in the future.

Nuclear fusion energy is a sustainable and clean energy alternative and is regarded as one of the best choices to address the global energy crisis and climate change issues. Magnet power supplies are important components in fusion reactors and need to balance dynamic rapidity and stability. Based on the operating parameters of nuclear fusion magnets, this paper proposes a DC power supply topology for fusion magnets and studies its load characteristics through MATLAB/Simulink. Simulation results show that the system has the ability of operating in four quadrants, can maintain stability under different load working conditions, and respond quickly according to the action signals, verifying the feasibility of this topology. Under the condition that the control strategy is proposed, the adjustment duration of the system is approximately linearly related to the inductance of the magnet.

The three-phase coaxial high temperature superconducting (HTS) cable is a promising technology for distribution network expansion in urban center. However, the three-phase coaxial structure of the superconducting cable leads to the asymmetry of the three-phase impedance parameters, which easily cause the unbalanced current in the three-phase conductors and lead to an asymmetric operation problem. A novel two-section three-phase coaxial HTS cable is proposed firstly in China Electric Power Research Institute (CEPRI) with the phase C and shield superconducting layers are divided into two sections, each with a different winding direction, pitch and HTS tape wrapping number, so they have great technical advantages in symmetrical operating performance. For validating, A 5 m, 10 kV/1 kA two-section three-phase coaxial HTS cable is manufactured as well and this HTS cable system is supercooled by LN2 closed loop cooling system with operation temperature of 73 K. The onsite high voltage test platform is set up at a 10 kV substation in Nanjing, China. The current-carrying performances of three-phase and shield layers have been experimental tested in a 10 kV transmission line. The experimental three-phase current asymmetry rate is only 4.1% which is very close to the theoretical value of 1.64%. The comparisons verify the proposed two-section structure and provide an important basis for the practical application of this kind of HTS cable in the distribution power grid.

To identify the key factors contributing to transmission tower failures and evaluate potential mitigation strategies, this study introduces a structural safety assessment framework utilizing Bayesian networks. The research begins with a systematic examination of diverse risk factors that may lead to structural damage in transmission towers, followed by the development of a three-tiered network model grounded in Bayesian causal relationships. The model’s prior and conditional probabilities are quantified through an integrated approach incorporating expert evaluations and fuzzy set theory. A connectivity tree is subsequently generated by constructing a belief map and optimizing the Build Constructive Tree (BuildCT) algorithm through element reduction. The proposed methodology employs both forward and backward inference mechanisms, leveraging real-time monitoring data to determine the probabilistic relationships between causative agents and structural consequences for maintenance purposes. Analytical results indicate that wind-induced conductor displacement presents the highest activation likelihood under certain weather scenarios, consistent with professional expertise. Furthermore, severe wind loads and ice accumulation are identified as primary contributors to conductor separation and structural deformation.

In the future, large-capacity SMES system is expected to play an important role in power grids, where magnet is a key component. The single tape current capacity is difficult to meet operating requirements of large-scale magnets in engineering application. Considering the magnet economic cost, it is not suitable to increase the capacity by increasing the amount of superconducting tapes and reducing the operating temperature. It is necessary to use composite superconducting conductors to increase the current carrying capacity for large-scale magnets application. This paper describes the structure and preparation process of a twisted stacked-tape in tube (TSTT) composite cable with an inner cooling channel. Then a pancake coil was fabricated using a 100-metre TSTT composite cable, and the pancake coil was cooled by liquid nitrogen immersion, with inner liquid nitrogen forced flow cooling environment. The critical current and strain of the pancake coil were measured at 77 K. With the criterion of 1 & micro;V/cm, the critical current was 650 A at 77 K. The trend and magnitude of strain in key components are generally consistent. The experimental results verify the rationality of the design of this TSTT composite cable and provide a valuable reference for large-scale magnet design.

As a new type of distribution pole foundation, the branch and plate belled pile can significantly improve the wind resistance performance, and is especially suitable for use in the coastal strong typhoon landing area. However, there are few studies on the mechanical characteristics and wind-induced response of this type of foundation pole, and the influence of pile-soil interaction on the mechanical characteristics of distribution pole is not considered. Through the establishment of the pole pile soil finite element model, the dynamic characteristics of the new type of electric pole under the elastic constraint of the soil around the pile are analyzed, and the wind-induced vibration response of the consolidation constraint model under fluctuating wind excitation, the elastic constraint directly buried pile model considering the pile-soil effect and the new type of branch belled pile model are analyzed. The results show that the natural frequency of the structure with elastic constraints is lower than that of the consolidation model after considering the pile-soil interaction; compared with the traditional equal diameter pile, the structural stiffness of the belled pile with branches and plates increases slightly; however, the belled pile with branches and plates can increase the area of pile-soil interaction and prolong the time of wind-induced impact, so as to reduce the peak acceleration of wind-induced response and wind-induced dynamic load.

The rapid urbanization has led to a surge in short-circuit currents within the electrical grid, occasionally surpassing the interrupting capacity of circuit breakers. This challenge underscores the critical need to limit fault currents, representing a significant technical and economic issue for power grid management. Superconducting fault current limiter (SFCL) has the advantages of fast current limiting response, self-triggering, low loss and fast recovery, which is an effective solution to the short-circuit current problem. However, the existing SFCLs used in power grids have the problem of costing large amount of superconducting materials, which cannot meet the cost requirements of current limiting in medium and low voltage level lines. The SFCL with current-limiting CORC conductor has higher current-carrying capacity and lower production cost, which is expected to further enhance the reliability and economy of current limiting. Aiming at the current-limiting CORC conductor applied for a 35 kV/1.5 kA SFCL, an FEM model with electric, magnetic, fluid and thermal fields is established in COMSOL Multiphysics so as to explore the multi-field coupling mechanism under steady state and fault condition. Simulation results obtain the critical current, AC loss and magnetic field of the CORC conductor in steady state. Furthermore, The quench operation of the CORC conductor is performed by applying a fault RMS current of 17.5 kA and 1750 A to acquire its electromagnetic and thermal-fluid operation stability. This study explores the application prospect of CORC cable in SFCL and impels the practical application of SFCL.

In order to address the issue of short-circuit fault current limiting in DC power grids, this paper employs a new topology structure of magneto-biased superconducting DC current limiting device with characteristic of automatic triggering, multi-level current limiting, and fast recovery. The current constraining effect was simulated and examined using MATLAB/Simulink platform in DC distribution network models under 10kV voltage level with short-circuit fault at different position. The results show that the current limit effect will change with the location of the bipolar short-circuit fault. In the early stage of fault occurrence, the maxmium current amplitude can be reduced by 20%, and the time when current peak appears will advance, providing important theoretical basis for the factual implementation of superconducting current limiters in DC grids in the near future.

To clarify the disaster-causing factors and preventive measure for the transmission tower, a structural safety assessment method based on Bayesian network is proposed in this study. Firstly, various disaster-causing factors triggering structural damage of transmission towers are systematically analyzed, and three layers network model is constructed based on Bayesian causality. And then, the a priori probability and conditional probability of the network model are quantitatively calculated by combining expert scoring and fuzzy theory. A connectivity tree is formed by building a doxastic map and eliminating elements of the Build Constructive Tree (BuildCT) algorithm. Finally, forward and backward reasoning algorithm using the monitoring data is implemented to capture probabilities of disaster-causing and resulting factors for maintenance. Results shows that the possibility of wind bias tripping is the most feasible factor to be triggered under specific meteorological conditions condition, which is in line with expectation of experts. And strong winds and Serious icing are the key causative factors for tower disconnection and excessive deformation.

A method based on Gabor spectral mode transmissibility functions (GSMTFs) is proposed to detect local damage in a cantilevered structure under nonstationary ambient excitations. Gabor transformation and singular value decomposition are used to reduce the influences of other vibration modes on Gabor spectral mode transmissibility functions and process nonstationary structural responses, respectively. A new state characteristic based on the fundamental structure frequency is formulated on the basis of the GSMTFs, eventually leading to the development of a new damage indicator. The probability density functions of the damage indicator for healthy and damaged states can be estimated from the measured data, and the receiver operating characteristic (ROC) curve derived from these probability distributions and the corresponding area under the ROC curve (AUC) are used to determine the damage location. A six-degree-of-freedom system and a typical transmission tower are numerically studied, and the results show that the proposed method can estimate the structural damage location under nonstationary random loads. The proposed method is further validated with a planar frame in the laboratory, which exhibits multiple damage elements via random force hammer excitations. The results show that the AUC values computed for certain parts of the structure containing the damaged elements are greater than those for other parts of the structure, indicating the effectiveness of the proposed method. Moreover, the proposed method is compared with the dot product difference (DPD) index, and the results from the laboratory planar frame demonstrate that the proposed method can better identify damage.

The rapid pace of urbanization has significantly elevated short-circuit currents in the grid, often surpassing the interrupting capacity of circuit breakers. This has turned limiting fault currents into a significant technical and economic challenge for the power grid. The superconducting fault current limiter (SFCL) offers distinct advantages, including a rapid current limiting response, self-triggering capabilities, minimal losses, and fast recovery. However, current SFCLs used in power grids face challenges related to the substantial use of superconducting materials, which usually exceeds cost constraints in medium and low voltage lines. The high temperature superconducting (HTS) Conductor on Round Core (CORC) cable offers superior mechanical properties and exceptional current carrying capacity. Therefore, the SFCL that utilizes the CORC conductor for current limiting boasts higher current capacity and lower production costs, enhancing both reliability and cost-effectiveness. To ensure the safety and efficiency of the CORC conductor, critical factors such as the critical current and alternating current (AC) loss must be considered when HTS CORC conductors are applied on alternating currents. This paper presents a numerical analysis of the electromagnetic field within an HTS CORC conductor that comprises six superconducting tapes with reversal winding and a stainless steel sheath. The analysis is based on the T-A formulation and finite element method (FEM). The findings indicate the critical current of this CORC conductor is 1070 A. Furthermore, the study reveals the impact of applied current and self-field on AC loss variations and branch shunting between the superconductor layer and stainless steel sheath: when the applied current exceeds 3000A, the current of the sheath layer will exceed that of the HTS layers, achieving the effect of shunt protection. This study paves the way to investigate the feasibility of CORC conductor working for an SFCL.

The main structure of the transmission tower consists of the tower body and the cross arm, which serve as vertical support and transverse extension, respectively. Compared with the tower body, due to the difference between the transverse and longitudinal projected areas of the cross-arm, the wind load distribution of the cross-arm is more complicated and requires more in-depth research. In this paper, wind tunnel force tests under skew wind were carried out on the 1:20 scaled rigid models of the tubular and the tubular-angle combined cross-arms. The tests consider four solidity ratios (0.2, 0.3, 0.4, and 0.5) under three wind speeds and 19 yaw angles. The aerodynamic force coefficients Ci, the skewed wind load factor Kθ, the transversal and longitudinal wind load distribution factor nX and nY, and the angle α between the transversal aerodynamic force coefficient (CX) and the resultant wind force coefficient (CR) were obtained and analyzed. It was found that the wind load coefficients decrease with increasing solidity ratio. The tested drag coefficient of the tubular cross-arm is larger than the combined cross-arm under the same solidity ratio. The nX of the tubular and combined cross-arm reaches the maximum range of 0.33–0.47 and 0.22–0.23 at 30° <θ < 45° and 30° < θ < 35°, respectively. The nY curves were ordered from large to small as follows: EN 50341-1, the tested tubular cross-arm, the tested combined cross-arm, and JEC-127-1979. At 55° < θ < 65°, the difference of α and θ for the tested tubular and combined cross-arm reaches the maximum of 10°–18° and 29°–32°, respectively, indicating that the lift force cannot be ignored and the assumption α = θ is not applicable. Reasonable nonlinear fitting functions are proposed to accurately calculate the wind load of the two types of cross-arms.

The DC superconducting energy pipeline (DC SEP) is a promising technology, which has the ability to transmit electricity and fossil energy such as liquefied natural gas (LNG) at the same pipeline so that LNG could serve as the refrigerant for the high-temperature superconducting (HTS) cables.The collaborative transportation of electricity and LNG increases the efficiency while lowering the cost.However, the operation performance of the SEP, which is crucial for HTS cables and LNG, is of greater complexity on account of multi-physics interactions.Herein, a ±100 kV/1 kA SEP model with electric, magnetic, fluid and thermal fields is established in COMSOL Multiphysics to analyze the temperature distribution of SEP via parametric scanning on SEP heat leakage and LNG flow rate.Finally, the relationship between temperature rise and LNG flow rate of a SEP has been estimated based on the interactions of the multi-physics fields.The results indicate that the temperature rises by 11.6 K for every kilometer of SEP.Moreover, the influences of heat leakage and LNG flow on temperature rise are revealed.Temperature rise increases proportionally with heat leakage and it decreases not monotonously with LNG flow rate.This study validates the feasibility of SEP and provides the theoretical references for the demonstration of SEP.

Typhoon meteorological disasters occur frequently, which seriously threaten the safe and stable operation of old transmission lines. The old transmission towers can be retrofitted with composite insulated cross arms to solve the problems of low capacity of wind protection design and insufficient distance between conductor and ground. The paper analyzes the wind load and bearing capacity of composite insulated cross-arm towers under the action of a typhoon through theoretical calculation and finite element analysis and puts forward the calculation method of wind load under the action of a typhoon, and it is revealed that typhoon has less influence on the force of composite cross arm and greater influence on the deformation of the composite cross-arm. Finally, the bearing capacity of a composite insulated cross-arm tower under typhoon load is proposed.

High temperature superconducting conductor on round core (CORC) cable has superior mechanical properties and current carrying capacity. With the purpose of ensuring the safety and efficiency of CORC cable, the critical current and the AC loss should be considered when alternating current is applied on CORC cable. In this paper, the electromagnetic field of a high temperature superconducting CORC cable wound by six superconducting tapes with reversal winding is numerically calculated using the T-A formulation and FEM. Results indicate that the critical current is 1070 A, and the variation of AC loss according to applied current and self-magnitude is revealed.

The level of fault current increases as urban power grid expands in recent years. The traditional relay protection has difficulties in preventing the increased fault current in power grid. Magneto-biased superconducting fault current limiter (SFCL) is a novel technology with two-stage fault current limiting capability of reducing the level of fault current in the first half of the cycle and further in the second cycle. It consists of a double-split reactor, a non-inductive YBCO component, and a fast circuit breaker. Achieving its coordination with relay protection can reduce the reconstruction cost of power system and contribute to the promotion of SFCL. This paper analyzes the SFCL's operating mechanism at first. Then, a typical 10 kV IEEE 9-bus power system model including the magneto-biased SFCL is built to theoretically investigate the quench and current limiting characteristics and validate the feasibility of SFCL. Finally, a distance protection setting of a simplified 10 kV urban power grid is calculated and the influence of the introduction of the magneto-biased SFCL on the distance protection is quantified. The simulation results of single-phase short-circuit fault show that the zone I and zone II of distance protection can be properly activated and there is little impact on the distance protection of zone III.

In order to realize the technical breakthrough of high temperature superconducting (HTS) cable in large capacity transmission, a new two-section three-phase coaxial HTS cable is studied in this paper. Its structure and parameters were proposed. The current carrying capacity of the HTS cable was verified through MATLAB/Simulink simulation and actual onsite tests. The results showed that the two-section structure of the cable can effectively reduce the shield layer current to less than 3% of the rated current, and reduce the three-phase imbalance ratio to 4.1%, which provides an important data basis for the practical application of this HTS cable in the future.

With the rapid development of distribution system and the integration of distributed generations, the increasing fault current is threatening electrical equipment of the power grid. The superconducting fault current limiter (SFCL) is an effective solution to dealing with the large fault current in the distribution network. In this work, the characteristics of the current limiting impedance of the flux-coupling SFCL is presented. The impacts of the flux-coupling SFCL on the overcurrent protection for distribution system with and without infeed is analyzed. Furthermore, a simulation model of a real 10 kV distribution system with a flux-coupling SFCL is built to verify the analysis. This work is of significance to the coordination between a flux-coupling SFCL and the overcurrent protection for distribution system.

This paper studies the stress state and collapse cause of transmission tower of 500kV Zhangquan II line under the combined action of wind speed, wind direction and wind speed up effect when Typhoon Meranti passes Xiamen. Based on the historical meteorological data and the destruction pattern of the tower, the input conditions of wind speed and direction which are most likely to cause the tower to collapse are determined. Based on CFD simulation analysis, the wind speed-up factor of 24 wind angles at the inverted tower position was determined, and the stress of the main member and inclined member under two wind angles conforming to the site failure pattern was analyzed, and the internal relationship between the failure pattern of transmission tower and wind speed, wind direction and wind speed up factor was clarified. The influence of wind speed, wind direction and wind speed up effect which widely existing in mountainous region should be considered comprehensively in the design of Fujian coastal high voltage transmission line to against typhoon.