Finite element method (FEM) is a general method for solving partial differential equations and is the mainstream numerical solution method in engineering field. This paper reviews the development history of finite element technology, and points out the development direction of finite element technology and the current bottleneck problems. With the development of high-performance computing technology, high-performance computing technology is considered to be one of the important forces to improve the efficiency of finite element computing and to promote the development of finite element technology. This paper introduces the finite element technology under the framework of high-performance computing technology, discusses the key issues of element analysis, stiffness matrix assembly and equations solving, and summarizes the development roadmap of high-performance finite element technology. Finally， based on the characteristics of electromagnetic simulation of electric equipment in power system, this paper discusses the existing problems and possible solutions of electromagnetic simulation of domestic equipment and the development of the novel compuational technique has been prospected.

Digital power equipment is a part of digital power grid. At present, there is a lack of relevant research on the basic composition, quality characteristics, test verification and other issues of digital power equipment. According to the theory of quality management system, combined with the development process of power equipment, the development law of quality characteristics of power equipment is revealed. By combing the current situation of digital, networked and intelligent technology of power equipment, combined with the development law of quality characteristics of power equipment, the basic composition, quality characteristics and digital twin model are put forward. According to the basic concept of digital power equipment, the development path of digital power equipment is clarified.

Prognostics and health management (PHM) of power transformers is of great significance for realizing the transition from traditional regular maintenance to condition-based maintenance and predictive maintenance to ensure the healthy operation. For a long time, the transformer PHM technology has stayed in the theoretical research stage, and there is a lack of an effective technical system and platform to integrate and improve the performance of the research results of each stage. The digital twin (DT) technology strengthens the monitoring and integration of the operating parameters of the transformer’s multi-physical components. Through multi-physical and multi-scale modeling in the virtual space, it realizes comprehensive fault analysis for transformers and has become an important direction for the evolution of transformer PHM. In view of this, the DT technology for power transformer PHM is studied, the connotation is explained, and the DT technology framework, key technologies, challenges and future development trends are summarized. The relationships among DT and its supported data, models, calculations, etc. are analyzed. It aims to provide references for researchers of digital twin technology in the field of transformer operation and maintenance.

The integration technology of building information modeling (BIM) and geographic information system (GIS) has become the management foundation of power grid engineering in planning, design, construction and operation and maintenance stages. However, the electrical equipment is not integrated on BIM and GIS, and the transfer technology of electrical equipment model data between BIM and GIS platforms is lacking. For this reason, the method of graph mapping is used to build the mapping rules between IFC and CityGML (common BIM and GIS data formats) to ensure the accurate mapping between the two organizational structures. The transformation of geometric information and semantics is emphatically analyzed. Considering the differences in organizational structure and information richness between electrical equipment and buildings, the organization form of IFC documents for electrical equipment is analyzed and a conversion framework suitable for electrical equipment is developed. The transformation framework proposed in this paper is extensible and can be used as the basis for building other spatial object mapping patterns in BIM and GIS.

In order to improve the intelligent level of the switchgear, improve the plug and play performance of smart devices, this article focuses on the Internet of Things (IoT) terminal, adopts software to define the system architecture of the terminal, and a variety of sensors detect and acquire various electrical and non electrical information required for operation and maintenance in the switchgear to form an edge sensing data acquisition and analysis processing network with IoT terminals as the core. Intelligent switchgear systems is built for various applications, and research and design of micro application services such as temperature and humidity collection and analysis of switchgear environment, temperature rise assessment, partial discharge analysis and early warning, video image processing around edge computing are carried out, which provides support for intelligent construction of switchgear

Manufacturing digital transformation and standard digital transformation are important parts of the national strategic goals in 2035. Intelligent manufacturing and digital standardization are closely related, thus doing research on their integrated application is conducive to their close combination and in-depth development, and to the digital transformation of manufacturing and standardization organizations. In this paper, a general model combining theory and application for integrating intelligent manufacturing and digital standard are proposed for the first time. More precisely, the model supplies architecture, functional specifications, technical system, implementation strategy and implementation process of intelligent manufacturing and digital standard. The feasibility of the general model is proved by using the concept verification of the digital twin model for the intelligent equipment manufacturing of power transformer. Furthermore, this paper can not only guide the research of electric power equipment manufacturing and standard digitization for power equipment, but also has reference value for standardization of intelligent manufacturing and standard digitization in other industries.

The operation data of the controlled switching devices for capacitor banks is analyzed, from the aspects of phase selection control precision, closing inrush current and operation overvoltage. The differences between phase selection switching and random switching are compared. The effects and existing problems of phase selection switching are analyzed. The operation performance of the controlled switching devices for capacitor banks is summarized, and suggestions for improving the accuracy of phase selection switching and the control strategy are put forward. The results show that the phase selection switching devices for capacitor banks in the substation run well in general, that the operation time of the phase-controlled circuit breaker is stable, that the target angle is controlled accurately and stably, and that the impact of transient effect on the switching and reactive power equipment can be suppressed.

Generation adjustment is one of the frequently used measures to guarantee the safety of the power grid, however, it may encounter difficulties during practical dispatching since the adjusting ability is restricted by various aspects. The issue of generator output limitations (i.e. power congestion) caused by the capacity constraints of transmission channels is discussed. Such constraints are fit into the generation scheduling optimization under certain power grid operation mode, with power transmission maximization of the critical channels and the minimization of generator output adjustments as the objectives. Then the optimization model is supplemented with the statement of the possible special cases which may lead to the failure of searching the limitations. Following with the introduction of medium and long term maintenance plan, the updated optimization model is created and solved to obtain the adapted generation dispatching solution. The example of a provincial power grid verifies the effectiveness of the proposed method, indicated that it can improve the security and economic benefit effectively, relieve the man-power during the calculation, and eliminate the potential faults in manual intervention.

Large capacity multi-HVDCs feed and large-scale new energy grid connection have become the main characteristics of China Southern Power Grid （CSG）, and the problem of frequency stability is increasingly prominent. In order to make full use of the frequency regulation function of the unit under pumped storage pump conditions, a multi-level low frequency integrated stability control system composed of pump cutting and load shedding, wide area low-frequency centralized pump cutting, local low-frequency decentralized pump cutting and low-frequency load shedding is designed. Combined with the operation characteristics of the unit under pumped storage pump conditions, the coordination and cooperation method of frequency stability control strategies at all levels are formed. Based on RTDS system, the hardware on-loop real-time simulation analysis of frequency stability control system is carried out, and the adaptability and reliability of each level stability control strategy are verified in various cases. According to the actual operation of the system, the optimization measures such as exiting the low-frequency slip locking function of the pump storage substation are put forward. The low frequency integrated stability control system has been put into practical operation in the field.

Rational utilization of demand side resources is one of the effective ways to delay distribution network planning and promote wind power consumption. However, the uncertainty of demand response (DR) will have an important impact on distribution network planning. In order to analyze the impact, firstly, in view of the uncertainty of user participation in demand response, the fuzzy model of user response under the time-of-use (TOU) price mechanism is introduced, and the change mechanism of user response rate error is explained. Then, based on the user response fuzzy model, a distribution network fuzzy credibility constraint planning model considering the uncertainty of DR is established; considering the problem that the traditional fuzzy simulation combined with deterministic power flow calculation is inefficient for verifying the credibility constraints, a genetic algorithm with built-in incremental power flow and fuzzy simulation is proposed, reducing the difficulty of solving the model. Finally, the risk assessment indices for the power flow limit violation of the distribution network are established to evaluate the impact of the uncertainty of DR on the safety of the distribution network. Simulation cases show that the proposed model and algorithm can effectively improve the security of distribution network planning, and reduce the risk of exceeding the limits of node voltage and branch power caused by the uncertainty of DR.

Aiming at the problems that the time-varying branch fault rate, the uncertainty of harmonic content and the correlation of random variables affect the accurate calculation of limit line loss, combined with the calculation requirements of flexible interconnected distribution network, a limit line loss calculation method considering multiple uncertain factors is proposed in this paper. Firstly, the improved three-stage Weibull distribution is used to fit the branch failure rate, and the probability distribution model of branch failure rate is established. Combined with the full probability formula, the loss probability distribution considering the time-varying of branch failure rate is solved. Then, the correlation model of the harmonic content of the converter with the transmission power is established to solve the problem that the harmonic can't reflect the influence of harmonic fluctuation on the standard deviation of line loss. Secondly, in order to quantify the influence of the correlation of random variables on the limit line loss, the Nataf inverse transform is introduced to improve the three-point estimation method, and combined with the failure rate probability model and harmonic content correlation model, the calculation method of limit line loss under multiple uncertain factors is constructed. Finally, an example of improved IEEE 33 node system shows that the proposed algorithm has high accuracy and fast calculation speed.

In order to realize the whole process automation of power grid operation, it is necessary to construct a comprehensive general knowledge model in the field of power dispatching operation. In this paper, the intelligent operation knowledge model (IOKM） with good scalability is designed with the machine intelligence of power dispatching operation as the goal, and two knowledge representation modes of hierarchical first-order predicate logic rule base and knowledge ontology are integrated. IOKM is divided into three layers: element knowledge, ontology knowledge and logic knowledge. According to the characteristics of dispatching management, the descriptive attributes and structures of dispatching task ontology, topology ontology and power outage plan ontology are enriched. In order to instantiate the ontology model and apply the rules based on object description to operational examples effectively, this paper proposes a dynamic construction method of fact database. An extensible and concise expression of the priority sequence of operation rules is designed for the synthesis task of operation sequence with time sequence constraints. Taking the actual power outage plan in grid dispatching as an example, the construction and application process of the knowledge model is demonstrated, and the performance of the model is verified.

To solve the problem that high impedance grounding fault of distribution network is easy to be confused with capacitor switching and load switching due to weak characteristics, an identification method based on improved variational mode decomposition and characteristic distribution coefficient is proposed in this paper. Firstly, the variational mode decomposition algorithm is used to deal with the transient zero-sequence current of the line, and several mode components are obtained. Among them, sparrow search algorithm is used to optimize and determine the parameters of variational mode decomposition. Then, the mode with the largest kurtosis is selected as the characteristic mode, the envelope distribution histogram is drawn, and the kurtosis, standard deviation and axial section sampling discriminant coefficient are calculated. Finally, according to whether the comprehensive characteristic distribution coefficient exceeds the threshold value, the high impedance grounding fault and disturbance events can be distinguished under different conditions. The reliability of the algorithm is verified by a lot of simulations on PSCAD/EMTDC software.

Aiming at the problem of low recognition accuracy of power quality disturbance (PQD) in complex noise environment, this paper combines the soft threshold function with one-dimensional convolutional neural network, and proposes a deep convolutional denoising network for power quality disturbance recognition. The soft-threshold function is inserted into the deep network as a nonlinear transformation layer, and a soft-threshold denoising module is constructed to effectively remove noise or other redundant features. Soft-threshold denoising networks are learnable parameters whose weights can be determined through model training. Compared with the soft threshold function, the proposed denoising module can adaptively calculate its thresholds from different sample inputs. The simulation results show that the proposed method can effectively identify 18 common single and multiple PQD in the case of different noise environment. Compared with other common disturbance identification algorithms, the proposed method has better anti-noise and high recognition accuracy of PQD in complex noise environment.

According to the composition of VSC-HVDC transmission for offshore wind power, the monitoring information of offshore wind farm, offshore booster station, offshore converter station, onshore converter station and AC/DC submarine cable is integrated, and a comprehensive integrated monitoring system scheme of VSC-HVDC transmission for offshore wind power is proposed. The architecture, functional requirements, communication mode and security partition are analyzed, so as to realize the operation and maintenance management mode of unattended offshore stations, integrated centralized monitoring system and onshore converter stations. The scheme effectively integrates multiple subsystems such as VSC-HVDC control and protection system, booster station monitoring, wind power prediction, wind turbine monitoring, fault recording, protection and fault information management, electric energy measurement, equipment online condition monitoring, video and environmental monitoring, submarine cable monitoring and so on. It provides a complete monitoring function for the main electrical equipment in VSC-HVDC transmission for offshore wind power, which can realize three applications: real-time monitoring and control, auxiliary monitoring and early warning, production and operation management. The scheme effectively reduces the operation cost of VSC-HVDC transmission for offshore wind power and meets the intelligent operation and maintenance requirements of advanced technology, complete functions and reliable performance.

In order to improve the reliability of power supply, it is more and more common to carry out live work. However, there are few reports on the safe access to the equipotential path on the transmission line under special conditions (with lightning arrester). This paper uses finite element analysis software to establish a calculation model for the equipotential entry of the transmission line with lightning arrester for live work. Taking the common ZB1 tower of the 500 kV EHV transmission line with arrester as an example, the safe access to the equipotential path is analyzed, and the operator enters The possible path of equipotential is the research object. The surface electric field of the operator at different positions is simulated and calculated, and the change law of the surface field strength of the operator entering the equipotential from different paths is obtained; The comparative analysis of the field strength of hands, knees, and feet suggests that it is most appropriate for operators to enter the equipotential safely along the diagonally upward path of the conductor under the two types of working conditions.