With the large-scale high-voltage direct current(HVDC) infeed, the safety, stability and economic operation of the receiving-end power grid is facing greater challenges. Therefore, this paper establishes a power grid optimal dispatch model considering the stability constraints of large-scale HVDC infeed, and puts forward a HVDC tie-line power optimization mode that comprehensively considers clean energy consumption and economy of the sending-end and receiving-end power grids. The model can consider the HVDC adjustment capacity and adjustment cost of the sending-end grid, the adjustment capacity and consumption demand of various resources such as wind, thermal and hydro in the receiving-end grid, safety and stability constraints on the coupling relationship between the HVDC transmission power and the startup mode of thermal units in the receiving-end power grid. By optimizing and adjusting the power of the HVDC tie-line, the model takes into account the operating economy of the sending-end power grid, the safety, stability and the demand for clean energy consumption of the receiving-end power grid. Based on the actual operating data of a domestic power grid, the validity of the established model is verified.

The transient overvoltage problem of HVDC sending system caused by HVDC blocking fault may threaten the safety of the large-capacity and long-distance transmission across regions. At present, the configuration of synchronous condenser in converter stations is recognized as one of the means to reliably solve the above problem. In order to coordinate the planning of capacitor and synchronous condenser in converter station from the perspective of economy, this paper firstly analyzes the mechanism of suppressing transient overvoltage caused by HVDC blocking fault using synchronous condenser. Furthermore, this paper puts forward a transient overvoltage calculation method of converter bus based on sub-transient power flow, and applies this algebraic analytical cal-culation method to the coordinated planning of capacitor and synchronous condenser capacity in converter station to meet the voltage control requirements during normal steady-state operation and after HVDC blocking fault. Finally, the simulation results verify the efficiency and accuracy of the transient overvoltage calculation and the corre-sponding reactive power planning methods proposed in this paper, and at the same time illustrate the economy of voltage management and control realized by the cooperation of capacitor and synchronous condenser in converter station.

In recent years, with the blowout development of ultra-high voltage transmission technology, it is imperative for the localization of high-voltage AC cable material. In this paper, the performance differences among the XLPE insulation material at home and abroad are analyzed in brief. A new domestic 220 kV high-voltage AC crosslinkable polyethylene cable material is developed by structure adjustment of molecular chain of resin, improvement of processing technology and the impurity control. A series of performance comparison are made among the new domestic developed insulation material and the imported materials with the same grade. The results show that the new domestic 220 kV high-voltage AC crosslinkable polyethylene cable material is basically the same as the imported products in electrical, mechanical and thermal properties. And all property parameters meet the Chinese national standard. At present, the 220 kV XLPE cable extruded by the above material has passed the relevant property testing and technical appraisal, and has been put into operation on the demonstration project of 220 kV Jingmao to Shuibei cable line in Shenzhen. The cable line is running in good condition until now.

Due to the limitations of test equipment, test methods and environmental factors, when the 50% discharge voltage of long air gap is measured in the test, the results deviate from the objective truth values. Taking the long gap discharge test of the valve-tower grading shield to the ground as an example, this paper establishes an uncertainty analysis method of U₅₀ measurement by "up-and-down method", calculates and analyzes the uncertainty of the test results from the aspects of statistical methods, high-voltage generator measurement systems, temperature and humidity changes during the test. The calculation and analysis show that the uncertainty of the test result is in the same order of magnitude as the deviation of the calculation result of the existing long air gap discharge voltage calculation model. When verifying the validity of the calculation model, it is necessary to take the uncertainty of the test value into consideration. The uncertainty introduced by the high-voltage generator measurement system is the largest. Improving the measurement and control accuracy of the high-voltage generator, and appropriately reducing the voltage difference of up-and-down method can effectively reduce the measurement uncertainty of 50% discharge voltage.

With the development of power electronic devices towards high frequency, large power and lightweight, high frequency becomes one of the important reasons of the high frequency transformers failures. In this paper, a high-frequency electrical aging experiment system is built, and the surface potential attenuation method is used to measure the surface charge accumulation and attenuation characteristics of oil paper insulation with different aging degrees. The results show that as the applied frequency increases, the amount of charge accumulated on the surface of the insulating paper decreases, and the charge attenuation rate increases first and then decreases. After high-frequency aging, the surface charge accumulation and attenuation rate of oil-paper insulation decreases with the increase of aging degree. When the frequency is lower than 5 kHz, the high-frequency heating effect on the surface of the insulating paper plays a leading role, and when the frequency is higher than 5 kHz, the charge dissipation time caused by the high frequency plays a leading role, causing the surface charge attenuation rate to increase first and then decrease. As the degree of high-frequency electrical aging increases, the probability of initial electron generation of oil-paper insulation decreases. Understanding the characteristics of surface charge accumulation and dissipation provides a theoretical basis for revealing the electrical aging mechanism of oil-paper insulation under high frequency.

Oil immersed transformer will inevitably have various latent faults during operation, it is very important to diagnose the state of transformer in time and correctly. The traditional three ratio method based on DGA data has insufficient coding, which limits the effect of fault diagnosis. In this paper, an improved manta ray foraging optimization (MRFO) is proposed to optimize the back propagation (BP) fault diagnosis model. Firstly, the algorithm uses the multi-stage algorithm integrating logic mapping and opposition based learning (OBL) to provide the initial position for MRFO and strengthen the global optimization ability of the algorithm. At the same time, three foraging strategies of manta ray algorithm are optimized by orthogonal experiment to adjust the individual exploration and development of manta ray, so as to strengthen the optimization ability of the algorithm on specific problems. Finally, the optimal solutions obtained by the improved manta ray algorithm are given to the weight and bias of BP network, and the transformer fault diagnosis system is established. Experiments are carried out using IEC TC 10 fault data, and the results are compared with the other algorithms, which show that the accuracy of the algorithm proposed in this paper is 16%, 8% and 24% higher than those using BPNN, unmodified MRFO-BP and three ratio method respectively.

A method of Wasserstein generative adversarial network with gradient penalty (WGAN-GP) data enhancement method for pattern recognition of partial discharge (PD) is proposed. Firstly, denoising and pulse extraction are carried out to obtain local emission pulse signal. Secondly, Wasserstein distance and gradient penalty function are introduced into generative adversace network (GAN) to improve the training stability of the generated model and the diversity of generated samples. Partial discharge pulse signals are used as samples to train the network to realize the enhancement of partial discharge data based on WGAN-GP. The proposed method is used to enhance the partial discharge sample data, and the enhanced partial discharge samples are used to train the common pattern recognition algorithms. The experimental results show that compared with traditional data enhancement method, the proposed method can more effectively enhance the partial discharge pulse sample data, the recognition accuracy of the data discharge pulse pattern can be increased by 12.9%.

The tension clamp of transmission line transmits the load of the ground wire to the tower, which is the key bearing part of the line and generally processed by crimping technology. In the process of engineering operation, the failure of the crimp type tensioning clamp often occurs due to the crimp defect, resulting in serious accidents. In this paper, the grip force experiments of NY400/35 type wire clip with normal crimping and crimping defects are carried out. The failure process and force transmission characteristics of wire clip are studied by using displacement and strain experimental data. The results showed that steel core and aluminum tube in the wire clip are subjected to wire tension simultaneously, and the wire clip is subjected to load: There are two paths for force transmission, one is steel anchor-aluminum tube-wire aluminum strand, the other is steel anchor-wire steel core; Insufficient threading length will lead to reduced contact area between steel core and steel anchor threading tube and reduced grip force, resulting in steel core pulling out of steel anchor threading tube, thus reducing grip force of tension-resistant clamp. When there is insufficient pipe length defect, the load of aluminum tube will increase by about 44.5%; When the pipe length is greater than 50 mm, the grip strength of the strain clamp can meet the specification requirements.

The development of new power system requires higher efficiency of power system simulation. In order to effectively deal with the massive computing needs from multiple users, this paper proposes a construction scheme of power system computing and analysis platform based on modern internet technology. Based on the leading Kubernetes cluster management system and docker container deployment technology, a real-time dynamically scalable cluster system architecture is proposed to construct an efficient, reliable, green share computing platform. The platform has been deployed in Power Dispatch and Control Center of China Southern Power Grid, and the reliability and efficiency of the system are verified by the actual data. Results show that the efficiency gain is close to the upper limit of the theoretical optimal value. The platform provides a powerful computing system to the operators at grid, province and city level dispatching departments, and provides technical support for resource sharing and integrated management.

How to build a scientific and reasonable black-start and system recovery scheme has always been one of the urgent problems to be solved in power grid. The paper innovatively develops a complete set of auxiliary decision-making system for black-start and system recovery of power grid, which is applied to practical engineering to verify its feasibility. Firstly, the architecture of this auxiliary decision-making system is introduced. And then, its functional modules and algorithms of the system are presented in detail, mainly including: 1) The construction of the optimal partition model considering the influence of parallel recovery process of subsystems and its solution strategy; 2) The making of black-start paths of each partition; 3) The construction of complete system recovery model with the minimum of the sum of power outage loss and total network loss as the objective function and its solution strategy; 4) The conducting of synchronous parallel among subsystems so as to achieve a comprehensive recovery of power grid. Finally, the system is applied to Central China Power Grid, and a complete set of black-start and system recovery scheme for Central China Power Grid are formulated. At present, this scheme has become the actual emergency plan of Central China Power Grid.

With the development of grid-load intelligent interaction, the connection between grid side and load side has gradually deepened. Based on grid-load interaction, this paper sets the power shortage and load shedding rounds by integrating grid frequency and voltage. Since the traditional intelligent algorithms have slow convergence speed and fall into local optimal solution easily, an improved firefly algorithm is proposed to improve the search speed and global optimization ability. And on this basis, an optimized load shedding strategy with the goal of minimizing the actual load shedding is proposed. This strategy takes into account constraints such as grid real-time frequency and voltage, which can effectively improve the lean level of emergency control of the grid load. Finally taking the actual grid in a certain area as an example, the simulation results show that this proposed strategy can effectively improve the speed and accuracy of the load shedding action in emergency situations, and ensure the safe and stable operation of the grid.

The complex spatial electromagnetic disturbance of GIS substation will be coupled and invades the sink node equipment of the wireless sensor network of intelligent substation, resulting in packet loss, bit error and abnormal operation. In serious cases, it will cause permanent damage to the equipment and the collapse of the entire wireless network system. Several smart substations with different networking types are investigated in this paper, and the induced currents of communication lines and power lines of sink node equipment in a 110 kV smart substation are measured under steady-state conditions; The coupling mechanism between space electromagnetic field and sink cables is analyzed; The near-field and far-field coupling model of the communication line and power line of the sink node is established, and the induced voltage of the core wire is calculated; The noise tolerance of the internal circuit devices is proposed to judge the interference degree of the core induced voltage to the sink node. In this paper, the reliability of the sink node in the complex electromagnetic environment is analyzed and suggestions are put forward to provide technical support for promoting the large-scale construction of the power Internet of Things.

Aiming at the abnormal heating of the cable armoring layer grounding line adjacent to the reactor in a 500 kV substation, the models of three-phase reactor, cable armored layer and cable terminal are established, the finite element numerical calculation method is used to analyze the abnormal rise of cable grounding line current and cable terminal temperature. The error between the calculated and measured values of grounding line current is 1.8%, the error between the calculated and measured maximum cable terminal temperature is 3.6%, which verifies the correctness of the model and method, and on this basis, the effect of the magnetic shield on the grounding line current under different placement methods and the heat generation of the magnetic shield are discussed. The results show that laying round and T-shaped magnetic shield at the bottom of the three-phase reactor can effectively reduce the cable grounding current value, and the increase of the magnetic shield area can significantly improve the shielding effect, the magnetic shield will not produce abnormal heat and can be used safely.

The operation stability of renewable power system presents new forms and characteristics, and subsynchronous oscillation is one of the representative problems. The influence factors of subsynchronous oscillation propagation path are complex. This paper studies the subsynchronous oscillation power and its propagation characteristics, and proposes an algorithm for the dominant component of subsynchronous oscillation power. The algorithm starts from the complete definition of subsynchronous oscillation power, characterizing the propagation of subsynchronous oscillation by the amplitude of AC component and analyzing the propagation characteristics afterwards. The proposed algorithm decouples the power frequency component and subsynchronous oscillation component in the expression through mathematical derivation. Finally, the effectiveness of the algorithm is verified by a two-machine five-node case.

In order to study the impact of the uncertainty of wind power forecast errors on the economic dispatch of the power system, firstly, the improved Gaussian mixture model is used to characterize the uncertainty of wind power forecast errors. According to the model, using Latin hypercube sampling generate the scene, and the improved K-means clustering is used to reduce the scene to obtain the initial scene and probability. Since the initial probability has a certain degree of randomness, the comprehensive norm is used to obtain its uncertain set. Then, to promote the consumption of wind power, the impact of energy storage and time-of-use electricity prices are considered at the same time during the dispatch process, and finally a min-max-min two-stage economic dispatch model is constructed. The first stage takes the start-up and shutdown cost of the unit as the goal, and the second stage searches for the optimal operating cost under the worst probability distribution based on the uncertainty set, and uses the column constraint generation algorithm to solve the model. Finally, the IEEE 39-node system is used to prove the effectiveness of the model and algorithm.

The traditional transmission pricing method is based on the annual peak load model, which is difficult to adapt to the new development situation of the large-scale access of renewable energy and the deepening of the power market reform. Therefore, a new method based on the correlation load model is proposed. Using multi-variable kernel density estimation and multi-dimensional normal distribution sampling technology to build a data-driven correlation load model, sample the node load vector sample space, reduce the lack of random distribution artificial assumptions, and better simulate the system node load correlation according to the law of random change. On this basis, multiple typical operation modes are formed during the peak load period of the system, the source flow analysis method is used to evaluate the grid usage share of the single operation mode, and the transmission cost is comprehensively allocated with probability weighting to establish a fair transmission price. The IEEE RTS-79 node system calculation example verifies that this method can more truly and comprehensively reflect the use share of transmission equipment, which is conducive to achieving fair pricing and adapting to the new pattern of green and market-oriented power system development.