Hunan Electric Power

Effect of Organic Pollutant Infiltration on Anti-Flashover Performance of Methyl Silica Superhydrophobic Coatings

WANG Shengwu, ZOU Qiaoge, LI Li, CHEN Junwu, XIE Yi

2023, 43(2): 3-7. doi:10.3969/j.issn.1008-0198.2023.02.001

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The deposition and infiltration of organic pollutants on the surface of methyl silica superhydrophobic coatings will lead to a decrease in the self-cleaning properties of the coatings, which in turn will lead to a decrease in the insulation strength of the coatings under dirty and wet environmental conditions. There is a lack of research on the effect of organic fouling on the insulation strength of methyl silica superhydrophobic coatings. The insulation strength of the coating samples under dirty and wet conditions is reflected by measuring the leakage current amplitude of the coating samples after they are wetted with alkane organic substances in different degrees and ways. The results show that the leakage current amplitude of the surface of methyl silica superhydrophobic coating increases by more than 50% when the infiltration area of organic pollution is increased to 3 times under the experimental conditions. The leakage current amplitude of the coating is decreased by about 16% by increasing the dispersion degree of organic pollution sites. Under the experimental conditions of heavy organic infiltration, the static contact angle and rolling angle of methyl silica super-hydrophobic coating drops are decreased by 10° and increased by more than 7° respectively.

Heater Arrangement Method of 12 kV Switchgear Decondensation Based on Synthesizing Evaluation Function

XU Junwei, SHU Shengwen, ZHAN Zhaoxuan, BIAN Zhiwen, LIN Yihong

2023, 43(2): 8-13. doi:10.3969/j.issn.1008-0198.2023.02.002

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In high humidity environment, the switchgear is easy to get damp and form condensation, resulting in a sharp decline in the insulation performance of the electrical equipment in the switchgear. In order to improve the ability of switchgear to cope with humid environment, this paper takes 12 kV high-voltage switchgear as an example to propose a comprehensive evaluation method of heater layout which considers temperature rise level, temperature rise uniformity and dehumidification capacity. Firstly, based on the comprehensive evaluation method of heater layout, the optimal heater layout test is carried out to select the optimal heater layout scheme. Then, the decondensation test is carried out on the basis of the optimal configuration test of the heater to verify the dehumidification performance of the heater layout scheme in the high humidity environment. Finally, combined with the numerical simulation of temperature-fluid multi-physical field, the distribution of temperature and flow field under the condition of heater installation is studied. The results show that the three 50W heater schemes are the best among the two selection strategies. The optimal heater arrangement scheme can completely remove condensation within 4.5h without causing excessive heating of insulation parts.

Test Analysis of Silicone Rubber Aging Detection Based on Microwave Transmission Method

LI Huihui, ZHANG Boming, LI Zijin, LI Peng, WU Tian

2023, 43(2): 14-18. doi:10.3969/j.issn.1008-0198.2023.02.003

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Aiming at the aging problem of shed and sheath of composite insulator, an aging detection method of silicone rubber material based on microwave transmission method is proposed. The artificial accelerated aging test of silicone rubber is carried out, and the microwave nondestructive testing platform is built to carry out the microwave nondestructive testing test of aging silicone rubber. The variation law of transmission parameter S₂₁ of silicone rubber with different aging degrees is analyzed, and the aging detection mechanism of silicone rubber by microwave transmission method was revealed by numerical simulation. The test results show that after the aging of silicone rubber, due to the change of its dielectric properties, the amplitudes of S₂₁ will change,and the aging degree of sillicone rubber can be identified by the value of ΔS₂₁. The research is of great significance to the aging detection of composite insulators.

Dielectric Properties and Structural Design of Main Insulation for Oil-Impregnated Paper Capacitive Bushing

LIU Daosheng, ZOU Bin, CHEN Xingrong, WANG Shihui

2023, 43(2): 19-23. doi:10.3969/j.issn.1008-0198.2023.02.004

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Oil-impregnated paper capacitive bushing, as one of the core current-carrying components of a transformer, has functions of support, current diversion and insulation. The insulation performance is crucial to the stability and safety of transformer operation. In order to reduce insulation faults caused by oil-paper partial discharge during the operation of oil-immersed paper bushings, this paper adopts nano-modulation technology to improve the dielectric and electrical properties of oil-immersed insulating paper for the main insulation of bushings. Taking 20 kV oil-paper capacitor bushing as the research object, a combination of simulation and experiment is used to investigate the effect of nanoparticles on the electric field distribution and partial discharge initial voltage of the main insulation of the casing core. The experimental results show that the nano-TiO₂ particles can improve the surface microstructure of insulating paper, reduce the relative dielectric constant and the peak electric field intensity in the casing core, and increase the partial discharge initial voltage of the casing core. This provides a reference for improving the insulation performance of oil-paper capacitive bushings.

Electromagnetic-Fluid-Thermal Field Analysis of Power Cable under Vertical Laying Mode

QU Bo, YANG Juntao, LI Xin, XIANG Xingyao, SHU Shengwen

2023, 43(2): 24-31. doi:10.3969/j.issn.1008-0198.2023.02.005

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The temperature distribution is one of the key factors that determine the operation of the power cable, and it is mainly affected by the running current, the laying mode and the operating environment. In order to study the temperature distribution characteristics of cables under the vertical laying mode, the paper takes the cable shafts of high-rise buildings as the research object, and builds a simplified three-dimensional multi-physics simulation model of the cable shafts. The finite element method is used to calculate the fluid and temperature distribution inside the cable shafts, and the temperature variation trend is analyzed. Then, the influence of factors such as running current and fire blocking material on the temperature distribution of the cable is comparatively studied. The research results show that compared with the horizontal laying mode, the vertical laying of the cable is more susceptible to the influence of the air flow in-side the cable shaft, resulting in a large difference in the temperature distribution between different parts of the cable. At the same time, the increase of load current and the addition of fire blocking materials will cause the increase of cable temperature and the change of temperature distribution between different floors.

Day-Ahead Scheduling of Integrated Electric Heating System Considering Thermal Inertia

DAI Mengdi, KE Deping, SONG Lin, WANG Huiji

2023, 43(2): 32-38. doi:10.3969/j.issn.1008-0198.2023.02.006

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For the problem of optimal scheduling of integrated energy systems involving wind power consumption, a stochastic optimal scheduling strategy with systematic consideration of mixed uncertainties is proposed by mining multiple thermal inertia. The thermal inertia of the network based on the dynamic characteristics of the heat network and the thermal storage characteristics is explored, the thermal load elasticity constraint is introduced into the modeling of thermal inertia of buildings, and heat pumps and thermal storage are used as time-shiftable electric loads and heat sources, which are jointly modeled with CHP units to solve the peak-valley mismatch of electric and thermal loads.On this basis, the IES model considering multiple thermal inertia is established, the coupled system of 33-node heat network and 9-node grid is used as an example for the analysis. And the traditional heuristic particle swarm algorithm with the mixed integer nonlinear programming algorithm is compared. The results show that by mining the multiple thermal inertia to broad the flexibility of the energy system, the complementary aid and flexible dispatch between multiple heterogeneous energy sources can be realized, and the mathematical planning algorithm can effectively improve the solving efficiency far than the particle swarm algorithm.

Control Strategy of LCL Grid-Connected Inverter Based on Improved Weighted Current Control

LING Zhiyong, ZHOU Zhifei, LI Shengqing, YAO Hongde

2023, 43(2): 39-45. doi:10.3969/j.issn.1008-0198.2023.02.007

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Aiming at the problems that the traditional weighted average current (WAC)control strategy does not consider the digital control delay, and causes the phase lag of the system, which leads to the reduction of system bandwidth and poor robustness, the WAC control strategy of combination of quasi-proportional resonance control and lead compensator is proposed. Firstly, the capacitor current feedback is introduced to suppress the reverse resonance peak. Secondly, the lead compensator is connected in series at the transfer function of the inverter bridge to improve the phase margin of the system. Finally, the quasi-proportional resonant controller is used as a current regulator to Increase the fundamental frequency gain and reduce the static error of the system. It is verified by simulation that the proposed control strategy has good adaptability to weak power grids, and the harmonic distortion rate of grid-connected current is reduced from 1.84% to 0.26%, thereby enhancing the robustness of the system and improving the quality of grid-connected current.

Numerical Research on Plastic Zong at Crack Tip of Superheater Tube for Supercritical Critical Boier

DENG Ping, TANG Zhihui, LIU Zhili

2023, 43(2): 46-52. doi:10.3969/j.issn.1008-0198.2023.02.008

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For ultra-supercritical boiler of a super-heater tube with cracks, the stress-strain field at the crack tip is analyzed by numerical simulation under high temperature and high pressure for a long time. According to the theory of plastic zones, the size of the plastic zone at the crack tip is estimated, and a finite element method for calculating,the size of plastic zone is proposed. The research results indicate that the stress and strain, as well as the size of the plastic zone at the crack tip are related not only to the internal pressure but also to the temperature. At a certain temperature, the plastic strain increases with the increase of internal pressure and when the internal pressure is constant, the plastic strain increases with the increase of temperature. Under high temperature and high pressure for a long time, there is some difference between the result of finite element method and that of plastic zone theory, and the reason of the difference is analyzed. The plastic zone at the crack tip is evaluated by using a small range of yield conditions under high temperature and high pressure for a long time, it is shown that the stress intensity factor K is an appropriate fracture parameter for the fatigue crack growth of the T92 superheater tube.

Summary of Reliability Research on High Voltage Electrical Device in Substation

MA Zhaoxing, CHEN Hao, TANG Yi, SHA Haoyuan, JIANG Minyi

2023, 43(2): 53-59. doi:10.3969/j.issn.1008-0198.2023.02.009

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Based on the reliability research of high-voltage electrical equipment in substations, this paper introduces the development of the reliability research of high-voltage electrical equipment, discusses the reliability analysis methods of common electrical equipment, and compares the advantages and disadvantages of the analytical and analog methods, the optimal application situation is analyzed, and the combination method and state method under complex system are studied. The future trend of reliability analysis based on multi-methods cross-fusion is prospected.

Analysis and Research of On-Line Energy Consumption Monitoring Model for Thermal Power Units

NIE Tao, SHAO Feng, YANG Wenzheng, HE Xinrong , WANG Zhong′ao

2023, 43(2): 60-65. doi:10.3969/j.issn.1008-0198.2023.02.010

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Because of the limitation of on-line energy consumption measurement condition and instrument measurement precision, the coal consumption of on-line monitoring system usually has big error.To solve this technical problem, this paper adopts the state equation of thermal economy of power plant to dynamically solve the steam turbine heat rate, applying the idea of energy mass balance, the steam water distribution matrix equation of the whole thermal system is established.At the same time, the dynamic fluctuation characteristics of boiler efficiency are deeply studied, the factors of coal quality ash and heat dissipation are analyzed , the theoretical calculation models of exhaust heat loss, solid incomplete combustion heat loss and heat dissipation loss are established.For the dynamic calculation of auxiliary power consumption rate, the emphasis is on the accuracy of the electric meter and the allocation method of the public part of the power supplied to the factory. The online calculation accuracy of the unit energy consumption model is verified and the test results show that the on-line energy consumption calculation and monitoring model can meet the accuracy requirements of ASME standards.

Development of Mobile Energy Storage Vehicle Based on Super Capacitor Battery

WU Chuanping, ZHOU Tiannian, LIU Yu, ZHU Hongzhang

2023, 43(2): 66-70. doi:10.3969/j.issn.1008-0198.2023.02.011

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Aiming at a new type of mobile energy storage vehicle using electrical double-layer capacitor, this paper introduces the electrical double-layer capacitor characteristics, the structure of mobile energy storage vehicle and the electrical double-layer capacitor package assembly scheme, puts forward the control method and working mode of energy storage power converter, designs the fire protection system of the device, and carries out the functional test on electrical double-layer capacitor mobile energy storage vehicle. The test results show that electrical double-layer capacitor mobile energy storage vehicle runs well in charging, discharging and islanding mode when connected to the grid, with high energy conversion efficiency and good application prospects.

10 kV Feeder Load Forecasting Method Based on Double Layer Mapping

GUO Lu, LIU Yongli, LI Longfei, HE Ming, YANG Huimin, ZHANG Yuan, WU Qian

2023, 43(2): 71-78. doi:10.3969/j.issn.1008-0198.2023.02.012

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Feeder load is very important for distribution system planning, safe operation, equipment maintenance and load analysis, etc. This paper uses the spatial load forecasting method to indirectly realize electrical load forecasting, which is suitable for the load forecasting of 10 kV feeders under the situation that the purpose of spatial land is clear, the historical data of parcel load is sufficient, but the historical data of feeder electrical load is relatively lacking. According to the“component-parcel”spatial membership relationship, the micro electrical load forecasting based on the feeder segment is indirectly realized by means of the spatial parcel load forecasting, and further summarizes the medium and long-term loads of the entire 10 kV feeder line. The core idea is to first map the electrical load of the current year to the spatial load, and then obtain the spatial load of the required planning year through the spatial load prediction, and then map the spatial load of the planning year to the electrical load, and finally summarize the predicted load of the feeder. The results of the example are compared with the existing mainstream forecasting methods and the actual load collection data respectively. It shows that the proposed model and calculation method meet the accuracy requirements of distribution network planning, and it is practical and effective.

Method of Distribution Network Voltage Stability Weak Bus Identification Based on Characteristics Curvature

SUN Jingliao, HU Changhong, CHEN Mengxiang, XIANG Yejun, LIU Jinyuan, ZHU Qiwei

2023, 43(2): 79-84. doi:10.3969/j.issn.1008-0198.2023.02.013

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In this paper, a method for identifying voltage weak bus in distribution network based on the characteristic curvature is proposed for the determination of voltage stability weak bus. The P-V curve of network bus is generated by the extended power flow method, and the sensitivity index based on the average change rate of the active power-voltage curvature radius is established. K-means clustering is used to classify the sensitivity indexes of distribution network bus, and the evaluation indexes of weak bus are defined to classify and sort the weak. The reactive voltage compensation point is confirmed according to the weakness degree. Simulation experiments based on IEEE 33 node system verify the effectiveness and rationality of the proposed method.

Device of Earth Wire Arc Preventing in 500 kV Substation under Strong Induced Electricity Environment

ZHANG Yunxiang, WANG Yu, SHENG Huan, LI Sipei, CHEN Hao, ZHU Kai, HE Jiahong

2023, 43(2): 85-89. doi:10.3969/j.issn.1008-0198.2023.02.014

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The induced voltage of the electrical equipment is too high during the overhaul.When the grounding switch can not be operated, it is necessary to connect the temporary grounding wire. The arc fault will affect the safe operation of the equipment. In this paper an anti-arc device for temporary grounding wire hanging is developed, and a grounding wire switching system based on the current limiting reactor is presented. This system can compensate the instantaneous current, and reduce the overvoltage level. Moreover,when the overvoltage is limited to a reasonable value, the grounding state is switched to direct grounding by control system. The application results show that the device can prevent the grounding arc caused by the induced voltage in the grounding process effectively,has the advantages of convenient installation and high security,and improve the efficiency greatly.

LCL Solar Inverter Control Design for Weak Power Grids

ZENG Lin, ZHU Zan, XU Yong, XIANG Yunkun, HE Zhe

2023, 43(2): 90-96. doi:10.3969/j.issn.1008-0198.2023.02.015

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The connection of a distributed generation (DG) unit to a weak power grid is challenging due to stability issues resulted from the uncertainty of system impedance. This paper designs controller to improve the performance of grid-connected current feedback control based on μ method. In order to decouple active and reactive components in control system, a multi-input multi-output model reflecting the interaction between the components of d and q is established. The decoupling requirement, together with steady-state error and overshoot is transformed into the design problem of controller. By employing the μ method, the paper designs a robust feedback controller to meet the all requirements. Simulations show that the controller not only guarantees the robust stability and robustness of the system under the uncertainty of the inductance of the power grid, but also realizes the decoupling of the d and q components of the current.

Research on Monitoring and Management of Wind Power Generation Capacity in Hunan Power Grid

CHEN Haoqi, WU Yuxiang, FAN Jiahong, QIAN Jun, CHEN Bin, ZHU Shu, ZHANG Jinfan

2023, 43(2): 97-101. doi:10.3969/j.issn.1008-0198.2023.02.016

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In view of the current situation and existing problems of wind power capacity monitoring technology in Hunan power grid, a wind power capacity monitoring algorithm and system architecture based on abnormal data identification are proposed. The feasibility of the algorithm is verified by historical data, which realizes real-time monitoring of wind power plant capacity and automatic detection and identification of wind power plant abnormal data.Based on the monitoring system, the supporting management suggestions are put forward to scientifically guide the improvement of the wind power management level of Hunan power grid, which can improve the wind power supply support ability and promote the development of wind power anti-ice technology.

Power Flow Calculation Method in Loop-Closing Distribution Network Based on Bus Voltage Phasor Acquisition

CHEN Chenggong, ZHU Yulan, PANG Muchan

2023, 43(2): 102-107. doi:10.3969/j.issn.1008-0198.2023.02.017

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The traditional calculation method relying on power grid modeling and parameter accuracy is not suitable for the power flow calculation in loop-closing distribution network.To solve this problem, a new power flow algorithm based on bus voltage phasor acquisition is proposed, which can realize the on-line calculation of power flow in distribution network conveniently. The on-line computing module developed based on the algorithm has a good effect, which verifies the validity and practicability of the algorithm.

Prediction of Power Transmission Project Cost Trend Based on Big Data

DENG Yiqing, SUN Bin, LI Xiaobing, LI Dan, WANG Rongjing

2023, 43(2): 108-111. doi:10.3969/j.issn.1008-0198.2023.02.018

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In order to accurately predict the cost of power transmission and transformation projects, control the cost investment in the construction stage, and improve the utilization rate of funds,based on the actual cost data of power transmission and transformation projects in different cities in Shaanxi province, the key influencing factors of power grid project cost are screened by using the entropy weight method, and the BP neural network forecasting model is used to predict the cost of transmission and transformation projects effectively. The forecasting results confirm the validity of the model.

Analysis on Influence of Separate Operation of 500 kV Bus of UHV Xiaoxiang Station on Hunan Power Grid

LIU Yongyan, GAN Wangwei, ZHANG Yan, XIAO Pei, CUI Ting, GUO Hu

2023, 43(2): 112-116. doi:10.3969/j.issn.1008-0198.2023.02.019

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After the commissioning of the 1 000 kV UHV AC double-circuit line from Xiaoxiang—Ganjiang, the reactive power support capability of the inter-provincial AC channels has been enhanced, and the system stability has been enhanced, but it also leads to the increase of the system short-circuit current. In order to ensure the transient voltage stability of Hunan power grid, it is still necessary to put forward the requirements for the start-up and rotation of units in the province, which limits the power supply capacity and operational flexibility of the power grid. Aiming at this problem, the optimization of 500 kV grid structure in Hunan power grid is studied, and the optimization scheme of 500 kV bus-bar operation in UHV Xiaoxiang station is put forward to reduce the impact of near-area short-circuit fault on the system. It can improve the transient voltage stability level and the power supply capacity of power grid, and provide technical support for the safe and stable operation of Hunan power grid.

Analysis of Common Problems for Current Transformer Secondary Circuit

YANG Qi, WEI Dong

2023, 43(2): 117-120. doi:10.3969/j.issn.1008-0198.2023.02.020

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Aiming at the problems of open circuit of phase current or neutral line current in secondary circuit of current transformer and two-point grounding of circuit under different working conditions, the method are put forward that under abnormal operating conditions such as inrush current and out-of-area fault, the amplitude and phase of the secondary current of different windings, the self-produced zero-sequence current and the external zero-sequence current are compared and analyzed, and the secondary current is correctly connected to the fault recorder, and consummates the inspection work measure ticket and so on. At the same time, the magnetic circuit characteristic of multi-tap transformer is analyzed, and the conclusion that secondary tap does not need short connection is obtained. The integrality of the secondary circuit of the transformer is ensured by the above methods, and the operation reliability of the secondary circuit is improved effectively.

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