Search

With the increase of urban power grid scale, the requirement of power supply reliability has been improved, and the active intervention type arc extinguishing device (AIT-AED) has been paid more and more attention to. As one of the effective means of grounding fault arc extinguishing, the AIT-AED has a high demand on the operation reliability, but the operation experience of AIT-AED is insufficient. Hence, the pilot application of this device was carried out and its operation situations were investigated in this paper. It is found that the setting value, control logic, accessories quality and artificial operation are the main influencing factors of operation reliability and the corresponding improved measures were proposed, which could provide references for the operation and maintenance of AIT-AED.

Due to the large amount of data information in the Gas insulated switchgear (GIS) partial discharge defect sample database, if the analysis and diagnosis are directly carried out, there will be problems of slow data mining speed, poor efficiency and low accuracy. Therefore, further research is needed to apply to different types of insulation partial discharge data abnormalities of GIS equipment. The typical feature mining and fault diagnosis method of the state. First, Use the Association analysis rules and the neural network to make a data cleaning strategy to clean and normalize the sample data. Then use the self-learning algorithm evolution mechanism to train the deep neural network, update the model parameters, and continuously modify the abnormal state data of the sample library, and build the GIS equipment insulation defect partial discharge data sample knowledge base. Finally, a deep belief network partial discharge signal diagnosis neural network learning model and optimization technology based on deep learning are constructed to improve the adaptability and generalization of different types of partial discharge signal map diagnosis of GIS equipment, as well as the intelligent diagnosis speed and abnormal state information accuracy.

Large crossing overhead transmission lines are usually erected on the ultra-high towers with long span, and its lightning withstand performance should be paid more attention to. Considering the propagation process of lightning current along the high tower, an improved simulation model of back striking was established by using the electromagnetic transient program, and then the lightning withstand performance of back striking under different conditions for the ± 1100kV UHVDC large crossing line were studied. The results show that comparing with the conventional transmission line for the ±1100kV UHVDC project, the large crossing section has a much lower lightning withstand level of back striking (LWLBS); The LWLBS for the large crossing line with high tower is not significantly affected by the footing resistance, while enhancing the insulation level can effectively improve the LWLBS. Furthermore, the LWLBS increases with the increase of the distance between striking point and the tower when lightning strikes the large crossing overhead ground wire.

In this paper, the effect of the curing process on electrical properties of superhydrophobic antifouling flashover coatings was studied, which electrical properties include, the volume resistivity (ρ v ܄ ), the electrical strength (U B ), relative permittivity (e r ) and the dielectric dissipation factor (tanδ). This kind of superhydrophobic coating uses modified SiO 2 and TiO 2 particles to construct micro-nano composite structures on the surface of FEVE fluorocarbon resin, and its surface has superhydrophobic characteristics. The results show that, as the addition amount of curing agent increases, ρ v܄ first increases and then decreases, and when it reaches 16%, it reaches the maximum value, while e r and tanδ increase simultaneously. As the curing time increases, ρ v܄ and U B increase, and e r and tanδ decrease. However, after full curing, curing time has little effect and curing temperature only affects e r and tanδ. With the increase of curing temperature, e r and tanδ decreases rapidly and then becomes stable. N3390 trimer and N3375 trimer have a relatively high ρ v܄ and U B . Their e r and tanδ are relatively high. N3390 trimer has the highest ρ v܄ and U B . N75 biuret has a minimum e r and tanδ, and its ρ v܄ and U B are relatively small.

In this paper, the composite insulators with different operating times were used as samples. The relationship between transverse relaxation time, Si-CH3 absorption peak area and operating time was analyzed by NMR and IR spectroscopy. The normalized method was used to compare transverse relaxation time and Si-CH3 absorption peak area, where the results showed that the two have obvious linear correlation, reflecting the consistency of the aging of insulators. Finally, according to the hydrophobicity grade test, the aging grade of insulator samples was divided, and the mathematical statistics was used to calculate the aging grade division from the sample data, which provided a reference for the quantitative evaluation of the aging degree of the composite insulator.

500kV zinc oxide arrester is usually arranged outdoors. The surface of its porcelain sleeve will be contaminated by local environmental pollution and weather factors such as frost, rain and snow. The surface flashover problem caused by pollution is similar to that caused by insulator surface pollution. The difference is that there are three resistor columns connected in series inside the arrester. The influence of surface contamination on the voltage distribution of the internal resistor and the radial electric field between the resistor and the porcelain sleeve needs to be studied. In this paper, a two-dimensional axisymmetric simulation model of 500kV zinc oxide arrester when its surface is polluted was established. The electric field distribution of the porcelain sleeve is simulated when it is clean, uniform and partially dry. The voltage distribution of the resistor under different pollution conditions and the radial electric field between the resistor and the ceramic sleeve are compared and analyzed.

In this paper, the effect of SiO2 particles on electrical properties of superhydrophobic antiflash coatings was studied, which electrical properties include, the volume resistivity (ρv), the electrical strength (UB), relative permittivity (er), and the dielectric dissipation factor (tanδ). This kind of superhydrophobic coating uses modified SiO2 and TiO2 particles to construct micro-nano composite structures on the surface of FEVE fluorocarbon resin, and its surface has superhydrophobic characteristics. The results show that, with the addition of 5um SiO2 content, ρv of the coating showed a trend of first increasing and then decreasing. The amount of 20 nm SiO2 particles added has little effect on ρv. The content of 5um and 20 nm SiO2 has little influence on the UB of the coating. With the increase of 5um and 20 nm SiO2, er and the tangent of tanδ show an increasing trend. Compared with 5um SiO2, 20nm SiO2 has less influence on tanδ. The addition of 80nm SiO2 has obvious significantly adverse effects on the four electrical properties of the coating.

Infrared temperature measurement plays an important role in the live detection of UHV arrester with its advantages of high efficiency and accuracy. However, the surface temperature of arrester will be affected by wind speed, sunlight and other external factors, which brings certain difficulties to infrared temperature measurement and fault diagnosis. Based on the principle of finite element, this paper established a three-dimensional temperature field simulation model of UHV AC arrester coupled with thermoelectricity, so as to use the model to simulate and analyze the temperature distribution of arrester under the influence of different wind speed and sunlight. The results show that the increase of wind speed strengthens the air convection and heat dissipation, which makes the maximum surface temperature decrease and the temperature rise decrease due to the internal defect heating of the arrester; the surface temperature of the arrester increases with the increase of solar radiation intensity, and the temperature of the sunny side is higher than that of the back, but the change of temperature rise is not great. The conclusion can be used as a reference for infrared temperature measurement of arrester in nonideal environment.

Distributed generation (DG), battery storage (BS) and electric vehicles (EVs) in a microgrid constitute the combined power generation system (CPGS). A CPGS can be applied to achieve a reliable evaluation of a distribution network with microgrids. To model charging load and discharging capacity, respectively, the EVs in a CPGS can be divided into regular EVs and ruleless EVs, according to their driving behavior. Based on statistical data of gasoline-fueled vehicles and the probability distribution of charging start instant and charging time, a statistical model can be built to describe the charging load and discharging capacity of ruleless EVs. The charge and discharge curves of regular EVs can also be drawn on the basis of a daily dispatch table. The CPGS takes the charge and discharge curves of EVs, daily load and DG power generation into consideration to calculate its power supply time during islanding. Combined with fault duration, the power supply time during islanding will be used to analyze and determine the interruption times and interruption duration of loads in islands. Then the Sequential Monte Carlo method is applied to complete the reliability evaluation of the distribution system. The RBTS Bus 4 test system is utilized to illustrate the proposed technique. The effects on the system reliability of BS capacity and V2G technology, driving behavior, recharging mode and penetration of EVs are all investigated.

The majority of the distribution network is supplied by unilateral power and has a radial distribution, wind farms connected into grid will inevitably bring a certain extent on static voltage of the distributed grid. Furthermore, the randomness of wind farm output will cause the node voltage fluctuations. This paper firstly studies the random flow calculation method including wind power, and analyzes the probability distribution of the grid voltage when wind farms with different capacity accessing by combining the Newton-Raphson method with probability theory. Then establishes a computing model of penetration capacity of wind farms with the constrain of the static voltage stability range. For different values of confidence level α, the results of penetration capacity are different, then we can choose the value α flexibility according to the distribution network security requirements.

To ensure safety and stability of distribution network, the maximum allowable capacity of DG has a certain limit. The maximum allowable capacity can be defined penetration level. The paper first analyses the influence caused by DG on power flow, network loss, node voltage, power quality, current protection and anti-islanding, then introduces some typical evaluation methods for penetration level of distributed generation in distribution network, these methods and conclusions can provide some references for DG planning.

In this study, a novel intentional island model of a distribution system with distributed generations (DGs) is presented and the improved Dijkstra algorithm is used to solve this model. This paper abstracts the distribution network with DGs to the layered directed tree according to its radial structure and power restoration process. In consideration of grade, controllability, capacity, level and electrical betweenness of load, the model weights load and maximizes total load weight in the island. The proposed model considers power balance, node voltage, phase angle and transmission capability of the branch, and network connectivity to meet practical engineering requirements. The improved Dijkstra algorithm formulates a search rule to select the load that can be divided into an island in descending order of the shortest path between the load node and DG node. An optimal island partition scheme is achieved through three stages: origin island, baby island and mature island. Meanwhile, scheme adjustment and constraint checking are used alternately to balance objective functions and constraints. The improved IEEE 43-bus distribution network is applied to verify the validity of the algorithm. A comparison of two island methods shows that the proposed algorithm can generate a reasonable scheme for island partitioning.