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Power-grid faults pose a great threat to the economy and to social stability. In this paper, the detrended fluctuation analysis method is used to investigate the scaling properties of power grid faults and the correlation between faults and meteorological factors that are closely related to power grid faults. Multifractal detrended fluctuation analysis showed that the fault time series were multifractal. Further investigations revealed the origins of multifractality in power-grid fault time series, and the results showed that the temporal correlations in the data represent the distribution of the returns, which are a significant source of multifractal scaling. Then, cross correlations between the fault and the four meteorological factors were investigated using the detrended cross-correlation analysis method. The results showed that maximum wind speed has a considerable impact on the number of transmission system line faults per day, whereas daily precipitation, daily mean air temperature, and maximum wind speed have a considerable impact on the number of distribution system line faults per day.

Conductor galloping is a common phenomenon during the operation of the transmission line, which can easily result in electrical accidents such as flashover and tripping caused by insulation breakdown of the inter-phase spacers. In this paper, a multi-span 4DOF (4 degree-of-freedom) dynamic model for the conductor-insulator is established, and the aerodynamic parameters of the 500kV crescent-shaped iced quad bundle conductor are calculated by CFD, and then the research on conductor galloping and insulation is done. Based on the explicit central difference integral algorithm, the galloping situation under different wind velocities, ice thicknesses, and spans are analyzed discussed. The results indicate that, between the minimum and maximum wind velocity that leads to gallop, the amplitude increases almost linearly corresponding to the wind velocity, which is a challenge to line insulation. Besides, the increasing of ice thickness makes the conductor easier to gallop and may destroy the outer insulation of line. However, too large thickness may be adverse and break the galloping. Furthermore, the conductor span has little effect on the minimum phase spacing. The conclusions are important for the development of anti-galloping technology and the insulation design of the transmission lines.

Serious icing disasters threaten the safe running of power system. Overhead ground wires are difficult to de-ice with common heat de-icing methods in some special areas. A mobile DC de-icer for the overhead ground wire is developed in this paper to realize flexible de-icing. A diesel generator provides the 50 Hz three-phase power supply. A rectifier transformer is used to step up the voltage and a rectifier is used to convert AC to DC. The 12-pulse rectification mode is adopted to reduce the current harmonics of the rectifier and to decrease the ripple of the DC output. Onsite experiment of the mobile DC de-icer for the overhead ground wire is performed on a GJ-70 typed overhead ground wire with the length of 4847 meters. A temperature rise of 7.0°C is achieved in 36 minutes under the DC de-icing voltage of 2700 V and current of 100 A. The result shows that the mobile DC de-icer for overhead ground wire can operate reliably and can meet the demand of flexible de-icing.

The laws of cloud-to-ground flash activities are the important fundamental data of lightning protection engineering, which can provide reference for the selection of transmission line route and for the effectual lightning protection measures. Based on the lighting data of the lightning location system (LLS) in Hunan Province from 2002 to 2010, the probability distribution of lightning current magnitude is analysed in this paper. The temporal and spatial distribution of lightning activities in Hunan Province is acquired by counting the cloud-to-ground flashes in different time and different regions with geographic information system (GIS) and grid method. Statistical results show that there exist obvious differences of cloud-to-ground flashes in different time and different regions for the lightning activities in Hunan Province. The lightning activities in some regions are intensive and the cloud-to-ground flash density reached 6.9 flashes per square kilometer per year. The probability distribution of lightning current magnitude in Hunan Province accords with a lognormal distribution approximatively.

Grounding grids play an important role in guarantee the safe operation when the station has encountered the short circuit or be attacked by lighting. Grounding grids must reconstruct when grounding resistance does not meet the regulation requirements. Using ion earthing electrode to reconstruct the grounding grid will cost less and have better effect. However, this way may increase the corrosion of grounding grid. In this paper, “ Ion earthing electrode with anti-corrosion” grounding grid reconstruction technique is presented. This technique not only exerts the advantages of ion earthing electrode but also prevents grounding grid from corrosion. It was applied in 500kV Aijiachong power station, 220kV Nanzhutang power station, and so on. Grounding resistances of these power stations reached prospective effect after reconstruction.

Lightning activity is a common phenomenon, which always is a great thread to safety of power grid, and it's the important reason for the accident of power grid and non-planned stopped operation. Through make analysis on the statistics data of lightning activities in Hunan area, we summarize that the historic discipline of lightning activity, and propose six typical weather situations which is prone to appear lightning weather. And this proposed method has been taken to make lightning forecast. Through giving lightning forewarning information, it can offer great guidance to the anti-lightning work of transmission line.

This article introduced the design background of online monitoring system of transmission line icing, and the reason of it being struck by lightning, which is easy to be received in the thunder and lightning environment. The article also proposed a method about the monitoring system of transmission line icing protecting against lightning, and analysis devices of protecting against lightning, over current and over voltage. It provided the design reference of online monitoring system of protection against lightning on the open country transmission line and the towers.

Serious lightning or icing often causes flashover on the insulators and probably results in a tripping accident. A novel composite insulator with lightning protection and icing flashover prevention is presented. The novel composite insulator with the rated voltage of 220 kV, specified mechanical load of 100 kN for the whole insulator and the nominal discharge current of 10 kA for the lightning protection part is designed and is manufactured. Basic performance, electrical performance, and mechanical performance are tested for the novel composite insulator. The experimental results show that the novel product meets the requirements of both standards of the common composite insulator and the common line metal oxide surge arrester and achieves the application conditions.

This article introduces the project's background of the transmission line icing thickness regelation. Through analyzing characteristics of transmission line scene pictures, there are two main technical difficulties. The lower edge of the wire is in shadow and the complex background of the wire, respectively, which are encountered in the scene image pre-processing. This article proposes using a common method, such as threshold segmentation for grayscale images, and using a gradient operator for the edge extraction on the transmission line icing image. We use a line-search algorithm to calculate the value of the thickness of transmission line ice covering. We use several tests applied to many images on different complex backgrounds to prove the algorithm is effective.

The zero resistance insulator greatly threats the safe and steady operation of the power system. A new method of detecting the zero resistance insulator on-line based on the infrared thermal image is presented. The recognition algorithm for zero resistance insulator with image processing is designed. The soft thresholding de-noising method is designed and Bayesian estimation is applied in the de-noising of infrared thermal images. The improved bi-threshold OTSU segmenting method is applied to wipe out the disturbed objects and keep only the plate area of insulators. Two-factor analysis of variance is used to assess the features of the infrared thermal images. Additional momentum and self-adaptive gradient descent algorithm are applied to improve back-propagation (BP) neural network in this research. Testing results show that these methods can achieve good effect.

Limiting the short-circuit current is of great significance to keep the safe and steady running of the power system. A novel fault current limiter (FCL) is presented. A high speed switch is used to rapidly break the short-circuit current. A triggered vacuum switch (TVS) is used to discharge a precharged pulse capacitor so as to quench the arc in the high speed switch quickly and to realize the active transfer of the short-circuit current. A resistor is used as the current limiting component. The parameters of a FCL of 10 kV voltage level are designed. Simulations of the FCL in an oscillating circuit are performed by means of the ATP software. Experiments of a FCL sample device are also carried out in the oscillating circuit. The experimental results are in agreement with the simulation results. The current transfer characteristics and the current limiting effect are testified.