Hongxian Zhang

An image recognition algorithm based on thickness of ice cover of transmission line

This article introduces the projects 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.

Self-Organized Criticality in Wildfire Time Series from China

AbstractTime-series data from the 2003 to 2013 actual wildfire records were analyzed. The evidence of self-organization criticality (SOC) for wildfire time series in three areas (Guizhou Province, ...

Study and experiment of mobile DC de-icer for overhead ground wire

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.

Manufacture and experiment of a novel composite insulator

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.

Protection against lightning on monitoring system of transmission line icing

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.

Forecast method of lightning activity based on the weather conditions

Lightning activity is a common phenomenon, which always is a great thread to safety of power grid, and its 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.

Application of ion earthing electrode and anti-corrosion synthetical reconstruction technique in reconstruction of grounding grids

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.