Wenjun Zhou

Experimental Investigations on Applicable Criterion for AC Corona Discharge Evolvement of Rod-plane Gap Based on UV Digital Image Processing

A measuring and analytical platform of corona discharge combining CoroCAM IV+ with the virtual instrument programming environment - Labview 8.0 - was designed. Selecting the proper algorithm and flowchart of the digital image processing, the Area Percentage of the UV image within the discharge zone was defined as the characterizing parameter of quantifying the intensity of corona discharge with processing the UV video of corona discharge recorded real time. Under the approximate standard atmospheric ambient, the study on corona discharge under the power frequency voltage of the rod-plane gap based on the UV digital image processing is carried out. The results illuminate that the flowchart of the digital image processing mentioned in the paper could reproduce the images observed by the UV imaging camera so as to ensure the validity of the quantifying parameter of corona discharge; the characterizing parameter could reflect the corona discharge development stages definitely; the regularity of the UV imaging of corona discharge attenuating with the observation distance is obtained; Standard Conversion Method - the applicable criterion of the corona discharge UV imaging detection is proposed.

Simulation research on impulse characteristics of horizontal grounding conductor

Impulse grounding resistance is closely related to lightning withstand level of transmission line towers, so study on the impulse characteristics of tower grounding conductors is of great significance. This paper, based on circuit theory, uses electromagnetic transient analysis software ATPDraw to simulate impulse characteristics. Control function of ATPDraw can simulate inductance effect and spark discharge effect well when lightning current flows through the grounding conductor, improving the existing simulation model. In this paper, a single extended model is established and the characteristics that inductance effect varies with the length and spark discharge with the current amplitude are researched. Simulation results are compared with laboratory test conclusion and they are identical which testify that the model and method is reliable.

Research on the Electromechanical Characteristics of the Lightning Rod Which Is Used for Taking Precautions Against Transmission Line Shielding Failure

On account of the shielding failure in extra high voltage network of 220 kV or above, we open out lightning rod (XBL-II) which was used for taking precautions against transmission line shielding failure. According to proportional model experiment, it can prevent shielding failure of line effectively. That lightning rod adopts needle bar symmetrical structure with its own counterweight, which can bring it back to balance automatically. Tiny air interstices are kept in needle in series, with insulating coating at the needlepoint. Based on theoretical analysis, these designs can strengthen the ability of leading thunder of lightning rod. Through the electromechanical characteristics test for lightning rod (XBL-II) which is used for taking precautions against transmission line shielding failure, we study the characteristics of lightning rod (XBL-II), such as the ability of leading thunder, the test of big electric current impulse withstand, the test of gentle breeze vibration and low frequency large amplitude and the test of power performance.

Application of 10kV post-arrester in protection from induced-lightning in distribution network

The tolerance level of the induced-lightning and the trip-out rate of applying different lightning protection measures on 10kV lines are gotten by emulating in ATPDraw and calculating. Though researching the destiny of the installation of post-arrester, the conclusion is reached that its no obvious effect on reducing lightning trip-out rate to place post-arresters at intervals. Only if arresters are installed continuously, the lightning trip-out rate will be reduced obviously. But it is not economical to install arresters continuously on the whole lines. So more-thunderstorm regions should be selected out to install arresters continuously.

A new portable test system for surge protective device (SPD)

In order to solve the problem of field testing the surge protective device (SPD) of the electrical and electronic equipments in low-voltage (LV) power system, this paper proposed a portable field test system for SPD. The tester can output waveform of 1.2/50µs∼8/20µs combination wave and produce DC high voltage, which can do impulse test and DC detect on SPD. This paper mainly talked about how to design this tester for portable, and illustrated that the tester can conveniently and effectively tell the performance of SPD in field use, so as to ensure the reliability of SPD.

Research on Lightning Overvoltage and Comprehensive Lightning Proof Measures of 10kV Overhead Insulated Distribution Lines

By calculating the amplitudes of the lightning induced overvoltage and induced current of the overhead insulated distribution lines, this paper studies the damage to the lines caused by induced overvoltage and induced current. According to the calculations, the value of induced overvoltage can be 400 kV and more, greater than overhead insulated lines and obtains the optimal parameters to prevent lightning strike break by adopting insulating cross arms. In the meantime, combining the theoretical analysis, it is known that adopting 400 mm insulating cross arms can prevent lightning break. As a result, depending on different operations and considering comprehensively, this paper puts forward measures as insulating cross arms, the stab type arc protection hardware, lightning proof post insulators and lightning arresters to prevent lightning break.

Research on Quantification of AC Corona Discharge Intensity of Rod-Plane Gap Based on UV Digital Image Processing

A measuring and analytical platform of corona discharge combining CoroCAM -V+ with the virtual instrument programming environment - Labview 8.0 - was designed. Selecting the proper algorithm and flowchart of the digital image processing, the area percentage of the UV image within the discharge zone was defined as the characterizing parameter of quantifying the intensity of corona discharge with processing the UV video of corona discharge recorded real time. Under the approximate standard atmospheric ambient, the study on corona discharge under the power frequency voltage of the rod-plane gap based on the UV digital image processing is carried out. The results illuminate that the flowchart of the digital image processing mentioned in the paper could reproduce the images observed by the UV imaging camera so as to ensure the validity of the quantifying parameter of corona discharge; the characterizing parameter could reflect the corona discharge development stages definitely; the regularity of the UV imaging of corona discharge attenuating with the observation distance is obtained; standard conversion method - the applicable criterion of the corona discharge UV imaging detection is proposed.

Research on Lightning Attraction Ability of Lightning Rod with Insulation Covering and Series Air Interstice

Analysis of electric field can be realized through observing the charge distribution around the tip of a lightning rod with insulation covering and series air interstice by means of high speed camera. From the test phenomenon, it can be achieved that, under the same voltage, compared to a common lightning rod, charge density in the lightning leader channel of a lightning rod with insulation covering and series air interstice is much larger, the thermal ionization is more violent, the leader channel is explicitly longer and the forward electric field density is obviously strengthened. The test results indicate that the lightning attraction ability of a lightning rod with insulation covering and series air interstice is evidently better than a common rod.