Positive Corona Charging Research Articles

Surface charge distribution analysis of polymeric insulator under AC and DC voltage based on numerical and experimental tests

The objective of the present study is to investigate the surface charge measurement on the surface of polymeric insulator under AC and DC voltages experimentally. According to the test results, increasing the voltage amplitudes led to an increase of the surface charge density, the voltage application duration was also extended. During the tests, it was observed that as the corona voltage and the charging time for both polarities rise, the amount of charges increases linearly. The results show that more surface charge was deposited by negative corona charging when compared with positive corona charging. Also in this paper, the effect of the corona variations on the amount of surface charge have been investigated. For this purpose, relationship between amount of surface charges and number of photons have been carried out using corona camera. Moreover, attempt was made to investigate the effects of surface charges on potential and electric field distribution along polymeric insulator under AC and DC voltages using computer simulations based on finite element method (FEM). The present paper was conducted to study the effects of magnitude, polarity, and location of surface charges on surface potential distribution along the insulator.

Surface charges on silicon rubber (SiR) insulator and their effect on potential and electric field distribution

This paper presents experimental results of the surface charges and charge decay measurement on the surface of polymeric insulator. In this research, the effect of surface charges on electric field and potential distribution has been investigated. Therefore, using measured electric charge and charge decay, the electric field and surface potential on insulator are studied by computer simulations. The accumulation of electric charge under DC electric field makes a significant difference compared to AC electric field, and this increases the rate of electrical failure and corrosion in HVDC insulators. So, a thorough understanding of the surface charge effect on insulation performance is necessary under various stresses. The experimental results revealed that the amount of charges increases linearly with the rising corona voltage and the charging time for both polarities. It was also observed that the amount of surface charges deposited by positive corona charging is less than negative corona charging. The simulation results illustrate that surface charges are important in potential and electric field variations.

Identification of electron and hole trap based on isothermal surface potential decay model

For identifying electron and hole traps in polymeric materials, we combine the isothermal relaxation current theory and surface potential decay together and present a model called isothermal surface potential decay (ISPD). A non-contact measurement setup is specially designed, which features that energy distribution of electron or hole-type traps can be discriminated with negative or positive corona charging, respectively. By measuring the ISPD characteristics of low-density polyethylene and polypropylene films, their trap distributions are obtained, revealing the different semi-crystalline morphology of these two materials. The results we obtained may imply the essentially distinct nature of electron/hole traps: inter-chain for electron-type traps and intra-chain for hole-type traps, which is in agreement with other researchers' molecular modeling results.

The Effect of Shield Design on Positive Corona Charging Currents

The variables and parameters of corona device design for positive dc corona are discussed as they affect uniformity and magnitude of plate current as the shield angle surrounding the wire is changed. Also presented are the effects of using either grounded conducting or insulating shields on the magnitude of positive dc plate current.

Electrophotographic Properties of the Plate with a Polyvinylcarbazole Overlayer and a CdS-Resin Layer

The electrophotographic plate having a two-layer structure made up of a CdS-resin layer and a PVK overlayer is proposed. The effects of either dark resistivity or photo-sensitivity of the CdS-resin layer on factors which decisively affect electrophotographic characteristics such as the surface potential, the spectral response and the contrast voltage: are investigated. In case of negative corona charging, the external quantum efficiency attains a maximum value of 20% at a resistivity of 4×1013 Ωcm, while it attains a maximum value of 7.5% at a resistivity of 2×1014 Ωcm in the case of positive corona charging. The high efficiency for positive corona charging may be due to the use of CdS powder doped with Li and Cu.