Ye Qizheng

A displaced dipole model for spheres in a non-uniform field

Abstract In this paper, a displaced dipole model for spheres in a non-uniform field is proposed. The displaced dipole moment and displacement can be approximately obtained from the external field values at the two poles of the sphere. The analytical expressions of the electric field are derived for a sphere in the non-uniform electric field. As the model does not have to assume the external field to be uniform in the vicinity of the spheres, it differs from the dipole-at-the-center approximation. In addition, it is simpler than the multipoles technique. Another result obtained is that the displaced dipole of two closely spaced spheres approaches the edge of the sphere when ei/ee⩾4 and the displaced dipole model becomes ineffective.

Abnormal breakdown characteristic in a two-phase mixture

A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsends theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, UTPM, increases gradually with an increase in the macroparticle number density (m). The voltage UTPM is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage UTPM increases gradually at low m values and decreases gradually at high m values. The voltage UTPM at pd = 200?cm?Torr is lower than that at pd = 760?cm?Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPMs Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field.

Influence of the Transverse Field Component on the Edge Effect in a Short-Gap Discharge

In a general plane-parallel electrode system, the edge of the electrode will undermine the uniformity of the dielectric barrier discharge (DBD) because of the influence of the distorted electrical field. In this paper, the influence of the non-uniform electrical field on the edge effect of DBDs in a short-gap is investigated. We present some of the experimental results of DBDs produced by three kinds of convex-spherical electrodes. The results show that there is a dark area (the homogeneous discharge) in the central region of the electrode and a bright halo (the filamentary discharge) in the outer peripheral region, and the radius of the dark region is determined by the electrode geometry. The calculated results of the transverse (radial) field component distribution on the surface of the electrodes show that the edge effect does not come from the electrode edge, but the transverse field. The discharge has enough space to be fully developed and then format the filamentary discharge in the outer peripheral region because the streamer of the filamentary discharge is driven to move along the direction of the longer path by the transverse field. Thus, the homogeneous discharge (the Townsend DBD or a glow DBD) could not be produced in this area.

Studying on dimensional standardization of UHF partial discharge detection system

In the ultra-high-frequency (UHF) partial discharge (PD) detection system, many physical quantities, such as voltage, charge, power and their normalization, were used to describe the UHF PD signal. The standardization of the dimensional has not been investigated thoroughly. Based on the PD forming mechanisms, the pulse transient electric field was presented as a main physical quantity in this paper. The minimum pulse transient electric field, which could be differentiated by the UHF PD detection system, was adopted as the sensitivity of detection system. The sensitivities of four detection systems were measured by GTEM platform, and comparison tests for Spike discharge in GIS were made. The experimental results were in accordance with the sensitivity of detection system.

The Numerical Solution of the Nonlinear Poisson-Boltzmann Equation Under the Anisotropic Boundary Condition for Colloidal Plasmas

Based on the model of the Wigner–Seitz cell, the surface potential of the spherical macroparticle (radius a) expands in terms of the monopole (q). A dipole (p) model is assumed for an anisotropic boundary condition of the nonlinear Poisson–Boltzmann equation. Using the finite element method implemented by the FlexPDE software, the potential distribution around the macroparticle is obtained for different ratios p/qa. The calculated results for the potential show that there is an attractive region in the vicinity of the macroparticle when |p/qa|>1.1, and noticeably there is a potential well behind the macroparticle when |p/qa| = 1.1, i.e., there exists both an attractive region and a repulsive region simultaneously. This means that the attractive interaction between macroparticles may arise from the anisotropic distribution of the surrounding plasmas, which well explains some experimental observations.

The cell dipole model in the dusty plasma

Based on a new physical concept, the momentneutrality of dusty plasmas (Ye Qizheng et al., J.Phys.D: Appl. Phys., 40), a particle in a spherical Wigner-Seitz cell has been replaced by a dipole p0 besides a charge q, for describing the actual potential distribution around the particle. By introducing the “apparent” dipole p in this paper, the surface potential of the particle caused by p0 and the sheath dipole pz can be decided by p. If we assume that the dusty plasma has roughly equal moments of particle dipoles (+) and sheath dipoles (−), i.e. “momentneutrality”, the relationship between the actual moment and the “apparent” moment can be acquired, and the potential around the particle in a WS cell can be calculated by self-consistent.

Electrical field adjustment for 500 kV optical metering unit

This work discusses our ongoing development of an AC 500 kV optical metering unit for use in a power system. The high voltage part of this unit is designed in a large size related to practical use. We review our test arrangement and present the experiment data demonstrating the results of different effects such as the vertical position and the height of the upper flange on the magnitude, sensitivity and linearity of the measurements of the optical voltage sensor. The results will be help of adjusting the electrical field in a designation of 500 kV optical metering unit for practical use.