Tadashi Kawamoto

Calculation of ION Flow Fields of HVDC Transmission Lines By the Finite Element Method

The paper describes a new method for calculating electric field and ion current caused by overhead DC transmission lines without using the commonly used approximation, Deutschs assumption. Unknown space functions, i.e. potential, positive and negative ion densities, are iteratively calculated from the coupled differential equations by the finite element method (FEM). The program is generally applicable to all monopolar and bipolar cases including grounded wires and wind. Emphasis is placed on numerical stability and reduced human task in the FEM computation.

Principle of surface charge measurement for thick insulating specimens

We discuss the method for measuring surface charge density accumulated on the surface of a solid dielectric (insulating specimen) such as a supporting spacer in gas and vacuum insulated equipment. For such thick specimens, the probe response does not correspond to the charge density directly below the probe, so the measurement necessitates multipoint data together with the aid of numerical field calculations. The probe gives either induced charge or floating potential in response to the surface charge. We compare various previously proposed techniques and give a reasonable procedure for analyzing the data.

Charge Simulation Method with Complex Fictitious Charges for Calculating Capacitive-Resistive Fields

This paper describes a numerical method for calculating electric fields very accurately in configurations including voluime resistance or surface resistance. The principle of the method is to incorporate the field effect of the true charge caused by conductivity in that of complex fictitious charges by the charge simulation method (CSM). CSM with complex charges for computing multi-phase AC fields is also described with a calculated example. Results are given for comparison with analytical expressions and for a disc-type gas insulation spacer having either volume resistance or surface resistance.

Mechanism and effect of DC charge accumulation on SF/sub 6/ gas insulated spacers

Mechanism and effect of DC charge accumulation on the surface of a solid insulating support (spacer) have been studied in compressed SF/sub 6/ gas using various cylindrical model spacers. The distribution of surface charged is closely related to the normal component (gas side) E/sub n/ of electric field on the spacer surface. The ,maximum charge density can be estimated from the condition of E/sub n/=0. When voltage is applied in a polarity opposite to prestressed DC, surface charge increases the maximum field strength in the arrangement, resulting in the reduction of the insulating ability. It is possible to estimate the lowest flashover voltage due to surface charges only from numerical fields calculations. An anticharging spacer shaped along electric lines of force is proposed and studied. >

Field Intensification Near Various Points of Contact with a Zero Contact Angle Between a Solid Dielectric and an Electrode

This paper describes the field intensification at the contact point in various arrangements where a rounded electrode contacts a solid dielectric at a zero contact angle. Three basic and two practical arrangements have been numerically analyzed for a variety of parameters.

Requirements for power line magnetic field mitigation using a passive loop conductor

Magnetic field mitigation for overhead power lines using a passive loop conductor was studied. The aim of this study is to clarify the requirements for effective mitigation not in a specific region such as at the edge of the ROW (right of way) but everywhere around the conductors. For this purpose, the concept of current dipole moment was introduced and applied to the problem. First to determine the validity of the derived formula which estimates the induced current to the passive loop, a miniature transmission line model experiment was performed. Then, the mitigation effectiveness of the actual dimensions of several kinds of overhead transmission line arrangements were estimated by the calculation. The application of a current dipole moment, was sufficient for explaining the differences in the mitigation effectiveness depending on the conductor arrangement and for clarifying the requirements for effective mitigation.

Equivalent dipole moment method to characterize magnetic fields generated by electric appliances: extension to intermediate frequencies of up to 100 kHz

A previously proposed simple method to characterize magnetic fields near electric appliances was extended to intermediate frequencies of up to 100 kHz. The method consists of identification of the magnetic dipole moment that is equivalent to a magnetic field source of an electric appliance and simple estimation of the magnetic field distribution around the appliance. In addition, frequency characteristics of the magnetic field were taken into account by considering the harmonic components in the magnetic-field waveform for both power frequency and intermediate frequency ranges. For the application of the method, a wide-frequency range (from power frequency to 100 kHz) magnetic-field measuring instrument was developed and applied to appliances that generate intermediate frequency magnetic fields, i.e., an induction heating cooker, a TV set, and a metal detector. The results revealed that the method is adequate to quantify the magnetic field near the electric appliances at frequencies of up to 100 kHz.

Simple estimation of equivalent magnetic dipole moment to characterize ELF magnetic fields generated by electric appliances incorporating harmonics

A simple method of quantifying the ELF (extremely low frequency) magnetic field distribution around electric appliances, which takes the harmonics into account, is newly proposed. The proposed method involves: (1) a simple estimation of the position of an equivalent magnetic dipole moment inside an appliance, using two magnetic field meters; (2) identification of the amplitude of the dipole moment magnetic-field measurements at certain points; and (3) calculation of the magnetic field distribution around the appliance using the estimated dipole moment. In this method, the dipole moment vector is assumed to be a similar value by allowing an uncertainty of 6 dB in the estimated magnetic field, which enables easy estimation of the dipole moment. In addition, the frequency characteristics of the magnetic field are taken into account by considering the harmonic components in the magnetic field waveform. The proposed method was applied to 13 types of appliances, and their equivalent magnetic dipole moments and harmonic components were determined. The results revealed that the proposed method is applicable to many electric appliances. The conditions required for the adoption of the method were also clarified.

Analysis Of Calibration Arrangements For AC Field Strength Meters

This paper presents numerical calculations for two kinds of arrangements used for calibration of AC field strength meters: a vertically symmetrical parallel-plate and a non-symmetrical plate-to-plane arrangement. Factors affecting the field distribution were analyzed with high accuracy, such as ratio of the electrode separation to the plate dimension, effect of an introduced meter and a grounded wall. The non-symmetrical arrangement is easier to use, but the symmetrical arrangement is more immune to the perturbing effects. Some of calculations were compared with the analytical approximation or with the experiment.

Effect of Conduction on Field Behavior Near Singular Points in Composite Medium Arrangements

The electric field configuration has been analyzed numerically by the charge simulation method near a contact point where two media having surface or volume conductivity meet an electrode. Surface conduction with uniform surface resistivity moderates the field singularity, resulting in a uniform field throughout both media for very low resistivity. On the other hand, volume conduction magnifies the field singularity if only one medium has conductivity. For these capacitive-resistive fields, it appears impossible to derive a simple analytical expression of field strength such as can be derived for purely capacitive cases.