Electromagnetic effects - From cell biology to medicine.

Epoxy-based model insulators were manufactured and fluorinated under a F2/N2 mixture (12.5% F2) at 50 °C and 0.1 MPa for 15 min and 60 min. Surface charge accumulation and decay behavior were studied with and without dc voltage application. The effect of direct fluorination on surface charge migration as well as on flashover voltage was verified. The obtained results show that the charge decay of epoxy-based insulators is a slow process, but the decay rate increases when an outer dc electric field is applied. The surface charge distribution is changed when a streamer is triggered on the insulator surface. The existence of heteropolarity surface charges can decrease the dc surface flashover voltage to some extent, while the surface flashover voltage is almost unchanged when charges of the same polarity accumulate on the insulator surface. The short time fluorinated insulator can modify the surface resistivity, and the rate of surface charge dissipation is greatly increased under a dc electric field.

https://iopscience.iop.org/article/10.1088/1361-6463/aa5207/pdf

Surface charge migration and dc surface flashover of surface-modified epoxy-based insulators

The electric field and ion current environment under HVdc transmission lines is an important design consideration. The flux tracing method (FTM) for calculating the ground-level electric field and ion current density distributions is reviewed and the possible errors caused by the use of Deutsch's assumption in the FTM are estimated. Experimental data obtained under one dc test line and three operating dc transmission lines are compared with calculations made with the FTM. The results show that the most important factor influencing the electric field and ion current distributions is the corona onset gradient of the conductors, or indirectly, the conductor surface roughness factor. The results also show that for practical dc transmission-line configurations, any errors caused by Deutsch's assumption are quite small compared with the observed variations in experimental data.

Electric Field and Ion Current Environment of HVdc Transmission Lines: Comparison of Calculations and Measurements

A micro-aperture electrostatic field mill based on MEMS technology

This paper describes Bonneville Power Administration's basic philosophy for predicting audible noise from ac and dc high voltage transmission lines. General formulas for predicting the A-weighted audible noise during rain for ac lines and during fair weather for dc lines which were developed from data from full-scale lines are presented. From this basic calculation, audible noise cumulative distributions, frequency spectrums, and lateral profiles can be estimated

Formulas for Predicting Audible Noise from Overhead High Voltage AC and DC Lines

The electric environment under HVDC transmission lines is characterized by electric field, current density and space charge density. The measurement of electric field at and above ground level is described in this paper. A field-mill instrument has been developed for ground-level measurements and has been used extensively under the bipolar dc test line at IREQ. The same principle was applied to develop a cylindrical field probe for measurements above ground. Details of the operating principle, design and construction of the two instruments are given in this paper together with an account of the calibration procedure and operating experience.

Development of Field-Mill Instruments for Ground-Level and Above-Ground Electric Field Measurement Under HVDC Transmission Lines

As part of a general study on the possible use of UHV transmission lines in the range of 1200 kV for the James Bay Project, the corona performance of four conductor bundles -6 ×1. 823", 6 ×1. 998", 8 ×1. 63 " and 8 ×1.823"-has been studied in outdoor test cages under conditions of heavy artificial rain and fair weather. The radio interference, audible noise and corona losses of the four conductor bundles have been measured in the test cages, and the corresponding long line levels have been evaluated. The results show that of the four bundles tested the 8 ×1.63" conductor bundle gives the best corona performance. However, ice loading conditions may dictate the use of a six conductor bundle, in which case the 6 ×1.823" conductor bundle seems to give a marginally acceptable corona performance.

A Comparative Study of the Corona Performance of Conductor Bundles for 1200 KV Transmission Lines

Transverse wind has a large influence on the electric field and ion current environment of HVDC transmission lines. The flux tracing method (FTM) is modified by including wind velocity in the defining equations of corona-generated monopolar DC space-charge modified fields. The modified method, called FTM-Wind, is derived by making appropriate assumptions and identifying wind-modified pattern of flux lines. Computations are made using FTM-Wind for hypothetical monopolar and bipolar DC transmission-line configurations to obtain a physical understanding of the influence of wind in changing the pattern of flux lines and, as a consequence, changing the ion current distributions on the ground plane. The FTM-Wind is also applied to study the influence of wind on the ion current profiles of a ±900-kV bipolar dc test line for which long-term measurement data are available. Calculations show reasonable agreement with measured ion current profiles grouped according to ranges of wind velocity.

Influence of Wind on the Electric Field and Ion Current Environment of HVDC Transmission Lines

The corona (in particular RI and AN) performance of two basic configurations of Hydro- Quebec's 735-kV transmission lines was recorded over a two-year period between 1976 and 1978. Statistical analysis of the data shows that both the RI and AN performances of the lines compare well with previously recorded data and are well within accepted norms.

A Study of the Corona Performance of Hydro-Qu??bec's 735-kV Lines

This paper reports on the use of test cages for obtaining the corona performance characteristics of conductor bundles under monopolar and bipolar dc excitation. A large nuimber of conductor bundles were tested under positive and negative monopolar dc as well as bipolar dc conditions in the outdoor test cages of IREQ. Radio interference (RI), audible noise (AN) and corona loss (CL) were investigated under fair weather and artificial rain. Empirical equations were derived for these three parameters: RI, AN and CL, as functions of the bundle geometry and conductor surface voltage gradient. Based on a comparison between cage and line test results, conclusions are drawn on the practical validity of cage tests for dc corona.

P. Sarma Maruvada

Papers

Development of Field-Mill Instruments for Ground-Level and Above-Ground Electric Field Measurement Under HVDC Transmission Lines

A Comparative Study of the Corona Performance of Conductor Bundles for 1200 KV Transmission Lines

Influence of Wind on the Electric Field and Ion Current Environment of HVDC Transmission Lines

A Study of the Corona Performance of Hydro-Qu??bec's 735-kV Lines

HVDC Monopolar and Bipolar Cage Studies on the Corona Performance of Conductor Bundles