P. Sarma Maruvada

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

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

The corona (in particular RI and AN) performance of two basic configurations of Hydro- Québecs 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.

Corona Studies for Biploar HVDC Transmission at Voltages Between ±600 kV AND ±1200 kV PART 2: Special Biploar Line, Bipolar Cage and Bus Studies

Some special aspects of the corona performance of bipolar HVDC transmission lines, as well as basic results on the corona performance-of bipolar bus configurations, are presented in this paper. In the special bipolar line study, the influence of the line parameters, namely the pole spacing and the conductor height, on the corona performance of bipolar lines is investigated. Results are also presented on the feasibility of using test cages for bipolar corona studies of conductor bundles. The bipolar bus study presents the results of corona performance characteristics of bus configurations required for bipolar HVDC stations in the voltage range of ±600 kV to ±1200 kV.

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

Human perception of electric fields and ion currents associated with high-voltage DC transmission lines

The objective of this study was to assess the ability of humans to detect the presence of DC electric field and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines.

Radio Noise Meter Response to Random Pulses by Computer Simulation

The radio interference from high voltage transmission lines is generally measured using either the CISPR or the ANSI type of instrument to give the quasipeak value and in some cases also the peak and average values, of the interference. However, because of the random and uncorrelated nature of corona generation on the transmission lines, the analysis of radio interference propagation can be made only in terms of rms quantities. In order to resolve this apparent inconsistency between the measurement and analysis of radio interference, the response of the conventional radio noise meters to random pulses is investigated using digital computer simulation. Some results are verified using a hybrid computer simulation, which represents more closely the detector output circuit of a radio noise meter. The results show that as the degree of randomness, both in amplitudes and separation intervals, of the pulses increases, the quasi-peak value becomes roughly proportional to the rms value. It is also shown that it is possible to predict, even with greater accuracy, the rms response of the radio noise meter from the measured quasi-peak and average responses.

Influence of Ambient Electric Field on the Corona Performance of HVdc Transmission Lines

Ambient electric fields produced by atmospheric electricity at the ground surface modify the electric-field distribution between the conductors and ground plane of HVdc transmission lines. Depending on their magnitude and direction, ambient electric fields may therefore contribute to variations in the overall corona performance of dc lines. A computational technique is developed in this paper to simulate ambient electric fields in the vicinity of HVdc transmission lines and evaluate their influence on the electric-field distributions on the surfaces of conductors and ground plane and determine the resulting pattern of flux lines. The computational technique is then applied to practical HVdc transmission-line configurations to determine the influence of ambient electric fields on radio interference (RI), audible noise (AN) performance, and onground-level electric-field and ion current distributions. The computational results are compared with some experimental data obtained on a dc test line and an operating dc transmission line.

Evaluation of the effectiveness of shielding and filtering of HVDC converter stations

The electromagnetic interference (EMI) generated by the periodic turn-on and turn-off of the valves is an important consideration in the design of HVDC converter stations. Remedial measures such as shielding the valve hall and filtering have been used in order to reduce the interference levels to acceptable values. The application of recently-developed Numerical Electromagnetic Code (NEC) to the problem of EMI from HVDC converter stations is investigated in this paper, with particular emphasis on evaluating the effectiveness of valve hall shielding and filtering.

A statistical model to evaluate the influence of proximity to transmission lines on residential magnetic fields

A statistical model, based on Monte Carlo simulation, is proposed in this paper for evaluating the influence of the proximity of transmission lines on the magnetic field intensities and exposures in the residential environment. The proposed model is validated by comparing the results of calculation using the model with experimental data obtained in a related study.

Analysis of Radio Interference from Short Multiconductor Lines Part 1: Theoretical Analysis

Radio Interference (RI) measurements made on short single-conductor or multiconductor test lines are generally used to predict the RI performance of the corresponding long lines. A rigorous analysis is presented in this paper of RI propagation on short lines including the influence of different impedance terminations at the ends of the line. The method consists essentially of the modal propagation analysis which takes into account the effect of line terminations. It is shown that the short-line analysis developed in the paper can also be extended to the case of long lines, which automatically takes into account the correct method of adding the modal components. Analytical results obtained by applying this analysis to practical line configurations, and some comparisons with experimental results, are presented in a companion paper.