K. D. Srivastava

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FRA tests in the frequency range up to 10 MHz were investigated using simulations and measurements. It was found that the FRA test was more sensitive to changes in the transformer at frequencies above 1 to 3 MHz than at lower frequencies. However, the effects of the conventional test circuits mask the changes at the higher frequencies. A new test method is(More)
This paper presents an electrostatic study of free conducting particles that contaminate com pressed gas-insulated high voltage apparatus and transmission lines. Analytical and numerical techniques are used to describe the effect of the particle charge and the magnitude of the ambient electric field on the field intensification on and near the particle(More)
Online transformer condition monitoring techniques based on transfer function methods, such as transmission-line diagnostics and swept frequency-response analysis, require the injection of a known test signal into the transformer. On larger power transformers, a practical method is to use the available bushing tap connection. In this paper, we will discuss(More)
Many researchers have suggested that the space charge field of the primary electron avalanche should not be neglected in calculating the corona onset voltage based on the streamer criterion. Some researchers consider only the space charge field of the positive ions created during the avalanche growth, while others consider only the space charge field of the(More)
An experimental and theoretical study is presented in this paper on the corona characteristics of conductor bundles under dynamic overvoltages. Measurements have been made in the outdoor test cages of Institut de recherche d'Hydro-Quebec (IREQ) on two bundles, under conditions of fair weather and heavy rain, for steady 60 Hz voltages as well as dynamic(More)
This paper presents data from a study conducted to identify the key factors that contribute to frequency response analysis (FRA) measurement results. The results show that the lower the shunt impedance, the higher the sensitivity of the FRA measurement for the detection of winding movement. On transformers with large bushings, the bushings can mask the(More)
The effect of the front of impulse voltages on the breakdown of nonuniform gaps in SF6 has long been reported to be unsystematic. The present study provides an explanation to this phenomenon by examining the breakdown probability distributions of rod- plane gaps in SF6 over a wide range of gas pressure and under different impulse wave forms. The(More)
The lifting field of a free conducting particle (FCP) situated on a dielectric coated electrode in compressed SF6 gas is calculated based on two different particle charging mechanisms-partial discharges occurring in the gas surrounding the particle and charge conduction through the dielectric coating. Calculated values are compared with experimental results(More)
In clean SF6 gas-insulated power transmission systems significant pre-breakdown discharges are rarely observed. This is so because the prevailing electric field is only moderately non-uniform. In practical systems, however, conducting particle contamination creates regions of highly non-uniform fields. Initial ionization, under contaminated conditions,(More)
A knowledge of the distribution of lightning strokes to towers and along the span of shielded power lines is needed to refine the outage rate calculation method. Such information is also needed for unshielded line because the outage mechanism differs depending on whether the stroke terminates on a tower or on a live wire. The authors provide the needed(More)