Abstract-High Frequency Current Transformer (HFCT) sensors are widely used for Partial Discharge detection due to their versatility, high sensitivity and wide bandwidth. This paper reports on a Finite Element Analysis (FEA) methodology that can be employed to optimize HFCT performance. The FEA model consists of accurate 3D representations of the sensor components. Two different FEA software modules were used in order to cover the wide operating frequency range of the sensor. The simulation computes the frequency response of the sensor in the range 0.3 MHz -50 MHz for various HFCT geometric and material parameters, specifically the number of winding turns, spacer thickness, aperture size and core material. A prototype HFCT was constructed and the measured response compared with that of the simulation. The shapes of the responses were similar, with the simulated sensitivity being higher than the measured sensitivity by 1 dB on average. The measured low frequency cutoff of the sensor was found to be only 0.05 MHz lower than that of the simulation.

No abstract

This paper considers the measurement and propagation of partial discharge pulses on distribution class power cable circuits, with the idea of attempting to determine discharge location sites on cables based on the parameters of individual pulses. Single-ended discharge location techniques based on partial discharge pulse parameters and shape will not be as accurate as time-domain reflectometry methods but can be done on-line without the need for double-ended techniques. Power cables used for the transmission of 50/60 Hertz electrical power, are by design not intended to carry transients or partial discharge pulses. The geometry and construction of such power cables present a transmission line that can heavily attenuate and distort the partial discharge pulses, making their detection and discrimination all the more difficult. Experimental and field work has been carried out to develop basic knowledge rules to describe how the time-domain parameters of individual pulses alter as a function of the distance propagated from the discharge sites for medium voltage power cables.Index Terms-On-line, power cable, pulse broadening, Time-domain Reflectometry, partial discharge, pulse propagation.

Computations of the evolution of the electron distribution function in a plasma subsequent to the excitation of a constant finite amplitude electron plasma wave show that the system is stable for plasma parameters for which under experimental conditions the sideband instability is found to be excited. When the time (or space) variation of wave amplitude is included a group of particles initially trapped is detrapped and then behaves like an electron beam passing through the plasma. The experimental dispersion of test waves in a low density plasma is compared with theoretical predictions for parameters given by the detrapping model. Further, measurements of the electron distribution function in the presence of a finite amplitude wave as a function of position, wave amplitude, and wave frequency, show features which are consistent only with a detrapped beam.