Capacitors are a good example of the fact that even simplest device can become complicated given 250 years evolution.

The theoretical sensitivity of conventional partial discharge detectors is compared with that obtained from ultra wideband (UWB) (up to l GHz) detection systems. comparison indicates for relatively lossfree distributed systems, such as SF6 insulated bus, the UWB system up two orders magnitude more sensitive. also embodies additional advantages facilitating location sites and rejection external electrical noise. For in plastic-insulated cables, true not practical because frequency-dependent...

It is shown how a partial discharge (PD) within test sample generates signal that can be measured outside the apparatus under test. Because transfer function between phenomenon and vary widely, partial-discharge magnitudes rarely have absolute meaning are often referred to as effective magnitude acknowledge this uncertainty. The most common sources of PD floating components, corona, voids. Each these considered in turn, fundamentals current external circuit explained.< <ETX...

The development of solid dielectric DC transmission class cable is a priority throughout much the world to avoid risks associated with placing hydrocarbon fluids in underwater environments. However conductivity polymeric dielectrics tends be strong function temperature and electric field. Based on measured material properties, we demonstrate effect such dependences field grading for range properties provide an analytical approximation computing resistively graded including field-dependent...

An article providing background on fundamentals of partial discharge, especially as related to field PD testing cable systems.

For pt.II see ibid., vol.6, no.5, p.35 et seq. (1990). The question of how to relate the magnitude measured, effective, partial discharge (PD) size, shape, and position cavity within a solid dielectric system is addressed. causes cavities are examined, brief review gas breakdown given. It then shown that for range geometries, such as parallel plate coaxial, one can develop analytic solutions (i.e. formulas), any solution be found using computer-based methods calculating electric field...

Fourteen polyene antibiotics and six of their semisynthetic derivatives were compared for effects on potassium (K + ) leakage lethality or hemolysis either Saccharomyces cerevisiae mouse erythrocytes. These fell into two groups. Group I caused K cell death at the same concentrations added polyene. In this group fungistatic fungicidal levels indistinguishable. drugs included one triene (trienin); tetraenes (pimaricin etruscomycin); pentaenes (filipin chainin); hexaene (dermostatin);...

Field tests have been carried out which permitted direct measurement of disconnect switch operation induced transients in an operating 500 kV substation. These measurements indicate that do not exceed 2 pu at the point and trapped charge left on load side is less than 0.3 pu. Further study way switches operate indicates during opening depends detailed design switch.

The effect of altered products the antioxidant by UV irradiation on dielectric breakdown strength metallized biaxially-oriented polypropylene (BOPP) capacitor film was studied. Results from Weibull statistical analysis show that an optimal exposure level ~3.4 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (200-400 nm) increases at 5% probability ~20%. As indicated spectroscopic analysis, in BOPP consumed almost entirely to form...

Inhomogeneous field breakdown in SF/sub 6/ has been investigated, and a theory developed which predicts the voltage for fast-rising (rectangular) waveforms applied to arbitrary electrode geometries gas pressures. This facilitates analytical design aspects of many GIS components where previously, engineering judgement development testing were necessary. It is suggested that extensions theory, will permit prediction an surge waveform, facilitate assessment test waveform efficacy more reliable...

The design of concentric-neutral plastic-insulated power cables has been optimized for the transmission and distribution large quantities 60-Ηz at high voltages. Understanding mechanism frequency propagation in these is important order to evaluate sensitivity partial discharge measurements [1,2]. Partial discharges solid insulation generate frequencies ranging several hundred MHz [3]. With wide band detection, location sites cable through pulse timing techniques also possible [4,5,6].

PD testing and location is an essential part of factory shielded solid dielectric power cable. The accuracy with which a source can be located limited by high frequency attenuation pulses as they propagate through the

Silicone-based materials for outdoor insulators have the advantage that low molecular weight (LMW) components migrate through material and coat surface, thereby restoring hydrophobicity over a period of hours. By measuring IR absorption siloxane migrating to silicone surface thin carbon coating, time constant migration was calculated. According dependence IR-absorbance, ranged from 1.6 5.3 h depending on alumina trihydrate (ATH) filler concentration.

The effect of various chemical impurities in polyethylene on the electronic structure, trap depths, electron density, interchain interaction, etc. has been studied through use density functional theory. Quantum mechanical description impurity states is provided. estimated depth deep traps introduced directly by and shallow indirectly induced local disorder are agreement with experimental estimates literature.

Conventional loading of induction motors is an ex- tremely difficult and expensive process for large machines.In those cases, full load losses temperature rise can be estimated by means equivalent methods, which provide accurate altemative, without the need a mechanical applied to shaft.This paper describes three such all using commercial PWM inverter.The methods examined are described in detail results performed on 10 hp motor presented.A calorimetric measurement facility was used order...

For pt.I see ibid., vol.3, no.3, p.923-30 (1988). An improved model for the calculation of statistical time lags in SF/sub 6/ insulated electrode arrangements positive impulse voltage is presented. On basis physical considerations, production rate initial electrons ascribed to local density negative ions and field dependent electron detachment. Values ion densities are measured directly, while detachment coefficient determined by a fitting procedure measurements lags.< <ETX...

Space charge formation and its increase with field under DC conditions is not a mystical phenomenon. The in space applied an obvious inevitable result of the interaction field-dependent current density spatially inhomogeneous resistivity. For common polymeric dielectrics, makes transition from linear function to exponential at around 10 kV/mm. This causes similar sample same region. However, this has no connection aging, if it does prove have connection, driving force rapidly increasing...

All dielectrics are nonlinear if subjected to sufficiently high electric fields. A degree of dielectric nonlinearity can bring simplicity many problems, especially those involving highly inhomogeneous field geometries. Given the simplifying assumptions that result from nonlinearity, distribution often be computed analytically good accuracy, which is desirable given alternative a numerical computation. This article discusses three examples in conditions affect performance manner easily...

A theoretical study was carried out to determine the dielectric response and tunability of a composite consisting linear, low-loss matrix with uniformly sized, randomly distributed paraelectric Ba0.60Sr0.40TiO3 (BST 60/40) particles as functions volume fraction size particles. The field dependence polarization inclusions are specified through nonlinear thermodynamic model then incorporated into two-dimensional finite element analysis. Near percolation threshold for BST (∼27% 45% depending on...

The very rapid dielectric breakdown of SF6 (eg, during the operation disconnect switches in gas-insulated substations) generates steep-fronted travelling waves which couple to exterior enclosure surface at air/SF6 bushings and cause transient ground potential rise. These high voltage transients, can be 100 kV range, propagate from termination, along a transmission line defined by bus plane, toward switchgear. This paper presents theoretical experimental investigation phenomenon, basic...

The fully enclosed nature of gas- insulated substations substantially increases the difficulty testing, maintaining, and troubleshooting switchgear. Under EPRI sponsorship, Ontario Hydro has developed systems for fault location in gas cables partial discharge substations.

The basic quantum mechanical theory for intrinsic breakdown was developed by von Hippel and Fröhlich over 70 years ago, but only now can we exploit their ideas accurately through the use of computational mechanics. As shown above, Hippel's low energy criterion provides remarkably good agreement with measured data a range both ionic covalently bonded materials. We correlate bandgap phonon cutoff frequency, although relationships differ different groups challenge going forward is to move from...