Partial discharge

About: Partial discharge is a research topic. Over the lifetime, 13997 publications have been published within this topic receiving 102058 citations. The topic is also known as: PD.

Application and Suitability of Polymeric Materials as Insulators in Electrical Equipment

Abstract: In this paper, the applications of thermoplastic, thermoset polymers, and a brief description of the functions of each subsystem are reviewed. The synthetic route and characteristics of polymeric materials are presented. The mechanical properties of polymers such as impact behavior, tensile test, bending test, and thermal properties like mold stress-relief distortion, generic thermal indices, relative thermal capability, and relative thermal index are mentioned. Furthermore, this paper covers the electrical behavior of polymers, mainly their dielectric strength. Different techniques for evaluating polymers’ suitability applied for electrical insulation are covered, such as partial discharge and high current arc resistance to ignition. The polymeric materials and processes used for manufacturing cables at different voltage ranges are described, and their applications to high voltage DC systems (HVDC) are discussed. The evolution and limitations of polymeric materials for electrical application and their advantages and future trends are mentioned. However, to reduce the high cost of filler networks and improve their technical properties, new techniques need to be developed. To overcome limitations associated with the accuracy of the techniques used for quantifying residual stresses in polymers, new techniques such as indentation are used with higher force at the stressed location.

Stacked substrates for high voltage applications

Abstract: A new way of insulation high voltages in modules is described, solving the problem of high electric fields at sharp corners with multilayer structures. Today, modules with a blocking voltage above 1700V are based on Si3N4 or AlN substrates. Special effort is required to manage the high electric fields that occur at the sharp edges of the metal layers on both sides of the ceramic layer. Simulations show that stacking substrates can significantly reduce the peak electric fields that are generated. This allows cheaper isolation solutions such as partial discharge Al2O3 ceramics can be used to replace the more expensive AlN or Si3N4 ceramic. The Influence of ceramic and metallization thickness as well as the layout design have been discussed. The simulations have been confirmed by measurements. Finally limitations of the stacked structures are highlighted and suggestions are made for practical use in modules.

Ultrasonic Spectrum Signatures of Under-Oil Corona Sources

Abstract: Ultrasonic techniques are useful for the detection and location of partial discharge or corona sources associated with HV power apparatus, particularly oil-filled power transformers. Measurements are commonly made using narrow-band transducers operating in the frequency range from ~20kHz to ~300 kHz, and occasionally at higher frequencies for which there is little published information. Because of the lack of available data on the spectra of ultrasonic emissions from discharges in oil-insulation systems, an investigation was initiated to determine if there was an optimum measuring frequency and whether discharges could be identified by their spectral characteristics. It was discovered that insulation voids and gap-type discharges, for example, have clearly identifiable ultrasonic frequency characteristics, and the actual physical size of voids may be estimated from their frequency spectra.

Examples of stator winding partial discharge due to inverter drives

Abstract: Random wound stator windings in motors have failed when exposed to the fast-risetime voltage surges coming from inverters. Measurements on motors show that these surges can create partial discharges and these discharges eventually destroy the turn-to-turn and/or phase-to-phase insulation, resulting in premature motor failure. Since the risetime of the voltage surges is in the same order of magnitude as the risetime of the PD pulses themselves, it is very difficult to separate the PD from the surges. Thus there has been little characterization of the PD caused by IFDs. Using a new device that can separate the PD from the surges, preliminary measurements of discharge inception voltage from several different motors, as well on twisted pairs of magnet wire were made. The DIVs under surge voltage are significantly higher than those made with 60 Hz voltage. As expected, the PD magnitude increases dramatically with applied surge voltage. PD pulses occur during a small percentage of the surges.

Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge

Abstract: The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly 'flat top' distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present work demonstrates that this effect may be used to control the phase of AC barrier discharges, triggering reproducible breakdowns at well-defined moments.