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.

Double discharges in unipolar-pulsed dielectric barrier discharge xenon excimer lamps

Abstract: Excitation of dielectric barrier discharge xenon excimer lamps by unipolar short square pulses is studied in this paper. Two discharges with different polarity are excited by each voltage pulse (double discharge phenomenon). The primary discharge occurs at the top or at the rising flank of the applied unipolar square pulse, which is directly energized by the external circuit. The secondary discharge with the reversed polarity occurs at the falling flank or shortly after the falling flank end (zero external voltage) depending on the pulse width, which is energized by the energy stored by memory charges deposited by the primary discharge. Fast-speed ICCD imaging shows the primary discharge has a conic discharge appearance with a channel broadening on the anode side. This channel broadening increases with increasing the pulse top level. Only the anode-side surface discharge is observed in the primary discharge. The surface discharge on the cathode side which is present in bipolar sine voltage excitation is not observed. On the contrary, the secondary discharge has only the cathode-side surface discharge. The surface discharge on the anode side is not observed. The secondary discharge is much more diffuse than the primary discharge. Time-resolved emission measurement of double discharges show the secondary discharge emits more VUV xenon excimer radiation but less infrared (IR) xenon atomic emission than the primary discharge. It was found that the IR xenon atomic emission from the secondary discharge can be reduced by shortening the pulse width. The energy efficiency of unipolar-pulsed xenon excimer lamps (the overall energy efficiency of double discharges) is much higher than that obtained under bipolar sine wave excitation. The output VUV spectrum under unipolar pulse excitation is found to be identical to that under sine wave excitation and independent of injected electric power.

Partial Discharge - Part 111: Cavitv-Induced PD in Solid Dielectrics

Abstract: n the first paper of the series, we discussed the nature of partial discharge (PD), and how a PD I associated with a test object causes a current to flow in the test leads. The second paper of the series discussed the options for detecting such a signal. With this paper, the series begins the move toward applicationsspecific content which will lead to a series of papers on I'D testing of specific types of electrical apparatus, such as solid dielectric power cable, rotating machines, printed circuit boards, gas-insulated substations, etc. Cavities (sometimes termed "voids") within solid or viscous liquid dielectrics are among the most common sources of PD in such systems. For this reason, along with the recent progress in the field, we will devote a paper to the subject. The basic problem can be stated in either of two contexts, viz., "How do we relate the magnitude of the measured, 'effective', PD to the size, shape, and position of the cavity within a solid dielectric system?" or "What is the relationship between cavity size and 'effective' I'D magnitude in a given context?", i.e., 'What is the smallest detectable cavity?" For a range of geometries, such as parallel plate and coaxial, we can develop analytic solutions (i.e., formulas), and for any system, the solution can be found using computer-based methods for calculating the electric field throughout a sample.

The analysis of ultrasonic signals by partial discharge and noise from the transformer

Abstract: This paper presents the analysis of ultrasonic signals by the partial discharge in a model transformer as well as by corona in the air at a shielded high-voltage laboratory. In addition, various noises onsite, a 345-kV substation, were measured and analyzed, for example, the vibration by core magnetostriction, cooling pump, cooling fan, onload tap changer (OLTC) operation, OLTC filtering unit operation, and air discharge pulse by corona on the transmission line. Therefore, electrical and mechanical noises onsite were removed using the proper narrow bandpass filter and the noise discrimination algorithm. Also, the developed online ultrasonic detector was applied to detect partial discharge in a 154-kV transformer with a warning level in C/sub 2/H/sub 2/ gas. As a result of an internal inspection, the source of partial discharge was found at the estimated position based on ultrasonic detection and its reliability was verified.

Discharge lamp starting circuit

Abstract: When a discharge lamp is started, high voltage pulses which superpose the voltage due to LC resonance of a resonance circuit are supplied to the discharge lamp, and breakdown occurs in the discharge lamp. The pulse energy needed for the high voltage pulses is small and the output power of the resonance circuit can be decreased. After the breakdown, the energy needed for the transfer from glow discharge to arc discharge is supplied by the resonance, and the high voltage pulses used to supply the starting energy are allowed to be stopped. Thus, the starting and restriking of a discharge lamp is sure, and the starting circuit for a discharge lamp can be made more compact.

Insulation performance of three types of micro-defects in inner epoxy insulators

Abstract: Gas insulated switchgear (GIS) has been widely applied in power equipment since the late 1960s due to its reliability and compactness. Because epoxy insulators in GIS are important insulation components that affect the dielectric withstand level and the equipment lifetime, high voltage tests and sensitive partial discharge (PD) tests have been carried out on them in the factory. If a latent defect occurs inside an actual epoxy insulator, its size is predicted to be small, such as a micro-defect, because it will have passed rigorous tests and multiple inspections at the factory. Although many studies have clarified the fundamental phenomena of deterioration caused by PD occurring due to defects in inner epoxy, little is known about the actual size of such defects and their effect on insulation properties. Therefore, to assess the risks associated with aging GIS equipment, it is essential to understand the actual size of latent defects in inner epoxy insulators of GIS and the impact the defects have on the insulation performance. The puncture properties and PD characteristics of artificial micro-defects of cracks, voids, and delaminations produced using an accurate estimation technique and precise production control were investigated and are described. The results suggest that an estimation method using electric field analysis is useful for designing the defect shape and that the breakdown voltage depends on the three-dimensional shape of the defect. Techniques for accurate estimation of small defects in epoxy resin and stable production of micro-defects have thus been achieved.