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.

Evaluation of UHF method for partial discharge measurement by simultaneous observation of UHF signal and current pulse waveforms

Abstract: The partial discharge - current pulse waveform analyzing (PD-CPWA) system can measure partial discharge (PD) current pulses continuously in high speed, and is being used for the study of PD mechanisms in SF6 gas in a laboratory. On the other hand, the ultra high frequency (UHF) method is becoming popular for the on-site monitoring of gas-insulated switchgears (GIS). The former can detect PD with high accuracy and make it possible to analyze and understand discharge physics in detail. The latter is suitable to detect PD in actual power equipment, even in noisy site condition. Clarification of coincidence of PD characteristics measured with both methods is very important for further application of the UHF method. In this paper, PD current pulses generated from artificial defects in SF6 gas were synchronously measured with both methods. Measured data were analyzed and compared in many PD characteristics. As a result, many characteristics coincided well between them. However, the scatter of PD and the limited equipment performance of the UHF method may cause some detection failures. An appropriate and advanced use of the UHF method was pointed out.

Generation of high-power-density atmospheric pressure plasma with liquid electrodes

Abstract: We present a method for generating atmospheric pressure plasma using a dielectric barrier discharge reactor with two liquid electrodes. Four distinct kinds of discharge, including stochastic filaments, regular square pattern, glow-like discharge, and Turing stripe pattern, are observed in argon with a flow rate of 9slm. The electrical and optical characteristics of the device are investigated. Results show that high-power-density atmospheric pressure plasma with high duty ratio in space and time can be obtained. The influence of wall charges on discharge power and duty ratio has been discussed.

A comment concerning the rise times of partial discharge pulses

Abstract: The influence of the discharge mechanism upon the rise time of partial discharge pulses is examined. In contrast to the long rise times characterizing the discharge pulses generated by glow discharges, spark discharges exhibit typically short rise times and large magnitude pulses. The occurrence of the latter is favoured by cavities wherein there is a paucity of free electrons that are necessary for electron avalanche formation. As a consequence, breakdowns across these cavities occur under overvoltage conditions, thus leading to space charge formation and photoemission at the cathode; this results in a rapid development of constricted spark-type breakdown channels. The question of detectability of short and long rise time pulses, utilizing PD detectors having different bandwidths, is considered both in the proximity to, as well as far removed from, the discharge sites.

Multiple partial discharge source discrimination with multiclass support vector machines

Abstract: Different types of partial discharges are created with test objects in laboratory.Their frequency content depends on the type of discharge and other external factors.An SVM extracts characteristics from the power spectral density of the pulses.Noise, corona, internal and surface discharges have different characteristics.The differences are used to classify discharges and separate them from noise. The costs of decommissioning high-voltage equipment due to insulation breakdown are associated to the substitution of the asset and to the interruption of service. They can reach millions of dollars in new equipment purchases, fines and civil lawsuits, aggravated by the negative perception of the grid utility. Thus, condition based maintenance techniques are widely applied to have information about the status of the machine or power cable readily available. Partial discharge (PD) measurements are an important tool in the diagnosis of power systems equipment. The presence of PD can accelerate the local degradation of insulation systems and generate premature failures. Conventionally, PD classification is carried out using the phase resolved partial discharge (PRPD) pattern of pulses. The PRPD is a two dimensional representation of pulses that enables visual inspection but lacks discriminative power in common scenarios found in industrial environments, such as many simultaneous PD sources and low magnitude events that can be hidden below noise. The literature shows several works that complement PRPD with machine learning detectors (neural networks and support vector machines) and with more sophisticated signal representations, like statistics captured in several modalities, wavelets and other transforms, etc. These methods improve the classification accuracy but obscure the interpretation of the results. In this paper, the use of a support vector machine (SVM) operating on the power spectrum density of signals is proposed to identify different pulses what could be used in an online tool in the maintenance decision-making of the utility. Particularly, the approach is based on an SVM endowed with a special kernel that operates in the frequency domain. The SVM is previously trained with pulses of different PD types (internal, surface and corona) and noise that are obtained with several test objects in the laboratory. The experimental results demonstrate that this technique is highly effective in identifying PD for cases where several sources are active or when the noise level is high. Thus, the early identification of critical events with this approach during normal operation of the equipment will help in the decision of decommissioning the asset with reduced costs and low impact to the grid reliability.