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.

Survey of Insulation Systems in Electrical Machines

Abstract: Insulating materials and insulation systems design have been gaining more attentions as more electrical machines tend to operate in harsher environments for various applications. Harsh environments include high temperature, humidity, erosion, low air pressure, etc. This paper discusses recent advances in insulation systems for electrical machines. Insulation tests as well as test standards that have been used to evaluate insulation systems and detect insulation failures will be discussed. Insulating materials used for a wide range of industrial applications such as wind turbine generators, aerospace hybrid/electric powertrain, and hydro generators have been summarized. For the emerging high-altitude, highvoltage aerospace applications, partial discharge and its impact on insulation systems will be discussed. Finally, polymer nanocomposite materials with excellent thermal conductivity and dielectric strength are highlighted as an outlook.

Dielectric Strength of Transformer Insulation

Abstract: This paper presents a summary of the results of over 2,000 tests on the dielectric strength of transformer oil and insulating material for impulse, switching, and 60-cycle voltages. From these tests the voltage-time characteristics of the 2 insulations tested may be established over the entire range from a fraction of a microsecond to more than one minute.

Degradation of Polyethylene by Partial Discharge

Abstract: To explore the fundamental concept concerning testing methods of corona resistance of insulating materials, some "roundrobin" tests with polyethylene have been performed by means of parallel-plate electrodes. The specimen films, degraded under the conditions of 6 kV ac impression and of static dry air, are examined with regard to weight, infrared spectrum, and other changes. From these results, information about degradation mechanisms was obtained. From these studies, the corona degradation behavior of polyethylene might be considered to include two kinds of chemical reactions. First, activated oxygen formed by discharge is able to oxidize perfectly the surface of the specimen exposed directly to discharge and to yield H2O, CO2, and other products, although the portion not directly exposed to the discharge is hardly affected owing to the extremely short life of these active species. At the same time, ozone with relatively long life diffuses into polyethylene and is able to form an ozonide by reacting with a terminal double bond, while it makes carboxylic acid and others by combining with the main chain in the polymer. Moreover, nitrogen oxide causes nitrate ester to be formed. Several conditions may control these two competitive reactions and the degree of competition is probably the reason for the fluctuation of results.

Partial discharge parameters to evaluate the insulation condition of on-line located defects in medium voltage cable networks

Abstract: Partial discharge analysis has a long record as reliable diagnostic tool to assess the integrity and the quality of electrical insulation of power systems. On-line partial discharge monitoring systems for live medium voltage cable connections have recently been introduced in Dutch grids and also a few worldwide. To enhance the applicability of on-line cable diagnostics there is a need to develop a PD interpretation approach suitable for on-line monitoring. This paper discusses various PD parameters, including PD charge magnitude, PD occurrence rate and PD charge density and their related statistical values such as mean and maximum, used to interpret the PD activity. Trend watching of these parameters is employed to study the degradation state of cable connections and their components. The approach is applied to field data obtained over a year through monitoring several live circuits. In this paper, three examples are presented. Weak spots were detected and failures were prevented by early warning.

Investigation of propagation of partial discharges in power transformers and techniques for locating the discharge

Abstract: The location of partial discharges in a power transformer can be determined based on the characteristics of the transfer function from the discharge source to the measuring terminal. Previous studies partially validated the technique using computer simulation and practical experiments based on a PD calibrator to represent a discharge signal. 'Real' discharges produced by insulation defect models were used to study how discharges propagate in an 11 kV plain-disc-type transformer winding: A corona model and a 'floating objects in oil' model produced discharge signals with different durations at various locations along the winding. Measurements were taken at the tap of the bushing capacitance through a conventional discharge detector. The signals were filtered, amplified and fed into a digital storage oscilloscope. The frequency spectra of the measured signals showed significant similarities irrespective of the type of discharge source. The characteristic of the transfer functions, i.e. the crests and troughs in the spectra, could be used for locating the source of the discharge. Energising the transformer increased the level of electric noise, which did affect the low frequency end of the spectra, but did not have any impact on the characteristics used for location.