Characterization of surface discharge as indicator for hydrophobicity evaluation of silicone rubber insulators

Abstract

A Dynamic drop test (DDT) has been employed for hydrophobicity evaluation, which has proven the occurrence of different discharge phenomena in relation to the hydrophobicity variation. In this paper, based on DDT method, the characterization of surface discharges, including the discharge magnitude, pulse number, adjacent discharge magnitude and adjacent time interval, have been analyzed to evaluate the surface hydrophobicity of silicone rubber insulator. It is found that with the decrease of hydrophobicity, these characteristics apparently show an increasing tendency. The characteristic pattern of discharge pulse and discharge magnitude presents a twin-peak shape, in which both the increase of the discharge magnitude and the discharge pulse number of higher magnitude reflect the decrease of surface hydrophobicity. The characteristic pattern of adjacent discharge magnitude and discharge magnitude emerges to be an 'X' shape composed by the discharge spots, in which the larger value in both the spot density and the shape expansion reveals the decreasing hydrophobicity. The characteristic pattern of next time interval and discharge magnitude demonstrates the frequency of surface discharges increases with the decrease of surface hydrophobicity. Furthermore, the comparability between the discharge characteristic methods and the contact angle method is analyzed to obtain the higher similarity coefficients. Obtained results indicate that the characteristic of surface discharge in DDT method can be utilized to the hydrophobicity evaluation.

Assessment of the resistance to tracking of polymers in clean and salt fogs due to flashover arcs and partial discharges degrading conditions on one insulator model

“…HDPE also exhibits the lowest magnitude in clean fog with enhanced surface degradations while it is the highest in salt fog with no remarkable degradation. Du et al [38] and Liu and Du [39] reported that the increase of PDs magnitude and pulse number at positive and negative cycles are well in accordance with the decrease of surface hydrophobicity. This is the case for salt fog conditions where water droplets density is higher due to the presence of salt substances which reduce the contact angle.…”

Naive Bayesian classifier for hydrophobicity classification of overhead polymeric insulators using binary image features with ambient light compensation

“…It is one of the widely used machine learning technique for both binary classification and multi-class classification problems. NBC is based on Bayes theorem to calculate the conditional probability (P H c f s ) for the given image features ( f s ) belong to a particular class of hydrophobicity (H c ) as in (10). It is simple to be constructed and suitable for high dimensionality systems…”

Effect of direct fluorination on partial discharge characteristics of polyimide film used as magnet wire insulation of generator

“…The adjacent discharge magnitude, which is related to the discharge magnitude, represents the strength of successive discharge. Then the relationship among the number of discharge pulse, the adjacent discharge magnitude and the discharge magnitude can be obtained [30]. The changing rate of signal (d u /d t ) is calculated by the changing value (d u ) divided by the corresponding time (d t ), which was closely related to the emitting rate of PD energy.…”