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

Ueta, Genyo; Wada, Junichi; Okabe, Shigemitsu; Miyashita, Makoto; Nishida, C.; Kamei, Mitsuhito

doi:10.1109/tdei.2012.6215098

Cited by 53 publications

(21 citation statements)

References 12 publications

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“…The POS is a conductive contaminant or particle that adheres to the surface of insulating materials. Cracks are one of the most common defects in GISs, which are formed due to mechanical impacts from the outside, operations of the circuit breaker, and strains generated by heat shock [7,8,21]. These three types of defects were simulated using artificial PD cells, and the epoxy resin insulator for GIS spacer was used.…”

Section: Insulation Defects In Spacermentioning

confidence: 99%

“…Among the components of GISs, the epoxy spacer is a critical part and can result in the eventual failure of GISs. It is usually examined by AC withstand voltage tests with high electrical stress and by PD tests [7,8]. It is specified that the maximum permissible PD level for GISs should not exceed 5 picocoulombs (pC) [9].…”

Section: Introductionmentioning

confidence: 99%

“…It is specified that the maximum permissible PD level for GISs should not exceed 5 picocoulombs (pC) [9]. It is also indicated that the spacer should be replaced if the PD induced in spacer is greater than 1 pC [7]. However, the sensitivity of PD measurement is influenced by the capacitive current flowing in the GIS test section, especially in the spacer.…”

Section: Introductionmentioning

confidence: 99%

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Disturbance Elimination for Partial Discharge Detection in the Spacer of Gas-Insulated Switchgears

Wang

Kil

et al. 2017

Energies

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With the increasing demand for precise condition monitoring and diagnosis of gas-insulated switchgears (GISs), it has become a challenge to improve the detection sensitivity of partial discharge (PD) induced in the GIS spacer. This paper deals with the elimination of the capacitive component from the phase-resolved partial discharge (PRPD) signal generated in GIS spacers based on discrete wavelet transform (WT). Three types of typical insulation defects were simulated using PD cells. The single PD pulses were detected and were further used to determine the optimal mother wavelet. As a result, the bior6.8 was selected to decompose the PD signal into 8 levels and the signal energy at each level was calculated. The decomposed components related with capacitive disturbance were discarded, whereas those associated with PD were de-noised by a threshold and a thresholding function. Finally, the PRPD signals were reconstructed using the de-noised components.

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Section: Insulation Defects In Spacermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Disturbance Elimination for Partial Discharge Detection in the Spacer of Gas-Insulated Switchgears

Wang

Kil

et al. 2017

Energies

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“…The height of each defect is less than 0.6 mm, which is much smaller than those used in previous researches. Refer to the previous report [16] for further information such as the design concept, PD magnitude, and production methods.…”

Section: Precise Estimation Of Practicalmentioning

confidence: 99%

“…Firstly, with regard to the PD phenomenon, Section 2 presents the detailed observation results of the PD current of the discharge in gas up to a high frequency band exceeding 10 GHz [15], as well as the study results of the insulation characteristics where micro-defects are present inside the epoxy insulator [16], the detectability of the UHF method with respect to the length of harmful particles inside GIS [17], and both experimental and numerical approaches on propagation phenomena of PD signal in GIS [18]. Subsequently, with regard to further refinement of the diagnostic technique and the calibration and verification method, Section 3 describes a new less uncertain and inexpensive UHF sensor calibration system using a conical antenna [19,20] and a more advanced UHF diagnostic technology whereby the influence of the shape and structures of GIS on PD signal propagation is taken into consideration [21,22], as well as a UHF measurement system sensitivity verification method on the site using a network analyzer [23] to substitute the CIGRE method [13], and the novel technique for PD and breakdown investigation based on current pulse waveform analysis [24].…”

Section: Introductionmentioning

confidence: 99%

New aspects of UHF PD diagnostics on gas-insulated systems

Okabe

Ueta

Hama

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

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Gas insulated switchgears (GIS) have been increasingly introduced as main substationequipment since the late 1960s thanks to their high reliability, safety, and compactness. The UHF method to diagnose partial discharge (PD) is broadly employed in the field as an advanced insulation diagnostic technology. There are three primary factors related to the PD signal detection characteristics using this UHF method; namely the frequency spectrum of the PD signal itself inside GIS, the propagation characteristics of the PD signal inside the GIS tank, and the detection characteristics of the sensor measuring the PD signal. Accordingly, to further improvement of the diagnostic technique based on the UHF method, the PD phenomenon itself and its propagation characteristics should be clarified and the measurement system refined. From these perspectives, the present study reviewed the recent and latest findings concerning the PD phenomenon and its propagation characteristics inside GIS as well as the PD measurement system verification methods and diagnostic technologies, and summarized typical examples. Firstly, with regard to the PD phenomenon, measurement up to the high frequency band exceeding 10 GHz (even 30 GHz) clarified that the rise time of the PD current waveform is several tens of picoseconds, shorter than previously known. In the case of PD in micro-defects inside the epoxy insulator, however, the rise time is relatively long, in the order of nanoseconds, and a crack is the most critical defect. Subsequently, with regard to UHF PD diagnostics/monitoring technology, a novel technique using PD current waveform characteristics has been developed, and a more advanced PD diagnostic algorithm has been established by clarifying the influence of the shape and GIS internal structures on the electromagnetic wave propagation characteristics. Less uncertain and simplified calibration and verification technologies are also proposed both for a single UHF sensor and the entire UHF measurement system. These new technologies and further advanced studies in future are expected to make the UHF method more convenient and sophisticated.

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