• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1694-1696
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• 2001

Partial discharge(PD) tests are used to evaluate the insulation condition of stator windings in six 6.6kV motors. These tests were conducted using a conventional partial discharge detector (PDD), turbine generator analyzer(TGA) and partial discharge analyzer(PDA). Off-line PD measurements were performed on six 6.6kV motors. PD magnitudes ranged from 740 pC to 5,100 pC at the normal line-to-ground voltage. Six 6.6kV motors have been equipped with eighteen 80pF epoxy-mica couplers(one per phase) on the motor terminal boxs. The PD pulse from sensors were measured with the TGA and PDA instruments on a normally operating motors. The PDD, TGA and PDA test results showed that internal discharge was detected in voids of the groundwall insulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.251-256
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• 2012

This study deals with the location of partial discharges(PDs) for power cables and GIS using 2 PD sensors and long coaxial signal cables. Throughout the experiments by use of simulated PD pulses and corona discharges in the power cable system, it is found out that the impedance matching between the coaxial signal cable and the measuring equipment should be done for good S/N ratio and the on-site measurement using more than 100m-long coaxial signal cable is possible. In addition, new PD location algorithm with the polarities of PD pulses and the arrival time difference between two pulses was proposed and was proved through the partial discharge experiments for the cable joint defect and artificial void defect.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1652-1654
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• 2002

The defects making partial discharge(PD) in a C-GIS(Cubicle Insulated Switchgear) initiate acoustic wave which can be detected using acoustic emission sensor placed outside or inside the C-GIS enclosure. In this paper, partial discharge property for 2 locations for AE sensor and 3 locations for defects in C-GIS are presented and PD waveforms were analyzed by PRPDA(Partial Resolved Partial Discharge Analysis). As a result, using post amplifier having gain of 10,000 and band pass filter having $20kHz{\sim}300kHz$, resolution of waveforms AE sensor signal by detected was good. Noise level was about 80 mV.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.344-354
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• 2015

In order to study the development of partial discharge (PD) under typical protrusion defects in gas-insulated switchgear, we applied step voltages on the defect and obtained the ${\varphi}-u$ and ${\varphi}-n$ spectrograms of ultra-high frequency (UHF) PD signals in various PD stages. Furthermore, we extracted seven kinds of features to characterize the degree of deterioration of insulation and analyzed their values, variation trends, and change rates. These characteristics were inconsistent with the development of PD. Hence, the differences of these features could describe the severity of PD. In addition, these characteristics could provide integrated characteristics regarding PD development and improve the reliability of PD severity assessment because these characteristics were extracted from different angles. To explain the variation laws of these seven kinds of parameters, we analyzed the relevant physical mechanism by considering the microphysical process of PD formation and development as well as the distortion effect generated by the space charges on the initial field. The relevant physical mechanism effectively allocated PD severity among these features for assessment, and the effectiveness and reliability of using these features to assess PD severity were proved by testing a large number of PD samples.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.240-242
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• 2005

It is well known that the PD (Partial Discharge) signals are generated if insulators have some defects such as voids in electrical facility and various PD detection methods are developed for preventing electrical troubles. So, an interest for the PD signals is higher and higher according to the high concern for the defects detection method of the aging electrical facility. When the equipment to detect PD signals installed at site and it works, a lot of noises flow in the equipment from surrounding situation and it will be mixed with original PD waveform. So we can not get the desired PD waveform. Therefore, there are many trial to reject or suppress the noise from the PD signals from long times ago. The greater of them used the hardware such as bridge circuits and frequency filters to suppress the noise. This paper proposed a novel noise rejection method in acquired data from PD detection equipment. The noise has the irregular phase and higher signal level than real PD, and noise decision is performed after inspection of pulse distribution in ${\Phi}$-q-n graph of acquired data from PD detection equipments. By experimental results on high voltage electric equipments, it is shown that proposed method has good performance. It is expected that this noise rejection technology is useful in numeric calculation and trend management of PD level.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1828-1830
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• 2003

Partial discharge(PD) tests are used to evaluate the insulation condition of stator windings in two 4.16kV and three 6.6kV motors. These tests were conducted using a conventional partial discharge detector(PDD) and turbine generator analyzer(TGA). Off-line PD measurements were performed on five high voltage motors. PD magnitudes ranged from 1000 pC to 5400 pC at the normal line-to-ground voltage. Five high voltage motors have been equipped with 80pF epoxy-mica coupler on the motor terminal box. The PD pulse from sensors were measured with the TGA instrument. TGA summarizes each plot with two Quantities such as the peak PD magnitude(Qm) and the total PD activity(NQN). The defect mechanisms of high voltage motor can be associated with PD patterns such as internal, slot and conductor surface discharges. The PDD and TGA test results of No. 4 motor showed that internal discharge was detected in voids of the groundwall insulation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.508-514
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• 2005

In this paper, it was investigated the characteristics of PD(partial discharge) pulse shapes in oil and the possibility of TF(Time-Frequency) analysis for the discrimination of air corona in on-site PD measurement of oil transformers. For the purpose, single and multiple discharges combined with oil discharges and air corona were generated and measured by use of artificial models through the HFPD pulse detector and the oscilloscope. PD pulse shapes were different according to the type of defects, especially including air corona- pulses. Also, through the TF analysis, data clusters could be classified each other in the TF Map, even in the case of multiple discharges. Therefore, it is known that TF analysis could be aprlied for the improvement of on-site PD measurement in oil transformers.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.975-979
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• 2001

In connection with the monitoring of the insulation degradation of large power apparatus in order to predict their expected service failures, a statistical treatment, such as phase resolved partial discharge analysis (PRPDA), has been established for the on-line monitoring system during the past decades. However, this method has shown some inconveniences to identify the nature of the PD source in power apparatus. In this regard, a novel approach based on the chaotic analysis (CAPD) is proposed describing the fundamental ideas, outcomes and different viewpoints from the conventional PRPDA. As a model for the possible defects causing sudden failures in service, three types of specimen are prepared. And partial discharge signals, originated from those samples, are measured and analyzed by means of CAPD. Throughout this work, it seems that the correlation between the consecutive PD pulses, depending on the nature of PD, could be clarified by CAPD. Thereffre, it could be considered that the nature of PD source can be identified more distinctively when the CAPD is combined with PRPDA.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.922-924
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• 1998

In this paper, an optical fiber sensor(OF sensor) utilizing the principal of Mach-Zehnder interferometer were proposed to detect the partial discharge signals in insulating oil. At first the AC breakdown signals were detected to check the response of the OF sensor. The detected signals from OF sensor was consistent with that from current probe. After the response checking, simultaneous measurements and continuous recording were made of electrical and the OF sensor signals from partial discharge(PD) produced by IEC(b) electrode system immersed in insulating oil. The continuous recording made it possible to extract basic quantities of PD from the OF sensor signals, such as pulse phase and pulse amplitude distribution. Through the signal analysis, the absolute peaks of the OF sensor PD signal was found to be increased with the amplitude of electrical signals, and these results mean that there is a strong correlation between OF sensor and electrical PD signals. It was demonstrated that the OF sensor in this research had a possibility to detect the PD signals in power apparatus.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.11
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• pp.616-621
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• 2000

This paper deals with the multiresolution analysis of wavelet transform for partial discharge(PD). Test arrangement is based on the needle-plane electrode system and applied AC high voltage. The measured PD signal was decomposed into "approximations" and "details". The approximation are the high scale, low-frequency components of the PD signal. The details are the low-scale, high frequency components. The decomposition process are iterated to 3 level, with successive approximation being decomposed in turn, so that PD signal is broken down into many lower-resolution components. Through the procedure of signal wavelet transform, signal noise extraction and signal reconstruction, the signal is analyzed to determine the magnitude of PD.