• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권4호
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• pp.247-252
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• 1999

In this paper, in order to investigate availability of the OW-PD measurement method which has been proposed as an alternative of AC-PD measurement method to an after laying test and/or diagnosis for the power cable system, partial discharges owing to the needle-type defect integrated into the cable have been measured using AC and OW(Oscillating Wave) voltages. In the AC-PD measurement, the magnitude, phase and pulse number of partial discharges have been changed with the duration of voltage application, which can be analyzed through the relation with the process of the electrical tree initiation and propagation. In addition, the characteristics of partial discharges using OW voltage are appeared to be similar to those in case of AC-PD measurement and to be different with the shapes of electrical tree. From these results, it is concluded that the OW-PD measurement method is available to the tests for the cable system.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.178-182
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• 2006

Five model coils of 6.6 kV motor were manufactured with several defects. These stator coils have artificial defects such as void of groundwall insulation, removal of semi-conductive coating and damage of strand insulation. Epoxy-mica coupler(80 pF) was connected to five model coil terminals. The voltage applied to the coils was 3.81 kV, 4.76 kV, 6.0 kV and 6.6 kV, respectively. Partial discharge(PD) tests performed in the laboratory and shield room. Digital PD detector(PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in pC were measured with PDD. PD patterns of model coils were indicated the internal and slot discharges. PD patterns are consistent with the result of measurement using PDD and TGA instruments. AC breakdown test was performed on five model coils in order to confirm the result of PD measurements. All the failures were located in a line-end coil at the exit from the core slot.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1526-1529
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• 1994

In hydro-generator, a groundwall insulation of stator windings gradually deteriorates due to mechanical, thermal, electrical and environmental stresses. These stresses combine to result in loose windings, delamination of the stator insulation and/or electrical tracking of the end winding, all of which can lead to stator insulation failures. Conventionally, off-line tests such as partial discharge measurement, DC/AC current test and ${\Delta}tan{\delta}$ test has been used for estimation of winding condition. However, off-line test requires large power supply and generator outage. In addition, major cause of insulation problems such as loose wedges and slot discharges may not be found with off-line diagnoses. This paper describes the on-line partial discharge measurement techniques in the generator stator windings. The experimental results from the UIAM #1 hydro-generator confirms a optimistic application of on-line generator diagnosis method as a reliable tool for evaluation of winding condition.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.735-741
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• 1999

The monitoring and assessment on the insulation condition of generator stator windings have been an important task of utility companies. The interest for the assessment of insulation condition has been increasing due to the need to keep old generating equipment reliable in order to extend the equipment life and to increase the generating capacity. Even though many developments and research activities for the condition assessment of generator insulation have been performed for decades, the assessment criterion in order to consistently predict the actual insulation condition is still in question. In this paper, the correlation between the parameters and the insulation condition is analyzed through the various non-destructive diagnostic tests in order to establish the assessment criterion on insulation deterioration of generator stator windings. By analyzing the correlation, PDI(Partial Discharge Index) as a novel parameter for the assessment criterion on insulation diagnosis of stator winding is proposed and verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.244-247
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• 2004

The electrical insulating design is important to realize a HTS power cable because the cable is operated under the high voltage environment. For the insulation design of a HTS power cable, it is necessary to investigate the AC, impulse breakdown and partial discharge(PD) inception stress of liquid nitrogen/LPP composite insulation system. Based on these results, the electrical insulation of a HTS power cable is designed and Mini-model cables are manufactured. The manufactured Mini-model cables are evaluated that AC, impulse withstand voltage, breakdown and partial discharge inception stress and analyzed characteristics insulation of HTS cable bending condition according to this paper. From these tests, the AC, impulse withstand voltage test and partial discharge inception stress is satisfied "standard technical specification of KEPCO" in Korea and the breakdown voltage was 120kV.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.50-56
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• 1994

Partial discharge on organic insulation surfaces are an important sauce of aging. Furthermore the modern PD measurement technigues are rapid developed as quality control and diagnostic tests to determine the fitness for use of HV equipment employing sol id electrical insulation. This paper deals with theory of conventional PD measurement and new tendency of technical development on PD measurements und evaluations. Finally the Measuring system used for diagnosing the surface aging on the organic insulation at High Voltage Laboratory of Technical University of Darmstadt in Germany is presented.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
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• pp.87-90
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• 1992

Detecting acoustic emission (AE) provides an appropriate method to diagonize on-line transformers, since acoustic signal is not influenced by strong electric field. Then AE versus AE signal processing method is investigated. But this processing is difficult that decision of starting point of AE wave with acoustic noise. This problem is sloved by correlation which calculate time interval between two signals eactly. This paper presents a technique locating the eact position of the partial discharge (PD) in a power transformer by the correlation of the AE signals from two ultrasonic sensors. And PD position is displayed on monitor. Laboratory tests confirmed that the proposed method can be used for locating the PD in power transformer.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1765-1772
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• 2015

The integrity of the gas insulated switchgear (GIS) is vital to the safety of an entire power grid. However, there are some limitations on the techniques of detecting and diagnosing partial discharge (PD) induced by insulation defects in GIS. This paper proposes a joint electro-chemical detection method to resolve the problems of incomplete PD data source and also investigates a new unique fault diagnosis method to enhance the reliability of data processing. By employing ultra-high frequency method for online monitoring and the chemical method for detecting SF6 decomposition offline, the acquired data can form a more complete interpretation of PD signals. By utilizing DS evidence theory, the diagnostic results with tests on the four typical defects show the validity of the new fault diagnosis system. With higher accuracy and lower computation cost, the present research provides a promising way to make a more accurate decision in practical application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2091-2093
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• 2005

Five model coils of 6.6kV motor were manufactured with several defects. These stator coils have artificial defects such as void of groundwall insulation, removal of semi-conductive coating and damage of strand insulation. Epoxy-mica coupler(80 pF) was connected to five model coil terminals, respectively The voltage applied to the coils was 3.81kV, 4.76kV, 6.0kV and 6.6kV. Partial discharge(PD) tests performed in the laboratory and shield room. Digital PD detector (PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in pC were measured with PDD. PD patterns of model coils were indicated the internal and slot discharges. PD patterns coincide with both PDD and TGA.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2066-2068
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• 2005

We developed an on-line Ultra-high frequency partial discharge monitoring system to prevent a catastrophic failure of gas- insulated switchgears. The system has been tested in the laboratory for detection of various UHF PD signals. We also performed detection sensitivity verification tests and compared them with conventional IEC60270 method.