• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2093-2096
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• 1999

This paper describes to access the insulation deterioration condition of the stator windings in three large turbine generators. Nondestructive tests have been carried out on stand-still generators which have been in service for 2 to 30 years. In most cases these tests include ac current increase rate($\Delta$I), delta tan delta( ${\Delta}tan{\delta}$), and maximum partial discharge(Qm). Gen. 2 show that the $tan{\delta}$ is higher than other two generators in the $tan{\delta}$-voltage curve. Partial discharge(PD) patterns were observed internal, corona and treeing discharges in large turbine generators. The PD tests were confirmed the correlation between discharge patterns and the kinds of defects.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2392-2395
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• 1999

This paper describes to access the insulation deterioration condition of the stator windings in six high voltage motors. Nondestructive tests have been carried out on stand-still motors. These tests include ac current increase rate($\Delta$I), delta tan delta(${\Delta}tan{\delta}$), and maximum partial discharge(PD). AC current and $tan{\delta}$ were measured by Schering bridge. The measurement of PD patterns were conducted using digital partial discharge detector. PD patterns were observed treeing and internal discharges in Motor 1 and 2. The stator windings of two motors were found to be in a poor condition and their were recommended to rewind. The stator. windings of four motors were judged to be in serviceable condition.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1688-1691
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• 1997

In this work, we have developed the off-line diagnostic system for power cable insulation using DC voltage decay method to diagnose the insulation degradation of underground power cables. Measurement errors of diagnostic system are less than 1% for $1T{\Omega}$ internal resistor. We have also developed measurement and diagnostic programs for win95 which is suitable for the database construction and the management of data. We could conclude that it is possible to apply this system to the multi-grounded underground cable systems.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.223-227
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• 2005

Insulation failure of traction motor stator coil depends on the continuous stress imposed on it and knowing its insulation condition is an issue of significance for proper safety operation. In this paper, application of the NN (Neural Network) as a scheme of the off-line PD (partial discharge) diagnosis method that occurs at the stator coil of a traction motor was studied. For PD data acquisition, three defective models were made; internal void discharge model, slot discharge model and surface discharge model. PD data for recognition were acquired from a PD detector. Statistical distributions and parameters were calculated to perform recognition between model discharge sources. These statistical distribution parameters are applied to classify PD sources by the NN with a good recognition rate on the discharge sources.

• Proceedings of the KIEE Conference
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• 2005.07c
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.500-501
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• 2007

The method of maintenance in railway is going to be changed to improve reliability on traction equipment. Partial discharge (PD) tests are useful to evaluate the insulation condition of stator winding. This paper describes the use of PD tests with 5 model coils which have the defects such as internal, slot discharge. The PD tests are performed with epoxy-mica coupler 500 pF at various AC voltages. The result of test shows PD pattern can correlate with the species of defects on 5 model coils.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1387-1388
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• 2007

Solid insulation exposed to voltage is degraded by electrical tree process. And the degradation of the insulation is accelerated by voltage application. For this experiment, specimens of electrical tree models were made by three types of XLPE (cross-linked polyethylene). And distribution characteristics of degraded stages are studied too. As a method of detecting and data process, discharge data was acquired from PD detecting system (Biddle instrument). And microscope and digital camera were used to observe the morphologies of the electrical tree to divide stages of the tree. The system presents statistical distribution as phase resolved. Moreover the processing time of electrical tree is recorded to know the speed of degradation according to voltage.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.139-144
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• 2008

Micro electrochemical machining was investigated to machine micro internal features. This method uses a micro disk tool electrode and can easily machine micro features inside of a micro hole, which are very difficult to make by the conventional processes. In order to limit the machining area and localize the electrochemical dissolution, ultra short pulses were used as power source and a micro disk electrode with insulating layer on its surface was used as a tool electrode. By electrochemical process, internal features, such as groove array, were fabricated on the stainless steel plate.

• Journal of the Korean housing association
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• v.12 no.3
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• pp.133-140
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• 2001

This study investigated the heat transmission coefficient through the experiment that the skylight, slope window of 60 degree and 30 degree consisted of pair glass and the double window of external window and internal window paper were suitable for heat insulation. As the result of experiment, the heat transmission coefficient of slope window was 1.06 times in the 60 degree, 1.18 times in the 30 degree and 1.31 times in the skylight as a standard lateral window. The heat transmission coefficient in the double window of external window and internal window paper was 3.017$\textrm{㎉}$/$\textrm{m}^2$.hr.$^{\cire}C$. The slope window was not suitable for the prescription by the increase of the heat transmission coefficient, so the user must pay attention to the treatment. This study investigated only the slope window of 12mm and 16mm pair glass and the double window of external window and internal window paper, study on the various pattern of window must be achived in a future.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.5
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• pp.1-12
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• 2012

In order to reduce energy consumption and greenhouse gas emission in building domain, thermal insulation of building is being enhanced. In a well insulated and tightened environment, internal heat gain caused by solar radiation, luminaires, electronic appliances and metabolism can be more important to thermal condition of building. This paper presents mathematical/physical models of quasi-adiabtic room and lighting fixtures using heat balance equation and thermal-electric analogy to quantify and modelize the heat gain due to luminaires. Experimental results are used to identify thermal parameters of theoretical models. And simulation results of models using Matlab/Simulink are conducted to verify the models and to investigate the thermal effect of lighting fixtures into quasi-adiabatic room.