• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.5
• /
• pp.629-635
• /
• 2014

This paper describes propagation characteristics obtained by considering semiconducting screen and cross-bonding in underground transmission cables. The semiconducting screen of power cable has effect on propagation characteristics including attenuation, velocity and surge impedance. However, it is very difficult to apply the semiconduction screen for EMTP model because of the number of conductors limitation. Therefore, CIGRE WG 21-05 proposed advanced insulation structure and analysis technique of simplified approach including inner and outer semiconducting screen. In this paper, the various propagation characteristics analyse using this structure and technique for 154kV XLPE $2000mm^2$ cable. The frequency independent model of EMTP CABLE PARAMETER is used for just pattern analysis of propagation characteristics. For exact data analysis, the frequency dependent model of J-marti is used for EMTP modeling. From these result, various propagation characteristics of 154kV XLPE $2000mm^2$ cable according to semi conducting screen consideration, frequency range, cable length and pulse width are analysed. In addition, in this paper, the effects of cross-bonding are also variously discussed according to cross-bonding methods, direct connection and impedance of lead cable.

• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1845-1848
• /
• 2003

PD(Partial Discharge) signal have the range from several kHz to several GHz. External noises don't give any interference to discerning PD signals with high frequency bandwidth between several hundreds MHz to several GHz but, in the range between several decades kHz to several MHz, are big obstacles to prevent from discriminating PD signals. Therefore, selecting appropriate filter to decrease the influence of noise is important problem. PD signals have the characteristics both short duration and non-continuous pulse train. For separating PD signals from External noises, some different filtering methods different from conventional ones are needed and wavelet filtering method was convinced to be suitable filtering method in various investigations. This paper has simulated PD signal and various noises and investigated the influences for the performance of wavelet filter by varying the components relative to designing of wavelet filter and constructed suitable one. For the purpose of convincing the performance of wavelet filter, real PDs were produced in needle to plane electrode structure. This small PD signal was mixed with external noises and filtered with wavelet filter. We have obtained apparent PD signals and noises are well suppressed by wavelet filter.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.10a
• /
• pp.570-573
• /
• 2022

This paper presents the identification of void diameters for a cast-resin transformer using an artificial neural network (ANN) model. A PD signal was measured by the Rogowski coil sensor which has the planar and thin structures fabricated on a printed circuit board (PCB), and the PD electrode system was fabricated to simulate a PD defect by a void. In addition, void samples with different diameters were fabricated by injecting air in a cylindrical aluminum frame using a syringe during the epoxy curing process. To identify the diameter of void defects, PD characteristics such as the discharge magnitude, pulse count, and phase angle were extracted and back propagation algorithm (BPA) was designed using virtual instrument (VI) based on the Labview program. From the experimental results, the BPA algorithm proposed in this paper has over 90% accurate rate to identify the diameter of void defects and is expected to use reference data of maintenance and replacement of insulation for cast-resin transformers in the on-site PD measurement.

• Journal of the Korean Society for Railway
• /
• v.20 no.2
• /
• pp.203-209
• /
• 2017

Research on condition monitoring and diagnosis of power facilities has been conducted to improve the safety and reliability of electric power supply. Although insulation diagnostic techniques for unit equipment such as gas-insulated switchgears and transformers have been developed rapidly, studies on monitoring of cables have only included aspects such as whether defects exist and partial discharge (PD) detection; other characteristics and features have not been discussed. Therefore, this paper dealt with PD characteristics against void sizes and positions, and with defect localization in XLPE cable. Four types of defects with different sizes and positions were simulated and PD pulses were detected using a high frequency current transformer (HFCT) with a frequency range of 150kHz~30MHz. The results showed that the apparent charge increased when the defect was adjacent to the conductor; the pulse count in the negative half of the applied voltage was about 20% higher than that in the positive half. In addition, the defect location was calculated by time-domain reflectometry (TDR) method, it was revealed that the defect could be localized with an error of less than1m in a 50m cable.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.09a
• /
• pp.60-66
• /
• 2001

Because of internal voids in insulators give rise to partial discharge(PD), which cause local breakdown and even entire insulation breakdown. Treeing due to PD is one of the main causes of breakdown of the insulating materials and reduction of the insulation life. Therefore the necessity for establishing a method to diagnose the aging of insulation materials and to predict the breakdown of insulation has become important. From this viewpoint, our studies diagnose insulation degradation using the method of computer sensing system, which has the advantages of PD and acoustic emission(AE) sensing system. To use advantages of these two methods can be used effectively to search for treeing location and PD in some materials. In analysis method of degradation, We analyzed the PD pulse and AE pulses by regression analysis, compared to these obtained the correlation coefficient and determination coefficient by T-distribution and saw that PD and AE pulses show a similar pattern on the whole. This is in agreement with the results of the research by Yoshimura and Fujita.