• Korean Journal of Clinical Laboratory Science
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• v.37 no.3
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• pp.220-227
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• 2005

Recently, the use of an electrical apparatus has brought up concerns of health risks from exposure to electromagnetic fields. EMF is composed of electric fields and magnetic fields. Heavy exposure to EMF can occur only in the vicinity of high-voltage overhead transmission lines, close to transformers and underground cables, and also close to large electrical machinery. In this thesis I have investigated the hypothesis of the correlation between occupational exposure to ELF-EMF and the risks of leukemia, anemia, cancer. Therefore, the aim of this study is to investigate whether or not ELF-EMF emitted from electric power stations and transformer substations affect some hematological parameters and tumor markers of electric utility workers. The hematological test results and tumor markers under investigation were similar in the two groups but some of parameters such as RBC, AFP, LDH showed significant difference between the two groups from two sample t-test (p<0.05). The exposure group showed increased LDH level compared to the control group by two sample t-tests. In addition, the abnormal LDH level in the exposure group was observed to be clinically significant by ${\chi}^2$-test. However, the levels of RBC, AFP observed were not clinically significant by ${\chi}^2$-test (p>0.05). These results suggested that ELF-EMF does not affect most blood test parameters except LDH of electric utility workers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.66-73
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• 2002

This paper presents ZVZCS(Zero-Voltage and Zero-Current Switching) Three Level DC/DC Converter without primary freewheeling diodes. The new converter presented in this paper used a phase shirt control with a flying capacitor in the primary side to achieve ZVS for the outer switches. A secondary anxiliary circuit which consists of one small capacitor, two small diodes and one coupled inductor, is added in the secondary to provide ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages include simple secondary auxiliary circuit topology, high efficiency, and low cost make the new converter attractive for high power applications. Also the circulating current flows through the circuit so that it causes the needless coduction loss to be occurred in the devices and the transformer of the circuit The new converter has no primary auxiliary diodes for freewheeling current. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1[㎾］ 50[KHz］IGBT based experimental circuit.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.203-209
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• 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 IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.29-33
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• 2004

In this paper, we took the basic experiment in order to explore the characteristics of optical CT(optical current transformer) for measuring high current in a superhigh voltage condition using faraday effect and wrote that. We used the 1,310[nm] Laser Diode for the source of light and PIN-Photodiode for receiver. The transmission line of light was composed of the single-mode fiber of 30[m] which could maintain the state of polarization in the optical fiber. The range of current was from 400[A] to 1300[A]. In addition, the temperature ranged from $20[^{\circ}C}]\;to\;50[^{\circ}C]$. In a same experiment condition, a power magnitude increases in proportion as input current is increasing and temperature become low. The maximum ratio of error in temperature of $50[^{\circ}C]$ appears 0.15[%] and the 0.16[%], 1.24[%] and 0.07[%] is ratio of error in respectively $40[^{\circ}C],\;30[^{\circ}C],\;and\;20[^{\circ}C]$.