Won-Zoo Park

Surface Discharge Characteristics Study on the Laminated Solid Insulator in Quasi-Uniform Electric Field with Dry Air

Dry air is an excellent alternative to SF6 gas and is used as an insulation gas in Eco- friendly Gas Insulated Switchgears (EGISs), which has gained popularity in industry. Solid insulators in EGIS play an important role in electrical insulation. On the other hand, surface discharge can occur easily when solid insulators are used. This paper explored the surface discharge characteristics on the structure of three-layered laminated solid insulators to elevate the flashover voltage. A laminated solid insulator was inserted after the quasi-uniform electric field was formed in the test chamber. Dry air was then injected to set the internal pressure to 1 ~ 6 atm, and the AC voltage was applied. When identical solid insulators were stacked, the surface discharge characteristics were similar to those of a single solid insulator. On the other hand, the flashover voltage rose when the middle part was thicker and had lower permittivity than the top and bottom parts in the laminated solid insulator. Based on experimental results, when stacking a solid insulator in three layers, the middle part of the solid insulator should be at least four times as thick as the top and bottom parts and have lower permittivity than the others. In addition, the flashover voltage increased with increasing gas pressure on the surface of the laminated solid insulator due to the gas effect. This study may allow insulation design engineers to have useful information when using dry air for the insulation gas where the surface discharge can occur.

Characteristics of Optical Current Sensors by Sensor Design

This paper will suggest that the 1 cross orthogonal loop type sensor improves on the orthogonal loop form sensor-head, which is available a calibration of the linear birefringence, when a fiber optic current sensor was composed, An output characteristics of the 1 cross orthogonal loop form, a general closed loop form, the orthogonal loop form are compared by the IEC(International Electrotechnical Commission) 60044-8 standard, and the state of polarization is compared with three forms. As a result, when the closed loop form was changed to the orthogonal loop form, retardation decreased 15.3[%]. When the closed loop form was changed to the 1 cross orthogonal loop type, the retardation decreased 33.8[%]. As a result of the Faraday Effect measurement, the 1 cross orthogonal loop form has the highest output characteristic and the lowest error ratio. It met the 0.5 class of the IEC 60044-8 standard. Thus, in application of the lcross orthogonal loop form, the possibility to develop high reliability fiber optic current sensors that have a high output and stable error ratio rises is increased.

A Study of the Real-time Sensing by the Optical Current Sensor for GIS

In this study, a Web server was constructed using LabVIEWs DataSocket, which makes possible acquisition, analysis, and saving in real time. The output value of the optical current sensor at the web server PC was measured and the output value was displayed using the Web browser of the client PC. DataSocket by LabVIEW makes the construction of a Web server easier than other languages and is compatible with other application programs. An optical current sensor was composed using a 1310 [㎚] laser diode, and 9/125 [?] standard single mode optical fiber and was created to be a close type sensor. Data measurement using Web servers has the advantage of monitoring electric power systems at a great distance and can fuse IT technology and electric power systems. Also, this measurement uses inexpensive mounting and programming when compared to existing measurement equipment allowing the construction of a measurement system in any situation or surrounding.

Breakdown characteristics of SF₆ and Imitation Air in Temperature Decline

This paper describes experiments of the breakdown characteristics by temperature change of SF? gas and Imitation Air(I-Air) in model GIS(Gas Insulated Switchgear). From the results of the experiments, the breakdown characteristics classify the vapor stage of SF? according to Paschens law, in which the stage of coexistence for gas & liquid of the voltage value increases. This results in large deviation and the breakdown of the voltage(VB) low stage as the interior of the chamber is filled with a mixture of SF? that is not liquefacted and remaining air that can not be ventilated. The ability of SF? liquid(LSF?) insulation is higher than high-pressurize SF? gas. The VB of the I-Air decreases as the temperature drops and the VB also drops. It is considered that the results of this paper are fundamental data for the electric insulation design of superconductor and cryogenic equipment that will be studied and developed in the future.

A Comparison of Signal Processing Techniques in Optical Current Sensor for GIS

This research is contents about output characteristic of optic current sensor that use faraday effect. optic current sensor used in an experiment is consisted of three parts.① Source of light used laser diode of 1310 [㎚].② Sensor section manufactured circularly according to gas insulated switchgear. And 9/125[ ㎛ ] standard single mode optical fiber for communication was installed winding 20 [turn] on sensor section core surroundings of diameter 31 [㎝]. ③ Electrical signal of PD(Photo detector) is collected using NI companys 16bit DAQ board via terminal block. Collected data analyzed by different three signal processing methods. NI companys LabviewTM was used to signal processing software. As a result, In signal processing of optic current sensor, we could know that noise greatly more influences the error generation than fluctuation of light intensity. also, 1 class CT(current transformer) manufacture that have error rate less than 1[%] was available by removing these

A Study of Surface Discharge Characteristics for Dew-Point of Dry-Air and Materials or Shapes of Solid Insulator in Quasi-Uniform Field

This study investigates the surface discharge characteristics of solid insulators by varying their materials, their shapes, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polycarbonate, and bakelite. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polycarbonate is higher than that of bakelite. Moreover, it is observed that the flashover voltage increases as the diameter and the thickness of each solid insulator become larger and thicker, respectively. However, the thickness of the solid insulators is more critical for increasing the flashover voltage than their diameter.

The Characteristics of the Ozonizer with Cascade-Type Plate Electrode

Recently, ozone has been utilized in various fields thanks to its effectiveness, and has been in ever-growing demand. Accordingly, various kinds of ozonizers have been examined among researchers. This paper is concerned with developing the cascade-type plate electrode ozonizer(PTO) for improvements of indoor air, water supply and drainage and investigating its characteristics. Four types of ozonizers have been devised according to their size, numbers and arrangement Electric discharge area of each type of ozonizer has the same size of 22,400[], and its discharge power has the maximum 40[w]. As the result of having studied ozone generation ozone concentration and ozone yield characteristics of each ozonizer, we found that the type of ozonizer in which eight plates were arranged into cascade type(PTO-4) was the most excellent one.

A Study on Characteristics of Insulation Breakdown and Surface Discharge by the Mixing Ratio of Dry Air/O 2 gas mixtures

This paper presents the discharge characteristics and economic feasibility of a Dry and a mixture gas in order to review alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry and the mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry and the mixture gas were discussed so that Dry mixture gaswas more suitable than mixture gas to the alternative.

A Study on the Surface Discharge Characteristics by Dielectric Constant and Diameter of Solid Dielectrics to Improve Surface Dielectric Strength in Eco-Friendly Insulation Gas

This paper studied surface discharge characteristics by a dielectric constant and diameter of solid dielectrics in mixture gas. Applied electric field strength at mixture gas was changed from the dielectric constant and diameter of the solid dielectrics, and insulation performance of the mixture gas determined surface discharge voltage. In each of the diameter at the solid dielectrics, the surface discharge voltage was increased by lengthening surface distance, whereas increasing rate of the surface discharge voltage was different from gas pressure. Thus, In this paper, main factors of surface discharge are as follows. 1) Insulation performance of mixture gas, 2) Dielectric constant of solid dielectrics, 3) Surface discharge path. It was clear that the surface discharge voltage depend on the main factors. These results will be applied to useful data for an eco-friendly composite insulation design.

Shielding effectiveness through narrow slots in dual conducting screens

This paper presents the electric shielding effectiveness (SE) of a dual metallic wall with narrow slots when the plane wave is incident. In the analysis, integral equations for aperture electric fields on slots are derived and solved by applying Galerkin’s method of moments (MoM). The numerical results show that plane-wave SE depends on both slot lengths and plate spacing for a given frequency. Plane wave SE fluctuates with the spacing of the plate, and the fluctuation period is about 0.5λ. A high level of electric SE can be obtained for small slots and low frequencies. Also obtained is the electric SE below 0 dB when the plate spacings are smaller than 0.1λ. Experimental measurements are also presented to validate the theory.