In this paper the modeling of interrupting characteristics of a high voltage current limiting fuse to be used in a power distribution system is introduced. In order to reduce the level of energy which can be absorbed by equipment during fault current flow, a high voltage current limiting fuse can generate a high voltage at the fuse terminals. Consequently it is necessary to model and analyze precisely the voltage and current variation during a CL fuse action. The characteristics of CL fuse operation modeled by electrical components have been performed with less than 6 [$\%$] errors. So the fuse designer or manufacturer can estimate the characteristics of CL fuse operation by using this modeling. The Electro Magnetic Transient Program (EMTP) is used to develop the modeling.

The ($Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films are deposited on Pt-coated electrode (Pt/TiN/SiO$_{2}$Si) using RF sputtering method with substitutional contents of Ca. The optimum conditions of RF power and Ar/O$_{2}$ ratio were 140(W) and 80/20, respectively. Deposition rate of SCT thin film was about $18.75{\AA}$/min. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over $15[mol\%]$. The capacitance characteristics had a stable value within $\pm4[\%]$ in temperature ranges of $-80\~+90[^{\circ}C]$. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

Precise measurement of extremely low resistance shunt is important for characterization and calibration of high current instruments. We tested resistance measurement method for extremely high current shunt (up to 140 kA), where resistance is determined by precise measurement of voltage drop at 10 A test current in the frequency range of 40 Hz to 10 kHz. For the extremely low ac voltage to be precisely measured, a verification of the measurement method was also carried, where the inherent noise is systematically evaluated. The measurement uncertainty was estimated to be $1\;\%\;at\;95\;\%$ confidence level (k=2) for about 50 $\mu\Omega$.

The optical current transformer was developed for 170 kV GIS using optical fiber. The sensor optimized on the optical CT was wound 3 turns and twisted 4 times per a turn at the pipe with a diameter of 130 m. To optimize the optical CT, the output signal was measured according to the setting angle of polarizer and analyzer, The asymmetry and distortion of the output signals were improved when the parallel polarized light was incident to the fiber sensor and under the angle of analyzer was $45^{o}$. The measurement error for the linearity was only $\pm{0.42}\;\%$ to 1,000 A in the case of reflection type.

A method for partial discharge diagnosis based on UHF narrow band type for GIS has been developed and calibrated. In generally, PD cannot be directly measured under on-line condition, but we can indirectly measure the electromagnetic wave made by PD using the high-frequency antenna. Compared with VHF band, electromagnetic waves of UHF band have a low influence for external noise in high-voltage substation. Therefore, we can detect the real abnormality with several pC in GIS using UHF narrow-band type method. For the case of no internal VHF sensor for GIS of the domestic substation, it has applied to use the external UHF sensor attached in spacer in GIS of existing substation. In this paper, we firstly described the technique of partial discharge measurement using frequency analysis and phase analysis in UHF band. Secondly, we presented the results of sensitivity test, the relationship of dBm-pC and diagnosis result of the cause of PD source by phase analysis. And then, we report the diagnosis result of partial discharge on the real GIS in domestic substation. These results make above method applicable for measurement of quantity and cause of PD for real operation GIS in high-voltage substation.

A wire-plate discharge system with a slit barrier has been proposed and investigated experimentally by focusing on the discharges on the slit barrier and ozone generation characteristics. This wire-plate discharge system with a slit barrier can generate an intensive corona discharges, and produce corona discharge twice, once from the corona wire electrode and second time from the surface and the slits of the slit dielectric barrier. As a result this propose wire-plate discharge system with the slit barrier can produce greatly increased ozone than without the slit barrier. This type of wire-plate discharge system with the slit barrier could be used for effective ozone generation as a means with retard to the removal of pollutant gas

Ion migration characteristics of a rotary spark airgap of high voltage Pulse generator had been investigated. It was considered that the ion migration speed and the ions of the gases(atmosphere gases, $O_2,\;N_2,,\;and\;H_{2}O,\;etc$.) and the charged very fine particles(about $10\~100nm$ size) migrated through the upper stator ball and bottom stator ball of the rotary spark airgap would determined the rise and fall times of the output high voltage pulse. In this paper, a basic study on the ion migration characteristics of the rotary spark airgap between the spark stator ball and the ion-sensing electrode of the proposed high voltage pulse generator have been investigated experimentally. As a result, the three kinds of ion speeds were detected by the ion-sensing electrode installed at the position of the bottom stator ball of the ball type sparkgap high voltage pulse generator. The migration velocities, diameters, masses, charges, numbers of the ions and particles were obtained by experiments and calculations, which, however, would determine the rise and fall times of the output high voltage pulse.