A uniform plasma-based ion implantation and DLC film formation technologies on the surface of complicated 3-dimensional substrates have been developed by applying pulse voltage coupled with RF voltage to the substrates such as plastics, rubber as well as metals with the similar deposition rate. These technologies are widely applicable to both ion implantation and DLC film formation onto the automobile parts, mechanical parts and metal molds. A problem to be solved is reducing cost. The deposition rate of DLC films is expected to increase to around 10μm/hr, which is ten times larger than that of the conventional method, by hybridizing the ICP (Induction Coupling Plasma) with a plus-minus voltage source. This epoch-making technology will be able to substitute for the electro-plating method in the near future. In this paper, the DLC film formation technology by applying both RF and pulse voltage, its applications and its prospect are presented.
A partial discharge (PD) detector for cables in service has been developed. It consists of a signal processor put into an attaché case with CT for PD pulse sensing, and a personal computer. This PD measurement system is usable for cables in service because its CT can be split open and clamped a earth line of existing facilities. This paper describes analysis methods of PD pulses on high voltage power cables, the outline of PD measurement system, and some acquisitions of PD pulses in live lines.
Dispersed generation technologies (e.g. Gas-engines) have greatly advanced in recent years. Gas engines are often operated as the main component of a cogeneration system (CGS). By using exhaust heat, the total efficiency of CGSs can reach from 70% to 80%, and as a result, it is also useful for reductions of CO2 emission. Therefore CGSs have been given preferential treatment by the Japanese government and their installation and use is expected to become widespread in the future. As a demand response program, the authors proposed a method whereby CGSs at the customer-side are used for congestion relief in transmission networks. In the proposed method, the optimal configuration of energy systems including CGSs at the customer-side is determined. As well, the optimal operation of the electric utility's generators is also determined taking into account the CGS operation patterns. This paper evaluates both costs to the electric utility and the customers' cost for congestion relief in transmission networks. Further, we evaluate the influence on CO2 emission and primary energy consumption from the view point of a unified energy system with CGSs providing input on a flexible operation pattern.
The load stability in bulk power system may be seriously affected when a large amount of distributed generators (DG) stop simultaneously due to voltage sag. It is important to understand the mechanism of load instability, which cannot be analyzed by well-known P-V curve only. For analyzing load stability without detailed simulations, this paper presents torque-speed characteristic curves of induction motor considering power system condition and constant impedance loads. As the results of examining the curves in various conditions (model order reduction methods, load dropping out), this paper also presents some cautions for bulk power system modeling with DG. A bulk power system model whose lower voltage subsystems are reduced by an accurate model order reduction method is introduced in order to check out the problems by DG-stopping. As to the numerical simulation, a great number of DG-stopping leads to voltage instability in bulk power system, and the instability is greatly improved by DG-voltage regulation.
This paper describes a method for deriving a transmission tower model for EMTP lightning overvoltage studies from a numerical electromagnetic simulation result obtained by the FDTD (Finite Difference Time Domain) method. The FDTD simulation carried out in this paper takes into account the following items which have been ignored or over-simplified in previously-presented simulations: (i) resistivity of the ground soil; (ii) arms, major slant elements, and foundations of the tower; (iii) development speed of the lightning return stroke. For validation purpose a pulse test of a 500-kV transmission tower is simulated, and a comparison with the measured result shows that the present FDTD simulation gives a sufficiently accurate result. Using this validated FDTD-based simulation method the insulator-string voltages of a tower for a lightning stroke are calculated, and based on the simulation result the parameter values of the proposed tower model for EMTP studies are determined in a systematic way. Since previously-presented models include trial-and-error process in the parameter determination, it can be said that the proposed model is more general in this regard. As an illustrative example, the 500-kV transmission tower mentioned above is modeled, and it is shown that the derived model closely reproduces the FDTD simulation result.
We investigated propagation properties of Lamb waves in gas insulated switchgear (GIS) tank to diagnose insulation performance of GIS. The acoustic signals excited by a free metallic particle colliding with the tank sheath were measured using AE sensors. The Wavelet Transform was applied to decompose the wave data into its time-frequency components. As the result, difference of propagation properties of Lamb waves is clearly seen on different size of GIS tank. Based on the characteristics of Lamb waves, algorithms for location identification of a free metallic particle were examined in model GIS using two AE sensors. As the result, we propose a new system for location identification of a free metallic particle in GIS. Moreover, it is verified that the new identification system is suitable to diagnostic technique for GIS.
A new type of vacuum circuit breaker (VCB) has been developed, which needs a minimum of maintenance. This VCB is characterized by the following: (a) a significantly simplified driving mechanism, (b) no need for grease, and (c) a new electromagnetic actuator called a hybrid-type electromagnet. The number of movable parts is decreased to 15% of that of our conventional product with a spring drive. Solid lubricant is adopted instead of grease for almost all of the linkages, which helps to eliminate periodical lubricating maintenance. The hybrid-type electromagnet has an attractive force suitable for the spring force characteristics of the VCB through its combination of conventional plunger-type and plate-armature-type electromagnet. The VCB is held in the closed position by the attractive force of the permanent magnet without using a coil current. Its core structure is optimized to prevent the permanent magnet from demagnetization and to secure long-term reliability. To assess the solid lubricant reliability, some special tests were performed such as a rare operation test. Dynamic characteristics were measured for three specimens at intervals of a month, a year, and two years, respectively. It was confirmed that variation of the armature speed is small and the influence of the non-operation interval is negligible.
The national standard class divider for the lightning impulse voltage measurements in Japan was developed in 1998. After three years, the standard impulse voltage calibrator was manufactured, too. These standard equipment are used as an industrial standard, and the performance had been evaluated annually supported by Ministry of Economy, Trade and Industry (METI). The standard impulse measuring system including the standard divider participated in the worldwide comparison test and its good performance was confirmed in 1999. Another international comparison test was carried out among three countries in the Asia-Pacific region in 2004 again and the standard measuring system participated in the test. In this paper, the details and the results of the international comparison tests in 2004 are described.
Effect of humidity on flashover voltage of three kinds of insulators is experimentally studied for about three years under natural humidity condition. It is found that the existing IEC humidity correction seems to be proper for most insulators regardless of the kinds of applied voltage but that change may be necessary for a cap and pin insulator unit under the application of positive and negative lightning impulse voltages.
Proton exchange membrane fuel cells (PEMFC) are one of the most promising technologies for use as power sources for fuel cell vehicles and residential power applications. However, it is recognized that durability is critical issues for commercialization. Generally, PEMFC for automobile use are exposed to low relative humidity and load cycle condition that cause significant degradation of membrane and catalyst. The focus of this research is to investigate the influence of the load cycle pattern on the cell degradation. Single cell tests were performed for several load cycles and the degradation of the cell performances were evaluated by monitoring of the cell voltage, internal resistance, gas crossover rate and ionic content in effluent. Also, in order to investigate the gas diffusion layer (GDL) and the membrane/ionomer degradation, contact angle measurement were made for the GDL and solid 19F-NMR measurement were conducted as the post analyses. In the load cycle conditions, the activation and diffusion polarization are remarkably increased during the test, and inadequate water content accelerates membrane/ionomer chemical degradation.
It is important for electric power companies to maintain grounding resistances adequately for the safety of the public. But they have difficulty in managing those grounding systems because vast amounts of grounding electrodes are installed in distribution lines. Based on the statistical data of surge currents through lightning arrestors and electrical surges in customers, a rated value of the grounding resistance for lightning arrestors on distribution lines was specified in the 1960's. TEPCO had conducted field research to measure the waveforms of surge voltage and current in order to rationalize the lightning protection design of distribution lines. And the authors proposed a lightning-surges analysis model based on the observation data. In this study, a lightning surge analysis for the rationalization of the grounding system was carried out by means of the EMTP. The calculated results suggest that a practical grounding design is possible. That can be useful for the Electric Power Companies to manage grounding systems.
The grounding system is one of the most important lightning-protection features of power distribution lines. Based on the statistical distribution of surge currents through lightning arrestors caused by indirect lightning strokes and electrical surges in customers, a rated value of the grounding resistance for lightning arrestors on distribution lines was specified in the 1960's. TEPCO had conducted field research to measure the waveforms of surge voltage and current in order to rationalize the lightning protection design of distribution lines. And the authors proposed a lightning-surges analysis model based on the observation data. In this study, a lightning surge analysis for the rationalization of the grounding system was carried out by means of the EMTP. The calculation conditions were set based on the observation data. The calculated results suggest that a simple grounding design is possible. That can be useful for the Electric Power Companies to manage grounding systems.