By specifically designating penetrations rates of advanced meters and communication technologies, devices and systems, this paper introduces that the penetration of advanced metering is important for the future development of electric power system infrastructure. It examines the state of the technology and the economical benefits of advanced metering. One result of the survey is that advanced metering currently has a penetration of about six percent of total installed electric meters in the United States. Applications to the infrastructure differ by type of organization. Being integrated with emerging communication technologies, smart meters enable several kinds of features such as, not only automatic meter reading but also distribution management control, outage management, remote switching, etc.
Voltage sags originated at the transmission level can have a very adverse effect on distributed generators running at distribution levels. A fault current limiter (FCL) can be an effective means to limit the voltage sag impact. This paper presents the main results of a research based on digital simulation and aimed at studying the effectiveness of a FCL to limit the impact of voltage sag on the shaft torque of distributed generators. The sensitivity of the shaft torque to parameters of the FCL, the power system and the fault is analyzed.
This paper presents a quantitative evaluation of CO2 emission from grid power systems and heat source systems including CHP (combined heat and power) in residential and commercial buildings in Japan. We estimated changes in CO2 emission from the utility grid and from CHP using an optimal generation planning model. Through quantitative simulation runs, the authors obtained the following results. First, introduction of CHP at a certain degree brings an increase of CO2 emission until 2020 regardless of the pace of nuclear power development. Second, because CHP will defer highly-efficient AGCC (advanced gas combined cycle generation) due to suppressed demand growth of utilities in the daytime when most of commercial CHP systems operate. CHP can reduce CO2 emission only if generating efficiency of CHP will be improved up to 50% or higher.
The power-frequency withstand voltage tests are regulated on electric power equipment in JEC by evaluating the lifetime reliability with a Weibull distribution function. The evaluation method is still controversial in terms of consideration of a plural number of faults and some alternative methods were proposed on this subject. The present paper first discusses the physical meanings of the various kinds of evaluating methods and secondly examines their effects on the power-frequency withstand voltage tests. Further, an appropriate method is investigated for an oil-filled transformer and a gas insulated switchgear with taking notice of dielectric breakdown or partial discharge mechanism under various insulating material and structure conditions and the tentative conclusion gives that the conventional method would be most pertinent under the present conditions.
To understand physical phenomena in gas circuit breaker, we developed a highly accurate analysis method for compressible fluid considering arc behavior. The feature of the method is as follows, (1) To suppress numerical oscillation, the product of density and internal energy is treated as unknown valuable of transport energy equation solved by CIP (Constrain of Interpolation Profile) method. (2) To consider the effect of ablation of nozzle wall the rate of evaporation is assumed to be proportion to the difference between the power emission rate of wall and the intensity of radiation in the space. (3) To solve linear equation systems appeared in pressure, electric and radiation fields, we have improved PCG (Preconditioned Conjugate Gradient) method by reduction of unknowns. We have applied the method to an ablation measurement test stand and an interrupter model of gas circuit breaker, and confirmed the calculation results agree with the experimental ones.
Gas insulated switchgear (GIS) has widely been used for the AC power distribution because of its high reliability and compactness. Recently, DC GIS has been developed with various investigations for dielectric breakdown characteristics of DC gas-insulation. GIS insulation is composed of SF6 gas and solid spacers, and it has been recognized that the dielectric performance of DC GIS is mainly influenced by solid spacers. Under the DC stress, the electric field is directed in one way, the effect of electrification for charges to be accumulated in the spacer must be taken into account and also the effect exists in AC GIS because the switching operations may leave the remanent DC charge on the AC GIS spacer. This paper first describes the effective resistivity (the bulk or the surface) of the solid spacer under the DC stress from the experimental investigation, and the critical factor on the solid spacer what cause to reduce the dielectric performance of the GIS insulation is studied. Secondly, the present paper deals with the electrification on the GIS with various surface roughnesses of epoxy insulator and metallic electrode. Finally, the DC insulation characteristics of GIS insulator are investigated from the experimental results.
This paper presents a new genetic algorithm “Search Space Logarithm Type Genetic Algorithm Considering Mutation Rate: MSSLGA” for optimization control problems of the Multi-input Power System Stabilizer (MPSS) design. Through the MSSLGA, in general, all the search space of tuning parameters for MPSS can be presumed in the range of 0.01˜100.0. First, this paper proposes developing it into the logarithm to cover the large scale disadvantage. Second, it is presented that mutation rates are decreased together gradually with the generation from the big value. The MSSLGA is possible to obtain the higher-fitness answer easily than the conventional Genetic Algorithm using a constant mutation rate. It is applied to the optimum design of MPSS using Series Compensation Method in power system, which contains low-frequency oscillations, and the efficiency through the MSSLGA is superior to conventional one.
Increase of static electrification activity and discharge generation was experienced during the service operation of an aged power transformer. The transformer oil had high sulfide and sulfoxide contents and was liable to show high ECT value after aging. However, there was no apparent increase in standard ECT (electrostatic charging tendency) measurement of the insulating oil and, therefore, deterioration of pressboard was suspected for the cause of the increase. The ECT tests with aged oil and pressboard sampled from the aged transformer were insufficient to demonstrate the increase in static electrification for the aged transformer. On the other hand, the results suggested a possibility that increase in static electrification can be caused by adsorption of some deterioration compound in the aged oil to the pressboard. In order to make more effective evaluation on the transformer insulation, potential measurement on the pressboard in the oil duct was carried out. The experimental results demonstrated strong increase of the accumulated charge by the aged pressboard, which suggested effectiveness of potential measurement for the assessment of static electrification in transformers. The device of potential measurement for practical use was designed by reducing the necessary amount of oil sampling.
We have developed a novel evaluation technique of the deterioration degree of insulators for breakers using a chemical analysis and the Mahalanobis-Taguchi (MT) method. It is possible to evaluate the deterioration degree with great accuracy and nondestructively on-site by this technique without the effect of humidity and external noise such as electromagnetic wave. The mechanism of insulator's surface resistivity reduction was clarified, and it was found that the deterioration degree of insulators could be evaluated by this technique because a linear relationship existed between the results judged by the MT method and the actual measurement results for surface resistivity. In comparison to electrical methods such as partial electric discharge and megohmmeters, the evaluation accuracy has been improved by three digits and the range of the deterioration degree that could be evaluated was expanded by seven digits.
When the effects of humidification temperature on air utilization properties of PEFCs were investigated, (1) in standard humidification conditions, cell voltage decreased with increase of air utilization, (2) in low humidification conditions, cell voltage increased with increase of air utilization, (3) in high humidification and high utilization conditions, cell voltage suddenly dropped with slight increase of air utilization. We proved that based on experimentally obtained ohmic polarization, oxygen gain, and internal resistance free cell voltage during pure oxygen tests, by combining the following results we could provide an explanation for cell voltage behavior in the three cases: (1) calculation of water vapor partial pressure in the cell and change in activation polarization based on oxygen concentration decrease in the cell, (2) increase in relative humidity in the cell due to increase in air utilization, and consequent increase of concentration polarization, and (3) change in catalyst utilization rate with change in humidification temperature, and resulting change in properties such as cell voltage.