The article reviews recent technology trend of overhead transmission line conductors and fittings. Especially, this article deals with “comparison between domestic and foreign conductors and fittings from view points of design, standard and test procedure”, “efficiency technology”, and “Technology of the improvement in reliability”.
This paper proposes a design strategy for a power system stabilizer based on the wide-area measurement of angular velocities to improve a mode of concern, which is a dominant inter-area mode, at each system operating point. The design strategy, which is based on a concept of adaptive controller, has fours step that are dominant mode identifying, controller output location, feedback signal weighting and parameter tuning. The proposed feedback signal weighting is to add weighting numbers to feedback signals using only one power system stabilizer. It is based on an optimal problem of maximizing the residue of the mode of concern for the feedback signal while minimizing those of other modes. Then the tuning process can focus on only the mode of concern. In this paper, the last two steps of feedback signal weighting and parameter tuning are performed using an iterative method. The proposed design framework has been tested on the IEEJ East 10-machine and West 10-machine systems. The result shows that the designed controller can improve the mode of concern significantly, while it can not affect much the others.. It is also seen that the design strategy is appropriate for a concept of an adaptive controller.
More and more distributed generators (DGs) using inverters are being connected to power systems. However, DGs with a conventional inverter do not have synchronizing power. As DGs, especially photovoltaic generators (PVs) grow at this rate, power system will become unstable, because of the shortage of synchronizing power. The purpose of this study is to improve stability of power systems with DGs. In this paper, we propose a “Synchronization Inverter”, which has a synchronizing power similar to that of a synchronous generator and its control equipment. This inverter is operated according to the control method based on a swing equation, a governor control logic and a power equation. We investigated the stability of power system with DGs by simulation, and compared conventional inverter with the Synchronization Inverter. As a result, when a Synchronization Inverter was introduced into a power system with DGs as a substitute for the conventional inverter, the stability of the power system improved.
Recently, electric power systems become more complex and that makes it more difficult to control power systems. Due to development of WAMS(Wide Area Measurement System), power system data are available online. In this paper, we propose a novel method that can predict transient stability multi swing step-out using anomaly detection with data mining. Especially we focus our attention on the theory of ChangeFinder which uses SDAR algorithm and the two step learning model. The forgetting parameter r used in SDAR is set by supervised learning. Active powers obtained by transient stability simulations are inputted to ChangeFinder and the proposed method can detect multi swing step-out. We verify the validity of the proposed method by simulations on the IEEJ 10 machine 47 bus-system.
In recent years, the deterioration in the power quality of a distribution system such as the aggravation of voltage imbalance and current imbalance or the increase of harmonics has been apprehended. It is thought to be causally related to the diversification of load by progress of power electronics technology and the increase of the number of interconnection of distributed generators for home use with the reduction of the effect on the environment. The purpose of this study is development of power conditioner systems (PCSs) with a function of improvement of power quality in the distribution system. In this paper, the authors propose a control method of restraint of harmonics and improvement of voltage imbalance in the distribution system utilizing the PCSs of photovoltaic systems. Moreover, it includes a determination method of the interconnection power factor and the optimal gain of filtering operation of PCSs so as to minimize the voltage imbalance factor and so as to minimize the maximum value of voltage total harmonic distortion in the distribution system by real-time feedback control with measured data from the information technology switches of distribution line. The numerical calculation is carried out in order to verify the validity of the proposal method.
The Vacuum Circuit Breaker (VCB) achieves the high current interrupting capability in the pressure lower than 10-5Pa. When gas pressure increases, the breakdown voltage of a VCB decreases according to Paschen's law, and in the case of small leak, the partial discharge will occur in the VCB and the high frequency electromagnetic waves are radiated. So, we have developed the partial discharge detection system using an antenna with the region from 200MHz to 300MHz placed inside the VCB. However, if the partial discharge occurs outside the VCB, the detection system leads to misdetection as the partial discharge inside the VCB. In order to improve the performance of partial discharge detection, the outputs of antenna voltages inside and outside the VCB are investigated.
This paper analyzes contribution ratios of technological progress and mass production effects, and cost-effectiveness of R&D and subsidization from the viewpoint of solar cell price reduction in Japan. For the analysis, contribution ratio of mass production effects by scale merit and learning-by-doing is estimated based on annual and cumulative production of solar cells and allocated into subsidy, net-metering, Feed-in Tariff and secondary effects of R&D. Contribution ratio of technological progress is estimated based on correlation between solar cell price reduction and technology knowledge stock after removing mass production effects estimated as their contribution ratio. Cost-effectiveness is analyzed based on the estimated contribution ratios and R&D expenditures and subsidy. The results of the analysis show contribution ratio of technological progress, which is contribution ratio of R&D, is around half of the total price reduction. Contribution ratio of mass production effects is around quarter and mainly based on subsidy and net metering. Cost-effectiveness of subsidy was higher than that of R&D initially, but it has dropped rapidly. In 2000s, cost-effectiveness of R&D became higher than that of subsidy. This means R&D should have been allocated more expenditures, especially on crystalline silicon solar cells, which could decrease solar cell price more cost-effectively.
The prospective transient recovery voltage (TRV) at current interruption for circuit breakers should be measured by using ideal circuit breaker. But, it is very difficult to measure the prospective TRV because there is no ideal circuit breaker. It is often used a vacuum circuit breaker or a diode to measure the TRV. It is difficult to decide the current zero by the arc voltage or the forward voltage drop. This paper shows the new method to decide the current zero for breaker terminal fault (BTF) interrupting condition at low voltage measurements using diode. It was found that the SiC diode is suitable to use the TRV measurement. The forward voltage drop of the SiC diode is nearly constant. The terminal voltage of the diode in BTF circuit during the current flowing is nearly constant regardless of the interrupting current. But, the terminal voltage after current interruption is varied with the amplitude of the current. The current zero is a border between the voltage constant region and varied region. We can find the current zero from the voltage waveforms by plural measurements.
When a fault arc occurs in oil-filled electric power equipment such as transformers in transmission and distribution systems, it generates a flammable gas and a dynamic pressure rise that may trigger an explosion. The purpose of this fundamental study is to investigate the effects of the arc under electrical insulation oil on pressure rises in a closed vessel containing air and oil. In particular, this paper is intended to investigate the relationship between the pressure rises and the generated bubble behavior by the arc. The pressure rises in both air and oil are measured under experimental conditions involving an arc current ranging from 2.3 to 8.9kA, an arc duration of 10 or 100 milliseconds. Experimental results show that the behavior of a bubble affects the pressure rises in the air and the oil as low-frequency pressure oscillation comparatively.
In EMTP, it is very hard to simulate a vertically arranged cable, since its surge impedance gradually changes with the distance from the ground to a top point. In the past, some researches about surge impedances and responses of vertical conductor (for example transmission tower, concrete pole and so on.) have been carried out, these researches are being continued now. However, there is no model of vertical co-axial cable in EMTP. In order to analyze surge voltage arisen on the electrical system, approach of method for treating this model in EMTP is required. In this paper, experiments of surge impedance and response on vertical cable, method of treating for vertical co-axial cable in EMTP and accuracy confirmed as compared result of this model with analysis result of VSTL Rev. (Virtual Surge Test Lab. rev. ) which is constructed under FDTD (Finite Difference Time Domain) method, are reported.
A new mechanical CBM (Condition Based Maintenance) system for an electromagnetically actuated vacuum circuit breaker (VCB) has been developed. This CBM function has a new monitoring method using analysis of the coil current profile of the actuator operation. The VCB has three sets of vacuum interrupters, insulating rods, contact pressure springs and electromagnetic actuators. The electromagnetic actuators control each phase independently. We have clarified the variation in the actuator's current profile by the developed analytical method when the value of friction, contact erosion and driving capacitance changes. We have established a diagnostic method for the mechanical condition using this current profile analysis. With this method, a new remote monitoring system of the mechanical condition using current monitors on the actuator's controller has been developed and mounted on VCB for cubicle type gas insulated switchgears rating from 7.2kV to 84kV. The maintenance for mechanical parts of VCB changes to the CBM system from the conventional TBM (Time Based Maintenance) system using this monitoring system. The developed mechanical CBM system significantly reduces the life cycle cost including the labor cost of maintenance.
There were 18 electric vehicles, EV, in average, per quick charger, QC, in Japan as of 2012, and this value may increase by a factor of several dozen by 2020. It is therefore necessary to model and analyze QC service, identify the causes of wait time and provide countermeasures to avoid significant QC congestion and to encourage the spread of QC stations. This research analyzed usage data of a QC installed at an existing service area on expressway, and showed the characteristics of QC demand as distribution functions. QC service was modeled as a queuing problem, and simulations were carried out using derived distribution functions. The results showed that the QC station needs additional charger in the case of daily charging times over 10 times.
MHD (magnetohydrodynamic) electrical power generation experiments have been conducted with a seed-free high temperature inert gas plasma in a disk-shaped Hall-type generator driven by a single-pulsed shock tunnel. Xenon is used as a working gas to archive a high performance at a low inlet total temperature, where the total gas temperature is varied in the range of 4600-10000K at the generator inlet. An enthalpy extraction ratio of 4.8% is obtained at the inlet total temperature of 7000K, and this value is much higher than that for argon at the same inlet total temperature. The unstable and non-uniform plasma attributed to ionization instability is observed at a high magnetic flux density and a high load resistance.
The constrained interpolation profile (CIP) method, which is one sort of the finite-difference methods, has been recently applied to transient electromagnetic field simulations. Differently from the finite-difference time-domain (FDTD) method, the CIP method considers not only electric- and magnetic-field values at grid points but also their spatial derivative values there. In principle, therefore, it could suppress numerical dispersion and instability even when a relatively coarse grid is used. In this technical note, fundamentals of the CIP method and its formulations for computing electromagnetic fields in the 3D Cartesian coordinate system and in the 2D cylindrical coordinate system are briefly explained. Representative applications are also shown.
Upward lightning flashes in winter frequently damage wind turbines in the coastal area of the Sea of Japan. Aspects of initiation of upward leaders of such flashes of winter lightning were investigated by using optical images recorded by 30 fps digital video cameras at 12 wind turbines. Moving blades generate upward flashes more likely than stationary blades. Among the 252 analyzed upward flashes, only one flash was confirmed to be initiated not from the tip part of a blade.
A thermopile-type pyranometer has a response delay due to heat capacity of the thermopile. In this study, a method to compensate the response delay has been proposed, and then it has been confirmed experimentally that the method is effective.