Because of real introduction of distributed power generation (DG) such as photovoltaic power generation, wind power generation, co-generation system and so on, it becomes necessary to investigate some technical measures of the utility distribution system to cope with the introduction of DG. The METI organizes about the directionality of technical development for the distribution system by some committees. Focusing on the result of the governmental investigations, this paper describes development trend and subjects of future new distribution network system which makes it possible to achieve smooth introduction of DG and to utilize DG successfully for load leveling, keeping power quality, enhancement of supply reliability and so on.
This paper describes a novel operating method using prediction of photovoltaic (PV) power for a photovoltaic-diesel hybrid power generation system. The system is composed of a PV array, a storage battery, a bi-directional inverter and a diesel engine generator (DG). The proposed method enables the system to save fuel consumption by using PV energy effectively, reducing charge and discharge energy of the storage battery, and avoiding low-load operation of the DG. The PV power is simply predicted from a theoretical equation of solar radiation and the observed PV energy for a constant time before the prediction. The amount of fuel consumption of the proposed method is compared with that of other methods by a simulation based on measurement data of the PV power at an actual PV generation system for one year. The simulation results indicate that the amount of fuel consumption of the proposed method is smaller than that of any other methods, and is close to that of the ideal operation of the DG.
This paper deals with a new detection method based on 3-phase vector operation for voltage sag. The detection method is applicable to a protection system using a high speed interruption system which protects distributed generators and critical loads in a customer’s facility. First, the algorithm and merits of this method are explained in detail. Secondly, the detection characteristics are analyzed using the ATP (Alternative Transients Program) and are confirmed using a real time digital simulator, and it is shown that the method is useful for detecting voltage sag.
“Tracing Power Flow of Electricity" is the concept that has become a focus of attention recently, as the deregulation or the liberalization of electric power markets proceeds. Although a number of methods, such as “Tracing Method by Power Flow Proportion", have already been published, reactive power contribution has never studied much so far. However applying `Tracing Power Flow of Electricity’ to ancillary service, for example compensation of reactive power, it is very important. In this paper, we pay attention to line flows and static capacitors in particular, and we study how to deal with the problem. We do computer simulation using a sample system and show the tracing results.
After the application of the Lagrange relaxation method to the unit commitment scheduling by Muckstadt in 1979, many papers using this method have been reported so far. The greatest advantage of applying the Lagrange relaxation method for the unit commitment problem is that it can relax (ignore) each generator’s output dependency caused by demand-supply balance constraint so that an unit commitment of each generator is determined independently by Dynamic Programming. However, when we introduce the transmission loss into the demand-supply balance constraint, we cannot decompose the problem into the partial problems in which each generator’s unit commitment is determined independently and have to take some measures to get an optimal schedule by Lagrange relaxation method directly. In this paper, we present an algorithm for the unit commitment schedule using the Lagrange relaxation method for the case of taking into account transmission losses.
This paper presents the results of analyses about transient stability augmentation by the fuzzy logic controlled braking resistor in a Multi-Machine power system. Following a major disturbance in electric power system, variable rotor speed of the generator is measured, and then the current through the braking resistor is controlled by the firing-angle of the thyristor switch which is controlled by the fuzzy logic. Thus the braking resistor controls the accelerating power in generators and makes the system transiently stable. Simulations are performed by using EMTP (Electro-Magnetic Transients Program). Through the simulation results of both balanced (3LG: Three-phase-to-ground) and unbalanced (1LG: Single-line-to ground, 2LG: Double-line-to ground and 2LS: Line-to-line) faults at different points in the IEEJ West-10 machines system model, the effectiveness of the proposed fuzzy logic controlled braking resistor is demonstrated and the optimal conductance value of the braking resistor in enhancing the transient stability is investigated.
At a multipurpose dam, it is necessary to forecast inflow to control flood safely and to operate hydraulic power plant efficiently. In this paper, we propose a method of forecasting the inflow of several hours later by neural network. The correlation is high about the inflow and rain which fell in the dam basin, but it is difficult to forecast by mathematical methods, because the relation is non-linear model. The neural network system can forecast the inflow by learning the past data of inflow and rain in the basin. This system can forecast inflow well after 1 hour or so. However, this system becomes inaccurate rapidly when it tries to forecast inflow at 3 or more hours later, because we use the rain data of the dam basin. Therefore, we also use rain data which is out of the dam basin and in the direction of the windward. The rain data contains information of the rain which will fall at the dam in future. Then, forecast results show that our system is effective.
In this paper, the practical impedance approach steady-state analysis in the frequency domain of the three-phase self-excited induction generator (SEIG) with a squirrel cage rotor is presented, along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover (VSPM) in addition to a constant-speed prime mover (CSPM) such as a wind turbine and a micro gas turbine for the clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate electro-mechanical equivalent circuit and the operating performances of the three-phase SEIG coupled by a VSPM and/or a CSPM in the steady-state analysis are evaluated and discussed on line under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM as well as a CSPM is implemented for the small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreements with those ones obtained from the simulation results. Furthermore, a PI controlled feedback closed-loop voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static VAR compensator (SVC) composed of the thyristor phase controlled reactor (TCR) in parallel with the thyristor switched capacitor (TSC) and the fixed excitation capacitor bank (FC) is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with the SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in the steady-state operations in terms of the fast response and the high performances.
The basic breakdown characteristics of the silicone oil as an insulating medium was studied with aim of realization of electric power apparatus which may be considered to be SF6 free and flame-retarding. As the first step, the impulse breakdown characteristics was measured with three kinds of electrodes whose electric field distributions differed. The breakdown characteristics in silicone oil was explained in relation to stressed oil volume (SOV) and the breakdown stress. At the second step the surface breakdown characteristic for impulse voltage was measured with two kinds of insulators which was set to between plane electrodes. The surface breakdown characteristic for impulse voltage was explained in relation to the ratio of the relative permittivity of oil and insulator. And on the third step, the breakdown characteristics of oil gap after interrupting small capacitive current was studied. In this experiment, the disconnecting switch to interrupt capacitive current was simulated by oil gap after interrupting impulse current, and to measure breakdown characteristics the high impulse voltage was subsequently applied. The breakdown stress in silicone oil after application of impulse current was discussed for insulation recovery characteristics.
For the establishment of a more effective grounding design, it is necessary to clarify a transient behavior of a grounding system. In order to verify the current dependency of the grounding electrodes in a distribution system and the behavior of the lightning surges into customer’s premise through the power lines, experiments were conducted using the 3MV impulse voltage generator on a full-scale distribution system and a power line surge simulation mock-up constructed for this purpose. As a result, the behavior of the currents in the distribution system and the possible effects of mutual interference between grounding potentials were successfully identified. In addition, with the lightning surge flow, applied current and low-voltage grounding system parameters, it was possible to evaluate the magnitude of the lightning surges into customer’s facility.
This paper describes a method to design a thermoelectric module in the thermoelectric generation system with an environmental load evaluation. We analyzed an energy ratio defined as the electrical output over the equivalent electrical input and life cycle CO2 emissions for each module design in the thermoelectric generation system. It was found that the optimum module design could be decided uniquely by the evaluation of the energy ratio or life CO2 emissions in the thermoelectric generation system. And by applying the optimum module design in the system, the thermoelectric generation system with a low environmental load could be designed and developed.
Recently the high attention for fuel cell electric vehicle (FCEV) is pushing to construct the hydrogen supplying station for FCEV in the world. The hydrogen pressure supplied at the current test station is intended to be high for increasing the FCEV’s driving distance. The water electrolysis can produce cleanly the hydrogen by utilizing the electricity from renewable energy without emitting CO2 to atmosphere, when it is compared to be the popular reforming process of fossil fuel in the industry. The power required for the high-pressure water electrolysis, where water is pumped up to high-pressure, may be smaller than the power for the atmospheric water electrolysis, where the produced atmospheric hydrogen is pumped up by compressor, since the compression power for water is much smaller than that for hydrogen gas. In this study the ideal water electrolysis voltage up to 70MPa and 523K is estimated referring to both the results by LeRoy et al up to 10MPa and 523K, and to the latest steam table. By using this high-pressure water electrolysis voltage, the power required for high-pressure hydrogen produced by the high-pressure water electrolysis method is estimated to be about 5% smaller than that by the atmospheric water electrolysis method, by assuming the compressor and pump efficiency of 50%.
Very fast transients (VFTs) occur in a gas insulated switchgear (GIS) at a disconnecting switch operation. VFTs are high frequency surges and are characterized by a fast steep wavefront and an oscillating waveform. VFTs cause voltage oscillations in a transformer winding connected directly to a GIS. VFTs in the GIS are simulated using the Laplace transform. The fast steep wavefront and the oscillating waveform attaking on the transformer are shown as a function of GIS constitutional parameters. For a case study, influence of the fast steep wavefront and the oscillating waveform is investigated on 550kV class transformer. In the case of VFTs at the transformer, a voltage level of the fast steep wavefront is larger than an amplitude of the oscillation waveform. However the interturn voltage oscillation in the winding caused by the oscillation waveform can be larger than that by the fast steep wavefront. The authors deduce that the voltage oscillations do not threaten the reliability of the interturn insulation.
The arcing behavior under the circumstance of rich copper vapor in a capillary glass tube were experimentally observed by currents and voltages and spectroscopic method. The arc voltage is affected by the inner diameter of glass tube, the higher arc voltage is, the narrower inner diameter of glass tube is, under otherwise same experimental conditions. It is supposed by the spectral measurement that the arc voltage in a capillary glass tube depents on the arrangement of copper vapor surrounding the arc column. It seems reasonable to consider that the arc voltage increases higher according to the copper vapor layer surrounding arc column forcing the ac current channel to narrow as the inner diameter of glass tube is rendered smaller.
Fault current limiting experiments were performed for parallel connected fault current limiting elements (FCL) which were arranged polygonal and on plane. It is found that the arrangement didn’t depend on the current limiting characteristics. The current re-distribution was observed at early stage of quench, and it is found that the current re-distribution accelerate the quench. Moreover, the normal operation tests were carried out for the parallel connected FCL, and the loss of the polygonal arrangement was about 1/5 comparing that of the on plane arrangement. Therefore, the advantage of the polygonal arrangement was confirmed.
It has been widely accepted that Gas Insulated Switchgear (GIS) has proven to be reliable, compact and has high availability. However, metallic particles forced to fly and kept in motion in high electric field, can cause partial discharges which lead to a flashover of GIS. Authors have formulated time vs vertical motion equation for a metallic particle on the basis of the statistical analysis of the time-resolved and digitized motion data obtained by a high speed framing video camera, introducing charging-suppress factor η for the coated electrode. Numerical solution of the time-motion equation gives the incidence/departure velocity upon the grounded electrode. Fairly well-agreements have been confirmed between the measured and simulated behavior of the particle’s motion, including its maximum flight height. A metallic wire particle was fixed at various height on a Teflon (PTFE) string tighten radially across the coaxial electrodes. The radius of light emission generated by the partial discharge on both ends of the metallic particle have been observed by an Image-Intesifier. The partial discharge-free allowable maximum flight height and the insulation reliability of GIS have been deduced for various size of the particle as a function of electric field and coating condition, on the grounded electrode combining the simulated particle behavior and observed radius for streamer criteria.
It has been widely accepted that Gas Insulated Switchgear (GIS) has proven to be reliable, compact and has high availability. However, metallic particles forced to fly and kept in motion in high electric field, can cause partial discharges which lead to a flashover of GIS. For the metallic wire particle with the length less than 3mm, its revolving flight and horizontal migration behavior become remarkable. This has been confirmed by the high speed framing video camera. For the revolving particle, we also found that the viscous drag which acts on it controls its flying behavior predominantly. Authors have formulated time motion equation for a revolving metallic particle on the basis of the statistical analysis of the time-resolved and digitized motion data obtained by a high speed framing video camera and taking the drag as one of the major force term. Numerical solution of the time-motion equation gives the maximum flight height-time curves, incidence, departure velocity and migration velocity of the revolving particle against the grounded electrode with or without slope. Fairly well-agreements have been confirmed between the measured and simulated dynamic behavior of the revolving particles. The other major parameters such as allowable maximum flight height, the climbing or descending speed and distance along the slope of the grounded electrode and the trapping factors of a particle trap has been revealed deductively through the simulation. This enables it to optimize the configuration and the operational performance of the particle trap.
We have developed an electro-magnetic pulse simulator for the radiated susceptibility tests that can generate three kinds of electro-magnetic pulses including nanosecond rise time and high electric field pulse. This paper describes simulated and measured results for the fastest rise time voltage generator of this simulator. A new circuit of the voltage generator has developed to stabilize the output voltage waveform and the effect of the connection geometry between the generator and an antenna is estimated by using transient electro-magnetic analysis program based on method of moment by triangular patch modeling.
Fuel cross leak through a polymer electrolyte membrane of the direct dimethyl ether fuel cell (DDFC) was investigated and was found to be approximately one-tenth that of the direct methanol fuel cell (DMFC). Three phenomena known to appear in the DMFC were also observed in the DDFC. These were (1) fuel cross leak due to the diffusion which increases with the fuel concentration on an open circuit condition, (2) electro-osmotic cross leak, which increases with the current density and fuel concentration, and (3) decrease of fuel cross leak with the increase of the current density due to fuel consumption at low fuel concentration. The decreased fuel cross leak realized by using Nafion ®117 as a membrane and the low fuel concentration of 11% resulted in an increase of the Farady efficiency of the DDFC of up to 90% at a current density of 80mA/cm2. The CO2 quantity at the anode outlet of the operating DDFC was slightly less than 2 mol per 12 protons, as estimated from an electrochemical reaction on the anode. The CO2 quantity at the cathode outlet was also investigated. The CO2 cross leak increased with current density at every CO2 concentration and the diffusion appeared to be the dominant phenomenon of the CO2 cross leak.