This article reviews past studies on the long-term CO2 abatement strategy dealing with electric technologies and thereby attempts to draw sound understandings of effectiveness of those measures. It is widely known that electrification of final energy uses plays an important role to mitigate CO2 emissions through curbing fossil fuel consumption. Electrification of thermal demand by high-efficient heat-pump technologies is considered as a realistic example, while electric vehicles including plug-in hybrid vehicles are getting higher expectations as an alternative in the transportation sector. It is of crucial importance, therefore, to carefully analyze the potential of CO2 emission reductions by these measures and to establish viable long-term strategies taking them fully into consideration. The author provides a numerical representation of such strategy development up to the year 2050.
The Great Hanshin-Awaji Earthquake occurred on January 17, 1995, and our facility had received big damage by earthquake. In this paper, I explain the point of the power transmission at the early stage, the situation of the equipment damage, the countermeasures, and the impression that looks back at that time.
In this paper, power system transient stability is simulated by using the new method of power system transient stability simulation. It combines the desirable features of both the time domain technique based on OOP (Object-oriented Programming) and the TEF (Transient Energy function) of detailed generator model. OOP is an alternative to overcome the problems associated with the development, maintenance and update of large software by electrical utilities. Several papers have already evaluated this approach for power system applications in areas such as load flow, security assessment and graphical interface. This paper applied the object-oriented approach to the problem of power system transient stability simulation. The modeling method is that each block of dynamic system block diagram is implemented as an object and connected each other. In the transient energy method, the detailed synchronous generator model is so-called two-axis model. For the excitation model, IEEE type1 model is used. The developed mothed was successfully applied to New England Test System.
Application of diesel generators to supply the load demand on isolated islands in Indonesia has widely spread. With increases in oil price and the concerns about global warming, the integration of diesel generators with renewable energy systems have become an attractive energy sources for supplying the load demand. This paper performs an optimal design of integrated system involving Wind-PV-Diesel-Battery system for isolated island with CO2 emission evaluation by using genetic algorithm. The proposed system has been designed for the hybrid power generation in East Nusa Tenggara, Indonesia-latitude 09.30S, longitude 122.0E. From simulation results, the proposed system is able to minimize the total annual cost of the system under study and reduce CO2 emission generated by diesel generators.
Several homogenized models are compared for accurate representation of ac magnetic properties of silicon steel sheets. Two of them are generalized Pry and Bean models that have a parameter for the frequency dependence of eddy-current loss. The third model assumes a quadratic distribution of magnetic flux density along the thickness direction. The other model is an extension of linear magnetization model. Numerical simulations show that the third model yields inaccurate BH loops whereas the other models accurately represent BH loops.
In Japan, operational principles from the mechanical-type era, such as the directional ground relay (DG) and overcurrent relay (OC), are still used without modification for the protection of distribution lines. We are now facing various problems, such as ground faults with high fault resistance in systems isolated from the ground. A new operational principle to solve the above problems is summarized below. ·A fault is simulated by replacing a branched distribution line with a one-section single distribution line, in which loads are concentrated at its terminals. ·Lines with a one-line to ground fault are detected on the basis of the relationship between the fault-phase voltage E before the fault and the fault current using Ho and Thevenin's theorem. ·Faults are assumed to occur at both terminals in the section. If the signs of the obtained fault reactance Xf at the two terminals are opposite, it is judged that a fault point where Xf = 0 holds exists within the section. As a result of the simulation using the program we developed, it was confirmed that no errors in the detection of the internal and external ground faults with a high fault resistance of 0-30kΩ were observed.
Currently, the prevention of a fault cascade during large-scale power blackouts is solely dependent on system operators. However, it seems impossible for operators to calmly decide and perform an appropriate shutdown in an emergency when unpredictable events continuously develop. Therefore, it is desirable to construct a “fault cascade control system”, which collects information on the entire system, shuts down generators and loads, and reduces the responsibility of the operators. The theory proposed in this paper has the following features. (i) The voltages and currents are represented in terms of complex values and the power system is represented using Kirchhoff's first and second laws. (ii) Linear power equations are presented, in which generators and loads show constant current characteristics independent of voltages. Then, the opening and closing of branches are simulated by equivalent virtual phase shifters and changes in the system conditions are simulated by a pivot operation in the linear programming (LP) method. Branch overload, node voltage anomalies, and disconnection from the system are detected. The fault cascade control system adopts the implicit enumeration method to resolve system anomalies based on the value of control variables that can be either 1 or 0. We developed a program on the basis of this theory, and verified the validity of the theory by simulating a route cutoff fault in a 500/275kV loop system.
The integrated circuits with low driving voltages have been widely used in high-efficiency power equipments, information communication equipments, medical equipments so on. However these equipments are very liable to be weak when surges occur as lightning surges, switching surges and/or static discharges. The overvoltages generated from the surge will affect power apparatus and electric appliances, which make of deterioration. Moreover the overvoltages occur frequently in power switching devices or lightning phenomena as multi strokes. Therefore AC phase controlled testing apparatus superimposed with high voltage double pulses has been developed in order to investigate effects of overvoltages to insulating materials and surge protection devices. The developed device will control the double pulses at any phase angle with phase control circuits consisting of RC integrated circuits controlled by the triggering circuit of zero-cross AC power source. This paper describes a developed AC phase controlled testing apparatus superimposed with double pulses and small gap breakdown characteristics as one of its applications.
Much of oil filled (OF) cable has been used for a long time for 66∼500kV extra high voltage cable. Sometimes we can see extremely degraded tanδ oil (several tens % of tanδ, for example) in joint box etc. The calculation results of tanδ on a simple combination model of paper/oil show that, tanδ of oil impregnated paper with such a high tanδ oil is extremely high and it must result in a thermal breakdown. However such an event has not taken place up to the present in actually operated transmission line. This fact suggests that some suppression mechanism of tanδ has acted in the degraded tanδ oil impregnated paper insulation. Therefore we investigated the tanδ characteristics of oil impregnated paper with extremely high tanδ oil in detail. In addition, based on the investigation results, we developed a simulation method of heat generation by dielectric loss in OF cable joint (which has degraded tanδ oil).
Plasma quenching efficiency by ablated vapor of polymers containing nitrogen atom was numerically investigated for the inductively coupled thermal plasma technique. Polyamide66 (PA66), which contains nitrogen atoms, was used for polymer materials, and it is injected into Ar thermal plasma in the numerical simulation. The simulation model considered heating, melting and evaporation of polymer powders, and then plasma quenching phenomena due to polymer ablation. Thermodynamic and transport properties of ablated vapor were also taken into account. It was found that PA66 vapor has a high plasma-quenching efficiency than other polymer materials of PTFE, POM, PMMA and PE. The calculated results were confirmed to be valid comparing with experimental results in terms of ablated vapor distribution and powder velocities.
In this letter, theoretical formulae, derived on the basis of the transmission-line theory by Bewley and by Jordan more than 50 years ago, for the characteristic impedance of a vertical conductor have been revisited and evaluated.