This paper describes a prospect toward electric power production by the Fusion energy. In the first part of the paper, a principle of TOKAMAK system which is the successful magnetic-confinement-systems for fusion reactors are shown, and then the ITER project based on TOKAMAK and the present status of ITER is reviewed. In the remainder of the paper, a roadmap for fusion energy and conceptual designs of Demonstration reactors are briefly described.
Advancements have been made towards inclusion of both static and dynamic security into transfer capability calculation. However, to the authors' knowledge, work on considering corrective controls into the calculation has not been reported yet. Therefore, we propose a Total Transfer Capability (TTC) assessment considering transient stability corrective controls. The method is based on the Newton interior point method for nonlinear programming and transfer capability is approached as a maximization of power transfer with both static and transient stability constraints are incorporated into our Transient Stability Constrained Optimal Power Flow (TSCOPF) formulation. An interconnected power system is simulated to be subjected to a severe unbalanced 3-phase 4-line to ground fault and following the fault, generator and load are shed in a pre-defined sequence to mimic actual corrective controls. In a deregulated electricity market, both generator companies and large load customers are encouraged to actively participate in maintaining power system stability as corrective controls upon agreement of compensation for being shed following a disturbance. Implementation of this proposal on the actual power system operation should be carried out through combining it with the existing transient stabilization controller system. Utilization of these corrective controls results in increasing TTC as suggested in our numerical simulation. As Lagrange multipliers can also describe sensitivity of both inequality and equality constraints to the objective function, then selection of which generator or load to be shed can be carried out on the basis of values of Lagrange multipliers of its respective generator's rotor angle stability and active power balance equation. Hence, the proposal in this paper can be utilized by system operator to assess the maximum TTC for specific loads and network conditions.
In order to analyze transient stability of large-scale power systems, it is advantageous to apply system reduction method to external systems. Short-circuit current method is one of the typical engineering reduction techniques. However, the dominant eigenvalues are not necessarily conserved in the reduced system. Therefore, the hybrid reduction method in which controller parameters are adjusted to conserve the dominant eigenvalues was proposed. Automatic voltage regulator (AVR) and power system stabilizer (PSS) have been used for parameters adjustment so far. However, since there are many parameters in AVR and PSS, complicated procedures are required to adjust them. Therefore, in this paper, the reduced system regulator (RSR) is proposed for hybrid system reduction method. The RSR has only two parameters for adjustment. It is easier to adjust the RSR than AVR/PSS. In addition, the initial gains of the RSR are set zero so that dynamic behavior of the system is not influenced before the adjustment. The effect and the accuracy of the hybrid system reduction method with RSR are examined using a typical longitudinal power system, IEEJ WEST 10-machine system model.
This paper is described a method for improving temperature dependent properties of an intensity modulation type optical fiber current sensor for AC detection using flint glass fiber Faraday sensing element, which has been researched and developed by us. The sensor has highly advantageous properties such as light weight and flexible in various points of view, however, it also has a drawback that its output value is dependent on the ambient temperature where the sensor is installed. The ratio error in the sensor output value changes in the range of -0.4% to +1.2% corresponding to ambient temperature change of -20°C to +80°C. Its temperature dependent property is caused by the combined temperature dependence of a magnetic garnet crystal used in the sensor system and Faraday sensor fiber. We researched this temperature dependent mechanism and devised a gain adjusting method of the signal processing circuit amplifier to an optimum value to reduce the ratio error of the sensor. We verified that the ratio error was reduced remarkably with our method by experiment. The ratio error value obtained by the experiment was -0.1% to +0.2% in relation to ambient temperature change of -20°C to +80°C. This value met the highest accuracy standard for current transformers of protection relays required in JEC 1201-1PS class.
The author devised new method for measurement of the transmission line constants of high precision with the automatic oscillograph. This paper is proposal of new method for measurement of the transmission line constants. The author utilized that the inherent eigenvector matrixs of transmission line had an equal relation with four-terminal constants eigenvector matrixs of transmission line. And the author calculated four-terminal constants of transmission line from the data (voltage-current data of the automatic oscillograph) of six cases of transmission line system faults and devised the method for measurement for transmission line constants from analysis of the four-terminal constants of transmission line next. Furthermore, the author inspected this new method in the system fault simulations of the EMTP transmission line system model. It was shown that the result is the measurement method of high accuracy. From now on, the author advances the measurement of the transmission line constants from actual system faults data of the transmission line and its periphery with the cooperation power system companies.
In high voltage distribution systems, there are many power quality troubles due to voltage dips. Otherwise, a magnetizing inrush current causes the voltage dip. To suppress voltage dips, it is necessary to identify the magnetizing inrush current phenomena. In this paper, the authors propose a new identification method. The principles are that the saturation start/end flux is equal and the inrush current pattern exists. And to avoid a interfere with saturation area overlap; the rectangular coordinate method is adopted.
In relation to the accidents due to bird nests in contact with overhead distribution lines, the authors investigated on life estimation of conductor insulation. The accident is often caused by crow or magpie. There is a region in which magpie is being specified to the protected bird in Japan. In that region, the nest in the breeding season can not be removed easily. Recently, metal wires are used for the nest material. When this conductive material is in contact with the distribution line and the arm, corona discharge will occur. The conductor insulation of the distribution line receives deterioration and there is a possibility of causing the accident. In this study, acceleration test was done to examine time from nest building to causing the accident in the distribution line. The acceleration factor based on the charge amount of corona and the influence of the applied voltage on corona characteristics were discussed. Moreover, the life of the conductor insulation was discussed from the V-t characteristics and the acceleration factor.
When a lightning occurs at the neighborhood of high voltage aerial distribution lines, the overvoltage due to the inductive lightning surge invades to the central line of the insulated wire. Because of the insulated wire is supported by the insulator and the binding wire at the electric light pole, the creeping discharges develop along the wire surface from the free end of the binding wire, just after a flashover of the insulator at the wire supporting point. These creeping discharges give rise to the disaster near the wire supporting point including the punch-through breakdown of wire when the weak points such as pin-holes exist in the wire insulator. To prevent these accidents, it is important to understand the behavior of creeping discharges at the insulated wire surface originating in the lightning strike. Positive and negative creeping discharges reveal the distinctive aspect by the polarities of the inductive lightning surges. In the previous paper, we have clarified the developing process of positive creeping discharge based on the data obtained from an image converter camera. In this paper, we report the developing process of negative creeping discharge. Complicated behavior of negative creeping discharge is clarified using an image converter camera and its process is discussed.
Displacement and/or deformation of a coil in oil-immersed transformers are hazardous. Frequency Response Analysis (FRA) has the possibility to detect these abnormalities with high sensitivity. However, a guideline for diagnosis of transformers by FRA is not yet firmly established. In this paper, FRA is applied to seven oil-immersed transformers installed in substations. Diagnosis methods when initial data do not exist are evaluated. When the initial data do not exist, it may be possible to diagnose by comparing transfer functions of three phases (phase-to-phase comparison) or by comparing transfer functions to those of sister units (sister-unit comparison). The phase-to phase comparison cannot be applied to some kinds of vector groups. The sister-unit comparison is fully applicable and the performance of the comparison can be improved by additionally comparing the transfer functions phase-to-phase. Furthermore, applicability of measurement of the transfer functions without disconnecting the bus from the transformer is evaluated. The bus should be disconnected from the transformer under tests because the measured transfer functions are influenced by bus.