This article addresses applications of meta-heuristics to power systems. They are defined as an iterative solution search algorithm that makes use of simple rules or heuristics to obtain better solutions. In practice, they make use of both intesification and diversification functions. They aim at evaluating a highly accurate approximate solution around a global minimum in optimization problems. In recent years, studies on meta-heuristcs have been positively made to solve the complicated optimization problems in power system operation and planning. In this paper, the recent trends on the applications of tabu search to power systems are discussed. Different strategies of tabu search are introduced to enhance the solution quality and computational efficiency.

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Distribution planning must be carried out by considering (1) geographic information such as allocation of loads and feeders, (2) operational conditions such as line current capacity, voltage drop limit and distribution loss, and (3) facility cost and so on. In order to systematically support the above work by computational approach, optimization techniques are available. In this paper, a computational method to support distributional planning systematically is proposed by introducing (1) geographical optimization technique and (2) configuration optimization technique. The geographical optimization is to determine which of sectionalized lines should supply power to future appeared loads so as to maximize availability ratio of feeders. The configuration optimization is to determine states of sectionalizing switches (opened or closed) so as to minimize distribution loss under the constraints such as the line current capacity, voltage drop limit and radial structure. In the proposed method, after the geographical optimization is carried out to determine future section loads, operational conditions are evaluated by the configuration optimization. If the operational constraints are not satisfied, previously prepared expansion plan candidates are evaluated quantitatively, and then the best candidate is decided. Voronoi diagram is applied to realize the geographical optimization, and tabu search is used to accomplish the configuration optimization. In order to check the validity of the proposed method, numerical results are shown for a distribution system model.

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Open access to electric power transmission networks has been carried out in order to foster generation competition and customer choice in the worldwide. When several PPSs request to simultaneously supply power to customers based on bilateral contracts, it is expected that transmission network accepts amounts of wheeled power requested by the PPSs as much as possible. It is possible to maximize total requested wheeled power by controlling power flow through transmission lines. It is well known that FACTS device is available to control line flow flexibly. In this paper, in order to maximize total wheeled power simultaneously requested by several PPSs, the authors propose an algorithm to determine the optimal reactance of TCSC (one of FACTS devices). The proposed algorithm is based on Particle Swarm Optimization (PSO), which is one of optimization methods based on swarm intelligence. In the proposed algorithm, PSO is improved to enhance ability of searching global minimum by giving different characteristic to behavior of each agent. In order to check the validity of the proposed method, numerical results are shown for 6 and IEEE 30 bus system models.

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In this paper, two-layered neighborhood tabu search is proposed to deal with distribution network expansion planning with distributed generation (DG). The distribution network expansion planning aims at optimizing the route of feeders and allocation of distribution substations while satisfying the constraints. The problem formulation results in a combinatorial optimization problem. In practice, it is quite hard to solve the problem due to the complexity. Recently, DG is widely spread in distribution systems due to the deregulated and competitive power markets. As a result, the distribution network expansion planning with DG becomes much harder. As a meta-heuristic method, tabu search is used to evaluate a better solution. This paper proposes a new method for solving it with two-layered neighborhood tabu search. The first layer deals with the optimal allocation of DG while the second one handles the optimal route of feeders and the optimal allocation of distribution substation. The effectiveness is demonstrated in a sample system.

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This paper proposes a loss minimum reconfiguration method by Tabu Search for open loop radial distribution system with distributed generators. The problem is to find the optimal normal open sectionalizing switch positions which minimize the total distribution line losses subjected to the line/transformer capacity constraints and voltage constraint. Generally, the problem is mathematically formulated as a complex combinatorial optimization problem or mixed integer programming problem, and is solved by using mathematical programming method, heuristic algorithm, intelligent method, etc. However, satisfactory algorithm for power companies has not yet been attained both in computational burden and solution accuracy. Thus, in this paper, the authors propose a method to solve the above problem by using Tabu Search (TS) method. Reverse power flow caused by distributed generators can be included in the solution algorithm. TS is one of meta-heuristic algorithms, and sometimes evaluated to be better compared with Genetic Algorithm (GA) or Simulated Annealing (SA) from viewpoints of both computational speed and solution accuracy. In order to evaluate the validity and efficiency of the algorithm, several numerical examples are shown in this paper.

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This paper presents an effective and practical method based on the Lagrangian relaxation method for solving hydro-thermal unit commitment problem in which operational constraints involve spinning reserve requirements for thermal units and prohibition of simultaneous unit start-up/shut-down at the same plant. This method is processed in each iteration step of LRM that enables a direct solution. To improve convergence, this method applies an augmented Lagrangian relaxation method. Its effectiveness demonstrated for a real power system.

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Recently, an ACC-CAES generating system has been developed by applying ACC (Advanced Combined Cycle) technology to a conventional CAES (Compressed Air Energy Storage) system. The ACC-CAES has a potential advantage of high efficiency and high capacity factor over other energy storage. However, advantages of it from the viewpoints of power system operation are not fully revealed because of its peculiar operation characteristics compared with the other energy storage. The characteristics include (1) it requires fossil fuel even in the case of operation using stored compressed air and (2) it has an ACC generating mode as one of its generating states to be used as a conventional ACC generating system while detaching the air storage system. Therefore, it is necessary to examine operation patterns of the ACC-CAES and its contribution to economic operation of a power system. In order to achieve the objective, operation simulations of a power system with ACC-CAES generating systems are needed because operation of energy storage systems such as the ACC-CAES must be studied through an operation scheduling of a power system. This paper develops an optimal daily scheduling method of a power system with both ACC-CAES generating systems and pumped hydro storage systems using two-dimensional dynamic programming. Sensitivity analyses are undertaken with the developed method; the results show that ACC-CAES generating systems tend to be operated as a peak or intermediate power source that bears some similarities to thermal plants or storage systems and, from an operation point of view, they have an economic advantage over pumped hydro storage systems.

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Local power systems (66kV) are served from the 275kV or 154kV substations. In order to maintain power supply reliability, the transmission lines are connected to several substations, and the operational configuration is radial. Since practical local power system has a number of transmission lines, many configuration candidates occur. It is expected to effectively evaluate these configuration candidates from various viewpoints such as reliability of power supply, transmission loss and so on. In this paper, the authors propose a multi objective evaluation method by using deterministic and probabilistic approaches for local power system configuration. In the proposed multi objective evaluation method, after selecting system configuration candidates which satisfy N-1 security by using an optimization method based on Boolean function, these candidates are evaluated from viewpoints of expected outage time, transmission loss and facility operation rate. In order to check the validity of the proposed method, numerical results are shown for a practical local system model with about 39 × 10²⁷ configuration

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We selected the way of “56V” system, which have the ability of high performance of section detected function, as the step out detection system for 500kV connective transmission line. Conventional “56V” system was using 4bit on transmission format of PCM relay. This time, we have developed new “56V” system which is using 2bit. It is confirmed that this 2bit system has the equal ability to 4bit system.
On the other hand, the “56V” system has the limitation to detect step out with high slip frequency or low voltage. We have developed combination system, which have the ability of section detected function of “56V” system and “56Z” system, and we confirmed the high performance of step out detection system by verification test of the system.

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The task of setting a protective relay requires various analytical calculations and coordination studies, and is thus complex and labor-intensive. While proposed conventional support systems are equipped with the required calculation functions, the systems are problematic with regard to practicability.
Our newly developed system not only integrates all required calculation functions based on a user-friendly GUI, but also dramatically improves system practicability mainly owing to the following developments:
· Functions which enhance the linkage between comprehensive calculation functions and the database
· Functions which automatically set parameters and execute standard-desirable fault calculations
· A relay-type-independent simulation method of protective relay sequence logic and a user maintenance function of the protective relay sequence database
This system presently performs network linkage operations in 22 locations of the Tohoku Electric Power Company, and has achieved great success in many respects with regard to the protective relay planning and operation, such as thorough relay operation analysis at the time of a power system fault.

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The present paper develops a numerical simulation method of steady-state and transient voltages and currents on a gas pipeline by applying a generalized circuit analysis program EMTP which is realized as a worldwide standard software. A buried gas pipeline is represented as an underground cable consisting of a tubular core and its outer insulator. The series impedance and the shunt admittance are easily evaluated by the EMTP supporting routine Cable Parameters. The paper has carried out simulations of steady-state and transient voltages and currents along the buried gas pipeline by EMTP. Based on the simulation results, it has become clear that the distributions of the voltages and the currents along the pipeline differ notably in the front and in the rear of a fault position. Thus, a detecting method is developed by observing a difference of a voltage amplitude between sound and fault states. The proposed techniques are investigated on real gas pipelines based on EMTP simulations, and it has been confirmed that the technique can be used in practice.

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This paper describes the electrical performance of a thermoelectric generating experimental equipment using a 200°C class fluid heat source. The experimental equipment is intended to use the waste heat of the phosphoric acid fuel cells for the hot side heat source.
A thermoelectric generating equipment using a 200°C class fluid heat source was experimentally manufactured, and the influence of the pressure applied to the modules on electric performance was examined.
The result is that the output power density tended to increase and the thermal contact resistance tended to decrease with the increase of the pressure applied to thermoelectric modules up to 0.5MPa. But the rate of increase in the power density tended to be saturated with the increase of pressure over 0.5MPa. At a pressure on modules of 1MPa, about 1.6kW/m² was obtained and the thermal contact resistance of one contact part was 2.5 × 10^-4 (m²K/W).

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In order to evaluate thermal interruption capability of gas circuit breaker, we consider that mass flow rate in nozzle throat at around current zero points is the most effective parameter, because it is closely related to the cooling capability of arc. In thermal puffer type gas circuit breaker, the mass flow rates depend not only on puffer pressure but also on gas passage structure. So using a calculation program of gas blast characteristics taking both arc energy and ablation gas into consideration, the relations between the mass flow rate at current zero points and gas passage structure were investigated. As the results, we found that shorter gas passage length greatly increases the mass flow rate at current zero points, although it does not influence puffer pressure formation so much. We also found that optimum cross sectional area of gas passage is a bit smaller than that of nozzle throat. If thermal interruption limit were determined by mass flow rate at current zero points, the shorter gas passage length and optimized cross section area will increase the SLF interruption capability of thermal puffer type gas circuit breaker.
This paper describes the detail of the results of simulations and discussions.

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This paper describes breakdown characteristics of an oil-pressboard insulation system to a superposition voltage of AC and DC voltages. Although AC electric field is decided by the ratio of the relative permittivity of a pressboard and insulating oil, DC electric field is decided by ratio α of volume resistivities. From the measurement in this study, 13—78 and 1.8—5.7 are obtained as the volume resistivity ratios α at temperature of 30°C and 80°C, respectively. The breakdown voltages against AC, DC, and those superposition voltages are surveyed to insulation models. In normal temperature, the breakdown voltage to the superposition voltage of AC and DC is determined by AC electric field applied to the oil duct. Since the α becomes as low as 2-3 at temperature of 80°C, AC and DC voltages almost equally contribute to the electric field of the oil duct as a result. That is, it became clear that superposed DC voltage boosts the electric field across oil ducts at operating high temperature.

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This paper deals with a power supply using switching modulation technique, and its application to the hot-line insulation diagnosis. One of the distinct features of the switching modulation techinque employed in this study is that the zero-phase-sequence voltage with arbitary frequency is generated easily in the three-phase power system. Basic composition is just to add a switching modulation device to the commercial power supply or charged indoor main line. Therefore, it is not necessary to feed a signal current from the signal power supply to the grounding conductor via a pouring transformer as required by current hot-line insulation diagnosis system.
When a power supply using switching modulation technique is used to hot-line insulation diagnosis, it is not necessary to modify or change existing commercial power facility. Therefore, there is a possibility that this may advantageously be used as a power supply for mobile type diagnosis. This paper deals with basic theory of switching modulation technique, and the phase rotation characteristics which play a basic role in three-phase power supply, and summarizes basic composition and performances of a trial manufactured experimental device. Furthermore, results of discussion are introduced concerning the conditions and method of its apllication to indoor wiring of fatories and buildings.

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In this paper we presented results of fundamental study to introduce the wavelet transform to vibration diagnosis for high-speed rotational machine such as steam turbine, gas turbine, and generator and so on. It is required to detect and distinguish typical vibration of high-speed rotational machine accurately in order to diagnose the machine. The wavelet transform is used in many fields because it is able to visualize phenomenon in time-frequency domain and to detect the beginning time and the duration of it.
We made a model rotor supported with two journal bearings to simulate contact vibration, clearance vibration, and oil whip. The vibration phenomena were measured with vertical and horizontal displacement meters at the rotor and vertical and horizontal accelerometers at the rotor bearing and visualized in the time-frequency domain by the wavelet transform. It is found that the dynamic spectra obtained by the wavelet transform of the vertical and horizontal components of displacement and acceleration signals are different for each vibration phenomenon, therefore, this method is able to distinguish each kind of vibration phenomenon. Each vibration phenomenon can be detected and distinguished at the early stage.

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Evaluation of lightning surge waveforms that actually enter into substations is important to rationalization of the test voltage of electric power equipment. The standard lightning impulse voltage (1.2/50μs) is used for factory tests. However, the actual lightning surge waveforms in substations are different from the standard lightning impulse voltage because they are complex and are usually superimposed with various oscillations. Insulation characteristics of SF₆ gas under such complex voltages have not been sufficiently clarified.
This paper deals with gap and spacer surface breakdown characteristics in SF₆ gas under sub-microsecond single pulses. The minimum breakdown voltages (V_min) under experimental waveforms are higher than V_min under the standard lightning impulse voltage. The evaluation method, which deals duration applied over 80% of peak voltage, can also estimate the insulation characteristics under single pulses with various conditions as well as oscillations.

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Evaluation of lightning surge waveforms that actually enter into substations is important to investigating the test voltage of gas insulated switchgear (GIS). The actual lightning surge waveforms in substations are different from the standard lightning impulse voltage because they are complex and are usually superimposed with various oscillations.
This paper describes insulation characteristics in SF₆ gas gap under the waveforms including oscillation (called waveforms B, C and D). The minimum breakdown voltages (V_min) under experimental waveforms are higher than V_min under the standard lightning impulse voltage. The evaluation method, which deals duration applied over 80% of peak voltage and conversion factor for second waves of waveform B, can estimate the insulation characteristics under waveforms B, C and D.

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