This paper shows current status and tasks in development of cable recycling technology and it’s items to be solved. Electric cable recycle system has been activated especially for copper conductor recycle in Japan. Previously removed cable coverings materials were mainly land filled. But landfill capacity is decreased and limited in recent years, at the same time, recycle technology was highly developed. A cable recycle technology has 4 tasks. (1) Applying new high efficiency separation system instead of electrostatic and gravity methods to classify mixed various kind of plastics materials including recently developed ecological material (ex PE, PVC, Rubber), (2) Removing heavy metal, especially lead from PVC material, (3) Treatment of optical glass fiber core, which has possibility going to be harmful micro particles, and (4) Establishment of social recycle system for electric wire and cable. Taking action for these tasks shall be proceeded under environmentally sensitive technology together with local government, user, manufacturer, and waste-disposal company on cost performance basis.
We propose a new protection relay system for selective and quick disconnection of fault area in a distribution system, which can be flexibly adopted for a large-scale introduction of distributed generators (DGs). When a fault occurs, a relay provides a binary signal which is activated if, for instance, its current exceeds a certain value. Each relay cannot locate the fault point with only its own signal. By utilizing signals from other relays together with its own signal, each relay can locate the fault, and then disconnect the DG if necessary. Because only a binary state signal is transmitted instead of the actual physical variable, the network traffic is much less than the case where the conventional protection system for a transmission system is applied to a distribution system. The followings are main results of a simulation on our proposed protection system: (1) the proposed protection system can successfully disconnect only a fault feeder,when all relays connected to the feeder use signals provided from the feeder sending-end and all other DGs on the same feeder, (2) in the case of the fault on a DG connected feeder, the DG can be disconnected within 60 msec.
Recently, the evaluation of control performances of interconnected power systems has become an important issue with respect to individual load frequency controls. Several performance measures are in practical use such as Area Control Error (ACE), Mutual Aid Criterion (MAC) and Control Performance Standard (CPS). Area Requirement (AR) is alternative expression for ACE, where AR = -ACE. However, the characteristics of these indices have not been sufficiently studied as far as the authors know. Specially, this is the case for their dynamic behavior against random load disturbances. This paper investigates the performance index, AR, through analysis of two-area systems. Major dynamic elements of interconnected systems affecting the frequency are taken into account to investigate responses of the system against load disturbances. The analysis shows that, when two systems are interconnected, the smaller system tends to require more effort of control against load disturbances to keep the same value of the performance indices.
This paper describes an evaluation of kW value with an analysis of measured data of photovoltaic power systems for houses. The kW value indicates the capability of power stations at the large electric power demands. If the PV system has a large kW value, the capacity of thermal power station to meet with the peak demand is reduced. A new method, K90 is proposed to estimate the kW value of the PV system. With the measured data of the PV system, K90 method is evaluated. Besides, the modified duration curve is considered to investigate the actual effect of the PV system on the peak demand for the thermal power plants. Finally, an appropriate kW value of the PV system is estimated.
It is necessary to consider the TEM-mode, the higher TE and TM-mode and resonance phenomena in GIS to describe the propagation and detection characteristics for partial discharge measured with the UHF-method. Measurements on the non-reflection coaxial wave-guide simulating GIS were carried out with changing installation and shape of UHF sensor and wave-guide length. This paper describes the output characteristics of UHF sensor above cut-off frequencies, when reflection and resonance phenomena are taken into account. In the frequency region above the cut-off frequencies of the TE11 mode, the output characteristics of UHF sensor shows resonant by reason of the electromagnetic reflection of TE mode at the both ends of wave-guide. At the resonant frequency, the output characteristics of UHF sensor are different by wave-guide length, shape of sensor and sensor installation, distance from end of tank, angle at circumference. The resonant frequencies are function of tank-length and cut-off frequency of tank, and expressed with equation of cylindrical cavity resonator.
For the purpose of mitigating carbon dioxide emissions, three renewable energy transportation systems are proposed in which methanol is synthesized by use of wind power generation energy at an oversea and is transported to Japan to be used for a power generation. The proposed systems are the following three systems: (1) wind energy and captured CO2 utilization system, (2) wind energy and coal utilization system, and (3) wind energy and biomass utilization system. The characteristic and cost of the proposed systems’ components such as a wind power generation and a methanol synthesis plants are investigated, and so are the energy and carbon flows of the systems, assuming that the wind power generation plant is constructed at the eastern coast of Russia. Major indicators such as energy efficiency, methanol cost, CO2 reduction cost, etc., of the proposed systems are evaluated together with those of a similar CO2 recycling system utilizing hydraulic power. On the basis of the evaluation results, the wind energy and biomass utilization system is shown to be the most excellent among the evaluated systems from the viewpoints of the CO2 reduction cost. When LNG cost is increased, its estimated CO2 reduction cost islower than that of a CO2 recovery system adopted to a conventional LNG-fired power plant. Consequently, the proposed system is expected to be a feasible option for CO2 reduction in the near future when the wind power generation cost is much decreased.
We have developed a simultaneous control design method for multiple power system stabilization controllers such as PSSs using the system identification and the non-linear numerical optimization technique. The developed controller design can take into consideration of controller structure and several design constrains in the controller design. For multiple controllers design, a reduced order MIMO linear system, which show similar dynamic properties to some original full order power systems, is identified from time domain simulation results by N4SID algorithm. The non-linear optimization technique is applied to minimize the Modal Performance Measure, which is directly related with damping of the power system oscillations. As an example of the design, PSSs design for IEEJ EAST30 system model is described.
This paper presents and analyzes a new simple instant-estimation method for time-average quantities such as rms-values of voltage and current, active and reactive powers, and power factor for single-phase power with the fundamental component of constant or nearly-constant frequency by measuring instantaneous values of voltage and current. According to the analyses, the method can instantly estimate time average values with accuracy of the fundamental frequency, and estimation accuracy of power factor is about two times better than that of voltage, current, and powers. The instant-estimation method is simple and can be easily applied to single-phase power control systems that are expected to control instantly and continuously power factor on a single-phase grid by inverter. Based on the proposed instant-estimation method, two-methods for such power control systems are also proposed and their usefulness is verified through simulations.
One of important problems to be solved in Japanese trunk transmission systems is the reduction of short circuit capacity. As this countermeasure, double buses are split into two buses in some substations. In recent years, dispersed generators are introduced in lower voltage classes due to the introduction of the electricity deregulation. In such a distribution system as many dispersed generators are introduced, it is a possibility that the fault current becomes beyond the breaking capacity at the occurrence of short circuit. Introduction of superconducting fault current limiters into a power system is very effective as one of the means to solve the above-mentioned problem, and we have studied on the effective introduction method of them and setting method of their parameters. This paper describes the results of the operation tests for SN transition type of a superconducting fault current limiter using 3 phases of FCL modules against various kinds of system faults or inrush current in the Power System Simulator installed at CRIEPI.
Transient responses of a closed loop MHD experimental facility from non-power generation to power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. For the long-time continuous power generation experiment, the time required to obtain the steady state for the power generation is estimated to be approximately 20 hours. By increasing the electrical input power to the heater as an exponential function of time, the temperature increment of ceramics can be moderated. When the duration of the experiment is around 10 minutes, argon gas temperature at the exit of the heater hardly changes because of the large heat capacity of structure materials. It is found that the fluid disturbances are induced at the instant of the power generation and they propagate as they repeatedly reflect at the sudden change of duct shape. Since all the induced disturbances attenuate approximately 0.4 seconds after the power generation, the time scale that the disturbances exist in the facility is estimated to be 1 second at largest.
This paper achieves a feasibility study of a 6.6kV, 1MW loop controller that consists of a transformerless back-to-back configuration using two 5-level diode-clamped converters. However, the loop controller requires reducing the zero-sequence current circulating between the two distribution lines below than 0.2 A in rms, in order to avoid malfunction of line-to-ground fault protection relays. Moreover, all the dc voltages across four capacitors in the dc link have to be controlled equally. This paper presents a solution to these problems. Two common-mode chokes are installed at the ac side of each converter to suppress high-frequency zero-sequence currents, while feedback control is applied to eliminate low-frequency zero-sequence currents. Two bidirectional buck-boost dc-dc converters are employed to keep the four capacitor voltages equal. Simulation results verify viability and effectiveness of the loop controller, along with the developed theoretical analysis.
Trapped field characteristics are one of the key factors in the application of high-temperature superconducting bulk, such as magnetic levitation systems, motors, bulk magnets and so on. The immutable trapped field is required in superconducting bulk applications as a quasi-permanent magnet, however, the trapped field is influenced and changed by a time-varying external magnetic field in a realistic operational environment of electrical devices. This means that shielding current distribution within the bulk is changed by the time-varying magnetic field and the transient magnetic flux movement results in temperature rise and finally reduction of the trapped field. In this study, we observed the abrupt reduction of the trapped field for the external AC magnetic field in the range of frequency up to 50 Hz. And we also performed the numerical simulation using a newly developed computer program based on the finite element method (FEM). In the simulation program, the voltage-current (E-J) characteristics, which depend on the irreversibility temperature are taken into account. From these results, it can be considered that the abrupt reduction of the trapped field is caused by the temperature rise due to AC loss.
The authors have investigated insulation diagnostic technique for gas-insulated switchgear (GIS) by detecting partial discharge (PD) signals, particularly PD current, PD-induced electromagnetic wave and AE signal. So far, we have experimentally shown that discharge type such as streamer and leader-type discharge can be discriminated by introducing an amplitude ratio of the positive peak value to the negative one of the first-incoming electromagnetic wave with UHF method in the 66kV model GIS. In this paper, we investigate the influence of GIS tank size on propagation properties of PD-induced electromagnetic wave by finite difference time domain (FD-TD) method to derive a criterion to discriminate discharge type. From the calculated results, we discuss the influences of GIS tank size and sensor position on discrimination of discharge type in terms of risk assessment of GIS with focusing on the influence of higher TE modes, especially TE11 mode, of propagating electromagnetic wave.
Aluminum, a main conductive material for overhead transmission lines, has excellent resistive property against corrosion in normal environment as far as its stable skin is not broken. However there are so many lines going through coastal and/or industrial areas where corrosive particles tend to occur. Under such circumstances the conductors filled with the grease among those wire layers have been generally adopted as an anti-corrosion measure. But corrosive circumstances have been getting severer to overhead lines in the last decades and there might be some cases in future that even the conventional measure does not enable to acquire sufficient effect against corrosion. Therefore, improvement of corrosion resistance of a conductor must be one of the most significant themes in order to obtain the higher reliability of overhead transmission lines at this stage. We successfully developed a new anti-corrosion overhead line conductor realizing much effectiveness against the acid atmosphere and/or rain as well as salty circumstances in the coastal area.
A method to interface linear subsystem model to main power system is shown. First a local reference angle of subsystem is extracted as a linear combination of state variables of the subsystem model. Second the subsystem model is transformed into a quasi-linear form having phasor quantities as its input/output variables. The quasi-linear form can be interfaced to main system within I = YV-type network solution.
PLL is used to synchronize the phase of an inverter AC output with that of an utility AC. The dynamic PLL behavior must be accurately simulated for it governs the control performance of an inverter. The VCO part of a PLL conventionally consists of an integrator, which is reset at the instant when it exceeds 2π. A numerical simulation, such as an EMTP simulation, with a fixed time step calculation cannot detect these accurate reset timings. This inconsistency in reset timing induces a phase jitter. The phase error, due to jitter, becomes a severe problem when a large time step is employed to simulate long period phenomena, and the inverter is modeled by the state-space averaging method. This paper proposes a jitter less VCO model for EMTP simulation. The phase jitter of the proposed VCO model is completely suppressed, regardless of the time step length. The improvements are confirmed through EMTP simulations.
The relation between the turbine shaft torque and the improvement effect of power system stability, in the case of reclosing operation, is examined in this paper. The reclosing operation is carried out, when the fault occurs on the transmission line. Until now, we have reported that the system stability is improved by the timing of the reclosing operation by taking account of the values of generator variables. And, the introduction of the fault current limiter has been proposed in order to suppress the fault current with the transmission line fault. On this limiter, we have already reported the improvement effect of power system stability. The correlation on turbine shaft torque and the improvement effect of power system stability is reported by the computer simulation, when the two methods used.
This paper presents a new approach to optimal voltage and reactive power control based on a genetic algorithm (GA) and a tabu search (TS). To reduce time to calculate the control procedure, the parallel computation using Linux is executed. In addition, TS and GA are calculated by the master and each slave based on the parallel program language. The effectiveness of the proposed method is demonstrated by practical 118-bus system.