110 kV输电杆塔的多波阻抗建模与雷击暂态响应分析

为准确分析输电杆塔的雷击暂态响应,精确建立杆塔的波阻抗模型显得尤为重要。通过双锥天线原理,建立垂直单根圆柱导体的波阻抗公式;考虑实际杆塔的倾斜因素和修正系数,利用ANSYS Maxwell进行三维电磁场仿真,建立主架、斜材的波阻抗修正系数与分段长度、等效半径、主架上/下间距的关系,并推导出主架、斜材的波阻抗计算公式。为反映雷电波在呼高部分的传播过程,将呼高部分细分为5段并完成建模。针对典型的110 kV同塔双回输电杆塔,利用ATP-EMTP暂态仿真软件进行建模分析,结果表明精细化建模进一步凸显了雷电波在杆塔中的折反射过程,与Hara无损线塔模型相比,杆塔电位波形变化基本一致,横担电位上升速度减慢,提前到达峰值且峰值降低,C相横担峰值相差9.6 %,峰值时间超前了0.023 μs,反映出了呼高部分的波过程以及对整个雷击暂态响应过程的影响。     

Results of lightning impulse tests for a 275‐kV full GIS substation

This paper describes the outline and results of the lightning impulse tests for a 275‐kV full GIS substation. The behavior of lightning surges is a very important factor for the rational design of substations and low‐voltage and control circuits inside the substations. For the above reason, we carried out lightning impulse tests for a new 275‐kV full GIS substation. In these tests, we measured voltage induced in low‐voltage and control circuits, transient characteristics of grounding grid, injected voltage and current waveforms, and so on. By investigating these data, we confirmed the behavior of lightning surges inside the substation. We also compared simulated waveforms by EMTP analysis with the measured waveforms. The simulated results agreed well with the measured results. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 46–58, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10230     

A wave‐front‐time dependent corona model for transmission‐line surge calculations

For transmission‐line surge studies, the inclusion of corona discharge due to high voltage surges is important as well as the inclusion of frequency‐dependent effects. Because the charge‐voltage (q‐v) curve of a lightning surge is different from that of a switching surge, a corona model should reproduce different q‐v curves for different wave‐front times. The present paper proposes a wave‐front time dependent corona model which can express the dependence by a simple calculation procedure as accurately as a rigorous finite‐difference method which requires an enormous calculation time. The simplicity enhances the incorporation of the corona model into a line model, because a large number of models are to be inserted into the line model by discretization. The q‐v curves calculated by the proposed method agrees well with field tests. This paper also proposes an efficient method to deal with nonlinear corona branches in distributed‐parameter line model using the trapezoidal rule of integration and the predictor‐corrector method. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 29–38, 1999     

Full range analog Wheatstone bridge‐based automatic circuit for differential capacitance sensor evaluation

In this paper, an integrable novel fully analog Wheatstone bridge‐based interface for differential capacitance estimation is presented. Its working principle takes advantage of the modified De‐Sauty AC bridge configuration being employed only by two capacitors and two resistors. A feedback loop controls one of the resistors (e.g. a voltage‐controlled resistor), to obtain an evaluation of the differential capacitance variation on a full range, thanks to a general but very simple formula that considers both the ‘auto‐balancing’ and the bridge ‘out‐of‐equilibrium’ ranges. The proposed interface shows a satisfactory accuracy, being the percentage relative error within 0.45% for the experimental results. Copyright © 2016 John Wiley & Sons, Ltd.     

Equivalent circuit models using CPE for impedance spectroscopy of electronic ceramics

Complex immittance (Impedance Z, Modulus M, Admittance Y, Permittivity ?) spectra for some equivalent circuit models involving resistances, capacitances and constant phase angle elements (CPE) are calculated for different ratios of the parameters. A comparison of experimentally obtained complex immittance plots with these diagrams greatly facilitates the search for the most appropriate equivalent circuit representing the electrical properties of electronic ceramics. An equivalent circuit for Ba_1-xSr_xTiO₃ (x = 0.35) ceramic system is developed by using these simulated plots.     

Modeling method of fast transient for unsymmetrical stray capacitance to ground

Transient characteristic of power system apparatus in a high‐frequency region should be modeled with stray capacitors. Pi‐type circuit is commonly used to represent the stray capacitors between terminals and those to the ground. A modeling method for the pi‐type circuit with unsymmetrical stray capacitances to ground is proposed in this paper. To obtain the unsymmetrical stray capacitances to ground, a couple of differential‐mode measurements are interchangeably applied. The parameters of the pi‐type circuit can be determined by the measurements with a common‐mode measurement. A nonlinear least‐squares method is used to estimate the capacitances. The method is applied to compose an equivalent circuit of a miniature circuit breaker (MCB), which has unsymmetrical stray capacitances to ground. The application is not only for the MCB but also for a scaled model of a high‐voltage circuit breaker. A gas‐filled arrester is used as a voltage sensor for the test because the voltage across the stray capacitor cannot be directly measured due to the input capacitance of a voltage probe. A transient response of the MCB with the gas‐filled arresters is numerically simulated to show the usefulness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

变压器绕组变形的扫频短路阻抗法研究

针对变压器因绕组变形而产生故障问题,分析了现有短路阻抗法和频响法检测绕组变形手段的特点和不足,研究了扫频短路阻抗法的基本原理和测试接线方式,在模型变压器上进行了绕组层间短路、绕组匝间短路等不同情况的试验测试,初步验证了该方法的有效性。以某220 kV变压器为测试对象,采用扫频短路阻抗法进行了变电站现场测试工作。该方法测试结果能够提供更多的测量参量,为绕组变形的研判提供了更多的参考依据,是一种很有价值的变压器绕组变形测试方法。     

Development of a contactless measurement method for transmission line surge voltage waveform

This paper proposes a contactless method to measure a surge voltage waveform on an overhead transmission line and on a cable sheath enclosed in a corrosion‐proof layer. To measure surge voltage and current waveforms on the overhead line, the method is based on electromagnetic coupling between the overhead line and a surge sensor, composed of a closed loop which is a distributed parameter line. The surge waveform is estimated from the induced voltage to the closed loop and from a Z‐parameter theory. To measure the cable sheath voltage waveform, the method is based on electrostatic coupling between the sheath and a detecting electrode, which is portable and detachable, and is composed of quite simple components, and its potential dividing ratio is adjustable using a lumped capacitor. The proposed method is inexpensive, is easy to measure surge waveforms with reasonable accuracy, and also is applicable to surge measurement on a live line because of its contactless nature. © 2001 Scripta Technica, Electr Eng Jpn, 136(1): 9–15, 2001     

An architecture of small‐scaled neuro‐hardware using probabilistically coded pulse neurons

In this paper, we present an architecture for neuro‐hardware that can be realized in circuits of far smaller scale than in the conventional approach. In order to reduce the scale of the circuits, the architecture employs a new method of computing the membrane potential and the sigmoidal function by encapsulating the probabilistic properties into the relative delay between two pulses. The proposed architecture makes it possible to integrate more than 100 neurons in the latest FPGA chip, which is a 13‐fold miniaturization compared to the conventional architecture. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 48–55, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.1168     

Poles–zeros analysis and broadband equivalent circuit for on‐chip spiral inductors

Poles and zeros of the transfer function determine the performance and the key features of the circuit network, such as phase, gain, and bandwidth. In this paper, the contribution of the poles and zeros to the transfer function has been shown. The factors η_p and η_z are proposed to account for the poles contribution to the peak and the zeros contribution to the valley of transfer function, respectively. A novel broadband equivalent circuit combining the physics‐based circuit model and behavioral macro‐model (black‐box) network is proposed for accurately characterizing on‐chip spiral inductors. The physics‐based elements are extracted using the linear dependence of a set of characteristic functions on variables (such as ω²) or other functions in a certain frequency range. The macro‐model network described by rational functions is determined using vector fitting approaches. The proposed modeling method is validated by the on‐chip spiral inductor fabricated with 0.13‐µm SiGe BiCMOS aluminum process. Excellent agreements are obtained between the measured data and calculation for the proposed model up to 40 GHz. Copyright © 2015 John Wiley & Sons, Ltd.     

Higher‐order CN‐FETD method for analysis of microwave circuit structures

In this paper, the hierarchical high‐order basis functions on tetrahedrons are introduced to the Crank–Nicolson (CN) finite‐element time‐domain (FETD) with the 3D Maxwell equations for analysis of the microwave circuit structures. Whitney 1‐form high‐order hierarchical basis functions are used to expand the electric field and Whitney 2‐form high‐order hierarchical basis functions for the magnetic field. The CN scheme is employed in the FETD method to lead to an unconditionally stable algorithm. Numerical results were presented to demonstrate the accuracy and efficiency of the proposed high‐order CN‐FETD method. Copyright © 2012 John Wiley & Sons, Ltd.     

An inverse‐time low‐impedance protection design for feeders in active distribution networks

One of the major issues associated with active distribution networks (ADNs) is to devise an appropriate protection scheme that works successfully in different operation modes. This paper describes the design of an inverse‐time low‐impedance (ITLI) protection scheme with the aid of the advanced measurement technologies in ADNs. The scheme detects faults and calculates tripping time by using the magnitude ratio of the maximum load impedance to the measured impedance. ITLI protection is immune to varying fault current caused by the flexible operation modes and able to automatically adjust fault‐tripping time according to the fault severity. With the existing communication infrastructures, an event‐triggered adaptive setting scheme updates the settings of ITLI relays in real time. The setting method not only enhances the detecting capability but also provides higher reliability and sensitivity before, during, and after events in ADNs, such as tap position adjustment, DGs fluctuation, and network structure change. Besides, an acceleration method based on the definite‐time grading technique is presented to reduce the impact of infeeds and fault resistance. The effectiveness of the proposed protection scheme is demonstrated in a 12.47‐kV active distribution network established by PSCAD/EMTDC. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Determination of equivalent circuit constants of synchronous machines from the extended Dalton‐Cameron method

This paper presents a method of determining the equivalent circuit constants which accord with the physical construction of synchronous machines, using the dc decay testing method with the rotor in arbitrary position (proposed by the authors and called the extended Dalton–Cameron method). The conventional Dalton–Cameron method calculates the direct‐ and quadrature‐axis subtransient reactance from a standstill response test in any arbitrary rotor position using a single‐phase power supply. The extended Dalton–Cameron method determines the direct‐ and quadrature‐axis operational impedances for each slip from a standstill response test using a small‐capacity dc power supply. The direct‐ and quadrature‐axis operational impedance loci thus obtained synchronous machine constants (subtransient, transient, and synchronous reactances) are used to estimate the direct‐ and quadrature‐axis equivalent circuit constants which accord with the physical construction of synchronous machines. As an example, equivalent circuit constants are determined for a 10‐kW laminated salient‐pole‐type synchronous machine with damper winding. The validity of the equivalent circuit constants is confirmed by comparing the calculated resistance and leakage reactance of the field winding determined from the operational impedance when the terminals are short‐circuited, to those when the terminals are connected to an external resistance. © 2001 Scripta Technica, Electr Eng Jpn, 138(1): 56–67, 2002     

An electromagnetic transient simulation model of grid‐connected inverters for dynamic voltage analysis of distribution systems

Transient analysis is an indispensable tool for analyzing the voltage fluctuation of distribution systems according to the penetration of distributed generations with grid‐connected inverters. Electromagnetic transient (EMT) analysis is suitable for the purpose because it enables detailed modeling of the inverters and accurate simulation of their dynamic behavior. However, the EMT analysis requires a smaller calculation time step by a factor of 500 if the simulated power system includes the inverters. Simulation of the inverters is a bottleneck in speeding up the EMT analysis. This paper proposes a novel average‐value modeling method for the grid‐connected inverters. The proposed inverter model operates in a larger calculation time step, and speeds up the EMT analysis of distribution systems containing the inverters. The maximum error in the output power was 8% compared to the result by the conventional model. Dynamic voltage simulations are demonstrated with a test case, which includes tap changing transformers with a voltage controller and a photovoltaic generation facility. The proposed model reduces the required calculation time by a factor of 754 compared to the conventional model whereas there is no significant difference in the simulated result.     

Exact sampled‐data analysis of quasi‐resonant converters with finite filter inductance and capacitance

Previous models of quasi‐resonant converters generally use averaging and assume infinite filter inductance and capacitance to reduce circuit complexity, but at the expense of accuracy. In this paper, exact sampled‐data modelling is used. A general block diagram model applicable to various topologies of quasi‐resonant converters is proposed. Large‐signal analysis, steady‐state analysis and small‐signal analysis are all studied. They agree closely with the experimental results in the literature. Compared with the averaging approach, the sampled‐data approach is more systematic and accurate. Copyright © 2001 John Wiley & Sons, Ltd.     

Characterization of deep levels in Si‐MOS structure using ICTS measurement

Interface traps and bulk traps induced by heavy metal impurities in Si‐MOS structure were characterized by isothermal capacitance transient spectroscopy (ICTS). In addition, the use of an MOS inversion time is proposed for the detection of a very low density of heavy metal impurities in the ICTS measurements. It is shown that heavy metal impurities enhanced interface trap densities as well as induced bulk traps. The degree of the enhancement varies with the species of heavy metal impurities. Interface traps may be enhanced by the substitutional heavy metal impurities. Moreover, it has been ascertained that a very low level of contamination by heavy metals can be detected by using the MOS inversion time. This has been experimentally shown by the use of a copper impurity. Furthermore, it has been clarified from the change of MOS inversion time that interface traps are also detrimental to the carrier generation lifetime. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 76–86, 2000     

An experimental study of lightning overvoltages in wind turbine generation systems using a reduced‐size model

Wind turbine generation systems are built at locations where few tall structures are found nearby so as to obtain good wind conditions, and thus, they are often struck by lightning. To promote wind power generation, lightning‐protection methodologies for such wind turbine generation systems have to be established. This paper presents the result of an experimental study of lightning overvoltages in wind turbine generation systems using a reduced‐size wind turbine model. Overvoltages observed at wavefronts of lightning surges are focused on in this study. In the experiments, lightning strokes to one of the blades and to the nacelle were considered, and voltages and currents at various positions of the wind turbine model were measured. The following points have been deduced from the results: (i) The voltage rise due to the tower footing resistance can cause a significant voltage difference between the tower foot and an incoming conductor led from a distant point. Also, a voltage difference between the bottom of down conductors installed inside the tower and an incoming conductor can be of significance. (ii) The lightning current flowing through the tower body induces voltages in main and control circuits which form loops, and the induced voltages can cause overvoltages and malfunctions. (iii) Traveling‐wave phenomena in a wind turbine generation system for a lightning strike to the tip of a blade and to the nacelle have been clarified from the measured waveforms. This information can be used for developing an EMTP simulation model of wind turbine generation systems. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 22– 30, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20466     

Development of gate drive circuit for next‐generation ultrahigh‐speed switching devices

This paper describes a gate drive circuit which is capable of driving an ultrahigh‐speed switching device and of suppressing high‐frequency noise caused by its high dV/dt ratio of 104 V/μs order. SiC (silicon carbide)‐based power semiconductor devices are very promising as next‐generation ultrahigh‐speed switching devices. However, one of their application problems is how to drive them with less high‐frequency noise without sacrificing their ultrahigh‐speed operation capability. The paper proposes a new gate drive circuit specialized for such devices, which charges and discharges the input capacitance of the device by using an impulse voltage generated by inductors. This ultrahigh‐speed switching operation causes a high‐frequency common‐mode noise current in the gate drive circuit, which penetrates an isolated power‐supply transformer due to the parasitic capacitance between the primary and the secondary windings. In order to overcome this secondary problem, a toroidal multicore transformer is also proposed in the paper in order to reduce the parasitic capacitance drastically. By applying the former technique, the turn‐on time and turn‐off time of the power device were shortened by 50% and by 20%, compared with a conventional push‐pull gate drive circuit, respectively. In addition, the latter technique allows reduction of the peak common‐mode noise current to 25%, compared with the use of a conventional standard utility power‐supply transformer. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 52–60, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21124     

Electromagnetic analysis coupled with motion for high‐speed circuit breakers of eddy current repulsion using the tableau approach

Electromagnetic field analysis coupled with motion using the tableau approach has been applied to high‐speed circuit breakers of eddy current repulsion mechanisms. This breaker has an opening time of 1 ms and break time less than 1 cycle (20 ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. The mechanisms are composed of two fixed coils and one repulsion plate. A numeric experiment has been applied to investigate the dynamic behavior of the electromagnetic repulsion mechanism using the equivalent circuit method. Calculation results were in good agreement with both measurement results and calculation results by FEM on an experimental model. In addition, repulsive forces depending on material conductivities have been researched. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 8–16, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20149     

Test circuit of impulse spark‐over voltage with different rates of rise for gas discharge tubes

The impulse spark‐over voltage of the gas discharge tube (GDT) is strongly related to the rate of rise (RoR) of the voltage. At present, due to the convenience of the test instrument, conventional impulse waveforms, such as 1.2/50 and 10/700 μs, are often adopted to conduct such kind of test for GDT. It has been found that these waveforms are able to generate valid waveforms only with limited RoRs and relatively narrow valid voltage ranges. This paper deals with a simple series RC circuit to test the GDT's impulse spark‐over voltage using a ramp voltage, which is approached by an initial portion of a steeply rising voltage impulse whose normal peak value is several times the breakdown voltage of the GDT. The basic circuit theory is described, and the RoR of the output voltage is correlated with the circuit parameters. Moreover, the series RC circuit in this paper is found to be able to deliver a ramp voltage with more consistent RoR than an RLC circuit. The results in this paper provide some suggestions for the revision of relevant standards (e.g., ITU‐T K.12 and IEC 61643‐311). Circuit parameters for different RoRs ranging from 100 V/μs to 1 kV/ns are also established. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.