Characteristics of lightning surges observed at 77 kV substations

In order to improve power supply reliability, it is necessary to prevent lightning faults in transmission lines and substation apparatus. However, faults are caused occasionally in lower-voltage power systems, particularly at the 77 kV level. The governing factor for insulation strength of substation apparatus is the lightning impulse voltage, and it is necessary to know the voltage level and distribution in a substation caused by lightning surges in order to investigate rational insulation coordination. For this purpose, the authors measured lightning surges at two 77 kV conventional substations from 1990 to 1993. In this paper, the characteristics of induced lightning surges and back flashover lightning surges are described. Comparisons of related surge voltages at two substations, the power line phases in grounding faults, and the equivalent capacitance of the substations are also discussed.     

基于等值老化容抗的变压器油纸绝缘状态评

针对频域介电谱特征量难以定量分析变压器油纸绝缘老化状态的问题,提出应用等值老化容抗定量分析油纸绝缘老化状态的评估方法。首先,采用回复电压特征量构建变压器绝缘系统等效电路。然后,分析扩展德拜等效电路参数与频域介电谱的内在联系,研究时-频域介电谱相互转化的可行性。最后,通过仿真分析等效电路参数变化对复电容实部谱线的影响规律,定量分析等值老化容抗与主时间常数的关系。研究结果表明：等值老化容抗与主时间常数具有指数函数关系,当等值老化容抗越小时,变压器油纸绝缘老化越严重。由主时间常数与变压器绝缘老化状态关系可划分不同的变压器绝缘状态所对应的等值老化容抗范围,为准确评估变压器油纸绝缘老化状态提供新的参考依据。     

用同步发电机突然短接现象的分析设计大容量真空断路器

本文着重介绍了用超导体线圈磁链不变原则下,对发电机出口端突然短接和ψ0=0时的分析。超瞬变和瞬变的电抗、突然三相短接电流、电抗Xd′′和Xd′的数值,两相和单相突然短接的电流以及突然短接的时间常数作了详细的阐述。可作为设计大容量真空断路器的参考。     

A method of predicting transient constants of synchronous machines

It is difficult to determine the subtransient (transient) reactance and subtransient (transient) short-circuit time constants of medium and large synchronous machines by the sudden three-phase short-circuit test because large-capacity equipment is required. This paper describes a new method of measuring these constants by means of a simple test using a small dc power supply. The key points of this method are as follows. (1) A dc voltage is applied to the armature winding (two terminals with the third one open) of a stationary synchronous machine through a resistance. When the two terminals are closed, the winding is short-circuited and the current in the armature winding decays. The whole process of decaying current is recorded. (2) The value of the transient phenomena of the winding calculated from circuit equations (armature, field winding and damper winding circuits) is compared with actual data, and the unknown equivalent circuit constants are identified by the least squares method. (3) Transient phenomena of the sudden three-phase short-circuit are calculated by the two-reaction theory using identified constants, and, hence, these constants are calculated. The transient constants of synchronous machines obtained by the new method agree closely with the observed values.     

考虑杆塔等效半径变化的高杆塔雷击暂态特性分析

分析雷击输电线路杆塔时的暂态特性,对输电线路上电气设备的绝缘配合设计具有重要的指导意义。在国内外已有波阻抗杆塔模型的基础上,考虑高杆塔主体和呼高部分随高度的减小而等效半径增大,使得各部分波阻抗值减小的情况,对高杆塔进行细分,仿真研究高杆塔多波阻抗模型的分段数对雷电波传播的影响。通过比较和分析不同段时雷电流波形、雷电流幅值及接地电阻对杆塔雷击暂态特性影响,得出若对高杆塔主体进行细分段,则有其上过电压降低,暂态过程较长的结论。     

A Strategy for Analysis and Modelling of Impedance Spectroscopy Data of Electroceramics: Doped Lanthanum Gallate

Modelling of impedance spectroscopy (IS) data of electroceramics depends critically on the correct choice of equivalent electrical circuit so that the extracted parameters have physical significance. The strategy proposed to choose the correct circuit involves analysis of IS data in several of the four complex formalisms: impedance, electric modulus, admittance and permittivity together with consideration of the frequency and temperature dependence of data and the magnitude and temperature dependence of extracted resistance and capacitance values. This is demonstrated using IS data from oxide-ion conducting La_0.80Sr_0.20Ga_0.83Mg_0.17O_2.82 ceramics over the range 182 to 280°C. Low temperature data are fitted first, to allow a full characterisation of the bulk response; some of the bulk parameters may then be fixed to enable fitting of the higher temperature data which increasingly feature lower frequency phenomena such as grain boundary impedances. The most appropriate circuit in this case is found to consist of a parallel combination of a resistor, capacitor and constant phase element (CPE) for the bulk response in series with a resistor and capacitor in parallel for a constriction resistance. The origin of the constriction resistance may be associated with the presence of plate-like LaSrGaO₄ secondary phase within the grains and/or with the presence of pores at the grain boundaries. The importance of choosing (a) the correct equivalent circuit and (b) approximately correct input values for the various circuit parameters to be fitted and refined are demonstrated.     

雷击引起的高压断路器故障分析

近年来电网中高压断路器遭雷击引起的故障时有发生且成上升趋势。笔者分析了雷击引起的高压断路器故障:故障与断路器本身有一定的关系,但还受到变电站绝缘配合技术原则的影响。探讨了断路器的性能、现行有关标准和规程的适用性,得出解决故障可采取的措施:在断路器的进(出)线侧安装避雷器,如变电站内无安装位置的话,可在线路终端塔上安装带间隙的线路避雷器。     

一起220 kV SF6断路器爆炸事故的原因分析及仿真计算

针对广东500 kV北郊站220 kV北石乙线开关爆炸事故,利用ATP-EMTP软件进行了仿真计算,计算结果表明:事故可能是由连续雷击造成的,北郊变电站的输电线进线段不设防(未装避雷器)是重要原因之一,北郊变电站线路侧无避雷器保护,断路器在开关断开的情况下难以抵御雷电侵入波,因而造成北郊变电站断路器发生爆炸。     

Surge impedance of independent transmission towers characterized by the direct method

Measurement of the surge impedance of a transmission tower by the direct method is studied with the help of NBC-2. The arrangement of the measuring wires in the experiment influences the result, and it is possible to correct the measured tower surge impedance to that for a standard arrangement with a vertical current injection wire and a horizontal voltage measuring wire. By reviewing various experimental results in this way, it is concluded that an independent double-circuit transmission tower has an impedance of about 150 Ω with the traveling wave speed in the tower being equal to that of light. This value can be applied to the case of a direct lightning hit on the tower top, regardless of the type of lightning, upward or downward. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 17–24, 1998     

超磁致伸缩致动器的等效电路研究及驱动波形设计

针对超磁致伸缩致动器由于大电感线圈的存在而使电流上升时间较长,以致于无法满足快速开启需求的问题,分析了致动器等效电路以计算精确的线圈电流,并设计了较为合理的驱动电压波形。从对致动器阻抗的描述精度出发考察3种等效电路,确定了带并联电阻的等效形式最为合理;分析计算了该种等效形式下方波电流输入时的电流表达式,得到不同频率下致动器电流瞬时响应,并通过实验测试了致动器阻抗以及电流瞬时值以验证等效电路的准确性。最后基于该等效电路,借鉴电磁阀的大电压开启方法,分析了合理的电压形式并提出了参数设计方案,计算结果表明,设计电压能在保证较小超调量的同时有效地降低电流调整时间。     

Characteristics of an induction motor with reduced turns of terminal coils

The use of PWM inverters with high switching characteristics for the adjustable speed drive system causes an overvoltage with steep‐fronted waveform on the motor terminals. As this steep‐fronted transient voltage in inverter drive loads heavily on the terminal coils of motor winding, the insulation failure in the motor winding occurs mostly on the terminal coils. Therefore, it is reasonable to reduce the turns of terminal coils only and to increase the dielectric strength of interturn insulation. This paper presents a comparison of measured characteristics of normal induction motors and induction motors with reduced turns of terminal coils and also a comparison of the results measured and calculated by equivalent circuit. The appropriate rate of reduced turns of terminal coils is about 20%. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 49–56, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10093     

同塔双回输电线路的雷电反击计算及仿真

由于同塔双回输电线路电感较大,将面临更加严苛的防雷保护问题,所以为了降低输电线路的跳闸率,有必要对输电线路雷电反击的影响因素进行研究。采用ATP-EMTP建立了反击仿真模型,研究了不同雷电流幅值下的绝缘子两端的电压变化情况。利用规程法计算出不同冲击接地电阻、不同杆塔高度及不同波阻抗下的线路的耐雷水平和反击跳闸率。计算结果表明:降低接地电阻或杆塔高度可以有效地降低同塔双回输电线路反击跳闸率;当波阻抗独立地变化10%时,输电线路的反击跳闸率将相应地变化约20%。     

适用于混合仿真的戴维南等值阻抗改进求取算法

由于基于机电暂态数据获得的机电侧系统戴维南等值阻抗参数难以体现接口发生故障后机电侧系统的电磁暂态特性,文中提出了一种基于电磁暂态短路仿真的机电-电磁暂态混合仿真机电侧戴维南等值阻抗改进求取算法。该算法是基于一种不受各次谐波影响的系统时间常数求取方法,通过全电磁暂态模型的接口位置设置2次不同接地电阻的三相短路故障,联立时间常数方程计算得到机电侧系统的等值阻抗信息。与传统的基于机电暂态模型通过单位电流注入法计算出的等值阻抗相比,文中方法计算出的等值阻抗能够更准确地体现接口发生接地故障后机电侧系统的电磁暂态特性,从而提升了机电-电磁暂态混合仿真故障期间和故障后的仿真精度。     

Experimental and analytical studies on lightning surge characteristics of a buried bare wire

Lightning surge analysis is very important from the viewpoint of insulation design of transmission lines and substations. Lightning surge analysis has many parameters, which include lightning surge characteristics of transmission towers, back flashover phenomena at an arcing horn, characteristics of footing resistance, effects of corona wave deformation, characteristics of electromagnetic fields caused by lightning, and other parameters. This paper describes experimental and analytical studies on lightning surge characteristics of a buried bare wire. The measurement of the lightning surge characteristics of the buried bare wire is carried out under various experimental conditions. The experimental parameters controlled in these experiments include earth resistance, length of the buried bare wire, and waveform of the injected current. The measured results are compared with analytical results based on the theoretical study by Sunde. A comparison of the measured results with the analytical results shows good agreement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(3): 35– 41, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20532     

500kV HGIS变电站雷电侵入波的计算分析

针对500 kV HGIS新型设备不断涌现,以往建立的变电站雷电侵入波计算模型需要改进的问题,采用HGIS新型设备的某500kV变电站,分析设备生产厂家提供的HGIS结构参数和试验参数,建立其雷电过电压计算模型,并结合以往采用常规设备变电站的设计经验,优化变电站雷电过电压计算方法,采用国际通用的EMTP电磁暂态仿真计算程序,对500kV HGIS变电站的雷电侵入波作了较为深入的计算分析和研究,提出了该工程针对雷电过电压500kV母线侧可不加装避雷器,出线侧需加装避雷器的配置方案,该研究可供变电站雷电过电压建模仿真计算参考。     

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     

深圳供电局110 kV联城变电站过电压的分析

通过电磁暂态计算,对深圳供电局110kV联城变电站可能遭受的雷电及操作过程进行研究,分析了杆塔反击时雷击点,运行方式,保护方式对联城变电站雷电侵入波的影响,最后对联城变电站的防雷措施提出具体改进意见。     

考虑曲率时汽轮发电机的运算电抗和等效电路

本文在极坐标下,求解汽轮发电机异步运行时向量磁位A的二维涡流方程,得出了交、直轴运算电抗及其等效电路;研完了考虑曲率和不计曲率时运算电抗间的联系.     

基于等效电路参数特征量的油纸绝缘老化状态评估

针对油纸绝缘等效电路参数与绝缘老化机理内在关系的研究较少,通过对变压器油纸绝缘等效电路参数与老化状态之间的关系进行分析,提出了利用等效电路中极化支路的平均弛豫时间常数作为评估变压器油纸绝缘老化状态的特征量,该参数受绝缘系统几何结构影响较小。通过大量数据分析获得利用平均弛豫时间常数与油纸绝缘老化之间的规律:油纸绝缘老化越严重,则平均弛豫时间常数越小。最后利用变压器实例验证了该特征量评估绝缘老化状态的有效性,为评估变压器绝缘状态提供新的思路与方法。     

计及部分电容的接地回路高频电路模型

建立相对精确的接地回路电路模型,研究接地回路的阻抗频率特性,对研究接地回路的传导干扰具有重要意义.首先建立了一个大尺寸的接地回路实物模型,运用PEEC方法求出各部分参数并建立了考虑部分电容作用的等效电路模型.实测和仿真的阻抗频率特性非常吻合,证明用PEEC方法分析研究大尺寸接地回路的高频阻抗特性是可行的,拓展了PEEC方法的应用领域.另外,在用HP4395A阻抗分析仪测量高频阻抗频率特性时,为屏蔽外界电磁干扰,应该对被测模型加屏蔽罩并可靠接地.