Lightning and Power Surge Damage to Appliances

Lightning rarely damages appliances by direct stroke to the appliance. Damage is usually caused by direct strokes to the power lines or by induced surges. Induced surges are caused by the release of bound charges on the line when overhead clouds lose charge because of a strike to objects other than the line. The direct stroke produces a large voltage, while induced surges usually have a lower magnitude voltage. Lightning usually damages appliance electrical insulation which leads to a continuation of the damage by the 60-Hz power that has the appearance of a non- lightning-related failure. Lightning or power surge damage can probably be ruled out if the equipment has failed because of certain problems such as an open conductor or a bad bearing. Electric lamps can provide a clue as to whether a high-voltage surge occurred in the electrical system because the filaments often open when subjected to such surges. Equipment can be protected by a design to withstand the highest normal voltage spikes expected. Proper grounding and bonding also is important. For critical components or equipment, surge arresters may be required.     

Light rail transit DC traction power system surge overvoltageprotection

At present, there are no industry standards or recommended guidelines for the application of DC surge arresters. It appears that such devices are applied based upon a rule of thumb without the benefit of analyzing characteristics, wave shape, and energy content of the expected overvoltage surges against the capabilities of the surge arrester. AC surge arresters are rerated for DC application. A difficulty arises due to a lack of clear published application literature on DC surge arresters, as well as lack of measured data on DC power system transient surges. This leads to the application of surge protective devices, which may be inappropriate. This paper describes the application of DC surge arresters to a typical light rail transit traction power system, and it makes a recommendation for the need of a standard on DC surge arresters test requirements and application guidelines     

Design and application considerations for motors in steep-frontedsurge environments

A large body of research has been conducted in the past 15 years into steep-fronted surges in electrical systems and their propagation in AC machine windings. This paper reviews the nature of the surge, the factors that determine its amplitude and rise time, and how it affects the motor winding. It then explains how its harmful effects can be controlled by system and winding design and by effective quality control. Related national and international standards are discussed and their shortcomings pointed out. Uncertainties in the prediction of amplitude and rise time of surges are explained, and guidance for cost effective specification of motors for application in a surge environment is given     

Surge protection for interface circuits of communication system

Microelectronic circuits are often damaged by surges. Surge protection for microelectronic circuits has some special requirements that are different than those for electrical equipment. The approach that the surge invades microelectronic circuits is studied in this paper. The surge withstand capability of some typical serial communication integrated chips, the behaviors of voltage-limiting components, and the influence of the connecting capacitance of a voltage-clamping device on digital signals are studied. Then, a design method of surge suppressor for communication systems is proposed.     

防雷元件的特性参数与其电容对通信信号的影响

微电子电路常因过电压损坏 ,其过电压保护与电气设备相比有不同的要求 ,因此文中介绍了过电压对微电子电路的侵入方式 ,测试了常用防雷元件的动作时延及其伏 -安特性 ,给出了防雷元件的电容对数字通信信号影响的计算公式。实测表明动作时延太长不能保护微电子电路 ,防雷元件的电容大于一定值后会使通信信号发生畸变 ,致使误码     

Matching Surge Protective Devices to Their Environment

A method is described for the rational selection of metal oxide varistors as surge protective devices in low-voltage applications, combining data on the surge environment and device characteristics. Fuses that may be connected in series with the varistors will be exposed to current surges resulting from the varistor operation. Experimental results on the effect of repetitive current surges on such fuses are described, and some guidance is provided on the necessary derating of fuses for series applications with varistors.     

Inverter-fed drives: which motor stators are at risk?

This article describes measurements of the surge voltage characteristics from a number of motors driven by inverter-fed drives (IFDs). The measurements were done with both laboratory and purpose-built instrumentation. Further, we discuss why certain surges deteriorate the insulation, and we give guidelines for determining which motors may be at risk of failure from IFD voltage surges. The effect of these surges on stator windings is also included, as well as means to determine if a motor installed in a severe surge environment will fail     

Partial discharge behavior in switching-surge-aged oil-papercapacitor bushing insulation

Partial discharge (PD) diagnostics are utilised to examine the aging process of mineral oil-impregnated-high density kraft paper capacitor bushing models, subjected to repetitive voltage switching surges. It is demonstrated that the PD measurements of cumulative apparent charge transfer and discharge inception stress constitute an effective means for assessing aging and its reversibility due to gas evolution and re-absorption or solubility of a mineral oil-impregnated-paper insulation system in the presence and absence of switching surges. While the experimental results indicate that electrically overstressed solid-liquid insulation can recover in part its initial electrical properties following an electrical stress-free period, long term stability is only effectively achieved by a reduction in the switching surge overstress through an increase in the overall insulation thickness. The electrical stress levels, employed in the experiments, are found to be not sufficiently elevated to lead to any detectable partial discharge formation within the oil phase itself; the observed discharge behavior is rather characteristic of the type that is normally associated with macroscopic cavities occluded within the oil-paper insulation systems     

Surge transference through transformers

The article demonstrates the need for secondary surge protection on main utility tie transformers and low-voltage substation transformers. Investments in these surge protection devices are minimal and an insurance against insulation failures. A more elaborate transformer model could be used in EMTP simulations, however, the results based on the simplified transformer inductive/capacitance model are valid for practical purposes. The modeling of surge phenomena on EMTP is complex, and a modeling of all the possible surges of atmospheric origin or generated within a distribution system will be time consuming. The cost of providing secondary surge protection on unit transformers is rather small, though a coordination of the surge arrester characteristics is required. Considerations should be applied to the overvoltage withstand capability of solid-state protective devices, ASDs, and monitoring and control equipment, which is much lower than the insulation levels associated with the power equipment.     

Transmission effects of surge protectors on category-5 cable systems

Surge protectors may be used on paired-conductor telecom circuits to provide protection against unwanted electrical energy surges. These protectors may have capacitance, inductance, or series resistance that can affect transmission. This paper provides numerical analyses of voltage-limiting and current-limiting protectors insofar as they impact insertion loss, return loss, and timing on a category-5 circuit. It is shown that surge protectors can significantly degrade transmission unless they are selected to be compatible with high-frequency applications by minimizing capacitance of voltage limiters, and series impedance of current limiters.     

一种输电线路故障测距新方法

针对传统距离保护方法存在许多不足,提出了一种输电线路故障测距新方法。该方法以同母线上任一“有限长”非故障线路作为参考线路,通过比较由故障线路暂态电流行波与该参考线路暂态电流行波形成的反向行波浪涌与其对应的正向行波浪涌的极性识别来自故障方向的行波浪涌,消除了来自参考线路的暂态行波浪涌的影响。通过电磁暂态分析软件仿真计算,表明该方法不仅能够对各种故障情况进行正确的识别,而且具有较高的精确度。     

Canadian national power quality survey: frequency and duration ofvoltage sags and surges at industrial sites

The occurrence of voltage sags and surges originating on the primary and secondary sides of industrial facilities can disrupt continuous and noncontinuous industrial computer processes, a costly issue for society. This paper attempts to answer several questions concerning the frequency and duration of voltage sags and surges posed by industrial customers. The answers to these questions are based on the national survey results of the frequency and duration of voltage sags and surges at industrial sites monitored at their utilization voltage levels (e.g. 120, 347 V) and on the utility primary side of their facilities. The survey results provide a knowledge base for monitoring, designing, and utilizing voltage sag and surge mitigating technologies     

一种利用暂态电流行波的输电线路故障测距方法

提出了一种利用暂态电流行波的输电线路故障测距新方法。以同母线上任一“有限长”非故障线路作为参考线路,通过比较由故障线路暂态电流与该参考线路暂态电流形成的反向行波浪涌和对应的正向行波浪涌的极性,识别来自故障方向的行波浪涌,消除了来自参考线路的暂态行波浪涌的影响。EMTP仿真表明这种方法是可行的。     

一种反应输电线路故障行波的测距方法

分析了故障暂态电流行波的基本理论,提出了一种故障测距原理,以同母线上任一"有限长"非故障线路作为参考线路,通过比较由故障线路暂态电流行波与该参考线路暂态电流行波形成的反向行波浪涌与其对应的正向行波浪涌的极性,识别来自故障方向的行波浪涌,消除了来自参考线路的暂态行波浪涌的影响。通过以本原理构成的故障测距系统进行实际检验,测距精度明显高于目前故障录波器的测距精度。理论分析和实测波形分析均表明该原理是可行的,并可以同时适用于永久性故障和瞬时性故障,而且不受电压过零故障的影响,在标准模式下还不受线路对端母线反射波的影响。     

浪涌抑制与电磁兼容

浪涌是低压电源线中最频繁发生的过电压和电流波动现象.研究电源线中的浪涌时不仅要分析它的电压幅值高低,还要分析它的电流和能量.电源线中浪涌抑制需要从过电压保护和电磁兼容两方面考虑.作者通过计算标准测试浪涌的波形和频谱,指出浪涌危害的主要原因和保护低压电源线与其上电子设备电磁兼容性的措施.最后计算了在交流电源中用氧化锌压敏电阻对浪涌进行限幅和泻流的一个实例.     

Protecting load devices from the effects of low-side surges

Wherever lightning and poor utility power system grounds exist, distribution secondary systems are subjected to high-voltage surges due to lightning current seeking ground through low-voltage circuits. Utilities are becoming aware of this low-side surge phenomena and are taking measures to protect their distribution transformers' secondary windings. These measures can increase the voltage stress at the customer service entrance. If any ground paths exist on the customer side of the service entrance, surges can penetrate further into the customer's system and damage loads. Damage caused by low-side surges can be avoided if properly coordinated arresters are installed at the transformer secondary, at the service entrance, and at load devices. This work describes the secondary surge phenomena and the importance of protecting the service entrance and critical load devices effectively, especially when the transformer secondary is protected. A properly coordinated and effective protection scheme is described and recommended     

基于时间域建模的晶闸管调压装置缓冲电路设计

三相晶闸管交流调压器由于传输线特性、器件半控性和负载电路的影响,在导通和关断瞬间极易造成过电压、过电流和电压电流瞬变现象。RC缓冲电路能有效抑制上述冲击,然而RC参数会影响驱动装置的损耗,如何获得最佳的参数匹配是需要解决的问题。本文按照时间域建模方法分析了一个导通周期内的晶闸管外特性,针对带有缓冲电路的模型,构建了晶闸管能耗指标和对系统冲击的数学描述。提出了将冲击作为约束条件,通过优化能耗指标,配置缓冲电路参数来实现节能抑制冲击的思想。借助Matlab工具得到了最佳参数配置。仿真曲线和实验波形表明优化的缓冲电路参数可以有效抑制系统的冲击并减少能耗,证明了这一设计的有效性。     

Impact of surge arrester number and placement on reliability and lightning overvoltage level in high voltage substations

Surge arresters are the most critical equipment for protecting high voltage substations. They play an important role in substations for limiting switching and lightning surges and diverting these surges to ground. On the other hand, surge arrester number and placement for high voltage substations can be determined based on some evaluations in the designing process of substations. Surge arresters can be placed on the both ends of substations, transformers, circuit breakers, reactors, capacitors and also high long bus-bars and etc. Therefore, failure of arresters during overvoltage can put substations in risk condition. Moreover, surge arresters may be inclined to be short circuit during normal operation condition due to ageing process and/or improper quality. This paper attempts to assess reliability of three common substation configurations namely: (1) one breaker and a half; (2) double-bus double-breaker; and (3) ring bus-bar in different placement of surge arresters. At first, maximum voltages on equipment are calculated in different lightning stroke locations through simulation in EMTP-RV. Studies without surge arrester and the presence of surge arrester in different locations are analyzed and compared. Then surge arrester’s placement impacts on the substations reliability indices are calculated in normal operating condition and overvoltage condition by minimal cut set method and simulation results. Analytical studies reveal that surge arrester can increase substations reliability. But for low annual number of lightning stroke, substation reliability may decrease. Also increasing surge arrester number more than substation need reduces reliability.     

一种新颖的航空直流电源抗浪涌电路

针对28 V航空直流电源系统中的过压浪涌和欠压浪涌,设计了一种双管Buck-Boost电路。该电路由Buck变换器和Boost变换器级联简化而成,对此电路设计了控制方法,使电路工作在降压、升压和LC滤波模式,能有效抑制过压浪涌和对欠压进行提升,而且对额定输入时的效率影响较小。从对电路性能影响方面,阐述了输出电压设定值的选取。传统的航空直流电源抗浪涌电路,结构较复杂、效率低,对额定输入时的效率影响也较大,故设计了一台300 W的原理样机,通过实验验证了该电路和所设计的控制方法能有效地抵抗航空直流电源中的浪涌,并使电路取得了较高的效率。     

Simulation and experimental analyses of electromagnetic transients behaviors of lightning surge on vertical conductors

Simulation of very fast surge phenomena in a three-dimensional (3-D) structure requires a method based on Maxwell's equations, such as the finite-difference time-domain (FDTD) method or the method of moments, because circuit-equation-based methods cannot handle the phenomena. This paper uses a method of thin-wire representation of the vertical conductor system for the FDTD method which is suitable for the 3-D surge simulation. The thin-wire representation is indispensable to simulate electromagnetic surges on wires or steel frames in which the radius is smaller than a discretized space step used in the FDTD simulation. In this paper, a general surge analysis program named the virtual surge test lab based on the Maxwell's equations formulated by the FDTD method, is used to simulate the surge phenomena of a vertical conductor, including the effects of horizontal wave incidence and vertical wave incidence. Experimental results on the reduced scale model have been presented in order to compare among the simulation results by the FDTD method and the results using numerical electromagnetic code based on the MoM.