山火引发输电线路跳闸事故的统计与分析

通过对部分引发输电线路跳闸的火灾事故进行统计以及对典型火烧迹地的跳闸事故进行考察,分析山火发生的次数、跳闸率、地理位置、过火区域地形地貌等,探讨引发线路跳闸的潜在山火类型、形成过程、影响因素和特性参数以及跳闸输电线路的放电特性参数。结果表明:易引发跳闸的山火类型依次为中高速中高强度的地表火、树冠火、冲冠火和地表火转化的树冠火;火灾基本为上山火,易形成高火焰、高热量、高温度、高浓度(烟尘粒子和带电质点)的易导致线路跳闸的环境条件;发生跳闸时输电线路主要放电部位为子导线,放电方式依次为对树、相间和对地;在中高强度火灾条件下放电距离突破了输电线路正常运行所需安全间隙,产生流注而发生跳闸。     

湖南电网输电线路山火跳闸时空分布规律

基于2010年1月至2018年2月湖南电网输电线路山火跳闸和输电线路山火数据,分析输电线路山火及其导致输电线路跳闸的时空分布规律,发现输电线路山火跳闸具有明显的区段集中性。采用皮尔逊相关性计算,得到影响输电线路山火灾害的主要气象因子为相对湿度和降水量。湖南地区冬春季节干燥天气、夏季快速生长的植被以及祭祖、烧荒频繁的用火习俗共同导致输电线路山火灾害频发,且极端干旱天气条件下的山火更易造成输电线路跳闸。根据研究结果提出针对性防山火对策。     

山火诱发高压输电线路跳闸典型事故分析

通过调研湖南省某处山火诱发500kV高压输电线路跳闸的事故,以桂山乙线454#杆塔为代表,分析此次山火成因、等级、类型和强度,分析空气温度和相对湿度、风速和风向对山火形成和发展影响以及山火作用下线路跳闸行为、类型、成因和机理。结果发现:诱发桂山甲乙同塔双回线路跳闸的山火为火线强度高于10 MW/m的高强度地表火,后在风速和风向作用下转为高强度冲冠火和被动型树冠火;紧凑型交流线路易发生相间放电,桉树和茅草等植被型扩散性火焰产生的大量导电性离子和电子及针状烟尘颗粒促发和加剧了这一过程,直至形成电子崩和流注通道,诱发线路跳闸。     

江西输电线路山火事故分析与措施

输电线路山火事故在输电线路事故中占有不小的比例。就江西省而言,五年以来,因输电线路因山火原因造成线路跳闸就多达74次。随着春冬季耕种烧荒增多,春节、端午节、中秋节、清明、冬至等民俗节日燃放烟花爆竹、烧香焚纸祭祖风气日益盛行,山火引发线路跳闸的形势不容乐观。因此,分析输电线路山火事故的特点及原因,总结相关防山火工作经验和教训,梳理出有效的防山火对策与建议,显得意义重大。     

山火诱发500kV及以上输电线路跳闸事故分析

通过对2009-2014年南方电网辖区500 kV及以上电压等级输电线路山火跳闸事故统计,结合谷歌地球软件、洛伦兹曲线以及基尼系数分析研究事故时空不均衡分布特性,并从地形坡度及重合闸成功情况等因素分析山火发生规律,讨论了典型事故过程序列及地域和地貌等方面的诱因。结果表明:南方电网辖区可燃易燃人工林易于着火并传播火灾;山火导致跳闸事故时空分布不均衡;山火诱发跳闸重合闸成功率较低。     

山火条件下高压输电线路放电特性

利用单、双和三木垛火源和单股、双分裂和四分裂模拟高压导线研究了中尺度高压输电线路在火灾条件下的放电特性及其与火源火场参数的关系,提出了为防控火灾实际输电线路走廊内森林可燃物管理方法.结果发现,模拟导线在火焰中较纯空气中容易发生放电(火焰中空气平均击穿场强较纯空气中约下降64.9％);火持续时间、火焰高度和火灾荷载密度对平均击穿场强的影响程度依次减弱,火强度则是决定性影响参数(木垛火源双木垛火变为三木垛火时,空气平均击穿场强与火强度、火灾荷载密度、火持续时间及火焰高度增幅比分别为2.11、0.482、1.70和0.582);中高速中高强度的上山地表火、树冠火、冲冠火和地表火转化的树冠火易形成高火焰、高热量、高温度、高浓度(烟尘粒子和带电质点)的容易使线路跳闸的环境条件.     

山火导致输电线路间隙击穿特性的研究现状

近年来,随着多条特高压输电线路投入运营,山火引发输电线路跳闸,跳闸事故给电网的安全稳定运行带来了严重挑战,因此,研究山火条件下输电线路间隙击穿特性具有重要意义。山火发生时,产生的火焰高温、火焰电导率、固体颗粒等导致输电线路间隙绝缘性能剧烈下降,可能引发输电线路跳闸,且重合闸容易失败,容易导致输电线路停运的严重事故。本文对山火导致输电线路间隙击穿主要诱因进行了综述,研究了火焰温度、火焰电导率、固体颗粒等对输电线路间隙击穿特性影响的现状。分析结果表明:山火引发输电线路间隙击穿是多种因素综合作用的结果,当前的研究结果分散性较大,且考虑因素较为单一,对于指导山火引发输电线路跳闸防护具有一定局限性。建议综合考虑山火条件下的各种因素耦合作用,进一步从理论计算、仿真建模和山火模拟试验等方面对山火条件下输电线路间隙击穿特性进行研究。     

冬季用火安全管理

冬季来临，由于气候的变化，除经常性的生产生活用火外，大多数企业、事业单位和城乡居民开始取暖，用火、用电大量增多，加上冬季气候干燥，可燃物极易燃烧，稍有疏忽，就会酿成火灾，据统计，每年约有30%以上的火灾发生在冬季。因此，冬季防火工作应特别引起人们的高度重视，下面就向您谈谈——     

输电线路周边火灾卫星遥感监测研究与应用

为避免电网跳闸停电事故的发生,提高输电线路山火监测的周期性和全面性,本文利用卫星遥感红外探测地表温度技术对福建省输电线路山火发生概率较大的重点县区开展了山火监测的应用研究,实现全天时全天候、大范围面状火点监测.利用自主构建的FAL模型以可信度≥4和输电线路2km以内为阈值条件获得输变电周边火点,分析火点与输电线路之间的...     

黑板报

据统计,每年约有60%以上的火灾发生在冬春季节,为什么呢?主要原因有:(1)可燃物多:冬季处在收获季节之后,农村柴草等到处堆放.工厂、机关、学校因天气寒冷,燃料的储存和消耗量较多,加上气候干燥,可燃物极易燃烧.(2)火源多:冬春季节日短夜长,气温低,用火、用电大量增多,照明、烧烤、加温     

江西省森林火灾发生特点及防治对策研究

基于ArcGIS、Excel 等空间分析和数学统计手段,对江西省2011-2018 年的森林火灾发生情况、起火原因、时空分布等特点进行研究,以此分析山地丘陵地区森林火灾动态特征。结果表明,江西省在此年间共发生火灾202 次,上坟烧纸、烧荒烧炭和野外吸烟是引发森林火灾的主要原因,分别占总数的29%、17%、14%;森林可燃物中主要以中熟林、幼龄林、杉木及马尾松为主要树种;森林火灾多集中在上半年,尤其1-4 月,下半年较少;每天的12-18 时为火灾高发时段,22 时至次日6 时火灾发生次数较少;上饶市、吉安市发生火灾次数最多,热点区域主要集中在上饶市117̊48′E,28̊19′N 处和萍乡市113̊46′E,27̊42′N 处。本研究可为山地丘陵地区林火管理工作提供理论支持。     

Modelling of two-dimensional flame spread across a sloping fuel bed

A significant contributing factor to wildland fire development is the slope effect which causes the fire spread rate to increase considerably as compared to horizontal spread. This leads to difficulties in determining the development of the fires hence in coordinating forest fighting efforts. In the present study, a two-dimensional non-stationary model for a fire spreading across a sloping fuel bed made up of Pinus pinaster litter is described. Based on a series of hypotheses, we first defined a medium equivalent to the pine needle litter for which we provided a thermal balance. By coupling this balance to a diffusion flame model we obtained the fire spread model numerically solved by means of the SIMPLEC procedure. The fire spread rates given by the simulations were then compared to experimental results generated by small-scale laboratory fires for a range of slope values. Predicted flow field structure, and temperature field are also discussed.     

A methodology for comparing the relative effectiveness of suppressant enhancers designed for the direct attack of wildfires

Suppressant chemicals are often added to water for use in the direct attack of wildfires to extend the longevity and suppression effects of the water. There are a range of suppressants available, however there has been limited testing to determine which are the most effective. This paper presents an experimental methodology designed to enable the comparison of the relative effectiveness of wildfire suppressants applied in direct attack to fires in forest fuels. The method involves suppressants being applied onto the flaming fronts of standardised laboratory fires burning in uniform forest litter fuels within a wind tunnel through a pressurised system mounted above the burning fuel. The minimum volume of suppressant required to extinguish a standard fire is determined and used to quantify suppressant effectiveness. Examples of the method are presented for plain water and water with three types of wildland fire suppressant. Results show that repeated tests conducted with the same suppressants have low variability (coefficient of variation ~10.8%) and thus high reliability. In order to minimise effects of non-controlled variation in fire behaviour between tests, results can be normalised to produce relative values for comparison across datasets.     

Wildland fire spot ignition by sparks and firebrands

Wildland and Wildland Urban Interface (WUI) fires are an important problem in many areas of the world and may have major consequences in terms of safety, air quality, and damage to buildings, infrastructure, and the ecosystem. It is expected that with climate changes the wildland fire and WUI fire problem will only intensify. The spot fire ignition of a wildland fire by hot (solid, molten or burning) metal fragments/sparks and firebrands (flaming or glowing embers) is an important fire ignition pathway by which wildfires, WUI fires, and fires in industrial settings are started and may propagate. There are numerous cases reported of wildfires started by hot metal particles from clashing power-lines, or generated by machines, grinding and welding. Once the wildfire or structural fire has been ignited and grows, it can spread rapidly through ember spotting, where pieces of burning material (e.g. branches, bark, building materials, etc.) are lofted by the plume of the fire and then transported forward by the wind landing where they can start spot fires downwind. The spot fire problem can be separated in several individual processes: the generation of the particles (metal or firebrand) and their thermochemical state; their flight by plume lofting and wind drag and the particle thermo-chemical change during the flight; the onset of ignition (smoldering or flaming) of the fuel after the particle lands on the fuel; and finally, the sustained ignition and burning of the combustible material. Here an attempt has been made to summarize the state of the art of the wildfire spotting problem by describing the distinct individual processes involved in the problem and by discussing their know-how status. Emphasis is given to those areas that the author is more familiar with, due to his work on the subject. By characterizing these distinct individual processes, it is possible to attain the required information to develop predictive, physics-base wildfire spotting models. Such spotting models, together with topographical maps and wind models, could be added to existing flame spread models to improve the predictive capabilities of landscape-scale wildland fire spread models. These enhanced wildland fire spread models would provide land managers and government agencies with better tools to prescribe preventive measures and fuels treatments before a fire, and allocate suppression resources and issue evacuation orders during a fire.     

北极地区山火对我国高寒地区林火管理的启示

北极地区主要包括北冰洋和周围一圈无树木的冻土地带,植被以生长接近地面的低矮灌木、类禾本植物、草本植物、苔藓和地衣为主,气候终年寒冷,火源以干雷暴为主.受全球变暖和高温热浪影响,北极地区山火的数量和强度不断增加,严重威胁生态安全,并引发一系列次生灾害.本文在总结2019年和2020年北极地区山火案例的基础上,分析北极地区...     

滇中地区萌生栓皮栎地表可燃物燃烧火行为研究

为评估萌生栓皮栎林的潜在火行为以及发生火灾的危险性,森林防火紧要期内在云南森林自然中心的萌生栓皮栎林进行外业调查。通过设置样地,测量样地内栓皮栎林的高度、胸径等,采集地表可燃物进行室内燃烧试验,结合野外实际状态和实验室理化分析,测定含水率、载量、灰分含量,利用点燃性、剧烈性和消耗性等指标,研究了栓皮栎地表可燃物的三维燃烧性。研究结果表明：在防火期紧要期,栓皮栎地表可燃物的含水率为3.53%～5.04%,载量为0.44～0.69 kg/m²,灰分含量为12.3%～16.4%,引燃时间为(4.8±0.3)s,蔓延速率为(0.36±0.09)m/min,烧损率为(61.99±9.29)%。可见,栓皮栎地表可燃物的含水率极低,点燃温度低,载量低,灰分含量较高,三维燃烧性表现较差;叶片很易燃,一旦有火源就容易被引燃,引发森林火灾。研究结果有利于掌握萌生栓皮栎林地表潜在火行为相关特征,为更好预防森林火灾提供参考依据,为滇中地区的林火管理提供理论支撑。     

华山松林地表可燃物着火及蔓延特征研究

在云南森林自然中心石关和园宝山华山松连续分布区设置样地,沿对角线设置6块2 m×2 m块小样方取样,采用200 cm×120 cm×32 cm铁质燃烧床进行实验,将燃烧床坡度设置为10°,测定可燃物的引燃时间、续燃时间、无焰燃烧时间、热辐射特征以及烧损率等参数,表征其着火特征和蔓延特征。结果表明,两处地表可燃物引燃时间为1~3 s,易引燃;石关上坡火续燃时间相对较短,约150 s;园宝山下坡火无焰燃烧持续较长,最长达345 s。园宝山上坡火速率均大于石关上坡火速率;上坡火的损烧率最高为88.29%,下坡火最高为76.13%。     

Fuel Moisture Thresholds in the Flammability of <Emphasis Type="Italic">Calluna vulgaris</Emphasis>

Managed and wild fires play a significant role in the ecology of heathlands in the UK but we currently have little ability to forecast fire behaviour or the likelihood of accidental wildfires. Like many shrubland fuel types, heathlands display significant structural complexity and the role of different fuel components in governing flammability has not been clear. Using a series of small, field-based ignition tests, we demonstrate the critical importance of the moisture content of dead fine fuels in the lower canopy for determining when sustaining fires in the vegetation canopy can develop. At moisture contents above c. 70% both spot and line ignitions failed but where moisture contents were less than c. 60% fires developed rapidly. The initial rate of spread of successful ignitions was primarily controlled by the moisture content of the lower canopy and the moss/litter layer. Models that predict the moisture content of elevated dead fuels and the moss litter layer are urgently needed in order to protect heathlands from wildfire and to allow forecasts of the suitability of conditions for prescribed burning to be developed.     

长白山6 种主要森林类型地表凋落物燃烧性实验研究

以长白山黄松蒲林场6 种主要森林类型林地内凋落物为对象,研究长白山林区地表凋落物的燃烧性。在长白山黄松蒲林场的白桦林、针叶混交林、针阔混交林、落叶松林、阔叶混交林和杨树林6 种主要森林类型林地内设置样地,通过外业调查、混合采样的方式收集地表凋落物并进行燃烧实验,测定火蔓延传播的速度、燃烧温度和质量变化。通过改变实验风速、坡度和坡向,研究不同条件对火行为、火蔓延速度和烧损率的影响。实验结果表明：长白山地区地表凋落物的火强度从大到小排序为白桦林、针叶混交林、针阔混交林、落叶松林、阔叶混交林、杨树林,白桦林的火强度最大,为460.23 kW/m,杨树林的火强度最小,为367.09kW/m;风速越大,地表凋落物火蔓延速度越大;风速为6 m/s 时,燃烧过程平均温度最大,烧损率最高,当风速小于2 m/s 或大于8 m/s 时,可燃物无法完全燃尽;上坡火坡度增加时,地表凋落物的火蔓延速度增加,烧损率减小;下坡火坡度增加时,地表凋落物的火蔓延速度减小,烧损率增加。     

Climate change and forest fires

This paper addresses the impacts of climate change on forest fires and describes how this, in turn, will impact on the forests of the United States. In addition to reviewing existing studies on climate change and forest fires we have used two transient general circulation models (GCMs), namely the Hadley Centre and the Canadian GCMs, to estimate fire season severity in the middle of the next century. Ratios of 2 x CO2 seasonal severity rating (SSR) over present day SSR were calculated for the means and maximums for North America. The results suggest that the SSR will increase by 10-50% over most of North America; although, there are regions of little change or where the SSR may decrease by the middle of the next century. Increased SSRs should translate into increased forest fire activity. Thus, forest fires could be viewed as an agent of change for US forests as the fire regime will respond rapidly to climate warming. This change in the fire regime has the potential to overshadow the direct effects of climate change on species distribution and migration.