Initiation of lightning in thunderclouds with the use of artificial clouds of charged aerosol

Results of the experimental simulation of lightning initiation processes in thunderclouds by large hydrometeor arrays using artificial clouds of charged water aerosol of negative and positive polarity are presented in this paper. A significant influence of the hydrometeor arrays on the discharge initiation and propagation between the charged cloud and the ground is shown. It is found that cloud polarity has a significant influence on the probability of discharge initiation by the hydrometeor array. It is established that hydrometeors have the most pronounced influence on the discharge initiation in positively charged aerosol clouds. Character types of the discharge phenomena initiated by the hydrometeors in the clouds of negative and positive polarity are found: cloud discharges, channel discharges, and diffuse discharges. It is established that the characteristic frequency ranges in the wavelet spectrum of electromagnetic radiation of such discharge phenomena initiated by hydrometeors have greater values for a negative polarity of a cloud than for a positive one. It is found that the characteristics of the current impulse of the main stage of the discharge between the cloud and the ground forming with the participation of hydrometeors differ from the analogous characteristics for cases in which hydrometeors are absent in the gap between the charged cloud and the ground. Thus, using artificial clouds of charged aerosol opens new possibilities for investigation of the processes of lightning initiation in thunderclouds.     

肃雷暴云电荷分布和闪电特征的个体差异

分析观测的资料表明,虽然甘肃地区雷暴云的电结构普遍呈三级结构,云底部存在一分布相当广的正电荷层,但不同雷暴中的闪电类型及闪电行为特征往往有较大差异。有些雷暴没有负地闪,而有些雷暴过程中却有负地闪;有些雷暴中的负地闪全为C型,有些则既有C型,又有P型。不同雷暴中闪电情况的不同,与雷暴云的个体差异性有关。     

3D imaging of lightning channel and leader progression velocity

Three‐dimensional imaging of lightning channels by means of UHF interferometers is performed. To realize this, a field campaign was conducted with two observation sites in Darwin, Australia. The distance between the two sites is about 14 km, and the triangulation scheme is applied to estimate locations of UHF radiation sources. Since the UHF radiation is more likely during the leader progression than in the return stroke phase, imaging of lightning channels is obtained mainly for downward leaders. Velocities of downward leaders are estimated and statistics are presented for first and subsequent strokes. The result is consistent with those of former investigations obtained by optical observations. The statistics for the velocity of leader propagation inside thunderclouds are presented herein. Using optical measurement, velocity estimation of leader progressions inside thunderclouds is impossible, and the presented results are concluded to be the first results of their kind. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 22–28, 2001     

不同矿藏地区雷电参数分布特征及对比分析

为研究雷电参数与矿藏之间的关系,根据雷电定位系统2013年1月至2022年12月的监测资料,对四川凉山州5个不同矿藏地区（镍矿、铁矿、铜矿、钨矿和锡矿）的地闪频次、雷电流幅值、雷电日等雷电参数分布特征进行了统计分析。结果表明,不同矿藏地区的地闪频次、雷电流幅值、雷电日差异较为明显,在年变化、月变化和日变化中：镍矿地区的地闪频次相较于其余4个矿藏地区最为突出,其余矿藏地区的地闪次数也有明显的差异;不同矿藏地区的雷电流幅值有明显差异,其中钨矿的雷电流平均幅值最大,镍矿的雷电流平均幅值最小;不同矿藏地区的雷电日也有明显的差异,镍矿地区10年的平均雷电日最大,铜矿和钨矿地区次之,铁矿和锡矿地区最小。     

Initiation of Spark Discharges between Artificial Thunder Cells Using a Hydrometeor

This paper presents the results of an experimental investigation of the influence of model hydrometeor arrays on the initiation and propagation of the spark discharges between the artificial thunder cells of the negative and positive polarity. It is specified that introduction of the negative and positive polarity of the model hydrometeors of different types joined into the array using the various methods into the gap between the artificial thunder cells, leads to the significant growth of the probability of initiation of the spark discharges between the cells and total length of the forming discharge system. It is stated that the model hydrometeors of the cylindrical form joined into the group using the dielectric string or tape are the most efficient for these purposes. The physical picture of formation of the spark discharges by the groups of the hydrometeors between the artificial thunder cells of the different polarity is constructed considering the possibility of formation of the high-current streamer and volume leader discharges.     

盘锦地区1996～2020年的电力负荷预测

本文以不同的负荷预测方法对盘锦地区的近期,中期和长期电力负荷作了预测,并给出了结果,还对此地区负荷增长的可能性和必然性进行了分析。     

地闪放电过程的甚高频辐射特征分析

为了研究闪电的甚高频辐射特征，自行研制了闪电甚高频辐射脉冲探测和定位系统，并将其用于对地闪的280MHz辐射电场进行了观测。研究了4次地闪的甚高频辐射波形及其特征，得出地闪在该频段的辐射可分为3类，孤立脉冲、连续脉冲和多个孤立脉冲，进一步分析给出了这三类辐射脉冲信号在闪电的不同阶段发生的频数和所占的比例，统计分析结果表明在地闪的预击穿过程中孤立脉冲电场波形所占的比例最大，而在梯级先导过程中连续脉冲电场波形所占的比例最大，预击穿过程中的多个孤立脉冲数大于梯级先导中的多个孤立脉冲数，最后对这种现象的产生机制进行了探讨，认为此现象是由于梯级先导的电磁辐射比预击穿过程强而造成的。     

基于雷电记录与行波数据的雷击故障测距结果优化方法

针对输电线路故障概率最高的雷击故障存在实测数据故障点反射波难以标定等困难,提出基于行波测距数据和雷电定位系统记录等多平台来源信息的雷击故障测距结果优化方法。以实测数据中疑似故障点反射波对应的疑似故障点作为基准,根据最近邻地闪记录与疑似故障点之间的空间距离和时差排除雷电定位系统中非故障雷击地闪记录和实测行波数据中非有效行波的干扰,初步确定故障点位置。在此基础上,根据最近邻地闪记录在空间位置上的趋向性,以线路走廊走势作为基准,计算最近邻地闪记录与线路走廊各基杆塔之间的空间趋势接近度,以接近度作为修正系数对行波测距结果进行优化。最后,以故障实测数据进行验证表明该方法可行、有效。     

Relationship between the energy distribution of electrostatic field change and lightning activity

A lightning strength parameter α (denoted as LSP or LAIDO), which is used for characterizing the phenomena of lightning activity, has been proposed, where α is defined by the characteristic energy obtained from the energy distribution of a radiated field component E in the electrostatic field changes produced by lightning discharge. Here, it is observed that the energy distribution of E_γ components is Maxwellian type. To prove more clearly the forementioned assumption from another viewpoint, changes of the amplitudes of the electrostatic field component E_S were measured and their distribution functions constructed. In the cloud-to-ground lightning discharges, the E_S components have a positive sign in the changes. However, those changes in the intercloud discharges are observed with either a negative or positive change depending on the distance between the striking point and the observation site. Therefore it is necessary to sum the numbers of occurrences of both positive and negative components for constructing an energy distribution of the E_S component. A fieldmill and a pair of doughnut-shaped electrostatic antennas are used in measuring the changes of the E_S component. As a result it is found that the changes of the amplitudes of the E_S components have a Maxwelliantype energy distribution. A characteristic energy β is defined which is obtained from the component of the electrostatic fields as a measure of LSP. Based on comparison of α and β it is clarified that β has the same characteristic nature with α. The lightning activity could be estimated from β.     

电网雷害分布图研究

为能够直观反映电网雷害分布,从地闪时空分布基础数据出发,通过确定电网雷害危险电流区间研究确定雷害危险事件频次分布及其分级的评估体系,提出了电网雷害分布确定方法。以华北雷电监测网2003~2006年共计375.2万次地闪记录数据为例,结合华北500、220 kV电网典型耐雷水平及其雷害故障历史记录数据,用电网雷害分布统计方法,研制了华北电网雷害图;分析了华北电网雷害事件与雷害分布图相关性。结果表明,电网雷害分布图与电网雷害故障历史记录间有良好的线性相关性。     

25～100 MHz频段闪电脉冲辐射能量频谱特征

对闪电不同放电过程中辐射能量频谱特征的观测分析结果表明，经25MHz高通滤波器对闪电辐射能量的低频成分抑制后，所得到闪电不同放电过程期间的宽带辐射信号，其能量谱分布有较大的差异，在25－100Mhz频段内，地闪较低频段的辐射强于云闪、云闪、地闪预击穿过程 和K变化过程峰值辐射能量处于相对较高的频段，表明这些过程可能以较小尺度的放电为主要特征：梯级先导和直窜先导过程初始阶段辐射能量主要集中在较高频段，而接近地面时则集中在较低频段，表明先导在向地面发展过程中放电尺度逐渐增大。     

±800 kV宾金线浙江段正负地闪多重回击特征分析

为得到±800 kV宾金线浙江段沿线走廊正、负地闪多重回击特征,对2017年6月至9月监测到的3 032例完整地闪样本的特征参数进行了统计分析,主要包括回击次数、地闪持续时间、回击间隔时间、回击强度四个方面。多重回击参数呈明显的随回击序号系统性变化特征,且正、负地闪特性差异较为明显。统计结果表明：正、负地闪样本数量分别占27.57%和72.43%;负地闪样本中单回击占52.60%,最大回击次数达到13次,平均回击次数为2.47次;正地闪样本中单回击占比更大,达到77.04%,而回击次数相对较少,其最大回击次数为5次,平均回击次数仅为1.26次。正、负地闪多重回击持续时间随回击次数增加呈递增趋势,且负地闪持续时间的增长速度更快,其整体的算术平均分别为250.20 ms和343.02 ms。负地闪回击间隔时间随回击次序变化不明显,而正地闪回击间隔时间随回击次序呈递减趋势。总体上正、负地闪后续回击强度比值均随后续回击次序增加呈递减趋势;负地闪首次回击电流强度随回击次数增加呈递增趋势,而正地闪变化趋势不明显。     

Forecasting Fossil Fuel Demand

The possibility of interfuel substitution in the generation of electrical energy exists. Given this fact, a demand model for various fossil fuels by electric utilities in the United States is developed. The results obtained using regional data suggest that the responsiveness of the demand for coal, residual fuel oil, distillate fuel oil, and natural gas by electric utilities to relative price changes is significant. In a forecasting setting, the demand model performs remarkably well when actual and forecast values for 1979 are compared.     

Neural-network-based demand forecasting in a deregulatedenvironment

The traditional approach to load forecasting is based on processing time series of load and weather factors recorded in the past. In the dynamic environment of the deregulated power industry, historical load data may not always be available. This paper explores the possibility of an alternative approach toward load forecasting based on indirect demand estimation from available customer data. This approach requires utilization of demand models for different customer categories. This paper presents a neural network-based method of demand modeling. Neural networks are designed and trained based on the aggregate demands of the groups of surveyed customers of different categories. The performance of such models depends on the neural network design and representativeness of the training data. The forecast accuracy is also affected by the forecasted group size, customer characteristics, customer classification system, and the extent of demand survey. This paper discusses the issues of neural network design and illustrates the proposed method by its application to forecasting demand of residential customers     

Toward Estimating Autonomous Neural Network-Based Electric Load Forecasters

Anticipation of load's future behavior is very important for decision making in power system operation and planning. During the last 40 years, many different load models have been proposed for short-term forecasting. After 1991, the literature on this subject has been dominated by neural network (NN) based proposals. This is mainly due to the NNs' capacity for capturing the nonlinear relationship between load and exogenous variables. However, one major risk in using neural models is the possibility of excessive training data approximation, i.e., overfitting, which usually increases the out-of-sample forecasting errors. The extent of nonlinearity provided by NN-based load forecasters, which depends on the input space representation, has been adjusted using heuristic procedures. Training early stopping based on cross validation, network pruning methods, and architecture selection based on trial and error are popular. The empirical nature of these procedures makes their application cumbersome and time consuming. This paper develops two nonparametric procedures for solving, in a coupled way, the problems of NN structure and input selection for short-term load forecasting.     

短期风电功率预测概念和模型与方法

随着并网风电容量的持续增加,风电强随机性给电力系统安全稳定运行带来了挑战,风电功率预测受到广泛的关注。文中较为全面地综述了国内外对风电功率预测的研究现状,着重从风电预测基本理论、风电预测方法和风电预测热点研究问题3个方面展开,主要介绍了确定性风电预测、概率性风电预测、风电爬坡事件预测、大数据和深度学习方法等方面的研究进展。     

湖南省雷电活动及其规律的分析

地闪活动规律是防雷工程中重要的基础资料,可以为输电线路路经的选择及采取有效的防雷措施提供参考依据。为掌握湖南省雷电活动及其规律,根据湖南省雷电定位系统2002—2010年共9a的雷电数据,统计分析了湖南的雷电流强度概率分布;结合气象观测站1997—2003年雷暴日观测记录,利用地理信息系统（GIS）,采用网格法统计不同...     

Surface discharges on polymeric insulator shed surfaces

This paper describes results of an experimental investigation into surface discharges occurring on the surface of polymeric insulators. Discharges on partially hydrophobic surfaces were found to occur across well defined dry bands, while discharges on hydrophobic surfaces appeared as small points of light occurring between discrete water drops. These discharges were observed to produce a localized loss of hydrophobicity. It is shown that these discharges are stable atmospheric-pressure glow discharges. The discharges are characterized by a high cathode voltage fall, dependent on the electrical conductivity of the water drop, and a voltage gradient in the positive column, dependent on the discharge current. A technique is presented for measuring the rate at which surface hydrophobicity of polymeric materials is lost due to the action of this type of discharge. It was found that the loss of hydrophobicity occurred predominantly in the region near the cathode     

Tree growth monitoring by means of digital partial discharge measurements

In this work results relevant to electrical treeing tests performed on several ethylvinylacetate EVA (with different vinylacetate percentage) and on cross linked polyethylene (XLPE) (of two different lots) polymer materials are presented. During the tree growth the partial discharges (PDs) were monitored by means of a digital PD acquisition system and the tree morphologies were optically evidenced by means of video recorder equipment. The PD acquired data, the outcome of the video monitoring and the time-to-breakdown were off-line processed and analysed. In this way, two main results were obtained: the first one, applicable to this kind of laboratory treeing tests, is related to the possibility of predicting the lifetime of the specimens, considering a specific PD measurement derived quantity; the second one demonstrates the possibility to detect the tree morphology considering the phase-number distribution obtained by the digital PD measurement. The presented test procedures are deemed to have a potential for diagnostic applications.     

基于可信度加权组合的电价波动模式日前预报方法

准确的日前电价预测对电力市场参与者的优化决策具有重要意义。目前,大多数日前电价预测方法并不区分每天电价的波动模式而采用统一模型进行预测,当被预测日的波动模式与历史数据出现较大差异时无法保证预测的准确性。根据不同的日波动模式采用相似历史数据进行分类建模是解决此问题的有效途径,这就需要建立针对历史数据不同波动模式的分类识别模型和针对未来波动模式的日前预报模型。为此,文章提出一种针对分类预测的电价日波动模式日前加权组合预报方法。第一,采用K-means算法对日电价序列进行聚类分析,在分析聚类结果特性的基础上提取反映每日波动模式差异的特征向量,利用支持向量机分类（support vector machine for classification, SVC）方法建立电价数据日波动模式的识别模型;第二,利用多种常规方法建立日前电价预测模型对日前电价进行预测,并将预测结果输入日波动模式识别模型得到对应的模式识别结果;第三,根据多个方法波动模式预测结果对历史数据表现出来的不同精度,设计了基于可信度的组合机制,实现考虑预测准确性的加权组合预测,从而得到最终的日波动模式预测结果。利用美国PJM电力市场电价数据进行的仿真分析表明,提出的日前电价波动模式预测方法能得到较为准确的模式预测结果;利用电价波动模式日前预报进行分类预测的精度相对统一预测有显著提高。