Power outages,economic cost,and firm performance: Evidence from Ethiopia

The lack of secure and reliable electrical power is a constraint to doing business in developing countries. Industrial firms in developing countries adopt different strategies to cope with deficiencies in electricity supply. This paper employs the World Bank Enterprise Survey data to examine how firms in Ethiopia respond to power outages. The results show that firms in Ethiopia self-generate electricity in response to power outages. Power outages were found to affect firms' productivity negatively, increasing firms' costs by 15% from 2011 to 2015. This effect varied negatively with output level, suggesting that outage is particularly costly for small firms.     

大规模风电高压脱网分析及协调预防控制策略

由于受扰系统在故障切除后恢复过程中出现高电压引起风电机组大规模脱网的事故近年来频发,因此基于近年来已发生的大规模风电机群脱网事故,从风电机组故障穿越期间动态无功控制策略和风电场附加无功补偿装置控制特性两个方面分析了受扰后电网发生高电压现象的主要原因,并通过现场测试验证了机组动态无功控制策略对机端电压的影响。在此基础上,提出了避免风电机组高电压脱网的协调预防控制策略,即风电机组在满足高电压穿越要求的前提下根据电压变化参与系统无功调节,风电场附加无功补偿装置根据并网点电压以及场内机组脱网情况实现快速调节和退出。最后,通过仿真验证了协调预防控制策略的有效性。     

南方电网综合防御框架的构思

针对南方电网复杂的交直流混合输电的特点,构思时空协调的停电防御框架。在广域信息平台、在线量化稳定分析和自适应控制决策等环节上,提升防御灾变的功能,即从静态到动态范畴,从离线到在线,从定性到定量,从固定设置到自适应优化;其中特别强调相继故障的风险预警和多方面的协调。其创新点和工程应用还包括：在没有数学模型的支持下,评估实测时间响应曲线的轨迹稳定裕度;非自治非线}生系统的特征根分析技术;高维受扰轨迹之间的相似度指标,及以其为基础的模型识别技术;将气象和雷电等非电力信息整合到停电防御框架中,对相继故障的风险进行仿真和预警;基于风险管理概念的协调控制。     

Minimum Duration Outage for CDMA Cellular Systems: A Level Crossing Analysis

Traditionally, outage for CDMA cellular systems has been defined as the signal level (or, more precisely, the signal-to-interference ratio (SIR)) falling below a required threshold. In real cellular environments, it is not the instantaneous drop of the signal strength below the threshold that determines outage. It is, in fact, the duration of time below a threshold that determines outage for cellular systems. Moreover, the static analysis of outage precludes the time correlation in the signals which is important in real systems owing to mobility, fading and power control. In this paper, we analyze minimum duration outages for such systems, where outage is defined as an excursion of the SIR below a level for a certain minimum duration. We formulate the outage condition as a level crossing problem and extend asymptotic results from the theory of level crossings to derive analytical results for the probability of outage. This method enables us to include the time correlation of signals in the analysis as well. The validity of the asymptotic results is verified using some exact results as well as simulations. These minimum duration outages have implications in redefining user capacity and handoff performance.     

基于系统与元件动态交互量化分析的电力系统连锁故障事故链识别方法

针对现有的连锁故障事故链搜索方法一般只考虑线路的过负荷保护或确定性模拟保护控制的动作等不足,提出了基于系统与元件动态交互量化分析的电力系统连锁故障事故链识别方法。该方法基于事故链模型,提出关键元件保护控制动作评估指标,用于量化关键元件保护控制的动作情况。进一步根据该指标计算临界情况下关键元件保护控制的动作概率,确定连锁故障事故链的后续事件。最后,基于风险指标筛选高风险连锁故障事故链。对2017夏高峰负荷情况下的某实际电网进行仿真,结果验证了所提方法的可靠性和有效性。     

A study of Electrical Security Risk Assessment System based on Electricity Regulation

With the expansion of China's power system, there are more and more factors contributing to Large-area Power Outages. The snow disaster that hit Southern China in 2008 caused serious damages to the power systems, which made Chinese government realize that they cannot solely depend on power enterprises to effectively control the risk involved in power system. The Chinese government needs to collaborate with power enterprises in strengthening Electricity Regulation and taking countermeasures to reduce the risk of Large-area Power Outages. This paper first proposes an objective, practical and adaptive Electrical Security Risk Assessment System based on Electricity Regulation. The system consists of an assessment process with 278 indices, which are used to calculate the risk of Large-area Power Outages by the use of Analytic Hierarchy Process and the Delphi Method. Then, an example of Guangdong power system serves to illustrate the detailed implementation procedures of the proposed assessment system and the results show that Guangdong power system faces a moderate risk of Large-area Power Outages. Finally, some countermeasures are proposed to overcome the defects in the existing power system.     

Choice experiment study on the willingness to pay to improve electricity services

Modern forms of energy are an important vehicle towards poverty alleviation in rural areas of developing countries. Most developing countries’ households rely heavily on wood fuel which impacts on their health and socio-economic status. To ease such a dependency, other modern forms of energy, namely electricity, need to be provided. However, the quality of the electricity service, namely reliability, is an important factor in reducing this dependency. This paper discusses a choice experiment valuation study conducted among electrified rural households located in Kisumu, Kenya, in which the willingness to pay (WTP) to avoid power outages or blackouts was estimated. A mixed logit estimation was applied to identify the various socio-economic and demographic characteristics which determine preferences in reducing power outages among a household’s users. In conclusion, several of the socio-economic and demographic characteristics outlined in this paper were identified and can assist service differentiation to accommodate the diverse households’ preferences towards the improvement of the electricity service.     

新的防止大停电事故的后备保护减载控制策略

近几年来国际上发生的多起大停电事故表明:在线路过负荷情况下，后备保护先于安全自动装置动作是导致事故扩大的重要原因。提出一种新的后备保护控制策略，可以实现后备保护与安全自动装置的协调配合，防止大停电事故的发生。提出线路相关集的概念，介绍了基于决策树理论的线路相关集的搜索方法，对其关键技术点进行了重点分析，导出线路相关因子的求解办法。在此基础上，提出了一种新的后备保护减载控制策略。仿真结果表明所提出的控制策略的有效性。     

Evaluating the cost to industry of electricity outages

The unreliability of electricity supplies is a major cause of the high cost of manufacturing in developing countries. In this paper, we propose a more accurate approach, the contribution method, to measure the cost imposed by power outages. We employ a rich, if not unique, set of data from the detailed operating accounts of three large manufacturing enterprises in Nepal. Estimating the true opportunity costs to the enterprises from lost production caused by power outages sheds light on the issue of cost measurement that is critical for the determination of the feasibility of mitigating measures. Furthermore, having such micro-based information on the value of lost load per kWh by firm or sector is critical for reducing the economic costs of planned outages by the electric utility.     

电力安全是能源安全的核心

能源安全概念在20世纪70年代主要指石油安全,随着电力工业的迅猛发展和电气化程度的不断提高,能源安全的概念不断拓宽,它不仅包含所有的能源形式,也包括环境的兼容性和可持续性,还包括有效应对气候变化。我国电煤消费占原煤产量的比重已达到50%左右;2009年电力消耗的能源在一次能源总消费量中的比重已达到40.96%,已接近世界发达国家的水平;2009年电力在终端能源消费量中的比重达到22.3%,已超过石油(21.9%),位于仅次于煤炭的第二位;我国电力普及程度已达到发达国家水平。电力在我国能源中已居重要地位,电力安全成为能源安全的核心。要实现电力安全,在研究能源和电力发展战略的同时,应研究电力安全战略,在研究制订电力长期规划和五年规划的同时,要研究落实电力安全大规划,并且要加快发展智能电网,加大力度发展储能设施,此外还要发展分布式能源系统,实现城市输配系统电缆化、地下化。