城市电网用户停电损失估算及评价方法研究

合理地估算和评价城市电网中各类用户的停电损失,为电力企业在提高城市电网的可靠性水平及应急电源优化配置的投资和决策方面提供依据。在对受停电影响造成的各类用户的经济损失进行分类调查的基础上,以峰荷时刻的停电损失为基准,建立了表示综合用户停电损失和停电持续时间关系的综合用户停电损失函数,用以估算每类用户的综合停电损失。基本计算过程为,根据各类用户的综合用户停电损失函数和停电次数的统计结果,采用停电损失评价率和每次事故停电损失2个指标来评价每类用户的停电损失。采用青岛地区53个重要用户的数据为实际算例,估算并评价了各类用户的停电损失。所得结果表明,所提出的估算和评价用户停电损失的方法,有助于电力企业确定不同可靠性水平下的应急电源优化配置成本。     

Outage costs quantification for benefit–cost analysis of distribution automation systems

Deregulation of electric power industry has motivated electricity customers to pay more attention in evaluating both the direct cost of electric service and the monetary value of reliable electric service. This movement has been recognized by the utilities and the value-based aspects are introduced into the planning and design of power systems to consider the outage costs. The value of service reliability that can portray and respond to actual utility and customer impacts as a result of power interruptions plays a major role on justifying whether a distribution automation (DA) system is beneficial or not. However, for the value of service reliability, there are a number of factors that can affect it. To exactly evaluate the service reliability value, two formulas for quantifying the customer interruption costs and utility reduced energy revenues associated with power failures are derived in this paper. The customer types, feeder loads, feeder failure rate, number of switch, restoration time, and repair time are taken into account. The proposed formulas can provide an exact estimate in outages costs of a feeder and their computation is simplified and straightforward. The estimated outage costs can then be used to calculate the reliability improvement benefit of DA systems for the system benefit–cost analysis. A practical DA system implemented by Taiwan Power Company is used to illustrate the proposed formulas and the benefit–cost analysis result is presented. Sensitivity analysis is also performed to reduce the effects of benefit–cost analysis parameters on the analysis result.     

分界负荷开关在10 kV架空线路上的应用

分界负荷开关在10 kV馈电架空线路上的应用可大大减少无故障线路连带性的事故停电、缩小故障停电范围、缩短用户停电时间,从而提高所带用户的供电可靠性。     

Impact of two-stage service restoration on distribution reliability

This paper examines the reliability improvements gained by using a two-stage restoration strategy rather than a single-stage restoration strategy following fault inception. In a two-stage strategy, a first stage quickly restores a limited set of customers using automated switches. A later stage restores additional customers using manual switches. The strategies are compared using a predictive reliability assessment algorithm capable of modeling each strategy. The impact of two-stage restoration is examined on a 10-MVA test feeder for various levels of feeder automation. Tests show that two-stage restoration significantly reduces customer interruption time for partially automated feeders. Further, single-stage restoration models underestimate the reliability benefits attainable through partial feeder automation     

Distribution Feeder Scheduling Considering Variable Load Profile and Outage Costs

In a deregulated power market, customers would have more choices for their power service and the improvement of service quality has become a challenge to power transmission and distribution companies. Distribution system reliability that was traditionally considered within the planning activities is now incorporated in the operational environment. This paper presents study results of a multiobjective feeder operation optimization problem that considers how to balance network efficiency, switching and reliability costs in a distribution network. The proposed method divides annual feeder load curve into multiperiods of load levels and optimizes the feeder configurations for different load levels in annual operation planning. Customer load profiles and seasonal varying data of feeder section failure rates and customer interruption costs are considered. Numerical simulations demonstrate the time-varying effects on the optimal distribution feeder configuration and operation costs. A binary particle swarm optimization (BPSO) search is adopted to determine the feeder switching schedule. Test results indicate that not considering time-varying effects and using only simplified fixed load and reliability parameters could underestimate the total loss to the utility and its customers.     

缺电成本及其估计方法

缺电成本用于稀量断电或限电时用户的经济损失。在电力市场中，它是一个很重要的参数，与供电可靠性、负荷控制和电价规划密切相关的。我国在这方面的研究还处一开始阶段。本介绍了缺电成本的概念、影响因素和估计方法。     

Heuristic rule-based phase balancing of distribution systems by considering customer load patterns

In this paper, a heuristic backtracking search algorithm is proposed to adjust the phasing arrangement of primary feeders and laterals for phase balancing of distribution systems. The phase unbalance index of distribution feeders is calculated based on the phasing current magnitude of each line segment and branch, which has been solved by a three-phase load flow program. The database of an automated mapping/facility management (AM/FM) system is used to retrieve the component attributes, and the topology process is executed to determine the electrical network configuration and the customers served by each distribution transformer. By using the monthly energy consumption of customers in customer information system (CIS) and the typical daily load patterns of customer classes, the hourly loading profiles of distribution transformers and service zones can be derived to solve the individual phase loadings of each primary feeder and lateral. The phase balancing of distribution systems is enhanced by heuristic rule-based searching process to minimize the phase unbalance index. To demonstrate the effectiveness of proposed methodology, a practical distribution feeder with 2754 customers is selected for computer simulation to enhance three-phase balancing of distribution systems. It is concluded that three-phase balancing of distribution systems can be obtained by considering customer load characteristics.     

Interruption costs of service sector electricity customers,a hybrid approach

A power outage brings in economic losses for both the customers and the utilities. Studying these unwanted events and making solid predictions about the outcomes of the interruptions has been an attractive area of interest for the researchers for the last couple of decades. By making use of a customer survey study conducted in Finland, this paper benefits from both the reported cost data collected from customers and from the analytical data that are available and then presents a new hybrid approach to estimate the customer interruption costs of service sector customer segment. Making use of Value Added information of the customers is a common practice for the cost normalization purposes. This paper verifies the approach by comparing the findings of the customer survey and the econometric model suggested here. This study is a unique source in terms of providing a reliable, easy to apply, and a straightforward model for calculating the economic impacts of power outages.     

Distribution feeder reliability studies

As the power industry moves into a new competitive era, the reliability of radial distribution feeders becomes a primary issue in comparing the “new” versus the “old” way of serving customers. In order to make the comparison, a distribution engineer needs to have the analysis tools to perform the necessary reliability studies. For the purposes of this paper, the reliability studies will be limited to the calculation of the annual “outage rate” and associated “restoration time” for a typical customer on a radial distribution feeder. This paper develops the background and theory for computing these reliability indices. The method can be applied to demonstrate how different devices and/or feeder configurations affect the average customer on a specific feeder     

A new integer-value modeling of optimal load shedding to prevent voltage instability

This paper presents a novel integer-value modeling for optimal under voltage load shedding (UVLS) problem. The real-value modeling of UVLS is encountered to some drawbacks which lead to an ineffective practical solution. The proposed integer-value modeling overcomes these drawbacks by considering the load feeders of load buses in the modeling as well as assigning interruption penalty factors and participation penalty factors to feeders and buses respectively. Applying these factors to the proposed UVLS integer-value modeling result achieving objectives such as minimizing the total number of participating feeders in the load shedding, minimizing the total number of participating buses in the load shedding, minimizing the total amount of load to be shed, minimizing the total interruption cost and combination sets of the objectives. Without any limitation of applying the proposed modeling to large scale networks, it is implemented on IEEE 14-bus and 30-bus test systems and the results verify the effectiveness of the proposed method.     

配电网用户感知停电事故严重性分析及可靠性评估

可靠性评估对于指导配电网规划设计具有重要意义。传统配电网可靠性评估主要从系统侧供电的角度,建立评估指标体系并进行分析,较少考虑停电发生时用户侧的用能需求差异,忽视了不同用户对于同一停电事故严重性的差异化感知,进而造成了传统可靠性指标不能完全准确反映停电事件对于不同用户在不同时段的差异化影响。为解决上述问题,首先,提出了用户感知可靠性的概念,并提出了一种用户对停电事故严重性感知的量化方法,以分析不同用户对停电事故的严重性感知程度及停电容忍程度;然后,分别从用户侧和系统侧提出了一系列基于用户感知的配电网可靠性评估新指标,建立了相应指标体系,并围绕该体系对配电网系统的可靠性评估开展了研究;最后,运用IEEE-RBTS标准算例对所提出的方法、指标进行了计算验证,证明了其可行性及正确性;并通过与传统可靠性指标的对比分析,体现了用户感知可靠性指标相较于传统评估指标的客观优势。     

Features that influence composite power system reliability worthassessment

Reliability worth assessment using customer interruption costs is an important element in electric power system planning and operation. This paper deals with two features that affect the composite generation-transmission system reliability worth assessment. One feature is the incorporation of temporal variations in the cost of interruption. This paper illustrates the effect on the expected annual system outage cost of temporal variation in the interruption costs for the residential, agricultural, industrial, commercial and large user sectors. The other aspect considered in this paper is using a probability distribution approach to represent the cost of interruption model. The conventional customer damage function approach utilizes average customer costs while the probability distribution approach recognizes the dispersed nature of the customer outage data. These two methods of cost evaluation are applied to reliability worth assessment in this paper. A sequential Monte Carlo approach incorporating time varying loads is used to conduct all the studies. Case studies performed on two composite test systems show that incorporating time varying costs of interruption for the industrial sector resulted in a significant reduction in the expected outage cost. A comparison of the reliability worth obtained using the customer damage function method (CDF) with the probability distribution approach suggests that using the CDF method may significantly undervalue the reliability worth by a factor of three to four     

A smooth bootstrapping based technique for evaluating distribution system reliability indices neglecting random interruption duration

Average interruption duration, interruption duration per year and failure rate at a load point are the basic reliability indices required to be evaluated. These indices depend on failure rate and average repair time of each feeder. Usually in reliability assessment of distribution system failure and repair rates are assumed constant. Further it has been observed that random outage time may be neglected at load point. This has been an important issue in determining the modified reliability indices accounting random outage time. Hence this paper presents a methodology to determine basic reliability indices subject to neglecting of certain repair time which is truly a random variable. The methodology is based on smooth boot strapping technique along with Monte Carlo simulation (MCS). The developed algorithm has been implemented on two sample test systems. The results obtained has been compared those with MCS and obtained with general boot strapping.     

Distributed nature of residential customer outage costs

Reliability worth assessment is an important factor in power system planning and operation. An equally important issue is how to use customer costs of electric supply interruptions as surrogates to appropriately quantify reliability worth. Postal or in-person surveys of electric customers are often used to determine interruption costs. The results obtained from the surveys are transformed into customer damage functions which are applicable to individual customer classes and sectors. Standard customer damage functions use aggregate or average customer costs for selected outage durations. This paper develops a practical alternative to the customer damage function method of describing the interruption cost data. The alternate technique, which is designated as the probability distribution approach, is capable of recognizing the dispersed nature of the data. The proposed probability distribution method is illustrated in this paper using the interruption cost data collected in a 1991 survey of the Canadian residential sector     

电力系统应急服务多点最优选址规划

合理规划电力系统应急服务点对于保证应急资源及时运送,进而降低停电损失具有重要意义。现有电力系统应急方面的研究多侧重于应急平台建设和相关指标体系构建,而对应急服务点选址优化问题则研究较少。在此背景下,通过综合考虑用户停电损失、停电时限约束及应急服务点的服务成本,建立了以电力应急总成本最小为优化目标的应急服务多点选址的优化模型,并采用Floyd算法求解该优化模型。最后,用算例说明了所构建模型的正确性与所采用算法的有效性。     

计及分布式电源的变电站个数及馈线条数概率规划

随着分布式电源渗透率的提高,分布式电源对配电网规划方法和结果的影响研究更具现实意义。采用概率规划方法,建立了涉及分布式电源的变电站个数及馈线条数优化简化模型,模型目标为变电站和中压线路的相关总费用最小,并考虑了线路的容量约束;提出了中压主干线与分支线长度的近似计算模型,并考虑了负荷变化、分布式电源随机性和线路负荷转供率对停电时间和停电费用的影响。基于模型求解获得的变电站优化个数、馈线优化条数和最小总费用,定义了相应的三大类置信变量。算例表明了概率规划对于变电站个数和馈线条数选择的意义以及分布式电源的替代作用。     

Distribution system reliability cost/worth analysis usinganalytical and sequential simulation techniques

The requirements for extensive justification of new facilities and emphasis on the optimization of system cost and reliability are steadily increasing. Customer interruption cost analysis provides valuable input to electric power supply reliability worth assessment. This paper presents both a generalized analytical approach and a time sequential Monte Carlo simulation technique for evaluating the customer interruption cost in complex radial distribution systems. Studies are conducted on two practical distribution systems. The results obtained using the analytical technique incorporating average restoration times are compared with those obtained using the time sequential simulation method and random restoration times. The effects on customer interruption cost indices associated with alternate supply and protection devices are also considered     

一种快速启发式配电网故障恢复算法

提出一种基于网络拓扑分析快速有效的配电网故障恢复算法。该算法在满足系统电流、电压的约束条件下,充分考虑负荷的优先级别,使得在开关操作次数尽可能少的情况下,尽可能多的恢复对重要负荷的供电以及其他负荷的供电,尽可能减小全系统的停电损失。算例计算表明该算法是高效和可行的。     

利用PLC AMR进行停电管理

自动抄表(AMR)是对电信、无线通信及电力线路等所连接用户表计消费数据的远程采集.提出了有效利用客户有效信息和基于电力线通信(PLC)的AMR进行停电管理,利用基于电力线通信的AMR轮询特性来确定停电的范围.通过检测故障呼叫附近的表计就可以确定受停电影响的用户,通过回溯追踪至公共点就能对停电进行定位.PLC AMR的利用能缩短停电时间,提高用户的满意度,并且能节约投资.     

基于虚拟控制单元与启发式搜索的线路过载紧急控制策略

为了快速消除由潮流转移引起的线路过载,给出了基于虚拟控制单元与启发式搜索的紧急控制策略。首先,引入虚拟控制单元的概念:节点的出力调整量等于最大线路过载量时,能够完全消除线路过载的控制单元。然后,给出了最优可控单元的双层搜索策略:第一层,通过设置合理的阈值,筛选减载能力较强的控制节点对构成优先控制单元集;第二层,综合考虑控制单元的减载效果和消除过载能力,给出了基于虚拟控制单元的启发式搜索步骤,得到优先控制单元集中的最优可控单元。若所选的阈值范围内无法找到可控单元,则适当扩大第一层搜索范围,依次类推,直至得到满足要求的控制单元。考虑正常线路冗余量约束来计算调整量,避免了潮流校验。经过一次调整后,依据灵敏度关系修正线路潮流与节点的最大可调整出力,提高控制速度。IEEE 30节点系统的仿真验证了所提算法的有效性。