Customer Interruption Costs Research Articles

Optimal Distribution System Reliability Planning: A Differential Evolution Based Approach

This article presents a differentialevolution (DE) based approach for optimal distribution system reliability planning, taking both customer interruption costs and utility costs into consideration. The purpose is to allocate main feeder sectionalizing switches and lateral fuses so as to minimize total costs for different conditions and configurations. For instance, the effects of load transfer and the treatment approach for a failed distribution transformer will be examined. The proposed approach is tested on two reliability test systems, and case studies are investigated. The results obtained show the proposed approach can provide information for value-based decision making in distribution systems reliability planning.

Technique to evaluate nodal reliability indices and nodal prices of restructured power systems

Power system restructuring has changed the mechanism of system reliability management and electricity pricing. The electricity price and supply point reliability are correlated due to customer participation in market trading in the new environment. A new technique used to determine both nodal prices and nodal reliability indices of deregulated power systems has been developed based on a probabilistic reliability evaluation approach and optimal power flow method. Customer demand response to price changes in terms of customer interruption cost has been included in the technique to re-dispatch generation and to shed load for releasing network violations caused by contingency states. Instead of using nodal price for the normal operation state, the expected nodal price and the associated standard deviation are used to represent the volatility of nodal price due to random failures. A reliability test system (RBTS) has been analysed to illustrate the technique.

Comparison of subtransmission system reliability worth for diverse systems by including health considerations

The fundamental concepts associated with quantitative reliability assessment of electric power systems are reasonably well established and accepted by the power industry. The evaluation of the costs and benefits of competing investments has now become a standard practice in power system planning. In order to make a consistent appraisal of economics and reliability, it is imperative to compare the investment cost needed to attain a specified level of reliability with the reliability worth or benefits derived by the society at that level of system reliability. Customer interruption costs, which serve as surrogates for the perceived worth of supply reliability, have been determined for several jurisdictions, areas, provinces, and countries as diverse as Canada, United Kingdom, Nepal, and Thailand, among others. This paper extends the well-being framework to include the societal worth of electric service reliability in subtransmission systems associated with the above four countries/systems. Systems well-being is defined in terms of the three system states of healthy, marginal, and at risk, thus combining the deterministic and probabilistic approaches into a single framework. The main objective of the paper is to present results of reliability worth indices of expected cost of interruptions (ECOST) and interrupted energy assessment rate (IEAR), for both the healthy and at risk states in the well-being framework. The concepts associated with extending the well-being framework to include reliability worth parameters are illustrated by application to a small reliability test system designated RBTS. Customer interruption data from the four countries are used in conjunction with the RBTS subtransmission system in order to obtain the reliability worth indices.

Current Practices and Customer Value-Based Distribution System Reliability Planning

Among the major issues facing utilities in today's competitive electricity market is the pressure to hold the line on rates and provide electricity with adequate quality and reliability. Utilities are increasingly recognizing that the level of supply reliability planned and designed into a system has to evolve away from levels determined basically on a technical framework using deterministic criteria, and toward a balance between minimizing costs and achieving a sustainable level of customer complaints. Assessment of the cost of maintaining a certain level of supply reliability or making incremental changes therein must include not only the utility's cost of providing such reliability and the potential revenue losses during outages, but also the interruption costs incurred by the affected customers during utility power outages. Such a cost-benefit analysis constitutes the focal point of the value-based reliability planning. Value-based reliability planning provides a rational and consistent framework for answering the fundamental economic question of how much reliability is adequate from the customer perspective and where a utility should spend its reliability dollars to optimize efficiency and satisfy customers' electricity requirements at the lowest cost. Costs to customers associated with varying levels of service reliability are significant factors that cannot be ignored. Explicit considerations of these customer interruption costs in developing supply reliability targets and in evaluating alternate proposals for network upgrade, maintenance, and system design must, therefore, be included in system planning and design process. The paper provides a brief overview of current deterministic planning practices in utility distribution system planning, and introduces a probabilistic customer value-based approach to alternate feed requirements planning for overhead distribution networks.

산업수용가의 정전비용 산출을 위한 조사 분석 연구

정전에 따른 직접적이고 단기간의 정전비용을 평가하기 위해 산업용 수용가를 대상으로 설문조사 결과를 요약한 것이다. 설문지는 주로 수용가의 전기전문가를 대상으로 예상되는 예비 조치에 바탕을 두고 작성되었다. 정전의 기간과 빈도를 고려한 신뢰성에 대한 경제성 평가는 어떠한 종류의 정전에 의해 유발되는 특히 대규모 산업용 수용가의 손실과 경제적인 충격을 정확히 반영하지 못했다. 수용가집단에 초래되는 비용의 큰 차이를 내포시키기 위해 본 정전비용을 분석함에 있어서 IEC, IEEE와 같은 국제 규격을 활용하였다.

Optimal Operating Strategy for Distributed Generation Considering Hourly Reliability Worth

This paper presents a method to determine optimal operating strategy for distributed generation (DG) incorporating reliability worth evaluation of a distribution system. The use of DG for peak shaving could reduce the overall system operating cost and its use as standby power could reduce the customer interruption cost. If the DG operating cost is less than the utility power cost at peak time, DG should be employed to reduce the overall system operating cost. However, when customer interruption cost is also an important concern, standby power strategy for DG may be better than peak shaving. The reliability worth and the power cost evaluations are needed to determine whether DG should be operated for peak shaving or as standby power. The hourly reliability worth is incorporated in the strategy proposed in this paper to determine the optimal operating decision for the DG. Using the approach proposed in this paper, the distribution companies could determine the optimal operating strategy for their DG.

Rural distribution system reliability worth evaluation using individual customer outage cost characteristics

Customer interruption costs are a function of both interruption and user characteristics. The specific customer characteristics at a load point in a distribution network can have a significant effect on the estimated customer outage costs at that load point and for the entire feeder. This paper illustrates the effects on outage cost estimates of using generalized sector customer outage cost estimates and actual customer specific outage cost functions. The data used in these analyses are from customer cost surveys conducted in Canada. A small distribution system is used to illustrate the possible variation in interruption cost estimates due to incorporating specific customer characteristics in the evaluation. The results presented clearly show that different customer compositions can result in significantly different feeder interruption cost estimates. The estimated interruption costs can be used in feeder design to create an optimal configuration based on reliability cost/worth analysis.

Comparative case studies for value-based distribution system reliability planning

Abstract This paper will develop a set of reliability worth evaluation models to evaluate the load point reliability worth indices for five different distribution types. The distribution substations, primary distribution systems, and the interaction between them contribute to the load point reliability worth indices. The reliability worth of the distribution systems are evaluated in terms of customer interruption costs, by using the sector customer damage function (SCDF). The most suitable system design is based on comparisons of the total system costs of the candidates under consideration. Four case studies are thoroughly examined in this paper. Also, the impact on customer interruption costs associated with customer type, substation configuration, and feeder configuration are investigated.

Evaluation of the Reliability of Distribution System Taking into Consideration Customer Interruption Cost

It is raised for methodology to evaluate power system reliability using interruption cost according to power industry is rushed into competition appearance. This paper presents algorithms to evaluate the reliability of powerdistribution system taking into consideration customer interruption costs. The customer interruption cost is considered as one of the most valuable indices to estimate the reliability of a powerdistribution system from the customers' standpoint. In the concrete, this paper presents new algorithm that takes into account the load bycustomer type and failure probability by distribution facilities when calculating the amount of unserved energy by customer type. Finally, evaluation results of unserved energy and system interruption cost based on customer interruption cost are shown in detail.

Reliability worth assessment of high-tech industry

This paper introduces a new approach to customer interruption cost evaluation that recognizes the dispersed nature of the cost data. The proposed method is designated as the possibility distribution approach and provides a realistic and effective assessment of the losses incurred by high-tech industry electrical users due to power failures. Fuzzy linear regression models are used to describe the distribution and dispersed behaviors of interruption costs. Bootstrap technique is used to generate a sampling distribution of small samples so that confidence intervals of interruption costs of different high-tech sectors can be obtained. Using the obtained cost models, interruption costs and reliability worth of high-tech industries that require higher reliability and premium power service, can be properly assessed.

Composite system reliability evaluation incorporating a six-phase transmission line

Composite system reliability studies incorporating a six-phase transmission line are presented. Both load-point and system indices are used to examine the impact on the individual bus and overall system reliability of incorporating a six-phase transmission line. Comparative studies are conducted in order to investigate the impact of the location of a six-phase transmission line on the load-point and system reliability indices. The worth of employing the six-phase transmission line is expressed in terms of the reduction in the customer interruption cost. The results are illustrated using a small test system.

Estimating customer outage costs due to a specific failure event

Customer interruption costs due to failure in electrical energy supply depend on many factors. A procedure is developed to estimate the customer outage costs on a distribution feeder subjected to a specific outage event. The data required to perform a detailed evaluation is illustrated and discussed, including the customer composition on the feeder, the customer demand profiles at the feeder load points and the relevant customer damage functions. The procedure presented in the paper is illustrated by application to a specific distribution feeder in the city of Saskatoon. The customer costs associated with power supply failures are a function of the time of day, day of the week and time of year. They are also strongly influenced by the duration of the outage event. The effect of outage duration and the time of outage occurrence is illustrated.

Reliability Worth Assessment of High-Tech Industry

This paper introduces a new approach to customer interruption cost evaluation that recognizes the dispersed nature of the cost data. The proposed method is designated as the possibility distribution approach and provides a realistic and effective assessment of the losses incurred by high-tech industry electrical users due to power failures. Fuzzy linear regression models are used to describe the distribution and dispersed behaviors of interruption costs. Bootstrap technique is used to generate a sampling distribution of small samples so that confidence intervals of interruption costs of different high-tech sectors can be obtained. Using the obtained cost models, interruption costs and reliability worth of high-tech industries that require higher reliability and premium power service, can be properly assessed.

Discussion of "Application of customer interruption costs in transmission network reliability planning" [and closure

Shih-Min Hsu comments on the paper by A. A. Chowdhury et al. (see ibid., vol.37, p.1590-6, 2001). He comments on transmission systems reliability and the use of average loads with respect to cost/benefit analysis. The original authors reply to the comments.

Closure to discussion of "Application of customer interruption costs in transmission network reliability planning"

Closure to discussion of "Application of customer interruption costs in transmission network reliability planning"

Feeder-switch relocation for customer interruption cost minimization

Most electricity service interruptions are due to failures in the distribution network. In a competitive market, service quality and reliability have become an essential part of the business. In order to enhance the reliability in the distribution system, a value-based method is proposed in this paper to take load distribution changes into account and search for new locations of feeder sectionalizers such that the customer interruption costs (CIC) can be reduced. Two stages are involved in the search. Using local information, the first stage determines the search direction and, in the second stage, it decides whether a crossover of the load point is beneficial. To avoid being trapped in a local minimum, a mutation technique is also applied to look for the global optimum. Actual feeders were used in the tests and test results have shown that with a proper adjustment of the feeder sectionalizers, service reliability can be improved and the customer outage costs are reduced.

Feeder Switch Relocation for Customer Interruption Costs Minimization

Most electricity service interruptions are due to failures in the distribution network. In a competitive market, service quality and reliability have become an essential part of the business. In order to enhance the reliability in the distribution system, a value-based method is proposed in this paper to take load distribution changes into account and search for new locations of feeder sectionalizers such that the customer interruption costs (CIC) can be reduced. Two stages are involved in the search. Using local information, the first stage determines the search direction and, in the second stage, it decides whether a crossover of the load point is beneficial. To avoid being trapped in a local minimum, a mutation technique is also applied to look for the global optimum. Actual feeders were used in the tests and test results have shown that with a proper adjustment of the feeder sectionalizers, service reliability can be improved and the customer outage costs are reduced.

Application of customer interruption costs in transmission network reliability planning

A method that can be utilized to ascertain the optimum level of power supply reliability is used to compare the incremental cost of providing reliability with the incremental benefit of that reliability. The benefit of an increment of reliability can be considered to be the change in the customer interruption cost related to the change in the reliability level. Reliability cost-reliability benefit assessment is, thus, an important aspect of electric power supply planning process. Customer interruption costs form an essential input to this reliability cost-reliability benefit assessment process. This paper illustrates the utilization of customer interruption cost information in transmission network reliability planning using Canada's Alberta Interconnected Transmission Grid. The methodology presented in this paper can readily be applied to industrial and commercial power systems.

Optimum load-shedding technique to reduce the total customer interruption cost in a distribution system

In capacity deficiency conditions caused by unscheduled outages in a generation and transmission system, system operators have to shed load at selected feeders in the distribution system to maintain acceptable operating conditions. Different load-shedding schemes can result in quite different load point reliability performance. Conventionally, the objective is to shed the minimum load subject to system security constraints. An optimum load-shedding technique is presented that can be used to improve the reliability of a local distribution system. Customer concerns regarding interruption costs are considered in the load-shedding procedure. The objective is to minimise the total system interruption cost. Cost weight factors are used to determine the load-shedding priority among feeders, and an enumeration technique is used to divide the capacity deficiency between feeders. The unreliability cost indices of two representative distribution systems are evaluated to illustrate the technique.

A power quality and reliability index based on customer interruption costs

Standard reliability indexes such as SAIDI ignore the variation in interruption costs with customer type. Thus, expenditure decisions driven by these indices that impact reliability, will not lead to the optimum improvement in value of service to customers. An index equal to customer interruption costs divided by energy sales (CICs/kWh) overcomes this deficiency. It is equally useful for identifying best-business-value solutions to power quality problems. It enables a supplier to decide which portfolio of projects (affecting power quality, or reliability, or neither) earns the highest return on investment, and allows a direct comparison of its value-creation record with that of its competitors.