Load Point Reliability Indices Research Articles

Reliability Comparison of Rural & Urban LVDS Networks with Corresponding HVDS Networks Including Substation Reliability

This paper mainly determines the comparison of reliability of an existing rural area & urban area LVDS (low voltage distribution system) with their respective proposed high voltage distribution system (HVDS) and also including their 33/11 kV Substation. Ring main substation and single bus bar substation configuration are considered for urban and rural distribution systems respectively. The reliability of ring bus substation used in urban area is more as compared to single bus substation used in rural area. The load point reliability indices are calculated considering both substation reliability indices and radial feeder indices. The substation failure rate is calculated by considering overlapping outages approach and whereas the radial feeder indices are calculated by using cut set approach. Further, the LVDS Network is converted into the HVDS Network by replacing a high rating distribution transformer (DTR) supplying to a group of customers with Large in number with multiple small rating distribution transformers near to consumer terminals with less number of customers in each group. This conversion leads to Minimum length of LT Lines in HVDS Which results in improving voltage profile, reliability and efficiency. In this paper the disconnecting switches and alternative supply are also considered on both LVDS and HVDS Networks in the calculation of the reliability of to assess the reliability of the radial distribution system (FMEA)Failure mode effect analysis is used. This study uses a LVDS and HVDS system, and uses an alternative power source and disconnectors, to determine reliability indices of the rural area network and urban area network distribution system. In this paper the important distribution reliability indices to reduce system average interruption durations (SAIDI), Energy Not Supplied (ENS) and ASAI for LVDS and corresponding HVDS are calculated. The research idea is proposed on a Indian practical networks.

Impacts of Transactive Energy Trading on the Load Point Reliability Indices of LV Distribution System

Impacts of Transactive Energy Trading on the Load Point Reliability Indices of LV Distribution System

Reliability Evaluation of Active Distribution Systems with Distributed Generations

Reliability evaluation is essential in designing, planning, operating modern power systems. System operators must operate the network securely and efficiently with minimal interruption events. With the recent advances in power electronics and control, distributed generations (DG) such as photovoltaic (PV), wind turbine, and storage systems are expected to grow in distribution networks. This high level of distributed generations penetration in the grid can increase the complexity of operating the system. This is caused by intermittent nature of solar irradiance and wind speed. This paper proposes a methodology used to assess distribution networks containing stochastic resources such as photovoltaic. This method will use the Monte Carlo simulation with a stochastic model to evaluate the distribution network’s reliability. The system and load point reliability indices such as frequency of loss of load and expected energy not to supplied will be computed in this technique. In addition, the configuration of distribution networks to improve system’s reliability to facilitate system restoration after pre-fault conditions will be assessed.

Assessment of Secondary Feeders Reliability in Nigeria: A case of Ado-Ekiti Metropolis Distribution Network

The major goal of power system is to ensure continuous supply of electricity at declared service quality to meet up with the demand of its customers. However, interruptions which sometimes may be unavoidable, tends to negate this trend. Identifying the problems will indeed enable the power utility companies to take the necessary steps in improving the reliability of the system. This paper used load point and customer-oriented reliability indices to evaluate the performance of the four distribution feeders within Ado-Ekiti metropolis, Nigeria, in order to identify the major causes of the frequent power supply outages and also suggested ways of improving its performance. Relevant outage data were collected from the supply utility-Benin Electricity Distribution Company of Nigeria (BEDC) daily operational logbooks from January 2021 to December 2021. Some of the data gathered were outage frequencies, fault durations, causes of outages, age of distribution transformers and number of customers on each of the feeders. Quantitative method of reliability indices was used to estimate and compare the performance of the feeders. The average availability (%) for the investigated period is 86.23%, 92.68%, 90.18% and 91.25% for Ajilosun, Basiri, Okesa and Adebayo feeders respectively. The results showed that almost all the feeders are not reliable. The study will enable the utility company in making informed decisions that will improve the reliability of the feeders and thereby facilitating effective monitoring to enhance optimum performance.

Reliability analysis of an active distribution network integrated with solar, wind and tidal energy sources

The global trends toward increasing clean and sustainable power generation have brought significant changes and developments in electrical distribution networks. The existing passive networks are being restructured to facilitate renewable distributed generations to ensure high degree of reliability of power supply to customers. A distribution system reliability assessment (DSRA) is crucial to analyze the risk and cost associated with power interruptions and take necessary preventive and corrective actions. This paper presents an approach to DSRA and carries out a comprehensive reliability assessment of an active distribution network (ADN) connected with solar, wind, and tidal energy sources. A multi-state reliability model is developed, combining the Markov and well-being frameworks to determine the reliability of a network energized by multiple renewable energy sources (RESs). The load point reliability and worth-oriented indices, namely SAIDI, SAIFI, CAIDI, AENS, EENS, ECOST and IEAR, are evaluated to analyze the impacts of the three RESs on the reliability of the ADN. The paper also proposes two new metrics to estimate the benefits of adding RESs from the reliability worth and cost perspectives. The analyses have been carried out on the Roy Billinton Test System. The results show that the maximum reliability worth and cost benefits can be extracted from a combined operation of multiple RESs. A combination of solar-wind-tidal energy sources, therefore, can be an effective solution for countries having long coastlines to fulfill not only the sustainable energy goals but also to improve the grid's reliability and reduce the monetary losses incurred due to customer interruptions.

Reliability assessment of different HVDC transmission system configurations considering transmission lines capacity restrictions and the effect of load level

The ongoing increasing demand for electrical energy and the reliable access to remote renewable energy generation points such as off-shore wind power stations or solar power generation, have revived the interest in HVDC multi-terminal systems. With the expansion of HVDC systems, their reliability assessment has become continuously important. One of the most important aspects of the reliability assessment of electrical systems is to have an accurate understanding of the engineering implications of the system and its associated components. The next step is to appropriately model the system components to represent their characteristics and functions in the overall system. In order to deliver a specified amount of electrical power, different methods can be considered. There are two general methods: 1) using several electrical power sources with low capacity, or 2) using fewer electrical power sources with high capacity. The decision to choose a certain method for transmitting electrical power depends on various parameters, and one of the most important parameters is reliability studies. This paper presents reliability modeling and analysis of HVDC transmission systems incorporating hybrid HVDC breakers to interrupt HVDC line faults. In this paper, comprehensive detailed reliability models of point-to-point, three-terminal, and four-terminal configurations are developed. Using this equivalent reliability model, various reliability indices are calculated at the load point of the system. Also, the effects of line constraints and incorporating DC circuit breakers of the DC transmission lines on the load point reliability indices have been evaluated. In the end, the effect of the load level on the reliability indices of the load point of each configuration has been assessed.

Reliability Assessment of some Selected 11 kV Feeders within Ibadan Distribution Network

The energy satisfaction that consumers can obtain from the central grid solely depends on how reliable the feeder to which such customers are connected, simply because the reliability of both generation and transmission is not enough to guarantee adequate and secure energy delivery. It is on this premise that this paper employed load point reliability indices to assess selected feeders within the Ibadan electricity distribution network. The required data for this analysis was collected from the Ibadan Electricity Distribution Company, at Ring Road, Ibadan, the collected data captured the total number of faults, total fault duration, and total operating time from 2016 to 2019. The load point reliability indices used as performance metrics include Failure Rate (FR), Mean Time Between Failures (MTBF), Mean Time to Repair (MTTR), Availability Factor (AVF), and Maintainability (M). An adequate comparison of each of these indices on each feeder was made for the period of investigation. It was discovered that many of these feeders were not reliable. Therefore, the need to carry out extensive maintenance on these feeders is non-negotiable. Also, the result of this analysis will help the Distribution Company (DisCo) to make informed decisions that will accelerate the reliability of these 11kV feeders across the investigated region.

Methodology to incorporate stuck condition of the circuit breaker in reliability evaluation of electrical distribution networks

The random failure of a circuit breaker (CB) in a power distribution network adversely impacts its ability to maintain supply continuity to its electricity customers. Among different CB failure modes, the failure to open, or the stuck condition, of a normally closed CB causes the operation of its backup breaker(s) leading to outages of multiple healthy feeders. Stuck condition is a low-probability failure event, but has wide-spread consequences when it occurs. This study proposes a generalised analytical methodology to identify the failure events due to the stuck breaker condition. The complexity of the reliability evaluation of a modern distribution system involving multiple switching arrangements is achieved through a search algorithm and repeated matrix operations that can readily be implemented in a computer program. The methodology is illustrated using a test distribution network. The usefulness of the methodology is demonstrated by quantifying the impact of the stuck breaker condition on load point and system reliability indices. The developed methodology can be a useful tool for industrial/commercial customers and utilities to incorporate the impact of breaker failures, including stuck breaker conditions, and make wise investment decisions in the upgrade and maintenance of the distribution network components and the protection system.

Reliability improvement of distribution system considering EV parking lots

Metropolitan cities have hundreds of parking lots (PLs), where each PL may have a capacity to hold hundreds of cars. Large-scale use of electric vehicles coupled with technological advancements in battery storage systems provide several technical and economic benefits of integrating PLs into the grid. This study presents the impacts of electric vehicle PLs on the distribution system reliability. The reliability indices of the distribution feeder are determined using recently proposed novel storage capacity model of a PL that accounts for the load and component outage data of the distribution feeder. The paper uses average interruption duration, average interruption frequency, and energy not served as feeder reliability indices. For load point reliability indices interruption frequency, interruption duration and energy not served are used. Numerical results, thus attained, show that for the backup operation mode of the PL; the feeder reliability indices and load point reliability indices improve up to 26% and 44% respectively.

Reliability evaluation of electricity-heat integrated energy system with heat pump

Integrated energy system (IES) has the advantages of improving the efficiency of energy utilization and promoting the consumption of renewable energy. It is of great importance to evaluate the reliability of an IES. This paper proposes a novel reliability evaluation method for the electricity-heat IES with heat pump. First, the load-point reliability indices and system-level reliability indices are defined according to the characteristics of electricity-heat IES. Second, the model of maximum output heat power of heat pump at the user-side considering the safety criterion of distribution network is established, and the step-varied repeated power flow method is applied to solve the model. Third, the reliability evaluation procedure of electricity-heat IES with heat pump based on the Monte Carlo simulation is presented. Case studies are carried out on the electricity-heat IES of an industrial park, and the results show that the configuration site, capacity and coefficient of performance of heat pump as well as the security constraints of distribution network can significantly affect the reliability indices.

Identification of Optimal Operating Condition of Six Bus System Based on Reliability Evaluation

Practical Transmission system interconnecting Ramagundam Thermal power plant, Kotagudam thermal power plant and Nagarjunasagar hydal power plant with Hyderabad, Karnool and Gooty load points is considered for present study. This six bus ring system is a part of the Telangana state transmission system. Reliability indices of the system for variable load at Hyderabad load bus are obtained. Based on the reliability indices the optimal operating condition of the system is identified. Operating the system at identified optimal operating point will nullify the installation of redundant components and adequacy improving components. Generation outage transmission outage and generation cum transmission outages are the possible contingencies which can occur during the operation of the considered practical composite power system. Telangana state transmission system is simulated for different possible contingencies with Power system simulation for Engineering software tool. Load point and system reliability indices evaluated for twelve different contingency cases. Referring to load point and system reliability indices, optimal operating point of ring system evaluated. Present study will indicate the load magnitude, upper boundary of load magnitude corresponding to reliable operation of the system.

Reliability Worth Analysis of Distribution Systems Using Cascade Correlation Neural Networks

Reliability worth analysis is of great importance in the area of distribution network planning and operation. The reliability worth's precision can be affected greatly by the customer interruption cost model used. The choice of the cost models can change system and load point reliability indices. In this study, a cascade correlation neural network is adopted to further develop two cost models comprising a probabilistic distribution model and an average or aggregate model. A contingency-based analytical technique is adopted to conduct the reliability worth analysis. Furthermore, the possible effects of adding distributed generation units into the network are evaluated. The proposed approach has been tested on a radial distribution test network evaluating the reliability worth. The results show that the probabilistic distribution model provides a more realistic model for the reliability analysis.

Differential Evolution Based Intelligent System State Search Method for Composite Power System Reliability Evaluation

This paper presents a new approach for evaluating the reliability indices of a composite power system that adopts binary differential evolution (BDE) algorithm in the search mechanism to select the system states. These states also called dominant states, have large state probability and higher loss of load curtailment necessary to maintain real power balance. A chromosome of a BDE algorithm represents the system state. BDE is not applied for its traditional application of optimizing a non-linear objective function, but used as tool for exploring more number of dominant states by producing new chromosomes, mutant vectors and trail vectors based on the fitness function. The searched system states are used to evaluate annualized system and load point reliability indices. The proposed search methodology is applied to RBTS and IEEE–RTS test systems and results are compared with other approaches. This approach evaluates the indices similar to existing methods while analyzing less number of system states.

Reliability Evaluation of Electrical Distribution Network Containing Distributed Generation Using Directed-Relation-Graph

This paper presents an analytical technique for reliability evaluation of electrical distribution network (EDN) containing distributed generation (DG). Based on hierarchical levels of circuit breaker controlling zones and feeder sections, a directed-relation-graph (DRG) for an END is formed to describe the hierarchical structure of the EDN. The reliability indices of EDN and load points can be evaluated directly using the formed DRG, and the reliability evaluation of an EDN containing DGs can also be done without re-forming the DRG. The proposed technique incorporates multi-state models of photovoltaic and diesel generations, as well as weather factors. The IEEE-RBTS Bus 6 EDN is used to validate the proposed technique; and a practical campus EDN containing DG was also analyzed using the proposed technique.

Value-based Distributed Generation Placements for Reliability Criteria Improvement

Restructuring and recent developments in the power system and problems arising from construction and maintenance of large power plants, increasing amount of interest in distributed generation (DG) source. Distributed generation units due to specifications, technology and location network connectivity can improve system and load point reliability indices. In this paper, the allocation and sizing of DG in distribution networks are determined using optimization. The objective function of the proposed method is to improve customer-based reliability indices at lowest cost. The placement and size of DGs are optimized using a Genetic Algorithm (GA). To evaluate the proposed algorithm, 34-bus IEEE test system, is used. The results illustrate efficiency of the proposed method.

Using the Modified Shuffled Frog Leaping Algorithm for Optimal Sizing and location of Distributed Generation Resources for Reliability Improvement

Restructuring the recent developments in the power system and problems arising from construction as well as the maintenance of large power plants lead to increase in using the Distributed Generation (DG) resources. DG units due to its specifications, technology and location network connectivity can improve system and load point reliability indices. In this paper, the allocation and sizing of distributed generators in distribution electricity networks are determined through using an optimization method. The objective function of the proposed method is based on improving the reliability indices, such as a System Average Interruption Duration Index (SAIDI), and Average Energy Not Supplied (AENS) per customer index at the lowest cost. The optimization is based on the Modified Shuffled Frog Leaping Algorithm (MSFLA) aiming at determining the optimal DG allocation and sizing in the distribution network. The MSFLA is a new mimetic meta-heuristic algorithm with efficient mathematical function and global search capability. To evaluate the proposed algorithm, the 34-bus IEEE test system is used. In addition, the finding of comparative studies indicates the better capability of the proposed method compared with the genetic algorithm in finding the optimal sizing and location of DG’s with respect to the used objective function.

Particle Swarm Optimization based Control Setting of TCSC for Improving Reliability of Composite Power System

the introduction of competition in the existing electrical market, it became necessary to increase the capability of transmission of power through the existing transmission lines. This paper describes a method of improving reliability of composite power system by increasing transmission system capability using FACTS devices. The utilization of FACTS (1) technologies will have a significant positive impact on power system performance in terms of reliability. Considerable efforts have been made in the past for developing techniques to evaluate composite power system reliability. The proposed method is based on the probabilistic approach to determine the load point reliability indices in a practical system. Composite system reliability can be increased by adjusting the settings of the FACTS device (such as reactance, phase angles, reactive power injection) with respect to the system parameters. In this paper, the settings of TCSC are obtained using Particle Swarm Optimization technique. The settings thus obtained are used for enhancing the transmission power capacity while improving the composite power system reliability. The proposed scheme is tested on Roy Billinton Test System (RBTS).

Optimal Placement of Distributed Generation Resources

Recent developments in the electric power and problems arising from construction and maintenance of large power plants have raised a great deal of interest in distributed power generation (DG). Distributed generation units due to specifications, technology and location network connectivity can improve system and load point reliability indices. In this paper, the placement and sizing of Distributed Generators (DG) in distribution networks are determined using optimization. The objective is to improve the reliability indices. The placement and size of DGs are optimized using a Genetic Algorithm (GA). To evaluate the proposed algorithm, the IEEE 34 buses distribution feeder,is used. The results illustrate the efficiency of the proposed method.)

Operational reliability assessment of power systems considering condition-dependent failure rate

Failure rate of a system component is usually assumed to be constant in conventional reliability evaluation of power systems. It has been realised from the real-time operation that a component will experience more failures during heavy loading condition than those during light loading condition, which means that the failure rate of a component in real-time operation is not constant and varies with loading condition. In order to evaluate system operational reliability related to load condition, the factors affected condition-dependent failure rate (CDFR) are investigated and a basic CDFR model is proposed in this study. In predictive operational reliability study, equipment loading condition for a given load period is determined using AC power flow based on the corresponding load level with considering load uncertainty. A four-state model has been proposed to represent a system component. The equations for determining the probability of each state for the four-state model have been derived. A technique based on these equations and models has been developed to evaluate operational and annual reliability indices of components, load points and system. The IEEE-RTS has been analysed to illustrate the proposed models and technique.

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.