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Securing a sufficient supply of reliable and affordable electricity is a major challenge for countries in sub-Saharan Africa (SSA), due to low current access levels, and rapid population and economic growth. This article will review application and technical modelling issues associated with generation adequacy assessment (i.e. assessing the risk of available generation being less than demand) in the context of SSA countries with significant capacities of renewable energy, with Kenya as the main case study. One major challenge in performing such studies in SSA is often availability of the necessary data on renewable resource and demand - the article will further demonstrate how useful information may be gained on the extent to which wind and hydro energy resources complement each other in Kenya, in the context of limited data availability. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a review of some fundamental concepts and practical applications in the area of common-mode and dependent (CMD) outage events in power systems. The paper is a result of ongoing activity carried out by the Probability Applications for Common and dependent Mode Events (PACME) Working Group (WG) of the Reliability, Risk and Probability Applications Subcommittee. The PACME WG was formed in 2010 to review, advance, and present the research and practical applications in the area of CMD outage events. This paper presents state-of-the-art in research, modeling, and applications of CMD outage events in power system planning and operation. Issues considered include: data monitoring and collection, and probabilistic modeling and evaluation in the planning, and operation of power generation and transmission systems. Additionally, some results obtained from outage data statistics corresponding to CMD outage events in systems such as Generating Availability Data System, Transmission Availability Data System, and Canadian Electrical Association are presented. [ABSTRACT FROM AUTHOR]

Power systems are planned such that they have adequate generation capacity to meet the load, according to a defined reliability target. The increase in the penetration of wind generation in recent years has led to a number of challenges for the planning and operation of power systems. A key metric for generation system adequacy is the capacity value of generation. The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. The variable and stochastic nature of wind sets it apart from conventional energy sources. As a result, the modeling of wind generation in the same manner as conventional generation for capacity value calculations is inappropriate. In this paper a preferred method for calculation of the capacity value of wind is described and a discussion of the pertinent issues surrounding it is given. Approximate methods for the calculation are also described with their limitations highlighted. The outcome of recent wind capacity value analyses in Europe and North America, along with some new analysis, are highlighted with a discussion of relevant issues also given. [ABSTRACT FROM PUBLISHER]

Distributed generation (DG) is increasing in penetration on power systems across the world. In rural areas, voltage rise limits the permissible penetration levels of DG. Another increasingly important issue is the impact on transmission system voltages of DG reactive power demand. Here, a passive solution is proposed to reduce the impact on the transmission system voltages and overcome the distribution voltage rise barrier such that more DG can connect. The fixed power factors of the generators and the tap setting of the transmission transformer are determined by a linear programming formulation. The method is tested on a sample section of radial distribution network and on a model of the all island Irish transmission system illustrating that enhanced passive utilization of voltage control resources can deliver many of the benefits of active management without any of the expense or perceived risk, while also satisfying the conflicting objectives of the transmission system operator. [ABSTRACT FROM AUTHOR]

This paper provides new insights into the electricity tracing methodology, by representing the inverted tracing upstream and downstream distribution matrices in the form of matrix power series and by applying linear algebra analysis. The nth matrix power represents the contribution of each node to power flows in the other nodes through paths of length exactly n in the digraph of flows. Such a representation proves the link between graph-based and linear equation-based approaches for electricity tracing. It also makes it possible to explain an earlier observation that circulating flows, which result in a cyclic directed graph of flows, can be detected by appearance of elements greater than one on the leading diagonal of the inverted tracing distribution matrices. Most importantly, for the first time a rigorous mathematical proof of the invertibility of the tracing distribution matrices is given, along with a proof of convergence for the matrix power series used in the paper; these proofs also allow an analysis of the conditioning of the tracing distribution matrices. Theoretical results are illustrated throughout using simple network examples. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for determining the capacity of a network to accommodate new generation under network security constraints. The assessment is performed by maximizing the total generation capacity in an optimal power flow model; this is solved by gradually adding limited numbers of line outage contingencies, until a solution to the complete problem is obtained. The limit on the number of contingencies added is key to the method's efficiency, as it reduces the size of the optimization problems encountered. Moreover, varying this limit on contingencies added provides a simple and highly efficient means of searching for multiple local optima of the nonlinear optimization problem. The method has been tested on a modified version of the highly meshed IEEE Reliability Test System with N-i security, where a significant reduction in the system's capacity for new generation is seen when security constraints are imposed. The method is generic and may be applied at any voltage level, for other security models and for other similarly structured problems such as the analysis of multiple resource availability scenarios. [ABSTRACT FROM AUTHOR]

The capacity of distributed generation (DG) connected in distribution networks is increasing, largely as part of the drive to connect renewable energy sources. The voltage step change that occurs on the sudden disconnection of a distributed generator is one of the areas of concern for distribution network operators in determining whether DG can be connected, although there are differences in utility practice in applying limits. To explore how voltage step limits influence the amount of DG that can be connected within a distribution network, voltage step constraints have been incorporated within an established optimal power flow (OPF) based method for determining the capacity of the network to accommodate DG. The analysis shows that strict voltage step constraints have a more significant impact on ability of the network to accommodate DG than placing the same bound on voltage rise. Further, it demonstrates that progressively wider step change limits deliver a significant benefit in enabling greater amounts of DG to connect. [ABSTRACT FROM AUTHOR]

Increasing connection of variable distributed generation, like wind power, to distribution networks requires new control strategies to provide greater flexibility and use of existing network assets. Active network management (ANM) will play a major role in this but there is a continuing need to demonstrate the benefit in facilitating connection of new generation without the need for traditional reinforcements. This paper proposes a multi-period AC optimal power flow (OPF)-based technique for evaluating the maximum capacity of new variable distributed generation able to be connected to a distribution network when ANM control strategies are in place. The ANM schemes embedded into the OPF include coordinated voltage control, adaptive power factor and energy curtailment. A generic U.K. medium voltage distribution network is analyzed using coincident demand and wind availability data derived from hourly time-series. Results clearly show that very high penetration levels of new variable generation capacity can be achieved by considering ANM strategies compared to the widely used passive operation (i.e., "fit and forget"). The effects on network losses are also discussed. [ABSTRACT FROM AUTHOR]