Reliability

Energy Policy 39 (2011) 1562–1568

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Energy Policy
journal homepage: www.elsevier.com/locate/enpol

A heuristic-based approach for reliability importance assessment of
energy producers
A. Akhavein a, M. Fotuhi Firuzabad b,n
a
b

Department of Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Department ofElectrical Engineering, Sharif University of Technology, Tehran, Iran

article info

abstract

Article history:
Received 20 May 2010
Accepted 13 December 2010
Available online 11 January 2011

Reliability of energy supply is one of the most important issues of service quality. On one hand, customers
usually have different expectations for service reliability and price. On the other hand,providing different
level of reliability at load points is a challenge for system operators. In order to take reasonable decisions
and obviate reliability implementation difficulties, market players need to know impacts of their assets on
system and load-point reliabilities. One tool to specify reliability impacts of assets is the criticality or
reliability importance measure by which systemcomponents can be ranked based on their effect on
reliability. Conventional methods for determination of reliability importance are essentially on the basis
of risk sensitivity analysis and hence, impose prohibitive calculation burden in large power systems. An
approach is proposed in this paper to determine reliability importance of energy producers from
perspective of consumers or distributioncompanies in a composite generation and transmission system.
In the presented method, while avoiding immense computational burden, the energy producers are
ranked based on their rating, unavailability and impact on power flows in the lines connecting to the
considered load points. Study results on the IEEE reliability test system show successful application of the
proposed method.
& 2010 ElsevierLtd. All rights reserved.

Keywords:
Component ranking
Reliability importance
Energy producers

1. Introduction
Power systems traditionally were operated in a vertically
integrated or regulated structure. In this structure, few utilities
are responsible for generation, transmission and distribution of
electricity. Each utility has a monopoly for the supply of electrical
energy over agiven geographical region (Kirschen and Strbac,
2004; Shahidehpour et al., 2002). In order to enhance economical
efficiency and fulfill growing expectation of service quality, many
power systems worldwide have undergone restructuring or deregulation. In the restructured environment, generation, transmission
and distribution activities and services are unbundled and hence,
several entities ormarket players are engaged in a power market
(Kirschen and Strbac, 2004; Shahidehpour et al., 2002). Generation
companies (GenCos) own generating units or power plant(s) and
play prominent role of the energy producer in the power system.
Transmission companies (TransCos) own transmission grid where
electrical energy is transferred from GenCos to bulk load points.
Distribution of theelectricity among customers in a specific
geographical region is the duty of distribution companies (DisCos).

n

Corresponding author. Tel.: + 98 21 66165901; fax: + 98 21 66023261.
E-mail addresses: a_akhavein@azad.ac.ir, ali.akhavein@gmail.com (A. Akhavein),
fotuhi@sharif.edu (M. Fotuhi Firuzabad).
0301-4215/$ - see front matter & 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.enpol.2010.12.030

Efficiency and reliability of the power system operation is delegated to the independent system operator (ISO) (Batlle et al., 2007;
Chow et al., 2005; Kirschen and Strbac, 2004; Shahidehpour et al.,
2002). The ISO administrates the energy markets, the ancillary
service market and the transmission system (Shahidehpour et al.,
2002). ISO and TransCo may be integrated into one...