Energy and Power Engineering, 2013, 5, 1022-1025
doi:10.4236/epe.2013.54B195 Published Online July 2013 (http://www.scirp.org/journal/epe)
Application of Risk-based Flexibility Assessment
Methods to Evaluate System Expansion Plans
Baorong Zhou1, Pei Zhang2, Jian b in C h en1, Xiaoming Jin1, Kai Hou2, Ming Niu3,
Zhao Xu3, Yunkai Lei2
1Electric Power Research Institute of China Southern Power Grid, Guangzhou, China
2Tianjin University, Tianjin, China
3Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
Email: brzhou@csg.cn, peizhang166@gmail.com;
Received April, 2013
ABSTRACT
This paper proposed a flexibility assessment approach based on and risk assessment methodology. System planners
prioritize each planning scheme with consideration of three aspects: reliability, economics, and flexibility. In the past,
there is lack of quantitativ e indices to measure flexibility of a power system. This pap er proposes applying probabilistic
risk assessment method to quantify system flexibility. The proposed approach is demonstrated to compare two trans-
mission plann ing schemes during Guangdong expansion planning process.
Keywords: Flexibility Assessment; Transmission Scheme Prioritization
1. Introduction
Development of power systems is of the foundations of
the national economy. Thus power system planning is
always one of the most important aspects of electric in-
dustry. In order to guarantee the reliability and economy
of the power supply, as well as to meet the rapidly in-
creasing demand of electric industry, power system
planners generally establish several planning schemes,
among which, only the most reliable, economical and
flexible one will be implemented. Therefore, it is great
importance for planners to apply reasonable methods to
perform assessment and prioritization for those schemes.
Regarding assessment and prioritization, there are
clear rules and effective methods currently to conduct
reliability and economy assessment. However, there is no
recognized standard or valid approach associate with the
flexibility assessment. The flexibility of planning
schemes indicates their tolerance for uncertain factors,
major of which are listed as follows:
Uncertainty of fault probability of components such
as generator, line and transformer;
Uncertainty of power generation location, capacity,
timing, and availability of new generating facilities;
Uncertainty of future demand, scope and complex-
ity of transaction;
Uncertainty of regulatory constraints and rules.
To handle these uncertainties, McCalley and his asso-
ciates have developed a risk-based method for power
system security assessment [1]. This method considers a
predefined set of contingencies, and takes into account
both probabilities and impacts of these events. The im-
pacts are measured in terms of the voltage or current vi-
olations caused by these predefined contingencies. This
innovative method has been successfully implemented in
numerous fields such as network planning, operational
planning and op eration [2-5].
Based on the risk assessment theory, EPRI, together
with some electric power corporations, has developed a
Probabilistic Risk Assessment (PRA) methodology and
further software to perform risk assessment on power
systems [6]. The PRA program computes the probabilis-
tic risk indices and displays the results clearly with forms
and images. Taking into account both probabilities and
physical impacts of contingencies, planners are able to
have a better understanding of planning schemes, as well
as identify potential failure modes. PRA methodology
and software have been implemented in a number of
electric power corporations, such as Southern Company,
American Electric Power, KCP&L, the Eastern Inter-
connection, NYPA, ERCOT and Tri-State. At present,
PRA method is being introduced into over ten utilities for
their own studies [7-9].
This paper proposes using probabilistic risk assess-
ment method to perform flexibility assessment and quan-
tify system flexibility. Quantitative indices can be used
by system planners to prioritize planning schemes. The
second part of this paper presents PRA methodology.
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