Determining the Effect of Operational Constraints on the Reliability of a Power Distribution Network

Abstract

Electricity-distribution network operators face several operational constraints in the provision of safe and reliable power given that investments for network area reinforcement must be commensurate with improvements in network reliability. This research aimed to ascertain the extent to which distribution reliability is impacted by violating operational constraints – overloading limits. The research study provides an integrated approach for assessing the impact of different operational constraints on distribution-network reliability by incorporating component lifetime models, time-varying component failure rates, and modelling of failure distributions to represent overloading violations in an all-inclusive probabilistic methodology that applies a time-sequential Monte Carlo simulation. A test distribution network based on the Roy Billinton test system with reliability data from the Energy Networks Association database was modelled to evaluate the distribution reliability when time-varying failure rates are used and when overloading limits are exceeded. Standard reliability indices of SAIFI, SAIDI, and ENS measuring the frequency and duration of interruptions and the energy not supplied respectively. The comprehensive assessment includes not only average indices but also their probability distributions to adequately describe the risk of customer interruptions. Results demonstrate the effectiveness of this holistic approach, as the impacts of operational decisions are assessed from both the reliability perspective. There is a consistent increase in all reliability indices when overloading violations are modelled using the linear and non-linear modelling approaches with SAIDI, SAIFI, and ENS increasing by 5.15%, 1.65%, and 5.22% in the former and by 18.54%, 7.34%, and 19.32% in the latter. This provides a holistic view of the effect of violating the operational constraints during network operation on the reliability of a power distribution network. This informs network planning decisions for utilities and regulators in making investments in distribution reliability by assessing the impact of violating operational constraints on distribution reliability.