Outage data analysis and RAMS evaluation of the Italian overhead transmission lines

Abstract

A serious failure of a power transmission line can generate substantial financial losses due to the power outage. Consequently, utilities have a clear incentive to assess the actual condition of strategically important transmission lines, with the aim to minimize the risk of failures, enhance the maintenance practices and plan the development of the transmission network. This work focuses on the analysis of forced outages data for high-voltage overhead transmission lines (OHTL) in the Italian network during the period from 2008 to 2014. After a brief survey of the Italian network, the analysis has been carried out as follows: after a preliminary identification of the outage causes for OHTL, a new factor, namely the Severity Factor, has been introduced with the aim to drive the prioritization of the failure causes and the enhancement of the maintenance activities. Finally, an evaluation of the reliability, availability, safety and maintainability (RAMS) of the Italian OHTL network has been performe

Outage severity analysis and RAM evaluation of italian overhead transmission lines from a regional perspective

“…At the same time, however, from a study conducted by the same authors of this paper in [8]- [9], it results that OHTLs are still the most critical components from both number of failures and the corresponding interrupted power points of view. The analysis presented in [8]- [9] were based on the data published by TERNA, the Italian TSO, about the outages of the Italian OHTLs in the period from 2008 to 2014.…”

“…The Severity Factor has been introduced by the authors in [8]- [9], defining it as an index that enables a rapid and effective comparison of the impact of different outage causes for OHTLs at the same voltage level. In particular, the symbol SF i,j denoted the Severity Factor of a generic outage category i for the OHTLs of the voltage category j.…”

“…In the following, for the sake of the clearness, with the notation SF i , j , the authors will always refer to the severity of the failures related to category i and affecting the OHTL belonging to the macrocategory j. In this paper, the SF is defined with a different analytical expression with respect to [8], where it was defined in an analogous way with respect to the Risk Priority Number (RPN) adopted in the Failure Mode, Effects and Criticality Analysis (FMECA) [15]. In particular, it will be adopted the definition of severity factor SF related to a category i and macrocategory j introduced in [9] and reported in (4) as:…”

“…This makes the comparison of the SFs for the different categories more fair, since it is reasonable to expect that statistically the number of outage events recorded for a given category i is proportional to the length of the related lines, so that E i,j tends to increase with the length. The new formulation of the SF given in (4) leads to different improvements with respect to the definition provided in [8]. The generic SF i,j , indeed, has now a physical meaning since it represents a weighted percentage of not-transmitted energy associated to a category i, for a macrocategory j.…”

“…Further, a longer period is surveyed, from 2008 to 2015, during which 12594 outages were registered, with a total power interrupted of 81379 MW. The tools exploited for the outage analysis are the Severity Factor (SF), already introduced by the the same authors in [8]- [9], and the Reliability, Availability, Maintainability (RAM) Analysis.…”