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Identifying critical components for system reliability in power transmission systems
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (RCAM)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Large interruptions of power supply in the transmission system have considerable impact on modern society. The goal for the transmission system operator (TSO) is to prevent and mitigate such events with optimal decisions in design, planning, operation and maintenance. Identifying critical power components for system reliability provides one important input to this decision-making.

This thesis develops quantitative component reliability importance indices applicable for identifying critical components in real transmission systems. Probabilistic models with component failure statistics are combined with detailed power system models evaluated with the AC power flow technique. In the presented method each system component is assigned three importance indices based on outage events expected probability and consequence to (i) reduced system security margin, (ii) interrupted load supply and (iii) disconnected generation units. By ranking components by each of the three interests, a more complete view of the risks to system reliability can be assessed than if, as traditionally, only (ii) is modelled. The impact on security margin is studied in well established critical transfer sections (CTS) supervised by the TSO. TSOs set the CTSs limits [MW] based on deterministic security criteria, with regard to thermal, voltage level, and system stability limits, and the CTSs' condition at post-contingency state is in the method used as an indicator of the system security margin.

The methodology is extended with three indices modified to quantify the component importance for common-cause events initiated by acts of sabotage.

The developed methods are applied on a significant part of the Great Britain transmission system, modelling 7000 components and 107 substation layouts. The study includes several load demand scenarios, 200 million initiating outage events and non-functioning protection equipment. The resulting component ranking provides an important input to the TSO's decision-making, and could be implemented as a complement to the existing deterministic N-1 criterion. With the methods applied a TSO can perform further and more detailed assessments on a few critical components in order to enhance system reliability for equipment failures and strengthen the system vulnerability against sabotage.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 112 p.
Series
Trita-EE, ISSN 1653-5146 ; 2011:053
Keyword [en]
transmission system reliability, component reliability importance index, Great Britain power system, power flow analysis, system adequacy, system security, system vulnerability
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-40389ISBN: 978-91-7501-081-6 (print)OAI: oai:DiVA.org:kth-40389DiVA: diva2:440986
Public defence
2011-10-07, K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110920Available from: 2011-09-20 Created: 2011-09-14 Last updated: 2012-03-30Bibliographically approved
List of papers
1. Risk analysis for power systems: overview and potential benefits
Open this publication in new window or tab >>Risk analysis for power systems: overview and potential benefits
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2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper provides a mapping and sample of recently developed risk assessment techniques that are available for the distribution system operator. Three estimates on the value of more detailed risk analysis are desccribed. I.e. component reliability importance indices can be used to divversify the maintenance efforts, gaining better expected system performance at no cost. Furthermore, components that are assumed to be relatively harmless (based on average values) are identified as critical for longer interruptions. Finally it is shown that losses in a transformer are critical in the decision on transformer lifetime.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-33499 (URN)
Conference
CIRED Workshop 2010
Note
QC 20110707Available from: 2011-07-07 Created: 2011-05-09 Last updated: 2013-10-07Bibliographically approved
2. RACalc: a Power Distribution Reliability Tool
Open this publication in new window or tab >>RACalc: a Power Distribution Reliability Tool
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2010 (English)In: 2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems (PMAPS): Date:14-17 June 2010, IEEE , 2010, 154-159 p.Conference paper, Published paper (Refereed)
Abstract [en]

One major objective of maintenance management activities in electrical distribution systems is to find the right level of investments. Within an MSc thesis project at KTH, the probabilistic reliability software RACalc has been developed to support the decision making in the distribution system maintenance planning and risk analysis. This paper desccribes the algorithms in RACalc and shows on present status on RADPOW, an additional reliability tool developed within the research group. Calculations with RACalc is in this paper exemplified with a case study on an existing Swedish distribution system, were the program is used to determine the components’ importance to the system reliability indices. The result show that if the failure rate can be decreased by 10% on the 21% most important components, the overall system reliability improvement is more than 7%.

Place, publisher, year, edition, pages
IEEE, 2010
Keyword
GUI, RACalc, RADPOW, RCAM, Reliability analysis, component, electrical distribution systems, risk management
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-33500 (URN)10.1109/PMAPS.2010.5528991 (DOI)2-s2.0-77956440161 (Scopus ID)
Conference
Proceedings IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS)
Note
© 2010 IEEE. Personal use of the attached pdf is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20110708Available from: 2011-07-08 Created: 2011-05-09 Last updated: 2011-10-25Bibliographically approved
3. Components' Impact on Critical Transfer Section for Risk Based Transmission System Planning
Open this publication in new window or tab >>Components' Impact on Critical Transfer Section for Risk Based Transmission System Planning
2009 (English)In: 2009 IEEE Bucharest PowerTech: Innovative Ideas Toward the Electrical Grid of the Future / [ed] Toma L; Otomega B, IEEE , 2009, 368-375 p.Conference paper, Published paper (Refereed)
Abstract [en]

In the planning of the electrical transmission system it is of greatest concern to quantify the security margin for unwanted conditions in the system. This paper proposes an approach based on quantifying the risk of insufficient transmission capacity in bottlenecks in the system. Stresses in these critical transfer sections (CTS) provide a potential risk to corrective actions, or worst, load curtailments. The proposed method provides a general screening of component outages in order to find potential risk events for the CTS. Furthermore, the severity of each risk event is quantified based on the likelihood of the event and the consequence on the section's transmission capacity. The components' contribution to the risk of insufficient capacity in the CTS is then based on these risk events' severity. The method investigates several forecasted load levels during the year and consequently gives an input to a scheme for a risk based transmission system planning. The method is demonstrated on the reliability test system RBTS.

Place, publisher, year, edition, pages
IEEE, 2009
Keyword
Power transmission reliability, power system security, reliability modeling, risk analysis, power system planning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-25819 (URN)000276834600057 ()2-s2.0-74949123727 (Scopus ID)978-1-4244-2234-0 (ISBN)
Conference
2009 IEEE Bucharest PowerTech: Innovative Ideas Toward the Electrical Grid of the Future; Bucharest; Romania; 28 June 2009 through 2 July 2009
Note

QC 20101101

Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2014-10-09Bibliographically approved
4. Identifying Critical Components for Transmission System Reliability
Open this publication in new window or tab >>Identifying Critical Components for Transmission System Reliability
2012 (English)In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 27, no 4, 2106-2115 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a method to quantify and rank transmission system components by their importance for system reliability under different load scenarios. Each component is ranked by three separate importance indexes based on its expected outage rate and impact on: 1) system security margin; 2) load supply; and 3) generation units. By studying these three interests individually, a more complete view of the risks to system reliability can be assessed. The method is demonstrated on a detailed power system model (7000 components) of a significant part of the Great Britain transmission system at 400 and 275 kV. The results show how sensitive the component indexes are to the load scenario. The method provides an input for decision-making when planning maintenance and new investment and can be used as a complement to deterministic criteria.

Place, publisher, year, edition, pages
IEEE Press, 2012
Keyword
Component reliability importance, Great Britain power system, power flow analysis, system adequacy, system security, transmission system reliability
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-40287 (URN)10.1109/TPWRS.2012.2188144 (DOI)000310389000040 ()2-s2.0-84867997220 (Scopus ID)
Note

QC 20121127

Available from: 2012-11-27 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved
5. Component ranking in Great Britain transmission system based on either equipment failures or sabotage
Open this publication in new window or tab >>Component ranking in Great Britain transmission system based on either equipment failures or sabotage
2012 (English)In: Journal of Risk and Reliability, ISSN 1748-006X, E-ISSN 1748-0078, Vol. 226, no 1 (SI), 96-108 p.Article in journal (Refereed) Published
Abstract [en]

In the long-term and operational planning of the power transmission system (PTS), one challenge is to identify components critical to system reliability. In this paper, the importance of each component for system reliability and vulnerability are quantified for two scenarios in a model of the Great Britain (GB) PTS. The scenarios are: (1) technical failures based on statistical data and (2) sabotage where the attacker has the ability to immobilize two contiguous components. In a novel method approach, the total importance of each component is based on three separate indices that include the system impact on (i) security margin, (ii) load, and (iii) generation. The final result of the GB system screening, including nearly 7000 components and 50 million outage events, is a ranking list indicating the 30 most critical components for each of the two scenarios. The results show that a component ranking that only includes risks of technical failures cannot be used to describe critical sabotage threats. Based on the results, the system operator can perform further and more detailed analysis on a few components and then make the necessary investments to improve the system reliability for equipment failures and strengthen the system vulnerability against sabotage.

Place, publisher, year, edition, pages
Sage Publications, 2012
Keyword
component importance indices; transmission system reliability; system vulnerability; system security; power flow analysis; Great Britain power system
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-40388 (URN)10.1177/1748006X11427372 (DOI)000300053300010 ()2-s2.0-84864481895 (Scopus ID)
Funder
StandUp
Note

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART O. QC 20120305

Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved

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