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Publications (10 of 23) Show all publications
Morozovska, K., Naim, W., Viafora, N., Shayesteh, E. & Hilber, P. (2020). A framework for application of dynamic line rating to aluminum conductor steel reinforced cables based on mechanical strength and durability. International Journal of Electrical Power & Energy Systems, 116, Article ID 105491.
Open this publication in new window or tab >>A framework for application of dynamic line rating to aluminum conductor steel reinforced cables based on mechanical strength and durability
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2020 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 116, article id 105491Article in journal (Refereed) Published
Abstract [en]

Dynamic line rating can be described as a method of overloading the power line within reliability and safety limits. Power line's loading limits can be increased, if its temperature is controlled to be below the maximum allowable conductor temperature, which is defined by the grid regulations. Dynamic rating brings additional uncertainties and risks to the grid operation due to high variability of weather conditions, which plays an essential role in determining real-time capacity limits. Power lines often are under the influence of risk factors related to power system performance, however, they could also be subjected to additional risks related to their mechanical structure. Overhead lines, which are composed of more than one stranded material, are exposed to increasing mechanical stress due to differences in thermal expansion characteristics of different materials. The reliability analysis of transient expansion/shrinkage of the material has identified the risks to the conductor mechanical strength that are associated with dynamic heating and cooling. This study determines an optimal dynamic line rating application, which not only would take into account electrical properties of the system and economic benefits, but would also minimize the aging of steel reinforced aluminum overhead lines. Alternatively to hourly line rating adjustment, 2 h, 3 h and 4 h ratings are suggested as possible way to decrease impact of DLR on conductor mechanical durability. Comparing the mechanical durability and cost benefits between different frequencies of loading limit adjustments, allows suggesting improvements to dynamic line rating application. 

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Aluminum conductor steel reinforced, Conductor mechanical strength, Dynamic line rating, Power line durability, Durability, Electric power system control, Overhead lines, Reinforcement, Reliability analysis, Risk assessment, Thermal expansion, Dynamic line ratings, Maximum allowable conductor temperature, Mechanical durability, Power lines, Power system performance, Reliability and safeties, Thermal expansion characteristics, Dynamics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-262058 (URN)10.1016/j.ijepes.2019.105491 (DOI)000499733200009 ()2-s2.0-85072543859 (Scopus ID)
Note

QC 20191122

Available from: 2019-11-22 Created: 2019-11-22 Last updated: 2020-01-13Bibliographically approved
Viafora, N., Morozovska, K., Kazmi, S. H., Laneryd, T., Hilber, P. & Holbøll, J. (2019). Day-ahead dispatch optimization with dynamic thermal rating of transformers and overhead lines. Electric power systems research, 171, 194-208
Open this publication in new window or tab >>Day-ahead dispatch optimization with dynamic thermal rating of transformers and overhead lines
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2019 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 171, p. 194-208Article in journal (Refereed) Published
Abstract [en]

Several studies have demonstrated how Dynamic Line Rating (DLR) could be an effective solution for increasing transmission capacity of existing overhead lines. As opposed to Static Line Ratings (SLR), DLR allows for higher power flows depending on real time thermal state of conductors, which highly depend on actual weather conditions. Similarly, recent advances in transformer thermal modelling revealed the feasibility of Dynamic Transformer Rating (DTR) based on the temporal evolution of top oil and winding hot spot temperatures. However, the joint dynamic thermal rating of both overhead lines and transformers in transmission networks has not been thoroughly addressed yet in the literature. This paper proposes a day-ahead dispatch optimization problem based on DC-Optimal Power Flow, where transformer top oil and hot spot dynamics are directly accounted for together with dynamic line ratings of selected transmission lines. Simulated weather data from an actual power system are mapped to the IEEE RTS 24 bus system thus allowing for the estimation of DLR on several lines and the influence of ambient temperature on transformer rating. Results indicate the potential benefits that using DLR in conjunction with DTR could provide for the optimal power system dispatch. The proposed approach does not only indicate advantages compared to standard rating scenarios, but also shows a positive impact that dynamic line rating has on unlocking transformer constraints and vice versa.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Dynamic line rating, Dynamic transformer rating, Optimal power dispatch, Power system optimization, Wind power integration
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-246409 (URN)10.1016/j.epsr.2019.02.026 (DOI)000464488600019 ()2-s2.0-85062302260 (Scopus ID)
Note

QC 20190402

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2020-01-09Bibliographically approved
Naim, W., Morozovska, K. & Hilber, P. (2019). Effects of Dynamic Line Rating on the Durability and Mechanical Strength of Aluminum Cable Steel Reinforced (ACSR) Conductors. In: Innovative Solutions for Energy Transitions: . Paper presented at 10th International Conference on Applied Energy, ICAE 2018; Hong Kong; China; 22 August 2018 through 25 August 2018 (pp. 3164-3169). Elsevier, 158
Open this publication in new window or tab >>Effects of Dynamic Line Rating on the Durability and Mechanical Strength of Aluminum Cable Steel Reinforced (ACSR) Conductors
2019 (English)In: Innovative Solutions for Energy Transitions, Elsevier, 2019, Vol. 158, p. 3164-3169Conference paper, Published paper (Refereed)
Abstract [en]

Dynamic Line Rating (DLR) is an emerging technology, which provides better utilization of power lines, by using real-time information on the weather parameters to dynamically adjust line rating limits. The power line capacity is highly dependent on its heat balance. The heat balance is influenced by external factors such as wind speed, ambient temperature, humidity, solar radiation and load. DLR analyses have shown high economical and reliability benefits from power system perspective. However, the mechanical stress on the conductor due to differences in thermal expansion characteristics of Aluminum and Steel materials could lead to faster ageing and mechanical damages. The study aims to provide better understanding of the risks associated with DLR application, which can affect conductor's mechanical lifetime. The reliability analysis of transient expansion and shrinkage of the material has identified the risks to the conductor mechanical strength that are associated with dynamic heating and cooling.

Place, publisher, year, edition, pages
Elsevier, 2019
Series
Energy Procedia, ISSN 1876-6102 ; 158
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-239530 (URN)10.1016/j.egypro.2019.01.1019 (DOI)000471031703082 ()2-s2.0-85063912210 (Scopus ID)
Conference
10th International Conference on Applied Energy, ICAE 2018; Hong Kong; China; 22 August 2018 through 25 August 2018
Projects
Dynamic rating with applications to renewable energy
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, FPS18StandUp for WindSwedish Energy Agency
Note

QC 20181126

Available from: 2018-11-23 Created: 2018-11-23 Last updated: 2020-01-09Bibliographically approved
Jürgensen, J. H., Nordström, L. & Hilber, P. (2019). Estimation of Individual Failure Rates for Power System Components Based on Risk Functions. IEEE Transactions on Power Delivery, 34(4), 1599-1607
Open this publication in new window or tab >>Estimation of Individual Failure Rates for Power System Components Based on Risk Functions
2019 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 34, no 4, p. 1599-1607Article in journal (Refereed) Published
Abstract [en]

The failure rate is essential in power system reliability assessment and thus far, it has been commonly assumed as constant. This is a basic approach that delivers reasonable results. However, this approach neglects the heterogeneity in component populations, which has a negative impact on the accuracy of the failure rate. This paper proposes a method based on risk functions, which describes the risk behavior of condition measurements over time, to compute individual failure rates within populations. The method is applied to a population of 12 power transformers on transmission level. The computed individual failure rates depict the impact of maintenance and that power transformers with long operation times have a higher failure rate. Moreover, this paper presents a procedure based on the proposed approach to forecast failure rates. Finally, the individual failure rates are calculated over a specified prediction horizon and depicted with a 95% confidence interval.

Keywords
failure analysis; maintenance engineering; power system reliability; power transformers; reliability theory; higher failure rate; power system components; risk functions; power system reliability assessment;power transformers;individual failure rates estimation;transmission level;Sociology;Statistics;Maintenance engineering;Power transformers;Reliability;Power system reliability;Asset management; condition monitoring; failure rate; failure rate modeling; power transformer diagnostics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-255877 (URN)10.1109/TPWRD.2019.2913777 (DOI)000477724800042 ()2-s2.0-85069930869 (Scopus ID)
Note

QC 20190820

Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-12-10Bibliographically approved
Zarei, T., Morozovska, K., Laneryd, T., Hilber, P., Wihlen, M. & Olle, H. (2019). Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration. International Journal of Electrical Power & Energy Systems, 106, 598-606
Open this publication in new window or tab >>Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration
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2019 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 106, p. 598-606Article in journal (Refereed) Published
Abstract [en]

An increasing share of renewable energy on the electricity market creates the need for economic and efficient production, operation and integration technologies, associated with the specific behavior of renewable energy sources (RES). Dynamic rating (DR) provides a possibility to apply improvements to the system both during planning and operation stages. The DR benefits are well described in various literature sources. However, DR is often focused on more efficient exploitation of power lines, not power transformers. Power transformers are costly equipment and their efficient usage and planning can have drastic effect on total costs.

Our analysis focuses on the dynamic transformer rating (DTR) for wind energy applications. The main objective is to study reliability effects of DTR from the component perspective. We utilize existing knowledge about transformer heat balance models from IEC and IEEE standards to obtain information on the loss of life (LOL) of the transformer under investigation and propose possible improvements for the system in question. The method can be employed for identifying the appropriate transformer size by taking into account ambient temperature and load variations and then overloading the transformer beyond nameplate ratings. The reliability of the proposed application is ensured by calculating the risk of overloading the transformer for each day of the year. A risk of overloading is quantified as LOL of the transformer. The risk is presented as a function of ambient temperature and duration of an overload. The final step consists of an economic analysis, which demonstrates economic benefits of DTR application.

Keywords
Dynamic transformer rating, Loss of life, Heat balance, Wind energy
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-239531 (URN)10.1016/j.ijepes.2018.09.038 (DOI)000454377000055 ()2-s2.0-85056630521 (Scopus ID)
Projects
Dynamic rating with applications to renewable energy
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, FPS18Swedish Energy AgencyStandUp for Wind
Note

QC 20181130

Available from: 2018-11-23 Created: 2018-11-23 Last updated: 2020-01-09Bibliographically approved
Mashad Nemati, H., Pinheiro Sant'Anna, A., Nowaczyk, S., Jürgensen, J. H. & Hilber, P. (2019). Reliability Evaluation of Power Cables Considering the Restoration Characteristic. International Journal of Electrical Power & Energy Systems, 105, 622-631
Open this publication in new window or tab >>Reliability Evaluation of Power Cables Considering the Restoration Characteristic
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2019 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 105, p. 622-631Article in journal (Refereed) Published
Abstract [en]

In this paper Weibull parametric proportional hazard model (PHM) is used to estimate the failure rate of every individual cable based on its age and a set of explanatory factors. The required information for the proposed method is obtained by exploiting available historical cable inventory and failure data. This data-driven method does not require any additional measurements on the cables, and allows the cables to be ranked for maintenance prioritization and repair actions.

Furthermore, the results of reliability analysis of power cables are compared when the cables are considered as repairable or non-repairable components. The paper demonstrates that the methods which estimate the time-to-the-first failure (for non-repairable components) lead to incorrect conclusions about reliability of repairable power cables.

The proposed method is used to evaluate the failure rate of each individual Paper Insulated Lead Cover (PILC) underground cables in a distribution grid in the south of Sweden.

Place, publisher, year, edition, pages
London: Elsevier, 2019
Keywords
Power cable, historical data, reliability, proportional hazard model, preventive maintenance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-238643 (URN)10.1016/j.ijepes.2018.08.047 (DOI)000449447200055 ()2-s2.0-85053080255 (Scopus ID)
Note

QC 20181109

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2019-06-11Bibliographically approved
Duvnjak Zarkovic, S., Stankovic, S., Shayesteh, E. & Hilber, P. (2019). Reliability improvement of distribution system through distribution system planning: MILP vs. GA. In: 2019 IEEE Milan PowerTech: . Paper presented at 2019 IEEE Milan PowerTech.
Open this publication in new window or tab >>Reliability improvement of distribution system through distribution system planning: MILP vs. GA
2019 (English)In: 2019 IEEE Milan PowerTech, 2019Conference paper, Published paper (Refereed)
Abstract [en]

Distribution system planning (DSP) is very important because it can result in reliability enhancement and large cost savings for both utilities and consumers. DSP is a complex nonlinear problem, which can be solved with different optimization methods. This paper compares two such optimization methods, conventional (mixed-integer linear programming - MILP) and meta-heuristic (genetic algorithm - GA), applied to the DSP problem: construction of feeders in distribution power system from scratch. The main objective of DSP is to minimize the total cost, where both the investment and operational outage costs are considered, while the reliability of the whole system is maximized. DSP problem is applied to an actual distribution system. Solution methods are outlined, and computational results show that even though GA gives reasonably good results in faster computation time, MILP provides a better optimal solution with simpler implementation.

Keywords
Distribution system, distribution system planning, edge-sets, genetic algorithm, mixed-integer programming, power system reliability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-259601 (URN)10.1109/PTC.2019.8810515 (DOI)2-s2.0-85072341947 (Scopus ID)
Conference
2019 IEEE Milan PowerTech
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, CP26
Note

QC 20190930

Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2019-09-30Bibliographically approved
Jürgensen, J. H., Brodersson, A. L., Nordström, L. & Hilber, P. (2018). Impact Assessment of Remote Control and Preventive Maintenance on the Failure Rate of a Disconnector Population. IEEE Transactions on Power Delivery, 33(4), 1501-1509
Open this publication in new window or tab >>Impact Assessment of Remote Control and Preventive Maintenance on the Failure Rate of a Disconnector Population
2018 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 33, no 4, p. 1501-1509Article in journal (Refereed) Published
Abstract [en]

This paper presents the impact of different explanatory variables such as remote control availability and conducted preventive maintenance, among others, on failure statistics of a disconnector population in Sweden using the proportional hazard model. To do so, 2191 work orders were analysed which included 1626 disconnectors and 278 major failures. Here, the results show that the remote control availability for disconnectors - an example of such Smart Grid technology - has a negative effect on the failure rate, whereas preventive maintenance has a positive impact. It is also shown that the disconnector age is not significant and that certain disconnector types have a significant and positive correlation towards failures when compared to other disconnector types. The results increase the understanding of disconnector failures to improve asset management.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Asset management, control equipment reliability, monitoring, diagnostic measures, failure rate, failure rate estimation, preventive maintenance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-216785 (URN)10.1109/TPWRD.2017.2710482 (DOI)000431959600001 ()2-s2.0-85046947535 (Scopus ID)
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Note

QC 20171102

Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2018-09-27Bibliographically approved
Song, M., Amelin, M., Shayesteh, E. & Hilber, P. (2018). Impacts of flexible demand on the reliability of power systems. In: : . Paper presented at 2018 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT).
Open this publication in new window or tab >>Impacts of flexible demand on the reliability of power systems
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Demand response provides flexibility to power systems through adjusting the power consumption. This study investigates the impact of flexible demands on the system reliability with real-time price-based demand response. It assumes that the power demand is sensitive to nodal price and the price is communicated to consumers as soon as it is cleared on market. The uncertainties of nodal price and potential flexibility are considered. Models are proposed for the optimal operation of a power system with and without demand response, respectively. The proposed models are evaluated through application to a 6-bus system using Monte Carlo simulation. The result shows that the reliability indices LOLP and EENS are improved for the system and for each bus when the demand is sensitive to nodal price. Moreover, the nodal prices decrease, reflecting a more efficient operation and a lower electricity price charged on consumers.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-250468 (URN)10.1109/ISGT.2018.8403357 (DOI)2-s2.0-85050701617 (Scopus ID)
Conference
2018 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT)
Note

QC 20190520

Available from: 2019-04-30 Created: 2019-04-30 Last updated: 2019-10-09Bibliographically approved
Shayesteh, E., Yu, J. & Hilber, P. (2018). Maintenance optimization of power systems with renewable energy sources integrated. Energy, 149, 577-586
Open this publication in new window or tab >>Maintenance optimization of power systems with renewable energy sources integrated
2018 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 149, p. 577-586Article in journal (Refereed) Published
Abstract [en]

This paper proposes a quantitative maintenance optimization problem for developing reliability centred maintenance for a power system with renewable energy sources. Reliability and cost are two important interlinked aspects considered by system operators in many deregulated power systems. Reliability centred maintenance is an effective method to consider both of these aspects when performing the maintenance optimization. Nevertheless, this method has not adequately studied for a power system with renewable energy sources included. According to the maintenance optimization problem proposed in this paper, first, the most critical components of the system are selected. Then, a set of maintenance strategies are proposed for all critical components. After that, the total cost of each maintenance strategy for all critical components are calculated as the summation of operation, maintenance, environmental, and interruption costs. Finally, the best maintenance strategy for each critical component is selected by identifying the lowest total cost of different maintenance strategies. The proposed method is tested on IEEE 14-bus system. The results show that the proposed maintenance optimization method provides a useful way for deciding the most proper maintenance strategies for the studied system.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Environmental cost calculation, Power system maintenance optimization, Reliability centred maintenance (RCM), Renewable energy sources (RES), Severity risk index (SRI)
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-227614 (URN)10.1016/j.energy.2018.02.066 (DOI)000431162100046 ()2-s2.0-85042388092 (Scopus ID)
Note

QC 20180515

Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-21Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2964-7233

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