Enhancing the Seismic Resilience of Aerial Substations: A Case Study of a Mid-Line Two-Pole 315 kVA Transformer

Document Type : Research Article

Author

Department of Civil Engineering, Razi University, Kermanshah, Iran

Abstract

Experience from past earthquakes has shown that transformers installed on aerial utility poles are among the most vulnerable components in power distribution networks. Significant vibrations and rotations of transformers during seismic events can damage transformer accessories such as bushings, and compromise the connections of their mounting platforms, potentially leading to sliding or overturning of the transformer. In most existing aerial substations in Iran, one or both ends of the transformer platform are connected to the reinforced concrete poles using friction-based joints instead of standard bolted connections. This paper investigates the underlying reasons for the widespread use of frictional connections in conventional pole-mounted substations and evaluates the seismic behavior of a 315 kVA two-pole transformer installation located at mid-span of a distribution line. The main contribution of this study lies in diagnosing prevalent technical flaws in standard aerial substation connections nationwide and introducing a novel seismic retrofit strategy. The proposed retrofit method is founded on two key principles: simplicity and technical refinement. Simplicity ensures the solution avoids execution complexity and costly equipment, while technical refinement guarantees a coherent, well-balanced design with no mismatches or inconsistencies. Nonlinear time history analyses reveal that the seismic performance of the frictional platform-to-pole connections is inadequate, rendering the substation vulnerable under design-level earthquake scenarios. Subsequently, retrofit solutions are proposed to improve the resilience of the transformer platform connections. The seismic response of the retrofitted substation is then compared to its original, unstrengthen state. The proposed retrofit measures significantly enhance the performance level of the aerial substation by limiting transformer rotation to below 0.015 radians, thereby improving transformer stability under design-level seismic events.

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References

[1] Jafari, M.A., Rahnavard, A., Zekavati, A.A. (2011). Vulnerability of Aerial Transformers in Earthquakes and Their Retrofit Solutions, 26th International Power System Conference, Tehran, Iran (In Persian).
[2] Schiff, A. J., & Schiff, A. (1998). Guide to improved earthquake performance of electric power systems. Gaithersburg, MD, USA: US Department of Commerce, National Institute of Standards and Technology.
[3] Zekavati A., Jafari. M.A., and Rahnavard A. (2015). Performance assessment of power distribution network in 2013 Bushehr, Iran Earthquake, in 7th International Conference on Seismology & Earthquake Engineering (IIEES), Tehran, Iran.
[4] Preliminary Report on the Identification of the Bam Earthquake of December 26, 2003. International Institute of Earthquake Engineering and Seismology (2003), Tehran, Iran (In Persian).
[5] Preliminary Report on the Earthquake of November 12, 2017, Sarpol-e Zahab, Kermanshah Province with a Moment Magnitude of 7.3. International Institute of Earthquake Engineering and Seismology (2017), Tehran, Iran (In Persian).
[6] Oboudi, M. H., & Mohammadi, M. (2024). Two-stage seismic resilience enhancement of electrical distribution systems. Reliability Engineering & System Safety, 241, 109635.
[7] Liu, J., Meng, X., Tian, L., Jin, Q., Dong, Y., Yang, M., & Liu, K. (2024). Failure mechanisms and seismic fragility analysis of overhead transmission lines incorporating pile-soil-structure interaction. Engineering Failure Analysis, 160, 108201.
[8] Mahmoudi M., Ghasemi A., and Tavousi Tafreshi S. (2023). Evaluation of the seismic performance of isolated electrical transformers under pulse-like excitations, Amirkabir Journal of Civil Engineering, 54 (10), p. 4007-4034.
[9] Liu, X., Xie, Q., Liang, H., & Zhu, W. (2023). Seismic resilience evaluation and retrofitting strategy for substation system. International Journal of Electrical Power & Energy Systems, 153, 109359.
[10] Zeynalian M. and Zamani M. (2018). Structural behaviour of concrete poles used in electric's power distribution network, Journal of Structural and Construction Engineering, 4(4), p. 29-41.
[11] Motaei Y., and Akashe B. (2015). Earthquake hazard in Tehran and the study of failure moods of power distribution equipment during earthquake, Journal of New Research in Seismology, JNRS, 10(35), p. 5-8 (In Persian).
[12] Publication 375 -  Management and Planning Organization of Iran (2007), Tehran, Iran (In Persian).
[13] Standard for Aerial Distribution Lines - Cross Arms and Pole Arrangements Used in the Distribution Network. Ministry of Energy - Tavanir Company - Research and Technology Deputy - Standards Office - Volume 6 (1998), Tehran, Iran (In Persian).
[14] Guidelines for Determining Requirements, Technical Evaluation Criteria, and Tests for Reinforced Concrete Square Poles. Tavanir Company, Distribution Coordination Deputy, Technical and Engineering Distribution Office, Concrete Poles Specialized Committee, 3rd Edition (2017), Tehran, Iran (In Persian).
[15] Standard for Aerial Distribution Lines (Standard 51-1), Design Principles and Practical Tables. Ministry of Energy - Tavanir Company - Research and Technology Deputy - Standards Office - Volume 1 (1999), Tehran, Iran (In Persian).
[16] Building Design Code for Earthquake Resistance (Standard 2800) - 4th Edition. Road, Housing, and Urban Development Research Center (2014), Tehran, Iran (In Persian).
[17] Rabbat, B. and Russell, H. (1985). Friction coefficient of steel on concrete or grout. Journal of Structural Engineering, 111(3): p. 505-515.
[18] Guidelines for Seismic Evaluation of Substation Facilities, Publication 315. Deputy of Planning and Strategic Supervision of the President - Strategic Supervision Deputy - Technical Executive System Office (2009), Tehran, Iran (In Persian).
[19] Guidelines for Seismic Evaluation and Retrofit of Power Supply Systems, Publication No. 607, 2012, Vice Presidency for Planning and Strategic Supervision – Strategic Supervision Deputy – Technical Affairs System (In Persian).
[20] Toopchi-Nezhad, H. (2021). Study, Review, and Determination of Methods for Retrofitting Structures of Aerial Substations, Ground Substations, and Electrical Equipment Against Natural Disasters, Research Project Report No. 765/D/98, Kermanshah Province Electricity Distribution Company, Research Deputy of Razi University (In Persian).
Amirkabir Journal of Civil Engineering
Volume 57, Issue 4
2025
Pages 695-714

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