The temperature gradient and mismatching between the thermal expansion of the core and flange readily lead to cracks and discharges on the core surface of the dry-type valve-side bushing, which severely impact the safety of power systems. It is vital to clarify the cracking risk of bushing cores under temperature gradients and establish corresponding control methods. The mechanical properties of epoxy resin impregnated paper (ERIP) material were measured in this study at different temperatures, and a thermal–mechanical coupling simulation model was established. The thermal and stress distributions of the core were obtained and the cracking risk was defined accordingly. The crack development mode was explored as it relates to the phase-field mode. Various elastic cushion materials affecting the stress distribution of the core were investigated. The results show that the mechanical properties of the ERIP material decrease rapidly as the temperature increases. When under severe working conditions, the maximum first principal stress of the core may be significantly higher than the tensile strength of the ERIP material resulting in significant axial cracks. Adding an elastic cushion layer made of polyurethane rubber can effectively relax the interface stress and reduce the cracking risk.

References

1. 1)
  - 27. Sreenivasan, P., Kurian, P., ‘Mechanical properties and morphology of nitrile rubber toughened polystyrene’, Int. J. Polym. Mater., 2007, 56, (11), pp. 1041–1050.
2. 2)
  - 20. Wang, Q., Yang, X., Peng, Z., et al: ‘3D coupled electromagnetic-thermal-fluid method for computation of temperature field of converter transformer RIP bushings’, Proc. Chin. Soc. Electr. Eng., 2016, 36, (22), pp. 6269–6275.
3. 3)
  - 23. Zhou, S., Zhuang, X., Zhu, H.: ‘Phase field modelling of crack propagation, branching and coalescence in rocks’, Theor. Appl. Fract. Mech., 2018, 96, pp. 174–192.
4. 4)
  - 17. Liu, S., Chevali, V., Xu, Z., et al: ‘A review of extending performance of epoxy resins using carbon nanomaterials’, Compos. B, Eng., 2018, 136, pp. 197–214.
5. 5)
  - 24. Zhong, A.: ‘Challenges for high-pressure high-temperature applications of rubber materials in the oil and gas industry. Residual stress’, Thermomech. Infrared Imaging Hybrid Tech. Inverse Probl., 2016, 9, pp. 65–79.
6. 6)
  - 4. Tian, H., Liu, P., Zhou, S., et al: ‘Research on the deterioration process of electrical contact structure inside the ±500 kV converter transformer RIP bushings and its prediction strategy’, IET Gener. Transm. Distrib., 2019, 13, (12), pp. 2391–2400.
7. 7)
  - 11. Seyedmehdi, S., Ebrahimi, M.: ‘Super-hydrophobic modified-polyurethane coatings for bushing of power transformers: from material to fabrication, mechanical and electrical properties’, Prog. Org. Coat., 2018, 123, pp. 134–137.
8. 8)
  - 8. Kurimoto, M., Ozaki, H., Sawada, T., et al: ‘Filling ratio control of TiO2 and SiO2 in epoxy composites for permittivity-graded insulator with low coefficient of thermal expansion’, IEEE Trans. Dielectr. Electr. Insul., 2018, 25, (3), pp. 1112–1120.
9. 9)
  - 7. Chen, M., Liu, X., Wu, Z., et al: ‘Novel heat pipe current-carrying tube of RIP valve-side bushing in converter transformer’, Electr. Power Syst. Res., 2020, 184, p. 106344.
10. 10)
  - 1. Liu, Z., Zhang, F., Yu, J., et al: ‘Research on key technologies in ±1100 kV ultra-high voltage DC transmission’, High Volt., 2018, 3, (4), pp. 279–288.
11. 11)
  - 10. Zhang, W., Li, H., Gao, L., et al: ‘Molecular simulation and experimental analysis on thermal and mechanical properties of carbon nanotube/epoxy resin composites with different curing agents at high-low temperature’, Polym. Compos., 2018, 39, (S2), pp. 945–954.
12. 12)
  - 14. Guo, L., Zhang, Z., Li, M., et al: ‘Extremely high thermal conductivity of carbon fiber/epoxy with synergistic effect of MXenes by freeze-drying’, Compos. Commun., 2020, 19, pp. 134–141.
13. 13)
  - 25. Chaikumpollert, O., Yamamoto, Y., Suchiva, K., et al: ‘Protein-free natural rubber’, Colloid Polym. Sci., 2012, 290, (4), pp. 331–338.
14. 14)
  - 13. Hadipeykani, M., Aghadavoudi, F., Toghraie, D.: ‘A molecular dynamics simulation of the glass transition temperature and volumetric thermal expansion coefficient of thermoset polymer based epoxy nanocomposite reinforced by CNT: a statistical study’, Phys. A, Stat. Mech. Appl., 2020, 546, p. 123995.
15. 15)
  - 16. Pahl, W.: ‘Carrier substrate for stress sensitive device and method of manufacture’. U.S. Patent Application, accessed 12 February 2020.
16. 16)
  - 3. Zhang, S., Peng, Z., Liu, P.: ‘Inner insulation structure optimization of UHV RIP oil-SF6 bushing using electro-thermal simulation and advanced equal margin design method’, IEEE Trans. Dielectr. Electr. Insul., 2014, 21, (4), pp. 1768–1777.
17. 17)
  - 26. Mancke, R., Landel, R.: ‘Stress–strain behavior of a polyurethane rubber in combined torsion and tension or compression’, J. Polym. Sci., Polym. Phys. Ed., 1972, 10, (10), pp. 2041–2049.
18. 18)
  - 22. Wang, Q., Yang, X., Tian, H., et al: ‘A novel dissipating heat structure of converter transformer RIP bushings based on 3-D electromagnetic-fluid-thermal analysis’, IEEE Trans. Dielectr. Electr. Insul., 2017, 24, (3), pp. 1938–1946.
19. 19)
  - 5. Kim, S., Park, D., Jeon, U.: ‘Response of a 230 kV outdoor termination according to the frequency characteristics of input seismic waves’, Energy Rep., 2020, 6, pp. 497–503.
20. 20)
  - 18. Shen, Y., Wang, H.: ‘Optimization design on CFG-Pile foundation with different cushion thickness in Beijing-Shanghai high-speed railway’, Transp. Infrastruct. Geotechnol., 2015, 3, (1), pp. 3–20.
21. 21)
  - 9. Hawileh, R., Abdalla, J., Hasan, S., et al: ‘Models for predicting elastic modulus and tensile strength of carbon, basalt and hybrid carbon-basalt FRP laminates at elevated temperatures’, Constr. Build. Mater., 2016, 114, pp. 364–373.
22. 22)
  - 2. Liu, X., Chen, M., Liang, C., et al: ‘Investigation on distribution of electro-thermal coupled field and improved design of ±1100 kV converter valve-side bushing’, IET Sci. Meas. Technol., 2020, 14, (2), pp. 188–197.
23. 23)
  - 12. Mateev, V., Ivanov, G., Marinova, I.: ‘Seismic analysis of high voltage bushing’. 20th Int. Conf. Symp. on Electrical Apparatus and Technologies, Bourgas, 2018, pp. 1–4.
24. 24)
  - 21. Du, B., Sun, H., Jiang, J., et al: ‘Temperature dependent electric field distribution in ±800 kV valve-side bushing insulation for a converter transformer’, High Volt., 2020, early access.
25. 25)
  - 28. IEC 65700-2014: ‘Bushings for DC application’, 2014.
26. 26)
  - 15. Hu, J., Chen, W., Cai, Q., et al: ‘Structural behavior of the PV–ETFE cushion roof’, Thin-Walled Struct., 2016, 101, pp. 169–180.
27. 27)
  - 19. Wilson, T.: ‘Solid mechanics. Comprehensive physiology’ (John Wiley & Sons, Inc., USA, 2011).
28. 28)
  - 6. Wang, Q., Wang, H., Peng, Z., et al: ‘3-D coupled electromagnetic-fluid-thermal analysis of epoxy impregnated paper converter transformer bushings’, IEEE Trans. Dielectr. Electr. Insul., 2017, 24, (1), pp. 630–638.

Cracking risk analysis and control for high-voltage dry-type valve-side bushings

References

Related content