As it is known the load of distribution cables is not constant with respect to the daytime, increasing the current in some hours may lead to an increase of soil surrounding the cable resistivity due to the migration of soil moisture content. Formation of dry zones may cause failure of cable insulation. Also because the soil thermal properties change with time according to the weather conditions of different seasons, the current capacity changes significantly from time to time. This paper studies the effect of dry zone formation during load cycling of underground cables on their temperature rise and the temperature distribution in the surrounding which is not considered by IEC 60853-2. The thermal model of the cables using the thermoelectric equivalent method is modified by including the thermal soil resistivity variation with soil temperature and moisture content. The finite element method is used also in this study to obtain heat map of the cable and surrounding soil. Additionally, experimental work of three soil types was investigated to study the effect of temperature and moisture content variation on the soil thermal resistivity and the dry zone formation of each soil type. Field measurements of temperature distribution surrounding the cables are done.

References

1. 1)
  - 29. Gouda, O.E.: ‘Environmental impacts on underground power distribution’ (IGI Global publications, Book, 2016).
2. 2)
  - 28. Milne, A.G., Mech. E., M.I., Mochlinski, K.: ‘Characteristics of soil affecting cable ratings’, Proc. IEE, 1964, 111, (5), pp. 1017–1037.
3. 3)
  - 20. Rerak, M., Ocłoń, P.: ‘Thermal analysis of underground power cable system’, J. Therm. Sci., 2017, 26, (5), pp. 465–471.
4. 4)
  - 19. Naskar, A.K., Bhattacharya, N.K., Saha, S., et al: ‘Thermal analysis of underground power cables using two dimensional finite element method’. Int. Conf. Condition Assessment Techniques in Electrical Systems (CATCON), Kolkata, India, 6–8 December 2013.
5. 5)
  - 23. Lewis, R.W., Nithiarasu, P., Seetharamu, K.N.: ‘Fundamentals of the finite element method for heat and fluid flow’ (John Wiley and Sons Ltd, UK, 2004).
6. 6)
  - 12. Kellow, M.A.: ‘A numerical procedure for the calculation of the temperature rise and ampacity of underground cables’, IEEE Trans. Power Appar. Syst., 1981, PAS-100, (7), pp. 3322–3330.
7. 7)
  - 14. Koopmans, G., Gouda, O.E.: ‘Transport of heat and moisture in soils with hysteretic moisture potential’. Proc. Fourth Inter. Conf., Swansea, UK, 15th–18th July, 1985, vol. 2, pp. 846–874.
8. 8)
  - 26. Groeneveld, G.J., Snijders, A.L., Koopmans, G., et al: ‘Improved method to calculate the critical conditions for drying out sandy soils around power cables’, IEE Proc., 1984, 131, (2), pp. 42–53.
9. 9)
  - 18. Olsen, R.S., Holboell, J., Gudmundsdóttir, U.S.: ‘Dynamic temperature estimation and real time emergency rating of transmission cables’. Presented at the IEEE Power Energy Soc. Gen. Meeting, San Diego, CA, July 2012, pp. 1–8.
10. 10)
  - 27. Donazzi, F., Occhini, E., Seppi, A.: ‘Soil thermal and hydrological characteristics in designing underground cables’, Proc. IEE, 1979, 126, (6), pp. 506–516.
11. 11)
  - 25. Rasoulpoor, M., Mirzaie, M., Mirimani, S.M.: ‘Electrical and thermal analysis of single conductor power cable considering the lead sheath effect based on finite element method’, Iran. J. Electr. Electron. Eng., 2016, 12, (1), pp. 73–81.
12. 12)
  - 5. Gouda, O.E., Adel, Z.E.D., Ghada, M.A.: ‘Effect of the formation of the dry zone around underground power cables on their ratings’, IEEE Trans. Power Deliv., 2010, 26, (2), pp. 972–978.
13. 13)
  - 9. Carlos, G., Antonio, F.O., José, C.: ‘Theoretical model to calculate steady-state and transient ampacity and temperature in buried cables’, IEEE Trans. Power Deliv., 2003, 18, (3), pp. 667–678.
14. 14)
  - 21. Flatabo, N.: ‘Transient heat conduction problems in power cables solved by the finite element method’, Trans. PAS., 1973, PAS-92, (1), pp. 56–63.
15. 15)
  - 4. Gouda, O.E., El Dein, A.Z.: ‘Improving underground power distribution capacity using artificial backfill materials’, IET Gener. Transm. Distrib., 2015, 9, (15), pp. 2180–2187.
16. 16)
  - 10. Hwang, C., Yi-Hsuan, J.: ‘Extensions to the finite element method for thermal analysis of underground cable systems’, Electr. Power Syst. Res., 2003, 64, (2), pp. 159–164.
17. 17)
  - 24. Gouda, O.E., El Dein, A.Z.: ‘Electro-thermal analysis of low- and medium-voltage cable joints’, Electr. Power Compon. Syst., 2016, 44, (1), pp. 110–121.
18. 18)
  - 16. Anders, G.J.: ‘Rating of electric power cables in unfavourable thermal environment’ (IEEE Press Wiley-Interscience, Hoboken, NJ, USA, 2005).
19. 19)
  - 17. Anders, G.J., El-Kady, M.A.: ‘Transient ratings of buried power cables part 1: historical perspective and mathematical model’, IEEE Trans. Power Deliv., 1992, 7, (4), pp. 1724–1734.
20. 20)
  - 7. Maximov, S., Venegas, V., Guardado, J.L., et al: ‘Analysis of underground cable ampacity considering non-uniform soil temperature distributions’, Electr. Power Syst. Res., 2016, 132, pp. 22–29.
21. 21)
  - 8. Zarchi, D.A., Vahidi, B.: ‘Optimal placement of underground cables to maximise total ampacity considering cable lifetime’, IET Gener. Transm. Distrib., 2016, 10, (1), pp. 263–269.
22. 22)
  - 2. Al-Saud, M.S., El-Kady, M.A., Findlay, R.D.: ‘A new approach to underground cable performance assessment’, Electr. Power Syst. Res., 2008, 78, pp. 907–918.
23. 23)
  - 13. IEC Standard 60853-2: ‘Calculation of the cyclic and emergency current ratings of cables. Part 2: cyclic rating factor of cables greater than 18/30 (36) kV and emergency ratings for cables of All voltages’, Publication 853-862, 1989.
24. 24)
  - 22. Perko, L.: ‘Differential equations and dynamical systems’ (Springer-Verlag, New York, Inc., 1991, 3rd edn., 2001).
25. 25)
  - 1. IEC publication 60287-1-3: ‘Calculations of the continuous current rating of cables (100% load factor)’, 1982.
26. 26)
  - 3. de León, F., Anders, G.J.: ‘Effects of backfilling on cable ampacity analyzed with the finite element method’, IEEE Trans. Power Deliv., 2008, 23, (2), pp. 537–543.
27. 27)
  - 6. Freitas, D.S., Prata, A.T., de Lima, A.J.: ‘Thermal performance of underground power cables with constant and cyclic currents in presence of moisture migration in the surrounding soil’, IEEE Trans. Power Deliv., 1996, 11, (3), pp. 1159–1170.
28. 28)
  - 15. Philip, J.R., De Vries, D.A.: ‘Moisture movement in porous materials under temperature gradients’, Trans. Am. Geophys. Union, 1957, 38, (2), pp. 222–232.
29. 29)
  - 11. El-Kady, M.A., Horrocks, D.J.: ‘Extended values for geometric factor of external thermal resistance of cables in duct banks’, IEEE Trans. Power Appar. Syst., 1985, PAS-104, (8), pp. 1958–1962.

Load cycling of underground distribution cables including thermal soil resistivity variation with soil temperature and moisture content

References

Related content