Dr Stephen Dodd
- Acting Head of the Electrical Power and Power Engineering Research Group
- Industrial Placement Tutor - Department of Engineering
- Senior Lecturer in Electrical Engineering
Electrical Power and Power Electrical Research Group
Electrical Power and Power Electrical Research Group
BSc, (Physics), PhD, MIoP, MIEEE
T: +44 (0)116 252 2869
F: +44 (0)116 252 2619
Location: Room 311c, S Block, Engineering
Stephen Dodd was born in Epping, England in 1960. In 1987, he received a First Class BSc in Physics from the City of London Polytechnic (now London Metropolitan University) and in 1992 a PhD degree from the same institution.
From 1992 to 2002 he was a Research Fellow at London Guildhall University and in 2002 he was appointed to a Lectureship in Electrical Power Engineering in the Department of Electronics and Computer Science at the University of Southampton. In 2007 he moved to the University of Leicester as a Senior Lecturer within the Department of Engineering. He has given invited lectures in the UK and Europe and has published more than 80 refereed journal and conference papers.
Main Research Interests:
His research interests include, electrical (dielectric), thermal and rheological characterisation of liquid and solid insulating materials and their electrical and thermal ageing characteristics. He has a long-standing interest in long-term electrical breakdown processes and the development of condition monitoring and assessment techniques for high voltage plant.
In particular, he has worked on many problems associated with electrical breakdown of insulating materials and, for the last 16 years, understanding the processes of electrical tree initiation and growth. This work has focused on systematic experimental studies of electrical tree initiation (employing an electroluminescence technique) and electrical tree growth in many polymeric materials to identify influencing factors such as mechanical stress, applied voltage, temperature, moisture absorption, and how they modify electrical treeing characteristics. Systems studied include, epoxy resins, polyolefins and composite insulation materials. Partial discharge measurements taken during tree growth have been used to provide evidence that the partial discharges and therefore the tree growth are governed by deterministic principles. In particular, evidence shows that partial discharge rates follow chaotic dynamics rather than stochastic principles.
This fundamental experimental work has been used to form computer simulation models for charge injection and electroluminescence during tree initiation and simulations of the electrical treeing process based on empirical modelling and deterministic modelling of partial discharge activity and electrical tree growth.
Such an approach has many advantages over the stochastic simulation methods that have been employed in the past. Specifically, they allow partial discharge behaviour to be modelled explicitly, such that tree extension is based on energy considerations - matching the local energy dissipated during each discharge event with the energy required to create local damage to the surrounding material. This allows the model to predict tree growth rates and the degree of branching (fractal dimension of tree growth) and establishes a methodology by which the relationship between tree growth characteristics and material factors such as bulk electrical conductivity to be explored. Ultimately, this will lead to physical models for treeing that have key material properties and influencing factors embedded within them, such that realistic predictive simulations and lifetime models can be obtained.
Fig 1: Electrical tree grown in epoxy resin Fig 2: Electrical tree growth and partial discharges
Practically, this fundamental work has led on to the development of novel condition monitoring techniques for high voltage insulation systems. These have been tailored for particular insulation materials and applications, including a capacitive monitoring technique for use where partial discharge magnitudes are often too low to distinguish, conventionally, from external electrical noise. Dr Dodd has attracted extensive financial support for his research into treeing and condition monitoring and assessment of high voltage insulators, amounting to in excess of £1.2M since 1989 from industry.
Fothergill, J.C. and Dodd, S.J., Knowledge Transfer Partnership (KTP) “to develop the capability of the company to characterise and assess insulating materials and key components for low-loss High Voltage DC (HVDC) electrical transmission” with Alstom Grid UK, £141,608 (Jan 2011 – Dec 2012).
Fothergill, J.C. and Dodd, S.J., DC Insulator Material Reliability, Nexans, France, £68,270 (Oct 2011- Oct 2014).
• Abdelmalik, A. A., Dodd, S. J., Dissado, L. A., Chalashkanov, N. M., & Fothergill, J. C. (2014). Charge transport in thermally aged paper impregnated with natural ester oil. IEEE Transactions on Dielectrics and Electrical Insulation, 21(5), 2318-2328.
• Chalashkanov, N. M., Dodd, S. J., Dissado, L. A., & Fothergill, J. C. (2014). Re-examination of the dielectric spectra of epoxy resins: Bulk charge transport and interfacial polarization peaks. IEEE Transactions on Dielectrics and Electrical Insulation, 21(3), 1330-1341.
• A. A. Abdelmalik, J. C. Fothergill, S. J. Dodd, (2012) Electrical Conduction and Dielectric Breakdown Characteristics of Alkyl Ester Dielectric Fluids obtained from Palm Kernel Oil. IEEE Trans. Dielectrics and Electrical Insulation, Vol. 19, Issue 5, pp. 1623-1632.
• J.C. Fothergill, T. Liu, S.J. Dodd, L.A. Dissado, U.H. Nilsson (2011) The Measurement of Very Low Conductivity and Dielectric Loss in XLPE Cables: A Possible Method to Detect Degradation due to Thermal Aging. IEEE Trans. Dielectrics and Electrical Insulation, 18(5):1544-1553.
• Xiangrong Chen, Yang Xu, S.J.Dodd and L.A.Dissado (2011) “Effect of Tree Channel Conductivity on Electrical Tree Shape and Breakdown in XLPE Cable Insulation Samples. IEEE Trans. Dielectrics and Electrical Insulation, 18(3):847-860.
• A.A. Abdelmalik, A.P.Abbott, J.C.Fothergill, S.Dodd, R.C.Harris, (2011) “Synthesis of a base-stock for electrical insulating fluid based on palm kernel oil”, Ind.Crops Prod. 33 532–536.
• L.A.Dissado, A.Thabet and S.J.Dodd (2010) Simulation of DC Electrical Ageing in Insulating Polymer Films. IEEE Trans. Dielectrics and Electrical Insulation. Vol. 17, No. 3, pp 890-897.
• Dodd, S. J., Lewin, P. L. and Wong, K. I. (2006) Phase Resolved Electroluminescence Measurements in Thin Films of Low Density Polyethylene Using a Charge Coupled Device Camera. IEEE Transactions on Dielectrics and Electrical Insulation 13(1) pp. 168-180.
• Vaughan, A. S., Hosier, I. L., Dodd, S. J. and Sutton, S. J. (2006) On the structure and chemistry of electrical trees in polyethylene. J. Phys D: Applied Physics, 39(5) pp. 962-978.
• Vaughan, A. S., Dodd, S. J. and Sutton, S. J. (2004) A Raman microprobe study of electrical treeing in polyethylene. J. Mater. Sci. 39(1) pp. 181-191.
• S.J.Dodd, J.V.Champion, Y.Zhao, A.S.Vaughan, S.J.Sutton and S.G.Swingler, (2003) “Influence of morphology on electrical treeing in polyethylene blends”, IEE Proc.-Sci. Meas. Technol., Vol.150, No.2, 58-64.
• Dodd, S. J. (2003). A Deterministic Model for the Growth of Non-conducting Electrical Tree Structures. Journal of Physics D: Applied Physics 36 pp. 129 - 141.
• J.V.Champion and S.J.Dodd, (2001) “Simulation of partial discharges in conducting and non-conducting electrical tree structures”, J.Phys.D: Appl. Phys., Vol.34, 1235-1242.
• J.V.Champion, S.J.Dodd, Y.Zhao, A.S.Vaughan, M.Brown, A.E.Davis, S.J.Sutton, S.G.Swingler, (2001) “Morphology and the growth of electrical trees in a propylene/ethylene copolymer”, IEEE Trans. on Diel. and Elec. Insul., Vol.8, No.2, 284-292.
• J.V.Champion and S.J.Dodd, (1999) “An assessment of the effect of externally applied mechanical stress and water absorption on the electrical tree growth behaviour in glassy epoxy resins”, J.Phys.D: Appl. Phys., Vol.32, 305-316.
• J.V.Champion and S.J.Dodd, (1998) “An approach to the modelling of partial discharges in electrical trees”, J.Phys.D: Appl. Phys., Vol.31, 2305-2314.