Professor Len Dissado

Emeritus Professor

Professor Len Dissado

Emeritus Professor of Engineering
Electrical Power and Power Engineering Research Group

BSc, PhD, DSc (London), FIEEE, Docteur (h.c.) Univ Paul Sabatier, Toulouse
T: +44 (0)116 252 2577
F: +44 (0)116 252 2619

Location: Room 311, S Block

Main Research Interests:
The research interests of Professor Dissado are currently focussed on space charge evolution in insulating polymers, their thermo-electrical ageing, and the mechanism of  prebreakdown processes such as electrical trees. Recent work on electrical trees has concentrated on the initiation process in epoxy resins under an EPSRC ROPA award. It has been shown that the electroluminescence intensity observed during tree initiation in these materials relates to an initiation process in which recombination between charges of opposite polarity first generate new trap states. When the trap density is high enough the shallow traps form percolation clusters in the applied electric field enabling electrons to be accelerated to an energy sufficient to cause further changes and light emission through the excitation of molecules along their path.

Eventually the damage accumulates to form gas filled tubules and the tree is initiated. The figures below show experiment and simulation of the emission intensity. Professor Dissado was part of the HVDC EU framework 5 programme, helping to produce a computer programme to simulate space charge evolution in DC cable. Related work on the decay of space charge showed an early stage dominated by injection-neutralization and a later stage governed by de-trapping rates.

Some work is also being carried out on simulating the microwave dielectric response of fast-ion conductors using molecular dynamics.

Professor Len Dissado - graph

These materials behave as a pseudo-one dimensional fluid, and the simulations, which are sponsored by QinetiQ, allow theoretical ideas concerning ion dynamics in a many body system to be evaluated.

Selected Publications:
• K.Wu and L.A.Dissado, “Model for Electrical Tree Initiation in Epoxy Resin”, IEEE Trans. DEI, vol 12, pp 655-668, 2005
• L.A. Dissado, V. Griseri, W. Peasgood, E.S. Cooper, K. Fakunaga, J.C. Fothergill, “The decay of space charge in a glassy expoxy rescu following voltage removal”, IEEE Trans. DEI, vol.13, pp903-916, 2006
• F.Boufayed, G.Teyysedre, C.Laurent, S.Le Roy, L.A.Dissado, P.Segur, G.C.Montanari, “Models of bipolar transport in polyethylene”, J.App.Phys. vol. 100, pp104105-104115, 2006
• L.A. Dissado, A.Thabet, “Simulation of Electrical Ageing in insulating polymers using a quantitative physical model”, J.Phys, D: Appl Phys., vol. 41, paper 085412 (5pp), 2008

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