Electricity transmission and distribution companies in the UK face serious challenges in continuing to provide high reliability from ageing networks. This is made more difficult by increasing economic and environmental pressures. The problems will become worse as the operating conditions of the networks are changed, to allow for the production of more electricity from renewable sources.To meet this challenge, network owners and operators need better knowledge of plant ageing and improved techniques to monitor its condition.As power is generated in different locations, so the pattern of current flow through the network changes. This alters the temperature of plant items (like transformers, overhead lines and underground cables), which make up the network. Other changes in operating conditions, such as when switches are operated, will affect the stresses seen by plant. We will investigate the effect of the new operating demands on individual items of plant in order to predict their effect on the reliability of the network.We will also investigate some innovative techniques for monitoring plant condition. These will range from techniques which give a general indication of the health of an entire substation, down to those which give detailed information on a specific item of plant. The work will look at new sensors, data capture, data management and data interpretation. Network owners and operators also need improved methods of protecting and controlling the network. New software tools will help them plan replacements as parts of the network wear out. Our work will help get the most power through the ageing network and allow owners to invest in new or replacement plant in a cost-effective way. All this has to be done while maintaining or improving the security of supply and taking into account interactions between gas and electricity networks. Software tools will be developed to calculate the optimum size and location of new generating plant and to calculate the cost that should be charged to transport electricity from a particular location.Finally, research into electrical plant with reduced environmental impact will allow the use of environmentally friendly replacements. There are three main aspects to this work: exploring methods of reducing the use of SF6 (a greenhouse gas), examining techniques for transmitting more power down existing lines and investigating methods of reducing environmental impacts (for example, oil leaks) from underground cable.EPSRC has assembled a team of six universities, which have the skills needed to tackle these challenges. These universities have worked closely with major electric utilities and equipment manufacturers to prepare this proposal. The industrial partners will provide a valuable contribution, both through funding and also by supplying their technical expertise and guidance.Our work will benefit electricity utilities, which will spend less on maintenance and get more for their money when buying new plant. Consumers will gain through improved reliability of their electricity supply. UK manufacturers will be able to exploit the new condition monitoring and diagnostic techniques. Society in general will benefit through reductions in environmental impact.