ZEFAL The Zero Fault Level Generator for Active Urban Networks

The current London Plan issued by the Mayor of London, requires that 10 per cent of energy demand should be met through on-site renewable generation. Draft Further Alterations to the London Plan published in February 2007 go one step further by specifically requiring new developments to have energy supplied by Combined Cooling Heating and Power (CCHP) systems wherever feasible and to reduce their CO2 emissions by a further 20 per cent through the production of onsite renewable energy generation. It is expected that other major cities both in the UK, Europe and internationally will follow variations of this approach and that the required percentages will escalate over time The rapid expansion of local generation within high load density areas - such as major cities - is rapidly eroding the remaining available fault level headroom on existing distribution networks. A survey in 2003 indicated that some 200 substations had less than 5% fault level headroom remaining and that 72% of UK substations (900) had less than 25% headroom. Already in London's Docklands, City and West End where headroom is near or at zero, approx. 6 schemes each of 1.5 to 3.5 MVA a year are not proceeding due to fault level constraints. Additional connection charges totalling 5-10m pa, necessary to overcome fault level constraints using conventional engineering solutions, render these schemes uneconomic to the developers. The number is expected to double during 2007/8. The proposed development will tackle this issue at source by permitting the connection of large numbers of rotating machine generators to city and urban networks without contributing to fault levels. This will allow the rapid and low cost connection of many other fault level contributing devices such as conventional motors and generators as well as PV sources and induction wind machines. The criticality of this problem means that a variety of fault level management solutions are already being internationally researched and developed including superconducting and power system electronic approaches. These developments are aimed at providing greater fault level headroom on existing networks. This is seen as being both essential and complimentary to the potential elimination of fault level contributions from a new breed of rotating generators particularly suitable for CCHP and biomass generation from waste. Lack of fault level headroom is a major constraint to the rapid and economic connection of distributed generation required by national and regional planning policies in UK cities to reduce the UK's CO2 emissions. In this basic research stage we aim to establish the feasibility of developing a Zero Fault Level Generator for Active Urban Networks, and to produce a demonstration generator in the 25-50kW range with full fault-ride through capability and provision to make active contributions to voltage, reactive power and frequency support in nromal operation and in post-fault recovery.