Grid Capacity Enhancements

The national grid currently delivers a peak power of about 60GW to UK customers.  The grid connects generators in what were coal producing areas of the midlands, coastal nuclear stations and gas fired generators to the major cities and industrial areas.  As we move toward greater use of renewable energy the grid must be enhanced to cope with energy sources that fluctuate wildly.  There are considerable difficulties but we must learn to tolerated the characteristics of these assets.  If we want wind farms to be at sea then they will have to be connected to wher we live and work.

Wind farm output varies between full rated output to zero averaging perhaps 30% of rated capacity.  Solar energy production could be undertaken by housholders but varies with cloud caver and obviously is zero at night.  Biomass generation, energy from waste and nuclear power is of course much more predictable.  The efficiency of renewable forms of generation and the investment required is controversial.  Small plants tend to be less efficient than large and some forms of generation are only worth the environmental damage they produce if the heat they produce is used.  The overall effect is that the grid will remain necessary to shift power from its source at any moment to the user but the sources will be more numerous, more variable and in new locations.

As we know, National Grid is responding to requests to connect new generating capacity in our area by proposing that it increases the capacity of the 400kV grid connection between Bramford and Twinstead Tee in Essex.  They propose that this should take the form of an additional 400kV twin circuit line to supplement the existing line taking one of four corridors between the end points.  In addition a number of existing connections will be up-rated by replacing conductors, particularly that to Norwich, beside the A140.  The sub-station at Bramford will be upgraded at a cost of £120 million. 

My own view is that the proposed lines will be obtrusive in any of the corridors with those where the line crosses high open country worse than areas where land form and vegetation form a partial screen.  However I do not see any clear choice between routes on this basis.  All have sections that offer screening and sections that do not.  Twin pylon lines like that from Bramford to Sizewell are much more obtrusive that a single line but I do not believe that this is sufficient to warrant intrusion on an entirely new group of people, a new area of countryside and the consequent damage to our tourist industry. 

Underground lines would be unobtrusive in operation but very disruptive during installation and at a cost.  Estimates of that cost vary widely from a European estimate of 7 times the cost of overhead to 17 to 25 times in estimates from National Grid.   I believe that underground options should be explored in some detail and take into account improving technology and the cost reductions which are occurring as under-grounding for 400kV connections is forced by activist pressures.   The National Grid “Optioneering Report” points to recent technology change as a driver for significant cost reduction in the Bramford substation upgrade.  Options such as in tunnel installation of gas insulated or polyethylene (XPLE) insulated cables should be considered with realistic cost estimates taking account of the lifetime reduction in circuit loss and balanced against the full costs of long term damage to human habitat.

We should remember that although increased capacity is necessary to allow us to exploit an increase in nuclear and offshore wind generation that capacity is not required for some years.  I would urge National Grid to evaluate alternative technologies fairly, grasp the nettle, go for underground lines and gain the advantages of lower fault incidence, reduced loss, fewer planning issues and less damage to our quality of life.

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