The Norwich to Bramford 400kV overhead transmission line known as 4YM is the last one of its type to be refurbished with new conductor and fittings since its construction in the East Anglian region. The L6 towers were designed and built by British Insulated Calendars Construction Co Ltd, (BICC) and the work took place during 1967 and 68. Towards the end of this project, the management of British Insulated Calendars Cables Co Ltd which was the parent company of the group were acquiring the interests of Power Securities which was the financial parent of Balfour Beatty and Co Ltd.
The companies had been in the same line of work for many years as overhead transmission line contractors with BICC having a small advantage as they owned Painter Brothers, OHL fabricators and Calendars Cables, the conductor manufacturer. It seemed to make sensible logic that the two competitors would merge as one but under the Balfour Beatty name. And therefore, on the 6th January 1969 the transaction was completed and what little work was available from the CEGB meant that the 400,000 volt Supergrid was almost completed from the 1960 ten year plan. Balfour Beatty did finish work back in 1969 to get the 195 tower 4YM route operational on the grid. They have now returned along this route to build a new tower on what will be the site of the new Yaxley substation. The overhead line is being refurbished in two stages over, 2022 starting from tower 1 at Bramford and working up to tower 100 at Yaxley and in 2023, completing the project.
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