The Braintree / Underground Cable Option

As part of their grid reinforcement project on the Essex / Suffolk borderNational Grid have proposed to build a substation in north Essex.

The purpose of this article

Here we present what we consider an environmentally preferable, economically sound alternative solution: an underground cable from Braintree Substation to Rushley Green near Castle Heddingham.

Executive Summary

Stour Valley Underground's proposalis to replace the need for a new substation by installing an underground 132kv cable in a trench from the existing Braintree Substation through countryside with good road access and avoiding all settlements to Rushley Green near Castle Heddingham.

We argue that our solution delivers an improvement in the amenity value of the landscape, not detriments and at a lower fiscal cost than the substation alternative.

SVU propose that:-

and contend that:-

A typical 132kv underground electricity cable

The case for an underground cable instead of a substation

Background: Why do National Grid believe a substation is needed?

Far from being the major part of National Grid's Bramford to Twinstead Connection Project, the perceived need for substation is a consequence of their proposed overall grid reinforcement methodology for the Bramford to Twinstead Connection Project. If National Grid remove any part of the UK power Networks owned 132kv line between Bramford and Twinstead, then an alternative power supply for the north going line from Rushley Green will be needed.

Map adapted and annotated from NG consultation documents 

showing the location of Rushley Green and the involved powerlines

Full map of the area available from the National Grid websitehere

National Grid (NG) propose to remove the UK Power Networks (UKPN) 132kv power line and its associated pylons between Bramford and the Twinstead Tee and this would indeed would cut a supply line to Rushley Green. These UKPN pylons would, under NG proposals, be removed and replaced with much larger 400kv ones.

National Grid have proposed to replace function of the UKPN 132kv supply line by building a huge, and in the view of the affected communities, environmentally inappropriate substation in the beautiful countryside of the north Essex border. To assist you in visualising just what a substation might look like, SVU have published a gallery of images of the component parts here.

How big a project would the SVU proposed underground cable from Braintree to Rushly Green be?

The underground cable we propose is nothing like the huge installation which is needed for the Bramford to Twinstead main project where National Grid seek to bring a full 1/4 of all the electricity in the UK into and through North Essex - that is around 14 thousand million watts of power (NG supplied data). 

The peak load ever recorded on the line from Rushley Green is only 80 million watts (UKPN supplied data) - a very tiny fraction of the former number. Thus the cables required are neither overly large or challenging to install by trench burial, after which the land can be fully reinstated. This is indeed an established, tried and tested approach to 132kv connection cross country.

In order to judge for yourself the scale of works required to achieve what we suggest, you might like to read UK Power Networks own specifications for the trench required which are included in their "ENGINEERING INSTRUCTIONEI 02-0019:INSTALLATION OF UNDERGROUND CABLES - LV TO 132KV” document which is available here. To save you time we can tell you that on page 21 a diagram shows that the trench required to install the necessary cables would be around 1 metre deep and half a metre wide.

UKPN's own specification for a cable trench for 2 x 3 phase circuits at 132kv

Dimensions in mm

Note: In this article, we use the word cable to cover however many conductors are needed to achieve the connection. All conductors would be installed in one trench as in the UKPN diagram above where 2 circuits comprising 3 phases each are laid in a single half metre wide trench.

Where could any new transformers or switches be located?

There is room at the Braintree Substation site to install any new transformers and ancillary equipment that may beneeded without damaging the visual amenity of the site and its environs. It should be noted that much of the equipment needed for the substation facilities needed by our proposal already exist at Braintree Substation, asymmetric pylons and lines to feed power into the substation being an example.

The following Google Earth sourced image is of the Braintree Substation as it is currently. In this image you can see a pair of transformers and a switching station toward the top of the image near the A120.

Beside the existing transformers is some open ground which could provide a site for further transformers and switchgear.Using a photo editor, we can copy the part of the original image that contains the existing transformer and switchgear. We can then simply paste it onto the original substation image in the location we are considering. In this way we can visualise the site with additional equipment if it is required to power the proposed underground cable.

Using the same technique, we can explore the possibility that there is room for transformers and switchgear nearer the entrance to the site, south of the existing plant, toward the bottom of the site as you see it in the image below.

It is however possible that the cable can be powered by the existing equipment with little further plant required. Either way, this exercise clearly shows that any additional transformers and switchgear that might be needed to power the proposed underground cable could readily be accommodated at this industrial site with little negative impact to the amenity value of the area.

Have SVU Determined a Precise Cable Route?

Not as yet. We have simply established that determining a low impact route is possible. 

A cable route out can simply go around the town of Braintree, not through it. The following image shows the Braintree Substation site (located at the bottom of the image) with its excellent major road links for bringing in any new equipment that might be required. The image also shows that no major deviations would be needed to route the cable to the east of the A120 going in a northerly direction. Much of the route could then run parallel to the A120 and A131, along field edges, avoiding detriment to all settlements. Any roads that need traversing can be dealt with using directional drilling technology that avoids disturbing traffic flows.

The entire cable route can be run along road sides or field edges and across the landscape using field boundaries such that there is no unacceptable negative impact on agriculture or transport. Again, where a cable needs to traverse a road or water course, directional drilling, a well established and commonly used technique can be employed to avoid any disruption of roads or drainage of the land.

It is not the purpose of this paper to identify a precise route for the cable. That would have to be developed through detailed examination of routing options, environmental assessment and community consultation.It is clear however that by using GoogleEarth (as SVU have) to examine the land corridor between Braintree and Rushley Green, that a route through the country that is near to good roads and avoids all settlements is entirely feasible. A full set of Google Earth images for the entire route corridor are available on request.

Cost

To get a guide as to the cost of what we propose here we have researched similar projects in the UK. By way of example, an underground 132kv cable project of 5 times greatercapacity than what we propose was announced in September 2010 by RWE power renewables (full details here). The length of the connection is similar to that which we propose at 11.2km and the contract price for all the work is £15 million. The works are broadly in line with what we propose and uses the same technologies and methodologies. Thus we argue that the cost for our proposal should not exceed this figure. The cost for a substation is given in National Grid documentation for the Bramford to Twinstead Project as being in excess of double this figure.

Who locally could complete such a project?

Utility Installation Projects Ltd., Valley Park, Hook Lane, Hadleigh, Suffolk include a case study of their 2 km 132kv underground cable project on their websitehereand thus the expertise for such an undertaking is available locally.

Benefits

The benefits of the SVU solution are however enormous. The economy of Essex includes well over £2 billion per annum (ECC sourced data) from tourism, in part founded on the natural beauty of the county. In the north of the county this is particularly important. Local government must be aware of this and has indeed invested in building and growing the tourism industry in this area.

Our underground cable proposal would see a massive reduction of pylon blighting of the natural beauty of the landscape because all of the Essex located 132kv pylons between Twinstead Tee in Henny and Rushley Green near Castle Heddingham could be removed. And gone would be the threat of an ugly substation in this same countryside, within the view from our most important local scheduled monument, the finest Norman keep in Europe, Heddingham Castle. Natural beauty and our cultural heritage are economic resources upon which rural economic activity and employment can be built.

Who's idea initiated this proposal from SVU?

The underground cable idea came from a local resident who attendedone of our public meetings.Stour Valley Underground, an organisation peopled by regular members of the involved north Essex communities researched, explored and tested the idea to ensure that it made good economic and environmental sense.

This therefore is not nimbyism: it is simply a better solution for everyone.

In concluding this article, SVU would like to assure the people of Braintree and all communities around the potential cable route corridor, that we have proposed nothing whatsoever that is to their disadvantage, only things that are to the greater good of all of the Braintree District. 

National Grid's project could be all detriment and no benefit for this area. SVU work to turn that situation around with proposals that would haveour solution deliver economic and environmental benefit to Braintree District.