33KV Overhead Line Planning Statement

substations as is required by the statutory requirements in this regard laid on the Authority.

1. The objectives for the future arrangements of electricity supply must provide for:-

a) an adequate and secure supply of electricity by the use of an efficient and economic system of transmission and distribution; b) acceptable standards of customer service; c) the electricity supply requirements of both existing and future customers; d) the preservation of natural beauty and amenity.

1. Short term estimates of future demands can lack precision as year to year variations in demand tend to be dominated by the effects of weather. Over the last few years, however, demands have increased at a rate greater than expected (Doc. 1. Diags. 105,106,107). Current forecasts show that the capacity of the Pulrose/Castletown line will be exceeded in 1990 without there being an increase in the number of consumers. Currently taking place in the south are several new domestic, commercial and industrial developments all of which will require electricity supplies in 1990. The demands created by these have been estimated to be 2 MVA by 1991; there is, therefore, a need for an increased transmission capacity to be in place by Autumn of 1990.

1. Throughout the planning process dealing with the application, careful consideration has been given to possible effects on the rural environment and visual amenity and in particular to the use of topography and natural features to lessen any effects of the proposed line. After the Authority

had decided on the form of the proposed development the following bodies were consulted:-

• Architect and Planning Officer
• Department of Local Government and the Environment
• Malew Parish Commissioners
• Santon Parish Commissioners
• Braddan Parish Commissioners
• Manx National Farmers' Union
• Manx Conservation Council
• Society for the Preservation of the Manx Countryside
• Manx Ornithological Society
• Chief Forester, Department of Agriculture, Fisheries and Forestry

All landowners and occupiers along the proposed route.

1. Points of detail regarding pole positions, minor variations and similar matters will be the subject of further detailed consultations during wayleave discussions. If the application receives consent it would be the Authority's intention to issue statutory notices to all owners/occupiers of affected land. It is hoped, however, to be able to negotiate willing consents from all the parties concerned.

Possible Methods of Necessary Reinforcement

1. The southern substation at Castletown is at Ballalough and this is supplied by a 33 KV ring (Doc. 2. Diag. 200). The system provides alternative supply routes should there be any interruption to any part of it. The section of the ring via St. John's is rated at 20 MVA. The eastern supply is via a 33 KV overhead line, erected in 1933, which has a rating of 12.5 MVA which in addition to its transmission function, supplies a number of communities along its length through several non-standard

transformers. This dual function has been satisfactory for many years but increasing loads now make the uses incompatible. Local voltage problems now occur. The peak load in the south in the winter of 1988/89 was 11.5 MVA and this is increasing. There is, therefore, now a need to provide a transmission facility of increased capacity to secure the southern area supplies, separate from a still required distribution function operating at 11 KV.

1. The options considered to effect the necessary reinforcement scheme were:-

a) To increase the capacity of the existing 33,000 volt overhead line between Douglas and Castletown. b) To install a 33,000 volt underground cable between Douglas and Castletown. c) To erect a new overhead line between Douglas and Castletown. Option A - Increase the capacity of the existing 33 KV line

1. In 1988 a short section of 20 MVA cable and a short section of 20 MVA overhead line were installed to connect Pulrose to the old section of the existing line. From this latter point the line runs via Newtown, Glen Grenaugh and Ballasalla to the Ballalough substation (Doc. 2. Diag. 201.) Local networks along the line, at various voltages are fed from non-standard 33 KV primary transformers. Increasing the capacity of the existing line would require:-

a) Reconstructing the line with bigger conductors, new poles and shorter spans. There would be an increased number of poles and changes to the existing pole positions.

b) Constructing new sections of 11 KV line to provide for supplies to the communities now supplied by the existing line. (Doc. 2. Diag. 202).

c) That part of the existing line near Ballasalla could not be reconstructed and it would have to be replaced with a section of underground cable.

1. The existing 33 KV line between Douglas and Castletown was erected in 1933. In order to supply the settlements along its length it follows a tortuous route. To rebuild it to the capacity now required would mean many long interruptions to supplies to consumers, some of these would be for some days per week over several weeks. There would be no amenity gain from rebuilding the old line and providing the required new 11 KV line. If the application route is adopted it would be possible to remove a total of some 1.5 km of the old line.

Option B - 33 KV underground cable from Douglas to Castletown

1. A reasonably direct and practical route for an underground cable is possible (Doc.2. Diag. 203). This route would use the existing short section of 20 MVA cable from Pulrose to Kewaigue and then follow tracks through fields and in the edges of the old Castletown Road through 3 settlements, then around Ballasalla to Ballalough via the Ronaldsway Industrial Estate and Great Meadow.

1. Other routes have been examined including one along the Douglas to Castletown railway track and the one along the Douglas/Castletown roadway. Each of these would involve higher costs than the route which would be preferred.

Option C - new 33 KV overhead line between Douglas and Castletown

1. Pulrose is on the southern edge of Douglas and there are adequate connections to the existing overhead line at Kewaigue.

The substation at Ballalough is on the northern side of Castletown. Possible routes between the two are largely parallel to the coast line.

1. The Development Plan makes no recommendations concerning new high voltage overhead lines. However, several areas have been identified from the Development Plan in which an overhead line would be inappropriate. These locations include the airport zone, developed areas near Ballasalla, certain other properties, areas of high tree density and areas of historical interest. Taking into account these areas there are only a limited number of route options (Doc. 2. Diag. 205) but the best practicable options have been examined.

Route A. (Doc. 2. Diag. 206)

1. From the starting point near Kewaigue the route runs to Ballachrink to then run south of the properties at Newtown, south of Ballavale, to the northern edge of Ballasalla to approach Ballalough on the west of Ballasalla. There are possible extensions of the latter to the north-west and there would be both technical and amenity difficulties at Silverdale. For these reasons this would not be a preferred route.

Route B (Doc. 2. Diag. 207)

1. From Kewaigue there would be a new section of line to the vicinity of Ballacutchal from there through the rural areas of Ballacorris and Ballanank to Ballalough through a point near the Ballamodha road where there would be the least disturbance to trees. While this route is a practicable one it would not use the existing 700 metres of existing line near Kewaigue. Additionally there is a "no go" area at the foot of Richmond Hill, the Ballacutchal section would be over high ground and the

route is not as direct as would be desirable. For these reasons this would not be a preferred route.

Route C - the Application Route (Doc. 2. Diag. 208)

1. This route would involve the use of the first part of the existing line as far as Ballachrink. The line would run to the south of Newtown then to Ballakissack, south of Ballanank to then cross the Ballamodha road. Nearer to Ballalough at Billown the new line would use the route of an existing line.

1. Each section of the route has been carefully examined to ensure that the line would have a minimum visual impact and avoid areas of specific concern. While the case for an overhead line reinforcement scheme is, in the Authority's view, overwhelming, this has not influenced the Authority's efforts to produce within the various constraints, an acceptable route in environmental and land use points of view.

1. In view of several suggestions received, the possibility of using the Steam Railway line as a route for an overhead line had been examined. In only one short section does the line run in the general direction required. The overhead line along the railway would follow a very tortuous route and it would have to accommodate 14 major bends. These changes in direction would require very substantial structures in the overhead line. There would be 8 road crossings and many trees and bushes would be affected. Properties near the track would have their amenities affected and in some cases it would not be possible to obtain the electrical clearances required for safety. It is not thought that the proposition is a practicable one.

Costs

1. As a body which has statutory duties placed on it in regard to economical operation the Authority must have regard to the costs of their proposals. The costs of the various alternatives, the line applied for and variations thereof are:-

a) Rebuilding the existing overhead line, building new 11 KV line, underground cabling from Ballasalla to the substation at Ballalough - £675,000.

b) A 33 KV, 20 MVA underground cable from Kewaigue to the substation at Ballalough, by the preferred and cheapest route - £2,520,000. c) A new overhead line as applied for between Kewaigue and the substation at Ballalough. - £325,000. d) Additional costs for undergrounding these two sections of the proposed line suggested by the Planning Committee:- i) From Knock-y-Laughan to Cooilcam - £510,000. ii) In the area of Billown - £150,000

e) An underground cable along the Steam Railway line would cost at least £500,000 more than the route that the Authority would prefer for an underground link.

All the above costs have been estimated using quotations received for similar such works. The generally experienced and accepted ratio of costs of underground cable to overhead line of 7-8:1 applies. All subsidiary costs, including those concerned with access, and compensation have been included. The costs of the refurbishment of the existing line feeding the four settlements between Douglas and Ballasalla have also been taken into account.

1. Overhead lines and underground cables have roughly equal economic lives of some, 30-35 years but this life is more affected by changes in the pattern of demands than economic factors.

1. Where an overhead on the application route would cross existing lines these would be removed and in general be placed underground. It is estimated that 3000m of existing high and low voltage overhead lines would be removed at a cost of £40,000, this has been allowed for. There would be a substantial amenity gain because of this work.

1. Undergrounding those two parts of the overhead line as suggested by the Planning Committee would cost an extra £600,000. In view of the small visual gain which would occur it is not considered that these extra costs would be justified. The overhead line in the central valley which has attracted justified criticism was not erected by the Authority's own staff.

Detailed Siting and Construction Details

1. The line would operate at 33 KV and would comply with the Electricity Act 1984, the current UK Electricity Supply Regulations 1988 and the Electricity (Overhead Lines) Regulations approved by Tynwald in 1988. The line would be constructed to the Electricity Supply Standard 43-40 dated 1 September 1988.

1. The proposed line can be conveniently divided into 4 sections (Doc. 3. Diag. 301):-

a) Section A-B using an existing overhead line, some 1 Kilometre long, erected by the Authority in 1988.

b) From Middle River to Ballachrink the existing 33 KV overhead line built in 1933 would be reconstructed for a length of some 700 metres.

c) From Ballachrink to Billown a new line some 10.2 Km long would be constructed.

d) From Billown to Ballalough there would be a reconstruction of 1.4 Km of the Castletown/Ballabeg 33 KV line which was erected in 1959.

1. The line would consist of 3 conductors mounted in horizontal formation on wood poles. The conductors would be 200 sq. mm Aluminium Conductor Steel Reinforced to BS 215. Porcelain insulators and galvanised steel work to the relevant British Standards would be used as would a number of different pole types (Doc. 3 Diag. 303,304,305).

1. Each pole would be of such a height and so placed as to suit the local contours, ensure proper mechanical loading and to satisfy the statutory clearances between the conductors and the ground, buildings and other obstacles. The nominal standard span length is 100m but this can be increased up to 144m as long as no two adjacent spans exceed 200m.

Construction Procedure

1. The construction period is estimated to last some four months, this includes access preparation, material delivery, pole erection, conductor stringing and final inspection. All work will be carried out by the Authority's own staff under the Authority's supervision. A line warden would be appointed from the Authority's line staff and his duties would include:-

a) Arranging in advance with landowners and occupiers access routes to and from the various work sites.

b) Liaising with landowners and occupiers to ensure that disturbance or inconvenience is kept to a minimum.