It’s the highest voltage electricity network in the UK – the ‘motorway network’ of the energy world. It transmits large quantities of electricity over long distances via wires carried on a system of mainly metal towers (pylons) and large substations. Transmission voltages in Scotland are 132kV, 275kV and 400kV. Larger generation schemes usually connect to the Transmission system.

The lower voltage parts of the system are called distribution networks. In Scotland, these local networks operate below 132kV whereas in England the distribution network includes 132kV. 

The Scottish Ministers are responsible for determination of applications submitted under Section 37 of the Electricity Act 1989. Both statutory consultees and members of the public have the right to submit their representations on the application. All representations will be considered by Scottish Ministers in their determination of the application.
The Office for Gas and Electricity Markets (Ofgem), as the regulator, has to approve all investment so project proposals are developed under license conditions.
Preferred route corridors chosen will comply with revised ‘Holford Rules’ which are the recognised industry approach to routeing overhead lines amended to reflect Scottish circumstances.

SHE Transmission are regulated by the Office for Gas and Electricity Markets (Ofgem), the regulator responsible for representing consumers' interests. Electricity consumer interests are therefore one of our key drivers and this is enshrined in our statutory duties under the Electricity Act.

In particular we have a statutory duty to develop, maintain and operate an efficient, economic and co-ordinated transmission system. Since the costs of these projects will ultimately be paid for by electricity consumers, we have a responsibility to take cost into account with due weighting in a comparison against other important factors.

During our consultation with the local community and other stakeholders we received several comments raising concerns about the potential use of Schiehallion Road during both the construction and operational phases, particularly during winter and busy months for local tourism.

Following this feedback, we have now taken the decision not to use this route and instead, propose that access during both the construction and operational phases will be from the B846. Access points for the overhead line are already established from Schiehallion Road.

A landscape and visual impact appraisal (LVIA) is currently being undertaken using substation design information. The LVIA will be one element that informs the final substation design, as well as ensuring appropriate mitigation is incorporated. This can include achieving an appropriate site level, using the existing landform features and the creation of sympathetic earth bunds and planting. Landscaping details will be submitted as part of the Town and Country Planning Consent Application.

Site 4 is our preferred site and during the planning process we will work with the local authority planners to minimise the visibility of all temporary structures and access tracks.

Three potential laydown (site compound) option areas were presented at the last consultation, however we only intend on taking a maximum of two of these locations forward. A Landscape and Visual impact appraisal is currently being undertaken and will consider the impacts of the proposed development and ways to minimise any perceived impacts.

Since the consultation we have undertaken a topographical survey of the area surrounding the site platform, although the density of forestry has made this challenging in places. As there is natural topography and forestry cover at the location, we will look to utilise this alongside any balance of earthworks to provide the optimal platform level with respect to the surrounding area.

There are currently no plans to extend the site beyond which we are currently consulting upon. As the Transmission Network continuously develops and responds to changing requirements, the proposed platform includes some additional space provision for future development, if the network requires it. Any extension to the site beyond that currently proposed would be subject to a new planning application, with associated public consultation.

The area surrounding site 2 is constrained due to the limited space available due to existing infrastructure and steep topography. In addition, the overhead line circuit that requires the reactive compensation installed upon would require diversion to tie in to the new substation site, where there is limited space to do so.

In determining the most optimum location to deliver a substation, we follow a Substation Site Selection process, which has been tried and tested on many substations within our network. This process reviews a number of factors including technical, operational, environmental and economic.

At our site selection event we presented the key conclusions which supported selection of Site 4. A number of attendees requested further detail with regard to the factors that influenced our site selection. The table below set out the key factors considered, our RAG rating of the factors which clearly shows why site 4 (Kinardochy) is our preferred site

Site 4 was favoured due to the relative size of the site when compared with site 1;

• Site 1 was constrained on multiple sides by the aqueduct,  forestry roads and an existing warehouse.
• Due to the size of the platform, the arrangement would overlap  the base of the embankment slope of the adjacent aqueduct.
Site 4 has reduced health and safety considerations during construction (site 1 is adjacent to an existing live substation and aqueduct);
• The stability of the aqueduct is a key concern and we do not wish   to introduce any risk to the stability of the hillside which supports  the aqueduct.
• We have worked in this area previously in the construction of the   Tummel 275kV substation. This substation required significant and   challenging civil engineering works to create the platform due  to underlying rock. The underlying geology has been reviewed   during site selection and it is expected that Site 1 will have   comparable conditions to those encountered at the Tummel  275kV substation site.

Site 4 will involve less modification to the existing OHL resulting in the requirement for fewer additional towers to achieve connection; Site 4 is less constrained by existing development which would negate any potential future expansion requirements.
 
Site 4 is more economic due to the reduced requirement of works on the existing OHL and the relative ease of construction when compared to Site 1 and the constraints and ground conditions described previously.  

Consideration of peatland has been addressed through initial ground investigation undertaken across the proposed site. Peat probing was undertaken at the proposed site in 2016 with further investigations in 2019 which has provided ground data to optimise the site position to avoid areas of deep peat. This has ensured the selected site has minimised impact on existing peatland.

The SNH Carbon and Peatland map 20161 indicates that there is an area of Class 1 peatland in the southwestern section of the PAN boundary.

An area of deep peat (> 3 m) was identified at the southwestern boundary of the Proposed Development (between the existing 132 kV and 275 kV OHL). However, the Proposed Substation and the construction laydown area options are all located outside of this area of deep peat.

There are no sites designated for habitat conservation located in direct proximity to the Proposed Development site.

The site plan, or electrical layout plan, provides an outline of the infrastructure that is required to meet the need of the network at this time. There is an area provisioned for the potential additional future voltage control equipment, which would only be installed as contracted generation increases and the network requirements have been clearly established.

The location plan provides an outline (edged in red) area of consideration for development. This redline provided the area within which we could optimise the layout, siting and arrangement of our proposal, including elements such as access roads, overhead line works, and forestry works.

The Category B Listed building: LB5741/ MPK10499: Tomphubil Limekiln will be used as a point of visual assessment and considered when designing the landscaping plan. Our specialist environmental consultant is undertaking an appraisal to determine the visual and cultural and built heritage impacts of our proposal. It is likely that there will be visibility from this location, however the extent of this is yet to be confirmed.

A Landscape and Visual impact appraisal is currently being undertaken and will consider the impacts of the proposed development and ways to minimise any perceived impacts.

Landscaping details will be submitted as part of the Town and Country Planning Consent Application.

It is proposed that construction traffic shall be travelling from the south on the B846. Any abnormal loads will also travel from the south via the B846. A new access point is proposed to be installed c. 1.5 km north of the B846/Schiehallion Road junction.

Pre and post conditions surveys shall be undertaken by the main contractor in advance of any development works. Any wear or tear caused, as a result of the construction traffic, shall be repaired on completion of the works.

A detailed traffic management plan will be submitted as part of our consent application, which will detail the anticipated traffic volumes.

It is proposed that construction traffic shall be travelling from the south on the B846. Any abnormal loads will also travel from the south via the B846.

The drainage arrangements are yet to be confirmed as they will be subject to the results of the ground investigation across the proposed site. However, the drainage arrangements will comprise drainage and surface water management systems to control surface water runoff.

The design principal will aim to mimic the natural drainage of the site. Due to the relatively large size of any proposed excavation it is likely the system will comprise perimeter drainage together with attenuation features discharging into Allt Kinardochy watercourse located approximately 200m to the north of the site.

We are proposing to form a new access road serving both construction and permanent access requirements. The access will be taken off the B846, connecting Aberfeldy and Tummel Bridge. In this respect, we do not envisage any restrictions to the access to the loch.

The Kinardochy substation will connect to the Beauly – Denny transmission circuit which is one of the main transmission corridors on the SHE-T network. The Kinardochy substation will allow additional low carbon generation to connect to the SHE Transmission network by allowing the electricity transmission system operator National Grid Electricity System Operator (NGESO), to safely manage voltage levels on this corridor.

This in turn will allow additional power flows from the wider network, maximising use of the existing transmission circuits.

The voltage on the GB Transmission system is continuously changing in response to varying generation and demand profiles. The voltage changes are therefore affected by factors such as time of day, season and weather conditions. SHE Transmission design the system to comply with the Security and Quality of Supply Standards (SQSS) which sets the limits for voltage changes on the GB electricity system.

The level of voltage fluctuation which is permitted is governed by the Security and Quality of Supply Standards (The SQSS). This Standard sets the limits for both planned and unplanned voltage variation. The SQSS also sets the operational limits that the UK Transmission System must comply with.

Our studies have shown us that reactive compensation is required on the 275kV circuit of the Fort-Augustus – Denny overhead line, within the Tummel bridge area, where we are observing these voltage changes. In this regard, the reactive compensation requires to be situated in close proximity to this section of network.

Full environmental impact assessments (EIA’s) as set out by the Electricity Works (Environmental Impact Assessment) (Scotland) Regulations 2017, are not carried out on multiple site options at the site selection stage.

However, we follow a consistent internal site selection process which considers a range of environmental topics as part of the overall balance of considerations, which also includes engineering and economic aspects. Examples of the environmental topics we assess during this project development stage include landscape and visual, ecology, protected species, hydrology, soils and geology, cultural heritage and noise.

The objective of the guidelines for substation site selection is to facilitate the design, consenting, construction and operation of the substation in a manner that is technically feasible and financially viable whilst causing, on balance, the least disturbance during construction and operation to the environment and the people who live, work and use it for recreation. We also commission environmental specialists to undertake a range of desk-based studies, and site surveys and walkovers in order to firstly assess each site option, and then undertake a comparative assessment of the sites, with the aim of identifying the least constrained site, based on the range of environmental criteria.

As discussed above we undertake a range of environmental assessments at the site selection stage to ensure we identify the least constrained site to take forward for subsequent consultation and consent application.

We then undertake a further detailed environmental appraisal on the proposed site prior to consent application in order to develop a range of appropriate mitigations e.g. site specific drainage plan. We have also developed a variety of environmental management plans for potential risks such as water management, pollution control measures and species protection plans. These risk mitigations, along with consent conditions and other commitments are included onto a commitment’s register and implemented on site. We also include various environmental risk mitigations into the design of our substations, including a tertiary system for oil pollution prevention, which has been reviewed and agreed by SEPA.

Our environmental consultants have been engaged to produce a detailed landscape design plan which include elements of screening bunds as well as screen planting. This will include an assessment on how we can enhance biodiversity within our site.

SSEN Transmission as part of the planning application will design a suitable landscape plan to adequately screen the substation site with the aim of preventing low level visualisation of the site.

A Traffic Management Plan (TMP) will be developed in consultation with the Roads Department at Perth and Kinross Council and Transport Scotland, with the aim of identifying the least disruptive route for vehicle movements associated with the construction of the substation, to actively mitigate the impact to the surrounding community. 
 
The local road network will be considered for both abnormal load movement and HGV construction traffic. Initial route assessments have identified the south route will be used for abnormal load movements, such as the STATCOM transformer due to the width restrictions crossing the River Tummel at Tummel Bridge. HGV and general construction traffic route assessments will consider the existing road use in the area, geometry, long term condition and degradation and as such mitigation and improvement measures may be required.   

Fire risk is assessed throughout the development of the project and mitigation measures incorporated into the substation design as required.  Plant and equipment considered to be a fire hazard, along with any element at risk, will be assessed and a fire protection design basis process is followed. This ensures appropriate fire protection measures are implemented as part of our proposals.

Fire safety is of the upmost concern and is a priority consideration when designing any of our assets. Any fire hazards identified within the substation will be risk assessed and thorough mitigation measures will be designed and implemented as required to ensure all elements at risk (including third party property) are protected.

The main item of equipment that could have an impact on the environment if exposed to high temperatures is the STATCOM transformer.  If the transformer was exposed which resulted in a fire it would release burnt hydrocarbon gases due to the insulating oil burning off. This would need to be extremely high temperatures to cause this and is considered an extreme event since the equipment is designed to operate at temperatures of +40°.

Standard substation design is based on an external arrangement which allows for safe operation, maintenance and control of fire risk. A subterranean transmission substation will have significantly increased fire, construction and operational safety risks.

The area identified (NN765588) is comparably constrained to the Site 2 option due to the limited space available as a result of existing linear infrastructure and its topography.  In addition, the overhead line circuit that requires the reactive compensation installed upon would require diversion to tie in to the new substation site, where there is limited space to do so.

For decades, SF6 gas has been used extensively across the electrical industry as an insulating gas for switchgear in substations. SF6 gas was chosen for its excellent insulating properties making it possible to reduce equipment size and improve reliability and safety. However, SF6 gas is a greenhouse gas and as such, if released, it is harmful to the atmosphere. 
 
In 2019 SSEN Transmission became one of the first transmission operators in the UK to install SF6 free circuit breakers on its network on 132kV switchgear. As part of SSEN Transmission’s commitment to reduce its greenhouse gases, it is working with suppliers to install SF6 alternatives where the technology is available, as well as working with the Energy Networks Association to support industry wide adoption of these technologies. 

SSEN Transmission has been one of the first transmission operators in the UK to install SF6 free circuit breakers on its network. Due to limitations of the technology available, the scale of the equipment, siting requirements and the potential for future installation,  gas insulated switchgear (GIS) is required at Kinardochy substation. This ensures we can develop an optimised substation solution with a moderate footprint with respect to the locale and the sensitivities.  
 
An air insultated switchgear (AIS) option has been considered as part of our early options assessment and a suitable comparison carried out to assess the viability of this option against the proposed GIS option. The installation of an AIS design would lead to a decrease in SF6 but not remove it from the site completely.  Further to this, the AIS substation would increase the overall platform footprint, increase the vehicular traffic during construction and increase the visual impact of the overall site.

Within our timescales for delivery, there are no viable SF6 alternative gases for 275kV or 400kV voltages, which is the required voltage range of the switchgear. We are committed to using SF6 alternative gases to reduce greenhouse gases, SSEN Transmission is working with suppliers to install  SF6 alternatives where the technology is available. It is our intention to use an SF6 alternative gas, where possible, to reduce the volume of SF6 we have on site.
 
There are options for interconnecting the substation components via gas insulated bars (GIB) and lines (GIL) that have been tested at these voltages on other Transmission Operators networks. We are readily exploring available alternatives in our commitment to deliver a net zero network.

As referred above, an Air Insulated Switchgear (AIS) substation had been considered in our early review of site designs and options. This was ruled out during our site selection process due to the scale of the infrastructure balanced against a number of other factors we require to consider as part of our proposals. 
 
Consequently, an AIS solution requires a much larger land take and accordingly much longer civil engineering works and total construction activity.  This solution would not allow us to meet our contracted date to complete the reinforcement.

The building will be designed such that all ducts, trenches etc at low level (below ground) will be sealed, not only to prevent the escape of gas and spread of fire but also to prevent any vermin or other small animals entering the building. SF6 gas is heavier than air and any leak will sink to the lowest point within the building.  
 
Although a leak is rare, should SF6 be released, through the design of the switchgear and with the appropriate maintenance and monitoring of the equipment this will ensure that any leakage is detected and rectified as soon as possible.

Yes, we have provisioned for the installation of 400kV capable equipment. Operating initially at 275kV. This will  minimise the amount of work required to upgrade the system to 400kV in future, when it is required on the network.

Our system studies have identified a requirement for reactive compensation on the 275kV circuit in our proposed year of delivery. If both circuits were 400kV, reactive compensation would still provide a benefit to network security and voltage control.
 
We have designed the reactive compensation substation with 400kV rated equipment, which will initially operate at 275kV. The proposed equipment will require only minor modification to operate at 400kV.

As an unmanned site, the permanent lighting solution will generally support access and egress to the substation during emergencies.  We have taken on a number of queries regarding lighting throughout the consultation and will work with our appointed contractor to optimise the lighting positioning, function and use to minimise unnecessary  light pollution.

During construction we will work with our appointed contractor to minimise lighting on site to that which is required.  In some circumstances, we may require to work outside of the hours of 7am and 7pm.

SSEN Transmission will install connections into proprietary fibre cable communications system as part of the construction and will not require a BT landline.

The fibre cable included within SSEN Transmission overhead line is limited to SSEN Transmission’s use only and for third parties to obtain use of this for commercial purposes, they will be required to obtain their own wayleaves prior to making use of the line.

This will form part of the landscape design and mitigation plan which will be submitted as part of the planning application.

SSEN Transmission has undertaken noise measurement as part of the survey process in investigating the site and will submit this information as part of the planning application, where the Planning Authority will set the limits to which SSEN Transmission will have to have its equipment conform.

We have appointed a landscape and visual consultant who are assisting us with our application, they have been in discussions with Perth and Kinross Council with regard to the selection of appropriate viewpoints.

The environmental assessments will include an assessment on archaeology and cultural heritage; both designated and non-designated.

SSEN Transmission as part of the landscape mitigation are aiming to prevent any long term low level visualisation of the substation and this would include views taken from the lime kiln.
 
Whilst we cannot guarantee, we will see what we can do as part of landscape mitigation design works.

We do not believe it is possible to deliver our plans without taking a long-term, sustainable view of our projects, both individually and combined, considering the impact on the environment, society and the wider economy. In developing this project, we have carried out detailed environmental assessments which include ecology and ornithology. During the construction period access to feeding on this loch will not be restricted at any time. The construction works will close in the evenings and as such there will still be opportunity for feeding.

SSEN Transmission expect to submit their application for planning consent under the Electricity Act to Perth and Kinross Council in quarter 3 of 2020.
The application will be advertised and opportunities for submission of representations will be available at that time. SSEN Transmission will continue consulting with the Scottish Government, Local Energy and Consents Unit, Perth and Kinross Council and other key statutory bodies as well as the local community prior to submitting a  formal application.