Network Assessment

Network Assessment


Most people in the UK are familiar with the electricity supply companies since they send the electricity bills. The 6 largest electricity suppliers in the UK are: Centrica, EDF, EON, NPower, Scottish Power and Scottish and Southern.

The UK physical electricity system is actually comprised of three additional components:

  1. Generation (Power stations, eg Drax)
  2. Transmission (High voltage ‘Super Grid’)
  3. Distribution (Distribution Network Operator, DNO)
Electricity Distribution Companies – Figure courtesy of the Energy Networks Association (ENA)

It is the Distribution Network Operator (DNO) who would be responsible for connecting a wind turbine to the electricity grid rather than the electricity supply company. There are eight DNOs in the UK; CE-Electric (YEDL & NEDL), EDF Energy Networks, Electricity North West, EON Central Networks, Northern Ireland Electricity, SP Energy Networks, SSE Power Distribution and Western Power Distribution.

When a proposal to install embedded generation, such as a wind turbine, is put forward the DNO is legally obliged to provide a connection to the grid. However, the 'sting in the tail' is that this is not free and the DNO is entitled to charge for the costs involved in providing and maintaining the connection.

The problem

Depending upon the required modifications to the DNO's network (often referred to as 'upgrade' or 'reinforcement') the DNO charges can be substantial. It is possible in sparsely populated areas that the local network will not be sufficiently 'strong' to accept the power from the proposed project. This is often a concern given that wind turbines are usually installed in rural locations.

Grid connection

The level of DNO costs often seem surprising high to our clients not familiar with grid connection issues. For turbines in the size range 50 – 500kW we have seen projected connection costs vary from less than £10,000 to over £500,000. This obviously has a huge bearing on the financial viability of any proposed project and makes it vital to pick sensible options early in the project.

These factors can often lead to something of a 'chicken and egg' situation. The DNO is naturally unable to provide a reliable quotation since the turbine has not been selected and the electrical design is not complete – but the client cannot choose the best optional without gauging the likely connection costs.

For example it would be vital to know early on if the existing cabling and site transformer were able to accept generation up to 120kW without modification whilst over 200kW would require several miles of the 11kV network to be re-conductored. In this case a Northwind 100 (100kW) or Endurance E3120 (50kW) wind turbine is likely to show a superior financial return to an ACSA A27 (225kW) or WES30 (250kW) machine.

Redcotec network assessment

Using geographic maps of the high voltage network, system schematics, other system data and turbine generator characteristics it is possible for Redcotec to provide an initial indication of any anticipated network limitations (e.g. voltage rise). Our ‘Network Assessment’ will identify the most promising grid connection point, location of the relevant primary substation(s) and will also provide a view on the expected costs and difficulty of connecting a range of different types of turbines.

This mechanism provides a low cost solution to the potential stumbling block mentioned above and also avoids becoming tied in to a single turbine manufacturer before the full facts are known.

Given that grid connection costs are often the second largest cost category after the purchase of the turbine itself, they can significantly affect project financial performance.

Our aim at Redcotec is to provide independent advice early in the project design so that you can be sure to select the wind project with the best overall returns.

More information

Training courses

Next Steps

  1. Request our PDF on 'Grid Connection Assessments and DNO Applications' by sending an email to
  2. Review the document and pricing structure.
  3. If you wish to proceed, get back in touch with Redcotec and provide some basic details such as the site boundary and your preferred wind turbine(s).
  4. Redcotec will prepare a full 'Network Assessment Report' summarising the grid connection situation at your site, the anticipated connection costs and likely impact on overall project financial returns.
  5. At this point many of our clients retain Redcotec to work on other aspects of their wind project, however there is absolutely no need or obligation to do this. You will have the grid connection information required to approach wind turbine manufacturers and installers to progress the size and type of project that is going to work best for you.

Training courses

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