A number of wind turbines were granted planning permission to be connected to the local 11 kV distribution network. The nearest electrical 11kV connection point, however, was located 2.8 km away, and the land in between both the wind turbine and the 11kV connection point was not owned by the client. This meant that it proved difficult to obtain wayleaves to install a new 11kV cable across the privately owned land. An alternative solution was to install a new 11kV cable at the side of an existing public road with a total route length of 4.8 km.
Using the electrical power software ETAP Engineering Power Solutions conducted a load flow and short circuit study to assess the impact of what the new wind turbines would have on the voltage and assess the magnitude of the additional short circuit current at the 11 kV point of connection. SP Energy Networks accepted the load flow and short circuit study report and granted connection to the 11 kV distribution network.
Engineering Power Solutions proceeded with the design and was requested to produce a detailed design for an 11kV switch station and an 11kV substation at both ends of the new 11kV cable. To enable the electrical contractors to quote for the work, the EPS electrical design workpack included:
- cable routing drawings
- lighting and small power drawings
- electrical protection settings schedules
- Substation location / site drawings
- LV and HV cable calculations
- single line diagrams
- schematic diagrams
- earthing drawings
- 11kV switchboard specifications
- 415V switch gear specifications
- 11kV / 415V transformer specifications
- Substation & switch station layout design
- Co-ordination with civil designers
The wind turbines were successfully installed and connected to the 11 kV distribution system to produce a maximum of 2.4 MW of electrical power (an average of 21,024,000 kWh per year). This is the equivalent of supplying 840 homes.
