Delivering a 132 kV substation, 22.3 km of 33 kV cabling, and grid integration for 24 turbines
Project Snapshot
| Client | ERG Power Generation SpA |
| Location | Near Kirkconnel, Dumfries & Galloway, Scotland |
| Project Value | £5.5 million |
| Project Duration | 10 months |
| Market Sector | Renewable Energy – Onshore Wind |
| Services Delivered | Full Electrical Balance of Plant (EBoP): 132 kV substation, HV cabling, switchgear, earthing, SCADA, protection and control |
| DNO / TNO | Private network connection onto Scottish Power Transmission (SPT) 132 kV system |
| Installed Capacity | 86.4 MW — 24 × 3.6 MW turbines |
| Connection Voltage | 132 kV |
| Energy Equivalent | Clean power for ~55,000 households |
| On‑site 33 kV Cabling | 22.3 km |
Client & Site Background
Developed by ERG, the Sandy Knowe Wind Farm sits in the hills near Kirkconnel in Dumfries & Galloway. The project forms part of Scotland’s fast‑growing renewable energy pipeline, supporting national decarbonisation goals and helping meet rising UK electricity demand through clean generation.
With 24 turbines, each rated at 3.6 MW, Sandy Knowe is a major contributor to local energy security and provides significant community and economic benefits.
The Challenge
ERG required a complete, high‑voltage EBoP solution, including:
- A new 132 kV substation and compound
- Integration of five turbine arrays generating at 33 kV
- Challenging construction logistics following the original contractor’s administration
- Tight energisation deadlines (including G99 testing)
- Delivery under a new multi‑contractor structure while maintaining programme certainty
- Ensuring robust grid compliance for connection to the SPT 132 kV network
Powersystems re‑mobilised to site in April 2022, taking over critical works to bring the project back on track.
Our Engineering Solution
Powersystems provided a full turnkey EBoP solution, including:
High‑Voltage (132 kV) Infrastructure
- Design & build of 132 kV substation and compound
- Grid transformers (33/132 kV, 60 MVA units)
- 132 kV structures, busbars, and disconnectors
- Dead‑tank circuit breakers
- Voltage transformers
- 33 kV capacitor bank
- Auxiliary earthing transformers (33/0.415 kV)
33 kV Wind Farm Infrastructure
- Installation of 22.3 km of 33 kV cabling across the site
- Turbine array connections across five arrays
- Earthing for both substation and turbines
- Ten‑panel 33 kV Schneider WS switchboard
- Full LV, control, protection, and communications cabling
Control, Protection & SCADA
- Interface and protection systems
- Control panels
- SCADA integration for turbines, switchgear, and grid interface
- Communications and signalling cabling
Design Deliverables
- Cable loss calculations
- Transformer bund design
- HV/LV cable sizing
- Control and signal cable design
- HV and LV network design
- Full civil GA for substation and compound
Ancillary Works
- Substation building services: lighting, heating, small power, fire & intruder alarms
- Compound lighting and custom control panels
Project Process
- 2016: Planning permission granted by Dumfries & Galloway Council
- May 2021: Construction begins under original principal contractor
- Contractor failure: Site pause and restructuring
- April 2022: Powersystems re‑mobilises; construction restarts
- May–Sept 2022: Accelerated electrical works, cabling, switchgear installation
- 5 October 2022: Successful 132 kV energisation by SPT
- Feb 2023: All turbines exporting and site fully operational
Project Facts & Figures
- 86.4 MW installed capacity
- 24 turbines × 3.6 MW each
- 5 turbine arrays feeding 33 kV network
- 22.3 km of 33 kV cabling
- 132 kV substation designed & built
- Ten‑panel Schneider WS 33 kV switchboard
- Two 60 MVA 33/132 kV transformers
- 33 kV capacitor bank installation
- Power for ~55,000 homes
Technical Specifications
132 kV Systems
- Grid transformers: 33 kV to 132 kV step‑up
- 132 kV dead‑tank circuit breakers
- 132 kV inductive VTs
- Disconnectors & earth switches
- Structures, equipment stands, and busbar arrangements
33 kV Systems
- Ten‑panel Schneider WS switchgear
- 33 kV capacitor bank for power‑factor correction
- Array cabling across five circuits (22.3 km)
- Turbine earthing and substation earthing
LV & Control
- 110 V DC charger
- Control & protection cables
- SCADA equipment and fibre network
- Lighting, small power, HVAC, and life‑safety systems
Protection & Commissioning
- G99 compliance testing
- Points on Wave (PoW) switching
- 132 kV protection scheme
- Full HV/LV test regime — VLF, IR, continuity
- Interface testing with SPT’s transmission network
Partnerships
- ERG Power Generation SpA — Project owner
- Jones Brothers Civil Engineering Ltd — Principal civil contractor
- SP Transmission (SPT) — 132 kV network operator
- Powersystems — EBoP contractor (design, install, commission)
Key Risks & Mitigations
- Principal contractor collapse – Mitigation: Rapid re‑mobilisation; takeover of incomplete works; re‑sequenced programme.
- 132 kV energisation and protection complexity – Mitigation: Detailed protection studies; interface coordination with SPT; staged commissioning.
- Challenging terrain and weather – Mitigation: Adaptive construction methods and resilient HV installation processes.
- Tight grid‑code (G99) deadlines – Mitigation: Priority scheduling, additional engineering resources, collaborative resolution with client and SPT.
Environmental Considerations
- Annual output targeting 250 GWh of clean energy
- Low carbon footprint construction philosophy
- Supports Scotland’s commitment to net‑zero by 2045
- Biodiversity‑sensitive turbine siting and environmental mitigation
Economic & Community Benefits
- Provides clean power to 55,000 homes
- Significant local supply chain engagement
- Long‑term investment in rural infrastructure
- Community benefit fund of £5,000 per MW, supporting local initiatives
- Strengthens Scotland’s renewable energy leadership
Future Prospects
Sandy Knowe positions ERG strongly within the UK renewables market, demonstrating capability for subsidy‑free and large‑scale wind development. The wind farm’s infrastructure is engineered for longevity, efficient operation and reliable grid performance.
Related Projects
- Glen Kyllachy 48.5 MW – 132/33 kV EBoP
- Sneddon Law 30 MW – 33 kV EBoP
- UK Onshore Wind (33–132 kV grid connections)
- Large‑scale substation design and build
Delivering a 132 kV wind farm or large scale renewable project?
Powersystems provides complete EBoP, HV substation, cabling and grid‑connection solutions for utility‑scale wind developments.