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Value: Multi Million
Voltage: 66kV
Duration: 16 months

66kV Electrical Installation

The client required a new cable installation comprising single, dual, and triple 66kV circuits and pilot cables along a 10km route in the London Borough of Hillingdon, connecting into SSE’s network at Iver.

CHALLENGE

Utility crossings faced significant constraints: inadequate duct capacity at the River Colne bridge and high-risk congestion near the River Pinn due to existing high-voltage and telecoms infrastructure. Additional environmental and health risks included flooding, Weil’s disease, and potential impacts on habitats such as bats.

WHAT WE DELIVERED

  • JSM planned, managed, and coordinated all phases of this multi-million project, including detailed design, permitting, construction, commissioning, and handover.
  • The team installed three 66kV circuits to SSE and IDNO standards across Uxbridge and West Drayton, navigating congested roads and utilities.
  • The Special Engineering Difficulties (SEDs) included two specialist river crossings under environmental permits while minimising disruption through proactive stakeholder engagement. Achieved by creating a temporary dam and installing a flume pipe to divert the water and enable open-cut works.

10km

route

66kV

circuits

11kV

circuits

SPECIALISMS USED

  • Cable installation
  • Principal contractor
  • Environmental permits
  • Special Engineering Difficulties (SEDs)
  • Traffic management
  • Safe excavation
“This was a complex route through busy urban areas, so planning and coordination were critical from day one. By taking a proactive approach to constraints and working closely with stakeholders, we were able to keep the works moving while minimising disruption to the local community.“
Stephen Bradley
New Business Director

FROM CONCEPT

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TO CONNECTION

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Value: Multi Million
Voltage: 33kV
Duration: 12 months

33kV Solar Farm Connection

The client required the design, installation, and commissioning of a 35MVA 33kV DNO switchroom and cable route in Essex.

THE CHALLENGES

An adjacent third-party project required excavation along the same route, creating a high risk of disruption to local residents, alongside the challenge of securing design approval from UK Power Networks

WHAT WE DELIVERED

  • Works included detailed design and approvals, installation of a 3.6km 33kV cable route, and post-construction commissioning and energisation
  • An adjacent 3rd party project required a collaborative shared trench arrangement

35

MVA

3.6km

33kV CABLE ROUTE

33kV

 DNO

 SWITCHROOM

specialisms used

  • Principal designer
  • Compound construction
  • DNO switchroom & substation
  • 3.6km cable route
  • 33kV Cables & Duct installation
  • LVAC supplies
  • Jointing & Terminations
  • Hot and cold commissioning
    with Energisation
“Careful planning and close collaboration were key to navigating the approval process and coordinating the works. That allowed us to maintain programme and deliver a reliable outcome without unnecessary disruption.“
Martyn Crocker
Operations Director

FROM CONCEPT

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TO CONNECTION

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Value: Multi Million
Voltage: 33kV
Duration: 8 months

33kV Solar Farm Connection

The client required the design and delivery of a 20MVA 33kV DNO switchroom and cable route for a solar development in Staveley, Derbyshire.

THE CHALLENGES

Design approval from NGED presented a key challenge, which was addressed by working closely with the client, their contractors, and NGED to develop an acceptable design. Additionally, potentially disruptive streetworks required careful management, with the JSM Streetworks team collaborating with the local highways authority to secure permits and minimise impact on the local community.

WHAT WE DELIVERED

Supplied and installed a 33kV DNO switchroom including battery chargers and a metering room, along with 3.1km of 33kV cable duct installation, cable pulling, and jointing

20

MVA

3.1km

CABLE DUCT

 INSTALLATION

33kV

DNO

SWITCHROOM

specialisms used

  • Compound construction
  • DNO switchgear & substation
  • 33kV Cables & Duct installation
  • LVAC supplies
  • Jointing & Terminations
  • Hot and cold commissioning
    with Energisation
“Early coordination and close collaboration were key to keeping this project on track and minimising disruption.“
Martyn Crocker
Operations Director

FROM CONCEPT

icon

TO CONNECTION

snap shot
Value: Multi Million
Voltage: 33kV
Duration: 8 months

33kV Solar Farm Connection

The client required the design, installation, and commissioning of a 15MVA 33kV DNO switchroom and cable route in Basildon, Essex.

THE CHALLENGES

The cable route needed to cross the busy A127 into London, creating congestion and logistical constraints. At the same time, a nearby third-party project planned to excavate along the same route, increasing coordination complexity and the risk of disruption to local residents.

WHAT WE DELIVERED

  • JSM provided detailed design and approvals, supply and installation of the switchroom with battery chargers and metering room, and 4.2km of 33kV cable ducting with cable pulling and jointing
  • Horizontal Directional Drilling (HDD) was used to cross under a busy road
  • Collaboration with an adjacent 3rd party project sharing the same route avoided multiple excavations on a busy road

15

MVA

4.2km

CABLE DUCTING

33kV

DNO

SWITCHROOM

specialisms used

  • Principal designer
  • Principal contractor
  • Compound construction
  • Compound earthing
  • 4.2km cable route
  • 33kV Cables & Duct installation
  • LVAC supplies
  • Jointing & Terminations
  • Hot and cold commissioning
    with Energisation
“Delivering this scheme required a joined-up approach from design through to energisation, with a strong focus on coordination throughout. By working closely with stakeholders and planning around key constraints, we were able to keep disruption down while maintaining a smooth and efficient delivery.“
Martyn Crocker
Operations Director