FROM CONCEPT

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TO CONNECTION

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Value: Multi Million
Voltage: 33kV
Duration: 10 months

21MVA Battery Energy Storage System

The client required the design, construction, and commissioning of a 21MVA Battery Energy Storage System (BESS) compound in Broadditch, Kent.

THE CHALLENGES

Site earthing presented a challenge due to the 33kV overhead line connection and the planned future 11kV connection, requiring careful consideration of combined fault contributions and differing clearance times. In addition, site constraints made plant installation difficult, as the six 32-ton batteries required a complex lifting operation into position.

WHAT WE DELIVERED

  • 6nr batteries
  • 3nr transformers
  • 460m of 33kV cabling,
  • 2-panel 33kV switchboard,

6nr

Batteries

460m

OF 33kV CABLING

3nr

TRANSFORMERS

specialisms used

  • Compound construction
  • Compound earthing
  • DNO switchgear & substation
  • Battery Installation
  • Duct installation
  • LVAC supplies
  • Jointing & Terminations
  • Hot and cold commissioning
    with Energisation

 

“From the outset, the project relied on careful design integration and coordination on site to manage constraints and ensure safe installation. That approach was key to achieving a robust and compliant end result.“
Martyn Crocker
Operations Director
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Value: > £50k
Distance: 75m
Duration: 5 days

Subduct installation in a culvert

The client commissioned JSM to increase fibre capacity beneath a dock by installing additional subducts within an existing Canal & River Trust (CRT) service culvert. The culvert naturally filled to dock water level and was subject to tidal influence from the River Thames.

Access was via 15.5‑metre‑deep shafts, requiring detailed planning to manage dewatering, tidal conditions and environmental constraints.

 

CHALLENGE

The service culvert filled to the same level as the Dock, with tidal influence from the River Thames. Deep access shafts (15.5m) and prolonged pumping were required to maintain safe working conditions.

WHAT WE DELIVERED

  • Installation of 14 no. 32/27mm sub ducts through the existing CRT service culvert
  • Continuous dewatering using high‑head pumps, coordinated with tidal cycles
  • Close coordination with Canal & River Trust, including water level management and environmental controls
  • Completion within a five‑day programme and within budget

14

no. 32/27MM

sub duct installation

15.5m

deep shafts

75m

in length

SPECIALISMS USED

  • Subduct installation
  • 32/27mm ducts
  • CRT service culvert
  • Fibre capacity increase
  • Culvert dewatering
  • High head pumping
  • Continuous pumping
  • Deep shaft access
  • Water quality testing
  • Tidal programming
“The project required a considered approach to planning and execution to manage access, environmental factors and site conditions. Maintaining that level of control was key to delivering the works safely and on programme.“
Steve Witt
Planning Manager

FROM CONCEPT

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TO CONNECTION

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Value: Undisclosed
Voltage: 400kV
Duration: 3 months

Redundant 400kV Oil Filled Cable Removal

The Network Operator required the safe removal of redundant oil filled 400V cables in Ross-On-Wye.

THE CHALLENGES

Working within a protected Site of Special Scientific Interest near the Wye River presented environmental constraints, further complicated by the presence of sensitive woodland coppice and breeding wildfowl. In addition, buried third-party services posed a risk of potential damage during the works.

WHAT WE DELIVERED

  • JSM removed a 1.98km section of redundant 400kV oil-filled cable
  • NICE (Non-Intrusive Cable Extraction) method was employed which enabled safe, trenchless extraction
  • Recovered cables were sealed and transported for recycling

400kV

redundant

cable

1.98km

oil filled

cable removed

NICE

enabled safe

trenchless extraction

specialisms used

  • Cable removal
  • Horizontal Directional Drilling
  • Joint bays
  • Backfilling
  • Oil drainage
  • Cutting
  • Recycling
“This project demonstrates how the NICE method enables us to manage complex cable removals safely and efficiently. By avoiding extensive excavation, we were able to minimise disruption while maintaining tight programme requirements.“
John Fitzgerald
Senior Operations Manager

FROM CONCEPT

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TO CONNECTION

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Value: Six figures
Distance: 32km
Duration: 3 months

Hollow Core Fibre Connection – Data Centre

The client required 32km of hollow core fibre (HCF) to be installed between Central and West London.

THE CHALLENGES

Communication and authorisation from the Canal & River Trust (CRT) for canal works presented a key challenge, requiring coordination and compliance with strict regulatory requirements.

WHAT WE DELIVERED

  • JSM planned and managed all phases of this multi-million pound project, including feasibility studies, permitting, and installation.
  • Special Engineering Difficulties (SEDs), including works crossing canals were managed in compliance with key stakeholders.
  • In addition to the 32km of HCF, 16 new chambers were constructed.

32KM

HCF

16

chambers

46m

new ductwork

specialisms used

  • As-builts drawings
  • 46 new Ductwork
  • Hollow Core Fibre
  • Splicing
  • Fibre installation

 

“There were a lot of moving parts on this project, especially working along canal routes and coordinating access. Keeping close communication with all parties made a big difference in delivering everything efficiently.“
Toby Ford
Head of Operations

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

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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, 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

FROM CONCEPT

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TO CONNECTION

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Value: Multi Million
Diameter: 160mm to 89mm ducts
Duration: 25 months

132kV Energy to Waste Connection

The client required the design, installation, and commissioning of a new 132kV electrical supply system to support energy recovery operations in Belvedere, Dartford.

THE CHALLENGES

The tidal location of the river created a significant flood risk and required careful environmental planning. Complex signal structures on constrained bridge crossings introduced additional engineering and approval challenges, while the proximity to a dual carriageway demanded strict traffic management. The site’s ecological sensitivity, including nesting birds and protected wildlife, limited construction activities, alongside the need to account for structural load and thermal expansion. The exposed installation also presented risks of vandalism and unauthorised access.

WHAT WE DELIVERED

  • Special Engineering Difficulties (SED) included constrained bridge crossings requiring Horizontal Directional Drilling (HDD) beneath roads
  • Potential for flooding due to the river’s tidal nature necessitated placing the pipe bridge above the bridge soffit and within the protection of the Thames Estuary flood defences. Polytetrafluoroethylene (PTFE) sliding bearings and expansion joints were used to accommodate thermal and structural movement without compromising flood resilience

10.6km

cable route

132kV

Electrical supply system

160mm to 89mm

Ducts

 

 

specialisms used

  • Installation
  • Commissioning of high-voltage
  • Bridge crossings
  • HDD (Horizontal Directional Drilling)
  • Diamond coring
“This project brought together complex engineering and environmental considerations in a highly constrained location. Through detailed planning and close coordination, we were able to deliver a compliant and resilient 132kV connection while minimising disruption and ensuring long-term reliability.“
Macc Flynn
Client Project lead

FROM CONCEPT

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Market segment: Network operator
Voltage: 132kV
Duration: 56 days

Redundant 132kV oiled filled cable route removal

The Network Operator required the safe removal of redundant oil filled 132kV cables from their Westcombe Park site in Deptford.

THE CHALLENGES

Urban disruption posed a challenge due to works taking place in built-up areas, alongside utility congestion from existing underground services. Cable removal introduced additional risks during execution, while potential surface impact required careful management to minimise damage and disruption.

WHAT WE DELIVERED

  • Two joint bays and 460m of a 132kV circuit were removed and new usable 160mm SDR11 duct was installed
  • NICE (Non-Intrusive Cable Extraction) method was employed which enabled safe, trenchless extraction

132kv

Oil filled cable route

2

Joint Bays 

460m

Circuit removed

specialisms used

  • Cable removal
  • Joint bays
  • NICE method
  • No-dig
  • Duct installation
  • Trail holes
  • Traffic management
  • Reinstatement
“On a constrained urban project like Westcombe Park, the NICE method allowed us to safely remove the redundant 132kV cable with minimal excavation and disruption. It’s exactly the kind of scenario the technique was developed for, reducing risk while maintaining programme and efficiency.“
John Fitzgerald
Senior Operations Manager

FROM CONCEPT

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TO CONNECTION

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Value: Multi Million
Voltage: 132kV
Duration: 36 months

132kV Data Centre Connection

The client required the delivery of a 6.5km civil infrastructure route, primarily within public highways, as part of a 60MVA 132kV Data Centre connection in Hemel Hempstead, Hertfordshire.

THE CHALLENGES

Construction couldn’t be completed in one phase due to early commissioning requirements, so works were staggered and required complex sequencing from temporary to permanent systems. The project involved specialist 132kV equipment and precise coordination with existing infrastructure, alongside significant site constraints including water ingress, depth limits, pipeline crossings, and a congested industrial route.

WHAT WE DELIVERED

  • JSM constructed a dedicated 11kV substation, a 132kV dual transformer bund area, and an iDNO-adoptable 132kV switchgear compound
  • Temporary power was required during substation works, resulting in 1.6km of 11kV cables being installed. This prevented delays to the client’s energisation requirements
  • The Special Engineering Difficulties included bypassing a bridge. Horizontal Directional Drilling (HDD) was used to ensure no disruption to traffic

6.5km

CIVIL INFRASTRUCTURE ROUTE

132kV

DATA CENTRE CONNECTION

60

MVA

specialisms used

  • Principal Designer
  • Principal Contractor
  • Project management
  • Cables and Duct installation
  • HV/EHV Plant installation
  • Comissioning
  • On Load testing/Energisation
“Delivering this project required exceptional coordination and adaptability from our team. From phased construction and complex sequencing to navigating challenging ground conditions and critical infrastructure crossings, we worked closely with all stakeholders to safely deliver a resilient, high-capacity connection within demanding time constraints. “
Martyn Crocker
Operations Director