From the substratum to the substation a central …...From the substratum…constructing a cable tunnel Key facts about the variety of tunnels in London: • London’s tunnel infrastructure

From the substratum to the substation –

a central London substation upgrade Ian Cox – London Programme Manager

2011. UK Power Networks. All rights reserved

End Customers

Millions

Service Area

km²

Underground

Network km

Overhead

Network km

Energy Distributed

TWh

Peak Demand

MW

New Connections

UK Power Networks overview

8.1

29,165

138,000

46,000

16,229

100,000

86.4

2


Location of primary substations in London

Leicester

Square


EHV network structure from 22kV to 132kV


From the substratum to the substation –

A central London substation upgrade

• Scheme approval:

–Substation

–Cable route (open cut and or cable tunnel)

• Detailed design development

• Legal considerations and approvals

• Supply chain appointment

• Delivery and commissioning phase

• Project completion and handover to Network

Operations

Progamme Key Milestones

From the substratum…constructing a

cable tunnel

Key facts about the variety of tunnels in London:

• London’s tunnel infrastructure dates back 150 years

• Some tunnels are subject to the Official Secrets Act

• The pace of development in London has resulted in

even more complex and deeper tunnel construction,

for example Crossrail

• The clay on which London sits makes it an ideal

substratum in which to construct tunnels

• Where practical UK Power Networks design our

tunnel routes to follow the main roads at ground level

(this is to reduce the number of consents required)


Typical cable tunnel route in central London (currently under construction)

O2 Arena

Existing Grid Supply Point

Existing substation

New substation (under construction)

Tower

Bridge

New cable

tunnel (under construction)


Key facts about the tunnel

River Thames

Existing GSP

Intermediate shaft

Total length of 6.5km with 2.85m diameter tunnel

Jubilee Line

• Tunnel boring machine is 30m long and weighs 50 tons

• 3x30m deep, 7.4m diameter shafts provide permanent access

• Machine burrows at a speed of 50m per week

• It will contain 23km of 132kV cables

• Miners reach the cutting face by train, taking around 25 mins

• Extra space in the tunnels for future cable capacity

• 6,000 concrete rings will line the interior of the tunnel

• 5,000 brackets installed to support the cables on the tunnel

walls


Some of the challenges….

Liverpool St train

station

Central line

Distance of

1.80M

Distance of

6.50M


TBM being lowered

down the shaft

Tunnel under

construction

Breakthrough

at a shaft

View from the

front of the TBM

Tunnel extension being created

inside an existing substation

Typical cable tunnel fit out with

steel brackets

Construction stage photographs

To the substation – constructing a

central London primary substation

Typical construction of a central London primary substation:

• Two to three storey basements connected to tunnel

shaft creating confined space challenges.

• Reduced footprint to incorporate the above ground

two storey building with mezzanine floors.

• Brown field development or incorporated into a

‘developers’ commercial high rise.

• Piled foundations, steel structures with cladding or

traditional brick finish.

• Stakeholder influence, heritage sites, customer

requirements.

To the substation – constructing a

central London primary substation

Typical assets being installed:

• 3x132/11/11kV 66MVA transformers complete with

cooling system

• 12 -15 no. sections of 132kV Gas Insulated

Switchgear

• 50 – 80 no. panels of 11kV switchgear

• Kilometres of 11kV and 132kV cable

• Batteries and telecontrols systems

• Secondary network distribution transformers


Some history to the sites:

• Some substations are built on former power

stations, with some dating back to the 1900’s

and other on more prominent sites such as

Bankside (Tate Modern Gallery)

• The network has to be able to cope with the

increasing demands and changing skyline of

London

London in the 1900’s

London one hundred years later


The challenges of working in London….

• In 2013 over seven consecutive weekends the UK

Power Networks Capital Programme team delivered

7x 132kV transformers into central London.

• This required numerous consent and co-ordination

with Transport for London, Thameslink, borough

councils and the Police.

• The following short video provides a brief insight into

the construction of some of our substations,

including delivery of the transformers through central

London.


What next for London’s electrical network?

• Identifying growth hotspots and areas of existing network that

require strategic infrastructure investment.

• Working with key stakeholders to consider the potential for

decentralised energy systems to reduce electricity distribution

infrastructure costs.

• Continued innovation both in technology and collaboration with

the supply chain and our customers.

• Increasing shared land use with prominent developers in key

central locations.

• Continuation of stay safe culture to achieve a target of zero

harm.

• To be recognised as setting the standard for construction of

major city electrical infrastructure.


And why do they say London is different?

The size of the investment and

the outputs achieved is

equivalent to delivering the

primary network required for

London 2012 Olympics every

year!

Documents

From the substratum to the substation a central …...From the substratum…constructing a cable tunnel Key facts about the variety of tunnels in London: • London’s tunnel infrastructure