7/28/2019 400kV Overhead Line Construction

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400kV Overhead Line Construction

Tim Inglehearn

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Contents

Overhead line components

Typical tower types

Overhead line construction

Reinstatement

Inspection and maintenance

Substations

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Overhead Line Components

Support

Conductors

Insulators

Spacers

Dampers

Earth wire

Jumpers (on tension

towers)

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Typical Tower Types

Suspension TowerTension Tower

(angled or deviation towers)

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Typical Tower Types

Termination Tower at aSealing End Compound or Substation

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Typical Tower Types

Short support: lower height;more supports per kilometre

Tall support: greater height;

fewer supports Clearance and ‘sag’; higher

voltages require greaterclearance/increased insulation

Sum of adjacent ‘spans’

Typical tower height: around50m

Typical tower span: 360m

Span Lengths and Tower Heights

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Overhead Line Construction

Temporary metal trackways orstone tracks dependent onlandowners requirements

Localised vegetation clearanceand excavation where towerfoundations needed, minor soilstorage as a result

Drainage/dewatering works

might be required depending onground conditions/watertable

Every tower requires its ownworking area – protected by

temporary Heras fencing

Access, Working Areas and Ground Preparation

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Overhead Line Construction

Excavator for foundations andany drainage works

Delivery of materials to site

Crane to assemble towers

Winch and tensioner

Machinery Required

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Overhead Line Construction

Tower Foundations –Excavated or Piled

Foundation type dependenton ground conditions

Excavated foundationsencased in mass concrete

Piled foundations also useconcrete

Stub legs installed andremainder of tower built up bycrane

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Overhead Line Construction

Fabricated from rolled steelangles and delivered to site innumbered parts (similar to flat-pack furniture)

Most parts are bolted together

Sections e.g. crossarmsassembled at ground leveland raised into position usinga crane

All steelwork is galvanised forprotection (will last approx. 20years)

Installation of insulators and

fittings

Tower Construction and Cranage

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Draw wires winched through

Conductors are winched intoposition

Conductors pulled throughsuspension towers

Winch and tensioner placed

at tension towers

Additional fittings (spacersetc.) installed

Overhead Line Construction

Stringing conductors

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Reinstatement

At end of construction, temporaryaccess tracks and working areas areremoved (unless otherwise agreedwith the landowner)

Land returned to original condition

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Inspection and Maintenance

Inspection is carried out everyyear

Towers are repainted approx.every 18 years depending oncondition

Replacement fittings duringroutine inspection, if required

Reconductoring takes place

approx. every 40 years

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Substations

Transform voltages (400/132 kV)

Switch connections in and out ofthe network

Manage power flows

Connection points

Switches, transformers,compensation equipment

Permanent land-take and vehicle

access required Transformers delivered as

abnormal loads - existing roadsmay need widening etc.

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Any Questions?