Network Standard
: NW000-S0006
Document No
Amendment No : 1
: Chief Engineer
Approved By
NETWORK
: 25/06/2015
Approval Date
: 25/06/2018
Review Date
(Supersedes Network Standard (Network) NW000-S0006. Amendment No.0)
NW000-S0006
NW000-S0006
NS168 SPECIFICATION FOR THE DESIGN AND CONSTRUCTION OF
33KV, 66KV AND 132KV UNDERGROUND CABLES
UNCONTROLLED IF PRINTED
Page 1 of 33
NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
ISSUE
For issue to all Ausgrid and Accredited Service Providers’ staff involved with the design and construction of 33kV, 66kV and
132kV underground cables forming part of Ausgrid’s network, and is for reference by field, technical and engineering staff.
Ausgrid maintains a copy of this and other Network Standards together with updates and amendments on www.ausgrid.com.au.
Where this standard is issued as a controlled document replacing an earlier edition, remove and destroy the superseded
document
DISCLAIMER
As Ausgrid’s standards are subject to ongoing review, the information contained in this document may be amended by Ausgrid
at any time. It is possible that conflict may exist between standard documents. In this event, the most recent standard shall
prevail.
This document has been developed using information available from field and other sources and is suitable for most situations
encountered in Ausgrid. Particular conditions, projects or localities may require special or different practices. It is the
responsibility of the local manager, supervisor, assured quality contractor and the individuals involved to make sure that a safe
system of work is employed and that statutory requirements are met.
Ausgrid disclaims any and all liability to any person or persons for any procedure, process or any other thing done or not done,
as a result of this Standard.
All design work, and the associated supply of materials and equipment, must be undertaken in accordance with and
consideration of relevant legislative and regulatory requirements, latest revision of Ausgrid’s Network Standards and
specifications and Australian Standards. Designs submitted shall be declared as fit for purpose. Where the designer wishes to
include a variation to a network standard or an alternative material or equipment to that currently approved the designer must
obtain authorisation from the Network Standard owner before incorporating a variation to a Network Standard in a design.
External designers including those authorised as Accredited Service Providers will seek approval through the approved process
as outlined in NS181 Approval of Materials and Equipment and Network Standard Variations. Seeking approval will ensure
Network Standards are appropriately updated and that a consistent interpretation of the legislative framework is employed.
Notes: 1. Compliance with this Network Standard does not automatically satisfy the requirements of a Designer Safety Report.
The designer must comply with the provisions of the Workplace Health and Safety Regulation 2011 (NSW - Part 6.2 Duties of
designer of structure and person who commissions construction work) which requires the designer to provide a written safety
report to the person who commissioned the design. This report must be provided to Ausgrid in all instances, including where the
design was commissioned by or on behalf of a person who proposes to connect premises to Ausgrid’s network, and will form
part of the Designer Safety Report which must also be presented to Ausgrid. Further information is provided in Network
Standard (NS) 212 Integrated Support Requirements for Ausgrid Network Assets.
2. Where the procedural requirements of this document conflict with contestable project procedures, the contestable project
procedures shall take precedent for the whole project or part thereof which is classified as contestable. Any external contact with
Ausgrid for contestable works projects is to be made via the Ausgrid officer responsible for facilitating the contestable project.
The Contestable Ausgrid officer will liaise with Ausgrid internal departments and specialists as necessary to fulfil the
requirements of this standard. All other technical aspects of this document which are not procedural in nature shall apply to
contestable works projects.
INTERPRETATION
In the event that any user of this Standard considers that any of its provisions is uncertain, ambiguous or otherwise in need of
interpretation, the user should request Ausgrid to clarify the provision. Ausgrid’s interpretation shall then apply as though it was
included in the Standard, and is final and binding. No correspondence will be entered into with any person disputing the
meaning of the provision published in the Standard or the accuracy of Ausgrid’s interpretation.
KEYPOINTS
This standard has a summary of content labelled “KEYPOINTS FOR THIS STANDARD”. The inclusion or omission of items in
this summary does not signify any specific importance or criticality to the items described. It is meant to simply provide the
reader with a quick assessment of some of the major issues addressed by the standard. To fully appreciate the content and the
requirements of the standard it must be read in its entirety.
AMENDMENTS TO THIS STANDARD
Where there are changes to this standard from the previously approved version, any previous shading is removed and the newly
affected paragraphs are shaded with a grey background. Where the document changes exceed 25% of the document content,
any grey background in the document is to be removed and the following words should be shown below the title block on the
right hand side of the page in bold and italic, for example, Supersedes – document details (for example, “Supersedes Document
Type (Category) Document No. Amendment No.”).
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KEY POINTS OF THIS STANDARD
Scope
General Design
Specific Design
This Network Standard specifies the
requirements for the design and
construction of 33kV, 66kV and 132kV
underground cables for use on the Ausgrid
network. It is limited to scope identified
below and provides controls for associated
risks as listed below:
This network standard includes the
following design requirements:



Applies to both new and existing
works.
Ausgrid will determine if the work is
contestable and will prepare a
development brief defining the scope
of the project and any project specific
requirements.






The Proponent is responsible for the
design, supply of materials, obtaining
approvals, and construction of the
underground sub-transmission line as
detailed in5.0.
Details of Ausgrid’s Development Brief
are outlined.
Route selection including major
crossings, private land and
contaminated land.
Approvals & environmental impact
assessment.
Route surveys required before
commencing design.
Easement requirements outlined in9.1.
Electrical design requirements are
detailed in Section 10
Materials and equipment requirements
together with details of documentation
requirements include:


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
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
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Detailed requirements for cable types,
use of cable types, joints, terminations,
link boxes, pits and vaults.
Sheath bonding & earthing.
Use of sheath voltage limiters
Requirements for the installation of
route markers.
Design details of joint bays, pits and
vaults.
The design details of UGOH poles
Trenching details including details of
the depth of cables, major road
crossings, location and design of
joints, and separation from other
services and cables.
Bedding and backfill requirements.
Conduits and conduit accessories.
Construction
The Proponent is required to carry out all
construction work in accordance with the
relevant legislation, Ausgrid standards,
Codes and agreements. Specific
requirements covered include:




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

Special precautions to be taken when
working with existing underground
cables due to prior use of oil, PCB,
OCP & asbestos and the possible
presence of energised cables.
Use of roadplates.
Conduit cleaning & mandrel tests.
Cable pulling.
Security.
Precautions against water damage.
As-built Operations & Maintenance
Manual.
Where to for more information?
Where to for more information?
Where to for more information?
Sections 5-10
Section 10
Sections 11 & 12
Where to for more information?
Tools and Forms
Tools and Forms
Tools and Forms
Section 1, 2, 3 & 4
None provided.
None provided.
Annexure A Sample Compliance Checklist
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
Network Standard
NS168
Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Contents
1.0
PURPOSE ............................................................................................................................................. 6
2.0
SCOPE .................................................................................................................................................. 6
3.0
REFERENCES ...................................................................................................................................... 6
3.1
General ...................................................................................................................................... 6
3.2
Ausgrid documents .................................................................................................................... 6
3.3
Other standards and documents................................................................................................ 7
3.4
Acts and regulations................................................................................................................... 7
4.0
DEFINITIONS ........................................................................................................................................ 7
5.0
RESPONSIBILITIES .............................................................................................................................. 9
6.0
DEVELOPMENT BRIEF ...................................................................................................................... 10
7.0
DESIGN DOCUMENTATION .............................................................................................................. 10
8.0
SURVEY .............................................................................................................................................. 11
9.0
ROUTE SELECTION ........................................................................................................................... 11
9.1
Easements ............................................................................................................................... 12
9.2
Substations .............................................................................................................................. 12
10.0
ELECTRICAL DESIGN ........................................................................................................................ 13
10.1 General .................................................................................................................................... 13
10.2 Cable types .............................................................................................................................. 13
10.3 Accessories (joints and terminations) ...................................................................................... 13
10.4 Link boxes ................................................................................................................................ 13
10.5 Sheath voltage limiters ............................................................................................................. 14
10.6 Thermal rating .......................................................................................................................... 14
10.6.1 General .......................................................................................................................... 14
10.6.2 Distributed temperature sensing (DTS) ......................................................................... 15
10.7 Trench cross-section ................................................................................................................ 17
10.8 Depth of cables/conduits .......................................................................................................... 17
10.9 Trench design .......................................................................................................................... 17
10.10 Conduits ................................................................................................................................... 19
10.11 Separation from other services and cables ............................................................................. 19
10.12 Bonding and earthing ............................................................................................................... 20
10.12.1 General ........................................................................................................................ 20
10.12.2 Single point bonding .................................................................................................... 20
10.12.3 Full cross bonding ...................................................................................................... 21
10.12.4 Looping existing circuits into new substations ............................................................ 22
10.12.5 Bonding connections at GIS terminations ................................................................... 23
10.13 Joint bays and vaults................................................................................................................ 23
10.13.1 Joint bay location ......................................................................................................... 23
10.13.2 Joint bays for 33kV cables .......................................................................................... 23
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
10.13.3 Joint bays for 132kV & 66kV cables ............................................................................ 23
10.13.4 Support of cables & joints............................................................................................ 24
10.13.5 Joint bay backfilling .................................................................................................... 24
10.14 Underground to overhead structures (UGOHs) ....................................................................... 24
10.15 Route markers.......................................................................................................................... 26
10.16 Telecommunications ................................................................................................................ 27
11.0
CONSTRUCTION ................................................................................................................................ 28
11.1 Hazards from existing underground cables ............................................................................. 28
11.1.1 Oil
............................................................................................................................. 28
11.1.2 PCB ............................................................................................................................. 28
11.1.3 OCP ............................................................................................................................. 28
11.1.4 Asbestos ........................................................................................................................ 28
11.1.5 Energised cables ........................................................................................................... 28
11.2 Hazards from contaminated land ............................................................................................. 28
11.3 Installation precautions ............................................................................................................ 28
12.0
FINAL PROJECT DOCUMENTATION ................................................................................................ 30
13.0
RECORDKEEPING ............................................................................................................................. 30
14.0
AUTHORITIES AND RESPONSIBILITIES .......................................................................................... 30
15.0
DOCUMENT CONTROL...................................................................................................................... 31
ANNEXURE A – SAMPLE COMPLIANCE CHECKLIST ................................................................................ 32
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
1.0 PURPOSE
Network Standard NS168 specifies the requirements for the design and construction of 33kV, 66kV
and 132kV underground cables for use on the Ausgrid network.
2.0 SCOPE
This Network Standard provides technical information in relation to Ausgrid’s requirements for the
installation of underground sub-transmission lines and modifications to existing underground subtransmission lines. In addition, work under this Standard is to be carried out subject to and in
accordance with any plans, drawings and documents that may be provided as part of the
Development Brief.
Other Network Standards relevant to this work, which must also be complied with are referenced in
Section 3.
This Network Standard does not cover construction requirements, authority approvals, safety or
environmental requirements relating to construction works. Normal industry practices apply in
addition to any Ausgrid design requirements detailed herein.
Ausgrid shall determine the need for any new or modified lines, and whether the work is
contestable, and shall prepare a Development Brief (see Note) document, defining the scope of the
project and detailing specific information relevant to the project.
Note:
In the case of contestable work, the Development Brief is the ‘Design Information’, as
defined by IPART.
3.0 REFERENCES
3.1
General
All work covered in this document shall conform to all relevant Legislation, Standards, Codes of
Practice and Network Standards. Current Network Standards are available on Ausgrid’s Internet
site at www.ausgrid.com.au.
3.2
Ausgrid documents
 All Ausgrid drawings referenced in this Network Standard and/or issued with the Development
Brief and detailed design.
 Be Safe Management System
 Bushfire Risk Management Plan
 Company Form (Governance) - Network Document Endorsement and Approval
 Company Procedure (Governance) - Network Document Endorsement and Approval
 Company Procedure (Network) - Production / Review of Network Standards
 Electrical Safety Rules
 Electricity Network Safety Management System Manual
 NEGSM04.11 Specification for the Design and Construction of Major Substations -Power
Cables
 NS100 Field Recording of Network Assets
 NS130 Specification for Laying Underground Cables up to and including 11kV
 NS143 Easements, Leases and Rights of Way
 NS156 Working Near or Around Underground Cables
 NS161 Specification for Testing of Underground Cables
 NS165 Safety Requirements for Non-Electrical Work in and around Live Substations
 NS172 Design Requirements for Cable Jointing Pits and Vaults
 NS174 Environmental Procedures
 NS174 Supplementary Notes:
 NS174A EIA Worksheet
 NS174B EIA Guidelines & EGN174B EIA worksheet guidance notes
 NS174C Environmental Handbook for Construction & Maintenance
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
 NS181 Approval of Materials and Equipment and Network Standard Variations
NSA1343 Supplement to NS181 - Approval of Materials and Equipment and Network
Standard Variations: List of Approved Materials and Equipment
 NS203 Telecommunications Network : Master Policy document
 NS205 Telecommunications Route Markers
 NS204.2.1 Communication Pits - Specifications and Installation Guidelines
 NS212 Integrated Support Requirements for Ausgrid Network Assets
 NS234 Telecommunications - Underground Physical Plant Installation
 NS260 Sub-Transmission Feeder Earthing Design
 NS261 Requirement for Design Compliance Framework for Network Standards
3.3
Other standards and documents
 AS1429.1 Polymeric Insulated cable for working voltages above 1.9/3.3(3.6)kV and up to and
including 19/33 (36kV)
 AS1429.2 Polymeric Insulated cable for working voltages above 19/33(36) kV and up to and
including 76/132 (145)kV
 AS2053.2 Conduits and fittings for electrical installations
 AS4805.1 Accessories for Electric Cables Test Requirements Part 1: Power cables with
extruded insulation for rated voltages from 1.9/3.3 (3.6) kV up to and including 19/33 (36) kV.
 AS/NZS1477 Unplasticised PVC (uPVC) Pipes and Fittings for Pressure Applications
 AS/NZS60840 Power Cables with Extruded Insulation and their Accessories for Rated Voltages
Above 30kV (Um = 36kV) up to 150kV (Um = 170kV) – Test Methods and Requirements.
 EA ER C55/4 -Electricity Association Engineering Recommendation - Insulated Sheath Power
Cable Systems.
 IEC 60287 Calculation of the continuous current rating of cables (100%) load factor.
 IEC 60502 Extruded solid dielectric insulated power cables for rated voltages from 1kV up to
30kV.
 IEC 60986 Short circuit temperature limits of electric cables with rated voltages from.6kV (Um =
7.2kV) up to 30kV (Um = 36kV).
3.4
Acts and regulations

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

Electricity Supply (General) Regulation 2014 (NSW)
Electricity Supply (Safety and Network Management) Regulation 2014
Environmental Planning and Assessment Act 1979
State Environmental Planning Policy (SEPP) Infrastructure 2007
The Roads Act 1993, as amended.
Work Health and Safety Act 2011 and Regulation 2011
4.0 DEFINITIONS
Accredited
Designer
A person accredited as a Level 3 ASP (ASP/3) to design the Works, in
accordance with the 'Scheme for the Accreditation of Service Providers to
Undertake Contestable Works' published by the former Electricity
Association of New South Wales in accordance with the Electricity Supply
(Safety and Network Management) Regulation 2014 and administered by
NSW Government Trade & Investment.
Note: Ausgrid is an ASP/3; refer to the NSW Government Trade &
Investment website for the contact details of all ASP/3s.
For work on the sub-transmission system, the Accredited Designer must
demonstrate training and recent experience in design work at the relevant
voltage.
Accredited
Service Provider
A person accredited as a Level 1 ASP (ASP/1) or as an Accredited Designer,
in accordance with the 'Scheme for the Accreditation of Service Providers to
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
(ASP)
Amendment No 1
Undertake Contestable Works' published by the former Electricity
Association of New South Wales in accordance with the Electricity Supply
(Safety and Network Management) Regulation 2014 and administered by
NSW Government Trade & Investment.
Note: Ausgrid is an ASP/1; refer to the NSW Government Trade &
Investment. website for the contact details of all ASP/1s.
For work on the sub-transmission system, the Accredited Service Provider
must demonstrate training and recent experience at the relevant voltage, in
all aspects of the work they will undertake.
Backfill
Material used to fill the trench and encapsulate the cables & conduits.
Business
Management
System (BMS)
An Ausgrid internal integrated policy and procedure framework that contains
the approved version of documents.
Classified
(Roads)
“Classified” roads are as defined in the Roads Act and can mean any of the
following:
(a) a main road,
(b) a highway,
(c) a freeway,
(d) a controlled access road,
(e) a secondary road,
(f) a tourist road,
(g) a tollway,
(g1) a transitway,
(h) a State work.
In addition, Classified roads fall within two main administrative classes being
“State” roads and “Regional” roads. The RMS maintains a schedule of
Classified roads, State roads and Regional roads.
Compliance
Officer
Ausgrid officer responsible for dealings with parties involved in construction
of Ausgrid network assets. For contestable works this would normally be the
ASP Compliance Officer.
Contestable
Works
Those works for which the Customer is required to meet the cost and for
which the Customer may choose the ASP under section 31 of the Electricity
Supply Act (NSW) 1995. This also includes contestable asset relocation
works
Customer
A customer is an individual or an entity that is an end-user of electricity.
Document
control
Ausgrid employees who work with printed copies of document must check
the BMS regularly to monitor version control. Documents are considered
“UNCONTROLLED IF PRINTED”, as indicated in the footer.
DTS
Distributed Temperature Sensing (fibre)
Development
Brief
A document issued by Ausgrid that defines the scope of the project and
details specific relevant information. In the case of contestable work, the
Development Brief is the ‘Design Information’, as defined by IPART.
ECC
Earth Continuity Conductor
Joint Bay
An enlarged section of excavated trench, in which cables are jointed, and
which is backfilled at the completion of the jointing work
Joint Pit or Vault
Underground enclosures constructed of brick or concrete in which cables are
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
jointed. Pits & vaults are enterable by personnel via a hatch or door.
Network
Standard
A document, including Network Planning Standards, that describes the
Company's minimum requirements for planning, design, construction,
maintenance, technical specification, environmental, property and metering
activities on the distribution and transmission network. These documents are
stored in the Network Category of the BMS repository.
OCP
Organo-chlorine pesticides – persistent bio-accumulative pesticides including
aldrin and dieldrin.
Project Officer
Ausgrid officer responsible for coordinating parties involved in the design of
Ausgrid network assets. For contestable works this would normally be the
Major Connections Project Officer.
Proponent
In this document:

For contestable construction of Ausgrid assets, the Proponent is an
individual or entity who requires the construction of a project. A
Proponent could be a developer or customer and includes Accredited
Designer(s) and Accredited Service Provider(s) working under
agreements/contractual arrangements for the Proponent. For contestable
works, the Proponent is not Ausgrid.

For non-contestable construction of Ausgrid assets, Ausgrid is the
Proponent. Any reference to the Proponent includes contractors working
under agreements/contractual arrangements for Ausgrid.
Review date
The review date displayed in the header of the document is the future date
for review of a document. The default period is three years from the date of
approval. However a review may be mandated at any time where a need is
identified due to changes in legislation, organisational changes, restructures,
occurrence of an incident or changes in technology or work practice.
SVL
Sheath Voltage Limiter
TR
Thermal Resistivity
TSB
Thermally Stable Backfill
Underground sub- An underground cable which is designed for use at 33,000, 66,000 or 132,000
transmission line Volts. It includes sub-transmission voltage cables used for distribution
purposes.
5.0
RESPONSIBILITIES
The Proponent is responsible for the design, supply of materials and construction of the
underground sub-transmission line, providing any necessary approvals and easements, and
providing an assessment of the environmental impacts of the proposed line in accordance with the
requirements of the Environmental Planning and Assessment Act 1979 and NS174.
The design, environmental impact assessment, construction environmental management plan and
quality documentation shall be submitted to the Project Officer for Ausgrid review – typically 4 to 6
weeks will be required for review of each document, or as nominated in relevant
agreements/contractual arrangements.
Once the design has been accepted by Ausgrid, the Compliance Officer will attend site to ensure
that Ausgrid is satisfied that construction works are being carried out to the required standard,
including witnessing of tests, hold-points etc.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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6.0
Amendment No 1
DEVELOPMENT BRIEF
Ausgrid will prepare the Development Brief for each new section of sub-transmission line project. It
may include the following information:




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





7.0
Project scope and description.
Required completion date, if applicable to satisfy system loading requirements.
Operating voltage.
Rating requirements, including provision for other circuits in close proximity.
Proposed route or endpoints.
Environmental GIS report.
Details of power cables, including any requirements for compatibility with existing cable
installations, e.g. extensions to oil-filled cables.
Details of communication cables, including any requirements for interfacing with existing
systems.
Any project-specific design or construction requirements/constraints.
Segregation requirements for multiple circuits along a common route.
Allowance for additional circuits, or conduits, if applicable.
DESIGN DOCUMENTATION
The Proponent shall provide a design and all details in accordance with NS104 Network Project
Design Plans and the Development Brief including but not limited to the following:
Route plan
A route plan shall be provided showing the cable route on a cadastre plan, including dimensions
from property boundaries if required for EMF calculations, the location of joint bays, pulling pits, link
boxes and communications/DTS pits and existing services.
Property schedule
Where easements are to be acquired or land purchased, a property schedule shall be prepared,
giving details of the Lot and DP numbers (and street addresses where known) of all properties
affected, name, postal address and contact phone number of property owners, and comments on
the nature of the interest to be obtained and any agreements made with the property owner, such
as access conditions, disposal of vegetation removed during line construction, etc.
Schematic
A schematic shall be provided showing feeder numbers, cable sections, joint bays, section lengths,
cable types, accessory types and sheath bonding arrangements
Design calculations
Design calculations shall include thermal ratings, short-circuit fault ratings, sheath voltage /
currents and tension / sidewall pressure during pulling for all cables.
Cable details
Cable details shall include cross-section, dimensions, materials, thermal & electrical properties.
Cable accessory details
This shall include manufacturers’ drawings and jointing instructions.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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Amendment No 1
Factory test plan
This shall include test specification references and pass criteria for all sample and routine tests
carried out in the factory on all cables and accessories.
Trench construction
This shall include trench cross-sections, backfill and reinstatement details.
Joint bay general arrangement
This shall include internal and external dimensions, location of joints, support details for cables &
joints, bonding lead conduits, link boxes and earthing details.
Native soil details
This shall include results of soil sampling, geotechnical, earth resistivity and thermal resistivity
testing.
Refer also to NS212 Integrated Support Requirements for Ausgrid Network Assets for additional
information on technical information to be provided with projects including documentation, spares
and training required for new network assets.
8.0
SURVEY
A route survey should be carried out before commencing any design work, this should include the
following minimum information –
 Cadastre.
 Combined services information, eg from “Dial Before You Dig” search.
 Property ownership, eg DP/strata “F Plan” to identify any areas that are not gazetted as road
reserve.
 Vertical profile if significant gradients are encountered that would adversely affect cable pulling
tensions.
Borehole samples will need to be taken from the preferred route for the purposes of –
 Thermal resistivity (TR) sampling at preferred intervals of 200m, or at changes in soil type, for
rating calculations.
 Road pavement make-up, details of layer materials and thickness, for road restoration
purposes.
 Characterisation of soil layers and environmental testing, for work method planning and waste
classification.
Trial holes may need to be excavated at survey stage to gain details of known obstructions /
pinchpoints that may affect route viability.
9.0
ROUTE SELECTION
The optimum route shall be selected, based on an assessment of the following factors :







Cost (usually minimised by selection of the shortest practical route).
Availability of suitable joint bay locations.
Major crossings (eg rail, water, major roads or other infrastructure).
Community disruption (eg traffic, nightworks, location & number of impacted stakeholders).
EMF prudent avoidance.
Environmental issues (eg ecology, heritage etc)
Easements.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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
Amendment No 1
Specific site issues (eg contamination, poor soil properties etc).
Community consultation.
Construction timeframe.
Existing services.
Risks to cost and program.
Where multiple options exist, an options analysis shall be undertaken in accordance with the
Project Development Manual.
9.1
Easements
Where possible, cable routes shall follow existing roads, and be contained within the carriageway
of the road reserve.
Where considerable savings or other advantages may be obtained by traversing private property or
other land not dedicated as public road, an easement shall be obtained to guarantee Ausgrid's
security of tenure over the route. The easement shall be negotiated and acquired in accordance
with the requirements of NS143 Easements, Leases and Rights of Way, using Ausgrid’s standard
terms and conditions. Easement widths shall normally be as specified in NS143, or in any
supporting documentation prepared justifying the need for departure from these standards. All
easements must comply with Ausgrid’s standard Deeds of Agreement for Easements.
Before any work commences on private property, the Proponent shall obtain written permission to
enter from the land owners, and shall obtain agreement from the land owners for the planned route
and dimensions of the proposed easement. The easement shall be finalised as soon as possible
after completion of the works, and shall be in accordance with an ‘as built’ survey which clearly
indicates the location of the new construction works and the agreed easement boundaries on the
private property.
Where, because of the route selected, the cable easement is not appropriate for vehicle access for
maintenance or repairs, a Right of Way should be established at the same time, to ensure ongoing
access for Ausgrid staff and contractors. Refer to NS143 for details of establishing a suitable Right
of Way. Also refer also to Section 8.2 Access Tracks.
Where the route traverses a rail corridor, approval for the crossing must be obtained from the
appropriate Rail authority – either RailCorp or Australian Rail Track Corporation (ARTC). The
Proponent is responsible for obtaining approval for the design of the crossing from the appropriate
Rail authority in accordance with the requirements of the relevant Master Access Deed (MAD).
Where the route follows a classified road, the provisions of the Memorandum of Understanding
between Ausgrid, RTA & Dept of Transport will apply.
9.2
Substations
Activities within substation yards are strictly controlled and only undertaken by authorised
personnel in accordance with defined procedures (e.g. NS156 Working Near or Around
Underground Cables and NS165 Safety Requirements for Non-Electrical Work in and around Live
Substations).
Cables and conduits should be installed within substations as per the requirements of NEG
SM04.11 Specification for the Design and Construction of Major Substations - Power Cables and
NEG SM04.27 Specification for the Design and Construction of Major Substations - Power Cable
Conduits.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
10.0 ELECTRICAL DESIGN
10.1
General
Unless prior written approval is received from Ausgrid, all materials used must be new and in
accordance with Ausgrid’s specifications.
Where the Proponent wishes to use materials not supplied or already approved by Ausgrid, they
must submit details in accordance with the requirements of NS181 Approval of Materials and
Equipment and Network Standard Variations. Materials approved by Ausgrid under this process
are listed in the regularly updated NSA 1343.
10.2
Cable types
New cable installations shall use cables with copper conductor and XLPE insulation.
The cable sheath type shall be selected as follows :
 132kV & 66kV – corrugated aluminium sheath cables shall be used in all applications apart from
dry environments such as substation basements, eg 132kV transformer tails, where polylam
cables can be used.
 33kV - polylam cables shall be used in all applications.
Special cases where different cable types should be considered –
 Major tunnels, eg where frequent personnel access is needed, or the risks of fire and multiple
cable failures are unacceptable - cables shall include an extra layer of low smoke zero halogen
material to retard the spread of fire and smoke.
 Submarine cables, eg marine environments where cables are direct-buried or contained in long
HDD bores where it may be impossible to easily replace the cable in future - lead sheath and
steel wire armouring should be considered to maximise service life.
 Contaminated/corrosive/swampy ground - lead sheath should be considered to maximise
service life.
10.3
Accessories (joints and terminations)
Cable accessories shall be compatible with the cables being used.
10.4
Link boxes
Link boxes shall be fabricated from stainless steel, and shall be watertight and explosion proof to
the likely level of pressure that could be developed by an internal flashover or SVL failure.
Along the cable route, the link boxes are to be installed in suitable concrete link box pits located in
the footpath/nature strip adjacent to the cable jointing bay/pit/vault. The internal depth of the link
box pit shall be 700 – 900mm to allow easy maintenance. The internal width of the link box pit shall
allow a minimum clearance distance of 200mm from the link box on the side of the bonding lead
entries and 150mm on the other sides as shown below.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
Figure 1 - min clearance between link box and link box pit
Pit access covers shall comply with the Class D watertight requirements of AS 3996. Covers shall
be type-tested in accordance with AS 3996 and test certificates made available on application. In
addition, covers shall sustain a modified type test, using the ultimate limit state design load, without
fracture. The test load shall be applied, without shock, five times, sustaining the test load and zero
load alternately for minimum periods of 30 seconds. Any resultant permanent set measured along
the unit’s long axis shall, after removal of the test load, be not greater than 0.8% of the clear
opening span.
Covers in footpaths/nature strips shall be installed to open in a safe and accessible direction, ie not
over the kerb into the road.
Covers in road carriageways shall be installed to be opened in the direction of the traffic lane (i.e.
not across the lanes), and shall open in the opposite direction to the flow of traffic.
10.5
Sheath voltage limiters
Sheath voltage limiters (SVLs) at cable terminations or bonding points shall be in accordance with
the current Ausgrid specification. The placement of SVLs shall be as specified or approved by the
group within Ausgrid responsible for underground sub-transmission mains designs.
SVLs generally have a rated discharge current of 20kA and a rated voltage of 4.5kV, 6.0kV, 7.5kV
or 9kV as appropriate.
10.6
Thermal rating
10.6.1 General
The required thermal rating and load cycle will be provided in the Development Brief. Inputs into
the rating calculations will be :
 Rating types (continuous/cyclic/both feeders in service/single feeder in service)
 Load cycle for cyclic rating
 Conductor temperature limits : 90°C for continuous & cyclic rating
 Ambient ground temperature : 25°C for summer, 18°C for winter
 Moisture content : 0% for TSB material & within 50°C isotherm, 3% for native soil
 Thermal properties of cables & conduits : supplier to provide.
Thermal ratings shall be calculated in accordance with IEC60287, and shall use the native soil TR
values found in the initial route survey.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
The maximum dimensions of the 50°C isotherm shall be calculated for the continuous & cyclic
rating scenarios for (a) both feeders in service, and (b) any single feeder in service. The trench
shall be backfilled so that the worst-case 50°C isotherm is fully filled with TSB (subject to the
minimum dimensions required by 10.9).
Backfill materials shall be tested as specified in NS130 & NS130 Annex K to ensure compliance
with TR & quality requirements.
Ausgrid shall be consulted about mutual heating effects from parallel/crossing cables.
All TR test reports for backfill and native soils shall be provided to Ausgrid in a standard Excel
spreadsheet template – Ausgrid Mains Design will provide the template on request.
10.6.2 Distributed temperature sensing (DTS)
10.6.2.1 General
Distributed Temperature Sensing (DTS) fibre is required on all new sub-transmission feeder
installations, with the possible exception of :
 Major tunnel installations where temperature measurements can be carried out more effectively
by other methods.
 Short substation routes where there is no possibility of that route being a constraint on the
feeder thermal rating.
The optical fibre bundle shall consist of at least two single mode and two multimode fibres to
Ausgrid’s current specification, although experience has shown that bundles consisting of six single
mode & six multimode fibres are stiffer and easier to blow long distances. DTS fibres will be
terminated in the control room of each substation to which the cable is connected.
The fibre route shall be designed so that the blowtube can be installed within acceptable tension
limits, and particular attention should be given to maximising bend radii where the route deviates
from the cable trench, eg to fibre pits.
The requirements of NS234 “Telecommunications Underground Physical Plant Installation” and
NS204.2.1 “Communications Pits – Specifications and Installation Guidelines” shall apply.
DTS fibre pits shall be located in the footpath wherever possible, and away from power cable
jointing bays, pits and vaults.
In substation control rooms, the DTS fibres shall be terminated in a patch panel in an AFC indoor
wall mounted enclosure, unless the substation is equipped with FDM and / or FDA panels. DTS
entering substations with FDM and / or FDA panels shall terminate the fibre in accordance with the
telecommunications brief supplied by Ausgrid’s Senior Engineer responsible for
telecommunications planning.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
10.6.2.2 Three core cables
Figure 2 - Three core cable cross-section showing blowtube
For three core cables, a single 6/8mm blowtube with outer protective MDPE & HDPE sheath shall
be installed in the fillers of the cable as per the 33kV cable specification. The blowtube provides a
space for optical fibres to be installed in the cable.
Where intermediate blowing pits are not required, the tube shall be made continuous through the
cable joints using compatible connectors. Where a blowing pit is required, the power cable joint
must provide a water tight exit for the tube, and the DTS fibre shall be mechanically protected for
the entire route from the cable joint to the pit.
The blowtube is to be extended to the substation building in each case, or jointed onto normal fibre
pilot cable at a convenient location that will not require feeder outages for future access.
10.6.2.3 Single core cables
For single core cables, a blowtube shall be installed in a separate 32mm orange conduit, generally
in the centre of a trefoil group.
As the DTS will be in a separate conduit, a fibre optic cable may be acceptable instead of a
blowtube since it can easily be replaced if the fibres degrade over time, however a large number of
splices may cause fibre loss budget difficulties with long cable routes so Ausgrid must be consulted
if a fibre optic cable is proposed.
10.6.2.4
DTS Monitoring Unit
Ausgrid will advise if a DTS monitoring unit is required, and will provide a specification in these
cases.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
10.7
Amendment No 1
Trench cross-section
Trenches shall be designed to achieve the required thermal ratings. The dimensions shall take into
consideration the cable operating voltage, cable type, and bonding arrangement.
Cables shall be installed in conduits wherever possible to minimise community impact during
construction. Direct-burial may be possible in rural areas.
10.8
Depth of cables/conduits
Classified roads
To comply with Ausgrid’s Memorandum of Understanding Between Ausgrid and Roads and Traffic
Authority of NSW (now NSW Roads and Maritime Services (RMS)) and Department Of Transport
(now Transport for NSW) August 2011 cables to be installed within State roads shall generally be
designed with a minimum cover depth of 1m within the carriageway and 900mm cover outside the
carriageway (eg footpath & driveways).
Non-classified roads
In Regional and Local (non-classified) road reserves cables shall be designed with a minimum
cover depth of 750mm within both the carriageway and non-carriageway areas.
Extra protection for shallow cables
Cables may be laid at shallow depths to cross obstructions, subject to an absolute minimum cover
depth of 500mm. Steel plate protection shall be installed instead of polymeric cover strips wherever
the cover depth is between 500mm and 750mm.
Special situations
Where cables run through structures it may be acceptable for the 500mm depth limit to be infringed
as long as adequate protection and warnings are provided to control all foreseeable risks during
construction and operation of the cables and structure. For example - where a cable runs through a
bridge culvert/chase, the cables could be protected by a concrete lid that is clearly marked to show
the presence of HV cables and a stainless steel cover underneath to protect against the impact of
mishandling the concrete lid. Another situation where a ductline runs through a carpark structure
could require the use of permanent warning signs to prevent any future drilling or cutting into the
ductline. Also see NS130 Annex J.
Deep situations
Rating calculations shall be used to ensure that the required cable ratings are achieved in deep
sections, this may require the conduit spacing to be widened or special backfill materials to be
used.
10.9
Trench design
Cables and conduits shall be backfilled using thermally stable backfill (TSB) as indicated in the
following diagrams. The diagrams below show typical cross sections only - the actual cross section
for any particular project will be designed on a case-by-case basis, depending on 




Voltage, size, type, rating & number of cables;
Road classification;
Requirements of local road authority;
Presence of other services;
EMF prudent avoidance
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
Figure 3 - Typical trench cross section - double circuit 132kV single core cables
Figure 4 - Typical trench cross section - four circuit 33kV three core cables
The following trench design constraints shall be adhered to  There shall be a minimum of 100mm of TSB material above, beneath and around the power
cables or conduits.
 Greater thickness of TSB may be needed to accommodate the 50°C isotherm (see 10.6.1).
 Polymeric cover strips shall be installed over the entire trench width for mechanical protection
100mm above the top conduit.
 TSB, DGB20 road base or similar backfill material with an appropriate thermal resistivity shall be
installed above the polymeric cover strips to the underside of pavement.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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Amendment No 1
 There shall be adequate separation between conduits to allow TSB flow.
 TSB backfill shall meet the requirements of NS130 – note in particular the need for thermal
resistivity testing of backfill samples.
 Note that the use of fly ash in TSB incurs various environmental reporting requirements – see
NS130 for details.
 Warning tapes shall be installed at the bottom of the road subbase, at a typical cover depth of
300 - 400mm.
 Road restoration shall be carried out to the requirements of the relevant roads authority.
10.10 Conduits
Conduits shall be Light Duty UPVC orange conduit in accordance with Networks NSW
specification.
Power cable conduits shall be 200mm nominal size for 132kV cables, and 150mm or 200mm
nominal size for 66 & 33kV cables depending on cable size – see Note below.
NOTE
Power cable conduit diameters shall be in accordance with the cable manufacturers’
recommendations. In general the internal diameter (ID) of the conduit shall be at least 40%
greater than the cable’s overall diameter (OD) to allow enough space for the cable to snake
due to thermal expansion. In special circumstances, for example pulling through short
lengths of existing conduit, a smaller conduit size may be accepted if approvals are obtained
from the group within Ausgrid responsible for underground sub-transmission mains designs.
Conduit sizes for telecommunication cables shall be in accordance with NS234 or as otherwise
approved by the group within Ausgrid responsible for telecommunications system design
standards.
Conduit accessories such as bends and collars, and materials for joining and sealing conduits shall
comply with Ausgrid specifications. Conduit bends shall normally have 6m bend radius.
Conduit spacers shall be used for all installations, with conduit separation based on cable rating
requirements and to allow TSB to flow as required. The main purpose of the spacers is to keep the
conduits in their correct position relative to each other and the surrounding soil, and to prevent
them floating as the trench is backfilled. They must be designed so as not to damage the conduits
if they soften due to the heat generated by the TSB or concrete as it cures.
Various spacer types are commercially available.
10.11 Separation from other services and cables
In all cases separations from other services shall be determined in consultation with the other
utility. Ausgrid generally requires a minimum separation of 300mm from other services and cables,
to provide clearance for repairs and to minimise consequent cable derating effects. Refer to
WorkCover Guide to Work Near Underground Assets for details of minimum approach distances to
various utilities.
Additional separation may be required where the cables are to be laid in the vicinity of other power
cables or metal pipes. In these cases, following completion of the services search, the rating
calculations shall allow for mutual heating from these nearby services and separations calculated
to maintain the specified ratings of all circuits.
Note 1: Proximity to Telstra or other copper wire telecommunications cables may result in
unacceptable voltage rises being induced on the communications cables, either under fault
conditions or if the two circuits run in parallel for a long distance. Separations shall be
designed to ensure compliance with the requirements of Telstra or other communications
carriers, as specified in:
 Code of Practice for Protection of Personnel and Equipment against Earth Potential Rises
Caused by High Voltage Power System Faults. (prepared jointly by the Telecommunications
Commission and the ESAA 1984 - covers Earth Potential Rise).
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
 Mitigation of Hazardous Voltages induced into Telecommunications Lines (Low Frequency
Induction Code of Practice 1978 + Application Guide 1984).
 AS3835:2006 Earth Potential Rise – Protection of Telecommunications network users,
personnel and plant.
Note 2: Proximity to metallic pipelines and associated equipment may result in unacceptable
voltage rises being induced on the pipelines. Separation distances shall be designed to
ensure induced voltages on the pipelines are compliant with the requirements specified in
AS4853:2012 Electrical Hazards on Metallic Pipelines.
These requirements apply irrespective of whether the other services are installed before or after
the sub-transmission cable.
10.12 Bonding and earthing
10.12.1 General
The bonding and earthing of any particular cable will be determined on a case-by-case basis
through earthing and rating studies.
33kV three core cables shall be solidly bonded to earth at both ends. 33kV & 132kV single core
cables will normally require special bonding and earthing arrangements, as described below.
The bonding system shall generally be in accordance with EA ER C55/4, and shall be determined
in consultation with Earthing & Insulation Coordination Group as part of a review of the earthing
design of the cable installation and substations at each end of the circuit - including consideration
of public safety, transferred potentials and voltages induced onto adjacent equipment/utilities as
per the requirements of NS260.
Ausgrid does not specify a limit on the standing sheath voltages, however a maximum of 120V is
usually considered appropriate to Ausgrid’s network as long as the cable system design (including
exposed metal parts, serving, joint barriers, bonding leads, link box and Sheath Voltage Limiters
(SVLs)) is fit for purpose under both normal and abnormal operating conditions.
For specially bonded systems, the selection of SVL’s shall take into consideration the standing
sheath voltage under rated load, the power frequency sheath voltage under fault conditions, the
transient over voltages that may be encountered and the level to which these over voltages should
be limited.
Bonding leads shall have stranded copper conductors with a cross sectional area of 300mm2 for
66kV & 132kV cables, and 185mm² for 33kV cables. Concentric bonding leads shall be used at
mid-route joint bays to reduce surge impedance. Single core bonding leads shall be used at
terminations, normally to single phase link boxes at outdoor terminations and three phase link
boxes at GIS terminations. Bonding leads shall be no longer than 10m long to limit surge
impedance.
Any heating effect of circulating sheath currents must be taken into account when calculating the
cable’s current rating.
Ausgrid’s specifications for bonding lead and ECC cables are available on request.
10.12.2 Single point bonding
In this arrangement the cable sheaths are solidly bonded to earth at one end only. The
sheath/screen at the other end is isolated from earth potential through a Sheath Voltage Limiter
(SVL). The SVL provides a high resistance path to earth under normal conditions and a low
resistance as sheath voltage increases, thereby protecting the cable’s outer sheath and auxiliary
components from unacceptably high sheath voltages under transient fault conditions.
Where single point bonding is used, it will normally be necessary to run one or multiple earth
continuity conductors (ECCs), as close as possible to the cables, transposed halfway along the
cable section to balance impedances, and connected to the substation, pit or UGOH earthing
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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Amendment No 1
system at each end. ECCs shall be 185mm² or 300mm² conductor size, as specified by Earthing &
Insulation Coordination Group.
Figure 5 - Single point bonding
Figure 6 - Link box without SVLs
10.12.3 Full cross bonding
New cross-bonding systems shall use “sectionalised cross bonding” as described in EA ER C55/4.
The cable sheaths shall be bonded between phases in succession (RW, WB and BR etc.) to
cancel out any sheath currents over three minor sections, with SVLs to minimise transient sheath
overvoltages. The three minor sections will form a major section with earth bonding at each end.
The lengths and cable configurations shall be designed so that the induced voltages of the three
minor sections balance to near-zero, this can be achieved by adopting the same cable
configuration in each minor section and joint bay positions being chosen so that the longest minor
section length is <5% longer than the shortest minor section length. If the imbalance is between 5%
& 10% then the design shall be reviewed to ensure that sheath voltages are acceptable and that
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
rating calculations have taken into account the heating effect of circulating sheath currents.
Imbalances >10% are not acceptable.
Note: the example shown below also shows the transposition of single core cables which is
required if the cables are installed in a flat configuration. Ausgrid’s preferred configuration for
the vast majority of new installations is trefoil in which case transposition is not generally
required.
Figure 7 - Cross bonding
Figure 8 - Cross-bonding link box
10.12.4 Looping existing circuits into new substations
From time to time, it is necessary to cut an existing cable and loop it into a new substation. Such
actions may significantly impact on the existing earthing and bonding arrangements and thermal
ratings, as well as gas pressure or fluid filled circuit design. Where possible the existing design
shall be maintained. However, where this is not practicable, the group within Ausgrid responsible
for earthing, cable ratings and transmission mains designs shall provide advice on the basic
requirements to be met to comply with system earthing design. This may, for example, involve
inserting a single point bonded section (with or without a separate bonding conductor) at the loop
in, and a modification to the existing cross bonding arrangements for the rest of the circuit.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
Underground Cables
Amendment No 1
10.12.5 Bonding connections at GIS terminations
Special measures need to be taken where CTs are present under 132kV GIS terminations, as all
earthing/bonding connections need to be brought down through the CTs to cancel out any sheath
currents. Bonding connections for GIS terminations are shown in NS260 section 7.11.
10.13 Joint bays and vaults
Transmission cables will normally be jointed in a joint bay which is backfilled after jointing is
complete. The use of jointing vaults may be specified for CBD areas, these are accessible spaces
(not backfilled) and requirements are detailed in NS172.
10.13.1 Joint bay location
Cable section lengths shall be maximised so that a minimum number of joints are needed,
consistent with the constraints of the bonding system design. Pulling tension calculations shall be
used to ensure the cables can be successfully installed within the constraints of pulling tensions
and sidewall pressures.
Joint bays shall be located where they will be readily accessible for future repairs and preferably
clear of driveways, intersections and other infrastructure.
Joint bays shall not be located in the carriageway of classified roads except with the written
approval of the group within Ausgrid responsible for underground sub-transmission mains designs.
All joint bay locations shall be investigated by trial hole excavation in order to confirm that the
location is suitable for the bay/pit construction intended.
10.13.2 Joint bays for 33kV cables
33kV cable jointing shall be carried out in a joint bay that consists of a concrete floor. Concrete
walls may be used where shoring, cross-bracing or water ingress causes an unacceptable
hindrance to jointing works.
The dimensions of joint bays shall be based on the following:




number of cables,
distance required to space out cables for jointing,
length of joints,
“parking” distance required for jointing components,
A typical joint bay for three 33kV 3c 500mm2 XLPE feeders will have internal dimensions of 2m
width and 10m length.
Joint bays that involve single core cables, special bonding and link boxes will require earthing
works to be installed as for 132kV cable joint bays described below.
10.13.3 Joint bays for 132kV & 66kV cables
132kV & 66kV cable jointing shall be carried out in a joint bay that consists of a concrete floor and
walls.
The dimensions of joint bays shall be based on the following:




number of cables,
distance required to space out cables for jointing,
length of joints,
“parking” distance required for jointing components,
A typical joint bay for two 132kV 1c 1200mm2 XLPE feeders will have internal dimensions of 2.8m
width and 14m length.
Joint bays that involve special bonding and link boxes will require an earthing design to comply with
NS260 section 7.5, this will normally include multiple earth electrodes and earth bond connections
between the joint bay reinforcing bars, link box pit reinforcing bars, link boxes and any ECCs.
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Amendment No 1
10.13.4 Support of cables & joints
Cables and joints shall be supported and restrained to prevent any movement during operation and
future excavations, eg for a fault repair on one feeder. Suitable supports include shaped Hebel-type
blocks, and stainless steel posts and cleats.
10.13.5 Joint bay backfilling
Joint bays shall be backfilled with suitable sand to a depth of 100mm above the top of the joints,
this sand shall be watered-in around the joints rather than compacted to prevent damage.
Polymeric cover strips shall be laid over the sand layer across the entire area of the joint bay, and
TSB (200-300mm depth) and warning tapes shall then be installed as per the normal trench
design.
10.14 Underground to overhead structures (UGOHs)
An underground to overhead transition structure (UGOH) is required where an underground section
of cable connects to an overhead section.
Where a section of underground cable is proposed that is near to an existing UGOH structure on
the same circuit, Ausgrid may require that the proposed underground cable is extended to the
existing cable installation so that a short section of overhead mains and two UGOHs are not
required on the network.
In the case of tower line terminations, the size and rating of the cables required to match the
overhead line rating may require a transition point enclosure that will house cable terminations,
surge arresters, station posts and other equipment. Ausgrid will determine the requirements for
tower line UGOH transition points on a case by case basis.
For tee connections to tower lines and terminations on most pole lines, a pole mounted structure
will be suitable. A concrete or steel pole shall be used for UGOH structures. Timber poles must not
be used for UGOH poles without written approval from the group within Ausgrid responsible for
underground sub-transmission mains designs. Structures made from other materials or that are not
a single pole structure will be considered on a case by case basis.
Table 1 - Standard Sub-transmission UGOH Drawings
Drawing
Number
Construction
Code
Drawing Description
Standard Construction 33kV UGOH on Concrete Pole General
Arrangement (uses flexible terminations)
232985
229262
-
Standard Construction 33kV UGOH for Concrete Pole
300mm2 – 600mm2 Twin Cables per Phase Screen Earthed
Assembly General Arrangement (uses flexible terminations)
227403
-
Standard Construction 33kV UGOH for 3 Core Cable Flexible
Terminations General Arrangement
192881
-
Standard Construction 66kV UGOH on Concrete Pole General
Arrangement
221569
-
Standard Construction 66kV UGOH on Concrete Pole 300mm
2
to 800mm – Twin Cables per Phase General Arrangement
221816
-
Standard Construction 132kV Transmission Line UGOH
Termination Arrangement
2
Other UGOH designs will be considered by Ausgrid on a case by case basis where none of the
constructions above are suitable for a particular application.
Particular attention must be given to the embedment depth and footing design of UGOH poles and
structures. Typically a UGOH pole will be required to support itself and any attached mains with 23m of excavation around the pole for the installation of the cable. Therefore pole embedment
calculations must consider the loadings on the pole with this open excavation around the pole.
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NS168 Specification for the Design and Construction of 33kV, 66kV and 132kV
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Amendment No 1
A hard setting pole backfill such as concrete must not be used within the zone where cables are
expected to be laid against the pole, but may be used below the level of the proposed cables. For
backfilling at the level where cables are fixed to the pole a material should be used that can easily
be removed if required without damage to the cable (such as a 20:1 sand cement mix). The
thermal resistance value of this material must also be considered.
Power cable conduits should be terminated a reasonable distance from the UGOH pole to enable
the direct-buried cable to be phased correctly, splayed out, dipped down and bent with the required
radius onto the UGOH pole. The distance required will vary based on the size, quantity and voltage
of the cable. The use of formed conduit bends to bend the cable up onto a UGOH pole shall be
avoided due to the complexities and added tensions involved in pulling the cable through such a
system.
Unless totally impractical, the installation of other voltages or equipment on the UGOH pole should
be avoided to assist in the cable termination process.
When selecting UGOH pole locations the design must also consider allocation of the space for
construction, jointing and operation of the UGOH pole including:
 Excavation and stockpiling of spoil.
 Space for laying and standing the pole including positioning of the crane.
 Cable drum setup or setup of cable pulling equipment.
 Laying out and pulling cables past the UGOH structure prior to standing the cables on the pole.
 Access and setup of a crane and EWP’s for standing the cable on the pole, including
consideration of any existing overhead conductors on or near the pole.
 Scaffold erecting, operation and removal:
- Size of footprint
- Ground stability (especially when recently excavated)
- Existing overhead mains
- Working at heights
- Traffic and pedestrians
- Access by unauthorised persons
 Network requirements in obtaining outages for long periods on nearby live equipment during the
jointing process.
 Earthing requirements and restrictions. This will have a significant impact on how close the
UGOH can be to existing utilities, with particular restrictions on the proximity to telecom pits,
pipeline valves, and the Multiple Earthed Neutral distribution system.
 Traffic and pedestrian safety during and after construction.
 Vehicle or machinery impacts, Ausgrid may require permanent barriers to be constructed
adjacent to the UGOH to reduce the risk of the UGOH being damaged due to a vehicle or
machinery impact. Ausgrid may disallow the UGOH being placed in a location where Ausgrid
considers the risk of damage to the UGOH, or risk to safety of maintenance personnel to be too
great.
 Environmental, aesthetics and surrounding land uses.
 EMF prudent avoidance.
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Considerations for determining whether to prepare terminations on the ground or when the cable is
cleated to pole :
Consideration
Prepare terminations on ground
Prepare terminations on pole
Trenching and
excavation
Excavation must remain open around
UGOH pole for duration of jointing
works.
Need sufficient room to ramp cables
up out of trench and setup for jointing
approx. 10m from UGOH pole.
Scaffolding not required. Tent can be
erected to provide some protection
from weather on the ground. Less
chance of fatigue and minimising risks
related to working at heights.
Excavations can be backfilled as soon
as cable is cleated to pole (required
for scaffolding).
Need sufficient space and terrain to
setup scaffold or EWP around pole.
Space requirement
Working conditions
Network outages
Network outage generally only
required for lifting completed
termination on the pole.
Damage to cable
Risk of damage to terminations during
lifting and fixing of termination to pole.
Cables need to be cleated top down
and aligning the cable into the cleats is
more challenging on larger cable.
The length of cable required from the
trench to termination has to be
measured accurately. If the cable is
too long additional excavation may be
required around the UGOH to take the
additional length. Too short and the
cable may be too shallow in the ground
at the UGOH and the cable bending
radius may be compromised.
Whilst lifting the cable onto the pole,
the cable core may rotate. A rotating
base must be used on 132kV selfsupporting terminations. A rotating
palm connection on a stalk must be
used for 33kV and 66kV flexible
terminations.
Security will be required out of hours
for the full jointing process.
Measurement of
cable length up pole
Cable rotation
Security
132kV cable requires scaffolding.
33kV and 66kV may be able to use
EWPs. Extended time working at
heights. Major effort to provide a
weather proof enclosure if required.
EWP restricts productivity of staff.
Mains in close proximity to jointing
location may need to be on a short
recall outage is working from an EWP
or an extended outage where scaffold
is used.
Non-terminated cable is lifted onto the
pole. Cleating can commence bottom
up with the crane able to assist in
manoeuvring the cable into the cleats.
As cable is already fixed into position
measuring the cable for cutting and
stripping is relatively simple. The
terminations can be built to the correct
alignment as it sits on the pole.
As the cable is already fixed in
position on the pole there is no further
rotation of the core to be considered.
Once covers are on the pole and
backfilling is complete security usually
not required when working from an
EWP. Security required for out of
hours when scaffolding is erected.
10.15 Route markers
The use of route markers shall be considered wherever cables are installed in locations off public
roads (eg parks, reserves, beaches, river/rail crossings & easements).
Route markers are intended to reduce the risk of cable damage by providing a physical indication
of the presence of transmission cables in areas where they may not be expected, or where there is
an increased risk that a contractor may not take adequate precautions before starting work. Route
markers are NOT intended to be a survey mark to indicate the precise location of cables – a Dial
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Before You Dig query, cable plans and proper cable location techniques should be used to
precisely locate the cables.
The location and type of route marker shall be decided in consultation with the landowner, including
due consideration of current and planned land usage, in accordance with the following guidelines –
 Each marker should be visible from the adjacent markers.
 Marker separation shall preferably be less than 200m to ensure good visibility, but can be up to
400m if circumstances dictate.
 A marker should be located at a property boundary where the cable route leaves a public road.
 A marker should be located where a substantial change of route direction occurs.
 Markers should preferably be located along fencelines, rows of trees, property boundaries and
similar features.
 Markers shall be easily seen without being obtrusive or interfering with pedestrian/vehicle traffic
or posing a risk to public safety.
 Markers shall be located on the route centreline, or offset on the edge of the trench if the backfill
material makes the centre location impossible.
 Marker posts are preferred as they are easily visible, however marker bricks flush with the
ground surface can also be used.
 Water crossings require the use of specific signage – see the NSW Maritime publication
“Crossings of NSW Navigable Waters : Electricity Industry Code”.
Route marker details –
 Marker post – drawing 42087, stock code 91082
 Marker brick – stock code H16520
10.16 Telecommunications
Telecommunications routes must be designed in accordance with the approved
telecommunications brief supplied by Ausgrid’s Senior Engineer responsible for
telecommunications planning.
Pulling calculations for optical fibre cables must be performed in accordance with NS234.
Telecommunications hauling pits must be designed and installed in accordance with NS204.
Route marking in accordance with NS205 must be applied to telecommunications infrastructure
which strays away from the HV feeder trench for reasons including but not limited to connection
with telecommunications pits or for UGOH transition.
Refer to the Senior Engineer responsible for telecommunications planning for further guidance on
route selection.
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11.0 CONSTRUCTION
11.1
Hazards from existing underground cables
11.1.1 Oil
Ausgrid’s existing underground sub-transmission cable system includes approximately 380 route
km of oil-filled cables. Oil filled cables are pressurised with insulating oil that is generally a mix of
original mineral oil and later synthetic linear alkylbenzene oil that has improved biodegradation
characteristics. Due to past damage or leaks the soil surrounding these cables may be
contaminated with cable oil, and will need to be appropriately handled and disposed of. Where
known these cables will be identified in the Development Brief.
11.1.2 PCB
PCB contamination has been found inside some oil-filled cables. Oil testing shall be carried out to
identify the presence & concentration of PCBs before works start on oil-filled cables, and
appropriate safety controls should be adopted.
11.1.3 OCP
During the installation of oil-filled cables (pre 1980) the backfill placed around the cables was often
saturated with OCPs, usually aldrin and dieldrin, to protect from termite damage. OCPs were also
added to the cable sheaths during manufacture of some oil-filled cables. Hence when working on
the sheaths of oil-filled cables, or in trenches where oil-filled cables are installed, appropriate
handling and disposal precautions must be applied. These precautions may include tests for OCPs
and the use of Personal Protective Equipment – see NS156 for further information.
11.1.4 Asbestos
Asbestos (AC/fibro) conduits were commonly used on Ausgrid’s network. If any asbestos is
encountered then safe work method statements and appropriate practices must be implemented.
Materials containing asbestos must be handled by a licensed contractor. This material should be
disposed to an appropriately licensed landfill.
11.1.5 Energised cables
Also refer to NS156 Working Near and Around Underground Cables.
For work that involves joint bays for existing cables, a risk assessment shall be carried out to
control the risks from energised cables and induced/transferred potentials, and it may be necessary
to de-energise some or all of the cables during some or all of the work. All cables in an existing
joint bay must be accurately identified and shown clearly on all plans to be used during
construction.
11.2
Hazards from contaminated land
If part of the route crosses known contaminated land, options to mitigate the potential future safety
hazards for staff or impacts to the cables must be considered as part of the design and
environmental planning approval. These may include the following:




Re-route the cables away from the contaminated land.
Enclose the cable in special fill which provides an impermeable barrier to the contaminants.
Treat or encapsulate the contaminated soil.
Design of suitable cable sheaths (e.g. lead sheath, selected polymers or use of a fluoropolymer
layer.
 Special mixes to prevent concrete degradation.
11.3
Installation precautions
Temporary steel plates over trenches must have skid resistance comparable with the road. This
can be achieved by coating the road plates with a suitable epoxy coating such as “Epirez Supatuff
HD”, and then applying 0.5 mm (200 –600 micron) quartzite aggregate (QA 2). Prior to applying the
antiskid coating, the surface of the road plate must be prepared in accordance with the
manufacturer’s recommendations. With the road plate in position, a natural taper should be made
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with asphalt between the road surface and the steel plate to eliminate any sudden level changes
that could destabilise a cyclist.
All conduits shall be mandrel tested as per the requirements of NS130, and shall be cleaned
shortly before cable pulling to prevent cable damage due to stones/debris.
To avoid cable damage during installation, cable pulling tensions shall generally be restricted to
80% of the cable supplier’s nominated maximum pulling tension for the cable and factory-applied
pulling eye, and shall ensure that the cable sidewall pressure limit is not infringed. Other
constraints include the pull-out strength of pulling eyes in pits or walls of substations, and the rated
capacity of the pulling stocking if used. Pulling tensions shall be monitored by dynamometer during
every cable pull, and records of (a) pulling tensions vs distance and (a) time vs distance shall be
provided on completion of every cable pull.
Vandalism and attempted theft can lead to substantial cable damage and project delays. Ausgrid’s
minimum requirements to guard against damage are –
 Cables shall be stored in a secure location before installation.
 Cable drums shall not be left unattended once on site, this includes the provision of a security
guard if the cable drum has to be kept on site outside working hours.
 Exposed cables in joint bays, pulling pits etc shall be protected by either covering the
excavation with steel plates or concrete lids that are not readily removable by hand, or the
provision of a security guard outside working hours.
Water ingress into the joint bay after cable pulling can lead to substantial cable damage and project
delays, but can be easily avoided. Water can enter via surface runoff, groundwater seepage and
via the incoming conduits. Ausgrid’s minimum requirements to guard against water damage are –
 Immediately after each cable pull, the cut end shall be triple-sealed by staff who are specifically
trained to carry out this work. Sealing shall be achieved through the use of heat-shrink caps and
tubing as shown below. The minimum overlap required between the oversheath of the cable
and the cap shall be 75mm, and all shrinkable components must be coated with adhesive
sealant.
Figure 9 - Sealed cable
 It is acceptable to leave the original pulling eye on the other end of the cable providing that the
pulling eye is adequately rated & tested against water ingress, and that no significant damage
has occurred to the waterproofing components during pulling.
 All cable ends shall be raised & supported to the maximum possible level in the joint bay to
minimise exposure to high water levels in the period before jointing starts.
 The joint bay shall be kept clear of incoming water from the time that the first cable sealed end
is removed for jointing until all joints are effectively waterproof. Precautions shall include having
a pump, generator and water storage capacity available on site, and adequate staff &
inspections to ensure that water is pumped out at all times including nights, weekends and
public holidays. Particular attention should be given to weather forecasts as severe storms can
cause large sudden volumes of runoff, and the joint bay shall be surrounded with suitable runoff
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protection, eg coldmix berm around the joint bay, and pipes to maintain gutter flow past the joint
bay.
12.0 FINAL PROJECT DOCUMENTATION
On completion of construction, the following information shall be provided to Ausgrid as an
Operations & Maintenance Manual :









Route plan.
Bonding schematic.
Rating calculations.
ITPs for cables, including sample & routine factory test reports and any cable site test reports
(eg serving tests).
ITPs for cable accessories, including routine factory test reports, serial numbers and jointer
checklists.
ITPs for cable pulling, including pulling tension values.
Final construction drawings, including layout for each joint bay.
Soil test reports, including thermal & electrical resistivity.
TSB backfill test reports, including thermal resistivity.
All drawings shall be provided in the format required by NS104.
13.0 RECORDKEEPING
The table below identifies the types of records relating to the process, their storage location and
retention period.
Table 2 – Recordkeeping
Type of Record
Storage Location
Retention Period*
Approved copy of the network
standard
BMS Network sub process Standard –
Company
Unlimited
Draft Copies of the network
standard during
amendment/creation
TRIM Work Folder for Network
Standards (Trim ref. 2014/21250/87)
Unlimited
Working documents (emails,
memos, impact assessment
reports, etc.)
TRIM Work Folder for Network
Standards (Trim ref. 2014/21250/87)
Unlimited
* The following retention periods are subject to change eg if the records are required for legal
matters or legislative changes. Before disposal, retention periods should be checked and
authorised by the Records Manager.
14.0 AUTHORITIES AND RESPONSIBILITIES
For this network standard the authorities and responsibilities of Ausgrid employees and managers
in relation to content, management and document control of this network standard can be obtained
from the Company Procedure (Network) – Production/Review of Network Standards. The
responsibilities of persons for the design or construction work detailed in this network standard are
identified throughout this standard in the context of the requirements to which they apply.
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15.0 DOCUMENT CONTROL
Content Coordinator
:
Transmission and Distribution Mains Engineering Manager
Distribution Coordinator
:
Engineering Information and Services Manager
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Annexure A – Sample Compliance Checklist
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