Technical Note – TN 006: 2019
Technical Note – TN 006: 2019
Subject: Clarification of substation fencing requirements where existing locations are modified
Issue date: 13 May 2019
Effective date: 13 May 2019
For queries regarding this document [email protected]
www.transport.nsw.gov.au
This technical note is issued by the Asset Standards Authority (ASA) to notify an update to
T HR EL 99004 ST Substation Fencing, version 1.0 to clarify the substation fencing requirements
where existing locations are required to be modified and repaired.
Delete Section 6.2 in its entirety and replace with the following:
6.2 Existing locations Existing fences that do not comply with current design requirements shall be upgraded when the
fence is due for renewal, or when enhancement is required as determined by a risk assessment.
6.2.1 Modifications Where existing fences are to be modified, the design and construction of the modifications shall
be such that the resultant fence configuration shall comply with this document. Where it is not
reasonably practicable to do so, the designer shall list all noncompliances and the proposed
design approach to mitigate the risks associated with each of the listed noncompliances.
Acceptance of the mitigation measures by the relevant authority of the operations and
maintenance AEO is required prior to the commencement of detailed design. If the design and
construction of the modified fence provides a security outcome that is equivalent or better than
the existing fence configuration and is accepted by the relevant authority of the operations and
maintenance AEO, then a concession is not required for the noncompliance.
6.2.2 Repairs Repairs to the existing fences shall comply with Section 11 of T HR CI 12160 ST, version 1.0.
© State of NSW through Transport for NSW 2019 Page 1 of 2
Technical Note – TN 006: 2019
Authorisation:
Technical content prepared by
Checked and approved by
Interdisciplinary coordination checked by
Authorised for release
Signature
Date
Name Rukshan Guruge Terry Niemeier Peter McGregor Jagath Peiris
Position Senior Engineer Substations and HV Network
Lead Electrical Engineer
A/Chief Engineer A/Director Network Standards and Services
© State of NSW through Transport for NSW 2019 Page 2 of 2
Substation Fencing
T HR EL 99004 ST
Standard
Version 1.0
Issued date: 16 November 2017
© State of NSW through Transport for NSW 2017
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
Important message
This document is one of a set of standards developed solely and specifically for use on Transport Assets (as defined in the Asset Standards Authority Charter). It is not suitable for any other purpose. The copyright and any other intellectual property in this document will at all times remain the property of the State of New South Wales (Transport for NSW). You must not use or adapt this document or rely upon it in any way unless you are providing products or services to a NSW Government agency and that agency has expressly authorised you in writing to do so. If this document forms part of a contract with, or is a condition of approval by a NSW Government agency, use of the document is subject to the terms of the contract or approval. To be clear, the content of this document is not licensed under any Creative Commons Licence. This document may contain third party material. The inclusion of third party material is for illustrative purposes only and does not represent an endorsement by NSW Government of any third party product or service. If you use this document or rely upon it without authorisation under these terms, the State of New South Wales (including Transport for NSW) and its personnel does not accept any liability to you or any other person for any loss, damage, costs and expenses that you or anyone else may suffer or incur from your use and reliance on the content contained in this document. Users should exercise their own skill and care in the use of the document. This document may not be current and is uncontrolled when printed or downloaded. Standards may be accessed from the Asset Standards Authority website at www.asa.transport.nsw.gov.au
© State of NSW through Transport for NSW 2017
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
Standard governance
Owner: Lead Electrical Engineer, Asset Standards Authority
Authoriser: Chief Engineer, Asset Standards Authority
Approver: Executive Director, Asset Standards Authority on behalf of the ASA Configuration Control Board
Document history
Version Summary of changes
1.0 First issue
For queries regarding this document, please email the ASA at [email protected] or visit www.asa.transport.nsw.gov.au
© State of NSW through Transport for NSW 2017
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
Preface The Asset Standards Authority (ASA) is a key strategic branch of Transport for NSW (TfNSW).
As the network design and standards authority for NSW Transport Assets, as specified in the
ASA Charter, the ASA identifies, selects, develops, publishes, maintains and controls a suite of
requirements documents on behalf of TfNSW, the asset owner.
The ASA deploys TfNSW requirements for asset and safety assurance by creating and
managing TfNSW's governance models, documents and processes. To achieve this, the ASA
focuses on four primary tasks:
• publishing and managing TfNSW's process and requirements documents including TfNSW
plans, standards, manuals and guides
• deploying TfNSW's Authorised Engineering Organisation (AEO) framework
• continuously improving TfNSW’s Asset Management Framework
• collaborating with the Transport cluster and industry through open engagement
The AEO framework authorises engineering organisations to supply and provide asset related
products and services to TfNSW. It works to assure the safety, quality and fitness for purpose of
those products and services over the asset's whole-of-life. AEOs are expected to demonstrate
how they have applied the requirements of ASA documents, including TfNSW plans, standards
and guides, when delivering assets and related services for TfNSW.
Compliance with ASA requirements by itself is not sufficient to ensure satisfactory outcomes for
NSW Transport Assets. The ASA expects that professional judgement be used by competent
personnel when using ASA requirements to produce those outcomes.
About this document
This standard specifies the requirements for the construction of fences associated with
substations within the Transport for NSW heavy rail network.
This standard supersedes RailCorp standard EP 99 00 00 07 SP Substation Fencing,
version 3.1. The changes to previous content include:
• updates to reflect organisational changes and resulting changes in responsibilities
• conversion of the standard to ASA numbering, format, and style
• alignment with the Energy Networks Australia (ENA) Guidelines
• inclusion of guidance for boundary and internal enclosure fences
• minor amendments and clarification to content
This standard is a first issue.
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T HR EL 99004 ST Substation Fencing
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Table of contents 1. Introduction .............................................................................................................................................. 7
2. Purpose .................................................................................................................................................... 7 2.1. Scope ..................................................................................................................................................... 7 2.2. Application ............................................................................................................................................. 7
3. Reference documents ............................................................................................................................. 8
4. Terms and definitions ............................................................................................................................. 9
5. Fence types .............................................................................................................................................. 9 5.1. Boundary fence ...................................................................................................................................... 9 5.2. Intruder resistant fence ........................................................................................................................ 10 5.3. Internal enclosure fence ...................................................................................................................... 10
6. Design requirements ............................................................................................................................. 10 6.1. General ................................................................................................................................................ 10 6.2. Existing locations ................................................................................................................................. 11 6.3. Boundary fence .................................................................................................................................... 11 6.4. Intruder resistant fence ........................................................................................................................ 12 6.5. Internal enclosure fence ...................................................................................................................... 12 6.6. Welded mesh fence construction ........................................................................................................ 12 6.7. Alternative fencing materials................................................................................................................ 13 6.8. Toppings .............................................................................................................................................. 13 6.9. Kerbing ................................................................................................................................................. 13 6.10. Ground level and fence height ......................................................................................................... 14 6.11. Climbing aids ................................................................................................................................... 14 6.12. Gates ............................................................................................................................................... 15 6.13. Clearance zone ................................................................................................................................ 17 6.14. Vegetation ........................................................................................................................................ 17
7. Electrical clearance ............................................................................................................................... 17 7.1. Non-penetrable panel .......................................................................................................................... 18
8. Substation fence earthing, bonding and isolation ............................................................................. 18 8.1. Earthing and bonding ........................................................................................................................... 18 8.2. Isolation and transfer potential mitigation ............................................................................................ 18 8.3. Testing and measurement ................................................................................................................... 19
9. Signage ................................................................................................................................................... 19
10. Construction factors ............................................................................................................................. 20
11. Maintenance ........................................................................................................................................... 20
Appendix A Additional references and drawings ................................................................................ 21 A.1. Documents ........................................................................................................................................... 21 A.2. Drawings .............................................................................................................................................. 21
Appendix B Substation fencing examples ........................................................................................... 22 B.1. Traction SS, section hut, or system SS – Indoor HV switchgear ........................................................ 22 © State of NSW through Transport for NSW 2017 Page 5 of 23
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B.2. Traction SS or system SS – Outdoor HV switchgear and exposed busbars ...................................... 22 B.3. 1500 V link or switch enclosure (free standing) ................................................................................... 23
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T HR EL 99004 ST Substation Fencing
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1. Introduction Unauthorised access to electricity infrastructure is considered to have a high-risk profile due to
the consequences of receiving an electric shock. Fences are one of the primary means of
limiting access to outdoor electrical installations at ground level, such as high voltage
substations.
2. Purpose The purpose of this standard is to provide requirements and guidance to ensure that fencing
associated with substations, sectioning huts and distribution substations in the RailCorp
distribution network or traction system is constructed properly and is fit for purpose.
This standard is based on ENA DOC 015 – 2006 National Guidelines for Prevention of
Unauthorised Access to Electricity Infrastructure.
2.1. Scope This standard specifies the requirements for the construction of fences associated with
substations within the Transport for NSW heavy rail network.
It defines the following three types of fencing for use in limiting access to persons:
• boundary
• intruder resistant
• internal enclosure
2.2. Application This standard is intended to be used by competent personnel engaged in the provision of
services relating to rail infrastructure. If, when using the standard, it is considered that the intent
of stated requirements is not clear, a clarification should be sought from the ASA Lead Electrical
Engineer.
In this standard, substation includes a substation, traction substation, transformer room, switch
room, sectioning hut, 1500 V link or switch area, containing either high voltage or 1500 V
electrical equipment.
This standard is applicable for all new substations associated with the heavy rail system in
NSW. It is not applicable to pole or pad mounted substations unless a risk assessment
determines that fencing is required. For existing locations, refer to Section 6.2.
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Where a new location or modification to an existing location is constructed and energised in
stages, the risk of unauthorised access to the site and to exposed electrical equipment shall be
managed.
3. Reference documents The following documents are cited in the text. For dated references, only the cited edition
applies. For undated references, the latest edition of the referenced document applies.
Australian standards
AS 2067:2016 Substations and high voltage installations exceeding 1 kV a.c.
AS 3600 Concrete Structures
AS/NZS 4680:2006 Hot-dip galvanized (zinc) coatings on fabricated ferrous articles
AS/NZS 4792:2006 Hot-dip galvanized (zinc) coatings on ferrous hollow sections, applied by a
continuous or a specialized process
Transport for NSW standards
EP 12 10 00 10 SP System Substation Earthing
RSS-003 Railcorp Security Standard – Substations (available on request from
www.asa.transport.nsw.gov.au)
SPC 511 Boundary Fences
T HR CI 12160 ST Boundary Fences, version 1.0
T HR EL 99002 ST Substations Minimum Construction Standard
T HR EL 00006 ST Electrical Power System Signage
T MU MD 00009 ST AEO Authorisation Requirements
T MU MD 00011 ST Concessions to ASA Requirements
Transport for NSW drawings
EL 0450708 Substations Fencing - Typical Construction - Arrangement - Sheet 1
EL 0450709 Substations Fencing - Typical Construction - Arrangement - Sheet 2
EL 0450710 Substations Fencing - Typical Construction - Arrangement - Sheet 3
EL 0450711 Substations Fencing - Typical Construction - Details - Sheet 4
EL 0450712 Substations Fencing - Clearances to Climbing Aids - Details - Sheet 5
EL 0450713 Substations Fencing - Non Penetrable Panel - Arrangement - Sheet 6
EL 0455333 Substations Fencing - Typical Construction - Emergency Egress Gate
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Other reference documents
ENA DOC 015 – 2006 National Guidelines for Prevention of Unauthorised Access to Electricity
Infrastructure
4. Terms and definitions The following terms and definitions apply in this document:
AEO Authorised Engineering Organisation
ASA Asset Standards Authority
ENA Energy Networks Australia
HV high voltage
SS substation
Note: This standard applies to specific substation types, see Section 2.2
TfNSW Transport for NSW
5. Fence types ENA DOC 015-2006 National Guidelines for Prevention of Unauthorised Access to Electricity
Infrastructure nominates different requirements for fencing depending on the purpose of the
fencing at a location.
Fencing associated with substations can be classified into the following three groups as
illustrated in Figure 5.1 of ENA DOC 015-2016:
• boundary fence
• intruder resistant fence
• internal enclosure fence
Note: TfNSW installations do not typically employ a sterile zone or sterile zone fence.
However, RSS-003 Railcorp Security Standard – Substations, may require a sterile
zone to be included in the design for Category 1 and Category 2 substations.
5.1. Boundary fence A substation boundary fence performs the following functions:
• identifies the substation site boundary
• limit the access of persons and vehicles to the site
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5.2. Intruder resistant fence An intruder resistant fence is designed to limit the opportunity for intruders to climb over,
through or pass under the fence without the aid of tools. They are typically used to prevent
access to outdoor switchyards where live exposed conductors are present, or at higher risk
locations where a security risk assessment determines the requirement of such a fence.
5.3. Internal enclosure fence An internal enclosure fence is used to prevent unintended access to exposed electrical
equipment at or close to ground level within substation switchyards. For example, internal
enclosure fencing could be used around capacitor banks, auxiliary supply transformers and
voltage transformer.
An internal enclosure fence shall always be inside an intruder resistant fence.
Note: An internal enclosure fence is also referred to as a high voltage (HV) equipment
enclosure or cage in ENA DOC 015-2016.
6. Design requirements 6.1. General
All substation fences shall be designed in accordance with T HR CI 12160 ST Boundary
Fences, version 1.0 and any additional requirements detailed in this standard.
All sites, existing and new, shall be assessed prior to the design. This assessment may
influence the fence type, and the design shall ensure that the fence provides the appropriate
level of security, and shall maintain a safe working environment. Refer to T HR EL 99002 ST
Substations Minimum Construction Standard for general substation security considerations.
The Authorised Engineering Organisation (AEO) shall ensure that consultation takes place with
appropriate TfNSW stakeholders, such as operators, maintainers and the TfNSW area
responsible for security and emergency management.
The design life of fences shall be a minimum of 20 years.
All substations are considered high-risk and shall have boundary fencing, irrespective of the
rate of crime or antisocial behaviour a particular location might experience.
Note: An existing corridor or boundary fence that complies with this standard may be
utilised as the substation boundary fence, subject to a site-specific risk assessment.
Substation buildings may form part or a whole of the boundary fence or intruder resistant fence
on the basis of a risk assessment by the AEO. The risk assessment shall address whether the
building requires a higher security rating for the doors, windows, security systems, and so forth.
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If the building is to form part of the fence, then the exterior of the building shall be of a
construction that minimises hand and foot holds.
An intruder resistant fence is not required if there is a building with no external electrical
equipment, and if the risk assessment by the AEO determines the building as being adequately
secure.
All substation fences shall be designed such that any structures or fixtures that might aid a
person climbing the fence are positioned clear of the fence. The minimum climbing aid
clearance shall be 3 m on both sides. If this is not achievable then refer to Section 6.11.
All fences performing the function of a boundary fence shall have a pedestrian gate and double
vehicular gates. These gates should be positioned so that access to the substation does not
require access via the rail corridor. The vehicular gates shall be internally accessed via the
pedestrian gate. All intruder resistant fences and internal enclosure fences shall have gates
appropriate for the enclosure and the equipment contained.
Fencing elements that are required to be galvanised by this standard shall comply with either
AS/NZS 4680:2006 Hot-dip galvanized (zinc) coatings on fabricated ferrous articles or
AS/NZS 4792:2006 Hot-dip galvanized (zinc) coatings on ferrous hollow sections, applied by a
continuous or a specialized process.
6.2. Existing locations Where existing locations are to be modified, the design and construction of the modification
shall be such that the resultant configuration of the whole location shall comply with this
standard. Where it is not practicable to do so, the designer shall list all noncompliances and
identify the associated hazards with a hazard log. The designer shall propose a design
approach to mitigate the risk of unauthorised access, as well as other risks, associated with the
noncompliance. The mitigation measures shall be accepted by the relevant AEO prior to the
commencement of detailed design, and be in accordance with the AEO’s judgement of
significance (JOS) processes for substations. Refer to T MU MD 00009 ST AEO Authorisation
Requirements. Where the AEO has not established a JOS process for substations that has
been accepted by the Lead Electrical Engineer ASA, the proposed design shall be documented
through a standards concession, in accordance with T MU MD 00011 ST Concessions to ASA
Requirements.
6.3. Boundary fence Boundary fences that do not perform the function of an intruder resistant fence shall be a
'security fence' as specified in Section 8.5 of T HR CI 12160 ST, version 1.0, and any additional
requirements detailed in this standard shall also apply. The preferred arrangement is the close
spaced welded mesh type.
© State of NSW through Transport for NSW 2017 Page 11 of 23
T HR EL 99004 ST Substation Fencing
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6.4. Intruder resistant fence Intruder resistant fences shall have the same configurations as a 'high security fence' as
specified in Section 8.6 of T HR CI 12160 ST, version 1.0, and shall also meet the additional
requirements detailed in this standard.
As a minimum, 2400 mm high close spaced welded mesh with 600 mm concertina short barbed
tape shall be utilised.
Note: Toppings are required for intruder resistant fences in accordance with
Section 6.7 of ENA DOC 015-2016.
In accordance with ENA DOC 015-2016, ASA prefers that the intruder resistant fence to be
constructed as a separate fence inside the boundary fence. This is to provide a higher level of
protection by restricting vehicle access to the intruder resistant fence. The minimum distance
between the two fences shall be 3 m.
Where site conditions preclude the use of two fences, the boundary fence shall be designed
and constructed as an intruder resistant fence. In this situation, traffic barriers or bollards shall
be used as appropriate to restrict vehicle access.
6.5. Internal enclosure fence For internal enclosure fence requirements, refer to AS 2067:2016 Substations and high voltage
installations exceeding 1 kV a.c.
Note: Typically, an internal enclosure fence should be an 'urban fence' as specified in
Section 8.3 of T HR CI 12160 ST, version 1.0, utilising the top and bottom rail
configuration.
6.6. Welded mesh fence construction The close spaced welded mesh shall be galvanised and powder coated prior to installation in
accordance with SPC 511 Boundary Fences. The preferred colour is black.
The welded mesh fence shall be a single layer mesh fence. The orientation of the mesh shall be
such that the horizontal mesh aperture is larger than the vertical mesh aperture as outlined in
ENA DOC 015-2016.
The construction of the welded mesh type fence shall be as follows:
• Plumb, level, and true to design position.
• The mesh shall be under tension or ensure there are no slack sections. If there are slack
sections, then a mid-rail shall be installed and fixed.
• A straining post shall be installed for each end, corner, change of direction, and acute
variation in the level of the fence. For straight runs, there shall be a straining post every © State of NSW through Transport for NSW 2017 Page 12 of 23
T HR EL 99004 ST Substation Fencing
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50 m minimum. Each straining post shall be supported by a brace in each direction of the
fence line.
• Mesh-to-mesh and mesh-to-post joins shall be with galvanised tamper resistant or locking
nuts and bolts.
• Mesh-to-mesh joins (if any) shall overlap a minimum of 200 mm. Each overlap shall have a
securing every 100 mm horizontally and 300 mm vertically.
• Any metal exposed during construction shall be coated with a two-part epoxy corrosion
inhibitor.
Refer to EL 0450708 Substations Fencing Sheet 1 Typical Construction for a typical installation
of welded mesh type fence.
6.7. Alternative fencing materials Any substation fencing design using masonry or cladding types of fencing is not preferred and
requires approval during the design phase by the Lead Electrical Engineer, ASA.
Any substation fencing design, that does not use open mesh construction shall require further
electronic intruder detection methods due to restricted visibility of the substation premises.
Metal or timber cladding may be proposed to address local aesthetic issues. The cladding
would typically be affixed to a mesh fence that complies with this standard.
6.8. Toppings Topping of concertina short-barbed tape shall be used on intruder resistant fences in
accordance with Section 8.6 of T HR CI 12160 ST, version 1.0.
The topping shall be straight up and supported by the fence posts. A stainless steel support
wire should also be installed to maintain the integrity of the barbed tape coils.
Where local conditions determine that the concertina short barbed tape cannot be installed, the
alternate topping and fence requires approval during the design phase by the Lead Electrical
Engineer, ASA and the TfNSW area responsible for security and emergency management.
Note: 'Croc top' or similar fence toppings do not meet the requirements of
ENA DOC 015-2016 for intruder resistant fences; however, they may be used as an
additional deterrent for boundary fences.
6.9. Kerbing Kerbs shall be included in the design of the fence. Kerbs prevent the integrity of the fence being
compromised due to subsidence, erosion, and burrowing. Kerbs are also known as ‘plinths’ or
‘anti-dig footings’.
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Typically, the kerb centre-line shall be directly below the fence line, with the bottom of the fence
no more than 50 mm above the top of the kerb. The kerb shall be a minimum of 125 mm wide
by 300 mm deep in clay soils. The kerb shall be a minimum of 125 mm wide by 600 mm deep in
sandy soils. The top of the kerb shall be no less than 50 mm above ground level.
If a kerb cannot be used, then a concrete path shall be constructed. This path shall extend a
minimum of 600 mm from the fence line. The path shall have a minimum depth of 75 mm and
finish flush with the existing ground levels. The bottom of the fence shall not be more than
50 mm above the concrete.
The construction of the kerb and path is as shown on EL 0450711 Substations Fencing Sheet 4
Details. The kerb and path shall be constructed in accordance with AS 3600 Concrete
Structures.
The design of kerbing and paths shall consider surface drainage issues, to minimise, for
example:
• water ponding, and
• fouling of the substation yard from silt runoff
6.10. Ground level and fence height If possible, the ground below the fence shall be level. The ground below the fence shall not be
exposed to erosion or subsidence. The fence shall be designed such that if the ground
transitions from one level to the next, climbing aids are not created.
In areas where ground level is sloped a retaining wall shall be constructed to provide support.
The retaining wall shall be designed and constructed to support the integrity of the fence. The
line of the fence shall progress down the slope in a series of level steps. The kerb or path shall
be included into the design of the retaining walls.
Where necessary, adjustments to the existing ground levels shall include surface drainage
measures to prevent water ponding.
6.11. Climbing aids
6.11.1. Intruder resistant fences
The vertical clearance of the fence above a climbing aid (which cannot be removed or
relocated), shall be a minimum of 2.4 m including the topping installed. Fence posts shall be
extended to allow for this on both sides of the climbing aid. Typical clearances shall be in
accordance with drawings EL 0450712 Substations Fencing Clearances to Climbing Aids and
EL 0450710 Substation Fencing Typical Construction.
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All potential climbing aids shall have measures to prevent unauthorised entry. The fence design
shall ensure that any climbing aid is 3 m or more away from the fence. If this is impractical, then
the following shall be considered:
• Traffic bollards or barriers – increase the height of the fence above the barrier to ensure
minimum height. Refer to EL 0450710 Substations Fencing Sheet 3 Typical Construction.
• Windowsills – place security grille or mesh flush over window so no finger or footholds are
available.
• Gate locks – the locks shall not create an external foot or hand hold. Refer to EL0450709
Substations Fencing Sheet 2 Typical Construction.
• Stairs – remove or relocate stairs, or provide increase in fence height, or do both.
Otherwise, provide a security grill or mesh around the stairs.
• Adjacent fence – where an abutting fence cannot be removed or relocated, then increase
the height of the intruder resistant fence to 2.4 m above the highest foothold. Refer to
EL 0450712 Substations Fencing Sheet 5 Clearances to Climbing Aids.
• Adjacent pole – if the pole cannot be removed or relocated then the fence shall be
redirected around the pole so that there is a clearance of at least 2 m.
• Overhanging vegetation – remove or prune back to 3 m away from the fence. If this is not
possible, trim trunk smooth to a height of 6 m to remove any climbing aids. Refer to
EL 0450712.
6.11.2. Other substation fences Where practicable, ensure structures adjacent to substation boundary and internal enclosure
fences are located and configured so as not to act as a climbing aid to the fence. The site
specific risk assessment may necessitate the use of the anti-climb methods nominated for
intruder resistant fences (refer to Section 6.11.1).
6.12. Gates Both vehicular and pedestrian gates shall be made of the same material as the fence. Each
gate shall have a concrete path or driveway provided underneath it.
The gateposts shall be of suitable strength to support the gate with reliable operation, for the
duration of the fence life. Double gates shall have a top, middle, and bottom rail and shall be
braced as shown in EL 0450709 Substations Fencing - Typical Construction - Arrangement -
Sheet 2.
The gates and posts shall be all-welded, galvanised and powder coated and be constructed in
accordance with EL 0450709. The topping for vehicle gates shall be straight up, not canted. The
topping for the pedestrian gate can be a continuance of the adjacent topping. © State of NSW through Transport for NSW 2017 Page 15 of 23
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Sliding gates are not preferred; however, they may be used as vehicular gates subject to ASA
approval.
6.12.1. Emergency egress gates
The design shall allow for the safe egress of personnel during a fire, severe equipment failure,
and other emergencies. Refer to T HR EL 99002 ST for details.
If there is insufficient space inside the substation fence for a safe area to evacuate to, then
there shall be an emergency egress gate in the substation fence to allow egress to the outside.
As part of the design process, the AEO shall prepare an emergency evacuation plan that clearly
identifies the nominated emergency gates and emergency egress pathways. The emergency
evacuation plan shall ensure that egress is to a safe location and not onto live rail lines or
roadways.
For a typical emergency egress gate, refer to EL 0455333 Substations Fencing - Typical
Construction - Emergency Egress Gate.
EL 0455333 specifies the following requirements for emergency egress gates:
• the gate shall have a transparent impenetrable barrier (typically a high strength, high
impact resistant acrylic or polycarbonate) surrounding the lock
• the gate shall have a welded plate across the gate to jamb gap on the lock side for the full
height of the gate
The lock shall be a single downward thrust action for egress, and the gate shall open in the
direction of the emergency egress. The locking tongue shall penetrate the striker plate to a
distance of a minimum of half the length of the locking tongue.
To minimise the risk of intruders being able to reach the gate release from the adjacent side
fence panel, emergency egress gates shall not be located in corners of fences.
The location of an emergency egress gate shall not interfere with the bracing required as
specified in Section 6.6.
The use of emergency egress gates shall be limited to those nominated in the emergency
evacuation plan as these gates are not as secure as those fitted with sliding bolt with padlock.
6.12.2. Hinges
The hinges shall be made of galvanised steel. The hinges shall be strong enough to ensure
reliable operation of the gate over the fence lifetime. The hinges shall require minimum
maintenance. The hinges shall be designed to ensure that the gate cannot be removed in the
closed position.
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6.12.3. Locks
The locking arrangement of gates shall be as shown in EL 0450709 Substations Fencing -
Typical Construction - Arrangement - Sheet 2.
For vehicular double gates, each gate shall be fixed by a galvanised padlock-able drop barrel
bolt (minimum 16 mm diameter) into the ground. Galvanised steel pipes shall be set into the
concrete for this purpose; refer to details shown on EL0450709. The two gates shall then be
locked together with a galvanised padlock-able sliding bar.
For pedestrian gates, the lock shall be a high security, exterior grade, sliding bolt with a
padlock. The bolt shall travel a minimum of 20 mm into the post on lock. The lock plate on the
outside of the gate shall be flush mounted and tamper proof.
The position of all locks shall be as shown on the drawings and mounted between 900 mm and
1200 mm above the ground level.
6.13. Clearance zone A 3 m horizontal clearance zone should be maintained around the substation fence. The
clearance zone should be kept free of intermediate structures, hazards, climbing aids, large
vegetation, and any form of material build-up. If the 3 m clearance is not practical, then the
maximum possible clearance is required, and any possible climbing aids are to be dealt with in
accordance with this standard.
6.14. Vegetation Any vegetation planted around the fence inside the clearance zone shall not have a potential
height greater than 300 mm. This ensures there are no areas close to the fence that allow
coverage for intruders.
7. Electrical clearance Electrical clearances to substation fences shall comply with Section 5.2 of AS 2067:2016.
As 1500 V dc is not included in the scope of AS 2067, for 1500 V dc use the clearances
specified for 11 kV ac.
If the specified clearances for mesh fencing cannot be achieved, one or all of the following shall
be carried out:
• relocate the fence to achieve the clearances
• move or insulate the live exposed equipment
• install a non-penetrable panel in the fence, in which case the reduced clearances for solid
wall construction may be used
© State of NSW through Transport for NSW 2017 Page 17 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
7.1. Non-penetrable panel The non-penetrable panel shall be as shown in EL 0450713. This panel will typically be of two
layers of compressed fibrous cement panel (2.4 m x 1.2 m x 18 mm) one on the front, and one
on the back of the steel posts. All fixings shall be countersunk type and the holes back filled with
a two part epoxy resin.
The topping over the non-penetrable panel(s) shall be continuous with the topping over the
adjacent panels.
Sufficient panels shall be installed to achieve the required electrical clearances.
Alternate materials or configurations, or both, for the non-penetrable panel may be proposed by
the AEO, and are subject to approval by ASA. The AEO shall assure the proposed option
including, but not limited to, whole-of-life costs and considerations, maintenance requirements,
and any alterations to technical maintenance plans (TMPs).
8. Substation fence earthing, bonding and isolation The design of the fence shall be coordinated with the design of the earthing system and shall
comply with EP 12 10 00 10 SP System Substation Earthing to avoid the creation of situations
in which the step or touch potentials are unacceptable, and to ensure that high earth potential
rise is not transferred beyond the zone where the potential gradient is properly controlled.
8.1. Earthing and bonding Earthing and bonding requirements for substation fencing, gate bonding, grading rings, and so
forth shall be in accordance with the TfNSW earthing standards.
Typically, substation fences are bonded to the substation earth grid. Any continuous metallic
fencing adjacent to the substation boundaries is isolated by insulated fence panels; however
fences can also be isolated or insulated where deemed appropriate.
The designer shall consider stray current, step, touch and transfer potential issues in
determining the earthing and bonding requirements for fencing and gates. Gates shall be
assessed for all operational positions.
Earth grading rings in close proximity to concrete paths shall be avoided.
8.2. Isolation and transfer potential mitigation All substation fencing and any supporting structures shall be electrically isolated from any other
conductive fencing beyond the substation boundaries. The location and number of substation
fence isolation points shall be subject to earthing design.
© State of NSW through Transport for NSW 2017 Page 18 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
The approved method for implementing fence isolation shall be through provision of an
insulated fence panel. Insulation panels are detailed in Section 11 of SPC 511, version 1.1.
Continuous reinforced concrete structures supporting uninsulated fences shall have
reinforcement isolated at points in line with any required fence isolation so as to break the
continuity of the reinforcement and maintain the integrity of the isolation point. Only a single
isolation point is required in line with the insulated fence section to maintain the integrity of the
insulated fence panel.
Approved insulating pads, ferrules and washers may be used to provide isolation between fence
panels and supporting reinforced concrete structures so long as the number of attachments
does not compromise the minimum insulation requirements.
The specification of insulation shall include measures to insulate security structures such as
fence toppings. The security structures shall not compromise the intended isolation points.
Where a continuous metallic structure is in contact with the fence, then an insulating section
shall be included in the design (of either the fence or the structure) to stop transfer potentials
through, into and out of the metallic structure.
Where an overhead wiring structure is located within 2 m of a substation fence, an insulating
panel shall be installed to achieve 2 m separation from any uninsulated fence panels.
8.3. Testing and measurement Visual inspection and step, touch and transfer potential measurements shall be used to validate
the design and installation of fence isolation and to ensure compliance. Testing of fence
isolation is mandatory if the maximum earth potential rise (EPR) at the substation is within 10%
of the allowable limits.
Continuity testing shall be conducted between the earth grid and the fence upon installation to
ensure adequate bonding has been installed. Pass and fail criteria shall be developed and
specified by the designer. Where bonding is required, more than one connection to the earth
grid shall be provided to any continuous fence section to provide redundancy.
9. Signage Signage shall be installed in accordance with T HR EL 00006 ST Electrical Power System
Signage.
In addition, if the fence construction includes barbed tape (razor wire) or palisade spikes, then
danger signs shall be installed warning of their presence.
Signs shall be placed to ensure that they are clearly visible and easily read.
© State of NSW through Transport for NSW 2017 Page 19 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
10. Construction factors During construction of a new or replacement fence, the risk of unauthorised access to the site
and to exposed electrical equipment shall be managed as part of the overall risk assessment.
This includes, but is not limited to, the following:
• the need for temporary protection measures
• monitoring the integrity of all access prevention methods
• development of safe work method statements (SWMS) or safe work instructions (SWIs) as
necessary
Identification of, and work around, buried services shall be conducted in accordance with
approved procedures. In addition, the design and construction of the fence shall consider and
manage the likelihood that the substation grading ring may be located outside the existing
substation fence line.
Refer to Section 10 of T HR CI 12160 ST, version 1.0 for more information.
11. Maintenance Substation fencing shall be inspected and maintained in accordance with the technical
maintenance plan, and Section 11 of T HR CI 12160 ST, version 1.0.
Any encroachment by vegetation shall be managed, to ensure clearances are not breached and
sighting of intruders is not impeded.
© State of NSW through Transport for NSW 2017 Page 20 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
Appendix A Additional references and drawings The list of documents and drawings in Section A.1 and Section A.2 may provide additional
information and context.
A.1. Documents AS 1725:2003 Chain-Link Fabric Security Fences and Gates
AS 4100 Steel Structures
AS/NZ 2312:2002 Guide to the Protection of Structural Steel against Atmospheric Corrosion by
the Use of Protective Coatings
AS/NZS 4534:2006 Zinc and zinc/aluminium-alloy coatings on steel wire
BS 1722-10:1999 Fences – Part 10: Specification for Anti-Intruder Fences in Chain Link and
Welded Mesh
BS 1722-14:1999 Fences – Part 14: Specification for Open Mesh Steel Panel Fences
EP 12 10 00 11 SP Distribution Substation Earthing
EP 12 10 00 21 SP Low Voltage Installation Earthing
T HR EL 12002 GU Electrolysis from Stray DC Current
A.2. Drawings The following drawings have not been AEO assured or accepted for TfNSW use; however, they
may provide additional reference material:
CV0393068 Substations Fencing Upgrades Sheet 1 Cover Sheet and Notes
CV0393069 Substations Fencing Upgrades Sheet 2 General Details
CV0393070 Substations Fencing Upgrades Sheet 3 Increase Fence Height and Barbed Tape
CV0393071 Substations Fencing Upgrades Sheet 4 Details of Gates
CV0393073 Substations Fencing Upgrades Sheet 6 Kerbing
CV0393074 Substations Fencing Upgrades Sheet 7 Locking and Bolting Details
© State of NSW through Transport for NSW 2017 Page 21 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
Appendix B Substation fencing examples The information in Section B.1 to Section B.3 provides informative guidance material to assist in
interpreting this standard.
B.1. Traction SS, section hut, or system SS – Indoor HV switchgear The site is defined by a boundary fence (see Section 5.1 and Section 6.3). This is typically
2.7 m high welded mesh, with croc top topping dependent on site risk assessment. This
includes sites where one wall of the substation building is facing the rail corridor - an extra line
of defence is recommended to deter vandalism of the SS building.
The HV switchgear and associated substation (SS) auxiliary and control equipment will be
contained within an intruder resistant building, typically not less than 3 m from the boundary
fence.
The transformers (rectifier or system or DC reactor) whether they are cable entry or bushing
entry, will be within an intruder resistant enclosure. The enclosure may be of masonry
construction, or welded mesh (Section 6.4) or a combination of both; for example, the
substation building itself may constitute one or more intruder resistant walls for the transformer
enclosure.
The 1500 V link area will be contained within an intruder resistant enclosure, typically a welded
mesh fence (Section 6.4), or contained within the substation building.
B.2. Traction SS or system SS – Outdoor HV switchgear and exposed busbars This configuration will normally only apply to pre-existing substations. Preference is for new
substations to be designed with enclosed switchgear.
The site should be defined by a boundary fence (Section 5.1 and Section 6.2), which should be
not less than 3 m from the intruder resistant fence (Section 6.4). Typically, due to site
constraints, the exposed HV equipment occupies such a significant portion of the site as to
preclude space for a separate boundary fence. However, the design for the intruder resistant
fence should attempt to accommodate the requirements of this standard. For example, the
design should attempt to constrict the alignment of the intruder resistant fence to enable the
provision for a boundary fence whilst not infringing the clearance defined in AS 2067.
© State of NSW through Transport for NSW 2017 Page 22 of 23
T HR EL 99004 ST Substation Fencing
Version 1.0 Issued date: 16 November 2017
B.3. 1500 V link or switch enclosure (free standing) The same principles detailed in Section B.2 apply for a SS yard with exposed HV conductors,
including but not limited to, the provision of an intruder resistant enclosure, and AS 2067
requirements for string line distances to exposed 1500 V conductors.
Such equipment is normally located within the rail corridor. Due to site constraints, there may
not be sufficient space for a separate boundary fence, therefore the site specific risk
assessment should consider the adequacy of any existing boundary fences, and define safe
access and egress routes for the link or switch enclosure.
© State of NSW through Transport for NSW 2017 Page 23 of 23
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