MEST 000002-03 Railway Bridges Electrical … MAY NOT BE UP-TO-DATE; REFER TO METRO INTRANET FOR THE LATEST VERSION Engineering Standard- Design Electrical Networks MEST 000002-03

PRINTOUT MAY NOT BE UP-TO-DATE; REFER TO METRO INTRANET FOR THE LATEST VERSION

Engineering Standard- Design

Electrical Networks

MEST 000002-03

Railway Bridges

Electrical Protection and Bonding

Version: 1

Issued: June 2013

Owner: Chief Engineer

Approved By:

Norm Grady

Chief Engineer

ELECTRICAL NETWORKS STANDARD

RAILWAY BRIDGES

ELECTRICAL PROTECTION AND BONDING

MEST 000002-03 Version: 1 Effective from: 18th June 2013

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Approving Manager: Chief Engineer Approval Date: 18/06/2013 Next Review Date: 18/03/2016

PRINTOUT MAY NOT BE UP-TO-DATE; REFER TO METRO INTRANET FOR THE LATEST VERSION Page 1 of 25

Approval

Amendment Record

Approval Date Version Description

18/06/2013 1 Initial issue under MTM.


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Table of Contents

1 Purpose ........................................................................................................................... 3

2 Scope ............................................................................................................................... 3

3 Abbreviations .................................................................................................................. 3

4 Definitions ....................................................................................................................... 3

5 References & Legislations ............................................................................................. 4

5.1 General ............................................................................................................................. 4

5.2 MTM Standards ................................................................................................................ 4

5.3 Rail Industry Standards .................................................................................................... 4

5.4 Australian Standards ........................................................................................................ 4

5.5 International Standards ..................................................................................................... 5

6 Related Documents ........................................................................................................ 5

7 Safety and Environment ................................................................................................. 5

8 Electrical Protection and Bonding Principles – Underbridges .................................... 5

9 Electrical Protection and Bonding Principles – Overbridges ...................................... 8

10 Retaining Walls ............................................................................................................... 9

11 Test Points – Underbridges ........................................................................................... 9

12 Appendices ..................................................................................................................... 9

Appendix A - Underbridges ............................................................................................................... 10

Appendix B - Overbridges ................................................................................................................. 21

Appendix C - Concrete Bridge Test Points ....................................................................................... 24

Appendix D - Steel Bridge Test Points ............................................................................................. 25


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1 Purpose

1.1 To define the technical requirements to protect persons and assets from failures of the traction wiring system in the proximity of bridges on the Infrastructure Lease.

1.2 To define the principles and approaches to be applied to the design and construction of bridges and other structures on the Infrastructure Lease to protect the assets against the effects of stray current corrosion.

2 Scope

2.1 This Standard provides the principles and the physical requirements to be incorporated into railway bridges and structures, both underbridges and overbridges in regards to electrical protection and bonding, to protect against electrocution and stray current corrosion.

2.2 This Standard applies to the design and construction of all new bridges, including bridge renewals, for the metropolitan railway.

2.3 This Standard also applies to works on the Infrastructure Lease and to works undertaken on other land which are intended to expand or enhance the provision of passenger services and to form part of the Infrastructure Lease.

2.4 Additionally, as protection against stray current corrosion requires bridge components to be designed and built with specific electrical continuity and isolation of various steel and metallic sections, bridges identified as being on lines that are to be electrified within the life of the structure shall be designed and constructed in accordance with this Standard.

3 Abbreviations

MTM Metro Trains Melbourne

PTV Public Transport Victoria

VRIOGS Victorian Rail Industry Operators Group Standards

4 Definitions

Infrastructure Lease

Is defined as the meaning in the Franchise Agreement

Shall Is used as the descriptive word to express a requirement that is mandatory to achieve conformance to the standard.

Should Is used as the descriptive word to express a requirement that is recommended in order to achieve compliance to the standard. Should can also be used if a requirement is a design goal but not a mandatory requirement.

Underbridges These are bridges supporting the track and passing over waterways, roadways, pathways, flood plains, etc.


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Overbridges These are bridges over the track, carrying vehicular traffic, and may include provision for pedestrians.

Footbridges These are bridges over the track, carrying pedestrian traffic only, and may be freestanding or combined with an overhead booking office.

5 References & Legislations

5.1 General

5.1.1 The isolation and bonding of conductive materials on bridges to provide protection to persons on and in the proximity of railway bridges against failure of the traction wiring system and the protection of structures against stray current corrosion shall be designed and constructed in accordance with this standard and relevant MTM and Australian, Rail Industry and International Standards.

5.1.2 The design and construction of the electrical protection and bonding for bridges shall comply with all legislative requirements and codes and specifically the Electrical Safety Act 1998 as amended and the requirements of the Victorian Electrolysis Committee.

5.2 MTM Standards

Document Number Title

L0-SQE-PLA-005 Environmental Management Plan

MEST 070000-01(1) Train Maintenance Buildings Electrical Systems Earthing and Bonding

MEST 000002-02 Overhead Line Electrification

5.3 Rail Industry Standards

Nil

5.4 Australian Standards


AS 5100.5 Bridge design Part 5: Bridge design - Concrete


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5.5 International Standards


EN 50122-1 Railway Applications - Fixed Installations - Electrical Safety, Earthing and the Return Circuit - Part 1: Protective Provisions Against Electric Shock

EN 50122-2 Railway Applications - Fixed Installations - Electrical Safety, Earthing and the Return Circuit - Part 2: Provisions Against the Effects of Stray Currents Caused by D.C. Traction Systems

6 Related Documents

The following drawings form part of this Standard.

STD_E0109 Typical Arrangement for Electrical Protection of Reinforced Concrete Bridge Piers and Beams

STD_E0110 Typical Arrangement for Electrical Test Arrangement for Direct Fixed Track on Bridge or Ground Slab

STD_E0111 Electrical Protection of Reinforced Concrete Structures with Direct Fixed Rail Track – Typical Test Point

7 Safety and Environment

7.1 Safety and risk assessments shall be undertaken for the electrical protection and bonding for bridges, addressing all areas of specification, design, construction and maintenance of the bridge, including structure, protection against electrocution and stray current corrosion.

7.2 Risk assessments specifically addressing the electrical protection and bonding for the bridge shall be undertaken at the preliminary design stage in conjunction with the bridge structural designers. Where appropriate, the bridge constructors shall also be involved in the risk assessments.

7.3 Where new materials are to be introduced with the design and construction of the electrical protection and bonding, the materials shall be subject to type approval for use on the metropolitan train network.

7.4 The design, construction and maintenance of the bridge, the electrical protection and bonding materials and related equipment shall comply with the MTM Environmental Management Plan.

8 Electrical Protection and Bonding Principles – Underbridges

8.1 Inherent in the design of direct current traction systems is the fact that the protection against fault currents only applies to faults between the positive conductors and the return current path formed by the rails. There is the potential under fault conditions for metallic

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objects in the proximity of the railway to become energised at high voltage and expose persons to dangerous voltages.

8.2 The rails of the traction supply system are not earthed but are near earth potential due to the placement of the rails on the earth.

8.3 Current leaking from the rails into metal and reinforced concrete structures will cause corrosion that has the potential to damage the structural integrity of the structure.

8.4 There are many principles under pinning the approach to the protection of persons from failure of the traction wiring system and the control of stray current corrosion. EN 501221-1 and 501221-2 are the primary standards outlining the requirements. AS 5100 requires the design to consider protection against corrosion. These principles and the required response to incorporate them into bridge structures supporting the railway are as follows.

8.4.1 The placement of overhead structures on bridges is to be avoided where possible. Where necessary, the overhead structures are to be mounted on piers and abutments and be isolated from the bridge deck, handrails, walkways and all metallic items. The overhead structure mounting bolts shall be electrically continuous with the reinforcing of the structure on which it is mounted.

8.4.2 The low potential end of overhead wiring insulators are to be provided with a direct path to rail such that in the event of insulator failure the substation circuit breakers detect the fault and isolate the line.

8.4.3 Failure of the overhead wiring may result in the cables falling to ground. An area set by the centre line of the track and 4 metres either side of the centre line is defined as the “drop zone” within which consideration is to be given to the consequence of overhead wiring failure.

8.4.4 Where there are metal structures in the proximity of overhead wiring that may be contacted by failed overhead wiring, the distance that the metal may be energised will be limited by gaps or isolation of the structure.

8.4.5 Walkways and similar purpose metal structures attached to the bridge in the proximity of overhead wiring that may be contacted by failed overhead wiring which are only accessible to trained employees of Metro Trains may, subject to risk assessment, not be provided with a connection to rail capable of carrying the traction system fault current.

8.4.6 Metal structures in the proximity of overhead wiring that may be contacted by failed overhead wiring which are accessible to passengers and members of the public shall be provided with a connection to rail capable of carrying the traction system fault current.

8.4.7 To mitigate against stray current corrosion, the rails of the traction supply system are not earthed. Specifically, in the proximity of bridges, rails shall not be connected to earth. Intermittent temporary connections of the rails to earth may be made at substations and other specific locations as protection against excessive rail to earth voltages.

8.4.8 Rails on bridges shall be isolated from all metal of the structure.

8.4.9 The steel reinforcement in bridge piers and abutments shall be welded to form an electrically continuous low resistance structure to protect against bar to bar corrosion from stray current and to provide a large metal mass for dispersion of any


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current that may enter the structure. The reinforcing shall be taken to be at earth potential.

8.4.10 Reinforced concrete bridge beams shall be designed and constructed such that the reinforcing is an electrically continuous low resistance structure and the beam electrically isolated from the rails and earth. The reinforcing shall be welded to be electrically continuous. Stressing cables are considered protected within the electrically continuous welded reinforcing and can remain free of connection with the reinforcing. The ends of stressing cables and any exposed metal are to be covered and insulated with permanent material such as epoxy resin to prevent any contact with any other material. The beams shall sit on electrically isolating bearings and at the ends be isolated from earth and earthed structures by non conducting materials. The rails are to be on ballasted track. The combination of ballasted track, reinforcing and stressing cables isolated within the beam and the beam isolated from earth provides the best protection from stray current entering the structure.

8.4.11 Metal handrails and walkways on bridges accessible only to trained employees of Metro Trains shall be constructed in sections with a gap of at least 100mm between sections to limit the distance of the metal that may become energised under fault condition. The section lengths may be from three metres to 70 metres maximum. Handrail or other safety barrier lengths shorter than or equal to the bridge span lengths are preferred.

8.4.12 Metal handrails and walkways on bridges accessible to passengers and members of the public shall be constructed in one electrically continuous length for the bridge with a connection to rail capable of carrying the traction system fault current.

8.4.13 Metal handrails and walkways shall be electrically isolated from the reinforcing in bridge beams and decks. The metal handrails and walkways shall not be earthed and shall be isolated from fences and walkways at the ends of the bridge. The end of bridge isolation shall be provided by two 100mm gaps 2000 to 2400mm apart or by a panel of electrical non conductive material, 2000mm or more in length.

8.4.14 Bridges constructed with steel beams supporting ballasted tracks shall have the bridge deck electrically connected to the beams. Cast insitu concrete decks shall have the reinforcing steel welded to the steel beams by connections to reinforcing starter bars. Steel decks shall have clean metal to metal contact with the beams. The steel beams shall sit on electrically isolating bearings and at the ends be isolated from earth and earthed structures by non conducting materials. The ballasted track, the steel beams isolated from earth and the mass of the steel structure provide the protection against stray current corrosion.

8.4.15 For reinforced concrete bridge beams, direct fixed track to a concrete deck requires another level of insulation to be provided to protect the structure in the event of the failure of the track mounting insulation. The concrete slab on which the track is fixed is to be separated from the concrete bridge beam. The reinforcing in the slab shall be welded in a grid pattern and be proven to be isolated from the reinforcing in the


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beam. To permit testing over the life of the structure to prove that the integrity of the insulation between the rails and the slab reinforcing is sound, a test cable is bonded to the reinforcing and brought out of the structure to a protected location. The rails shall be fitted with insulated rail joints, normally bonded around, to enable periodic testing of the rail to reinforcing resistance. The insulated rail joints shall be within the ballasted track and a minimum of one metre from the ends of the approach slabs to the bridge. The bridge structure shall sit on electrically isolating bearings and at the ends be isolated from earth and earthed structures by non conducting materials.

8.4.16 For steel bridge beams with direct fixed track on a cast insitu concrete slab, the reinforcing in the slab is to be welded to the steel beams by connection to the reinforcing starter bars. The reinforcing is welded in a grid pattern as well as being welded to the main steel beams. The mass of the steel structure provides protection in the event of a connection between rail and the reinforcing. Testing over the life of the structure to prove that the integrity of the rail to reinforcing insulation is sound is performed by measurement of the resistance between the rails and the steel bridge beams. The rails shall be fitted with insulated rail joints, normally bonded around, to enable periodic testing of the rail to reinforcing resistance. The insulated rail joints shall be within the ballasted track and a minimum of one metre from the ends of the approach slabs to the bridge. The bridge structure shall sit on electrically isolating bearings and at the ends be isolated from earth and earthed structures by non conducting materials.

Note: With reference to 8.4.15 and 8.4.16, removal of bonds around insulated rail joints to be performed with tractions services suspended to protect against electrification.

8.4.17 For steel bridge beams supporting precast concrete sections, the precast sections are to be formed with the reinforcing welded to be electrically continuous. The precast sections are mounted on the steel beams without electrical insulation. The system relies on the steel beams being on electrical isolating bearings and the ballast or epoxy fixing for rail isolation. The precast sections are to be limited in size to limit the consequence of failure. A failure of one of the precast sections is not regarded as significant as failure of a major beam or slab section.

8.5 Appendix A provides further details on the requirements for underbridges. The Appendix also details the requirements for track direct fixed to a slab on ground structure.

9 Electrical Protection and Bonding Principles – Overbridges

9.1 Overbridges fall into three categories being:

9.1.1 Those high above the suspension points of the overhead catenary where there is little likelihood of a failure of the overhead impacting the structure,

9.1.2 Bridges that are within the area formed by a line joining the catenary suspension points and 300mm above the catenary and

9.1.3 Bridges supporting the overhead wiring.

9.2 Concrete bridges not supporting the overhead wiring are at little risk of having high potentials impressed on them or of passing stray current in the event of overhead wiring failure contacting the bridge.

9.3 Concrete bridges supporting the overhead wiring require secondary insulation of the suspension and registration points to protect against stray current corrosion.


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9.4 Steel bridges within the area formed by a line joining the catenary suspension points and 300mm above the catenary and steel bridges supporting the overhead wiring have the potential under failure conditions to impress high potentials on the bridge structure and any conductive materials attached to the structure. The limits of the steel bridge are to be contained to that necessary and any adjacent fences shall be isolated from the bridge by two 100mm gaps 2000 to 2400mm apart or by a panel of electrical non conductive material, 2000mm or more in length.

9.5 Steel bridges accessible to passengers and members of the public shall be constructed in one electrically continuous length with a connection to rail capable of carrying the traction system fault current

9.6 Appendix B provides further details on the requirements for overbridges.

10 Retaining Walls

10.1 Where it is necessary for a mast or structure supporting overhead wiring to be mounted on a retaining wall, wing wall or similar structure, the mounting bolts shall be electrically continuous with the reinforcing of the structure on which it is mounted.

10.2 The reinforcing in the retaining, wing wall or similar structure shall be welded to be electrically continuous. The welding is to occur at a minimum of 2 metre square grid points.

11 Test Points – Underbridges

11.1 Concrete and steel bridges supporting rail track are to be fitted with test points to enable the integrity of the rail to structure minimum prescribed insulation resistance to be tested. Appendix C gives the required test for concrete structures and Appendix D for steel structure.

12 Appendices

Appendix A Underbridges

Appendix B Overbridges

Appendix C Concrete Bridge Test Points

Appendix D Steel Bridge Test Points


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Appendix A - Underbridges

ELEMENT SUB ELEMENT REQUIREMENT RATIONALE

1 Reinforced concrete piers supporting railway

n/a To be separated from rail

Reinforcement joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points

All steel in piles, pile caps and the entire pier structure to be made electrically continuous with a minimum of two separate welded connections between each steel section.

Reinforcing not exposed to rail leakage currents

Any leakage over the long term from a large steel mass

2 Reinforced concrete bridge deck supporting rail track on ballast

Deck Beam Reinforcing in beam to be to be electrically continuous joined by welding – welding to occur at a minimum of 2 metre square grid points

Reinforcing in beam to be isolated from all rail to earth potential

Stressed beams to have the exposed ends of stressing cables cleaned and completely sealed with epoxy resin

Beams to be supported on insulating bearings

Beams at ends not to be connected to earth or other concrete or steel at earth potential – insulated cover plates required

Insitu concrete reinforcement welded to starter bars in beam

Insitu concrete to have reinforcement joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points

Reinforcement within insitu concrete over concrete beams to be isolated from all conducting materials (handrails, walkways)

Reinforcing within structure isolated from all sources of current

Isolated beam bearings limits potential for rail current flow to earth

Interconnected mass of steel in structure provides protection against stray current

Reinforcement steel welding prevents bar to bar corrosion




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3 Steel handrail with concrete walkway

Handrail mounted on bridge deck

Not connected to reinforcing of deck

Maximum length of continuous handrail 70 metres

100mm gap between each 70 metre section of handrail

2 metre long non conductive panel or two 100mm gaps 2000mm apart at ends of bridge

Access to walkway to be restricted to railway employees

Bridge only accessible to rail employees

Integrity of isolation of reinforcement in deck not breached

If overhead falls on handrail exposure limited

4 Reinforced concrete bridge deck supporting rail track on ballast

Steel handrail with steel walkway

Neither handrail or walkway connected to reinforcing of deck

Maximum length of continuous handrail and walkway 70 metres

100mm gap between each 70 metre section of handrail and walkway

2 metre long non conductive panel or two 100mm gaps 2000mm apart at ends of bridge

Access to walkway to be restricted to railway employees

Bridge only accessible to rail employees

Integrity of isolation of reinforcement in deck not breached

If overhead falls on handrail or walkway exposure limited




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5 Overhead wiring support structure

Only to be placed on bridge if unavoidable

If required must only be mounted on bridge pier

Overhead structure must be electrically continuous with pier reinforcing

Must not be in contact with bridge deck or any metal on bridge (handrail/walkway)

Single polymeric insulators for catenary and contact wires

Spark gap structure to rail

Pier reinforcement must be joined by welding and be electrically continuous

Highest risk is damage to bridge deck structure and current fault and leakage paths keep isolated from deck

Leakage current across polymeric insulators negligible

Fault current will flow to rail through spark gap

Interconnected mass of steel in pier structure provides protection against exposure to short term rail to earth current

6 Signal Trunking Steel trunking not permitted

Where steel trunking is installed to the edge of the bridge it is to be isolated from the bridge including concrete, handrails and steel walkways to a level of 3KV (gap)

Non conductive conduits or concrete trunking on the bridge structure permitted

Remove possibility of fault current flowing in trunking and impressed high voltage on low voltage cables

7 3rd

Party Services Only to be placed on bridge if unavoidable

If necessary must be insulated from bridge structure to a level of 3kV

Must not be on the upper surface of the bridge

Reduce as far as is practical the potential for current to enter services

8 Reinforced concrete Abutments

n/a To be separated from rail

reinforcement joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points

Reinforcing not exposed to rail leakage currents

Any leakage over the long term from a large steel mass




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9 Reinforced concrete slab supporting direct fixed rail track integral to bridge structure

Bridge beams formed by reinforced concrete

n/a Reinforcement in slab joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points

Reinforcing in slab to be isolated from all rail potential

Reinforcing in beam to be to be electrically continuous joined by welding – welding to occur at a minimum of 2 metre square grid points

Primary support beam(s) supported on insulating bearings


Reinforcement within slab to be isolated from all conducting materials (handrails, walkways, other reinforcing)

70mm2 insulated copper cable to be cad welded to

reinforcing in slab and brought out to a protected and covered location to form a test point

Test points to be provided within 2 metres of the ends of each slab and at 100 metre intervals

Test points to be sealed against moisture ingress

All rails supported on slab track to be fitted with insulated rail joints at the ends of the slab with removable bonds for initial and routine tests of rail to earth insulation

Overhead structures to be on piers and clear of slab structure

[Maximum length of continuous handrail and walkway to be 70 metres as above]

The rails and their fixings are isolated from the slab reinforcing

The reinforcing in the track slab is isolated from the supporting beams and the supporting beams are isolated from earth.

Reinforcing in slab isolated from all other conductive material

Slab test points provided against which isolation of rails from structure can be tested

Rails can be tested for failure of insulation once isolated at rail joints




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10 Reinforced concrete slab supporting direct fixed rail track integral to bridge structure

Bridge beams of steel

n/a Slab reinforcement joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points


Reinforcing in slab connected to main steel beams through starter bars welded in a 2 metre square grid



Reinforcement within slab to be isolated from other conducting materials (handrails and walkways)

70mm2 insulated copper cable to be cad welded to

reinforcing and brought out to a protected and covered location to form a test point

Test points to be provided within 2 metres of the ends of each slab and at 100 metre intervals

Test points to be sealed against moisture ingress


Overhead structures to be on piers and clear of slab beams and slab deck structure

[Maximum length of continuous handrail and walkway to be 70 metres as above]

The mass of the steel bridge structure provides short term protection against rail current leakage.

Reinforcing in slab connected to main steel structure

Slab test points provided against which isolation of rails from structure can be tested





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11 Steel bridge with concrete deck supporting rail track on ballast

n/a Reinforcing in concrete connected to main steel structure through starter bars welded in a 2 metre square grid


All of deck structure at ends not to be connected to earth or other concrete or steel at earth potential – insulated cover plates required

Separate beams and bridges on common cross heads to be electrically bonded together with two 70mm

2 insulated copper cables

Overhead structures to be on piers and clear of structure

Fences at bridge ends to have 2m long insulating panel or two 100mm gaps spaced 2m apart to bridge structure


Arrangement of electrical connections and isolations of steel handrails and walkways on bridge dependent upon design of structure




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12 Steel bridge with precast concrete deck sections supporting rail track on ballast

n/a Reinforcing in precast sections welded together in a 2 metre square grid.

Minimum 50mm concrete cover over precast reinforcing







Damage from electrolysis action limited to precast sections





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13 Steel bridge with precast concrete deck sections supporting direct fixed rail track integral to bridge structure

n/a Reinforcing in precast sections welded together in a 2 metre square grid.

Minimum 50mm concrete cover over precast reinforcing

Direct fixed rail mountings to be formed without connection to or touching reinforcing

Drilled holes for direct track fixed fittings to be to be clear of reinforcing and hold down bolts to be epoxy filled into slabs







Damage from electrolysis action limited to precast sections





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14 Steel bridge with steel deck supporting rail track on ballast

n/a Primary support beam(s) supported on insulating bearings











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15 Reinforced concrete slab supporting direct fixed rail track on ground

n/a Slab reinforcement joined by welding – to be all electrically continuous – welding to occur at a minimum of 2 metre square grid points


Reinforcing to be earthed to copper earth mat by 70mm

2 insulated copper cable cad welded to

reinforcing at one location

Cable to be accessible for inspection and test

Slab to have a maximum length of 100 metres

Abutting slabs to be electrically isolated from each other

Slab ends to be isolated from any metal objects in soil

Handrails, walkway and any other metal fittings not to be connected to reinforcing of slab

Copper cable and earth mat to be protected by cover against damage and vandalism

Cover to cable and earth mat to be sealed against moisture ingress


[Maximum length of continuous handrail and walkway to be 70 metres as applies to bridge]

Slab earthed to provide test point against which rails can be tested


Earth mat resistance to be less than 5 ohms

For construction with abutting slabs, insulated rail joints are only required at the ends of the outer slabs




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16 Overhead wiring support structure

Only to be integral with slab if unavoidable

Overhead structure must be electrically continuous with slab reinforcing

Must not be in contact with any metal on slab (handrail/walkway) – 100mm gap minimum

Single polymeric insulators for catenary and contact wires

Spark gap structure to rail

Slab reinforcement must be welded and electrically continuous

Leakage current across polymeric negligible

Fault current will flow to rail through spark gap

Interconnected mass of steel in slab structure provides protection against exposure to short term rail to earth current




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Appendix B - Overbridges ELEMENT CONDITION REQUIREMENT RATIONALE

Concrete bridge Not supporting overhead wiring and above a line joining the catenary supports of the structures either side of the bridge

Structural requirements – Nil (*) Failure of wiring or pantograph entanglement extremely unlikely to impact structure

Bridge soffit at a height well above the overhead wiring

No supporting insulator to fail

Concrete bridge Not supporting overhead wiring and below a line joining the catenary supports of the structures either side of the bridge and a minimum of 300mm above the catenary

Steel protective barriers over wiring and any other metallic structures on bridge inaccessible to persons

No exposed 3rd

party assets

Structural requirements - Nil (*) Failure of wiring or pantograph entanglement may contact structure

Failure of wiring or pantograph entanglement does not place unsafe potentials on structure with risk to persons or 3

rd property assets


Metallic protective barriers over overhead wiring not accessible to persons

Concrete bridge Supporting overhead wiring

No metallic structures on bridge accessible to persons

No exposed 3rd

party assets

Structural requirements – Nil (*)

Overhead supported with secondary insulation insulated to a value of 3000V

Failure of supporting insulators, wiring or pantograph entanglement may contact structure

Failure of overhead system does not place unsafe potentials on structure with risk to persons or 3

rd property

assets

Metallic protective barriers over overhead wiring not accessible to persons

Isolation from bridge structure for electrolytic corrosion protection

Positive fault path for insulator failure




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ELEMENT CONDITION REQUIREMENT RATIONALE

Steel bridge Not supporting overhead wiring and above a line joining the catenary supports of the structures either side of the bridge

Structural requirements - Nil (*) Failure of wiring or pantograph entanglement extremely unlikely to impact structure

Bridge soffit at a height well above the overhead wiring


Steel bridge Not supporting overhead wiring and below a line joining the catenary supports of the structures either side of the bridge and a minimum of 300mm above the catenary


Bridge to be diode connected to rail

Bridge to be isolated at ends from metallic items

Lighting on bridge insulated to a level of 3000V to protect direct fault current flowing into L&P system


Failure of wiring or pantograph entanglement may contact structure

and place unsafe potentials on structure with risk to persons or 3

rd

property assets

Metal area raised to high potential limited to bridge

Steel bridge Not supporting overhead wiring and below a line joining the catenary supports of the structures either side of the bridge and a minimum of 300mm above the catenary

3rd

party assets on bridge





3rd

party assets to be in protective material insulated to a value of 3000V


Failure of wiring or pantograph entanglement may contact structure

and place unsafe potentials on structure with risk to persons or 3

rd

property assets





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ELEMENT CONDITION REQUIREMENT RATIONALE

Steel bridge Supporting overhead wiring

No 3rd








Failure of supporting insulators, wiring or pantograph entanglement may contact structure and place unsafe potentials on structure with risk to persons or 3

rd property assets




Steel bridge Supporting overhead wiring

3rd







3rd

party assets to be in protective material insulated to a value of 3000V


Failure of supporting insulators, wiring or pantograph entanglement may contact structure and place unsafe potentials on structure with risk to persons or 3

rd property assets




(*) Refers to modifications such as the welding of reinforcing and insulating materials additional to the structural design provided for electrical protection purposes




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Appendix C - Concrete Bridge Test Points

ELEMENT TEST REQUIRED TEST POINT RATIONALE

Rails – all bridges Isolation of rails from structure Not required Visual inspection

Piers and Abutments Proof of continuity of reinforcing Not required. Test performed before concrete pour

Continuous mass of steel in structure

Bridge beam Proof of continuity of reinforcing Not required. Test performed before concrete pour


Test point becomes a potential risk over the life of the structure for corrosion

Handrails and walkways Insulation test (megger) section to section and to overhead masts

n/a Design and construction to ensure that mounting of handrails and walkways do not connect to reinforcing. See above test point in beam not provided

Overhead wiring support structure Proof of continuity of reinforcing with hold down bolts and reinforcement in pier

Not required. Test performed before concrete pour


Reinforced concrete slab supporting direct fixed rail track integral to bridge structure

Proof of continuity of reinforcing

Proof of isolation of rails from reinforcing over life of structure

Test performed before concrete pour

Test point per slab section to test rail to reinforcing connection


Ability to test rail to reinforcing steel isolation over the life of the structure

Reinforced concrete slab supporting direct fixed rail track on ground

Proof of continuity of reinforcing

Proof of isolation of rails from reinforcing over life of structure

Test performed before concrete pour

Test cable with earth connection to directly earth reinforcing and form long term test point


Ability to test rail to reinforcing steel isolation over the life of the structure




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Appendix D - Steel Bridge Test Points

ELEMENT TEST REQUIRED TEST POINT RATIONALE

Bridge structure Isolation of rails from structure Not required Visual inspection

Isolation from fences and all

metallic services and items on or

adjacent to bridge

Not required Electrical connectivity available for test

purposes on structure