eps-03000 grounding and bonding

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ELECTRIFICATION PERFORMANCE SPECIFICATIONS

Final Version 7 – October 2014

EPS-03000 Grounding and Bonding

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REVISION HISTORY:

Date Version Purpose

Mar 23, 2012 0X First issue as stand-alone documentJune 15, 2012 02 Update based on Mx Submittal ReviewOct. 3, 2012 03 Update based on Mx Submittal ReviewOct 26, 2012 03 Update based on Mx Submittal Review

Nov 12, 2012 04Corrected error in revision level (amended V03 toread V04) and revised issue date. No changes madeto the content of the document.

December 16,2013

05 Update based on Mx Submittal Review

April 14, 2014 06 Update based on Mx Submittal ReviewOctober 28, 2014 07 Restore changes due to technical feedback

Parsons Brinckerhoff2300 Yonge Street, 20 th FloorToronto, Ontario M4B 1E4Canada

http://www.metrolinx.com/en/


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TABLE OF CONTENTS

1. Purpose ........................................................................................................................ 6

2. Scope ........................................................................................................................... 7

3. Reference Documents ................................................................................................. 8

3.1 Normative Documents .................................................................................... 9

4. Responsibilities ......................................................................................................... 10

5. General Data ............................................................................................................. 11

5.1 General Requirements ................................................................................... 11 5.2 Hazards and Electromagnetic Interference ................................................... 13

5.2.1 Direct Contact ........................................................................................... 13 5.2.2 Indirect Contact ......................................................................................... 13 5.2.3 Lightning ................................................................................................... 14 5.2.4 Electromagnetic Compatibility ................................................................. 14

5.3 Step and Touch Voltage ................................................................................ 15 5.4 Impact of DC Traction Systems in the Vicinity............................................ 17 5.5 System Earth ................................................................................................. 18

5.5.1 Grounding Network Configuration ........................................................... 18 5.5.2 Connections............................................................................................... 20 5.5.3 Grounding Bus Bars .................................................................................. 20 5.5.4 Non-buried Grounding Conductors .......................................................... 21 5.5.5 Publicly Accessible Locations .................................................................. 21

5.6 Special Requirements for 1x25 kV AC System ............................................ 22

6. Grounding and Bonding ApplicatIOns – Traction Return Current .......................... 23

6.1 General Principles ......................................................................................... 23 6.1.1 Bonding at Insulated Joints ....................................................................... 24 6.1.2 Static Wire (Aerial Earth or Ground Wire) ............................................... 24 6.1.3 Track Bonding .......................................................................................... 25 6.1.4 Return Cables ............................................................................................ 26 6.1.5 Current Return Monitoring ....................................................................... 26

6.2 Traction Power Facility Grounding .............................................................. 26 6.2.1 General ...................................................................................................... 26



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6.2.2 Grounding Grid ......................................................................................... 28 6.3 Stations and Service Buildings Grounding ................................................... 29

6.3.1 Stations and Sidings .................................................................................. 29 6.3.2 Facility Buildings ...................................................................................... 32 6.3.3 Other Equipment in Stations ..................................................................... 33

6.4 Bridges Grounding ........................................................................................ 34 6.4.1 Existing Bridges ........................................................................................ 34 6.4.2 New Bridges.............................................................................................. 34 6.4.3 Structure Continuity .................................................................................. 35

6.4.4 Structure Grounding.................................................................................. 35 6.5 Grounding and Bonding of Metallic Components ........................................ 37 6.5.1 OCS Support Structures ............................................................................ 37 6.5.2 Overhead Contact Line Zone .................................................................... 37 6.5.3 Grounding and Bonding of Structures - General ...................................... 40 6.5.4 Aerial Structures (Viaducts and Overpasses) ........................................... 40 6.5.5 Track Support Structure ............................................................................ 42 6.5.6 Trenches, Retaining Walls, and Retained Fill Structures ......................... 44 6.5.7 Tunnels (As Applicable) ........................................................................... 45 6.5.8 Screen, Noise, Wind, and Safety Barriers................................................. 46

6.5.9 Fence and Gate Grounding ....................................................................... 46 6.5.10 Third-Party Grounding Interface .............................................................. 47

6.6 Grounding and Bonding of Signalling and Communications Equipment .... 48 6.6.1 Signalling System Equipment and Structures ........................................... 48 6.6.2 Cross Bonding ........................................................................................... 49 6.6.3 Communications System Equipment and Structures ................................ 54

6.7 Lightning Protection ..................................................................................... 56 6.8 Rolling Stock Maintenance Facilities ........................................................... 57

Appendix A: List of Standards ......................................................................................... 58

Appendix B: Definitions ................................................................................................... 63

Appendix C: Abbreviations and Acronyms ...................................................................... 70



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LIST OF TABLES

Table 1: Reference Documents ........................................................................................... 8

Table 2: Durations of Maximum Permissible Touch Voltages ........................................ 16

LIST OF FIGURES

Figure 1: General Grounding System Layout ................................................................... 19

Figure 2: Cross-Section of Two-Track Cantilever Showing Location of Static Wire ...... 25 Figure 3: Layout of a Typical Grounding Arrangement at Passenger Station Platforms . 30

Figure 4: Typical Overhead Structure Grounding and Bonding Schematic ..................... 36

Figure 5: Overhead Contact Line Zone and Pantograph Zone ......................................... 38

Figure 6: Long, Short, and Double Combs ....................................................................... 43

Figure 7: A, B, and C Bonds and Cross Bond Configurations ......................................... 51

Figure 8: Drain Bond Configuration ................................................................................. 51



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2. SCOPE

The grounding and bonding system designs shall provide the means to carry electriccurrents into the earth, under both normal and fault conditions, without exceedingoperating and equipment limits or adversely affecting continuity of service. Adequate

bonding shall be designed and installed throughout the entire electrified system to provide proper return circuits for the normal traction power currents and fault currents,with grounding connections as detailed in these criteria.

This section provides the specifications for the grounding and bonding design of allaffected sites. The sites, to be provided with grounding grids, mats, or rods, include thetraction power facility (TPF) high, medium, and low voltage (HV, MV, and LV,respectively) switchgear, traction power transformers, autotransformers, auxiliarytransformers, disconnects, buses, cables and feeders, alternating current (ac) equipmentenclosures and pre-packaged building frames, OCS structures, and facility buildings,including stations.



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3.1 Normative Documents

Grounding and bonding is to be designed and implemented primarily in accordance withthe following standards as applicable:

1. CAN/CSA C22.2 No.0.4, Bonding and Grounding of Electrical Equipment(Protective Grounding).

2. CAN/CSA C22.3 No.2, General Grounding Requirements and Groundingrequirements for Electrical Supply Stations

3. CAN/CSA C22.2 No.8 – M91 (Reaffirmed 2003) Railway ElectrificationGuideline Standard

4. CEA report 249 D541 Simplified Rule for Grounding Customer OwnedHigh Voltage Substations

5. IEEE 80: Guide for Safety in ac Substation Grounding;

6. EN 50122-1: Railway Applications, Fixed Installations – ProtectiveProvisions Relating to Electrical Safety and Grounding;

7. IEC 60479: Effects of Current on Human Beings and Livestock – Part IGeneral Aspects; and

8. NFPA 780: Standard for Lightning Protection Systems.

9. Ontario Electrical Safety Code, 25 th Edition, 2012



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4. RESPONSIBILITIES

The grounding and bonding plan, and specifications are the responsibility of the SystemsEngineering Team. It is the responsibility of all users of this document to:

Develop detailed specifications and designs based upon the principles outlined inthis document;

Support all design work with back-up calculations which shall be made available

to Metrolinx on request; and

Inform Metrolinx in the event of any conflict between the contents of thisdocument and any other document produced for the Metrolinx Electrification

project.



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5. GENERAL DATA

5.1 General Requirements

The grounding and bonding system designs shall provide the means to carry electriccurrents into the earth, under both normal and fault conditions, without exceeding anyoperating and equipment limits, without thermal degradation or mechanical breakdown,and without adversely affecting continuity of service. Adequate bonding shall bedesigned and installed throughout the entire electrified system to provide proper return

circuits for the normal traction power currents and fault currents, with groundingconnections as specified herein without affecting life and/or property.

All grounding and bonding designs shall be coordinated with the various disciplinedesigns, including civil, architectural, electrical and electronic, mechanical, and

plumbing, traction power supply and distribution, communications, and signalling. Allgrounding and bonding designs shall be coordinated with stray current and corrosioncontrol measures, as well as the electromagnetic compatibility (EMC) andelectromagnetic interference (EMI) requirements, so that the respective designs do notconflict and render other systems ineffective. Refer to clauses 5.2.3 and 5.4 for

additional grounding and bonding requirements for lightning protection and in thevicinity of direct current (dc) systems respectively.

Normally non-current-carrying-conductive parts, examples being conduit, cable trays,handrails, and trackside fencing, shall be electrically bonded to provide a continuouselectrical path, and shall be permanently and effectively grounded. Grounding systemdesigns shall include grounding individual items, and dividing the length of normallynon-current-carrying-conductive entities into sections, with each section grounded at onlyone point. Sizes of grounding and bonding conductors shall be selected in accordancewith the latest version of the applicable codes (e.g. CSA, OESC, NESC, and CEC).

Ground resistance at each grounding location shall be less than or equal to the valuespecified in the applicable code.

An electrical safety analysis shall take in to account criteria for the ground potential rise(Refer to IEEE Standard – 80). The analysis shall be undertaken to assess which normallynon-current carrying conductive parts need to be grounded and bonded, and theappropriate method of implementation shall be identified to ensure that the touch and step

potentials are within permissible limits.



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The design of each large facility or building, such as the TPF, shall include a ground grid.Wayside houses shall be grounded by means of one or more interconnected ground rods.Where ground grids are used, the design shall adhere to the following requirements:

1. Ground grid design shall be based on local soil resistivity under all soil conditionsthat exist in practice (e.g., wet, dry, and frozen conditions) and the calculationsshall comply with IEEE standards (e.g., 80, 142, and 1100) and theCSA/OESC/CEC/NESC rules as applicable. Ground grids shall be constructedfrom an assembly of driven ground rods and bare metal conductors. A continuousloop of the grounding conductor(s) shall surround the perimeter of each facility or

building. The perimeter fence and gates, if provided, shall be effectively bondedwith the grounding loop at frequent intervals, and within this loop, the conductorsshould be laid in the form of a grid. At the cross-connections, the conductorsshould be securely bonded together. Ground rods shall be installed at gridcorners, at junction points along the perimeter, and at major equipment locations.The ground rods are to be driven vertically into the ground to not less than theminimum depth specified in CAN/ULC-S801. Horizontal ground rods may berequired where subsurface rock or other obstructions interfere with the placementof vertical ground rods. The ground conductors may be made of copper or othermetals or alloys that shall not corrode excessively during the expected service life.Ground rods may be made of zinc coated steel, stainless steel, copper-clad steel,or stainless steel-clad steel. The ground conductors shall be securely bonded tothe ground rods and to the equipment (including busbars) to be grounded. Jointsshall be exothermically welded;

2. The ground rods shall be driven to stable soil where constant conductivity properties apply;

3. At least two grounding testing well stations shall be incorporated into the designof each ground grid. Approval of Metrolinx shall be obtained for the locations andnumber of the grounding testing wells. Each grounding testing well station shall

be connected to the ground grid by at least two grounding conductors;

4. Grounding well stations shall be located so that they are accessible to Operationsand Maintenance (O&M) personnel. Locations shall be chosen that minimize the

bonding conductor length;

5. The ground grid shall be bonded to the ac service ground electrode and thestructural steel of the facility structure;



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6. Ground grid locations shall be coordinated with landscaping plans to avoidconflicts with tree roots, as well as underground utilities and sewer installations inorder to avoid any direct electrical connection to these systems; and

7. Ground grids shall be designed to allow up to 50 percent more ground rods to bedriven and attached to the grid in the future.

The grounding and bonding design shall provide for mitigation of the relevant hazardssuch as EMI and lightning.

5.2 Hazards and Electromagnetic Interference

The grounding and bonding system shall be designed to protect persons against hazardsincluding direct and indirect contact with live parts, lightning, and electromagneticinterference.

5.2.1 Direct Contact

The grounding and bonding design shall ensure that persons are protected against dangersand damage that may arise from contact with live parts of the electrified system.

This shall be effected by:

1. Preventing a current from passing through the body of any person; and2. Limiting the current that can pass through a body to a value lower than the

shock current.

5.2.2 Indirect Contact

Indirect contact means electric contact of persons or animals with exposed conductive parts that have become live under fault conditions. Accordingly, the grounding and bonding system shall be designed to protect persons who accidently come in contact withnormally-non-current-carrying conductive parts that may be energized under fault

conditions. This shall be effected by:1. Connecting all such normally-non-current-carrying-conductive parts to

earth either directly or indirectly so that a low resistance path is availablefor fault current to be dissipated (see clause 6.5 for details);

2. Limiting the fault current that can pass through a body to a value lowerthan the shock current; and



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3. Automatic disconnection of the supply within a predetermined time onoccurrence of a fault likely to cause a current to flow through a body incontact with exposed-conductive parts, if the value of the current is equalto or greater than shock current.

Current flowing in 25 kV 60 Hz OCS induces a voltage difference across adjacentmetallic structures, exposed conductive parts, and conductors. The extent of the induced

potential difference depends upon the quantum of power being drawn by the electrictrains, distance of the metallic structures from the OCS and the length of parallelism

between the two. Similarly, running rails are insulated from ground along their length

but are connected to ground at discrete points spaced apart. Because large amounts oftraction return current flows through rails, the rails attain a potential difference withrespect to ground especially at locations away from their connections to ground.

Therefore, the most common examples of indirect contact are:

A broken contact wire falling on conductive parts;

The rail-to-ground potential;

Induced voltage on trackside metallic structures installed parallel to theOCS; and

An internal fault in electrical equipment.

5.2.3 Lightning

Lightning is a massive electrostatic discharge caused by an unbalanced electric charge inthe atmosphere. Each facility and exposed structure shall be provided with appropriatelightning protection measures, based on the incidence of strikes in the area local to eachfacility. Facilities and exposed structures shall be grounded in accordance with therecommendations of the equipment manufacturer, OESC, CEC, NESC, CAN/ULC-801,CAN/CSA – B72 – M87 Installation Code for Lightning Protection Systems and NFPA

780 - Standard for the Installation of Lightning Protection Systems, as applicable.Refer to clause 6.7: Lightning Protection for additional information.

5.2.4 Electromagnetic Compatibility

The grounding and bonding system design shall provide for control of EMI by measuresincluding:

http://en.wikipedia.org/wiki/Electrostatic_dischargehttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Electrostatic_dischargehttp://www.metrolinx.com/en/


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1. Proper grounding and bonding of apparatus, conductor shields, andraceways to maximize shielding and to minimize circulating currents inshields.

2. Surge protection against lightning and other natural sources of EMI.

Additional details about EMC are available in the performance specification EPS-04000:EMC/EMI.

5.3 Step and Touch Voltage

Step and touch potential at the traction power facilities shall be governed by therequirements of IEEE 80: Guide for Safety in AC Substation Grounding and OESC.

The bonding and grounding of other current carrying equipment, enclosures andassociated structures — including the Overhead Contact System (OCS), rails, and othertrackside equipment — shall be designed such that touch voltages do not exceed the valuesindicated in Table 2, below, which has been derived from EN 50122-1: 2011 Section9.2.2.



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Table 2: Durations of Maximum Permissible Touch Voltages

Duration of Current Flow (seconds) Permissible Voltage in V (rms)0.02 865

0.05 835

0.1 785

0.2 645

0.3 480

0.4 295

0.5 220

0.6 180

< 0.7 155

0.7 90

0.8 85

0.9 80

1.0 75≤ 300 65

> 300

(where accessible to the public underall power supply feeding conditions)

60

> 300

(in workshops and similar locations)25



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5.4 Impact of DC Traction Systems in the Vicinity

Where tracks operated by dc traction power systems are located adjacent to electrifiedMetrolinx tracks, coordination shall be required with the dc traction system operator tominimize the possibility of dc stray current circuit paths through the ac system traction

power return circuits. Track insulation between rails and ground shall be enhanced inthese areas.

The design of the traction electrification system (TES) shall minimize the possibility ofcreating dc stray current circuit paths through the return system. The OCS static wire inthe area potentially subject to dc stray currents shall be electrically insulated from theOCS poles by supporting the static wire on insulators. The OCS poles shall be groundedthrough interconnection of the pole; anchor bolts, and steel reinforcement of the concretefoundation so that the ground resistance of individual poles does not exceed 25 ohms. Ifthe ground resistance of any individual OCS pole exceeds 25 ohms, ground rods or othergrounding solutions shall be applied. Fault conditions shall be evaluated and groundingdesigns shall be developed such that unsafe touch voltages are not created.

Any dc stray current leakage from dc system tracks adjacent to the right-of-way/facilitiesduring the design phase shall be monitored and documented to establish baseline levels.

Similarly, any dc stray current leakage from the dc system tracks during the field-testingand commissioning phase shall be monitored and documented, to evaluate anydifferences and take necessary remedial action to assure the integrity of the system.

Where passenger platforms and emergency walkways are located adjacent to dc systemtracks, the designer shall investigate whether inadmissible touch voltages could occur

between the rail and ground, and shall determine whether a voltage-limiting device, suchas non-permanent rail to ground connection, should be installed to control touch voltages.If necessary, the designs shall require that such devices be installed.

All of the above measures shall be coordinated with the signalling system design.

Coordination is required with the dc electrified railroad operator to obtain assurance thatthe operator shall maintain a high level of insulation between the dc system rails andground in these sections to minimize the possibility of dc stray currents leaking into theac traction return system.



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5.5 System Earth

5.5.1 Grounding Network Configuration

The grounding network and the traction return current network are closely interconnectedto constitute a single composite network.

The purpose is to create a grounding network, based on the use of horizontal electrodes oflarge dimensions for (i) facilitating equal-potentiality for all normally-non-current-carrying-conductive equipment and structures, and (ii) ensuring flow of all fault currenttowards the earth including fault currents due to lightning strike.

The grounding network consists of:

1. the structure earth (ground);

2. the common buried earth wire (counterpoise) and the aerial earth wire(static wire);

3. the running rails;

4. impedance bonds;

5. rail and track bonds;

6. bonding and grounding interconnections; and

7. the earth.

Other secondary components, such as cable trays, building structures and bridge steelstructures also participate in making up the overall ground network with low resistance toground at all locations. Connection between parts of this network is realized throughgrounding bars.

Figure 1: General Grounding System Layout, presents a schematic showing the generalgrounding system layout.



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Figure 1: General Grounding System Layout

The grounding system shall be continuously bonded. The grounding electrodes shall becontained within the right of way confines. The bonding material shall be capable ofsustaining the short-circuit currents for up to the total switch-off (trip) time imposed onthe system without thermal degradation or mechanical breakdown. In particular:

The traction equipment bonding shall be capable of discharging a 15 kA faultfrom the OCS within 0.5 seconds (this above value may however be revisedduring the detailed engineering phase); and

The E&M equipment bonding shall be evaluated by each sub-system based on theelectrical characteristics of the piece of equipment to be grounded.



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5.5.2 Connections

The following grounding and bonding requirements shall be met.

1. Exposed grounding and bonding connections such as those at equipment,enclosures, ground busbars, and grounding testing well stations shall bevisible and accessible;

2. Buried/underground joints in grounding conductors and connections shall be exothermically welded. Two-hole compression-type termination lugsshall be used to connect bonding conductors to equipment enclosures.

Connections to reinforcement steel shall be exothermically welded.Splices in grounding conductors shall not be permitted; and

3. Equipment enclosure doors shall be bonded with flexible metal bondingstraps, instead of reliance on hinges for electrical continuity.

Where identical installations exist, the following requirements apply wherever practicable:

1. The routing of conduit and conductors between structures and enclosuresshall not differ;

2. Conductor terminations shall be located in like manner;3. Prescribed materials, cables, and appurtenances shall be compliant with

applicable UL and ULC standards;

4. The colour of the insulation jacket of insulated ground conductors shall be green; and

5. Water, gas or other piping shall not be utilized as a ground electrode orground conductor.

5.5.3 Grounding Bus Bars

Unless otherwise specified, ground bus bar shall be provided in each equipment room and pre-engineered enclosure (e.g., TPF equipment houses, communications rooms, signalhouses, and wayside power control cubicles). A grounding bus bar shall encircle therooms and the door/door frame shall be connected to this grounding as per the GOTransit DRM. Ground bus bars shall be of solid copper with insulated standoffs, and eachground bus bar shall be drilled with rows of holes according to National Electrical



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Manufacturers Association (NEMA) standards for the attachment of bolted compressionfittings.

Additional ground busbars for equipment shall be provided such that no potentialequipment location within an auxiliary space (housing the equipment) is more than 10metres (nominally 35 feet) from the nearest ground busbar.

The system to which ground conductors at ground busbars are connected shall beidentified. The ground busbars shall be connected to the ground electrodes or groundgrids.

5.5.4 Non-buried Grounding Conductors

Non-buried conductors between the ground grid or ground busbar and the groundedequipment shall be insulated copper wire or cable in non-metallic conduit. Groundingand bonding conductors shall be sized in accordance with the applicable code so that theycan pass the maximum ground fault current without melting or fusing before the circuit

breakers or protective relays disconnect the source of the fault current.

Non-buried grounding conductors shall be protected against physical damage andaccordingly routed in conduit, cable tray systems, system-wide cable troughs, orductbank systems under the following scenarios:

1. between buried ground grids and grounding testing well stations;

2. between grounding testing well stations;

3. between grounding testing well stations and grounding busbars;

4. between equipment enclosures and grounding busbars;

5. between equipment enclosures; and

6. along the trackside.

5.5.5 Publicly Accessible LocationsFor locations that are accessible to the public, the following constraints shall apply to thegrounding and bonding design:

1. Anchor bolts and ground lugs shall not protrude in a manner that couldresult in injury or property damage;

2. Materials shall be concealed wherever possible;



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3. Location of grounding testing well stations in public areas shall beavoided; and

4. Tamper proof hardware shall be used.

5.6 Special Requirements for 1x25 kV AC System

The UP Express spur line from Mile Post 13.5 on the Kitchener rail section to thePearson Airport Terminal 1 station will be electrified with 1x25 kV ac configuration.The remaining portion of Kitchener rail section and both Lakeshore rail sections will beelectrified with 2x25 kV ac configuration. In general, the grounding and bonding of 2x25kV ac and 1x25 kV ac systems is similar. The return conductor on the 1x25 kV ac isequivalent to the static wire on 2x25 kV ac system. The major difference is that theelectromagnetic induction impact of 2 x25 kV ac is less severe than that of comparable1x25 kV ac system.



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6.1.1 Bonding at Insulated Joints

At insulated joints, electrical continuity for rail return system shall be maintained throughimpedance bonds. A cross bond is an electrical connection that connects in parallel theconductors of the return circuit. Cross bonds are of the following two types:

1. Cross Bond – Rail to Rail: Electrical bond that interconnects the tworunning rails of the same track, and

2. Cross Bond – Track to Track: Electrical bond that interconnects tracks.

Dimensions of the rail bonds, track connectors, electrical connections shall conform with

AREMA, Manual for Railway Engineering, Chapter 33, Part7 Rail Bonding . Refer toclauses 6.2 and 6.6 for further details about impedance bond and cross bond locations.

Figure 7: A, B, and C Bonds and Cross Bond Configurations and Figure 8: Drain BondConfiguration depicts the types of cross-bonds.

6.1.2 Static Wire (Aerial Earth or Ground Wire)

A static wire, usually installed aerially adjacent to or above the catenary conductors andnegative feeders, connects OCS supports collectively to ground or to the groundedrunning rails to protect people and installations in case of an electrical fault. In an ac

electrification system, the static wire forms a part of the traction power return circuit andis connected to the running rails at periodic intervals and to the traction power facilityground grids. If mounted aerially, the static wire may also be used to protect the OCSagainst lightning strikes.

Other Sections of EPS-03000 provide additional information and design requirementsregarding static wire.

The cross-section of a two-track cantilever showing the location of the static wire isdepicted in

Figure 2: Cross-Section of Two-Track Cantilever Showing Location of Static Wire.



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Figure 2: Cross-Section of Two-Track Cantilever Showing Location of Static Wire

6.1.3 Track Bonding

Running rails are bonded to maintain electrical continuity at mechanical joints. The bonds shall have low electrical resistance and sufficient contact area so that they are not

overheated under normal and fault conditions.The running rails shall be interconnected with one another depending upon track circuitoperation requirements at the same time meeting touch/step potential criteria.



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6.1.4 Return Cables

Return cables are the conductors connecting the return rails or other parts of the returncircuit to the traction power facility ground busbar. With a view to ensuring reliability ofthe traction return path and for safety of personnel they must:

Be as short as possible with the lowest possible impedance;

Have, in general, a cross section not less than 100 mm 2; and

Comply with the following redundancy rule: if N cables are required for thetraction current return, N+1 cables shall be installed.

6.1.5 Current Return Monitoring

Current return monitoring is done through the traction power System Control and DataAcquisition (SCADA) system. In particular, the SCADA system shall measure:

The traction return current returning from the earth (connection between the busbar and the TPF grounding system); and

The total return current of each main transformer / autotransformer (cables between busbar and transformers / autotransformers).

Refer to the performance specification EPS-08000 SCADA.

6.2 Traction Power Facility Grounding

6.2.1 General

The TPF grounding system shall comply with IEEE 142 and all local regulations, andshall ensure that step and touch potentials remain within permissible limits during normaloperation as well as under fault conditions. All relevant local geotechnical data shall beconsidered in the design of the building grounding system.

The rail return path of the 2x25 kV ac autotransformer feed TES consists of the staticwires (aerial ground wires), the running rails, and cable connections from static wires andrunning rails to the traction power facilities. All of these are grounded as detailed below.The static wire is connected at regular intervals to the running rails via impedance bondsand to the grounded centre tap of the secondary winding of each traction powertransformer and the grounded centre tap of the winding of each autotransformer. Thestatic wire runs alongside the catenary to interconnect the OCS supporting structures and



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brackets, such that all normally-non-current-carrying metallic supports of the OCS are atthe same ground and track reference potential.

The traction return current causes a voltage rise in the running rails and static wires, dueto the impedance of these conductors, resulting in a voltage between the running rails andstatic wires and the surrounding ground or other grounded metallic parts (touch voltages).These touch voltages need to be limited to acceptable values. Hazards due to touchvoltages shall be minimized by means of adequate grounding and bonding measures.

In addition to the impedance bond connections at TPFs, further periodic connections between the static wires and the rails through impedance bonds may be needed based onthe traction power load flow simulation results and the touch/step analysis. The designshall determine the required spacing of impedance bonds and interconnections to therails, which must also be coordinated with requirements for compatibility with thesignalling system.

The ground grid at each traction power facility and the centre tap of the secondary ofmain power transformers and the centre tap of autotransformers shall be connected to therails through impedance bonds, and to static wires through two independent connections.Each return cable shall be sized to carry the maximum load current, thereby allowing forthe failure of one return cable. The connection to the running rails shall be through

impedance bonds.

All buried/underground joints in grounding conductors and connections shall beexothermically welded. Splices in grounding conductors shall not be permitted.

All normally-non-current-carrying conductive parts of manholes, handholes, pull boxes,splice boxes; metallic raceways and cable tray systems shall be bonded and grounded.

Where insulated cables are used within the TES, they shall be specified and manufacturedin accordance with the appropriate electrical standards that are applicable to the workingenvironment – voltages, operating and fault currents – to which they shall be subjected.

Cable shields shall be grounded at one end only to minimize the possibility of setting upcirculating current paths.

An electrical safety analysis as described in clause 5.1 shall be undertaken.

The grounding and bonding system for the TES shall not be electrically connected to anynon-traction power facility electrical grounding system.



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6.2.2 Grounding Grid

The grounding systems of all traction power facilities shall be designed based on IEEEand OESC/NESC/CEC/CSA as applicable). See clause 5.1 for additional requirements.The grounding system for each TPF shall generally be comprised of a ground gridconsisting of grounding conductors installed horizontally in a grid. To minimize thedanger of high step and touch voltages at the earth‘s surface, the grid should be installedat shallow depth (usually 30 mm to 45 mm (12 inches to 18 inches)) below grade, asstipulated in the Institute of Electrical and Electronics Engineers standard IEEE 80-2000,clause 9.2.

A thin layer (75 mm to 150 mm (3 inches to 6 inches)) of high resistivity material, suchas gravel, should be spread on the earth’s s urface above the ground grid to increase thecontact resistance between the soil and the feet of any person in the traction powerfacility. The grounding system shall be designed so that the step and touch potentialsunder fault conditions are within the designated limits.

In areas where soil resistivity is high or the TPF space is limited, alternative methodsshould be considered for obtaining low impedance grounding, such as connections toremote ground grids or wire mesh, deep-driven ground rods or drilled ground wells, plusthe use of various additives and soil treatment methods. Transferred potentials, which

can result from interconnection to remote ground grids, shall be considered andmitigated.

Backup calculations shall be provided to prove that the grounding system design ensuressafe touch and step potentials.

All perimeter fences and gates at TPFs shall be effectively grounded and bonded to thegrounding system of the TPF as specified in the applicable code.

Each TPF shall be provided with appropriate lightning protection measures, selectedaccording to the incidence of lightning strikes in the area local to each TPF. Lightning

protection measures shall be grounded in accordance with recommendations of theequipment manufacturer, OESC, NFPA – 780, CEC and NESC. See clause 6.7:Lightning Protection for additional requirements.

Wayside Power Cubicles (WPC) shall be grounded by separately driven ground rods atopposite corners, and connected to grounding pads integral with the cubicle.Compression-type terminal lugs shall be used to connect grounding conductors to



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equipment enclosures. These enclosures shall not be interconnected with the TESgrounding and bonding system.

6.3 Stations and Service Buildings Grounding

6.3.1 Stations and Sidings

Passenger Stations and Service Siding Platforms in At-grade or Trench Locations

For at-grade or trench located platform grounding, a counterpoise (buried earth wire)shall be installed along the entire length of each platform with the conductor buried in

earth and extending a minimum of 20 metres (65 feet) beyond the ends of the platform.One end shall be terminated in a hand hole, which shall permit the counterpoise to beconnected to the rails via an impedance bond, with the location to be coordinated with thesignal system design. The counterpoise shall be connected to the rails at one end only to

permit broken rail detection. Normally non-current-carrying metallic structures andmiscellaneous metallic items within 2.5 metres (8 feet) from the edge of the platform(including platform reinforcement steel, any OCS poles, stairways, platform shelters,elevators, or other features) shall be isolated from the static wire and shall be bondeddirectly or indirectly to the counterpoise. The counterpoise-bonded metallic items shall

be isolated from steel building grounds and particularly from utility grounds. Thecounterpoise shall be connected to the passenger train station’s E&M grounding system .The counterpoise size shall be determined by the systems designer; empirically, its sizeshall be at least equal to that of the static wire. The static wire shall be isolated from theOCS poles and ground in the station platform area.

The grounding design shall ensure that the maximum permissible touch voltages, asspecified in Table 2: Durations of Maximum Permissible Touch Voltages are notexceeded and, without exception, the resistance to ground shall not exceed 5 ohms.Subject to field-testing during construction, it may be necessary to install supplementalground rods at the ends of the counterpoise to achieve the 5-ohm value, and thisrequirement shall be incorporated in the design.

Figure 3: Layout of a Typical Grounding Arrangement at Passenger Station Platforms, presents the layout of a typical grounding arrangement at passenger station platforms.



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Figure 3: Layout of a Typical Grounding Arrangement at Passenger Station Platforms

Passenger Station Platforms in Aerial Structures

New station buildings, including the platforms, shall be constructed to be structurallyindependent from the aerial trackway. The facility electrical system shall utilizeinsulated cable grounding connections to the electric utility supply point.

To minimize step and touch potentials between the station platform and the vehicles, the platform reinforcement shall be electrically interconnected and shall be connected to therails through an impedance bond at one end only, as detailed above for the at-grade

platforms.

The reinforcement in the platform shall be electrically interconnected to thereinforcement in the supporting structure and its foundation reinforcement. If the

platform is constructed using pre-cast panels, grounding plates (as detailed in clause 6.5.4for the aerial structures) shall be used to provide the means for interconnecting thereinforcement in the panels and for attachment of the impedance bond connection.



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Provisions shall be incorporated in the platform design such that all normally-non-current-carrying metallic structures and miscellaneous metallic items within 2.5 metres (8feet) from the edge of the platform (including any OCS poles) shall be isolated from thestatic wire and shall be bonded directly to the platform reinforcement. The platformreinforcement-bonded metallic items shall be isolated from the facility and utilitygrounds.

For existing stations in aerial structures, a counterpoise shall be installed along the entirelength of each platform with the conductor buried in earth and extending a minimum of20 metres (65 feet) beyond the ends of the platform, and other steps shall be taken as

described above for at-grade stations.The grounding design shall ensure that the maximum permissible touch voltages, asspecified in Table 2: Durations of Maximum Permissible Touch Voltages are notexceeded and, without exception, the resistance to ground shall not exceed 5 ohms.Subject to field-testing during construction, it may be necessary to install supplementalground rods outside the limits of the platform, which can be attached to the platformgrounding system to satisfy the touch voltage requirements.

Elevated Access Platforms at Service Sidings

Metallic parts of elevated access platforms such as those for rooftop equipmentinspection and maintenance at service sidings shall be electrically interconnected andshall be connected to the rails through an impedance bond at one end only to minimizestep and touch voltages between the access platform and the vehicles. Provisions shall beincorporated into the platform design such that all metallic structures and miscellaneousmetallic items within 2.5 metres (8 feet) from the edge of the platform (including anyOCS poles) shall be isolated from the static wire and shall be bonded directly to the

platform. The platform-bonded metallic items shall be isolated from any facility or utilitygrounds.

The grounding design shall ensure that the maximum permissible touch voltages, asspecified in Table 2: Durations of Maximum Permissible Touch Voltages are notexceeded. Subject to field-testing during construction, it may be necessary to installsupplemental ground rods outside the limits of the platform, which can be attached to the

platform grounding system to satisfy the touch potential requirements.



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6.3.2 Facility Buildings

Service Entrance and Building Grounding

The ac grounding electrode system (otherwise known as “building ground” or “serviceentrance ground”) shall be designed to:

1. establish a common reference voltage for ac electrical power systems;

2. provide a safe dissipation path for lightning or accidental high-voltagecontact; and

3. Provide a safe dissipation path for electrostatic discharge.

The components that make up the ac grounding electrode system include:

1. the grounding electrode system (ground rod or ground grid);

2. the grounding electrode conductor; and

3. the bonding conductor, which connects equipment grounding systems tothe ac grounding electrode.

A ground grid, in direct contact with the earth at a depth below the earth surface of atleast 1m (3 feet, 3 inches), shall be provided at each building. The ground grid shall be

extended at least 600 mm (2 feet) beyond the foundation footer and at least 450 mm (18inches) outside the roof drip line.

The metal frame of buildings shall be bonded to the ground grid. Connections to theground grid shall be exothermically welded. Where exothermic welding is impractical,cUL listed connection hardware may be used.

For steel-frame buildings, alternate vertical columns shall be bonded to the ground grid.

Building Exterior and Interior Bonding and Grounding

Each grounding conductor that passes through a structure, foundation, or wall shall be

provided with a waterstop.Multiple separate grounding systems are not permitted within the same building. If a

building is supplied by two or more services, the grounding electrodes for the twoservices shall be bonded together.

In multi-floor buildings, the grounding conductor shall be extended to each floor.



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A grounding electrode conductor sized in accordance with the applicable code betweenthe service equipment ground bus and metallic water and gas pipe systems, building steel,and supplemental or made electrodes shall be provided. A grounding electrode conductorshall also be provided for jumper-insulated joints and bolted (non-welded) joints in themetallic piping.

The steel columns shall be bonded to the reinforced steel within the building foundation.

Conductive piping systems shall be bonded to the building grounding system. Bondingconnections shall be made as close as practical to the equipment ground bus.

Within a building, the grounding cable shall, where possible, be embedded in orunderneath the floor slabs. The grounding electrode system shall be attached and bondedto normally-non-current-carrying conductive entities within the building.

6.3.3 Other Equipment in Stations

Refer to clause 6.5 regarding grounding and bonding of fences, gates, level crossinggates, and pedestrian crossings.



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6.4 Bridges Grounding

6.4.1 Existing Bridges

If components of existing bridges and overpasses, as detailed below, lie within theoverhead contact line and pantograph zone (see Figure 5: Overhead Contact Line Zoneand Pantograph Zone) the following special grounding provisions may be required toafford protection to adjacent third party installations:

1. Abutments or Piers: galvanized steel strip on each bridge wall or attachedto columns of piers; and

2. Bridge Face: galvanized steel strip or angle section above the overheadline at each bridge face, if the bridge soffit is within the pantograph zone.

The above measures shall be provided at existing structures if an analysis determines theneed for them.

If the vertical clearance between OCS conductors and concrete overpasses is less than 1metre (3 feet, 3 inches), protection panels (flash plates) shall be installed above the OCS,attached to the underside of the structure, and interconnected to the static wire at not lessthan two locations. For steel overpasses, the steel girders shall be interconnected and

bonded to the static wire at not less than two locations.

6.4.2 New Bridges

Grounding and bonding for concrete beam and steel beam structures, and their supportingabutments or piers, shall be as detailed for the aerial structures (see clause 6.5.4), andshall include provision of grounding plates for connections to the static wire(s).

If components of new overpasses lie within the overhead contact line and pantographzone (see Figure 5: Overhead Contact Line Zone and Pantograph Zone ) the provision offlash plates may be required when the vertical clearance between OCS conductors and

concrete overpasses is less than 1 m. The flash plates shall be attached to the undersideof the structure and interconnected to the static wire at not less than two locations. Forsteel overpasses, the steel girders shall be interconnected and bonded to the static wire atnot less than two locations.



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6.4.3 Structure Continuity

At each new upper or under pedestrian crossing, overpasses, underpasses, or upper andunder vehicle crossings, the reinforcement shall be bonded continuously and shall havean accessible grounding point.

Steelwork with reinforced concrete structures is considered electrically continuous provided it fulfills the following criteria:

Electrical continuity of the reinforcing steel is established between individual precast concrete units; and

At each 65m (200 feet), accessible grounding plates should be available forensuring connection with the rail.

The grounding point is connected to the AECs. See Clause 6.5.4 for additionalrequirements.

6.4.4 Structure Grounding

Depending upon the height of the concrete overpasses compared to OCS, flash plates(protection panels) have to be attached above the OCS, to the underside of the structure,and bonded to AECs at not less than two locations in order to prevent hazard of direct

contacts with OCS. Flash plates shall be required if vertical clearance between OCSconductors and concrete overpass is less than 1m (3 feet, 3 inches) (see Clause 6.4.1).

The metallic reinforcement of concrete bridge structures shall be bonded to the returncircuit. This shall also include road crash fence, handrails, stair cases and security fenceslocated within the step and touch potential limit. Step and touch potential limit existswithin 2.5 m (8 feet) of a standing train, 2.5m (8 feet) from electrically continuous fence

bonded to the static wire, or 2.5 m (8 feet) from any metallic item bonded to the staticwire. With regard to the fences, they must have a longitudinal electric continuity

between panels including possible continuity interruption (gates etc.). This continuity

can be achieved by bonds if an ITB is located near the bridge. If not, a bare conductor isrequired all along the structure.

Galvanized steel strip or angle section shall be installed above the OCS at each bridgeface if the bridge soffit is within the pantograph zone.

Grounding detailed design of overpasses shall be coordinated with the overpass structuredesign.



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A typical generic overhead structure grounding and bonding schematic is shown inFigure 4: Typical Overhead Structure Grounding and Bonding Schematic:

Figure 4: Typical Overhead Structure Grounding and Bonding Schematic



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6.5 Grounding and Bonding of Metallic Components

6.5.1 OCS Support Structures

OCS support structure grounding and bonding should create a conductive path that shallachieve potential equalization of the grounded elements of the railway system.Grounding connections provide for tying wayside metallic parts to the return circuit andfor the electrical interconnection of reinforcing rods in concrete structures, and in case ofother modes of construction, the conductive interconnection of the metallic parts.

The OCS poles shall be grounded through interconnection of the pole to the static wire sothat the ground resistance of the interconnected poles is kept low. Reinforced concreteand anchor bolt foundations, where the concrete is in good contact with the adjacent soil,are recognized as being good earth electrodes. Where the ground resistance of individualOCS poles exceeds 25 ohms, individual ground rods or other grounding solutions shall beapplied. All other OCS structural supports, such as wall brackets, drop pipes, and feederwire brackets shall be interconnected to the static wire.

Ground connections to disconnect switches and ground leads from surge arresters shallhave a maximum ground resistance of 5 ohms. Ground rods and ground mats shall beused to obtain the required ground resistance. If the metallic OCS pole at a disconnect

switch location is to be used as part of the grounding system, the pole must be bonded tothe steel reinforcement in the concrete pier foundation, and the reinforcing steel bondedto one or more driven ground rods or the ground mat.

6.5.2 Overhead Contact Line Zone

A live broken contact line, or live parts of a broken or de-wired pantograph or energizedfragments, may accidentally come into contact with wayside structures and equipment, as

per below (derived from European Standard EN 50122-1) which defines the zone insidewhich such contact is considered probable and which limits are unlikely to be exceeded,in general, by a broken overhead contact line, damaged energized pantograph, orenergized fragments.

The limits of the overhead contact line zone below the top of the rail extend verticallydown to the earth surface, except where the tracks are located on an aerial structure wherethey extend down to the aerial structure deck. In the case of energized out-of-runningOCS conductors, the overhead contact line zone shall be extended accordingly.



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Normally-non-current-carrying metallic components that lie within the overhead contactline and pantograph zone shall be either directly grounded or bonded to the static wire to

provide for personnel safety.

Figure 5: Overhead Contact Line Zone and Pantograph Zone



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For the Mx electrification project, the following values have been retained:

X = 4 metres;

Y = 2 metres (shall be determined based on the rolling stock characteristics;meanwhile, these are assumed to be 2 metres); and

Ih = 8 metres

OCL Zone Indirect Contacts6.5.2.1

All metallic equipment within the OCLZ or the pantograph zone (see Figure 5: OverheadContact Line Zone and Pantograph Zone) is potentially at risk of being in contact withthe OCS or at risk to carry the short-circuit current. Consequently all metallic structures,including the following, shall be connected to the grounding network:

All metallic cases and masts:o OCS switches;o Signal masts and cabinets except point machines,; Line-side telephones

and casing,; Distribution metallic cabinets and boxes;o Radio towers/masts;o

CCTV masts and cabinets;o Cable ladder racks;o Lighting masts;o Turnout mechanical mechanism; ando All metallic components installed in the tunnels.

All metallic structures/components in the vicinity of the OCS including but notlimited to:

o Metallic parapet and protective canopies of bridges, tunnel heads and foot bridges;

o Metallic sheds and platform shelters;o Bridge structures,; Upper steel capping on concrete bridges/footbridges;o Underground along track metallic pipes;o Trays;o Conduits;o Sound walls;o Fences;o Overpass structures; and



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o Outdoor mounted transformer structure etc. Cable shields and armours:

o Power supply;o Signalling; ando Communications.

Lightning and surge arrestors.

All E&M sub-systems and all equipment which is connected to the ground network shall be connected to the nearest grounding bar in a cable trough.

6.5.3 Grounding and Bonding of Structures - GeneralExcept for passenger station and service track platforms, normally-non-current-carryingmetallic items on structures crossing over, under, or immediately adjacent to theelectrified tracks (such as OCS poles, signal and communications enclosures, wayside

power control cubicles, snow melt units etc.) shall be bonded either directly or indirectlyto a static wire and/or to a trackside grounding plate for personnel safety and lightning

protection. The steel reinforcement in the structure elements discussed in the followingsections, including the aerial structure parapets, shall be interconnected electrically andshall be electrically continuous. The grounding and bonding of the emergency walkway

area and other publicly accessible areas, as well as grounding and bonding of the trackstructure (where appropriate), shall be designed to avoid inadmissible touch and stepvoltages and to meet the requirements of the signalling system.

6.5.4 Aerial Structures (Viaducts and Overpasses)

Concrete Aerial Structures

For new concrete aerial structures that carry electric trains, the static wire shall beelectrically grounded through the aerial structure columns and/or the abutments. Thereinforcement steel in the support column foundation shall be electrically connected tothe reinforcement steel of the column. A jumper from the column shall be connectedwith an exothermic weld to a surface-mounted grounding plate near the top and bottom ofthe column, as well as on both sides of the column. Only one plate shall be requiredwhen the upper plate shall be 2 metres (6 feet, 6 inches) or less above finished grade atthe column. The ground resistance, measured at this plate prior to any furtherconnections as detailed below, shall be 25 ohms or less. Where the resistance is greaterthan 25 ohms, additional grounding measures shall be installed to achieve this value.



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The reinforcement steel in concrete aerial structure segments or beams shall beinterconnected and similarly jumper-connected to a surface-mounted grounding plate ateach end of, on both sides of, and near the bottom of the segment/beam. This shall bearranged such that an external jumper can be installed to electrically connect the columnand segment/beam grounding plates. For aerial structure beams that are 65 metres (200feet) or less in length, a grounding plate that is electrically bonded to the reinforcing steelshall be installed at or close to the midpoint of each beam on the inner surface of both

parapet walls, and on the upper surface of the beam for connection to the track slabgrounding plates. For aerial structure beams that are more than 65 metres (200 feet) in

length, additional grounding plates shall be installed such that the along-track spacing between plates is a maximum of 65m (200 feet). The electrical continuity between thegrounding plates on each beam shall be verified prior to any further connections beingmade. The grounding plates at one end of the beam shall only be connected to thegrounding plates at the top of one column, and the grounding resistance checked to verifythat it is equal to or less than 25 ohms. Thereafter the beam-column jumpers at theremaining end of the beam shall be connected.

The parapet grounding plates shall be used for exothermically welded groundingconnections to the OCS poles and to other systems elements, such as signalling andcommunications cubicles or houses, and wayside power control cubicles.

For existing concrete aerial structures separate counterpoise(s) shall be laid on the deck atthe time of electrification. These counterpoises shall be connected to the earth throughvertical ground conductors running on the columns. A counterpoise is required becausereinforcement steel bars cannot be interconnected after the concrete structures have beenlaid. The static wire and all other system elements shall be connected to the counterpoisethrough ground plates. Other details are similar to those for new aerial concretestructures described above.

Steel Structures

For steel girder structures over which the electric trains run, the static wire shall beelectrically grounded by means of jumpers with bolted lug connections to the OCS pole

base plates and exothermic weld connections to the grounding plates on the structurecolumns and/or abutments. The steel bridge girders shall be interconnected at the “ fixedends” with exothermically welded flexible bonds, which shall be connected to thereinforcement steel (within the bridge piers or abutments) at two grounding plates, eachwith a ground resistance of 25 ohms or less, similar to the requirements indicated above



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for the concrete structures. To provide electrical continuity at the “sliding end’, the twoouter girders shall each be connected by an exothermically welded flexible jumper (ofsufficient length to allow for expansion and contraction of the girders) to a grounding

plate that is connected to the reinforcement steel (within the bridge pier or abutment).Where non-ballasted track is installed on the steel support structures, flexible jumpersshall be exothermically welded between the track slab grounding plates and the steelsupport girders.

6.5.5 Track Support Structure

Steel reinforcing bar (rebar) loops in concrete supporting running rails can causeinductive loading or undesired coupling between track circuits. To avoid these adverseeffects, all rebar in any new structure that is within 300 mm (1 foot) of a Metrolinxrunning rail shall be grounded in one of the following configurations. The mostappropriate configuration shall be determined and the same configuration shall be used inall similar applications. Structures to be treated include track slabs, aerial structuredecks, etc.:

1. Long comb: In each affected structure, longitudinal rebar’s (those parallelto the running rails) are electrically connected in a 'comb' pattern to asingle lateral (perpendicular to the running rails) connecting rebar at oneend only of the longitudinal rebars. The lateral connecting rebar shall beconnected by an external connection to the reinforcement that is connectedto ground. The other lateral rebars shall be ungrounded and insulatedfrom the longitudinal rebars at their intersections;

2. Short comb: In each affected structure, lateral rebars shall be electricallyconnected in a 'comb' pattern to a single longitudinal connecting rebar atone end only of the lateral rebars. The longitudinal connecting rebar shall

be connected to an external ground. The other longitudinal rebars shall beungrounded and insulated from the lateral rebars at their intersections;

3. Double comb: In each affected structure, longitudinal rebars shall beelectrically connected in a 'comb' pattern to a single lateral connectingrebar at one end of the longitudinal rebars. The lateral connecting rebarshall be connected to an external ground. The other lateral rebar shall beconnected in a 'comb' pattern to a single longitudinal rebar. Thelongitudinal connecting rebar shall be connected to an external ground.



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The longitudinal and lateral rebars shall be insulated at their intersections,and shall be only connected together through their grounding connection.

Figure 6: Long, Short, and Double Combs

If a structure contains multiple layers of rebar within 300 mm (1 foot) of a running rail,each layer shall be treated in one of the above configurations.

If a structure contains multiple layers of rebar, layers that are greater than 300 mm (1foot) from any running rail can be grounded in any pattern that satisfies the safetyrequirements for grounding and bonding.



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Non-Ballasted Independent Dual Block Track

In this form of new track construction, the independent blocks, which are supported bynon-reinforced track concrete, provide no electrical interconnection through whichtraction current would flow. However, the reinforcement in the cast-in-place concreteslab could become part of the return circuit and shall be grounded and bonded in amanner similar to that for the aerial structure beams/segments.

The grounding design shall ensure that the maximum permissible touch voltages, asspecified in the Table 2: Durations of Maximum Permissible Touch Voltages are notexceeded.

Non-Ballasted Precast Concrete Slab Track

In this form of new track construction, the reinforced precast segmental slabs, which aresupported by non-reinforced asphaltic material, could provide an electrical path throughwhich traction current may flow. In addition, the reinforcement in the cast-in-placeconcrete slab could become part of the return circuit. Therefore, the reinforcement in the

precast segmental slabs shall be inter-connected to the reinforcement in the cast-in-placeconcrete slab and shall be grounded and bonded in a manner similar to that for the aerialstructure beams/segments.

The grounding design shall ensure that the maximum permissible touch voltages, asspecified in the Durations of Maximum Permissible Touch Voltages table, are notexceeded.

6.5.6 Trenches, Retaining Walls, and Retained Fill Structures

The reinforcement steel in the new trench walls shall be electrically connected to thereinforcement steel of the base slab, and successive trench segments shall be connectedtogether to provide electrical continuity. The reinforcement steel in retaining walls orretained fill structures shall be similarly electrically connected to the reinforcement steelof the footing, and successive retaining wall or retained fill structure segments shall beinterconnected to provide electrical continuity. The static wire shall be electricallygrounded through the trench, retaining wall, or retained fill structure reinforcement viasurface-mounted grounding plates, with a ground resistance of 25 ohms or less, asdetailed for the aerial structures.

To facilitate grounding of the track slab, grounding plates, electrically interconnected tothe structure reinforcement, shall be installed in the face of the walkway. Grounding



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plates, electrically bonded to the reinforcing steel, shall be provided at no more than 3metres (10 feet) from each end of, and in each niche/recess in, trench and retaining wallstructures, and at intervals not to exceed 65 metres +/-3 metres (200 feet +/- 10 feet) forall structure types. Systems elements, including signalling and communications cubiclesor houses, wayside power control cubicles, and facilities electrical equipment, shall begrounded to these plates.

For long trenches or retaining wall segments, particularly those cut into rock, the need foradditional grounds or additional along-track ground wires to meet the ground resistancerequirements and to minimize the possibility that rail potentials may cause unacceptable

touch voltages shall be determined and incorporated into the design as needed. If anyadditional ground conductors are laid at low level adjacent to the track or along thewalkways, these conductors shall also supplement the grounding capability of the systemand enhance fault detection and control in the event of a broken wire condition. In orderto provide a sufficiently low ground resistance, it may be necessary to install a groundgrid at or near one or both of the ends of the trench or retaining wall segment.

For existing trenches, along-track counterpoises shall be laid in place of interconnectingreinforcement bars. All other details are similar to those for new trenches describedabove.

6.5.7 Tunnels (As Applicable)

For tunnel sections, metallic drop pipes or brackets that support the OCS cantilevers shall be bonded to the static wire. Depending on tunnel length and the requirements of thesignalling system, the static wire shall be connected to the rail through impedance bonds,in the same manner as for surface sections. For tunnels, particularly those cut into rock,the systems design shall determine whether additional grounds and additional along-tunnel ground wires may be required to meet the ground resistance requirements and tominimize the possibility that rail potentials may cause unacceptable touch voltages.

Any additional required ground conductors shall be laid at low level, adjacent to the trackor along the outer edges of the walkways, so that these conductors shall supplement thegrounding capability of the system and enhance fault detection and control in the event ofa broken wire condition. Based on the rail potential analysis and in order to provide asufficiently low ground resistance, it may be necessary to install a ground grid at or nearone or both of the tunnel portals.



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Where the reinforcing rods in the tunnel structures can be interconnected longitudinally,such as in cut-and-cover construction, or the tunnel is built in sections (with gaps alongthe length), each section shall be connected to the return circuit static wire, or the sectionsshall be connected together and then connected to the static wire, using grounding platesmounted at the interior surface of the tunnel as detailed above for the aerial structures.To facilitate grounding of the track slab, grounding plates, electrically interconnected tothe structure reinforcement, shall be installed in the face of the walkway.

Grounding plates, which shall be electrically bonded to the static wire, shall be providedat no more than 3 metres (10 feet) from each end of, and in each niche or recess in

tunnels and at intervals not to exceed 65 metres +/- 3 metres (200 feet +/- 10 feet).Ground connections for facility services within tunnels shall provide an exposed groundconductor, sized per Code (OESC/CEC), parallel to each track for the complete length ofthe tunnel and interconnected by at least two connections to the ground grid of each

building (e.g., ventilation structures, portal facilities, sump pump structures) associatedwith the tunnel structure. Where the tunnel structure design includes cross passages,emergency shafts, or other ancillary spaces, the ground conductor shall be extended intothese spaces. The ground conductors shall be located to avoid accidental contact by

personnel.

6.5.8 Screen, Noise, Wind, and Safety Barriers

The reinforcement steel of screen, noise, wind, and safety barriers shall be electricallyconnected to the reinforcement steel of the associated structure (e.g., aerial structure,trench) in a similar manner to that detailed above for aerial structures.

Safety barriers shall be electrically bonded to the static wire at not fewer than twolocations. Metrolinx and third party advertising signboards within the Metrolinx right-of-way shall be similarly bonded to the static wire at not fewer than two locations. Theconcerned third party shall be responsible for grounding of its advertising signboards

outside the Metrolinx right-of-way.6.5.9 Fence and Gate Grounding

The design shall evaluate touch voltages on metallic fences and/or gates, including levelcrossing gates, pedestrian crossings and inter-track fences, which lie within the OverheadContact Line and Pantograph Zone, see Figure 5: Overhead Contact Line Zone andPantograph Zone. Ground electrodes shall be installed on either side of a gate or other



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opening in the fence. Fence posts at openings in the fence shall be bonded to form acontinuous path, and gates shall be bonded to support posts with flexible metal bondingstraps to eliminate reliance on hinges for electrical continuity.

Fences shall be made electrically continuous and grounding conductors shall beexothermically welded to fence posts and to any fence material support members (top and

bottom) between posts. Metallic fences inside the Overhead Contact Line andPantograph Zone shall be electrically bonded to the static wire and segmented(electrically insulated) at intervals such that the touch voltage does not to exceed thelimits specified in Table 2: Durations of Maximum Permissible Touch Voltages.

Metallic fences (and gates) outside the Overhead Contact Line and Pantograph Zone, upto a distance of 10 metres (32.80 feet) from the outermost rail of the electrified tracks, perCanadian Standards CAN/CSA-C22.3 No.8-M91, shall be bonded to form a continuous

path in the same manner as detailed above. These fences (and gates) will, however, not be electrically bonded to the static wire. Ground electrodes shall be installed on eitherside of a gate or other opening in the fence, and at intermediate locations, based on localsoil resistivity and worst-case projected potentials. Grounding conductors shall beexothermically welded to fence posts and driven ground electrodes. The requirements ofOESC/CEC shall be met.

6.5.10 Third-Party Grounding Interface

Due to the danger of voltage propagation, third-party grounding installations near theMetrolinx right-of-way shall not be connected to the railway grounding system. Forthird-party pipe work, non-conducting materials shall be used or an insulating segment orinsulated joint shall be inserted at the site boundary. Where the public networkgrounding system cannot be separated from the railway grounding system due to lack ofspace for separation, the traction power return circuit shall be interconnected with theneighbouring grounding system of the public network.

To minimize the possibility of shock hazards outside the fence line, the systems designshall evaluate touch potentials on third-party metallic fences/gates and/or pipelines that parallel the right-of-way, or other metallic structures. The grounding and bonding designshall provide for grounding and/or segmenting the conductive feature using insulatingmeasures for these elements, such that touch potentials are controlled to levels that do notexceed the limits detailed in Table 2: Durations of Maximum Permissible TouchVoltages. Fences and/or segments shall be made electrically continuous, but shall not be



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connected to railway ground grids, grounding conductors, static wires, or the rails, andshall be independently grounded by means of driven ground rods. Grounding conductorsshall be exothermically welded to fence posts and driven ground electrodes.

In cases where fences are purposely electrified to inhibit livestock or wildlife fromcrossing the fence, site-specific insulating measures shall be designed and implemented.

6.6 Grounding and Bonding of Signalling and CommunicationsEquipment

This section describes the grounding and bonding requirements of signalling andcommunications equipment in electrified territory.

6.6.1 Signalling System Equipment and Structures

Signalling Houses and Signalling Rooms6.6.1.1

The grounding system for signalling equipment shall be designed as a single-pointground system. Equipment safety grounding shall be designed to limit touch voltages tosafe levels, as specified in Table 2: Durations of Maximum Permissible Touch Voltages , with and without a fault on the ac system.

Solid copper ground busbars designed for mounting on the framework of open or cabinet-enclosed signalling equipment racks shall be provided. Ground bars within equipmentracks shall be bonded together using solid copper splice plates. All busbars and the metalstructure of the houses and cases shall be bonded to the ground conductor, which in turnshall be bonded to the local ground provision (either ground rods or grounding plateintegrated into the civil structures).

Bonding conductors shall be continuous and routed in the shortest, straight-line path possible.

In each train control room and house, ac and dc ground detectors shall be provided withsensitivity sufficient to detect a ground leakage resistance of 0 to 2,000 ohms for acground and 0 to 10,000 ohms for dc ground.

Trackside Train Control Equipment and Structures6.6.1.2

Grounding of wayside equipment and metallic structures including houses and waysidecases shall be localized as much as