WST-2100-PBACH-R-ME-0042%5B00%5D[1] copy

Sydney Metro Network Stage 2 Reference DesignSection 9 - Earthing, Bonding and EMC

Earthing and Bonding Strategy ReportDate: Author: Revision: Status:

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Document VerificationJob title Reference Design Job number C2100 Document title Section 9 Earthing, Bonding and EMC Earthing and Bonding Strategy Report Status Pre-Final Reference Design

Discipline Revision 0-0 Date 5/03/2010 Filepath/Name Description WST-2100-PBACH-R-ME-0042[00] Issued for Archiving

Prepared byName Signature Filepath/Name Description Jinsun Kim

Checked bySimon Makeham

Approved byDaniel Kuster

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PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOC

Contents1 Introduction 1.1 Background 1.2 Aims and Objectives 2 3 Definitions and Terms Standards, regulations and references 1 1 1 2 3 6 6 6 6 6 7 8 8 8 8 8 9 9 9 11 11 11 11 11 11 12 12 12 12 12 12 13 13 13 13 13 13 13 13 14 14 14 14 14 15 15 15 16

4 Operation and maintenance 4.1 General 4.2 Earthing system 4.3 Rail to Earth Resistance 4.4 DC Stray Current 4.5 EMC Management 5 Earthing and bonding 5.1 General 5.2 Earth mat installation 5.3 Electrical bonding of DC railways 5.4 Electrical strategy

6 Definition of the equipotential zones 6.1 General 6.2 Principles prior to defining the equipotential zones 6.3 Zone A: LV earthing 6.4 Zone B: The running rails 6.5 Zone C: The rail vehicle body 6.6 Zone D: Tunnel services 6.7 Zone E: HV earthing 6.8 Zone F: Platform screen doors 6.9 Zone G: Station lightning protection 6.10 Zone H: Depot 6.10.1 Zone H1: Main line segregation 6.10.2 Zone H2: Rolling stock maintenance building 6.10.3 Zone H3: Infrastructure maintenance roads (Perway) 6.10.4 Zone H4: Depot lightning protection 6.10.5 Zone H5: Washbay 6.10.6 Zone H6: Wheel lathe 6.10.7 Zone H7: Jacking roads 6.10.8 Zone H8: Stabling roads 6.10.9 Zone H9: Overhead contact system 6.10.10 Zone H10: Shore supplies 6.10.11 Zone H11: Depot office areas 6.11 Zone I: Utility pipes

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7 Equipotential zoning strategy for the Sydney Metro 7.1 General 7.2 Overview of earthing arrangement 7.3 Communications equipment 7.4 Generic to Sydney Metro Stations 7.5 Electrical bonding and separation 7.5.1 Separation between rail and platform LV equipment 7.5.2 Mechanical ducting 7.5.3 Platform screen doors


7.5.4 Tunnel services 7.5.5 Walkways 7.5.6 Cross passages services 7.6 Electrical bonding of Depot 7.6.1 Segregation from mainline 7.6.2 Maintenance roads Rolling stock maintenance building 7.6.3 Maintenance roads Infrastructure maintenance 7.6.4 LV earthing in the maintenance aArea 7.6.5 LV earthing in the wheel lathe area 7.6.6 Overhead conductor system 7.6.7 Office areas 7.6.8 Utility pipes 8 DC stray current stations & tunnels 8.1 General 8.2 Monitoring DC stray current 8.3 DC stray current - Depot 8.4 Running rails 8.5 Trackslab 8.6 Tunnel Rings 8.7 Station structure 8.7.1 Tunnel services 9 EMI/EMC 9.1 General 9.2 EMC requirements 9.3 EMC management 9.3.1 Impacts on third parties 9.3.2 EMC management within Metro 10 Lightning protection 10.1 Stations 10.2 Overhead conductor system 10.3 Buildings 10.4 External Electrical Systems

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Appendix A HV Earthing Modelling Report Appendix B Drawing List

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PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOCREF

Reference Design Section 9 - Earthing, Bonding and EMC Earthing and Bonding Strategy Report

Issued for Archiving

11.1

IntroductionBackground

The earthing and bonding of multiple electrical systems consisting of AC HV and LV power supplies and a DC railway is complex due to the need to ensure personnel and equipment safety while also not creating unacceptable conditions for stray traction return current resulting in electrolysis corrosion of buried metal structures. Further, the rail traction, electrical distribution, and corrosion protection areas are covered by different legislation and the demarcation boundaries are such that it is not always simple to align the jurisdictional boundary with a simple physical one.

1.2

Aims and Objectives

The purpose of this report is to provide an overview of the evaluated options and a commentary on the adopted solutions for high voltage earthing, bonding and electrolysis protection across the Sydney Metro Network Stage 2 (SMNS2). It will form the basis for the design development of the above project elements by: identifying both specific and brief requirements relevant to the design of the works.

identifying the specific regulations and standards relevant to the design of the works identifying the verification requirements specific to the elements of the package. identifying the current status of the design and monitoring the timing for delivery of the design information.

This report covers the earthing and bonding design of the SMNS2. CDEGS earthing simulation software has been extensively used in the overall design of the earthing system. The results of the simulation are covered in Appendix A of this report.

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Reference Design Section 9 Earthing, Bonding and EMC Earthing and Bonding Strategy Report

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Definitions and Terms

Table 2.1 Definition of termsAcronymAC AS AS/NZS ASP BCA BPS BS DC DNSP EA EMC ENA EPZ HV IEC IEEE IP kA kV kVA kW kWhr LSZH LV MVA OCC OCS PSD PSTC STS V VA

DefinitionAlternating current Australian Standards Australian Standards / New Zealand Standards Accredited Service Provider Building Code of Australia Bulk power supply British Standards Direct current Distribution Network Service Provider Energy Australia

Electromagnetic compatibility

Energy Networks Association Equipotential zone

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A S A TKilo amps Kilo volt Kilo volt amp Kilo watts Kilo watt hours Low voltage Mega volt amp

High voltage

International Electrical Commission

Institute of Electrical and Electronics Engineers Ingress protection

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Low smoke zero halogen

Operations Control Centre Overhead conductor system Platform screen door Power, Station and Tunnel Control Sub-transmission substation Volt Volt amp

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Standards, regulations and references

The following standards are relevant, as a minimum, for the earthing, bonding, stray current mitigation and EMC works. All works are to comply with the requirements as outlined in the latest version of the relevant standards applicable at the time of installation.

Table 3.1 Applicable Standards and RegulationsStandard Number Description

AS 1125 AS 1768 AS 2053 AS 2067 AS/NZS 3000

Conductors in insulated electric cables and flexible cords Lightning protection Conduits and fittings for electrical installations

Substations and high voltage installations exceeding 1 kV a.c. Electrical installations (also known as the Australian/New Zealand Wiring Rules) Electrical installations Classification of the fire and mechanical performance of wiring systems

AS/NZS 3013

AS/NZS 3080

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Telecommunications installations Generic cabling for commercial premises Telecommunications installations Telecommunications pathways and spaces for commercial buildings Approval and test specification General requirements for electrical equipment Approvals and test specifications Particular requirements for isolating transformers and safety isolating transformers Insulating and sheathing materials for electric cables Polyethylene (PE) pipes for pressure applications Cables - Fire Performance Installation of underground utility services and pipelines within railway boundaries

AS/NZS 3100

AS/NZS 3108

AS 3808 AS/NZS 4130 AS/NZS 4507 AS 4799


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AS 60270 AS 60529 AS/NZS 610006-1 AS/NZS 610006-2 AS/NZS 610006-3 AS/NZS 610006-4 EN 50121-1 EN 50121-2

High-voltage test techniques Partial discharge measurements Degrees of protection provided by enclosures (IP Code) Electromagnetic compatibility (EMC) General standards Immunity for residential, commercial and light-industrial environments Electromagnetic compatibility (EMC) General standards Immunity for industrial environments Electromagnetic compatibility (EMC) General standards Emission standard for residential, commercial and light industrial environments Electromagnetic compatibility (EMC) General standards Emission standard for industrial environments Electromagnetic compatibility Part 1: General

Electromagnetic compatibility Part 2: Emission of the whole railway system to the outside world Electromagnetic compatibility Part 3-1: Rolling stock train and complete vehicle Electromagnetic compatibility Part 3-2: Rolling stock - apparatus Electromagnetic compatibility Part 4: Emission and immunity of the signalling and telecommunications apparatus

EN 50121-3-1

EN 50121-3-2 EN 50121-4

EN 50121-5

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Electromagnetic compatibility Part 5: Emission and immunity of fixed power supply installations and apparatus Railway applications Fixed installations Part 1: Protective provisions relating to electrical safety and earthing Railway applications Fixed installations Part 2: Protective provisions against the effects of stray currents caused by DC traction systems Railway Applications - Fixed installations, DC switchgear Part 1: General Railway Applications - Fixed installations, DC switchgear Part 2: DC circuit breakers Railway applications Compatibility between rolling stock and train detection systems Equipment for General Lighting Purposes EMC Immunity Requirements

EN 50122-2

EN 50123 1 EN 50123 2

EN 50238

EN 61547




AUSTEL

Customer Premises Cabling Manual Customer Premises Cabling Manual, including specifically the following standards: TS 001 Safety requirements. TS 002 Analogue internetworking and non-interference requirements. TS 003 Customer switching system connections requirements. TS 006 General requirements for customer equipment connected to the non switched public network. TS 008 Permitted cabling products. TS 009 Wiring rules for customer premises cabling. TS 010 General premises cables registration requirements. TS 011 Abbreviations, definitions and terms used by TS 001 to TS 006. Communications cabling handbook Building Code of Australia NSW Service and Installation Rules

SAA HB 29 BCA

NS 116

Energy Australia Design Standards for Distribution Earthing Electricity Supply (Corrosion Protection) Regulation 2008 Occupational Health and Safety Act 2000

ENA EG1

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44.1

Operation and maintenanceGeneral

The maintenance schedule and parameters of the earthing network, DC stray current monitoring including rail-to-earth resistance and EMC emission will be determined by the IMO in accordance with ENA EG1, relevant Australian or IEC standards.

4.2

Earthing system

As indicated in Section 12.2 of ENA EG1, the response of an earthing system may progressively degrade, as its conductors and connectors deteriorate because of corrosion, mechanical fatigue, inadvertent breakage, etc. It is not reasonable to assume that an earthing system will maintain its initial performance level indefinitely. Therefore, periodic integrity tests are required to detect and repair damaged or corroded conductors of the earthing system. The frequency and type of periodic checks required are determined by: statutory requirements, and

earth system size and vulnerability (i.e. to degradation by aggressive soils, or vandalism).

The fall-of-potential method or four-point method will be used to measure the earth resistance, which is suitable for the earth grid with a low earth resistance such as that of Metro earthing system. The earth grid of the next station and one of the HV cable sheaths can be used for the current injection. The main earth busbars (MEBs) of the earth grid under test should be disconnected from the earth grid, and the HV cable sheath should be connected to one of the disconnected earth cables to the MEBs. Once the injected current is at the recommend level (as noted by the test equipment supplier) potentials should be measured at different potential probe locations to evaluate the earth resistance of the earth grid. If practical, the stray current collection mats installed in the trackslab in the tunnels, with the minimum of 100mm separation between them at every 300m interval, could be used as a potential probe. If not appropriate, another alternative to measure the earth resistance is to be assessed.

4.3

The minimum acceptable design and construct value for the rail to earth resistance will be 1 M.km per track. With the proposed track system for the Metro, which has the rail insulated and not connected to earth, this rail to earth resistance is anticipate to be readily achieved. The insulation resistance of rail to reinforcement mats will be regularly monitored and compared to ensure that DC stray current is kept within the acceptable levels and not affecting the integrity of nearby structures and services. The proposed method to undertake the testing is indicated in drawing WST-2100-RD-1000-ME-0615.

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4.4

DC Stray Current

Monitoring of DC stray current is incorporated in the design. This is described further in this report. The bond from the running rails tied down to earth at the Depot will be continuously monitored on a daily basis. This needs to be checked if the monitored current can represent the practical DC stray6PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOCT



current. The output from the monitoring will be compared on a daily, monthly and yearly basis to ascertain significant changes in the values recorded. To mitigate DC stray current flowing from/to Utility substations through HV incoming cable sheaths, the compartments of all HV switchboards for incoming cable connections will be equipped with separate cable screen earth bars. This arrangement is to facilitate the future installation of a surge earth clamp which allows isolation between the Utility and station earthing systems to block DC stray current during normal operation and provides a virtual short circuit on an AC earth fault, acting to provide a direct connection of HV cable screens to the switchboard earth bar.

4.5

EMC Management

An EMC management plan is to be prepared during the design and operations, and is to be based on EN50121, 61000-5, AS/NZS 61000-6 and other applicable international railway standards. The EMC management plan will set out a strategy for the Metro to ensure EMC is achieved. It will identify the quality assurance process including hazard identification, required deliverables, roles and responsibilities, EMC certification and test specifications.

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55.1

Earthing and bondingGeneral

The earthing system will be designed to provide means to carry electric currents into the earth under normal and fault conditions without exceeding any operating and equipment limits, or adversely affecting continuity of service. The earthing system will also assure that a person in the vicinity of earthed facilities is not exposed to the danger of critical electric shock. In order to ensure that the designed earthing system is safe, the earth resistance, EPR, touch and step potentials of the system will be verified to be within the safety limits required in the applicable legislation and standards.

As the soil resistivity data for the various sites were not readily available, 150m of soil resistivity was assumed to conservatively represent all the stations for the earthing system modelling. This has been based on measurements of other sites with similar soil conditions. Soil resistivity tests will be require to be undertaken at each station using the Wenner method. Testing should occur for each station once excavation or tunnelling is finished, and before the construction of concrete slab. Based on the earth grid design referred to in Appendix A, and with the assumed soil resistivity, modelling found that the earth resistance, touch and step potentials and EPR levels will be within the safety limits required in the applicable Australian standards and IEEE 80. During the detail design stage, the earthing design analysis will be required to be completed using the measured soil resistivity and finalised station layouts.

5.2

Earth mat installation

The earth grid will consist of 120mm2 bare stranded copper cables laid 300mm below basement slab and electrodes with each, 10mm diameter, copper and 6m length. Boreholes for electrodes will be backfilled with soil enhancement compound of which resistance is less than 5.m. Bonding between two earth grids will be made with two connections using 120mm2 insulated stranded copper cables. All joints will be made by exothermic welds except for bonding connections to equipment. At each riser cable entry through an underground wall or floor, a tinned copper water-stop sleeve coated with epoxy resin will be provided to prevent the ingress of water.

5.3

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Electrical bonding of DC railways

Under no circumstances, other than at the Depot, the platform screen doors at the stations, or those equipotential zones, will there be any direct or indirect bonding to the running rails. This is to ensure that the traction return current flowing in the running rails remains within the running rails and does not seek to flow through the equipment or systems connected to the running rail and cause an electrical malfunction, damage to earthing conductors, or electrolytic corrosion of buried structures.

5.4

Electrical strategy

To assist in defining the earthing strategy for different areas of the Metro system, a strategy of establishing various equipotential zones has been utilised. This is described in more detail below.8PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOCT



66.1

Definition of the equipotential zonesGeneral

Equipotential zones are required for electrical safety and to prevent people touching, at the same time, two metal parts that have a dangerous potential difference. The EPZ is at a low potential with respect to earth during normal operation. Under earth faults the touch voltage may rise to a limit that is specified as un-safe for humans. The boundary of an EPZ is 2m from the outer metalwork. This 2m distance is generally accepted as being the minimum clearance for a possible hand to hand fault and is cited in many books and standards. In the instance of this document, the 2 m distance is considered from the edge of the platform and looks back towards the station building etc. parallel to the platform and is referred to as the buffer zone. The zones in the stations described below are depicted in Figure 6-1.

6.2

Principles prior to defining the equipotential zones

The process when two separate electrical supplies are within a single area, i.e. a Sydney Metro electrical supply and electrical supply from another network such as Energy Australia, Integral Energy or Railcorp, will require an assessment with respect to the 2 m buffer zone. Where the 2 m buffer zone has been achieved, each system can be bonded independently. Where the 2 m buffer zone can not be achieved, care is to be undertaken to ensure that the systems are isolated through the use of insulation or like means. With respect to the Sydney Metro project, there are nine zones that have been identified. These are defined below.

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Figure 6.1 EPZ Zones in Stations

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6.3

Zone A: LV earthing

This zone incorporates all of the station areas except those covered in the zones defined below. Here the assumption is that the bond to the Metro HV network is the neutral of the AC supply and the earth conductor is labelled as the Multiple Earth Neutral [MEN] conductor. Additionally within this zone, the good practice relating to earthing and bonding has been adopted in accordance with electrical codes and standards.

6.4

Zone B: The running rails

This zone has been introduced to address the specific requirements of the longitudinal railway.

6.5

Zone C: The rail vehicle body

The rail vehicle body has been treated as an equipotential zone in its own right. This is due to the fact that the rail vehicle uses the 1500 V DC traction electrical supply, which is configured differently to the LV electrical supply used within the station environment. The obvious differences are the type of voltage and indeed the magnitude. Note: Traction bonding usually takes the form of cross bonding between running rails with a direct connection to the traction return or negative busbar of the substation. This is why it is important not to bond to the running rails.

6.6

Zone D: Tunnel services

This zone has been included for work relating to tunnels on SMNS1 and SMNS2. It has been given its own zone. The risk of touch potential is limited as there will be no electrified rolling stock present in the tunnel during maintenance activities and in the event of a detrainment, the rolling stock will not be drawing electrical current from the overhead contact system. Electrical equipment in tunnels will be bonded in accordance with the relevant standard and will not be bonded to the running rails.

6.7

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Zone E: HV earthing

This zone has been identified as relating to the high voltage electrical network associated with SMNS1 and SMNS2. The HV earthing design is described in detail in the HV earthing modelling report contained in Appendix A.

6.8

Zone F: Platform screen doors

This zone has been explicitly identified in order to address the specific anomaly to the bonding of DC railways rule noted above. The platform screen doors will be bonded to the running rails via a building supply negative busbar. Due the electrical supply being derived from the main station power supply,PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOC

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an isolating transformer has been incorporated into the electrical supply for the platform screen doors. This will ensure that the earth circuit for the station remains independent of the traction return circuit.

6.9

Zone G: Station lightning protection

This zone addresses the specific requirements of the earthing of the lightning protection system to be installed at the station. It is generally understood that stations will not require lightning protection due to their underground location but support structures may create an above ground to underground electrical route. The extent and form of any lightning protection system has been determined to suit the retrospective risk analysis.

6.10

Zone H: Depot

The Depot generally does not comply with the 2 m ruling as there is a requirement to maintain the rolling stock. However isolation will be provided to prevent touch potentials.

This zone has been explicitly created to separate the mainline railway configurations from the Depot. The Depot is split into further sub zones to address the specific requirements of the office areas, maintenance workshops and stabling.

Not all of the following zones are included in SMNS2 works, but are noted within this report to provide a holistic approach to the earthing and bonding design required for SMNS2.

6.10.1

Zone H1: Main line segregation

This zone deals with the segregation of the Depot lines from the main line. This is not the situation and this zone is not required.

6.10.2

Zone H2: Rolling stock maintenance building

This zone is applicable to each individual maintenance road in the rolling stock maintenance building, which is covered under SMNS1.

6.10.3

This zone is applicable to the infrastructure maintenance roads, which are covered under SMNS1.

6.10.4

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Zone H4: Depot lightning protection

This zone has been specifically created to address the specific requirements of the earthing of the lightning protection system to be installed at the Depot. It can be broken down into two further subzones to address the specific requirements of the Depot.

Zone H4A: Lightning protection of the OCSThis zone is applicable to the overhead contact system support structures.

Zone H4B: Lightning protection of the Depot buildingsNo new depot buildings are proposed for SMNS2.




6.10.5

Zone H5: Washbay

The washbay building is a part of SMNS1.

6.10.6

Zone H6: Wheel lathe

The wheel lathe building is a part of SMNS1.

6.10.7

Zone H7: Jacking roads

Jacking roads or elevated roads are a fundamental part of the Depot, allowing safe access to the underside of the rolling stock for maintenance activities. The jacking roads are located within the maintenance shed and do not require traction power, and are covered under the SMNS1 scope.

6.10.8

Zone H8: Stabling roads

Stabling roads have been identified as a separate equipotential zone as they contain a number of metallic structures and electrical equipment, such as walkways, handrails, lighting and CCTV.

6.10.9

Zone H9: Overhead contact system

Zone H9A: Non maintenance roads

The overhead contact system support structures will comply with the requirements laid out in section 6.10.2. The OCS must be double insulated from the support structure. In addition to this, there must be a low resistance return path for fault current in the event that the primary insulation for the OCS is compromised. If such a path is not provided, the DCCB will not trip.

Zone H9B: Maintenance roads

The overhead contact system in the Depot must be capable of full electrical isolation and/or segregation from other parts of the overhead contact system.

6.10.10 Zone H10: Shore supplies

This zone is concerned with the auxiliary power supply provided to rolling stock. This is part of the SMNS1 works.

6.10.11 Zone H11: Depot office areasThis zone is concerned with the low voltage electrical supplies and will comply with AS/NZS 3000. This is part of the SMNS1 works.

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6.11

Zone I: Utility pipes

This zone deals with utility pipes in all areas and the mitigation of DC stray current.


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7

Equipotential zoning strategy for the Sydney MetroGeneral

7.1

This section incorporates the equipotential zoning methodology.

7.2

Overview of earthing arrangement

The overarching earthing arrangement is a MEN arrangement as per AS/NZS3000.

7.3

Communications equipment

A communication earth bar system is to be installed for the connection of communications equipment and other signal circuits. This is to avoid unwanted earth loops to occur between signal circuits. The loops may form when the circuits are earthed to different earth buses with potential differences Ideally a separate communications earth grid separated from the main electrical earth with a surge arrester would be provided with connections to the main earth grid, but in the stations the structure and the separation from the main earth grid will not be achieved. To mitigate the risk of noise, a separate earth bar and cable reticulation will be installed, with the connection to the earth grid occurring as close as practically possible to the earth grid / ground connections. Cabling associated with communications earth installations will be identified with a purple sheath. Under no circumstances will any other electrical equipment be connected to the communications equipment earth bar.

7.4

A typical scenario relating to equipotential zone bonding is shown below.

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Generic to Sydney Metro Stations

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Table 7.1

Station generic bonding guidelinesScenario Bonding Guidance

Insulating membrane below platform finishes, extending 2m from the platform edge. Steelwork within 2m of platform edge. Platform Screen Doors Metalwork Light Fittings, advertising frames, train mirrors, CCTV equipment, etc. within 2 m buffer zone Platform supporting steelwork. Steelwork further than 2m from platform edge. Platform end gates. Light fittings, advertising frames, train mirrors, CCTV equipment, etc. outside the 2m buffer zone.

No bonding required.

No bonding required. Bonded to the running rails, zone B EPZ Bonded to the zone A EPZ (LV earthing).

No bonding required. No bonding required.

No bonding required.

7.57.5.1

Electrical bonding and separationSeparation between rail and platform LV equipment

To avoid simultaneously touching the rail vehicle boundary (i.e. the kinematic envelope) and the platform structures bonded to the AC safety earthing system, a 2m separation will be maintained between them. If the 2m physical separation is not possible, for example where equipment has to be mounted close to the track on an end-of-platform wall, electrical separation can be maintained by a barrier, an insulating wall or double insulation. The LV electrical equipment fixed on the platform but separated from the rail vehicle boundary can be treated by applying the requirements of AS/NZS3000.

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7.5.2

Mechanical ducting

The general assumption is that no metallic mechanical ducting will be located within close proximity of the overhead contact system. Should there be a requirement to do so, then the ducting is to be insulated in the location that close proximity occurs, and method statements will be introduced so that the power to the overhead conductor system is isolated prior to the commencement of maintenance activities on any equipment in contact with the ducting in question.PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOC

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7.5.3

Platform screen doors

Platform screen doors are to be electrically segregated from the main earth system of the station. They are required to be bonded to the running rails. The platform screen doors should be fixed to the platform edge using non conductive materials and they should also be mounted upon suitable insulation mats, similar to those seen when insulating the running rails from the rail fixing. This isolation will also be required for top and side connections to the building structure. The earthing arrangement of the platform screen door is electrically segregated from the low voltage electrical supply. This will be achieved by via the use of an isolating transformer. The communications and control equipment for the platform screen doors will be powered from the station LV supply, any remote communications or control connections to the actual platform screen doors will require isolation. Communications connections will be via optical fibre so there is no electrical connection. Some railway operators do not bond the platform screen doors to the running rails. Research into this field reveals that a particular supplier of platform screen doors does not recommend bonding to the running rails, whilst others recommend doing so.

Whilst this approach may be incorporated upon a risk basis, the decision to bond the platform screen doors to the running rails or to leave them free floating will be very much dependent upon the supplier of the platform screen doors. One reference earthing point at around the middle of the track rail in each station will be provided to prevent circulating current flowing between the rail and PSD earthing circuit due to potential differences along the rail by a large DC current flow.

7.5.4

Tunnel services

The SMNS2 design pertains to the area of which is mostly underground. As a result there will be various tunnel services requiring electrical power. These tunnel services typically include; lighting ventilation pumps, and

communications.

The risk of touch potential in a tunnel environment may be limited to; emergency scenarios involving a detrainment of passengers scheduled maintenance activities, and un-scheduled maintenance activities.

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The risk of touch potential is limited as there will be no electrified rolling stock present in the tunnel for maintenance activities and in the event of a detrainment, the rolling stock will not be drawing electrical current from the overhead contact system. LV cables will be double insulated so that the cable containment does not require connection to earth. HV cables will be sheathed so no contact between cable containment and metallic screens will occur, so that the cable containment does not require connection to earth.




Based on this approach, there are no special arrangements regarding the earthing strategy of the tunnel services. Cable trays, ducting and such like are not required to be bonded to the running rails even though they are within 2 m of the running rails. Earthing of equipment will be to the main station earthing system

7.5.5

Walkways

The general assumption is that walkways will only be used in emergency scenarios but in the event that a walkway is to be used during operational timetable, the following will be applied; handrail detail will specify non conducting material and the method statement will ensure that personnel and equipment required for maintenance will remain within the confines of the walkway, or if non conducting material is deemed too expensive, then the fixings between the handrail and the walkway will be of non conducting material and the hand-rail will be divided into relatively short electrically continuous lengths.

7.5.6

Cross passages services

The cross passages provide a means of safe egress from the railway mainline operations for passengers who have de-trained in an emergency situation. It is proposed that there are no special arrangements required for cross passageway equipment and that the requirements laid out for tunnel services are followed. The general assumption is that the cross passages will only be used as a means of emergency egress from a detrainment. The assumption here is that the overhead conductor system will be isolated and no traction current will be drawn. Should there be a need to operate the cross passages whereby the overhead conductor system is not isolated then the cross passage doors do not need to be bonded to the running rails but they will need to be double insulated to avoid touch potential risks.

7.67.6.1

Electrical bonding of DepotSegregation from mainline

The design does not require electrical segregation from the mainline as there will not be a dedicated electrical substation for the Depot.

7.6.2

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Maintenance roads Rolling stock maintenance building

For elevated tracks, a test connection between the rail waybeam and the ground [via the support structure] will be provided for personal safety reasons. Tracks will be isolated from the remaining traction return system with insulated rail joints (IRJ). These will be located so that they are able to be replaced without the need to demolish any concrete. A diode circuit will be provided connecting the maintenance roads to the Depot roads, providing a path for the traction return currents to flow during the short periods when rolling stock is moved in / out of the shed. The diode circuit will provide a number of diodes to ensure that the failure of one diode will not impact the operations or integrity of the system.


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7.6.3

Maintenance roads Infrastructure maintenance

Tracks will be isolated from the remaining traction return system with insulated rail joints (IRJ). These will be located so that they are able to be replaced without the need to demolish any concrete. The tracks will be earthed so that no earth potential exists.

7.6.4

LV earthing in the maintenance aArea

Low voltage earthing will be in accordance with AS/NZS 3000 and will not incorporate any bonding to the running rails.

7.6.5

LV earthing in the wheel lathe area

Low voltage earthing will be in accordance with AS/NZS 3000 and will not incorporate any bonding to the running rails. There is no risk of touch potential in this area as there will be no traction power delivered to the rolling stock.

7.6.6

Overhead conductor system

The overhead contact system will incorporate an isolation switch, such that the mainline and the Depot can be electrically segregated. The handrails and authorised metallic walkways and routes will be bonded to the running rails via a building supply negative busbar. This will mitigate against touch potential risks within this area. Sections of the overhead conductor system that are to be temporarily made safe for personnel contact must be isolated and connected to rail before contact is permitted.

Stabling roads

These structures will not be bonded to the running rails but will follow the specific requirements of AS/NZS 3000, i.e. the Multiple Earth Network arrangement with the structures connected to earth. Any equipment requiring electrical supply that is connected to these structures will be double insulated from the structure. To minimise the effects of touch potential issues, structures should be insulated at those areas where a touch potential scenario may exist with insulated material. For the actual roads, this zone is a derivative of section 6.10.2 in the sense that it is applicable to the low voltage electrical supply. Battery powered tools, compressed air tools or tools supplied from the auxiliary power supply of the rolling stock will be used in this area of the Depot for maintenance.

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7.6.7

Office areas

Low voltage earthing in the office areas will be in accordance with AS/NZS 3000 and will generally adopt the principles of equipotential zone A.

7.6.8

Utility pipes

Utility pipes will be electrically bonded to the main earth bar. Insulated joints will be required at the property boundaries also.




88.1

DC stray current stations & tunnelsGeneral

The strategy for dealing with the DC stray current inherent with DC systems is to minimise the stray current through insulation, while providing the reinforcement mats under the running rails and installation of a collector cable to allow for capture of any stray current should there be an issue found during regular testing and monitoring activities. A dedicated stray current collector system in the stations and tunnels is proposed, but will not be connected unless an issue is discovered during regular testing and monitoring activities.

The tunnel construction has concrete segments for the tunnel lining, with steel fibres used for reinforcement. The steel fibres are not electrically or mechanically continuous, and thus will not form an electrical circuit. The track form installation in the stations and tunnels will be minimum double insulated from supporting structure (i.e. the track slab), thus negating the need of a stray current mat in the tunnels section of the SMNS2. However, the mat is to be provided to only monitor stray current. In the event of insulation degradation in the future, the mat will be used as parts of the stray current collection system. The predominant ground conditions in Sydney give rise to the understanding that the level of rail to earth resistance is of significant magnitude to ensure there is less than 1A of stray current flowing in mother earth or nearby circuits. The double insulation for the track form is provided by: booted sleepers

rail fixings to be insulated material (nylon washers / pads or similar) so that rail is insulated from the booted sleepers.

The trackslab requirements are outlined below in the chapter 8.5. The oil refinery facilities in Camellia, the buildings in Sydney Olympic Park, and the in ground gas and petroleum pipelines in the Camellia - Silverwater area will need special attention to be taken to minimise the effects of stray current, as well as other facilities along the SMNS2 railway line. Further assessment is required during the detailed design stage of the project to ensure any additional measures are suited to the final installed system.

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8.2

Monitoring DC stray current

As noted above, provisions for DC stray current monitoring will be incorporated in the design (refer to drawing WST-2100-RD-1000-ME-0615). Within the tunnel, copper tags will be provided at set durations connected to the track slab reinforcement to allow for periodic testing for any degradation in the track form insulation. There are no tags in the trackslab sections in the station. This is described in more detail below in the Trackslab section. PSDs and the rail to earth voltage at stations will also be monitored and recorded.


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The output from the monitoring will be compared on a daily, monthly and yearly basis to ascertain significant changes in the values recorded.

8.3

DC stray current - Depot

The track form installation in the Depot will be provided, as a minimum, with single insulation from earth, thus negating the need of a stray current mat. The insulation is provided by: rail fixings to be insulated material (nylon washers / pads or similar) so that rail is insulated from the sleepers where rails are imbedded in concrete and part of the traction return circuit, the rail is to be imbedded in insulating material (e.g. via a booted rail) to provide isolation from earth

where rails are imbedded in concrete, not part of the traction return circuit and insulated from the rest of the Depot rails via insulated rail joints, the rails will be earthed. This includes areas such as the Perway, Maintenance Shed tracks, and the Wheel Lathe.

Monitoring of the earth connection at the Maintenance Building will be provided.

The output from the monitoring will be compared on a daily, monthly and yearly basis to ascertain significant changes in the values recorded.

8.4

Running rails

The traction return current will pass through the running rails and at some point there will be a connection from the rail to the negative busbar at each traction substation. Running rails will be bonded at each station and other areas as noted in the mainline traction negative return schematics, drawings WST-2100-RD-1000-ME-0305, WST-2100-RD-1000-ME-0306 and WST-2100-RD-1000ME-0307 to assist in current sharing to the negative busbar of the traction substation. The purpose of the traction return circuit is to ensure that a redundant path is provided in the traction return to deal with any running rail breakages. Cross bonding has been provided on the following basis: cross bonding to occur at each traction substation location, with the cross bonding to occur at the nearest point to the substation. cross bonding to occur at each station. Cross bonding to occur at the end of each track between tracks. For SMNS1, this is to occur at the end of each siding track in the Depot, and at Rozelle Station. For SMNS2, this is after the stabling tracks at Westmead Station, and at the end of each additional or extended siding track in the Depot

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The cross bonding is used to reduce the overall running rail resistance in order to get the rail potential to below 60V. Preliminary rail potential modelling has indicated that in the rail sections where the distance between traction substations are the greatest, i.e. between Central and Homebush Bay Drive, the rail potential may exceed the 60V. As a consequence, should more detailed modelling confirm this situation, additional measures will be required, such as to install additional cabling connecting to the rail to further decrease the resistance of the traction return circuit. Under no circumstances should any bonds be made to track fixings themselves as this will have an adverse effect upon the stray current mitigation and control which in turn will impact upon the efficient20PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOCT



return circuit of the traction motor current, i.e. traction return current will flow through the fixings and into nearby electrical circuits, metallic structures or earth.

8.5

Trackslab

The design of the trackslab is important, but bears no resemblance to earthing and bonding. The important features of trackslab design revolve around ensuring that the right amount of insulation is installed between the running rail and the sleeper on which it rests. The right amount of insulation assists in the control of stray current. This has been described above. As the trackslab will have steel reinforcement, there are requirements to allow for the possible degradation of the rail to earth resistance, and to enable the collection of any unacceptable stray current if necessary. The reinforcement in the trackslab will be electrically continuous for lengths up to 300 metres maximum creating a series of mats. Each adjacent mat will be electrically isolated. Continuity is provided by welding sufficient longitudinal steel to achieve the equivalent of 70 mm copper over this length. This may be achieved by welding reinforcing bars at 1m grid centres and at laps. Where reinforcing mesh is used, welding at 1 m spacing at laps may be sufficient. Within the trackslab, sufficient steelwork or steel reinforcement must be electrically continuous throughout the length to provide longitudinal conductivity equivalent to that of a 70 mm copper conductor.

Continuity across lateral dowelling joints is to be provided with 2 x 70 mm copper cables connected to each layer of stray current mesh. Copper cables will be connected to reinforcement using Cadweld, or approved equivalent, cable to rebar connectors. There is to be no untied or electrically discontinuous longitudinal construction joints in the slab within the width occupied by a stray current collection mat. The structure containing the stray current collection mats is not be electrically connected, and have minimum of 100mm of concrete separation from any adjoining structures. At the ends of each electrically continuous section insulated copper tail cables equivalent to 70 mm copper will be connected from each mat to an insulated termination bar. Additional connection points will be provided on the termination bar in such pits for future connection to a stray current collector cable which is to transfer collected stray currents between pits before returning to the substation. Testing of the electrical continuity of the stray current collection mats and tail cables is to be conducted to show that a conductivity equivalent to a 70 mm piece of copper cable has been achieved between any two points within the electrically continuous section and between termination bars. This requirement includes testing for continuity across lateral joints. Such testing is to be performed prior to the pouring of concrete. Weld size, throat size, cross-sectional area and surface area is to be consistent with the bars being welded so as to ensure that the correct conductivity is achieved. All welds are to be in accordance with AS1554.

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8.6

Tunnel Rings

The tunnel rings/lining are not required to be bonded to the running rails. The tunnel rings/lining are adequately earthed through the physical ground in which they are connected to.


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8.7

Station structure

Within each structure sufficient steelwork or steel reinforcement is to be electrically continuous throughout the length of the structure to provide longitudinal conductivity equivalent to that of a 70 mm copper conductor between monitoring points. In addition, each lateral reinforcing bar is to be welded to at least two longitudinal bars and each longitudinal bar is to be welded to at least two lateral bars. At least two flexible continuity bonds will be provided across any construction joint, expansion joint or other structural discontinuity each equivalent to a 70 mm copper conductor. At the ends of each electrically continuous section (usually the entire structures in most cases) suitable terminals are to be provided to enable continuity testing and to permit future connection to cathodic or equivalent corrosion protection installation. Terminals are to be Cadweld, or approved equivalent, lugs or plates. These terminals are to be clearly marked, identified and protected, and be easily accessible.

The terminals are to be marked by stamping with a letter punch or using a cast in stainless steel plate. The labelling text size must be 6mm high with the words ELECTROLYSIS TEST POINT.

8.7.1

Tunnel services

For stray current mitigation, all metallic tunnel services within the running tunnels will have insulated joints installed at regular intervals. These joints for all services are to line up with each other and also with the structural joints as outlined above for trackslab measures. Insulated joints will not be located within station caverns.

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99.1

EMI/EMCGeneral

Electromagnetic compatibility (EMC) is the ability of electrical or electronic apparatus to operate in its intended environment without suffering unacceptable degradation or causing unintentional degradation to other apparatus. The railway is a complex electromagnetic environment and the EMC interfaces with other third party systems along railway stations also need to be investigated. Failures in compatibility between systems can introduce costly unreliability in services as well as leading to incidents that may compromise the safety of passengers and staff.

9.2

EMC requirements

All electrical and electronic equipment utilised within Sydney Metro are to meet the latest EMC standards.

The whole railway is a distributed system along the route and need not be tested as a single entity for compliance to the EMC requirements. However, all apparatus, systems and installations that make up the whole railway system must individually comply with the requirements. Therefore, manufacturers, suppliers and installation contractors of all electrical or electronic equipment, systems and installations are to demonstrate compliance with the EMC requirements. Technical construction file will be utilised to demonstrate compliance with EMC within Sydney Metro system, based on rigorous EMC testing and independently assessed by and EMC competent body. Compliances with EMC requirements will be addressed at every phase of Sydney Metro project including design, construction, operation and maintenance.

9.3

9.3.1

Characterisation of the electromagnetic environment is necessary to fully understand the environment in which the railway is intended to operate. An electromagnetic environment characterisation study is to be performed which will consist of a desk top study to indentify the likely intentional interfaces and transmitters such as the existing railway system, utilities, emergency service radio, and medical equipment in nearby hospitals. Site measurements should be undertaken at key locations along the Sydney Metro route to ascertain the electromagnetic ambient. These key locations include, but are not limited to: City Road Broadway Road junction area, due to close proximity to Telstras tunnel and premises at this junction Sydney University, where the alignment passes under all of the Universitys buildings Westmead Station and stabling roads, due to the close proximity of the hospital and the T-Way bus system to the alignment.23

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Impacts on third parties

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Other areas will also have site measurements completed following any additional sites that are identified during the electromagnetic environment characterisation study. An assessment is to be made of the electromagnetic compatibility between the electric traction system, rolling stock and the signalling systems. It will be demonstrated that the proposed installation will neither cause nor be subject to an increase in risk due to electromagnetic interference. An EMC management plant covering design, construction and maintenance will be established. An EMC Installation Code of Practice will be prepared based on the requirements of the railway network, best practice in EMC design, installation and the EN 61000-5 series of standards. In designing the Sydney Metro that operates close to another railway it is necessary that reference is made to the standards and codes of both railways as emissions from on impinge on the other. Preparation of an EMC test specification will include a comprehensive specification of the EMC testing requirements for SMNS2. Tests will include EMC testing of individual apparatus and at system level. Additionally site measurements will be undertaken on the final installed railway system to verify that the project EMC requirements have been met. Westmead Station and the traction substation at Westmead will be located close to Westmead Hospital where sensitive medical equipment and devices are located. There will be building substations located at Westmead Station and traction substation at Westmead Ancillary Site. The position of the electrical substations has aimed to maximise the distance from the hospital, however suitable land acquisition has resulted in the substations being located in areas that may still influence some areas of the hospital. Also, at Westmead, SMNS2 will run under or close to Bus T-way route whose system includes low level signal circuits for closed circuit television, display screens and realtime information. EMI influence from the SMNS2 electrical systems to the hospital and T-way facilities will need further investigation and analysis, with additional mitigation measures to be put in place to provide the necessary compliance.

9.3.2

EMC management within Metro

All traction substations are located on the street level (above ground). The only exception is Leichhardt Station, where, the 1500V DC switchboard room is located underground, but outside the station box. Where practical, the HV and traction equipment, e.g. transformers, reactors, switchgear, are located to maximise the distance to the communications and signalling equipment rooms. The LV design is to mitigate issues of electromagnetic radiation effects on communications and signalling equipment. The preferred method of providing EMC is to maximise the separation between HV / traction / LV cables and communications / signalling installations. The main area of the SMNS2 where it is expected that HV / traction / LV cables and communications cables will be reticulated in long parallel routes is within the tunnels and the station track areas. The separation distance is limited to the tunnel diameter. The routing of cables in the tunnels has been based on: Avoiding reticulating HV / traction / LV cables and communications / signalling cables in close proximity over long parallel routes, and For LV cables , where copper communications / signalling cables and power cables cannot achieve the recommended separation, the LV cables will be enclosed in earthed steel cable ducts (trays, conduits or ducts) Main communications cabling will be optical fibre which is not susceptible to EMC issues. The routing of cables in the station track areas follow similar principles.24PRE-FINAL REFERENCE DESIGN WST-2100-PBACH-R-ME-0042[00].DOCT

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1010.1

Lightning protectionStations

The station entrances will have lightning protection provided through the use of the station building structure. Most of the external building structures are low rise structures, and generally do not tower over the height of adjacent buildings.

10.2

Overhead conductor system

There will be no additional requirement for lightning protection on the overhead conductor system within the tunnels as this system is not susceptible to lightning strikes.

Within the Depot, in order to prevent lightning surges damaging railway infrastructure, surge arrestors will be employed. In addition to surge arrestors, lightning protection via high masts and air terminals are also proposed. This applies to the whole of the Depot area.

10.3

Buildings

All above ground structures will be provided with a lightning protection system. This system will utilise a system comprising of down conductors connected to finials and horizontal metallic straps mounted on the roof of the building and provided in accordance with AS/NZS1768.

10.4

External Electrical Systems

Switchboards and communications connection frames supplying electrical circuits and copper communications circuits used to supply or connect equipment mounted in external areas will be provided with surge protection devices This system will utilise a system comprising of down conductors connected to finials and horizontal metallic straps mounted on the roof of the building and provided in accordance with AS/NZS1768.

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Appendix A HV Earthing Modelling Report

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Sydney Metro Network Stage 2 Reference DesignSection 9 - Earthing, Bonding and EMC

Appendix A - HV Earthing Management Strategy ReportDate: Author: Revision: Status:

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5th March 2010 Jinsun Kim Issued for Archiving Pre-Final Reference Design

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Document VerificationJob title Reference Design Job number C2100 Document title Section 9 Earthing, Bonding and EMC Appendix A HV Earthing Management Strategy Report Status Pre-Final Reference Design

Discipline Revision 0-0 Date 5/03/2010 Filepath/Name Description WST-2100-PBACH-R-ME-0042[00] Issued for Archiving

Prepared byName Signature Filepath/Name Description Jinsun Kim

Checked bySimon Makeham

Approved byDaniel Kuster

Prepared byName Signature Filename Description

Checked by

Approved by

Prepared byName Signature

Filepath/Name Description

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Issue Document Verification with Document

PRE-FINAL REFERENCE DESIGN APPENDIX A_HV EARTHING MANAGEMENT STRATEGY.DOC

ContentsExecutive summary 1 2 3 Introduction Standards for consideration References 1 2 3 4 5 5

4 Methodology 4.1 CDEGS calculation methodology 5 Assumptions

6 Soil model and resistivity 6.1 Soil resistivity testing 6.2 Soil model

7 Earthing design 7.1 Determination of earth fault current contribution for the maximum earth grid potential rise 7.2 Earthing system 7.3 Earthing system impedance 7.4 Earth potential rise (EPR) 8 Hazard investigation 8.1 Maximum allowable step and touch voltages 8.2 Hazardous step and touch voltage analysis 8.3 EPR and EPR transfer hazard investigation. 9 Conclusions and recommendations 9.1 Conclusions 9.2 Recommendations

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6 7 7 7 8 8 10 11 11 13 13 15 16 17 17 17


Reference Design Section 9 - Earthing, Bonding and EMC Appendix A - HV Earthing Management Strategy Report


Executive summaryThis earthing study presents the conceptual computer aided design and performance evaluation for the Sydney Metro Network Stage 2 (SMNS2) earthing systems. IEEE STD 80, AS/NZS 3000, ENA EG1, AS/NZ 4853 and AS 2067 were generally applied for the earthing system design. As site soil resistivity data were not available, an investigation to previous measurements of soil resistivity near to the SMNS2 alignement was undertaken. Thus, a homogeneous soil model, with a soil resistivity of 150 m was evaluated to conservatively represent all the stations and applied to the earthing system modelling. The earth fault levels available from the HV network analysis were utilised.

The modelling of earth bonding between the stations incorporates the screens of two 33kV and two 11kV cable circuits, which will act as earth returns. However, a single tunnel failure between two stations, which places one 33kV circuit and one 11kV circuit out of service, was considered in the analysis. The typical earth impedance was calculated to be less than 0.61 , which complies with the required value of 1 or lower as per AS/NZS 3000. The maximum earth potential rise (EPR) was calculated as 490V at Silverwater station during a phase to earth fault.

The maximum step and touch voltages of the station earth grids were calculated to be 125V and 78V, respectively, which are all within the safe limits according to the IEEE STD 80, AS/NZ 4853 and AS 2067 standards. The maximum surface EPR at neighbouring properties was calculated to be below 500V. Even though the Metro earthing system satisfies the EPR limit required in AS3835, the touch voltages of any utility pipes, metallic structures, fences, etc around the perimeters of the station earth grid rings have to be investigated during the construction design. It must be ensured that no voltage exceeding 430V is transferred to other installations. On the basis of the above findings the station earth grids designed for all the stations and ancillary building areas have been evaluated to be safe according to the applicable standards and recommendations.

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1PRE-FINAL REFERENCE DESIGN APPENDIX A_HV EARTHING MANAGEMENT STRATEGY.DOCT



1

Introduction

The objectives of this report are to provide a safe earthing system design of the SMNS2 that provides means to carry electric currents into the earth under normal and fault conditions without exceeding any operating and equipment limits or adversely affecting continuity of service and assures that a person in the vicinity of earthed facilities is not exposed to the danger of critical electric shock.

In order to ensure that the designed earthing system is safe, the earth resistance, EPR, touch and step potentials of the system are calculated and verified to be within the safety limits required in the applicable legislation and standards, as outlined in Section 2.

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2

Standards for consideration

All electrical installations are subjected to a number of standards and regulations in order to ensure the safety of equipment and personnel. The earthing systems safety compliance has been assessed to the standards and recommendations listed in listed in order of preference in Error! Reference source not found.. It should be noted that Australian Standards, ENA EG1-2006 and AS 3000, are used for their general recommendations and for installation of earthing systems, but ENA EG1 takes precedence for substation installations. Both standards align with the IEEE STD 80 2000 approach for safety assessments.

Table 2.1 Earthing standardsReference NumberENA EG1-2006 IEEE Std 80 2000 IEEE Std 81 1983 IEEE Std 81.2 1999

TitleSubstation Earthing Guide

Guide for Safety in AC Station Grounding

Guide for Measuring Earth Resistivity, Ground Impedance and Earth Surface Potentials of a Ground System; Guide for Measurement of Impedance and Safety Characteristics of Large Extended or Interconnected Grounding Systems; Substation and high voltage installations exceeding 1kV a.c.

AS/NZS 2067 -2008

AS/NZS 3835.1 2006 AS/NZS 3835.2 2006

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Electrical hazards on metallic pipelines Railway Applications Fixed installations Protective provisions relating to electrical safety and earthing. Railway Applications Fixed installations Protective provisions against the effects of stray currents caused by DC traction systems. Electrical installations (known as the Australian/New Zealand Wiring Rules) Lightning Protection

AS/NZS 3000 AS/NZS 1768




3

References

NS 116 Energy Australia Design Standards for Distribution Earthing. Integral Energy Documents Substation Design Instruction SDI 505 - General Details and Minimum Requirements; Distribution Earthing Construction and Test SDI 100 Station layouts of all stations of SMNS2 Single line diagrams of SMNS2 HV modelling report of SMNS2 (Appendix A - Section 17 of the reference design)

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4

Methodology

The Current Distribution, Electromagnetic Interference, Grounding and Soil Structure Analysis (CDEGS application version 12.0.0.133) software package distributed by Safe Engineering Services & Technologies Ltd, Montreal, Canada was employed for the earthing studies. The earthing studies presented here are the results of computer simulation using CDEGS. Software module MALZ has been used to evaluate earth grids performances at station earth systems. An outline of fault current analysis provided in Section 7.1 was used as input data for the earthing study. Design calculations were carried out on the basis of standards listed in Section 2 . The methodology used comprises of theoretical and practical analysis and provides a comprehensive study of the earthing systems. However, the findings included in this report should be supported by on-site measurements based on testing of the system earthing parameters (earth resistance, EPR, step and touch voltages).

4.1

CDEGS calculation methodology

Design calculations incorporate the following:-

definition an appropriate soil model and associated soil resistivity for the calculations. analysis of prospective fault levels and clearance times derived by load flow calculations, to establish the applicable worst-case fault conditions. analysis of the fault current distribution (split between ground current and through cable sheaths) at faulted points using CDEGS software module. calculation of the EPR at station earth grid for different fault scenarios to obtain a conservative value.

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calculation of tolerable step and touch voltages according to IEEE80 2000 and AS 2067 2008 standards. analysis of step & touch voltages of the proposed earthing system using CDEGS MALZ package. assessing the performance of the earthing system and identifying any safety limit violations. The design of earth grids used in the above modelling process will be modified to eliminate the safety limit violations and to achieve 1 resistance limit according to AS/NZS 3000. This will be repeated until the design compiles to the allowable limits. the requirement of having earth returns (additional earth wires and cable screen support) to eliminate the high EPR at stations was considered.

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5

Assumptionsthe selected soil resistivity (150m) is based on data from soil resistivity tests carried out around the Sydney area, at locations close to Western Metro sites and locations with a similar geological and geographical nature. Section 5.1 of the HV Modelling report (appendix A, section 8 of The Reference Design report), identifies distance between substations. These distances have been adopted in this report verbatim. in the earth grid current calculations, it is assumed that each substation earth grid connected to SMNS2 will have an earth grid resistance of less than the typical 0.61 except the ancillary building sites (assumed 1), which has been adopted in calculations.

this report assumes that it is acceptable to connect the earth return of HV cables at both ends between the source substation earth grids and remote substation earth grids, in the SMNS2 system. Therefore, it is essential to evaluate the EPR transfer hazards from at the remote substations, should a fault occur at the source substation before finalising the earthing designs. the resistance for the utility source substation earth grid feeding the earth fault current is assumed to be 0.1 and all the other utility substation earth grids not feeding the earth faults, 1.0 . a single tunnel failure has been assumed as the worst case scenario when selecting number of available cable sheath and separate earth cables (minimum earth return paths).

the primary and secondary fault clearance times used in safety limit calculations are assumed to be 0.12 and 0.5 seconds, respectively.

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66.1

Soil model and resistivitySoil resistivity testing

Soil resistivity data were not available when this earthing study was conducted therefore a desk top study was carried out, taking account of two soil resistivity measurements taken in Carlingford and Woolooware for other projects done by PB. Thus, a soil resistivity model has been adopted, based on data from locations close to SMNS2 sites, with a similar geological nature. The applicable case studies are listed in appendix A1. In order to verify the suitability of desktop data, it is recommended to carry out soil resistivity testing using traverses (100m or more traverse length, that is electrode distance up to 32m or more) inside the caverns before finalising the earth grid detailed designs. Testing inside the caverns (15 to 20m deep from ground level) may avoid the effect of most of the metallic structures. In addition to this, long traverse soil resistivity testing is recommended in nearby park areas (300m or more traverse length that is, electrode distance up to 100m or more).

The testing method suggested is Wenner 4 pin method according to IEEE 81 and ENA EG12006. From such testing, a soil model directly applicable to the SMNS2 system can be identified.

6.2

Soil model

As stated in Section 6.1, the adopted soil model used to assign an approximate value of soil resistivity for use in calculations is based on data identified in third party case studies at similar geographic locations, with assumed equivalent geology. These studies are listed in Appendix A1. . The case studies presented in Appendix A1 reveal that the deep layer soil resistivity is less than 100m. However for conservative design to reflect uncertainties in SMNS2 stations a value 150m has been assumed. Therefore 150m homogeneous (uniform) soil model was considered for the earthing designs.

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77.1

Earthing designDetermination of earth fault current contribution for the maximum earth grid potential rise

For the assessment of the station earthing system performances, it is necessary to evaluate the worst fault scenarios for a fault in the SMNS2 power network. The SMNS2 HV network is proposed to supply two voltages 11kV and 33kV. Therefore both 33kV and 11kV faults were analysed to find out worst case earth fault currents. Single-Phaseto-Ground fault was used for the design. Supply feeders are always operated on radial feeding arrangements; therefore no ring feeding arrangements are considered in this analysis. For this study the fault levels given in Error! Reference source not found. were recorded in an earlier SMNS2 fault and load flow study. These values have been adopted verbatim for the determination of earth fault current in this study.

Table 7.1 Maximum earth fault levels phase to earthCase Substation 33kV Fault level kA

11kV Fault level kA

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Westmead Ancillary Westmead station

Parramatta Station Rosehill Station

Silverwater Station

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10 0Secondary Fault Clearance time Seconds 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Primary Fault Clearance time Seconds

0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12

N/A

15.72

11.64 N/A

17.99 N/A N/A 7.33 N/A 10.59 N/A N/A 17.34

William Street (Canada Bay Station) Five Dock Station Leichhardt Station Camperdown Station Broadway - Sydney University Station Central

Note: Fault levels refers HV modelling report of SMNS2. Note that the clearance times include relay operating times, relay margin errors and circuit breaker operating times. (0.1sec)


8



When estimating the fault current distribution at SMNS2 stations, the earth return line configuration cannot be ignored. Therefore the earth return paths and station earth grids were included in the design to reduce the EPR levels as indicated in Error! Reference source not found.. To reduce the earth fault current to a manageable level, earth return paths listed in Appendix A27 have been considered. It is assumed that all Utility feeders and circuit earth wires and cable sheaths on utility feeders connected to the SMNS2 power network, will be connected to the SMNS2 earth grids. Thus, a utility substation earth grid will be connected through cable screens of power cables and 3x120mm2earth cables. In order to overcome the risk associated with a broken earth conductor connecting the adjacent earth grids, single tunnel failure which makes one 11kV circuit and one 33kV circuit out of service was considered for the analysis. The resultant return current split between the earth wires and the earth grid was calculated using the CDEGS software. It is worth noting that the paralleling effect of the cable sheath (earth wires) reduces the combine effect of parallel earth return paths. The CDEGS considered this as well in its calculations. With the fault and power system data available, the equivalent fault model was derived.

In this analysis using CDEGS, the feeder contribution from utility substations (Error! Reference source not found.) was used. The earth return paths were modelled as listed in Appendix A. Input data used for the analyser were the cable data and the fault current (contribution from the source). Since the utility substation earth grid impedances are unknown, reasonable assumptions were made to make the fault worst case. The utility substation (feeding the fault) earth grid impedance was assumed as 0.1 to obtain the worst case. A simplified circuit diagram of the system is included below. This illustrates the fault current distribution for a fault at Rosehill Station substation. The EPR recorded at each station is listed in Table 7.3.

R D

F A

A S A T

5 T

C AR M

2 H

10 0

Figure 7.1 Typical Fault Circuit9PRE-FINAL REFERENCE DESIGN APPENDIX A_HV EARTHING MANAGEMENT STRATEGY.DOCT



7.2

Earthing system

The earthing system designed consists of two major parts. Earth Grids (electrodes), to be installed at each substation which carry a part of the fault current through the soil back to the source via the earth (soil) is the first major part. The second major component comprises earth return cable screens, which connect all the station earth grids back to the source substation earth grid. The earth grid was designed with several of 6m deep electrodes distributed around the perimeter of the caverns together with the horizontal conductors 0.5m below the station cavern surface level as indicated in drawings. The perimeter of the bottom most (basements) station earth grid was defined such that the outermost conductors are located to the edge of the excavated caverns. To comply with the AS3000, Energy Australias and Integral Energys earthing standard requirements, the standalone earth grid resistance needs to be not greater than 1. To keep the surface EPR levels at the neighbourhood boundaries below 430V, it is necessary to have the resistance around 0.61 per each earth grid in the Metro HV system. Sheath, screen or/and armour of the 11kV cable and all 33kV cables shall be connected to the earthing systems. In addition earthing cables listed in Error! Reference source not found. shall be provided between earth grids. Further,

Sizing calculations for earth grid conductor are given in Appendix D. The calculations were based on 20kA fault current and 0.5sec fault clearance time (secondary fault clearance). On the basis of these calculations, all earth conductors shall be 120mm2 or more. All joints shall be constructed using exothermic welds. Appendix A2 to A23 plots shows the configuration of the designed station earth grid. Appendix A27 shows the earth return paths chosen for each worst case earth fault analysis. Reinforcement bars (re-bars) in the concrete floors are represented in the grounding model by 5m x 5m area at each basement floor (two grids for the plat form on each for other service caverns). These re-bars (radius of 0.008m) are buried at a depth of 0.0013m (0.005m cover). Note that only the top layer of the re-bars is modelled. All re-bar grids are modelled as 5 linearly spaced steel conductors each along X and Y directions. Four corners of the re-bar grid were bonded to the earth grid using bare conductors. This underground metallic structure was represented in the CDEGS model by steel wires. The choice of this type of representation is based on CDEGS guide for concrete floors and restricts the modelled re-bars to small portions to avoid significant computation time while remaining conservative in the design approach, i.e. the computed performance of the grounding system based on the above recommended technique will always be worse than the computed performance of a model that includes all of the re-bars.

R DCase 1 2 3 4

F AFrom

A S A T

5 T

C AR M

2 H

10 0

Table 7.2 Additional earth return pathsTunnel Sections To Westmead Station Rosehill Station Sydney Olympic Park Station Leichardt Station No of 120mm2 Cables per Tunnel 8 2 2 2

Westmead Ancillary Parramatta Station Silverwater Station Five Dock Station


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Case

Tunnel Sections From To Camperdown Station Broadway-Sydney University Station Rosehill Station Homebush Bay Drive Ancillary Central Station Central Station

No of 120mm2 Cables per Tunnel 2 2 3 3 3 3

5 6 7 8 9 10

Leichardt Station Camperdown Station IE Camellia STS to EA Homebush STS EA Campbell St ZS EA Surry Hill STS

7.3

Earthing system impedance

The calculated earth grid impedance for a station earthing system, considered for the modelling was less than 0.61. Since the stand-alone earthing system resistance is not greater than 1, HV and LV combined earths can be utilised for stations earthing systems. Further the stand-alone resistances of the earth grid satisfy the Australian lightning standard AS 1768 requirement of being not greater than 10. Therefore lightning down conductors can be connected to the earthing system, but the earth grid must not be solely relied upon to dissipate lightning strikes. A separate lightning design study should address the lightning design requirements, wherein interconnections with power frequency earth grids should only be considered as fortuitous connections.

7.4

Earth potential rise (EPR)

The CDEGS simulation EPR values for worst case faults at stations are given in Table 7.2 below. These values are used to energise the earth grids to calculate the step and touch voltages.

Table 7.3 Maximum earth potential riseCase Rail way Station and Ancillary shaft locations Maximum EPR V

R D

F A

A S A T1 2 3 4 5 6 7 8 9

5 T

C AR M

2 H

10 0

Westmead Ancillary Westmead Station Parramatta Station Rose Hill Station Silver Water Statio

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