IET Publication: Guide to Earthing and Bonding for AC Electrified Railways Authors Dr R D White and Allen McDonald - week 6

Week 6 – Design management responsibility & engineering management plans

?This is week 6 of a series of 6 articles based on the application of earthing and bonding requirements for AC electrified railways. These articles are designed to show the necessity for good Engineering Management and in particular, the application of national and international standards and Safety Management processes to ensure the safe and reliable operation of AC electrified railways.

This week the article identifies the importance of the development of Engineering Management Plans which are related to the requirements of earthing and bonding of an AC Electrified Railway. The overarching management plan is the Engineering Management Plan (EMP) which has been detailed in the article of Week 4. Within the EMP there should be a requirement for the development of an Earthing and Bonding Management Plan, EMC Management Plan, and Stray Current Management Plan (when the AC railway is near to DC railways). Additionally, Interface Management is required as part of the EMP to ensure that interfaces are identified by each engineering discipline.

Earthing Management Plan: The content should be based on the performance requirements of relevant national and international standards, i.e. European Standard EN50122-1, EN 50522, EN 62305, National and railway company codes of practice.

The plan should set out a strategy that ensures the management of interconnection of earths, including railway electrification and distribution system, the electrical distribution network operator, the low voltage (LV) distribution and signalling and control systems and other inter-system earths. The requirements of utility company earthing practices (third parties) ?and their connection to the railway need to be specifically recognised and integrated.

The following are key requirements for Earthing and Bonding Management that are relevant to all electrical apparatus, systems and installations forming part of the electrical power supply and distribution, overhead line structures, signalling, telecommunications, stations, depots and interfaces with third parties etc.:

Key requirements for the Engineering Design Management (EMP)

·??????the earthing design process;

·??????design review and interdisciplinary review process;

·??????provide, manage, record, and maintain a hazard log;

·??????ensure compliance with the requirements of the Construction Design Management to include identification of all hazards and risks associated with the engineering, design, implementation, operation and removal of the works;

·??????Undertake interface management, requirements management and change management;

·??????roles and responsibilities

Key Engineering discipline design requirements and deliverables:

·???????????technical specifications and project requirements;

·???????????electrification, signalling, telecommunications and station designs and associated schematic drawings; AFC and As Built designs;

·???????????electrical bonding plans for all disciplines; AFC and As Built designs;

·???????????LV immunisation for signalling and control systems;

·???????????LV Immunisation, including DNO and station;

·???????????Depot earthing and bonding designs – this has special requirements.

?Interface Management Plan: The requirements of Electrical System Integration should ideally be specified in the Engineering Management Plan and the discipline design plans. This will ensure the reliable operation of the railway, safety and the correct operation of systems. On an AC electrified railway the following disciplines and systems are required to undertake integrated design; traction electrification (both rail authority and public supply), signalling and control, telecommunications, GSMR, permanent-way, civil infrastructure, rail vehicles, and third parties. Failure to integrate these electrical systems properly will increase the probability of electrical or control system failure, and the subsequent likelihood of disturbance to the operation of the railway.

As part of the integration process ‘interface matrix’ are required to be produced at the early design stages. This identifies any interface (electromagnetic, galvanic, spatial) between each engineering discipline within the project. The Hazard Identification (Hazid) process should use the interface matrix to identify any hazard associated with each interface.

This picture is of Reading station with DC 3rd Rail and 25kV AC Electrification interface

Where there are known interfaces (spatial, galvanic and electromagnetic), these should be identified through an interface matrix. Where there is a known hazard then an ‘interface specification’ should be prepared between the disciplines, contractors or infrastructure owners. The interface specification should identify the following:

·??????disciplines that are affected; e.g. signalling or utility;

·??????interface between systems e.g. galvanic, clearances, electromagnetic;

·??????hazard e.g. human safety or system reliability;

·??????details that are required to be provided to close out the hazard

Electro-Magnetic Compatibility [EMC] Management Plan: An EMC Management Plan is required and should be based on the requirements of EN50121 (emissions and immunity) , EN61000-5 (installation) and EN61000-6 (emissions and immunity).?It should set out a strategy for the project to ensure EMC is achieved.?It should identify a quality assurance process including hazard identification, deliverables, roles and responsibilities, EMC certification and test specifications.

Preparation of an EMC code of practice for installation and earthing should be based on the requirements of the railway network, best practice in EMC design, installation as defined in EN61000-5.?In designing a railway that operates close to another railway, reference must be made to local railway standards and codes of practice of both railways, as their emissions will impinge on each other.

An EMC test specification should include EMC testing of individual apparatus and at the system level.?Additionally, site measurements may be required to be undertaken for the following system's characteristics of the final installed railway system:

·??????induced voltage (50Hz and harmonics),

·??????conducted voltage (50 Hz and harmonics),

·??????radiated (kHz, MHz & GHz)

·??????electric and magnetic fields (50Hz) .

DC Stray Current Management Plan (protect the AC Electrification system): The ‘stray current management plan’ should provide a guide for the management framework, quality assurance and deliverables that are required throughout the design and installation and commissioning stages of a project. Specifically, this plan should detail:

·??????physical (bridges, stations) and electrical interfaces to other railways;

·??????modelling requirements for electrical interfaces;

·??????acceptable pass/fail criteria for the level of DC stray current, after construction is completed, and throughout the life of the asset;

·??????testing requirements for DC rail insulation and DC rail conductance; ?

·??????monitoring process for the DC rail insulation.

This plan should specify deliverables including the ‘stray current code of practice’, test plans and monitoring plans. The Code of Practice should provide detail of the design, based on known proven technologies and evidence of best practice e.g. electrical substation connection, high rail insulation, good stray current collection, good water drainage construction supervision and quality control by qualified personnel and the necessary testing and monitoring system.

Concluding remarks

New railway projects and the privatisation of railways have divided contracts & disciplines into separate engineering disciplines. Railway authorities need to recognise the importance of integrating electrical systems as failure to do this will have significant consequences on delivering a railway largely free from electrical disturbances.

This application note has endeavoured to demonstrate how railway authorities are being challenged by this difficult task of integrating electrical systems. This challenge will not be made any easier as the client and public expectations of new rail transit systems require the railway designers to incorporate more versatile and operation of AC electrified railway.

The Book ‘Guide to Earthing and Bonding for AC Electrified Railways’ is due for publication in Spring of 2022.

The following are details of the IET Seminar ‘Railway Earthing and Bonding - Requirements for AC 50 Hz Electrified Railways’; which will be based on the book.

28-29 June 2022 | Austin Court, Birmingham, UK

Railway Earthing and Bonding (theiet.org)

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