Earthing Design and Installation for the Elizabeth Line

Abstract

This technical paper reviews the various methods for design and construction of the earth electrode systems for both Station, Shafts and Portals as well as systems wide locations. Much knowledge has been gained from the different methods of creating the main earth electrode and there are clear lessons for future constructions of similar magnitude. During construction on the Elizabeth Line there have been issues with quality, buildability, testing and assurance of earth electrode systems that could be easily mitigated on a future project. The Crossrail earthing system is highly integrated and is formed from a number of elemental earthing distribution systems. These elemental distribution systems had to be broken down into zones for the purposes of control of circulating current and testing. Significant knowledge has been gained from traction power commissioning testing as to how effective the earth zoning has been and there are potential opportunities for future projects to simplify designs. The value of the Earth Management Plans (EMPs) became apparent throughout the project as they set out the earthing design plus the process for delivery and integration. The EMPs were kept as live documents which recorded the current configuration of the earthing system on site during construction. At the commissioning and handover stage, the EMPs were finalised to record the as built state for transfer into operation and maintenance. The importance of structure and content of the EMPs plus the benefits of a consistent approach are discussed.