201807 – Blakeley-Smith & Stelmach – Immunization, Earthing & Bonding 2.00

25kV railway electrification implementation started in Europe, was implemented in the UK in the late 1950’s and was migrated to Australia in the mid 1970’s. Although some modification and additions were made to accommodate local conditions such as the use of the Multiple Earthed Neutral (MEN) in utility distribution systems, even at that time technology had advanced to the point where some specification requirements really needed reviewing but, lacking practical experience, remained unchanged.

This has become more pressing by the 21st century with the advent of, for example, Optical Fibre technology, LED signals, axle counters and the demise of the Signal Post Telephone reducing S&C circuit lengths, questioning the requirement for Booster Transformers. Never the less, many specifications still quote the standards of the 1950’s.

Unquestioning compliance with requirements appropriate to these standards can have a significant cost, particularly where existing railways run parallel to, but have no running, over 25kV lines, new or to be electrified, or achieving separation of earthing systems in existing complexes or new developments over or immediately adjacent to a 25kV railway. The resulting design may be overly complex, time consuming, expensive or, in practice, realistically unachievable.