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Topic Title: Standards for DC switch boxes
Topic Summary: Maintenance & testing
Created On: 20 September 2013 08:06 AM
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 20 September 2013 08:06 AM
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Posts: 27
Joined: 25 June 2013

We have a number of 1,500V DC switch boxes to supply the overhead power lines for our railway network. During routine maintenance & inspections, it has been identified that many of the boxes are suffering badly from corrosion, some of them to the extent that holes have actually formed where people could put their hands in and access live 1,500V DC components.

So obviously we are actively looking to address this issue and have made temporary covers/repairs to patch up any holes. We have had quotations for replacement boxes, but they are very expensive. So as a value management excercise, I have been asked to look at getting new casings manufactured and changing out the switch gear to suit.

The only problem with this is that the boxes are 30 years old and are unlikely to meet modern safety standards. My enquiry is, if we are replacing the casing like for like, is this classed as maintenance and therefore only needs to meet the standards that the boxes were originally constructed to; or would the new casings have to comply with modern standards, even though the switchgear likely wouldn't?

Also, does anybody have any indication as to what the old and modern standards are for high voltage switchgear? I am quite familiar with the LV side and BS7671 etc, but the HV stuff is all relatively new to me. What testing would a new case have to undergo before it could be put into service e.g. earth continuity etc.? Are the tests detailed in the standards?

Any opinions/advice would be greatly appreciated.
 21 September 2013 04:04 PM
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Joined: 05 September 2004

This is posted not as advice, but as a way of guiding you towards going to the HSE website and consulting with the Office of the Rail Regulator in the process of determining which is your best solution, refurbishment or replacement.


Memorandum of guidance on the Electricity at Work Regulations 1989


"Electric railway and tramway operators, in conjunction with the Office of the Rail Regulator (HM Railway Inspectorate), have developed standards and safety specifications for the construction of those parts of their systems which use bare conductors at overhead and at track level, together with safe systems of work."

Even working at the edges of the rail industry like me you get to realise that it is a highly regulated industry and that there are specifications and standards written for most products used on the railways and for most actions undertaken on the railways.

If there aren't any specifications and standards written to meet your current needs, you are going to have to design and write them, and if necessary get them agreed with the rail regulator. It may help if you buy in the time of a consulant experienced with this old equipment to help you author the standards and specifications.

If the original manufacturer worked to a set of standards in terms of component quality control and test specifications, that their equipment had to meet prior to being installed on the railway, then I expect you will have to at least follow these in refurbishing the equipment. If the regulator has released more modern standards they may want you to follow these instead.

If you decide to refurbish your own equipment, you will have to document the whole process (including changes in design or component specification) as any original manufacturer would, so that you can prove on inspection that the new design (and your implementation of it) meets the necessary standards set by the regulator and also any in-house standards and working procedures you have separately set down in writing as a company, as part of your quality system for example; e.g. in terms of safety, quality control, manufacturing specification, test specification, installation, maintenance procedures and inspection documentation etc. etc

(In terms of the corrosion you are experiencing this may be just down to old age, or being newly amplified by DC leakage currents or chemical potentials set up by the wrong metals in contact with each other.)

James Arathoon

James Arathoon

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