Request ID: FOI-0459-2324 Date published: 12 June 2023
You asked
Dear Sir/Madam,
BS 7671 Regulation 560.5.3 states:
“Where automatic disconnection of supply is used as a protective measure against electric shock, non-disconnection on the first fault is preferred.”
My Freedom of Information requests are as follows:
1. What protective measure is used against electric shock on the Emergency Lighting and other safety circuit installations on the Elizabeth Line?
2. If automatic disconnection of supply is used as a protective measure against electric shock, has non-disconnection on the first fault been considered?
3. If non-disconnection on the first fault has been factored into the design, how is this achieved?
4. If non-disconnection on the first fault not been factored into the design, has this been risk assessed and entered into the designer’s risk register?
We answered
Our ref: FOI-0459-2324/GH
Thank you for your request received by Transport for London (TfL) on 16 May 2023 asking for information about the Elizabeth line.
Your request has been considered under the requirements of the Freedom of Information Act 2000 and our information access policy. I can confirm that we do hold the information you require.
The Elizabeth Line is an operating name for a complex railway with multiple infrastructure managers. Transport for London is only responsible for the infrastructure between Abbey Wood/Pudding Mill Lane and Westbourne Park and therefore our response below only applies to that section of the Elizabeth Line.
What protective measure is used against electric shock on the Emergency Lighting and other safety circuit installations on the Elizabeth Line?
The protective measure used in the context of Regulation 560.5.3 of BS7671 is Automatic Disconnection of Supply.
If automatic disconnection of supply is used as a protective measure against electric shock, has non-disconnection on the first fault been considered?
Non-disconnection on first fault was considered in the designs which were undertaken on behalf of Transport for London by Crossrail Limited.
If non-disconnection on the first fault has been factored into the design, how is this achieved?
Non-disconnection on first fault was not factored into the designs.
If non-disconnection on the first fault not been factored into the design, has this been risk assessed and entered into the designer’s risk register?
Clause 560.5.3 of BS 7671 states that non-disconnection on first fault is preferred (author’s italics). The designs for the Elizabeth Line core section electrical safety services provide for redundancy of equipment and diversity of supplies, meeting the requirements of this clause by alternative means. This approach was fully risk assessed by Crossrail Ltd. and recorded as part of the Programme Wide Hazard Register.
Should you require answers on the remaining infrastructure over which the Elizabeth Line operates, you may wish to contact Heathrow Airport Ltd and Network Rail to see if they can assist you further.
If this is not the information you are looking for, please do not hesitate to contact me.
If you are not satisfied with this response please see the attached information sheet for details of your right to appeal.
Yours sincerely
Graham Hurt FOI Case Officer FOI Case Management Team General Counsel Transport for London
