MCB upgrade for HST trailer cars

Article: MCB upgrade for HST trailer cars

Background/ Overview

Miniature Circuit Breakers (MCBs) prevent excess current from damaging an electrical circuit. They are designed to trip during a short circuit or overload to protect wiring against electrical faults and equipment failures.

MCBs are found extensively on the underframes of the HST trailer cars operated by ScotRail and these Ottermill-Chilton type MCBs are now obsolete, having been fitted at the time of vehicle build.

MCBs are known to age and to become slow at tripping and so Angel Trains wanted to explore the possibility of changing them to a modern alternative.

DB ESG was contracted to undertake a review into the replacement of these original MCBs with a suitable equivalent. Angel Trains also requested an evaluation into the viability of adding a remote reset facility for an essential circuit breakers, to enable them to be reset from within the carriage by train crew.

Work Undertaken

  • DB ESG conducted a review into equivalent MCBs, confirming their suitability for use. A survey was conducted of the different HST trailer cars, looking at any mechanical and electrical modifications that may be required.  A  design solution report was produced that described the recommended solutions.
  • DB ESG produced a modification procedure that covered all the steps required to decommission, remove old equipment, and retrofit any new components, including wiring changes, post modification installations and functional testing. A full Bill of Materials was created for all materials required to undertake the necessary modification work.
  • A new set of drawings was produced to support any modifications required including;-
    • Details of new fittings and installations for each trailer car type.
    • Modified wiring diagrams.
    • New and updated schematics.
    • A new control panel for the remote reset for the BCB.
  • An engineering change pack detailed all the supporting data calculations and justifications.
  • An independent approvals body, Railway Approvals Ltd, reviewed the modification and delivered the attestation statement to Angel Trains.