The extent of the current British Rail Great Northern suburban electrification scheme comprises 111 route km and 365 single track km. The Outer Suburban part of the system uses a 25 kv single-phase overhead system; the Inner Suburban part, which must run in tunnels, is equipped with a 750 v dc third-rail system. The rolling stock consists of Class 312 four-car electric multiple units for the Outer Suburban service from King's Cross to Royston and Class 313 three-car electric multiple units providing the Inner Suburban service between Moorgate and either Hertford North or Welwyn Garden City. The Class 312 cars have a maximum speed of 90 mph, and a maximum acceleration of 0.9 mph/sec. Normal braking is about 1.8 mph/sec, with 2.2 mph/sec for emergency application. The Class 313 units have a maximum speed of 75 mph with rheostatic braking to 12-16 mph, using air-operated disc brakes to effect the final stop. Waste heat from rheostatic braking is used for warming the passenger accommodation. The Class 313 design enables electric current to be collected from either the 25 kV ac. overhead line equipment or from the 750 volts dc third rail systems. Changeover between overhead contact and conductor rail operation is controlled manually by the driver from the operative driving cab. When the 750 volts D.C. system is selected, the vacuum circuit breaker is locked open and the pantograph system physically locked in the down position. Indicator lamps show the system selected. If a train should run on to a live conductor rail section with the overhead contact equipment connected, or vice-versa, a buzzer sounds continuously until all the train equipments are correctly switched to the appropriate system.

  • Corporate Authors:

    Allens (Clerkenwell), Limited

    Wheatsheaf House, 39 High Street
    Wheathampstead, Hertfordshire,   England 
  • Publication Date: 1977-2

Media Info

  • Pagination: p. 28-29
  • Serial:
    • Energy Digest
    • Volume: 6
    • Issue Number: 1
    • Publisher: Allens (Clerkenwell), Limited

Subject/Index Terms

Filing Info

  • Accession Number: 00163297
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Oct 29 2003 12:00AM