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[email protected] · November 30th 08, 08:12 AM posted to uk.transport.london

In article ,
(Charles Ellson) wrote:

Was the 38 stock on Island Line modified to work only on third
rail? What did that require, if that was the case?

Modification to the same general standard as other SR 3rd-rail stock,
returning current via the wheels and chassis instead of via a central
pickup to a conductor rail. Older LU stock might also have required
upgrading of cables if the insulation was not suitable for 660v (or
750v?) use; under normal conditions an LU train running on LU 4-rail
track doesn't have any parts at more than 440v to earth but when
running on sections of "hybrid" 3or4-rail the highest normal voltage
to earth is 440V to earth. Under fault conditions (centre conductor
rail earthed) on LU the 3rd rail voltage can rise to the full supply
voltage and current stock has cable insulation already rated to cope.

On hybrid sections (e.g. East Putney to Wimbledon) the 4th rail is at
+630v.

--
Colin Rosenstiel