|
"Southern Electric" is now a trading name of the Scottish and Southern Energy Group but, from 1923 to 1947, it was used by the Southern Railway to promote its electric train services. Electric railways are often seen as "boring" but there is plenty to interest railway historians. The first electric underground railway was built before 1900 and some overground railways were electrified in the early 1900s. At that time the choice was between the "American system", using 600 volts Direct Current from a third rail, and the "German system", using 6,700 volts Alternating Current from an overhead wire. The London, Brighton & South Coast Railway chose the "German system" and electrified its South London line, from London Bridge to Victoria via Denmark Hill, between 1906 and 1909. The London & South Western Railway started a little later, in 1913, and chose the "American system". The LBSCR and LSWR were merged (with the South Eastern & Chatham Railway) into the Southern Railway in 1923 and standardisation became necessary. The "American system" was chosen and the LBSCR lines were converted from overhead to third rail. Under British Railways the voltage of third rail lines was increased from 600 to 750 but London Underground lines remained at 600. Various other systems (notably 1,500 volt DC overhead) have been used in various parts of Britain but the standard for new electrification is 25,000 volt AC overhead. Some new trains are dual voltage and can run on either 25,000 volt AC or 750 volt DC. Where DC is used, the AC supply from the power station must be "rectified" (i.e. converted from AC to DC). Before World War I this was usually done with a motor-generator set (an AC motor driving a DC generator). Between the wars the mercury arc rectifier became popular, being very efficient and reliable. Today, silicon rectifiers are used. The Southern Railway line from Reading to Virginia Water was electrified on the third rail system in 1938, the section from Virginia Water to Waterloo having been electrified earlier. A curious feature was that Earley Station (formerly known as "Early") retained its coal fires and gas lighting for many years after the railway was electrified!
|