ABX                Big Bang at Wynchmore Hill

The story as I was told it was that a substation at Wynchmore Hill was a long way from any of the London Transport power stations.  As a result of this, running a three phase 11kV feeder from two different power stations would be expensive, with a  capital 'E'.  As overhead pylons were out of the question, it meant running cables along railway tracks, and possible under a few roads.  So the powers that be decided to only feed that station with one feeder from a London Transport source and get the second (standby) one from a National grid source.  Although London Transport generated at 33 1/3 Hz and the Grid runs at 50 Hz, it did not present too much of a problem with the 'new' mercury arc rectifiers.  Had they still been using rotary converters, the problems would have been much greater.

All substations that I ever heard of were fed by two feeders from separate sources to maintain security of supply.  The switchgear at the substation was capable of transferring the load from one feeder across to the other when required.  Now it would have been possible to have had either a mechanical or an electro-mechanical interlock that prevented both feeders from being connected to the load simultaneously.  But I suppose the top brass considered that they had well-paid competent staff who knew what they were doing.

But as Mr Murphy will tell you "what can happen, will happen; eventually!"  I was told that the bang could clearly be heard in the street outside the building.  The informant didn't know how much damage had been caused, but he, like me, could deduce that two cables supplying approximately a megawatt of power each would dissipate a lot of energy before the power station circuit-breakers tripped out.

I would have loved to be a fly on the wall, but not too close to the change-over cabinet.