NavList:

Hi

I have just rejoined the list after a long spell and This is my new message. Things have changed a bit since my last, so this may not go the way it should. If I get it wrong perhaps someone will put me right.

In response to the (old) thread this may be of interest:-    

I have a Journal published by the Institute of Post Office Electrical Engineers (in the UK), on  ‘The Design, Laying and operation of the Trans-Atlantic Telephone Cable’, which was a joint effort by UK, Canada and USA sometime in the early 1950s before Telstar.

In the Introduction to the chapter on Power Feed equipment, it says “the objective of the design of the power plant”  was, amongst several others, to quote:-

“To compensate for earth potential differences of up to 1000 volts, of either polarity, that may develop between the earths at Oban (Scotland) and Clarenville (Newfoundland), during the magnetic storms accompanying the appearance of Sunspots and Aurora Borealis”.

I don’t know what earth voltages were induced during the use of the TAT cable, but clearly the engineers were anticipating them to be quite high! (The cable supply was 1950 V negative, wrt earth, supplied from one end and 1950 V positive from the other).

However, GPS will probably be immune to induced earth voltage as the ground monitoring stations are unlikely to be linked by cable! But high earth voltage excursions might well have damaged the Power and telephone circuits in the USA.   

Clive.