55v - 110v centre tap transformer short circuit calculations

My experience of fixed 110 volt installations has been in pub cellars with everything run in three core cable.

So, what is the earth path from the socket back to the transformer with two core cable, is it in conduit?

The “star” point in a 55-0-55 transformer delivering 110 volts is the centre tap in the transformer, I’m not picturing how the sockets earth terminal are connected to the centre tap. This earth is referenced through the incoming supply earth, is that what is being relied on? 

I presume you are testing loop impedance and fault currents live using an electricians multi-function tester, rather than dead testing resistances with a multi-meter.

In real life I have only ever seen tool transformer fuses blow due to prolonged over load, not due to a damaged cable or the like.

When I started work a firm I worked for was using the old scratch earth 110 volt leads onsite, some of these had fuses which were actually the pin of the plug, you had to unscrew the plug pin and replace it if you blew the fuse, others had solid fixed pins so you had to ensure you laid them out in the correct order and watch what you plugged in to multi-way adapter boxes.

the circuits from the transformer are installed in SWA cable. fly lead from banjo to the transformer earth. 

the circuits from the transformer are installed in SWA cable. fly lead from banjo to the transformer earth.