Hi Uppeydog,
I assume from your question and terminology that you're located in British territory, or maybe Ireland.
On the 110v side L&N are connected to earth, why dont the tranny trip on short cicuit?
The secondary of these transformers is 110V with the center tap earthed. That center-tap is the only point on the secondary which is earthed, so there can be no short-circuit. The two "outers" of the winding connect to the two current-carrying pins on the 110V sockets.
You thus have 110V for portable power tools, but each side of the circuit is only at 55V with respect to earth. This reduced voltage to earth lowers the shock risk.
The most sensitive RCD used here is generally a 30mA trip type. That's still enough current to be dangerous in some situations.
If American-style GFIs were used, which trip at around 6mA, then it would certainly be an improvement.
