In old British Standards for transformers,various connections were tabulated in tables.eg 0 connections were in table 1, 11'o clock connections in table 4 etc.So when connection was mentioned, the table number also used to come with it.
The transformer connections were listed by group numbers and these number referred to the phase displacements. These were:
Group 1(1)-zero degrees, clock hour number 0.
Group 11(2)- 180 degrees displacement, clock hour number 6.
Group 111(3)- minus 30 degrees disp., clock hour 1.
Group 1V(4)- plus 30 degrees, clock hour 11.
Here's an excellent resource.
J&P Transformer Book-A Practical Technology of the Power Transformer,Butterworth,numerous editions~$150.
