Postcode for Kidderminster in the West Midlands, UK.
Also a vector group (connection configuration) of a 3-phase transformer.D - Means Delta Wound Primary
Y - Means Wye (Star) Wound Secondary
11 - Is the phase shift between the two windings. The 11 refers to 11 on a clock face, hence 30 degrees.
It means Transformer Primary Side is Delta and is having two Secondary Windings with phase difference of 30 degree lead. (DELTA STAR STAR )