Converter Transformer Secondary Delta Winding - One Phase Shows Zero Volts

We had Transformer 11KV/718V/718V (Dd0,Yn5) whose Primary had Delta and Secondary has Delta and Star winding.It is a converter Transformer.I want to know in which case delta winding will show double voltage like R-E is showing 825 and B-E is also showing 825 volts.Y-E is showing zero volts. Transformer rating 11KV/718/718Volts.Please tell in which case Delta winding one phase will show zero volts whereas other windings are showing double voltage w.r.t earth?