Grounding Transformers (Zig-Zag Transformers)

[tsk_nan]

Whether two grounding transformers can be connected to same system at a time in a 33KV ungrounded system?
Two 50MVA,220KV/33KV transformers ,(YD1)are running parallel
two Zig-Zag transformers (250KVA,ZYn11) conncted to 33KV bus
any chance of circulating current in the system through ground in normal running condition?

 

[ruferil]

What is a zigzag transformer? (thought they were rolling papers) and what is YD1 and ZYn11?

Thnaks