As you know, the protection requirements of each side of mentioned transformer is different and designer shall consider suitable protection system for each side. Regarding your other question about effect transferring of secondary earth fault to primary phase side, you can refer to Protection Riddle No.1. Indeed, zero sequence current cannot transfer from secondary side to primary phase side in DYn connection, but other sequence element of earth fault currents such as negative and positive sequence can appear in primary side and some protection system such as differential protection can detect them.