distribution transformer transformer proublum neutral voltage unbalance

1000kva 13.8kv/0.4 kv 3phase Delta/star distribution transformer

Note:- transformer secondary star winding Neutral not grounded, since 2007 also like this with out neutral grounded, i have more transformer in my site.

Dear respected friends this transformer as i mention above, their is problum in transformer sec. winding neutral, in my case between neutral & earthing appearing 200vac actually it must be 0v,

today as i trace as follow:-

between phase to phase 400vac, is normal

phase to neutral 220vac , is normal

Earth to neutral 200vac, that is completly abnormal

and Earth to L1, Phase=180, Earth to L2, Phase=250, Earth to L3, Phase=248

also if we will check by 500vac screw driver tester, as connect neutral appearing full indicator, and connect Phase L1, so indicator not Appearing, But another L2 & L3 Light Appearing.

please if someone have answer so help me, because my suspect of transformer secondry star winding neutral left inside, so must be replaced transformer or what please reply.