ACSD Test for Nonuniform Insulated Transformer

A transformer of rated voltage 420 kV having non uniformly insulated neutral.What the test levels ?

Follwing the IEC 60076-3 ,I got confused between the below two option.

first level is 1.1Um/1.732- wrt earth .2nd level 1.3Um wrt other phase and 3rd is U1 level. Is this ok? or

first level is 1.1Um/1.732- wrt phase .2nd level 1.3Um wrt other phase and 3rd is U1 level. Is this ok?

Pls clarify ...