Hi, ofcourse. The reason I made this change is that onderstation is a type of substation that feeds the 25kv traction supply system from the high voltage grid. The ones I changed to AT-station are not connected to the high voltage electrical grid, but only contain an autotransformer that is part of the traction power supply system. Therefore AT-stations don't have a 150kv section.  So the function of both types of substation is different. 
You can read more about this here: https://www.infrasite.nl/glossary/tractie-energievoorziening-25kv/
I hope that helps