Please I don't know if this is off topic. can somebody tell me the voltage rating (in ratio) of a 200kva transformer.

 

Nobody can tell you the transformer voltage rating just from a kVA rating. You need to get the complete specs for the actual transformer.

 

Don't get frustrated please. Transformers are used for supplying power to loads. Actually the voltage rating will decided by the voltages available for connection to the transformer. For example if you are connecting a transformer to a Utility network then generally utilities have a high voltage network and plant loads are usually at a lower voltage level.