I am talking about IAS 16(Property, plant and equipment) para 25.

Previously the classification of exchanges was exchanges of similar assets and exchanges of dissimilar assets. An exchange of dissimilar assets is usually considered to have commercial substance but not always.And an exchange of similar assets is considered to lack commercial substance but not always.
In general you can determine if an exchange has a commercial substance by looking at the future cash flows that the company would have received from the old asset and what will it receive from the new asset, if the future cash flows are expected to change significantly then the exchange will be considered to have commercial substance.

Thanks Hamzashaaka