Hello @Neethu,
The Schneider EM6400 supports Modbus and you can read the values into Evok or Mervis.
The L&T ER300P has RS485, but with some custom L&T protocol. You cannot easily read the data into Evok or Mervis.
Typically, the best way is to use Modbus devices. Trying to implement any other protocol would be quite time consuming and requires vast knowledge.
Martin