I have digital data over uart, which need to be sent over 5km wire length. Digital data I can cnvert to any protocol like spi, i2c or any other.
RS485 has limitation.

how can i send data?
also is there any 4-20mA transmitter/receiver which can do this?

 

They do it with standard telephone cables... Crank the voltage up to 50V and use a few mA... I would read up about using this tech as I think boosters are used at regular intervals... But remote locations still get decent telephony!!

 

You have not said how fast the data needs to be sent. (Baud rate.) It is more difficult to send high Baud rates over long distances. You could send the data in the form of modulated audio signals using modems at each end of the link.

Les.