Sepam Series 20 and 40: is the changing of settings remotely password protected?

No, the changing of settings remotely is not password protected.
To modify protection settings remotely in Sepam 1000+ through the Modbus communication link, no passwords are required.

The remote setting feature can be inhibited in each Sepam 1000+ (it's one of the parameters of the General settings)

A controlled access to this function have to be programmed in the SCADA system.

The remote setting feature on Sepam 2000 is based on the same principle.