Power Utilities Protective Relay Usage
According to the North American Study of Electric Power Utilities Protection and Control Management and Staff, roughly half of relays installed are digital relays instead of electromechanical types. However, almost all new relay purchases will be digital.
The most common communication protocol is RS-232, however, RS-485 and RS-422 usage is increasing.
It also appears that IEC 61850 will be adopted by many utilities in the near future.