What voltage does a RTU operate at
What voltage does a RTU operate at
The newer RTU's I deal with have 135Vdc supply power. All intelligent electrical devices (IED's) talk through network switches or serial cables DNP3.0 or MODBUS protocol. No AC or DC from IED's go to the new RTU.
Older RTU's I've seen also have 135Vdc Supply power. Secondary voltages and currents go to an analog input card. The ratios should be set up to match the instrument transformer so dispatch sees primary values. I've seen 24V dc to input cards for statuses and alarms.
In Utility Substations, RTUs are powered from the station battery banks. In the event of a total station power outage, remote communications, indication and control functions are still available. I have worked with RTU systems from 24 vdc to 135 vdc. I'm sure there are many more voltages to choose from!