Voltage and current signals signals from simulated instrument transformers are sent to the relay via analogue output via the GTAO card or IEC 61850-9-2 Sampled Values via the GTNETx2 card of the RTDS Simulator hardware.

Analogue outputs operate over a maximum range of +/- 10 Vpeak, so to provide secondary voltage and current to the protection equipment, the GTAO output is connected to power amplifiers (or, in some cases, is connected directly to the protection equipment for “low level” testing).

The protection should respond to faults by providing trip and possibly subsequent reclose signals. Since the network model is simulated in real time, the signals from the protection will be used to operate breakers modeled in the simulation via digital input or IEC 61850 GOOSE Messaging.