Testing Physical Devices

Closed-loop testing is one of the most thorough means of testing physical devices such as protective relay systems and control systems. Closed-loop transient testing is only possible using a real time simulator. Closed-loop testing is characterized by taking signals output from the simulation, and using them as input for a device under test. The output from the device under test is then fed back into the simulation, thereby affecting the simulation. This type of testing most closely resembles the actual performance of the device under test. However, it often requires the exchange of hundreds of input and output signals. The simulator’s hardware architecture must facilitate handling input and output requirements.

The RTDS Simulator can be used to mimic the physical system and provide the full system response during closed-loop testing. Closed loop testing not only tests the functionality and setting of particular devices, but also tests the system's reaction to that device’s operation. This provides for a realistic testing environment for testing the system, the device, and the interaction between the two. As well, using a RTDS Simulator for closed-loop testing enables a large number of contingency tests to be run either with or without user interaction (i.e. Batch Testing) Many of these contingencies could not be performed by any other means or would not be permitted on the real system.

Closed-loop testing should not be confused with playback testing. Playback or open loop testing lacks the ability to have the device’s operation feedback into the simulation.

Closed-loop testing is used for testing both protective relay and controllers. Other testing methods are available to provide some insight into the performance of protective relays. However, only closed-loop real time testing is sufficient to truly test a controller.