The Real-Time Digital Simulator (RTDS) is a hardware and software environment that allows for the development of a real-time simulation model of a power system that can interact with actual protection and control devices in a hardware-in-the-loop type of arrangement. The biggest advantage of this type of simulator is that it is possible to model an entire power system model from the generation of the electrical energy, the transmission thereof and the distribution to the consumer, at a fraction of the cost of a real-time experiment that would span across the entire power system network. The IEC 61850 standard is a non-proprietary communication protocol that was established to ensure communication between devices from different vendors and to ensure interoperability between them. There are four levels that are recognized within the power system substation environment across which the IEC 61850 standard is operative – these are the process, bay, station, and control center levels. The process level is the layer where the sensors and actuators are connected to the actual primary plant equipment. The communication in IEC 61850 is Ethernet-based, and the Merging Units (MUs) connected to the primary plant equipment, i.e. Current Transformers (CTs) and Voltage Transformers (VTs), publish these Sampled Value (SV) data at a periodic interval onto the Ethernet network. This data is now available to all devices on the Ethernet network and conforms to the IEC 61850-9-2 format.
The RTDS supports various communication protocols including the IEC 61850 suite of protocols – these include the IEC 61850-9-2 for sampled value messages. This research work involved the conducting of a practical experiment where the simulation model of the power system is developed in RSCAD which is the software environment for use with the RTDS. The simulation model data output is generated by the Gigabit-Transceiver Network Sampled Value (GTNET-SV) Communication Output card. The first part of this research work confirms conformance to the IEC 61850-9-2 standard in terms of the fixed portion, the varying portion and the data portion of the message structure itself. The analysis of the message structure is performed by means of the Wireshark network analyzing software. The second part of this work confirms interoperability between devices from different vendors.
The RTDS firstly simulates the MU where the data from the simulation model is published onto the network in the IEC 61850-9-2 SV format, and is subscribed to by an IED. Secondly the RTDS subscribes to the output of a MU that is publishing the same simulation model data back to a second GTNET-SV card. Time synchronization is performed by using a Global Positioning Satellite (GPS) clock with an IRIG-B signal connected to the GTSYNC card within the RTDS rack. The research work confirms interoperability as data can be communicated in both directions, and also conformity to the IEC 61850-9-2 standard.
Kriger, A.C. Adewole • Cape Peninsula University of Technology