**9. Case study**

For easy understanding of the smart LoM protection based GOOSE simple electrical system with simple Ethernet communication system network has been defined (modeling of the electrical system within the real time simulator is not focusing of this work) as in **Figure 1**. A laboratory setup for the electrical communication system network that includes Opal-rt simulator, different Light-weight and commercial IEDs, 1000Mbit/sec Ethernet link and Ethernet switch has been established. IEDs light-weight IEC 61850 based FPGA and microcontroller is designed and modeled according to the IEC 61850–7-420 DERs LNs. GOOSE publisher block is continuously publishing the status of the main supply and the ECP through the 146 bytes GOOSE message from the real time simulator. Light-weight native IEC 61850 IEDs based FPGA and microcontroller are designed and modeled based on IEC 61850–7-420 DERs LNs, whereas others IEDs are a normal commercial feeder protection relay, Vamp 52, and ABB 615. Different IEDs are configured as subscriber to the Opal-rt GOOSE messages. The subscriber IEDs use the extracting parameter from the Opal-rt GOOSE for proper implementation of the proposed LoM protection function. Two scenarios based LoM protection function had been specified. Testing for these tow scenarios had been carried out based on the above laboratory setup. The first scenario for the LoM protection function is by changing the DPST. ECPConn data object of the main supply status from "true" to "false" in Opal-rt. This changing of the main supply DPST.ECPConn data object from "true" to "false" indicates that the main supply is not electrically connected to the electrical grid. Now here is regardless to the main supply operation mode. While scenario two, is by changing the main supply operation status by the DRCS.ModOnConn data object from "true" to "false". This changing of the main supply DRCS.ModOnConn data object from "true" to "false" indicates that the main supply is electrically connected however it is not within the operation mode. In practice this means that the circuit breaker is closed but there is no power supply available (e.g. due to main transformer failure). The changing statuses in scenario one and two are published within Opal-rt GOOSE massage. Both scenarios present two cases of the LoM that need to be predicted and detected within the DUT and publish dispatching GOOSE messages based on the new detected status. In our case study the LoM prediction and detection tasks are implemented through the exchanging of the GOOSE messages over the communication system network. Moreover, main and standard deviation of the GOOSE messages round trip latencies had been measured and calculated in next section.
