# On the Use of LoRa Technology for Logic Selectivity in MV Distribution Networks
## 7 Experimental Tests
### Measurement Setup  
To carry out the tests, an automatic measurement station was created in the National Instruments LabVIEWTM environment, which allows: (i) the performance of repeated tests, (ii) the recording of the results of each test, and (iii) the determination of the average and standard deviation of the time intervals of interest for each case study. At the end of the programmed tests, a report file is released. Before starting the tests on the particular selected case study, some operations have to be performed on each PR: (1) adjusting the timer of the board master with the Maximum Blind Waiting time \(T_{MBW}\), as determined in Table 9; (2) configuring the sensor node board with the LoRa transmission parameters appropriate to guarantee a nominal time for transmitting the **Blind** message that is less than \(T_{MBW}\); (3) connecting the pin used by the circuit controller that generates the fault event so that, during the test, all the PRs detect the presence of the fault in the same instant. Items 1 and 2 are strictly connected to the type of fault. Item 3 is instead dependent on the desired position of the fault in the line. In particular, pin PA2 of the circuit controller has to be connected to pin PA11 of all the PRs that have to sense the fault (i.e., the boards emulating the PRs upstream of the fault); for the other boards (emulating the PRs downstream of the fault), pin PA11 has to be referred to ground. The tests can be started from the control panel created in LabVIEWTM (National Instruments, Austin, TX, USA). At power-up, all the boards are kept in reset status by the circuit controller. The command to start a new test is sent from the automatic measurement station to the circuit controller via USB cable. After 1 s, the circuit controller releases the reset lines and all the boards enter the normal operating condition. In this state, the green LEDs of both SR and the masters of PR1, PR2, and PR3 are turned on to emulate the closed state of the respective CB and the supply of the entire MV line up to the boundary TR, which, instead, has the green LED off to emulate the breaker in the open state. After another second, the fault event is generated by raising the PA2 line of the circuit controller. All the boards that revealed the fault can then identify it and start the planned actions. The test ends when the reconfiguration of the line is terminated with the isolation of the fault and the closure of the interconnection breaker. All the digital signals of interest are sampled with a rate of 100 kS/s and recorded through the digital I/O lines of a National Instruments data acquisition board NI-USB 6343. In particular, for each MASTER, the acquired signals are:  
* the control signal of the yellow LED, which indicates the arrival of a message that can be a Blind from a downstream protection, a Trip from an upstream protection, or a Close message for the TR from an upstream protection; \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fault Type** & **Fault Clearing** & **Fault Detection** & **Tripping** & **Blind Waiting** \\  & **[ms] \(T_{TC}\)** & **[ms] \(T_{D}\)** & **[ms] \(T_{TRIP}\)** & **[ms] \(T_{MBW}\)** \\ \hline
50.S3 Poly-phase short circuit (Threshold 600 A) & 120 & 27 & 60 & 33 \\ \hline
51N.S1 Two-phase to ground fault & 170 & 27 & 60 & 83 \\ \hline
67N.S2 One-phase to ground fault with not compensated neutral & 170 & 57 & 60 & 53 \\ \hline
67N.S1 One-phase to ground fault with not compensated neutral & 450 & 57 & 60 & 333 \\ \hline
51.S2 Poly-phase short circuit (Threshold 250 A) & 500 & 57 & 60 & 383 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Times for fault clearing, detection, tripping, and blind waiting depending on the fault type. * the control signal of the green LED, which indicates the status of the circuit breaker (high level means LED on, i.e., breaker closed);
* the TxRxDone signals that indicate a transition when a LoRa package transmission or reception is completed.