# On the Use of LoRa Technology for Logic Selectivity in MV Distribution Networks
## 6 Realized Demonstrator  
A demonstrator was realized in the laboratory in order to carry out preliminary tests of the feasibility, functionality, and reliability of the proposed solution. The demonstrator, shown in Figure 3, emulates a medium-voltage distribution radial line where there is a primary station protected by the substation breaker SB and controlled by the substation relay SR. The MV line is protected by three circuit breakers, CB1, CB2, and CB3, respectively controlled by three protection relays, PR1, PR2, and PR3. At the line boundary, the interconnection breaker IB is controlled by the Tie recloser TR.  
The digital protections should consist of the sensing element that continuously monitors the electrical quantities of the line to detect a fault; the sensing element is associated with the wireless network sensor node in LoRa technology and enables the exchange of information between the various protections. For the sake of simplicity and safety in the laboratory, and considering that the research activity aimed to demonstrate the effectiveness of the adoption of LoRa technology for the implementation of logic selectivity, in the realized demonstrator, the sensing element of the protection was not present, and only the nodes of the wireless network were considered and distributed. To assure the possibility of carrying out automatic tests on the system, fault detection was emulated by means of the output digital lines of a circuit controller that was mandated to transmit the fault occurrence to the selected wireless nodes.  
To realize the sensor nodes in LoRa technology, the components shown in Figure 4 were exploited. I-NUCLEO-SX1272D (by STMicroelectronics, Geneva, Switzerland) extension boards were used, which integrate a LoRa SX1272 transceiver, (Semtech, Camarillo, CA, USA) controlled by a NUCLEO-L073 RZ (STMicroelectronics, Geneva, Switzerland), based on a 32-bit ultralow-power microprocessor STM32L0 ARM (ARM Holding, Cambridge, UK) Cortex, which operates at a frequency of 32 MHz. Through Arduino-compatible connectors, the extension board was mounted on the L073 demo board, and a hardware stack was thus formed that allows physically connecting the microcontroller with the LoRa transceiver.  
In particular, several digital lines of the connector are used for the following tasks:  
Figure 3: Realized demonstrator for the experimental assessment of the system.  
* serial SPI communication for the transfer of the payload of the LoRa packets from the microcontroller to the transceiver and vice versa;
* control of the transmission and reception commands sent from the microcontroller to the receiver;
* control of the transmission and reception state sent from the receiver to the microcontroller to report the successful transmission or reception of a LoRa package.  
Therefore, the firmware running on the microcontroller of the sensor node first configures the transceiver with the desired LoRa communication parameters and, subsequently, thanks to the implementation of an appropriate state machine, realizes the logic selectivity, managing the different PR phases in collaboration with the other nodes of the network.