# On the Use of LoRa Technology for Logic Selectivity in MV Distribution Networks
## 8 Conclusions  
The suitability of LoRa technology as communication media for logic selectivity is reported in the paper. In particular, protective relay prototypes were realized that are capable of exchanging messages with each other. In order to assess the reliability and response times of the proposed solution, a laboratory demonstrator was created, with which two types of faults were emulated: (1) the poly-phase short circuit with current exceeding 600 A, for which it is necessary to clear the fault within 120 ms and is, therefore, the most critical to be managed and (2) the single-phase to earth fault, for which it is necessary to clear the fault within 450 ms. For both types of fault, tests were performed for different fault locations along the MV line.  
Figure 22: Management of a fault between PR2 and PR3 when a connection problem occurs.  
The experimental results show that for all of the types of faults examined, the system is able to isolate the faulty section of the network within the maximum allowed times. Moreover, the system is characterized by its robustness against possible communication problems, because even when the messages do not reach the relays, the fault is isolated within the established times.  
The laboratory assessment, thus, proved that LoRa technology seems to be suitable for achieving logic selectivity in all those cases in which optical fiber installation is not convenient from a cost point of view.  
It has to be noted that in wireless communication through LoRa technology, whenever the preamble, payload, SF, BW, and CR parameters are fixed and known for both the transmitter and the receiver, it is possible to remove the header from the message by disabling the implicit header mode and by reducing the value of \(T_{packet}\) to the SF and BW parity. This optimization allows for increasing the time symbol by setting a higher SF or a lower BW. For example, the 30.98 ms duration packet obtained with SF = 8, BW = 250 kHz, and an explicit header mode is reduced to a nominal duration of 25.86 ms by switching to the implicit header mode and leaving all the other parameters unaltered. In the case of failure 50.S3, this would mean that the spreading factor can be changed from 7 to 8 with a notable improvement in the receiver sensitivity and link budget.  
The ongoing research activity is focused on the optimization of packet transmission. Further tests, moreover, are going to be carried out in order to add to the indoor laboratory tests by conducting outdoor field trials. It is necessary, in fact, to assess the robustness of LoRa communication technology with respect to disturbances caused by the MV network. The use of a wireless system allows for the isolation of the path for data transmission from the path for power transmission. However, the LoRa transceivers can suffer from electromagnetic interference (EMI) caused by the corona effect [44]; in particular, EMI could deteriorate the signal-to-noise ratio and, thus, a different optimization of the LoRa packet parameters could be required to achieve the aim of increasing the receiver sensitivity.  
Conceptualization, A.L.; Data curation, F.B. and R.S.L.M.; Methodology, A.L., F.B. and R.S.L.M.; Supervision, L.A. and A.L.; Validation, A.L., F.B. and R.S.L.M.; Writing--original draft, F.B.; and Writing--review and editing, L.A., A.L. and R.S.L.M.  
This research received no external funding.  
The authors wish to thank Prof. [PERSON] for his scientific contribution and his precious suggestions. The authors wish to thanks [PERSON], [PERSON] and [PERSON] from ST Microelectronics at Arzano (Italy) for both the offered opportunity of testing the proposed transmission system on their STM32 microcontrollers and the technical support during the execution of the laboratory tests.  
The authors declare no conflicts of interest.