# Development of a Digital System for Monitoring Emergency Conditions in 20 kV Distribution Networks
## 3 Results
### Development of a Simulation Model for a Wireless Transmission Channel
Figure 12: Example of a signal scatter plot for PAM modulation of operational (**A**) and nonoperational (**B**) types. Figure 13: Example of a signal scatter plot for 16-QAM modulation of operational (**A**) and nonoperational (**B**) types. In the second case (see Figure 14B), with an increase in noise level, the signal-to-noise ratio drops to 2 dB, and errors are displayed in the error channel on the oscilloscope, resulting in unacceptable errors during signal transmission and rendering the transmission channel inoperable. For this type, we consider a signal-to-noise ratio of 3 dB as the boundary of a stable operational mode under conditions of intense noise interference [9]. Let us now compare the simulation results, which are reflected in Table 1.  
Thus, the wireless transmission technologies considered are inferior to LoRaWAN technology in terms of resistance to intense interference. Although this technology lags behind in data transmission speed compared to other faster technologies, it can reach up to 50 kbps [9], which is more than sufficient for transmitting a measurement signal formed by a zero-sequence voltage measurement node under intense electromagnetic interference from power lines and atmospheric phenomena. The topology of the LoRaWAN information technology network, \"Star within a Star,\" used for monitoring emergency conditions of urban 20 kV cable lines, is shown in Figure 15 (Notes: BS--Base station; SS--Substation) [9]. Taking into account the requirement for affordable equipment, we select devices from VEGA [11], which utilize LoRa transmission technology [9]. This company offers a comprehensive hardware and software solution for industrial wireless networks. To organize the data transmission network from measurement nodes to the central server, we use the VEGA BS-2 base station [11] (see Figure 16). \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**N**} & \multirow{2}{*}{**Name of Technology and Modulation**} & \multicolumn{2}{c}{**Extremely Low**} \\  & & **Signal-to-Noise Ratio, dB** \\ \hline
1 & PAM (ANT + technology) & 26.5 \\ \hline
2 & FSK (Bluetooth technology) & 9.5 \\ \hline
3 & QAM16 (ZigBee technology) & 16.0 \\ \hline
4 & PSK (ZigBee2.2 technology) & 19.5 \\ \hline
5 & LoRa (LoRaWAN technology) & 3.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of simulation data. Figure 14: Simulation results of the LoRa-modulated channel without errors (**A**) and the transmission channel becomes inoperable (**B**). For measurement nodes, radio modems CI-22 are used for the first option and VEGA M-BUS [11] for the second option. These modems are battery-powered, with a battery life of up to 3 years without replacement. Base stations can be placed at intermediate stations, connected to the existing dispatch system, as well as in suburban areas with centralized power supply and internet connectivity. Thus, the network structure will depend on the location of wireless access stations and the conditions for radio signal propagation.