# 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 9: Model of a Wireless Transmission Channel with FSK Modulation Under Intense Noise Impact. reception stages. In this case, the signal is distorted by noise, resulting in signal transmission with unacceptable errors, i.e., the transmission channel becomes nonoperational. Based on the simulation results, it can be concluded that for FSK modulation, the threshold value of the signal-to-noise ratio Eb/N\({}^{0}\), expressed in dB, at which the system becomes nonoperational at BER = 10\({}^{-8}\), lies in the range of 9-10 dB, with an approximate value of 9.5 dB. Next, we consider the simulation results of the transmission modes for a channel with PSK modulation (Figure 11) for two cases: operational and nonoperational. In the first case, the SNR is 20 dB, and the oscilloscope does not display any signals in the error channel. In Figure 11A, the signal scatter plot shows the effects of noise on the code combinations, but their boundaries do not merge, indicating error-free signal transmission. In the second case, the SNR is 19 dB, and the oscilloscope displays signals in the error channel. In Figure 11B, the signal scatter plot shows the effects of noise on the code combinations, and their boundaries merge, resulting in signal transmission with unacceptable errors, i.e., the transmission channel becomes nonoperational. Based on the simulation results, it can be concluded that for this modulation, the threshold value of the signal-to-noise ratio (Eb/No), expressed in dB, at which the system becomes inoperable at BER = 10\({}^{-8}\), lies in the range of 19-20 dB, and is approximately 19.5 dB. Let us now consider the simulation results of channel transmission modes with PAM modulation for two cases: operational and nonoperational. Figure 12 presents the simulation results of the channel with PAM modulation in two modes--normal (Figure 12A) and failure (Figure 12B)--in the form of signal scatter plots. In the first case, the signal-to-noise ratio is 27 dB. The scatter plot shows the effects of interference on the code combinations (see diagram in Figure 12A), but their boundaries do not completely merge, the signal transmission occurs with unacceptable errors. Based on the simulation results for the channel with PAM modulation, it can be concluded that the threshold value of the signal-to-noise ratio (Eb/No), expressed in dB, at which the system becomes inoperable at BER = 10\({}^{-8}\), lies in the range of 26-27 dB, and is approximately 26.5 dB. Figure 13 presents the simulation results for the 16-QAM modulation. Figure 11: Example of a signal scatter plot for PSK modulation (BPSK—binary PSK) of operational (**A**) and nonoperational (**B**) types. Let us examine the simulation results for transmission modes in two cases: operational and nonoperational. In the first case (see diagram in Figure 13A), the signal-to-noise ratio is 17 dB. The scatter plot shows the effects of interference on the code combinations, but their boundaries are clear and do not merge, allowing error-free signal transmission. In the second case (see diagram in Figure 13B), the signal-to-noise ratio is 15 dB. The scatter plot shows the effects of interference on the code combinations, and although their boundaries do not completely merge, the signal transmission occurs with unacceptable errors, rendering the transmission channel inoperable. Based on the simulation results for the channel with QAM modulation, it can be concluded that the threshold value of the signal-to-noise ratio (Eb/No), expressed in dB, at which the system becomes inoperable at BER = 10\({}^{-8}\), lies in the range of 15-17 dB, and is approximately 16 dB. We now simulate the transmission channel for LoRa (Long Range) technology [9] for both operational and nonoperational cases. In the first case, the signal-to-noise ratio is 4 dB, which corresponds to a high level of noise interference; however, no errors are displayed in the error channel on the oscilloscope, allowing error-free signal transmission (see Figure 14A).