# Development of a Digital System for Monitoring Emergency Conditions in 20 kV Distribution Networks
## 3 Results
### Development of a Measurement Node  
The structural diagram of a stationary measurement node for zero-sequence voltage within a wireless data transmission network is shown in Figure 17.  
For the implementation of the scheme shown in Figure 17, a search was conducted for equipment with the lowest power consumption and energy efficiency features, such as sleep mode between occurrences of emergency modes in power transmission lines. As a result, two project implementation options were selected. The first option involves a signaling device that generates an alert signal when the threshold voltage is exceeded, indicating the presence of an emergency. The second option enables distributed remote measurements along the line to identify fault locations based on the maximum zero-sequence voltage levels. Figure 16: Diagram of the use of the base station in the data transmission network. Figure 17: Structural diagram of induced voltage measurements. Figure 15: Structure of the LoRaWAN wireless information technology network. The first option is based on the INA226 microchip [10], which can measure voltages in the range from 0 V to 36 V, independently of the internal power supply voltage, which may vary from 2.7 V to 5.5 V. The operating temperature range is from \(-40\)\({}^{\circ}\)C to 125 \({}^{\circ}\)C. The chip is powered by a standard 3.6 V battery, whose capacity supports its operation in power-saving mode for up to 3 years. The chip is set to trigger when a voltage threshold is reached, generating a signal through a dedicated alert digital output pin. This signal is sent to a special input of the VEGA CI-22 radio modem [11], where it is processed and transmitted wirelessly, indicating the occurrence of an emergency mode at the measurement location. The threshold is determined and programmed based on the following principle: at the measurement node's location, the operational range of zero-sequence voltage changes is between 2 and 7 V [12; 13; 14], and this voltage increases to values above 15 V during a single-phase earth fault [12; 15]. Therefore, the threshold for triggering the emergency alert is set at 11-12 V [16; 17]. The block diagram of the zero-sequence emergency voltage measurement node, implementing the first option and designed for use on a 20 kV cable line, is shown in Figure 18 (ZCT--Zero-Sequence Current Transformer). The radio modem operates on the EU868 and KZ865 frequency bands and also has a built-in battery [11]. The second option is based on the PZEM-017 DC voltmeter and the VEGA M-BUS radio modem. The block diagram of the measurement node, designed for use on a 20 kV cable line, is shown in Figure 19.  
In this scheme, the power source is the measuring transformer ZCT, which is installed remotely along the power transmission cable line. The alternating voltage from the ZCT output is fed to a rectifier, where it is converted into direct current voltage. This voltage is measured by the PZEM-017 DC voltmeter, which includes an analog-to-digital converter and an M-BUS interface. The digital measurement signal containing the voltage data is transmitted to the Tx transmission path of the VEGA M-BUS radio modem and sent wirelessly to the dispatcher's server. The radio modem is powered by a built-in battery  
Figure 19: Block diagram of the remote zero-sequence voltage measurement node for a 20 kV cable line. Figure 18: Block diagram of the zero-sequence emergency voltage detection node for a 20 kV cable line. with a service life of 10 years, and this battery provides power to the voltmeter through the +V connection. To save energy, there is the option to control the switching on and off of the voltmeter via a feedback channel, sending control signals from the modem to the voltmeter through the Rx connection. The equipment is housed in a weatherproof casing suitable for outdoor use in Kazakhstan's climatic conditions. The spectrum of the alternating voltage may contain many harmonic components, which could overload the analog-to-digital converter and distort the measurement results [18].