## 2 Experimental Schemes  
This research was performed using equipment from the core shared research facilities, namely the high-voltage research complex of the National Research University, the Moscow Power Engineering Institute, which allows the creation of artificial storm cells of negative polarity with a potential of up to 1.5 MV [21]. As a result, a strong electric field appears in the gap between the artificial thunderstorm cell of negative polarity and the grounded plane, which develops all the forms of spark discharge that are characteristic of a thunderstorm, including the leader and main stage. The measuring units of monitoring systems are usually located on transmission towers and phase wires. The measuring unit includes sensors for measuring main parameters, a processor module, and a data transmission system. Depending on their functional purpose, monitoring systems can use various types of sensors and transmitters (transceivers) of a rod or elongated type with sizes ranging from several centimeters to tens of centimeters. Sensors can have an almost spherical or cylindrical shape, or have a complex shape with protruding rod elements [5; 6; 8]. Since the structural elements of the transmission tower, as well as the phase and grounded wires, are also close in shape to a rod or cylindrical form, the following two experimental schemes with rod or cylindrical electrodes were chosen for the physical modeling used during the research. Two experimental schemes were used for a physical simulation of the spectrum. The first scheme simulated upward streamer discharges formed from the rod sensors (or antenna devices) or the effects of the electromagnetic radiation of the upward streamer discharges, formed on the rod elements of the transmission line design on the nearby model sensors (Figure 1). The second scheme simulated the analogous situation, but for the case of sensors (or antenna devices) of the cylinder type and of limited length, and the phase and ground wires (Figure 2). The distance between two grounded electrodes (one simulating the element from which an ascending streamer discharge is formed, and the other simulating the element on which the signal is induced by this discharge) was in the range of 15 to 30 cm. In the simulation, a monitoring system element and the places of formation of ascending streamer discharges on an overhead power transmission line were situated relatively close together. Figure 1: First scheme of experimental and measurement setup: 1—charged aerosol generator; 2—grounded electrostatic screens; 3—artificial thunderstorm cell; 4—rod electrodes; 5—upward streamer discharge; 6—shunts; 7,8—digital oscilloscope; 9—trigger generator; 10—system of photomultipliers; 11—digital photo camera; 12—photomultiplier; 13—CCD-camera; 14, 15—flat antennas. The conditions for the formation (the occurrence and subsequent development) of ascending streamer discharges originating from the grounded elements of monitoring systems in an external electric field created by a thundercloud and/or a descending lightning leader significantly depend on the nature of the distribution of the local electric field in the area near them [22]. Therefore, when conducting experimental studies, the radii of the vertices of rod model objects and the radii of model cylindrical objects varied in range from 0.3 to 2.5 cm for rod elements, and from 0.5 to 2.3 cm for extended elements. The height of the electrodes varied from 15 to 37 cm. Model rod electrodes were made of brass or aluminum; model cylindrical electrodes (tubes) were made of brass, aluminum, or steel. Elements of sensors, transmission towers, and phase and grounded wires were also made of these materials. As a result, the experiment simulated the formation of ascending discharge phenomena from elements of cyber-physical objects and systems with significantly different electric field amplification coefficients under the influence of atmospheric electricity and lightning.