# Analysis of the Possibility of Using Drill-Type Electrodes for Air Ionization
## 2 Measuring System, Characteristics of Drill-Typed Electrodes, Research Programme
These voltages were measured for each of the eleven pairs of drill-type electrodes. For each pair of drill-type electrodes and the adopted distance, measurements were made three times. Arithmetic mean was calculated from the obtained values, which was averaged, converted through a test transformer gearbox (500) and rounded to two decimal places. In this way, results under further analysis were expressed in kilovolts. For averaged results, their scatter was determined by determining the standard deviation. Measurements for each pair of drill-type electrodes were made in the range of distance from 2 cm to 16 cm, increasing the distance every 2 cm. In this way, eight measuring points were obtained for each pair of drill-type electrodes and for each characteristic voltage. The results of the electrical strength measurements of the air were affected by the atmospheric  
Figure 3: General view of 11 pairs of drill-type electrodes selected for testing of different diameters d (in millimeters): 0.5—(**a**); 0.6—(**b**); 0.7—(**c**); 0.8—(**d**); 0.9—(**e**); 1.0—(**f**); 1.1—(**g**); 1.2—(**h**); 1.3—(**i**); 1.4—(**j**); 1.5—(**k**). Figure 2: The sketch of the drill-type needle electrode. The diameter 2R of the needle part is 1 mm, length L\({}_{1}\)—8.5 mm, handle diameter \(\Phi\)—3.175 mm, total length 38.2 mm. conditions under which the measurements were made. Their impact was taken into account when calculating the appropriate correlation coefficient. In order to obtain reference characteristics to allow for the comparison of results relating to the systems with the drill-type electrodes, measurements were also made in two systems of needle electrodes. Needle electrodes with needle angles of 45\({}^{\circ}\) and 20\({}^{\circ}\), respectively, were used. The way of performing tests in these systems was the same as in systems with drilling elements. Results of Measurements of Characteristic Voltages of Partial Discharges Generated between Drill-Type and Needle Electrodes in Different Geometries  
Figure 5 shows the results of the measurements of voltages U\({}_{\text{o}}\), U\({}_{\text{s}}\) and U\({}_{\text{b}}\) as a function of the distance between electrodes, obtained in the systems of drill-type electrodes of different diameters d: a--0.5 mm, b--0.6 mm, c--0.7 mm, d--0.8 mm, e--0.9 mm, f--1.0 mm, g--1.1 mm, h--1.2 mm, i--1.3 mm, j--1.4 mm, k = 1.5 mm. For comparison of the results obtained in the measurements with the use of drill-type electrodes (Figure 5), Figure 6 presents results of the measurements of characteristic voltage discharges generated in the needle spark gaps, with two different needle angles: \(\alpha\) = 20\({}^{\circ}\) and \(\alpha\) = 45\({}^{\circ}\). Figure 4: Spark gap with drill-type electrodes (2R = 1 mm), prepared for measurements. Figure 5: _Cont._  
Figure 5: Comparative characteristics of voltage: sparking voltage, corona voltage and breakdown voltage for a needle—needle system with drill-type electrodes of different diameters d (in millimeters): 0.5—(a); 0.6—(b); 0.7—(c); 0.8—(d); 0.9—(e); 1.0—(f); 1.1—(g); 1.2—(h). 1.3—(i); 1.4—(j); 1.5—(k). Figure 8: _Cont._  
Figure 1:0 The value of the corona voltage, sparking voltage and breakdown voltage for the systems of drill-type electrodes of different diameters: (**a**) distance 8 cm, (**b**) distance 12 cm, (**c**) distance 16 cm. Figures 9 and 10 show the spatial distribution of the obtained results. In this approach, the results obtained in the measurements made in systems with drill-type electrodes, as well as in systems with needle electrodes, are presented in comparison. The combined analysis of the presented results makes it possible to compare U\({}_{\alpha}\), U\({}_{s}\), U\({}_{b}\) voltages, and consequently, to compare the effectiveness of their ionization. It also enables the comparison of drill-type and needle spark gaps of different geometries in this respect.