**6. Testing the GFSA model in γ radiation field**

A model of GFSA was constructed to allow the variation of relevant characteristics (chamber gas pressure and electrode materials), in order to test GFSA performance in various operational regimes. The experiment was performed as follows: (1) GFSA model was formed by choosing the appropriate material for the electrodes, placing the electrodes inside a gas-vacuum chamber, and setting the optimal electrode distance (**Figure 8A**); (2) the formed model (the gas tube) was connected to the gas-vacuum system with suitable valves, with a vacuum pump on one side and a steel gas supply cylinder on the other, and a pressure gauge; (3) the model was vacuumed by obtaining a stable pressure using valves leading to the vacuum pump and needle valves for grading the pressure; (4) the specific dose rate was set by appropriate positioning of the gas chamber relative to the source; (5) the electric circuit including the GFSA was closed; (6) the electrodes were conditioned by being kept in discharge state for a while in order to attain stable working conditions and insure the repeatability of measured results; (7) the value of prebreakdown current was measured, as the applied voltage was gradually increasing in each of the experimental dose rates; and (8) resetting the experimental system at a different working point (electrode material, gas pressure, dose rate) and performing a new measurement procedure. The scheme of the experimental setup is presented in **Figure 8B**. Measuring equipment consisted of (1) gas-vacuum chamber, (2) pressure gauge Speedivac, (3) steel cylinder with pressurized Ar gas, (4) vacuum pump Edwards 5, (5) DC high voltage source, CANBERRA, (6) AVOmeter Iskra MI 7006, (7) digital multimeter LDM—852 A, (8) variable resistance MA 2110, and (9) coaxial cables and connectors.

Examination of the GFSA was carried out in a gamma radiation field of 60Co. The average energy of the applied gamma quanta was 1.25 MeV. The absorbed dose rate in air was, respectively, 96, 960, and 1920 cGy/h. The distance between the examined overvoltage components and the radioactive source was, respectively, 272, 86, and 60 cm. The distance between electrodes was 0.5 cm. All tests were carried out at pressures of 4666.27 Pa (35 Torr) and 2666.45 Pa (20 Torr), at room temperature of 20°C. The electrodes were made either of aluminum, steel, or brass.

Investigation of the dependence of the prebreakdown current on the applied voltage was performed under various experimental conditions: in the absence of radiation and in a gamma radiation field (for aluminum, steel, and brass electrodes), under two gas pressures. The results for DC current are presented in **Figures 9–11**, for aluminum, steel, and brass, respectively. In captions shown in these figures, current *I*1 corresponds to the measurements without the radiation, current *I*2 corresponds to the γ radiation absorbed dose rate of 0.96 Gy/h, current *I*<sup>3</sup>

**225**

**Figure 8.**

*Influence of Gamma Radiation on Gas-Filled Surge Arresters*

corresponds to the γ radiation absorbed dose rate of 9.6 Gy/h, and current *I*4 cor-

Gamma radiation has a strong influence on the prebreakdown current in GFSA, as can be deduced from the presented graphs. Prebreakdown current is constant and independent of the applied voltage up to the value of the breakdown voltage in the absence of radiation. When 60Co source is present, a steady rise of the prebreakdown current is observed, increasing with the increase of applied voltage. For all three-electrode materials, the rise of the prebreakdown current is more pronounced as the γ radiation dose increases, effective under both of the tested pressures. Breakdown voltage increased under higher gas pressure regime. The highest breakdown voltages were obtained using brass electrodes (up to 450 V), and the lowest were obtained using steel electrodes (from 320 to 350 V, depending on the radiation dose). Under lower pressure, for both steel and brass electrodes, higher radiation doses resulted in lower breakdown voltages, with the highest breakdown voltage measured when no radiation was applied. For aluminum, the highest breakdown voltage was obtained under highest radiation dose. The best performing GFSA for

Pulse shape (volt-second) characteristic is shown in **Figures 12**–**14**, respectively, for aluminum, steel, and brass electrodes. Experimental data indicates the following: γ radiation leads to a decrease in standard deviation and the narrowing of pulse shape characteristics of the arresters, which leads to an increase in the response speed. Because of that, we can conclude that γ radiation improves the performance of GFSA. This phenomenon is most prominent in aluminum

responds to the γ radiation absorbed dose rate of 19.2 Gy/h.

*GFSA model (dimensions in mm, A) [23] and the scheme of the test cycle (B).*

DC current was the brass electrode under 20 Torr pressure.

*DOI: http://dx.doi.org/10.5772/intechopen.83371*

*Influence of Gamma Radiation on Gas-Filled Surge Arresters DOI: http://dx.doi.org/10.5772/intechopen.83371*

#### **Figure 8.**

*Use of Gamma Radiation Techniques in Peaceful Applications*

**6. Testing the GFSA model in γ radiation field**

*GFSA resistance versus applied voltage without radiation (A) and under γ radiation (B) [9].*

**Figure 7.**

A model of GFSA was constructed to allow the variation of relevant characteristics (chamber gas pressure and electrode materials), in order to test GFSA performance in various operational regimes. The experiment was performed as follows: (1) GFSA model was formed by choosing the appropriate material for the electrodes, placing the electrodes inside a gas-vacuum chamber, and setting the optimal electrode distance (**Figure 8A**); (2) the formed model (the gas tube) was connected to the gas-vacuum system with suitable valves, with a vacuum pump on one side and a steel gas supply cylinder on the other, and a pressure gauge; (3) the model was vacuumed by obtaining a stable pressure using valves leading to the vacuum pump and needle valves for grading the pressure; (4) the specific dose rate was set by appropriate positioning of the gas chamber relative to the source; (5) the electric circuit including the GFSA was closed; (6) the electrodes were conditioned by being kept in discharge state for a while in order to attain stable working conditions and insure the repeatability of measured results; (7) the value of prebreakdown current was measured, as the applied voltage was gradually increasing in each of the experimental dose rates; and (8) resetting the experimental system at a different working point (electrode material, gas pressure, dose rate) and performing a new measurement procedure. The scheme of the experimental setup is presented in **Figure 8B**. Measuring equipment consisted of (1) gas-vacuum chamber, (2) pressure gauge Speedivac, (3) steel cylinder with pressurized Ar gas, (4) vacuum pump Edwards 5, (5) DC high voltage source, CANBERRA, (6) AVOmeter Iskra MI 7006, (7) digital multimeter LDM—852

A, (8) variable resistance MA 2110, and (9) coaxial cables and connectors.

Examination of the GFSA was carried out in a gamma radiation field of 60Co. The average energy of the applied gamma quanta was 1.25 MeV. The absorbed dose rate in air was, respectively, 96, 960, and 1920 cGy/h. The distance between the examined overvoltage components and the radioactive source was, respectively, 272, 86, and 60 cm. The distance between electrodes was 0.5 cm. All tests were carried out at pressures of 4666.27 Pa (35 Torr) and 2666.45 Pa (20 Torr), at room temperature of 20°C. The electrodes were made either of aluminum, steel, or brass. Investigation of the dependence of the prebreakdown current on the applied voltage was performed under various experimental conditions: in the absence of radiation and in a gamma radiation field (for aluminum, steel, and brass electrodes), under two gas pressures. The results for DC current are presented in **Figures 9–11**, for aluminum, steel, and brass, respectively. In captions shown in these figures, current *I*1 corresponds to the measurements without the radiation, current *I*2 corresponds to the γ radiation absorbed dose rate of 0.96 Gy/h, current *I*<sup>3</sup>

**224**

*GFSA model (dimensions in mm, A) [23] and the scheme of the test cycle (B).*

corresponds to the γ radiation absorbed dose rate of 9.6 Gy/h, and current *I*4 corresponds to the γ radiation absorbed dose rate of 19.2 Gy/h.

Gamma radiation has a strong influence on the prebreakdown current in GFSA, as can be deduced from the presented graphs. Prebreakdown current is constant and independent of the applied voltage up to the value of the breakdown voltage in the absence of radiation. When 60Co source is present, a steady rise of the prebreakdown current is observed, increasing with the increase of applied voltage. For all three-electrode materials, the rise of the prebreakdown current is more pronounced as the γ radiation dose increases, effective under both of the tested pressures. Breakdown voltage increased under higher gas pressure regime. The highest breakdown voltages were obtained using brass electrodes (up to 450 V), and the lowest were obtained using steel electrodes (from 320 to 350 V, depending on the radiation dose). Under lower pressure, for both steel and brass electrodes, higher radiation doses resulted in lower breakdown voltages, with the highest breakdown voltage measured when no radiation was applied. For aluminum, the highest breakdown voltage was obtained under highest radiation dose. The best performing GFSA for DC current was the brass electrode under 20 Torr pressure.

Pulse shape (volt-second) characteristic is shown in **Figures 12**–**14**, respectively, for aluminum, steel, and brass electrodes. Experimental data indicates the following: γ radiation leads to a decrease in standard deviation and the narrowing of pulse shape characteristics of the arresters, which leads to an increase in the response speed. Because of that, we can conclude that γ radiation improves the performance of GFSA. This phenomenon is most prominent in aluminum

*Prebreakdown current versus applied voltage in γ radiation field with aluminum electrodes under pressure of 20 Torr (A) and 35 Torr (B) [9].*

#### **Figure 10.**

*Prebreakdown current versus applied voltage in γ radiation field with steel electrodes under pressure of 20 Torr (A) and 35 Torr (B) [9].*

**227**

**Figure 12.**

**Figure 11.**

*(A) and 35 Torr (B) [9].*

under γ radiation [9].

*Influence of Gamma Radiation on Gas-Filled Surge Arresters*

electrodes and least prominent in steel electrodes. Breakdown voltage deviation was least under the shortest pulses (1.2/50 μs) and highest under the longest ones (100/700 ms). All the observed changes lasted only during γ radiation and reversed as soon as the radiation exposure ceased. The best pulse shape characteristic was obtained for aluminum electrodes, which had its performance improved

*Pulse shape (volt-second) characteristic for aluminum electrodes in γ radiation field [9].*

*Prebreakdown current versus applied voltage in γ radiation field with brass electrodes under pressure of 20 Torr* 

*DOI: http://dx.doi.org/10.5772/intechopen.83371*

*Influence of Gamma Radiation on Gas-Filled Surge Arresters DOI: http://dx.doi.org/10.5772/intechopen.83371*

#### **Figure 11.**

*Use of Gamma Radiation Techniques in Peaceful Applications*

**226**

**Figure 10.**

**Figure 9.**

*20 Torr (A) and 35 Torr (B) [9].*

*(A) and 35 Torr (B) [9].*

*Prebreakdown current versus applied voltage in γ radiation field with steel electrodes under pressure of 20 Torr* 

*Prebreakdown current versus applied voltage in γ radiation field with aluminum electrodes under pressure of* 

*Prebreakdown current versus applied voltage in γ radiation field with brass electrodes under pressure of 20 Torr (A) and 35 Torr (B) [9].*

#### **Figure 12.**

*Pulse shape (volt-second) characteristic for aluminum electrodes in γ radiation field [9].*

electrodes and least prominent in steel electrodes. Breakdown voltage deviation was least under the shortest pulses (1.2/50 μs) and highest under the longest ones (100/700 ms). All the observed changes lasted only during γ radiation and reversed as soon as the radiation exposure ceased. The best pulse shape characteristic was obtained for aluminum electrodes, which had its performance improved under γ radiation [9].

#### **Figure 13.**

*Pulse shape (volt-second) characteristic for steel electrodes in γ radiation field [9].*

**Figure 14.** *Pulse shape (volt-second) characteristic for brass electrodes in γ radiation field [9].*

#### **7. Conclusion**

In this chapter, the influence of γ radiation on gas-filled surge arrester operation is discussed. An experimental model has been developed that allows easy modification of elements of the system and tests under different operational regimes. The experimental setup has also been used to test commercial GFSA components. An analytical method to describe GFSA pulse shape characteristics using area law has been established. These theoretical and empirical tools were used to measure and analyze the performance of different GFSA components exposed to combine n + γ and pure γ radiation.

The experiments demonstrated that γ radiation improves the performance of GFSA. This effect was observed both in commercial components and the experimental model. The prebreakdown current had increased when GFSA were exposed to γ radiation. Beneficial effect of γ radiation on pulse shape characteristics was determined: due to the reduction of standard deviation, response time of GFSA was improved. These effects were consistent under different insulating gas pressure regimes. Among the metals tested as electrode materials using the model, brass was the best performing one. The effects of γ radiation were lasting only as long as the components were exposed. The performance of GFSA under γ radiation makes them suitable for overvoltage protection of electronic circuitry constantly or occasionally exposed to that type of radiation.

**229**

**Author details**

Luka Rubinjoni1

Belgrade, Serbia

provided the original work is properly cited.

, Katarina Karadžić

\*Address all correspondence to: bloncar@tmf.bg.ac.rs

2

1 Faculty of Technology and Metallurgy, Innovation Center, University of

2 Faculty of Technology and Metallurgy, University of Belgrade, Serbia

and Boris Lončar2

\*

*Influence of Gamma Radiation on Gas-Filled Surge Arresters*

The authors declare no conflict of interest.

The authors thank the Ministry of Education, Science and Technological Advancement, Republic of Serbia, for supporting the research through projects no.

*DOI: http://dx.doi.org/10.5772/intechopen.83371*

**Acknowledgements**

171007 and 43009.

**Conflict of interest**

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,
