A slot structure was combined with a discharge electrode to limit incident high-power microwaves via the integration of plasma discharge. At the target resonating frequency of 9.45 GHz, the surface current was concentrated at an electrode, and the electric field was enhanced by the proposed design to lower the response power level of the incident signal. When a low-power signal is injected, plasma is not generated, and the incident wave travels without insertion loss. Double-stage slot structures were utilized to broaden the band-pass characteristics in the frequency domain, and the demonstrated plasma limiter exhibited an insertion loss of 1.01 dB at 9.45 GHz. The xenon gas pressure was optimized with the shortest distance of 100 µm between the upper and lower electrodes to reduce the discharge power of the plasma. In the case of a high-power signal input, as xenon-gas breakdown occurred, the transmitted signal was close to zero, and most of the high-power signal was reflected with a blocking efficiency of 40.55 dB.

The audible noise (AN) generated by corona discharge from a full-scale, high-voltage direct-current (HVDC) transmission line was evaluated over a one-year period from December 2017 to November 2018. The double bipolar HVDC transmission line using a metallic return conductor was demonstrated using a full-scale tower having a height of 21 m in Gochang, Korea. The measured AN in an outdoor environment was statistically evaluated and compared in different seasons and weather conditions. The A-weighted spectrum of the HVDC corona noise exhibited a greater distribution than the background noise above 1.0 kHz in the frequency domain. Various background noises were considered and eliminated to improve the measurement accuracy. The highest AN levels were exhibited during the spring season. Individuals in the age range of 18–60 years were randomly selected to conduct a human-perception test. The results indicated that 15% of the participants became aware of the AN from the corona discharge when it was >5 dBA greater than the background noise. The AN was <36 dBA when the conductor surface gradient was <18 kV/cm with a six-bundle sub-conductor.

A slot structure was combined with a discharge electrode to limit incident high-power microwaves via the integration of plasma discharge. At the target resonating frequency of 9.45 GHz, the surface current was concentrated at an electrode, and the electric field was enhanced by the proposed design to lower the response power level of the incident signal. When a low-power signal is injected, plasma is not generated, and the incident wave travels without insertion loss. Double-stage slot structures were utilized to broaden the band-pass characteristics in the frequency domain, and the demonstrated plasma limiter exhibited an insertion loss of 1.01 dB at 9.45 GHz. The xenon gas pressure was optimized with the shortest distance of 100 µm between the upper and lower electrodes to reduce the discharge power of the plasma. In the case of a high-power signal input, as xenon-gas breakdown occurred, the transmitted signal was close to zero, and most of the high-power signal was reflected with a blocking efficiency of 40.55 dB. The demonstrated result will be useful to protect the receiver of a radio detection and ranging system from the high power microwave.

The induced voltage and current were measured while changing the contact resistance of gloves and the resistance between the shoes and ground, respectively, to evaluate the human impact of the voltage induced by overhead power lines. The major parameters were extracted using a formula, and the results were compared using a simulation tool. When exposed to an electric field of 4kV/m, an induced voltage between the human body and the ground of approximately 600 V was generated. The maximum value and duration of the discharge current varied according to the change in the gloves and shoe resistance. In addition, the induced voltage-reduction effect through the shielding wire was also confirmed.