1 Antenna Performance in High-Voltage Corona Marcin M. Morys Dr. Gregory D. Durgin School of Electrical and Computer Engineering Georgia Institute of Technology Friday, October 26th, 2012

2 Outline Motivation  High-Voltage Sensing  Corona Formation Theoretical Overview  Electromagnetic Wave Propagation Through Atmospheric Pressure Plasmas Simulation Results Conclusions

Traditional High-Voltage Sensing Current Transformers  Used in current monitoring  Oil used for insulation Advantages  Reliable communication link  Widely tested, well understood Disadvantages  Costly  Bulky  Limited location 3 Courtesy

Wireless High-Voltage Sensing Wireless Sensing  Air gap insulation Advantages  Inexpensive  Small  Versatile Disadvantages  Complex communication channel  Need to power sensor 4

Sources of Power Requirements  Easy installation  Limited maintenance  Reliable Battery Solar Direct to line Inductive coupling RF energy harvesting 5

High-Voltage Corona Induced by large voltage gradients  On the order of 3 MV/m in air at atmospheric pressure Simulation of E-field from PCB at 500kV, 5m 6 Ground 500kV

Electric Field Magnitude 7

Corona Noise Corona process involves avalanche of electrons  Moving charges  electromagnetic radiation Xiaofeng, et.al measured noise spectrum [1]  Radiated energy measured up to 650 MHz  Energy proportional to line voltage [2] Design RFID system to operate well above expected noise frequency bands  2.4GHz, 5.8GHz 8

Propagation Through Corona Layer 9 E m = electron mass x = electron displacement e = electron charge E = wave electric field strength v = collision frequency

Propagation Through Corona Layer Applying Maxwell’s equations, obtain the attenuation and propagation constants [3] At atmospheric pressure, electron collision frequency much higher than wave frequency [4] Complex permittivity given by 10 m = electron mass e = electron charge n = electron density v = collision frequency

Wave Attenuation By Corona 11

Simulation – Plasma Modeling Plasma can be modeled with separate electron density slabs [5] Corona layer electron density distribution based on corona simulations of Argon at atmospheric pressure [6]  10 layers of 0.1mm thickness 12

Simulation – Model, No Plasma 13

Simulation – Model, Plasma Model 14

Simulation – S11 15

Simulation – Input Impedance 16

Conclusions RFID is a promising technology for distributed high-voltage sensing Corona formation on antenna changes input impedance  Real impedance goes to 0 as charge density increases  Antenna reactance grows with charge density Experimental verification to be performed measuring backscattered power over 5.8 GHz band from tag in corona 17

Bibliography [1] H. Xiaofeng, L. Shanghe, W. Ming, and W. Lei, “Measurement and analysis of Electromagnetic Fields Radiated by Corona Discharge,” in International Symposium on Electromagnetic Compatibility [2] P. Sporn and A. C. Monteith, “Progress Report on Tidd 500-kV Test Project of the American Gas and Electric Company – Corona, Radio Influence, and Other Factors,” AIEE Summer and Pacific General Meeting, Vol. 69, pp , June [3] M. A. Heald and C. B. Wharton, Plasma Diagnositics With Microwaves. New York: Wiely, [4] M. Laroussi and W. T. Anderson, “Attenuation of electromagnetic waves by a plasma layer at atmospheric pressure,” International Journal of Infrared and Millimeter Waves, vol. 19, no. 3, 1998, pp. 453–464. [5] Li Wei, Qiu Jinghui, and Deng Weibo, “Radiation characteristics of planar reflector antenna covered by a plasma sheath,” in The 19th International Zurich Symposium on Electromagnetic Compatibility, Zurich, 2008, pp. 855–858. [6] T. Farouk, B. Farouk, D. Staack, A. Gutsol, and A. Fridman, “Simulation of dc atmospheric pressure argon micro glow-discharge,” Plasma Sources Science and Technology, vol. 15, p. 676,

Electric Field Magnitude 19

3D Antenna Pattern 20

Gain and Radiation 5.8 GHz Electron density (m^-3)Radiation efficiencyGain (dB) No Plasma55%4.46 n_max = 1e1850%4.15 n_max = 1e1939%3.02 n_max = 1e2023%

Antenna Dimensions 22 DimensionSize (mm) Antenna x12.85 Antenna y19.3 Antenna-ground plane height0.24 Board height1.5 Board length30