A fiber-optic current sensor for lightning measurement applications

Abstract

An optical-fiber sensor based on Faraday Effect is developed for measuring total lightning electric current. It has many unique capabilities not possible with traditional current sensors. Designed for aircraft installation, the sensor is lightweight, non-conducting, structure-conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can also be used on windmills, lightning towers, and can help validate lightning detection network measurements.Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. The broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with about 60 dB dynamic range.Three sensor systems were built with different sensitivities from different laser wavelengths. Operating at 850nm, the first system uses twisted single-mode fiber and has a 150 A -150 KA range. The second system operates at 1550nm, uses spun polarization maintaining fiber, and can measure 400 A -400 KA. Both systems were validated with rocket-triggered lightning measurements and achieved excellent results when compared to a resistive shunt. The third system operates at 1310nm, uses spun polarization maintaining fiber, and can measure approximately 300 A -300 KA. High current measurements up to 200 KA were demonstrated at a commercial lightning test facility. The system was recently installed on an aircraft and flown near icing weather conditions.

Establishing a disruptive new capability for NASA to fly UAV's into hazardous conditions

“…Figure 4 shows the HU-25C Faraday system installation. [5] NASA LaRC lightning sensor researchers will team with NASA AFRC Fiber-Optic instrumentation specialists to reduce the Mass, Volume and Power (MVP) requirements of the Faraday lightning current sensor for use on a small UAV. NASA AFRC's state-of-the-art Fiber Optics and Systems Integration Laboratories are ideally suited to transition the system to an all-fiber design.…”

Research of Magnetic Shielding on the Closing Gap of Optical Fiber Current Sensor

“…The electric current is the most basic process parameter in various industrial applications, such as high-voltage direct current (HVDC) projects [1,2] and nonferrous metallurgy [3][4][5][6]. Accurately measuring the current is an important task.…”