Hybrid fiber-optic current sensor for remote monitoring of electrical submersible plant

This paper gives details of the design, construction and experimental evaluation of the optical current sensor developed specifically to monitor electrical submersible pumps operating several tens of km away from an oil rig. The proposed sensor is of a hybrid construction, and uses an optical voltage-to-strain transducer to monitor a specially designed current transformer. In this application, the voltage-to-strain transducer is realized using a novel approach: it employs a fiber Bragg grating (FBG) bonded to a stack of multiple piezoelectric elements, with their respective electrodes connected in parallel. This approach greatly increases the measurement sensitivity; thus, the FBG can be interrogated using a classic scanning filter configuration rather than the interferometric technique. Moreover, since the absolute wavelength information is preserved, this brings the advantage of the simultaneous temperature measurement capability and enables the straightforward multiplexing of several sensors on one optical fiber.