Fiber-optic current sensing using a sensor with exchangeable sub-modules

摘要

A fiber-optic current sensor includes a measuring unit having a light source and a light detector, and a sensing head having a sensing fiber wound around a conductor and a retarder connected to the sensing fiber. The scale factor as a function of current of the fiber-optic current sensor is described by the product of two scaling functions fe′ and fs′ for the measuring unit and the sensing head, respectively. The data describing the scaling functions fe′, fs′ is stored in a memory of the measuring unit, while the data describing the scaling function fs′ is also stored in a memory of the sensing head. Providing two such memory devices allows to store the scaling functions fe′ and fs′ separately, thereby turning the control unit as well as the sensor head into easily replaceable modules.

主权项

1. A method for operating a fiber-optic current sensor measuring a current I in a conductor, wherein the current sensor includes:
a sensor head having a sensing fiber wound around the conductor and a retarder connected to the sensing fiber; a measuring unit having a light source and a light detector; and a polarization maintaining fiber connecting the sensor head to the measuring unit, wherein the method comprises: sending light from the light source through the sensor head; measuring, by means of the light detector, a signal S derived from light returning from the sensor head; and calculating the current I from
I=(S/g)·fe′(S)·fs′(S) wherein: fe′(S) is a scaling function of the measuring unit depending on the signal S; fs′(S) is a scaling function of the sensor head depending on the signal S; and g is a constant independent of the signal S, wherein a phase shift Δφ is measured in the sensing fiber of the sensor head, and the sensor head scaling function fs′ is defined by Δφ/(4φF), where 4φF is a defined phase shift.