The on-site calibration of fiber optical current transformer is often influenced by the environmental factors, resulting in certain deviation of results. We proposed the sources of uncertainty in this paper, which mainly include: the uncertainty uA(ε) induced by the error of standard FOCT, the uncertainty uB(ε) induced by the field environment and improper operation method, and the uncertainty uC(ε) induced by the calibrator unit. In further, the uB(ε) is analyzed detailed. This component is mainly produced by temperature, vibration and inhomogeneous magnetic field. The experimental results show that the errors of temperature, vibration and inhomogeneous magnetic field are 0.020%, 0.051% and 0.049%, respectively. Finally, we can calculate the synthetic standard uncertainty and expanded uncertainty of the DC calibration (P=99%) are 4.8×10-4 and 1.4×10-3, respectively. And the synthetic standard uncertainty and expanded uncertainty of the AC calibration (P=99%) are 5.6×10-4 and 1.6×10-3 respectively. The results show that the scheme can satisfy the uncertainty requirements of the direct comparison method (0.5S level).
A reflection fiber optic current transformer (FOCT) based on equal-ampere-turn method and range self-expanding approach is proposed to measure ultra-high current in this paper. A flexible sensing coil is utilized in FOCT to suit the needs of the measurement environment and to enable installation and removal. At the same time, two significant difficulties have been raised: one is the nonlinear difficulty introduced by the equal-ampere-turn approach and the range self-expanding method; the other is the non-uniform magnetic field errors generated when the flexible sensing coil is put on site, including conductor eccentricity and non-closed angle, which can amplify the nonlinear problem. Therefore, in order to eliminate the non-uniform magnetic field error, a closed structure of λ/4 waveplate and reflector is designed for the reflection structure, and the sensing coil skeleton is optimized. Experimental results show that the FOCT with closed structure and sensing coil skeleton has a good range self-expanding ability. The accuracy at rated current can also fulfill the requirement of 0.2S. Finally, the FOCT was subjected to a temperature cycle test in the range of -40°C to 70°C, with a ratio error of less than ±0.2%. So the method's validity and feasibility are confirmed.
When the λ/4 waveplate of fiber optic current transformer (FOCT) is set in the variable temperature environment, there will be a polarization error during the process of optical signal propagating in the fiber, which will decrease the accuracy of current measurement. In this paper, in order to reduce the influence of temperature change on the accuracy of current measurement, we firstly analyzed the influence mechanism of temperature change on λ/4 waveplate in FOCT, and then used a variable-rate spun fiber (VRSF) as a sensing coil instead of a λ/4 waveplate with circular polarization maintaining fiber (CPMF) as a sensing coil. After that, the mechanism of temperature insensitivity of VSSF was explained. Finally, the two FOCT systems with different fiber sensing coils were tested under variable environment, which proved that the fiber sensing coil using the VSSF in FOCT can effectively resist the interference of the external environment temperature change. As a result, the accuracy of current measurement can be kept within 0.2S degree under the variable temperature environment of -20-70°C.
A fiber optic current sensor utilizing orbital angular momentum (OAM) beam is proposed in this paper. The superposition principle of composite OAM beam is deduced, and the current sensing process is derived by Jones matrix. The current is measured by detecting the rotation angle of petal-like patterns formed after the composite OAM beam through the polarizer. The reflective structure of the sensor doubles the rotation angle, which improves the measuring sensitivity and the reciprocity of the system. Through simulation analysis, we verified that the rotation angle changes linearly with the increase of current, and the sensitivity of the proposed sensor is 0.1254°/A. Finally, on this basis, the angle recognition method is optimized, and the final measurement error is less than ±0.2% in the range of 50A-1500A. .
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.