Abstract
When applying an optical current transformer (OCT) to direct current measurement, output signals exhibit a low signal-to-noise ratio and signal-to-noise band overlap. Sinusoidal wave modulation is used to solve this problem. A double correlation detection algorithm is used to extract the direct current (DC) signal, remove white noise and improve the signal-to-noise ratio. Our sensing unit uses a terbium gallium garnet crystal in order to increase the output signal-to-noise ratio and measurement sensitivity. Measurement errors of single correlation and double correlation detection algorithms are compared, and experimental results showed that this measurement method can control measurement error to about 0.3%, thus verifying its feasibility.
Highlights
direct current (DC) transmission is an important means to realize interconnected power grids and transmission that has ultra-high voltage, large capacity, and low-loss for long distances
In order to address the problems of the overlapping of signal-to-noise bands and low signal-to-noise ratio (SNR), using the randomness of noise in the optical current transformer (OCT), this paper proposes a double correlation detection algorithm based on autocorrelation and cross-correlation operations in order to improve the measurement accuracy
A double correlation detection algorithm is used for signal processing, and on the basis of this, the terbium gallium garnet (TGG) crystal is used as a sensing material to increase the output SNR, which can, as a result, effectively reduce the measurement error and improve the DC measurement accuracy and sensitivity
Summary
DC transmission is an important means to realize interconnected power grids and transmission that has ultra-high voltage, large capacity, and low-loss for long distances. Authors [14] used a digital lock-in amplifier based on correlation detection principle to separate the signal and noise and detect the signals to achieve noiseless signal These denoising methods can filter out noise in DC measurement to some extent. These methods cannot effectively filter out white noise, and cause the signal-to-noise characteristics of the output signal is analyzed, and a double correlation detection large errors in the measurement results. The basic principles and structure of the OCT are provided, the correlation detection—are compared by simulation The feasibility of this measurement method is output characteristics of different sensor materials such as magneto-optical crystal and magnetoverified by building a hardware platform.
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