A high dynamic range magnetooptic current transformer with advanced signal processing

In the power industry, current must be measured for metering and protection purposes. For such measurements, the use of magnetooptic current transformers offers many advantages. Conventional sensors, however, need two magnetooptic transformers to realize the required high dynamic range. Using a combination of analog and digital signal processing algorithms, the inherent low noise of the photonic input signals is maintained. The system design is based on a rigorous investigation and optimization of the error sources in the signal processing chain. The validity of this approach was confirmed by a demonstrator which achieved a dynamic range from 0.05 to 100 times the rated current and whose rms error was less than 0.5 %.