Abstract

In the power generation industry it is important to measure the amplitude, frequency and phase of the generated currents in electricity distribution networks. This measurement is required for fiscal reasons and also to establish if there are faults in the network. The conventional method of current measurement is based upon a 'current transformer' which is deployed around the current carrying wire commonly termed a 'bus bar'. As the bus bar is normally at very high potential, for example, 440,000 volts, insulation between the current transformers secondary and the permeable core which surround the bus bar must be extremely high as the signals generated by the current transformer are monitored in the central control unit of the power station. Hence the current transformer is both large and extremely expensive. Although considerable effort has been devoted to the development of optical fibre current sensors based upon the Faraday effect, the performance of these sensors is often limited by problems associated with bend-induced birefringence, temperature and wavelength sensitivity of the Verdet constant and the high sensitivity to vibrational noise [1].

© 1992 Optical Society of America