ABSTRACT
Optical current and voltage sensors have been developed predominantly as alternatives to conventional instrument current and voltage transformers in alternating current (ac) electric power transmission and distribution. Further fields of application include high voltage direct current (HVDC) power transmission, railways, electro-winning of metals and further industrial uses, scientific applications, e.g., in plasma physics and particle accelerators, and others. Conventional instrument current and voltage transformers for high voltage (HV) substations, commonly referred to in the industry as CT and VT, respectively, are bulky, typically oil and paper insulated devices (SF6 gas insulation is an alternative), and heavy – with weights as large as several tons. By contrast, the all-dielectric nature of optical sensors drastically reduces size and weight, inherently insulates secondary equipment from high voltage, and provides new options for the integration of current and voltage measurement in HV systems. The oil-free insulation eliminates any risk of explosive failure, e.g., during earthquakes. Furthermore, the sensors’ large bandwidth and absence of phenomena like magnetic saturation or ferro-resonances provide a more accurate image of the primary current or voltage waveforms, especially during faults, and the sensors’ digital electronics is in line with modern digital substation communication and control.
