Novel optical current sensor for metering and protection in high power applications

ABSTRACT

A clamp-on optical current sensor prototype for metering and protection applications in high power systems was developed and characterized. The system is based on the Faraday effect in a low birefringence, high Verdet constant, 8 cm long SF57 Schott glass prism. It was incorporated in a nylon casing suitable for clamp-on applications in the power line. The sensor operation was tested at 630 nm, 830 nm, and 1550 nm to access its applicability in remote interrogation via fiber links. Optimal operation at 830 nm is reported with a linear response up to 65.28kA, with 0.1 or 0.2 accuracy class considering a nominal currents of 1.2 and 0.3 kA (root mean square), respectively. Twelve calibrations procedures performed over six days showed an estimated maximum error of 11 m A. Preliminary measurements were made from 40 to 400 Hz. The sensor was exposed to transient signals less than 10 µs that demonstrated its use in protection applications.

KEYWORDS:

• Digital processing
• Faraday effect
• high-power grid
• optical current sensor