Design of Optoelectronic Transformer for Its Application in Traveling Wave Protection of Power Grid

Abstract

As an important foundational link of the power system, the reliable measurement and accurate data of the metering module are the important foundation and support for energy metering. As a new type of optoelectronic current transformer, magneto-optical crystal-based optoelectronic current transformer effectively avoids the defects of traditional electromagnetic current transformers and becomes an ideal equipment for measurement in power systems. This paper proposes an improvement method to enhance the temperature stability of optoelectronic current transformers, using a magneto-optical crystal sensor head based on Faraday effect to limit the fiber length to within 140 m. It considers the influence of a uniform temperature field on magneto-optical crystal materials to process data reasonably to ensure normal incidence of the incident beam. The magneto-optical crystal material in the non-uniform temperature field has non-uniform deformation due to thermal expansion and cold contraction. Here, a Karamay No. 45 cooling oil is used for filling and sealing. In the experiment, the temperature stability of the current transformer is tested. Firstly, the wiring method is designed. Then, the corresponding test system is designed. After improvement, there is no drift phenomenon in the ratio difference and angle difference of all points of the photoelectric current transformer within the testing temperature range, and the error difference is stable. The principle of identifying faults within the area is elaborated, and a directional longitudinal traveling wave protection method for direct-current transmission lines is designed based on the differential output characteristics of the designed photoelectric transformer. Through experiments, the transformer in this design can effectively identify potential traveling wave fault types and fault phases.