Problems of linear birefringence in optical glass current transformers with return-back optical paths

The effects of linear birefringence (LB) upon Bulk Glass Optical Current Transformers (BGOCTs) with return-back optical path designs, such as the Orthoconjugate Reflection (OCR)-typed, the Direct Reflection (DR)-typed and the Roof-prism Reflection (RPR)-typed BGOCT design, are theoretically analyzed and compared with that of the BGOCT with a single-loop optical path in this paper. The results show that the return-back dual-loop current sensing designs with conventional signal processing scheme of "-/+" cannot eliminate the harmful effects of the LB thoroughly, if suitable signal processing schemes which can separate the LB from Faraday effect are not used.