Theoretical analysis of the effects of linear birefringence upon optical glass current transformers with different optical designs

The effects of linear birefringence (LB) upon bulk glass optical current transformers (BGOCTs) with different optical path designs, such as the orthoconjugate reflection (OCR)-typed, the direct reflection (DR)-typed and the roof-prism reflection (RPR)-typed BGOCT designs, 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.