Complete Model Development for an Optical Current Transformer

Optical current transformers/transducers (OCTs) produce digital and analog signals. In recent years, they have become more available, playing an increasingly important role in electric power grid upgrades. This requires developing accurate models for relay testing and relay performance evaluations to ensure that the system equipment is safe. This study presents several models developed for OCT: analog, digital, and complete models. It applies previously studied and presented frequency-response characteristics to develop a transfer function using a complex curve-fitting method. An analog circuit model is constructed from the developed transfer function via a network synthesis method. A digital model is presented by transforming the developed transfer function into a digital domain transfer function using bilinear transformation. The digital model implementation is performed by the direct form I block diagram. The optics model and electronics model of the device are developed separately and are then combined to present a complete model. The Jones calculus method is used for optical modeling, and a developed transfer function is used for electronics modeling. All of the developed models are verified through the frequency-response results and tested with PSpice and Matlab Simulink programs. The results show that the developed models can be used as legitimate OCT models.