Performance Evaluation of Hybrid Bypass Protection of Hybrid Smart Transformers in a Substation Environment

The recent transformation in electric grid infrastructure have stressed conventional grid operation and control strategies. This demands that legacy devices perform a variety of advanced grid-support functions in addition to their traditional operation. A hybrid smart transformer (HST) and its protection scheme against damaging high voltages have been proposed. In this paper, the proposed hybrid bypass protection approach is evaluated in a typical substation protection environment involving a group of protection devices. These include a differential relay, feeder protection relay and a SEL-751A as a secondary bypass protection for the proposed HST module. The results from a laboratory-scale hardware prototype are included to verify the effectiveness of the proposed approach. The hybrid bypass protection approach performs as desired under all scenarios without interfering with the normal operation of typical substation protection devices. The proposed protection scheme finds a myriad of applications under the exponentially increasing inverter-based resources (IBRs) that demand robust protection against faults on the grid.