Sampling data passageway switching method and device in main transformer protection of digitalized substation

The invention provides a sampling data passageway switching method and a device in main transformer protection of a digitalized substation, comprising the following steps: receiving an operational command to set a primary side constant value of a current transformer in an accessory pathway branch to be zero and existing from accessory pathway branch optical fiber; when starting back accessory pathway operation, receiving the operation command to set the primary side constant value of the current transformer in the accessory pathway branch to be a preset value, and connecting with the accessory pathway optical fiber; when carrying out the back accessory pathway operation, receiving the operation command to close a accessory pathway branch switch and switch off a main transformer branch switch; and then setting the primary side constant value of the current transformer to be zero and existing from a main transformer branch optical fiber. Meanwhile, the invention also provides the sampling data passageway switching device, comprising a receiving module, an accessory pathway branch module, a main transformer branch module and a line switch module. In the invention, main transformer differential construction is changed by switching a plurality of constant value regions, and the main transformer differential construction is ensured to always reflect the operation condition of the single system, thereby ensuring safe operation of a transformer protection device during the process of bypass replace protection for main transformer.