Sensor, device and monitoring method for on-line monitoring of leakage magnetic field of transformer

The invention provides a sensor, a device and a monitoring method for on-line monitoring of a leakage magnetic field of a transformer, and belongs to the technical field of transformer monitoring. The sensor comprises at least two optical fiber collimators, a magneto-optical crystal, a hollow glass tube and at least two magnetic flux collectors, the magneto-optical crystal is fixed in the middle of the inner side of the glass tube; the two optical fiber collimators are respectively fixed at the two ends of the opening of the glass tube, and the positions of the optical fiber collimators are adjusted and determined by the micro-mechanical system; the outer surface of the glass tube is sleeved with the two magnetic flux collectors, and the two magnetic flux collectors are symmetrically arranged on the two sides of the magneto-optical crystal. The sensor provided by the invention can be installed in the transformer, has the advantages of high sensitivity, high insulation level, no electromagnetic interference an