In the field of power transformer protection there is provided a method of protecting a power transformer comprising the steps of: (a)monitoring an external fault indication signal (12A, 12B, 12C); (b)carrying out locally a fault determination; (c)carrying out locally an inrush current determination; and (d)issuing a final trip signal (48) to protect the power transformer if: (i)the external fault indication signal (12A, 12B, 12C) identifies that a fault has occurred and the locally carried out fault determination confirms that a fault has occurred; or (ii)the external fault indication signal (12A, 12B, 12C) identifies that a fault has occurred and the locally carried out fault determination identifies that no fault has occurred but after a predetermined delay the locally carried out inrush current determination confirms the absence of an inrush current.