The invention relates to a power
transformer winding fault online monitoring device and a diagnosis method, and belongs to the technical field of power
transformer fault diagnosis. The power
transformer winding fault online monitoring device is characterized in that the output end of a
voltage sensor and the output end of a
current sensor are connected to the input end of a synchronous
signal sampling circuit, the output end of the synchronous
signal sampling circuit and the output end of an
ultrahigh frequency sensor are connected to the input end of a
signal conditioning circuit, the output end of the
signal conditioning circuit is connected to the input end of a DSP (
Digital Signal Processor) through an A / D conversion circuit, the output end of the DSP is connected with a PC (
Personal Computer) through a CPLD (
Complex Programmable Logic Device), and the PC is connected with an alarm. The diagnosis method comprises the steps of acquiring ultrasonic signals at the wall of a
transformer oil tank, and finally acquiring coordinates of
partial discharge through
signal conditioning and A / D conversion and through DSP denoising; acquiring
voltage signals and current signals,
processing the signals, building an online short-circuit
reactance model, acquiring a short-circuit
reactance value of each phase winding, comparing the acquired short-circuit
reactance value with a corresponding historical fault-free short-circuit reactance value so as to acquire the short-circuit reactance change rate, judging a range, in which the change rate is located, of an upper limit threshold and a
lower limit threshold, and judging the winding operating state.