To solve the problem of low efficiency in ultrasonic detection of transformer windings

the ultrasonic coding spread spectrum ranging technology is introduced into the existing ultrasonic detection technology

and the propagation path and wave form conversion of the ultrasonic wave in the oil-transformer housing medium are analyzed. Being aimed at the echo modes of different position detections

a joint detection method of different types of ultrasonic probes is proposed

and an ultrasonic spread spectrum ranging system is designed. The system can simultaneously transmit multiple ultrasonic waves carrying different signals to the internal windings of the transformer. The surface structure of the winding inside the transformer is detected

and then the echoes are analyzed by generalized cross-correlation

so that the accuracy of the ultrasonic detection can reach ±0.064 mm. The system is used to detect the physical transformer model. The final experimental results show that the system can detect the internal structure of the transformer winding without affecting the normal operation of the transformer. And it is an efficient and online transformer winding detection method.