In order to realize the passive vibration monitoring of power transformer, a vibration energy extraction method of power transformer based on PMN-PT piezoelectric ceramic series parallel structure, is proposed in this paper.
Firstly, the vibration signal on the surface of a running 220 kV power transformer is measured by a vibration sensor, and the measured signal is Fourier transformed. Secondly, Sm-doped-PMN-Pt piezoelectric ceramics synthesized by high-temperature solid-state treatment are selected as energy extraction materials, which can obtain the best high-voltage electrical and dielectric properties. They are combined in a specific series and parallel way to form a piezoelectric energy collection device. Thirdly, an improved parallel double intermediate capacitor energy recovery control circuit is proposed to improve the extracted power and to regulate the output voltage. Finally, an experimental platform is built to verify the vibration energy extraction method of power transformer, which consists of energy collection device, signal generator, power amplifier, vibration exciter and oscilloscope.
According to the time-frequency domain signal after Fourier transform, the center frequency of power transformer vibration signal is concentrated at 100 Hz, and the vibration amplitude at the lower part of the transformer is the largest. The actual output power of the piezoelectric energy collection device is greater than 500 µW. The energy recovery control circuit can greatly improve the extracted power, and the maximum output power is independent of the load. It can provide a stable voltage of 3.6 V for the back end, which is enough to meet the power supply demand of the vibration sensor.
In this paper, the PMN-PT piezoelectric ceramics with series and parallel configuration collect the vibration energy of the power transformer and converts it into electric energy to supply power for the low-power vibration sensor. In this way, a self-powered vibration sensor of power transformer is realized. It provides a passive monitoring method for the vibration signal on the surface of the power transformer box, which is used to judge the operation status of the iron core and winding in power transformers.

Transformer vibration monitoring,Passivity,Piezoelectric ceramics,Series and parallel structure,Energy recovery control circuit