812 / 2022-04-01 00:08:49

Test of excitation and vibration characteristics under DC bias of single-phase four-column transformer

DC bias,vibration,transformer

Purpose/Aim

DC bias leads to DC component in the transformer winding, saturating the core half cycle, increasing magnetic leakage, current distortion and increasing loss, causing overheating of structural parts and oil tank, exceeding the audible noise, damaging the insulation structure and threatening the safety of equipment. In this paper, the DC bias test platform of 110kV single-phase four column transformer is built, the excitation characteristics under different bias currents are tested, and the influence law of DC bias on oil tank vibration is obtained, which lays a foundation for further analysis of the influence of DC bias.

Experimental/Modeling methods

The test is carried out based on the mutual load method. A program-controlled DC injection device is added between the two transformers. Transformer 1 is the intermediate transformer, and transformer 2 is the tested transformer. Sensors are arranged to excite from the high-voltage side to test the excitation and vibration characteristics of transformer 2.

Results/discussion

With the increase of DC current, the 1st, 3rd and 5th harmonics and 2nd and 4th harmonics increase obviously. Under no-load condition, the acceleration frequency response of each measuring point is mainly concentrated in 400 ~ 2kHz, and mainly in the frequency doubling band range of 50Hz. Moreover, the peak position of the same measuring point under different current conditions is not corresponding, and the vibration displacement peak to peak of different oil tank measuring points shows a saturated trend.

Conclusions

With the increase of DC current, the odd harmonics below 7 times and even harmonics below 6 times increase obviously, and the vibration of different measuring points of the oil tank increases significantly and tends to be saturated. Due to the pressing force of structural parts, the vibration of the oil tank will tend to be saturated after increasing, and there is no sudden and obvious increase of vibration in the transformer.