Excitation and Vibration Characteristics of Single-Phase Four-Column Transformer Under DC Bias

With the construction of long-distance and large-capacity UHV DC projects, the impact of DC bias on the operation of transformers has become more and more serious. It causes excitation current distortion, increased harmonics, increased loss, increased vibration, local overheating, etc., which seriously threatens the safe operation of the transformer. In this paper, based on a 110kV single-phase four-column transformer, a test platform is built, and the no-load excitation and vibration characteristics of different DC currents are measured and analyzed. The results show that with the increase of DC current, the peak value of excitation current basically shows a linear increase, and the content of odd harmonics 1~7 and even harmonics 2~8 are large. When
$\mathbf{I}_{\mathbf{dc}}\leqslant \mathbf{16}\mathbf{A}$
, the vibration acceleration of each measuring point increases linearly, the amplitude of the #1 measuring point is the largest. When
$\mathbf{I}_{\mathbf{dc}} > \mathbf{16}\mathbf{A}$
, the vibration acceleration tends to be saturated, and the acceleration of #1 measuring point increased from 70m/s
²
to 8Sm/s2, while that of #2 to #6 does not exceed 12m/s
²
. The overall variation law of the vibration velocity is basically consistent with the vibration acceleration, and the vibration velocity of #1 measuring point is the largest. With the injection of DC current, the peak-to-peak value of the vibration displacement of each measuring point first linearly increases and then saturates. When
$\mathbf{I}_{\mathbf{dc}} > \mathbf{10}\mathbf{A}$
, the peak-to-peak value of the vibration displacement of the #1 measuring point fluctuates around
$\mathbf{40}\boldsymbol{\mu}\mathbf{m}$
, and the maximum does not exceed 50um, while that of #2 to #6 does not exceed
$\mathbf{5}\boldsymbol{\mu}\mathbf{m}$
.