特高压变压器典型分区绝缘结构线圈内匝间电压振荡特性

Characteristics of Inter-turn Voltage Oscillation in Typical Graded Insulation Windings of Ultra-high Voltage Transformers

为应对快速暂态电压侵入变压器线圈后可能激起的电压振荡,以内屏连续式和纠结连续式2种典型结构的高压线圈为对象,研究了变压器线圈固有频率的响应因子、固有频率的振荡模式、固有频率正弦电压和典型快速暂态过电压(VFTO)激励下线圈内匝间电压的分布规律。结果表明:变压器线圈内激起明显电压振荡的频率一般<10 MHz,内屏连续式线圈最大响应因子略大于纠结连续式线圈,且较大响应因子的频率分布要更分散;在固有频率正弦电压激励下,低频振荡模式表现出对较大范围的节点电压有明显贡献,而高频振荡模式表现出只对线圈首端少数节点电压有明显贡献,高频振荡模式比低频振荡模式在线圈首端部位有更大的电压梯度,从而可能产生更大的匝间电压。综合比较2种线圈的振荡模式发现,从总体来看,纠结连续式出现最大匝间电压略小于内屏连续式,前者出现较大匝间电压的范围略小于后者。

To deal with the voltage oscillation caused by invading fast transient voltage in transformer windings, taking the interleaved-continuous coil and intershielded-continuous coil as objects, we investigated the response factors and the oscillation modes of natural frequencies, as well as the inter-turn voltage distribution under the excitation of sinusoidal voltage and a typical very fast transient overvoltage. The results show that the resonant frequencies with which can excite obvious voltage oscillations in the windings are generally below 10 MHz. The maximal response factor of the intershielded-continuous coil is slightly larger than that of the interleaved-continuous coil, and the resonant frequencies with large response factors distribute more dispersively in the intershielded-continuous coil. Under the excitation of sinusoidal voltages with resonant frequencies, the voltage components in low-frequency oscillation modes contribute to the node voltages in a wider spatial range, however, those in high-frequency oscillation modes contribute only to the node voltages at the first several disks near the applied voltage and can cause more significant inter-turn voltages. Comparison of the maximal inter-turn voltages and their spatial distributions in both windings between the sinusoidal and very fast transient voltage excitations indicates that the maximal inter-turn voltages produced in the interleaved-continuous winding are slightly lower than those of the intershielded-continuous winding, and are more concentrated at the first few disks.