变压器油纸绝缘套管受潮缺陷频域介电谱特征

已有研究表明,频域介电谱(FDS)对油纸绝缘受潮缺陷的检测比较灵敏。为了研究变压器油纸绝缘套管受潮缺陷的FDS特征,测试了受潮后套管模型不同静置时间下的介损电压特性和0.001 Hz～1 k Hz的介损频率特性。结果表明:在受潮初期,相同试验电压下介损随时间的变化呈现微弱增长趋势,但并不明显,相同时间下,介损随试验电压升高有所增长;在受潮中期,介损随时间的变化呈现明显增长趋势,并在120 h时介损达到峰值;在受潮末期,介损随着时间的增加呈现下降趋势,整个过程介损增量未超过规程规定值,可考虑降低规程规定值。在FDS的低频段0.001～0.01 Hz区间范围内可明显区分受潮套管和不受潮套管,1 m Hz介损特征尤其明显。因此建议套管出厂及运行增加FDS低频段测试,利用FDS低频段特征进行套管绝缘诊断。

FDS characteristic of damp-affected oil-paper insulation transformer bushings

It has been shown that frequency domain dielectric spectroscopy is sensitive to detect moisture defects of oil-paper insulation, in order to study the frequency domain dielectric spectrum characteristics of damp-affected defect of transformer oil paper insula-tion bushings, the dielectric loss voltage characteristics and the dielectric loss frequency characteristics of 0.001hz ~1kHz were studied .The results show that the dielectric loss increases slightly with time under the same test voltage at the beginning of damp, but it is not obvious.At the same time, the dielectric loss increased with the test voltage.In the middle period of damp, the dielec-tric loss showed an obvious increasing trend with time, and reached its peak at 120h.At the end of wetting, the dielectric loss de-creased with the increase of time.The increase of dielectric loss in the whole process does not exceed the regulation value, the regulation value can be reduced.In the low frequency band 0.001hz ~ 0.01hz of frequency domain dielectric spectrum, the damp-affected bushing and the non-damp-affected bushing can be distinguished obviously, and the dielectric loss characteristic of 1mHz is particularly obvious.Therefore, it is recommended to add FDS low-frequency test to the casing and make use of FDS low-frequency characteristics for casing insulation diagnosis.