Study on Estimation Method for Lifetime of Converter Transformer Insulation Paper Based on FDS

To realize nondestructive tests for mechanical strength of converter transformer insulation paper and residual lifetime evaluation of transformer insulation, firstly, a series of accelerated mechanical-thermal aging(MTA) experiments were performed in this work under the conditions of 100℃, the amplitude of 0.57 mm, the frequency of 50 Hz and the aging duration of 35 d. Secondly, the frequency domain spectroscopy(FDS) characteristics and tensile strength(TS) of cellulose insulation paper specimen were measured and determined when the frequency scope of the FDS tests ranged from 1 mHz to 1 kHz. By analyzing the characteristics of tanδ-f curves, it was found that the low frequency band of tanδ-f curve could be selected as the characteristic frequency band to indicate the degradation status of the specimen. Moreover, the negative exponential relationship between the dielectric loss value and the corresponding tensile strength of the specimen with different degradation status under the characteristic frequency was explored, and the validity of this proposed relationship was verified by the experimental data. Based on the above relationship, the nondestructive testing of mechanical strength and the effective evaluation of degradation status of insulation paper could be achieved. Finally, the residual lifetime prediction criterion based on FDS was developed, by which the insulation lifetime of the specimen could be evaluated effectively. The conclusion can provide a theoretical basis for nondestructive tests and lifetime evaluation of the mechanical properties of the insulation paper within power transformers. © 2020, High Voltage Engineering Editorial Department of CEPRI. All right reserved.