hi this sounds like loose metal leaves this will give rise to high third and fifth harmonics frequencies  this couls cause all sorts of problems normaly  but could be helpful if it is the power supply to your cell.
aussepom

At least here is the complete abstract:

Analysis of Resonance in Transformer Windings Under Very Fast Transient Overvoltages
SUN Haifeng, LIANG Guishu, ZHANG Xile, CUI Xiang （1. School of Electrical Engineering, North China Electric Power University, Baoding 071003, China; 2. Baoding TianWei Baobian Electric Co., LTD, Baoding 071000, China）
Abstract:

Very Fast Transient Overvoltages （VFTOs） generated by switching operations of disconnectors or circuit breakers in Gas Insulated Substation （GIS） are dangerous for the transformer insulation, especially for the directly connected ones. One problem is that VFTO always has a short rise time, which can cause the unbalance of voltage distribution in transformer windings. Under some special circumstances, the turn-to-turn voltage can be close to the transformer basic insulation level. Another problem is the resonance in transformer winding which occurs when the frequency of the incoming VFTO matches some of the resonance frequencies of the transformer. The resonant overvoltage can destroy the insulation between turns. Because of the complexity of the physical phenomena in the transformer, the progress in transformer modeling for the analysis of resonance in transformer windings is not satisfactory. Multi-conductor transmission line model based on the representation of the winding by its individual turns is used to analyze the resonant phenomena. This paper proposes a single input and multiple output circuit model and computation method of the transfer function of transformer. Transfer function from the terminal of arbitrary turn to the input is deduced, which is presented to analyze the resonant frequencies of transformer. After the analysis, the locations where the resonance could happen are determined. The above method is applied to a core-type transformer model. After this analysis and calculation. It can be seen that amplitude of high frequency component is decreased with increment of turn number. There is a good agreement between the measured and calculated terminal amplitude frequency response characteristics. Considering the complexity circumstance around the transformer model, the results are good enough to analyze the resonant phenomena in transformers. It is found that the model proposed by this paper is adequate for the calculation of resonance in transformer windings under VFTO and the results can satisfy the engineering calculation.[著者文摘]
Key words:

VFTO; transformer; multi-conductor transmission line; resonant frequency; transfer function