Investigating the Internal Winding Resonance Characteristics of Various Power Transformer Winding Designs

The transformer is the main equipment in the electricity network, which plays an essential role because the failure of the transformer can cause severe power outages. One of the failures of the transformer is breakdown insulation caused by over-voltage. Failure of the transformer due to over-voltage even still occurs on transformers that are in good condition and also protected by arresters. In this condition, one of the factors suspected as the cause of failure is the phenomenon of resonance over-voltage. Several studies have been conducted to investigate the phenomenon of resonance in the transformer, both the phenomenon of ferro resonance and internal winding resonance. Research conducted is generally related to methods to reduce impacts, both by installing protective equipment and choosing the right design. In this research, the small scale power transformers were designed with different type windings of each phase. Phase A use continuous disc type winding, phase B use shield disc type winding and phase C use closing disc type winding. Measurement points of the tapping locations were located at 25%, 50%, 75% and 100% of the full winding. Based on the results of the high frequency characteristics using Sweep Frequency Response Analysis (SFRA), all of the three winding design used in this research shows that there are a tendency of internal winding resonance to occur. Based on that SFRA characteristics, it was found that the highly potential occurrence for internal winding resonance that needs to be considered is the resonance that occur at the frequencies above 100 kHz. According to the SFRA characteristic, frequency above 200 kHz is strongly influenced by series winding capacitance. Hence, based on these results, series capacitance of winding strongly influence the phenomenon of internal winding resonance.