The Study Of Moisture Location For Oil Impregnated Paper Insulation Bushing

Moisture adversely affects the dielectric properties of oil-impregnated paper(OIP)insulation bushing.It reduces the dielectric strength as well as breakdown strength and causes the degradation of the insulation material leading to the bushing failure which in turn results to transformer and power system failure.Most of bushing failures are caused by moisture ingress within high voltage power transformer insulation bushing.Currently,frequency domain spectroscopy(FDS)measurement method based on dielectric response is used to identify the condition of the insulation.It determines the moisture in insulation bushing and provides the global change in insulation properties.in this research a 15kV OIP bushing model consisting of three layers of foils is introduced to study the influence of moisture on OIP insulation bushing and its location in the laboratory condition using FDS method.The research results show that the moisture in the OIP insulation bushing presents both high capacitance(C)and dissipation factor(DF)in the insulation.Regarding,the influence of moisture location in the OIP insulation bushing,the research findings show that the moisture is highly concentrated in innermost and middle layers and that the FDS is more sensitive to detecting and locating the moisture in thinner than thicker insulation bushing and the part of which the OIP bushing is highly concentrated in moisture.The research results also show that the moisture within the OIP insulation bushing have a significant impact on insulation parameters such as C,DF,insulation resistance IR and real part of relative permittivity ?'.However.DF is most excellent parameter for predicting the moisture in the OIP insulation bushing.Lastly,an increase in moisture showed a significant increase in maximum DF(at low frequency)whereas minimum DF(at high frequency)increased gradually and can serve as a diagnostic parameter for evaluating the moisture in insulation bushing.