Mritunjay Kumar and Mandava Mohana Rao
Adapter sensor, bushing, bushing tap, capacitance, condition monitoring, leakage current and tan delta
High-voltage (HV) bushing is a device used to carry HV and high current from electrical equipment such as transformers and switchgear to overhead transmission lines. In service, HV bushing has to withstand the rated HV, abnormal system overvoltages as well as the heat generated by the high current. With the introduction of ultra–high-voltage class power transmission equipment in recent times, the reliability of the bushing becomes important, as an unplanned outage of the system may cause heavy revenue loss. Therefore, the bushing insulation requires continuous monitoring for its healthiness. This can be generally achieved by analysing its leakage current which is measured using a suitable tap design at low-voltage (LV) side of the bushing. The paper presents the simulation of bushing layer faults and their influence on the leakage current, for both three-phase and single-phase configurations. This study is also aimed to provide a correlation and trend between the bushing layer faults and the phase/magnitude of the leakage current so that the state of the healthiness of the bushing can be determined. Furthermore, the paper also describes about the development of a novel adapter sensor with suitable hardware and software for the online monitoring of bushing leakage current. Finally, implementation of condition monitoring technique on a bushing experimental model is also presented.
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