A Protection Scheme for Improved Transformer Bushing

The paper suggests a new bushing scheme which is suitable for bushing monitoring. Compared to the traditional bushings, the new scheme has a measurement tap on it. Then a capacitor and a small current transformer are introduced in series connecting with the measurement tap of the bushing. Then the voltage across the capacitor and the current through the measurement tap are supervised and their change rate are monitored. In this way, any great change of the bushing capacitance can be found immediately, and the protective relay sends the alarm or trip signal to isolate the transformer, so that the bushing security is enhanced.