Highly sensitive partial discharge detection by TEV method under severe noise conditions

Partial discharge detection is useful for insulation diagnosis of switchgear. Since a partial discharge can be easily measured by attaching a sensor to a metal casing, we have been studying practical applications of the transient earth voltage (TEV) method. A test model including a switchgear operating under external noise conditions was constructed, and a partial discharge was measured using a TEV sensor. Focusing on the low-frequency band (several megahertz to several tens of megahertz), the fluctuation of the potential on the grounded enclosure was not correlated with the sensor mounting position, allowing the partial discharge to be quantitatively evaluated. Focusing on the high-frequency band (several hundred megahertz), a high signal-to-noise ratio was obtained compared with the low-frequency band. We showed that the TEV method can detect a partial discharge under severe noise conditions.