RF detection of partial discharge in current transformer

The partial discharge test is an efficient technique for detecting early failure of high-voltage apparatuses. Depending on the application, acoustic, optical and electrical methods may be used. For electrical detection, UHF method is widely used for PD measurements. For the noise issue, it is the more sensitive than other methods. However, the UHF antenna often installs at the specific location near the device under test (DUT). It is difficult to detect the PD everywhere with the same sensitivity. Also, the lower frequency PD signal such as high frequency (HF: 0.3-30 MHz) is not easy to measure using the UHF antenna. In this study, we design wide bandwidth coils to detect the radiating frequency (RF) from partial discharge. The copper coils wind uniformly around the whole DUT from the top to the bottom. Using this structure, the localization issue for acoustic and UHF methods may be solved. Also, due to uniform distribution of coils, it can pick up the PD signal effectively. Therefore, the sensitivity can be significantly improved. Compared to the UHF antenna in which all coils wind closely, the coils loose distribute in this study. This greatly increases the bandwidth of the PD detection.