A Study on the Enhanced Extraction of Ultra-High-Frequency Signals Induced by Transformer Core Coupling

Partial discharge, as an important indicator of insulation degradation in transformers, is a crucial means of assessing the insulation performance of transformers. The existing broadband pulse current detection is easy to install and has no electrical connection with the detection equipment, but it is susceptible to electromagnetic interference from the external environment. Although ultra-high-frequency detection has good anti-interference performance, the installation of its sensors needs to match the structure of the transformer and cannot be applied to partial discharge detection of transformers in operation. This article proposes a research method for detecting ultra-high-frequency partial discharge based on the induction signal of transformer iron core. A transformer iron core simulation model is established based on the time-domain finite-difference method, and the reliable detection frequency band of the iron core for ultra-high-frequency signals of partial discharge is simulated. At the same time, the optimal extraction method of the induction signal is also simulated and studied. The feasibility and effectiveness of the detection method are verified through partial discharge experiments on a physical 110 kV transformer. The results indicate that the transformer core can be used as an ultra-high-frequency sensor for partial discharge detection in the ultra-high-frequency domain. The ultra-high-frequency partial discharge detection method based on a transformer core induction signal is consistent with conventional pulse current and ultra-high-frequency detection.