TEV Signal Analysis in Power Transformers: Effects of PD Location and Resonance Modes

Abstract

Detection of partial discharge (PD) in power transformers is crucial since it indicates early-stage insulation degradation that may lead to system failure. The transient earth voltage (TEV) sensor offers a non-intrusive method for measuring PD during online transformer operation. In this paper, the application of the TEV measurement technique is investigated through both laboratory experiments and numerical simulations. A TEV sensor model is developed in COMSOL Multiphysics to determine the time-domain signal sensitivity for different PD source locations and TEV sensor positions, and the simulation results are compared with experimental measurements obtained using the UHF 800 and MPD 600 systems. In addition, the resonance frequencies of the transformer tank are evaluated analytically, numerically, and experimentally. The paper demonstrates that the center frequency and bandwidth in the UHF 800 must be carefully selected based on the transformer’s resonance frequencies. Phase-resolved partial discharge (PRPD) patterns for two PD sources at 200 MHz $\pm ~40$ MHz (resonate zone) and 250 MHz $\pm ~40$ MHz (non-resonate zone) show that choosing suitable filter settings for TEV measurements is essential for correctly interpreting PD activity and separating it from background noise.