Assessment of Rogowski Coils for Measurement of Full Discharges in Power Transformers

Abstract

Science and industry have sought to develop systems aiming to avoid total failures in power transformers since these machines can be working under overloads, moisture, mechanical and thermal stresses, among others. These non-conformities can promote the degradation of the insulation system and lead the transformer to total failure. In the incipient stages of these faults, it is common to detect Full Discharges (FDs), which are short circuits between degraded coils. Therefore, several techniques were developed to perform FD diagnosis using UHF, acoustics, and current sensors. In this scenario, this article presents a mathematical model for Rogowski coils and compares two different types of cores: Ferrite and Teflon. For this purpose, FDs were induced in an oil-filled transformer. The sensitivity and frequency response of the Rogowski coils were compared. This analysis was achieved using the Power Spectrum Density (PSD) and the energy of the acquired signals. Additionally, the Short-Time Fourier Transform (STFT) was applied to detect repetitive discharges. The results indicated that the Ferrite core increases the sensitivity by 50 times in the frequency band between 0 and 1 MHz. However, the Teflon core showed higher sensitivity between 5 and 10 MHz.

Design and applications of Rogowski coil sensors for power system measurements: A review

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PCB Rogowski Coils for Capacitors Current Measurement in System Stability Enhancement

“…At the end of the twentieth century, the development of PCB technology provided new ideas for the development of traditional Rogowski coils [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], with its digital wiring…”

Measurement of Power Frequency Current including Low- and High-Order Harmonics Using a Rogowski Coil

“…In fact, researchers and scientists have proposed its use in many applications. Among these applications are the measurement of power frequency current [4][5][6][7][8][9][10], measurement of impulse and pulsed currents [10][11][12][13], fault detection in DC-DC converters [14][15][16][17][18][19], condition monitoring of high-voltage insulators [20,21] and power system equipment [22], smart meters [23], and many other applications. It is used to measure the power frequency current for singlecore and multi-core cables and to measure impulse currents with different characteristics.…”