On the Use of Monopole Antennas for Determining the Effect of the Enclosure of a Power Transformer Tank in Partial Discharges Electromagnetic Propagation

Abstract

A well-defined condition-monitoring for power transformers is key to implementing a correct condition-based maintenance (CBM). In this regard, partial discharges (PD) measurement and its analysis allows to carry out on-line maintenance following the standards IEC-60270 and IEC-60076. However, new PD measurements techniques, such as acoustics or electromagnetic (EM) acquisitions using ultra-high-frequency (UHF) sensors are being taken into account, IEC-62478. PD measurements with antennas and the effect of their EM propagation in power transformer tanks is an open research topic that is considered in this paper. In this sense, an empty tank model is studied as a rectangular cavity and their resonances are calculated and compared with their measurement with a network analyser. Besides, two low cost improved monopole antennas deployed inside and outside of the tank model capture background noise and PD pulses in three different test objects (Nomex, twisted pair and insulator). The average spectrum of them are compared and can be found that mainly, the antenna frequency response, the frequency content distribution depending on the PD source and the enclosure resonances modes are the main factors to be considered in PD acquisitions with these sensors. Finally, with this set-up, it is possible to measure PD activity inside the tank from outside.

Electromagnetic Burst Measurement System Based on Low Cost UHF Dipole Antenna

“…On one hand, while the smaller the antenna, the less its sensitivity for low frequencies. On the other hand, while the larger the probe, the greater the perturbation introduced by the antenna to the field, making the measurements less reliable and the response slower [15]. Finally, the resonant frequency (RF) of the antenna was selected to be far from the high intensity fields radiated by the measured phenomenon.…”

“…Depending on the working gas, this column can produce pulses of neutrons, ions and electrons, as well as visible to X-ray pulsed radiation. Unfortunately, during the plasma generation process, electrical disruption processes are created which originate very large amplitude EMN sources whose spectral and temporal behavior is very similar to that generated by other types of physical and electrical phenomena (Z-pinches [11,12], wire arrays [13], capillary discharges [14], partial discharges [15], etc.). These transient electromagnetic emissions can easily couple to cables, conductors and electronic systems of the surrounding equipment [16,17], causing permanent damage and catastrophic failure of these equipment [18,19].…”

Antipodal Vivaldi Antenna to Detect UHF Signals That Leaked Out of the Joint of a Transformer

“…It can be divided into two types, namely, builtin and external, according to the difference in antenna installation position. Typical built-in antennas include monopole [7], Hilbert [8], and Goubau antennas [9]. They are usually installed in the hand hole, manhole, and oil drain valve.…”

Positioning and Imaging Detection of Corona Discharge in Air with Double Helix Acoustic Sensors Array

“…The UHF method has been proven to be an effective tool in detecting PD occurring inside power equipment, especially in gas-insulated substations (GIS) [1,2] and power transformers [3,4]. However, UHF detection is strongly influenced by the EM noise distributed in the very high frequency (VHF) range (30-300 MHz), which is overlapped by the EM waves of corona in air [5,6].…”