Abstract
A recent investigation explored a new measuring concept used in partial discharges (PD) measurements in gas insulated substations (GIS), consisting of a magnetic loop antenna. The sensor’s frequency response was characterized up to some tens of MHz. This paper proposes an improved version of the sensor with an extended bandwidth (BW) one order of magnitude higher: a resonance, attributed to a common mode current in the mounting hole, is identified and eliminated employing ferrite beads in the feeder cables. Moreover, this publication proposes an electric circuit model that fully covers the transverse electromagnetic mode (TEM) frequency range in GIS. The electric model is compared against experimental measurements using a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</i> GHz bandwidth testbench, giving accurate results. Two contributions are achieved in this research: an improved magnetic loop antenna with extended bandwidth and an accurate electric circuit model. This publication paves the way for further research on time resolution and signal postprocessing techniques for magnetic loop antennas in GIS.
Highlights
G AS insulated substations (GIS) exhibit advantages over traditional air insulated substations, such as long life span, high reliability, and reduced space
A partial discharges (PD) sensor that measures in the transverse electromagnetic mode (TEM) frequency ranges is, in principle, able to calculate the charge of PD
Partial discharges are electrically represented as current pulses; the PD charge magnitude is related to the current [5]
Summary
G AS insulated substations (GIS) exhibit advantages over traditional air insulated substations, such as long life span, high reliability, and reduced space. Date of publication June 14, 2021; date of current version August 31, 2021. Studies presented in [3] and [4] conclude that it is not possible to estimate the PD charge using the ultra-high frequency (UHF) range because of the complex propagation in the TE a TM mode. A PD sensor that measures in the TEM frequency ranges is, in principle, able to calculate the charge of PD. This calibration setup is used for the experimental characterization of the magnetic loop antenna and has been instrumental in identifying the antenna’s resonances. The increased BW improves the charge estimation and the time resolution by decreasing reflected pulses overlapping [2]
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