Dielectric windows for UHF partial discharge detection

Abstract

Increasing the permittivity of the propagation medium inside a hollow tube lowers its cut-off frequency, allowing it to transmit a wider range of signal frequencies. This principle is applied to the design of dielectric windows that can be used to facilitate partial discharge (PD) detection at ultra high frequency (UHF) in a HV metalclad plant such as gas-insulated substation (GIS), power transformers and circuit breakers. External UHF couplers mounted on such windows can be removed or replaced without compromising the integrity of the insulation system. By increasing the signal power level incident on a window-mounted external UHF coupler, higher sensitivity to PD can be achieved. The problem is analyzed using waveguide theory and, using GIS as an example, improvements of andap;6 dB are demonstrated by means of coupler sensitivity measurements and experiments using PD sources

Two planar antennas for detection of partial discharge in gas-insulated switchgear (GIS)

“…The antenna can also be located on an insulated window that is installed in the metallic wall of the enclosure [19]. One advantage of this is that it increases the received power due to the increased surface area where the RF signal can propagate through.…”

“…One advantage of this is that it increases the received power due to the increased surface area where the RF signal can propagate through. However, it limits the PD detection for the existing GIS substations as it needs to be incorporated during the GIS manufacturing process [19].…”

On the Feasibility of Gap Detection of Power Transformer Partial Discharge UHF Signals: Gap Propagation Characteristics of Electromagnetic Waves

“…Therefore, in this section, maintaining H to be 1 cm and the PD source is in positive direction of Z-axis. Depth D of the transformer was adjusted to 18,16,14,12,10,8,6,4, and 2 cm separately, studying the influence of gap depth on the gap propagation characteristics of the PD electromagnetic wave, where the corresponding d…”

“…Currently, UHF antenna sensors are primarily inserted into transformers via handholes [2] and oil drain valves [3] or placed outside by the addition of a dielectric window [4][5][6]. Built-in antenna sensors can effectively shield the sensor from the electromagnetic interference in the surrounding environment, but two problems exist: (1) the built-in antenna sensors will change the internal structure of the transformer, which may damage the uniform distribution of the internal electromagnetic field; (2) for transformers in operation, electric power companies are always unwilling to allow retrofitting.…”

Detection of ultra-wide-band impulsive noise in a 400 kV air insulated electricity substation

“…PD current pulses in strong insulators (e.g. SF 6 ) can have risetimes as short as 50 ps and may contain significant energy at frequencies up to 3 GHz [10]. Several methods and systems for detection of very-highfrequency (VHF, up to 300 MHz) and ultra-high-frequency (UHF, up to 3 GHz) PD in GIS have been investigated [10][11][12].…”