Abstract
The detection of partial discharges (PD) can help in early-warning detection systems to protect critical assets in power systems. The radio-frequency emission of these events can be measured with antennas even when the equipment is in service which reduces dramatically the maintenance costs and favours the implementation of condition-based monitoring systems. The drawback of these type of measurements is the difficulty of having a reference signal to study the events in a classical phase-resolved partial discharge pattern (PRPD). Therefore, in open-air substations and overhead lines where interferences from radio and TV broadcasting and mobile communications are important sources of noise and other pulsed interferences from rectifiers or inverters can be present, it is difficult to identify whether there is partial discharges activity or not. This paper proposes a robust method to separate the events captured with the antennas, identify which of them are partial discharges and localize the piece of equipment that is having problems. The separation is done with power ratio (PR) maps based on the spectral characteristics of the signal and the identification of the type of event is done localizing the source with an array of four antennas. Several classical methods to calculate the time differences of arrival (TDOA) of the emission to the antennas have been tested, and the localization is done using particle swarm optimization (PSO) to minimize a distance function.
Highlights
The correct maintenance of high voltage equipment is an advantageous strategy for electric utilities to avoid unexpected outages [1,2]
Partial discharge sources can be identified through the well-known partial discharges (PD) phase resolved (PRPD) patterns, which represent PD magnitudes referenced to the applied high voltage
These parameters are characterized by the frequency intervals where the spectral power is calculated, so they will be referred as power ratio for low frequencies (PRL) and power ratio for high frequencies (PRH), and they are defined as follows: Pf2L
Summary
The correct maintenance of high voltage equipment is an advantageous strategy for electric utilities to avoid unexpected outages [1,2]. Partial discharge sources can be identified through the well-known PD phase resolved (PRPD) patterns, which represent PD magnitudes referenced to the applied high voltage. This is achieved through voltage dividers and high frequency current transformers (HFCT) [5,7,8]. Emissions from PD are being measured using ultrasonic sensors [9,10] and antennas [11,12], respectively These techniques allow making PD location using arrays of sensors simultaneously, which is especially useful inside oil-insulated power transformers and gas-insulated substations and in air-insulated substations [13]. The objective function is minimized using the particle swarm optimization (PSO) algorithm giving excellent results in the geometric location
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