Abstract
During the last two decades, on-line partial discharge (PD) measurements have been proven as a very efficient test to evaluate the insulation condition of high-voltage (HV) installations in service. Among the different PD-measuring techniques, the non-conventional electromagnetic methods are the most used due to their effectiveness and versatility. However, there are two main difficulties to overcome in on-line PD measurements when these methods are applied: the ambient electric noise and the simultaneous presence of various types of PD or pulse-shaped signals in the HV facility to be evaluated. A practical and effective method is presented to separate and identify PD sources acting simultaneously in HV systems under test. This method enables testers to carry out a first accurate diagnosis of the installation while performing the measurements in situ with non-invasive high-frequency current transformers (HFCT) used as sensors. The data acquisition in real-time reduces the time of postprocessing by an expert. This method was implemented in a Matlab application named PRPD-time tool, which consists of the analysis of the Phase-Resolved Partial Discharge (PRPD) pattern in combination with two types of interactive graphic representations. These graphical depictions are obtained including a feature parameter, effective time (teff), related to the duration of single measured pulses as a third axis incorporated in a classical PRPD representation, named the PRPD-teff pattern. The resulting interactive diagrams are complementary and allow the pulse source separation of pulses and clustering. The effectiveness of the proposed method and the developed Matlab application for separating PD sources is demonstrated with a practical laboratory experiment where various PD sources and pulse-type noise interferences were simultaneously measured.
Highlights
Developments in signal processing techniques achieved in recent years have positioned on-line partial discharges (PD) tests measuring with high-frequency current transformer (HFCT) sensors as an effective method for evaluation of the insulation condition of high-voltage (HV) electrical equipment such as power transformers [1]
It the is inattenuation that position where the installation of anand sensor recommended, to avoid the effect of and distortion of the pulses is recommended, order to avoid the effect of theThus, attenuation andtodistortion the toHFCT
A novel and effective method for impulsive sources separation was proposed, which considers the effective time as a feature parameter along with the pulses’ amplitudes and the phase in which they are acting
Summary
Developments in signal processing techniques achieved in recent years have positioned on-line partial discharges (PD) tests measuring with high-frequency current transformer (HFCT) sensors as an effective method for evaluation of the insulation condition of high-voltage (HV) electrical equipment such as power transformers [1]. A practical and efficient computational tool named the phase-resolved partial discharge (PRPD)-time tool was developed in order to assist in the insulation diagnosis procedure. The PRPD-time tool is a PD analysis tool that makes possible the supervised source-pulse separation process using a powerful and interactive graphical interface. A source pulse separation and identification process allows the determination of the specific PD or noise sources present simultaneously in HV installations and is commonly implemented in three stages [3]: Filtering and signal denoising
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