Wojciech Sikorski

Location of partial discharge sources in power transformers based on advanced auscultatory technique

In the paper a new partial discharge (PD) location technique based on acoustic emission and conventional partial discharge detection method is presented. Synergetic combination of two methods allows obtaining a high accuracy of the insulation fault location and reducing the time of measurement procedure. Several cases of practical application of the new technique for PD location in the power transformers tested in an HV laboratory and in a substation are discussed.

Detection, Recognition and Location of Partial Discharge Sources Using Acoustic Emission Method

The acoustic emission (AE) is a group of phenomena involving generation of transient elastic (acoustic or vibro-acoustic) waves, resulting from liberation of intermolecular bond energy (deformation, cracking, phase transitions). This fact contributed to elaboration of the acoustic emission method, which is widely used in: (i) diagnostics of cutting tools and machine cutting process, (ii) machinery and civil structures condition assessment, (iii) fatigue and fracture materials research, (iv) detection of material defects, (v) orogenic and earthquake prediction research, (vi) rockbursts prediction in deep mines and (vii) in chemical reactions and phase transitions research. This method is also applied in electrical power engineering for detection and location of partial discharge (PD) sources in insulation system of large power transformers and GIS/GIL (Gas Insulated Substations/Gas Insulated transmission Lines).

Location of partial discharges sources using sensor arrays

Occurrence of partial discharges (PD) is one of the basic criteria of high voltage devices insulation evaluation. Precise PD source location is crucial for undertaking maintenance of mentioned equipment. This paper concerns the issue of partial discharges sources location using phased rectangular arrays technique and high-resolution direction of arrival estimation technology. In addition to the theoretical assumptions of both techniques, the simulation result, in which an Uniform Rectangular Array (URA) was used for registration of the electromagnetic signals generated by defects in power transformer insulation system, were shown. To estimate the Direction of Arrival (DOA) of electromagnetic signals, that propagate from the discharge-generating defect to the transducer array installed on transformer tank, Minimum Variance Distortionless Response (MVDR) algorithm was chosen. The location of defect was determined using two intersecting lines defined by the DOAs from two URAs. With the ability to locate multisource discharges (even at very low signal to noise ratio - SNR), the adopted solution has advantages over conventional techniques.

Power Transformer Diagnostics Based on Acoustic Emission Method

Widely applied techniques for the fault location based on AE method are: (i) measurement of the time difference of arrival (TDOA) of the acoustic signals, (ii) measurement of the acoustic signal amplitude in different areas of a transformer tank (standard auscultatory technique, SAT), (iii) advanced auscultatory technique (AAT), (iv) estimation of the direction of arrival (DOA) of the acoustic signal based on the phased-array signal processing (Markalous et al., 2008; Tenbohlen et al., 2010; Qing et al., 2010).

Ocena możliwości zastosowania matrycy anten UHF do lokalizacji wyładowań niezupełnych

This paper raises the issue of partial discharge sources localization. Through the use of UHF antennas array combined with beamforming algorithms it is possible to estimate the direction of arrival of the signal. The results of studies, in which the signal was registered using linear array of monopole antennas, were presented. Artificially generated signal had a frequency similar to the actual frequency of the signals emitted by different types of partial discharge. (Possibility evaluation of UHF antennas array application to the localisation of partial discharges). Słowa kluczowe: wyładowania niezupełne, antena UHF, matryca sensorowa, estymacja kierunku nadejścia sygnału

Ultraczułe przetworniki emisji akustycznej zoptymalizowane do monitoringu wyładowań niezupełnych w transformatorach

The paper presents prototype acoustic emission transducers, which were optimized for detection and monitoring of partial discharges (PDs) in power transformers. Their high sensitivity was proven in PD model research, in which popular commercial transducers were used for comparison. Moreover, the issue of characteristic frequencies of acoustic emission signals generated by high energy forms of partial discharges (creeping, turn-to-turn, surface, in oil-duct) was discussed in the paper. (Ultra-sensitive acoustic emission transducers for partial discharge monitoring in power transformers). Słowa kluczowe: wyładowania niezupełne, przetwornik piezoelektryczny, emisja akustyczna, monitoring transformatora energetycznego.