Krzysztof Siodła

Investigation of transformer model winding deformation using sweep frequency response analysis

This article describes an investigation of the transformer inner winding deformation, using Sweep Frequency Response Analysis (SFRA). The object of the investigation is a transformer model with functionality of disassembling inner winding and changing configuration of its parts. The purpose of the investigation is to find the characteristic frequency ranges which could be treated as diagnostic bands.

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.

Diagnosis of degradation effects of on-load tap changer in power transformers

By performing diagnostics on on-load tap changers by means of dynamic resistance measurements a condition diagnosis of high-speed resistor-type tap changers can result in pre-failure detection of contact degradation. It provides the measurement parameters that are most suitable for detecting these defects, such as the presence of a contact film, contact wear and pitting. The resistance curves of OLTCs are interpreted, to determine the occurring degradation mechanisms, which can be used to support strategic decisions about the maintenance or overhaul of the tap changer.

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.

Partial discharge localization on dry-type transformers

In this paper an electrical partial discharge (PD) localization technique for a dry type power transformer is presented. The method has been tested in the laboratory on real transformer coil as well as on a transformer in a test bay. Calibration signal is injected through a plate sensor placed along the winding on the surface of the transformer coil in different positions, thus PD signals can be measured at both coil terminal sites using digitizer. Measured PD signal during test can be then evaluate and compared with calculated transfer function. The described technique enables not only localization of the PD source also determination of the apparent charge. This evaluation can be more accurate than conventional PD measurements by use of quadruple and coupling capacitor calibration and can be used during manufacturing process as well as diagnostic in field.

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

Dependence of creeping partial discharge activity in a synthetic esters-paper insulating system on the temperature

The paper presents the results of partial discharges investigation in a synthetic ester-paper insulating system for three values of temperature (25°C, 30°C and 40°C). The article shows the measurement set-up, measuring procedure, data outcome and its analysis. It occurs, that there is a positive correlation between temperature and PDs activity in investigated set-up.

On-site testing and diagnosis of distribution and transmission power cables using damped AC voltages

On-site testing and diagnosis of distribution and transmission power cables is one of the issues of asset management within power utilities. Due to the importance of power cables in the transmission network it is of importance to test the initial condition during after-laying, to test the actual condition of HV power cables during operation and to test the repair work after a failure.