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Charge dynamics of partial discharges explored applying a chopped sequence

Florkowski Marek

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 5

art. no. e138817

EN

Diagnostic methodologies are of fundamental importance for operational strategies of electrical devices, both in the power grid and in industrial applications. This paper reports about a novel approach based on partial discharge analysis applied to high voltage electrical insulation. Especially dynamics of charges deposited by partial discharges is explored applying a chopped sequence. The applications refer to microvoids occurring inside solid insulating systems or at the interfaces, such as delaminations at the electrodes. The experiments were carried out on embedded voids having distinctive wall dielectric materials. The underlying physical phenomena of post discharge charge transport are analyzed. The assessment is performed using phase-resolved partial discharge patterns acquired applying a chopped sequence. The chopped partial discharge (CPD) method provides quantitative insight into post discharge charge decay processes due to deposited and accumulated charges fluctuations. The assessment indicator is based on comparing partial discharge inception angle between chopped sequence and continuous run. The experiments have shown that materials with distinctive surface conductivity revealed adequately different charge decay time dynamics. The detailed analysis yields time constant of walls charge decay for insulating paper equal to 12 ms and cross-linked polyethylene 407 ms. The CPD method may be further used to investigate streamer physics inside bounded cavities in the form of voids. The presented method provides a quantitative approach for charge non-invasive decay assessment and offers high potential in future diagnostics applications.

2

Thermographic analysis of losses to the surroundings from the WR-25 stoker boiler

Krawczyk P., Kapuściński J.

Rynek Energii

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2017

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Nr 4

97--103

EN

In this article, the method for calculating the heat loss from the surface of the walls of the power boiler by measuring the temperature distribution on the walls of the boiler with a thermal imaging camera is presented. Measurements were done on two WR25 stoker boilers, with a capacity of 29,1 MW each, working in a heating plant supplying district heating for a town with more than 150 thousand inhabitants. Heat loss from the surface of the boiler walls was calculated, the comparison of heat loss from classic WR25 boiler with loss from water walls-based WR25 boiler was done, a graph of temperature increase along the height of the wall of water walls-based WR25 boiler was made. The analysis and presentation of areas of the highest heat loss (gaps in insulation, uninsulated components on boiler wall) was done.

PL

W artykule zaprezentowano metodę szacowania straty ciepła do otoczenia z powierzchni bocznych analizowanego kotła, poprzez pomiar rozkładu temperatury tych ścian z wykorzystaniem kamery termowizyjnej. Pomiary zrealizowano dla dwóch kotłów rusztowych typu WR 25 o mocy nominalnej 29,1 MW każdy. Kotły zabudowane są w ciepłowni miejskiej zaopatrującej w ciepło ok 150 tys. mieszkańców. Jeden z badanych kotłów był kotłem wykonanym w technologii tradycyjnej drugi w technologii ścian szczelnych. W ramach zrealizowanych prac straty ciepła do otoczenia dla obydwu kotłów zostały oszacowane a wyniki tego oszacowania zestawione. Dodatkowo zidentyfikowano oraz porównano dla obydwu kotłów miejsca występowania lokalnych, podwyższonych strat ciepła.

3

Szacowanie czasu propagacji fal dźwiękowych w ośrodkach materialnych za pomocą metody Dijkstry

Perkowski Z., Gozarska K.

Roczniki Inżynierii Budowlanej

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2012

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z. 12

43--48

EN

A proposition of method enabling an estimation of wave propagation time from point to point (but without refection) in material media is presented in the work. The calculating procedure is based on Fermat’s principle and Dijkstra’s algorithm and it is relatively quick and easy for its implementation by means of individual computer code. It can be used effectively in optimization methods oriented on reconstruction of damage state in engineering structures basing on time-of-flight measurements for mechanical waves.