Modelling the ageing of cellulose insulation in power transformers

2005 ◽  
Author(s):  
H.Z. Ding
Keyword(s):  
Power Transformers ◽  
Cellulose Insulation

scholarly journals Improvement of the Space Charge Suppression and Hydrophobicity Property of Cellulose Insulation Pressboard by Surface Sputtering a ZnO/PTFE Functional Film

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1610 ◽  
Author(s):  
Li ◽  
Hao ◽  
Zhang ◽  
Hou ◽  
Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Space Charge ◽  
Photoelectron Spectroscopy ◽  
Power Transformers ◽  
Nano Structure ◽  
X Ray ◽  
Ptfe Composite ◽  
Cellulose Insulation ◽  
Scanning Electron

Oil-impregnated cellulose insulation polymer (oil-paper/pressboard insulation) has been widely used in power transformers. Establishing effective ways of improving the physical and chemical properties of the cellulose insulation polymer is currently a popular research topic. In order to improve the charge injection inhibition and hydrophobic properties of the cellulose insulation polymer used in power transformers, nano-structure zinc oxide (ZnO) and polytetrafluoroethylene (PTFE) films were fabricated on a cellulose insulation pressboard surface via reactive radio frequency (RF) magnetron sputtering. Before the fabrication of their composite film, Accelrys Materials Studio (MS) software was applied to simulate the interaction between the nanoparticles and cellulose molecules to determine the depositing sequence. Simulation results show that the ZnO nanoparticle has a better adhesion strength with cellulose molecules than the PTFE nanoparticle, so ZnO film should be sputtered at first to fabricate the ZnO/PTFE composite film for better film quality. The sputtered, thin films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The space charge injection behavior and the hydrophobicity performance of the untreated pressboard; and the cellulose insulation pressboard with sputtered nano-structure ZnO, PTFE, and the ZnO/PTFE functional films were compared with each other. X-ray photoelectron spectroscopy results showed that ZnO, PTFE, and ZnO/PTFE functional films were all successfully fabricated on the cellulose insulation pressboard surface. Scanning electron microscopy and XRD results present the nano-structure of the sputtered ZnO, PTFE, and ZnO/PTFE functional films and their amorphous states, respectively. The ZnO/PTFE composite functional film shows an apparent space charge suppression effect and hydrophobicity. The amount of the accumulated space charge in the pressboard sputtered ZnO/PTFE composite functional film decreased by about 40% compared with that in untreated cellulose insulation pressboard, and the water contact angle (WCA) increased from 0° to 116°.

scholarly journals A New Concept of Applying Methanol to Dry Cellulose Insulation at the Stage of Manufacturing a Transformer

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1658 ◽  
Author(s):  
Piotr Przybylek
Keyword(s):  
High Temperature ◽  
Moisture Content ◽  
Power Transformers ◽  
Technical Challenge ◽  
Moisture Contents ◽  
Percentage Points ◽  
Time Period ◽  
Drying Techniques ◽  
Heating Up ◽  
Cellulose Insulation

A decisive technical challenge for transformer manufacturers is correctly drying the cellulose insulation. During the production of a transformer, it is necessary to reduce its insulation’s moisture content from about 8% to less than 1% in the shortest possible time period. The drying of insulation is a time-consuming process, and for high-power transformers, it can last up to three weeks. Several drying techniques are used during the production of a transformer, and all of them require heating up the insulation to a high temperature and applying a vacuum. Unfortunately, the use of a high drying temperature above 100 °C can cause a decrease in the degree of cellulose polymerization by over a dozen percentage points. This paper presents a new concept for drying cellulose insulation that does not require heating insulation and applying a vacuum. In this solution, methanol is used as the drying medium. The research results showed the possibility of drying cellulose insulation by means of methanol with different initial moisture contents. The possibility of completely drying pressboard of various thicknesses for a sufficient period of time was also proven. The paper also presents a new concept of both the device and the procedure for drying cellulose insulation by means of methanol.

Regeneration of Cellulose Insulation of Windings of Long-Life Power Transformers

2004 ◽  
Vol 38 (3) ◽  
pp. 178-181
Author(s):  
V. B. Komarov ◽  
M. Yu. L'vov ◽  
Yu. N. L'vov ◽  
B. G. Ershov ◽  
V. N. Bondareva ◽  
...  
Keyword(s):  
Power Transformers ◽  
Long Life ◽  
Cellulose Insulation

scholarly journals Study of the Dielectric Response of Ester Impregnated Cellulose for Moisture Content Evaluation

2018 ◽  
Author(s):  
A Graczkowski ◽  
J Gielniak ◽  
P Przybyłek ◽  
K Walczak ◽  
H Morańda
Keyword(s):  
Moisture Content ◽  
Dielectric Response ◽  
Mineral Oil ◽  
Operating Conditions ◽  
Power Transformers ◽  
Synthetic Ester ◽  
Measurement Results ◽  
Content Evaluation ◽  
Cellulose Insulation ◽  
Non Destructive

<p>Knowledge about moisture content in impregnated cellulose insulation is essential for power transformers when estimating remaining lifetime, planning operating conditions and drying procedure. Frequency dielectric spectroscopy (FDS) is non-destructive, convenient method to asses moisture content of insulation. It is important to study dielectric response of ester-cellulose insulation due to growing number of transformers using synthetic ester MIDEL 7131 as insulation fluid [1, 2]. The paper presents study of dielectric response of synthetic ester-pressboard samples with various moisture content (from dry to 5%) measured in wide temperature range (from 5 ˚C to 50 ˚C). Measurement results for pressboard impregnated with synthetic ester are compared to data of pressboard impregnated with mineral oil. The aim of presented work is to provide patterns of dielectric response of synthetic esterpressboard for accurate moisture content evaluation.</p>

Moisture in cellulose insulation of power transformers - statistics

2013 ◽  
Vol 20 (3) ◽  
pp. 982-987 ◽  
Author(s):  
J. Gielniak ◽  
A. Graczkowski ◽  
H. Moranda ◽  
P. Przybylek ◽  
K. Walczak ◽  
...  
Keyword(s):  
Power Transformers ◽  
Cellulose Insulation

scholarly journals Thermal stability of cellulose insulation in electrical power transformers – A review

2021 ◽  
Vol 252 ◽  
pp. 117196
Author(s):  
Paul Jusner ◽  
Elisabeth Schwaiger ◽  
Antje Potthast ◽  
Thomas Rosenau
Keyword(s):  
Thermal Stability ◽  
Electrical Power ◽  
Power Transformers ◽  
Cellulose Insulation ◽  
Thermal Stability Of
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