CC BY
9УДК 621.45.034
Toirov O.Z.
Doctor of Technical Sciences, Professor, Head of Department "Electrical Machines" Tashkent State Technical University (Uzbekistan, Tashkent)
Yusupov D.T.
PhD in Engineering, Senior Researcher Institute of Energy Problems of the Academy of Sciences of the Republic of Uzbekistan (Uzbekistan, Tashkent)
Nosirov A.
Master Student of the Department "Electrical Machines" Tashkent State Technical University (Uzbekistan, Tashkent)
Avazov J.
Master Student of the Department "Electrical Machines" Tashkent State Technical University (Uzbekistan, Tashkent)
DETERMINATION OF THE ELECTRICAL STRENGTH OF TRANSFORMER OIL
Abstract: the article presents the results of determining the electric strength of oil power transformer TDN-63000/110. The results showed that to moisture concentration in oils 0.2 g/T and the oil is serviceable.
Key words: transformer oil, electrical strength, breakdown voltage, impurities, moisture.
Introduction. One of the main indicators characterizing the insulating properties transformer oils, is their electric strength [1-6]:
Е = Upr / h, (1)
where, Upr - breakdown voltage; h - distance between the electrodes.
The breakdown voltage is very sensitive to the presence of impurities. With the deterioration of the state of transformer oil and the appearance of moistened impurities in it, the electrical strength decreases sharply.
Pure transformer oil, free from various impurities, has a breakdown voltage sufficient for use (more than 60 kV), determined by the electrodes with a distance of 2.5 mm between them.
Materials and methods of research
The most important sign of the state of insulation is the lowest breakdown voltage for transformers and is set according to Table 1 [1-3].
If the voltage applied to the dielectric is gradually increased, then the resistance of the dielectric decreases sharply. This critical state, in which the dielectric becomes a conductor, determines the dielectric strength of the oil (kV/cm). The voltage at which oil breakdown occurs is called breakdown voltage (kV) [4-6].
A decrease in breakdown voltage indicates, as a rule, oil contamination with various impurities.
Table 1.
The lowest breakdown voltage for transformer insulation [1-3]
Operating voltage of the transformer, kV Oil breakdown voltage, kV
Up to 15 (inclusive) thirty
St. 15 to 35 (inclusive) 35
From 60 to 150 (inclusive) 55
From 220 to 500 (inclusive) 60
Arithmetic mean value of breakdown voltage Upr in kV:
U =1Y™ U ■
upr.avg n£-ii=lU/pr.i
(2)
where,
Ur
pr. avg
- breakdown voltage (arithmetic mean), kV;
Upr.i - the value obtained during successive breakdowns, kV; n - the number of breakdowns.
The moisture concentration in the oil is determined according to formula 2:
Upr. avg= -8.543ln(x) + 42.247 (3)
where, Upr.avg. - breakdown voltage (arithmetic mean), kV; x - moisture concentration in oil, g/T. Experimental study and processing of the results
As a result of testing the oil of the power transformer TDN-63000/110 for breakdown voltage the following results are obtained:
Upri, kV Upr2, kV Upr3, kV Upr4, kV Up5, kV
57 55 58 56 59
U.
Inserting formula 2, we define
(57 + 55 + 58 + 56 + 59)
pr.avg
n i=1
Upr
285
5
5
= 57 kV
Let's draw a graph of the change in the breakdown voltage of the oil of the TDN-63000/110 power transformer:
60
59
с
58
57
56
55
54
53
1
2
3 4 5
Sequence number of the test
Fig.1. Graph of breakdown voltage of oil of power transformer TDN-63000/110
Let's determine the moisture concentration in the oil according to formula 3:
57 = -8.543ln(x) + 42.247 8.543ln(x) = -57 + 42.247 8.543ln(x) = -14.753 ln(x) = -1.727 x = 0.2
Moisture concentration in power transformer oil TDN-63000/110 is 0.2 g/T. According to Table 1, the standard value of the breakdown voltage of the oil in operation must be at least 55 kV for a power transformer with a voltage of 110 kV. Conclusion
Moisture concentration in power transformer oil TDN-63000/110 is 0.2 g/T. Transformer oil is serviceable.
REFERENCES:
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Serebryakov A.S., Semenov D.A. Diagnosis of housing insulation of distribution transformers // ELECTRO. 2013. No. 1. P. 47-51.
Power transformers: Ref. book. / ed. S.D. Lizunova, A.K. Lokhanin. Moscow: Energoizdat, 2004.4. Klyavin Ya., Poznyak A.A. Modeling and optimization of hardening and stress states in obtaining materials // Hydromechanical and heat transfer, 1990. 178p.
Тоиров О.З., Цыпкина В.В., Иванова В.П., Аширов А.Р. Математическая модель электрических процессов в комбинированном контрольном кабеле // Universum: технические науки: электрон. научн. журн. 2021. 6(87). DOI -10.32743/UniTech.2021.87.6.12003.
Toirov O.Z., Shatursunov S., Akberdiev M.A. Method for calculating the level of enamelling and temperature conditions on current conductors at different speeds in cable production processes // Universum: технические науки: электрон. научн. журн. 2022. 5(98). DOI - 10.32743/UniTech.2022.98.5.13819. Toirov O.Z. и др. Automation of high speed computer network control // Universum: технические науки: электрон. научн. журн. 2022. 5(98). URL: https://7universum.com/ru/tech/archive/item/13807 (дата обращения: 01.06.2022).
