Power transformers, autotransformers and oil reactors (hereinafter referred to as transformers)

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Encyclopedia of radio electronics and electrical engineering / Electrician

Annex 3. Standards for testing electrical equipment and apparatus for electrical installations of consumers

Power transformers, autotransformers and oil reactors (hereinafter referred to as transformers)

Free technical library

Encyclopedia of radio electronics and electrical engineering / Rules for the technical operation of consumer electrical installations (PTE)

Comments on the article

K, T, M - are produced within the time limits established by the PPR system.

Name of the test	Type of test	Test norms	Directions
2.1. Determining the conditions for switching on the transformer	К	Transformers that have been overhauled with a complete or partial replacement of windings or insulation are subject to drying, regardless of the measurement results. Transformers that have been overhauled without replacing windings or insulation can be put into operation without drying or drying if the oil and winding insulation indicators comply with the requirements of Table 1 (Appendix 3.1), and also subject to the conditions for the active part to stay in the air. The duration of work associated with depressurization should be no more than: 1) for transformers for voltage up to 35 kV - 24 hours at relative humidity up to 75% and 16 hours at relative humidity up to 85%; 2) for transformers with a voltage of 110 kV and more - 16 hours at a relative humidity of up to 75% and 10 hours at a relative humidity of up to 85%. If the transformer inspection time exceeds the specified one, but not more than 2 times, then the control drying of the transformer must be carried out.	When filling transformers with oil with other characteristics than that of the one drained before repair, a change in the insulation resistance and tgδ may be observed, which should be taken into account in a comprehensive assessment of the state of the transformer. The conditions for switching on dry transformers without drying are determined in accordance with the instructions of the manufacturer When commissioning transformers that have been overhauled under operating conditions without changing windings and insulation, it is recommended to perform control in accordance with the requirements given in the regulatory and technical documentation
2.2. Insulation resistance measurement:
1) windings	K, T, M	The lowest allowable values of insulation resistance, at which it is possible to put transformers into operation after a major overhaul, are regulated by the instructions in Table. 2 (Annex 3.1) Measurements during operation are made with unsatisfactory results of oil tests and (or) chromatographic analysis of gases dissolved in oil, as well as in the scope of complex tests For transformers for a voltage of 220 kV, it is recommended to measure the insulation resistance at a temperature of at least 20 ° C, and up to 150 kV - at least 10 ° C	Measured with a megaohmmeter for a voltage of 2500 V It is carried out both before the repair and after its completion. See also note 3 Measurements are made according to the schemes of Table. 3 (Appendix 3.1). During the current repair, the measurement is carried out if the transformer is not specifically required for this purpose.
2) available tie rods, bands, yoke half bands, pressure rings, yokes and electrostatic screens	К	The measured values must be at least 2 MΩ and the insulation resistance of the yokes must be at least 0,5 MΩ	It is measured with a megohmmeter for a voltage of 1000 V for oil transformers only during major repairs, and for dry transformers and during current repairs
2.3. Measurement of the dielectric loss tangent tgδ of winding insulation	K, M	For transformers that have undergone a major overhaul, the highest allowable values of tgδ insulation are given in Table. 4 (Annex 3.1)	During interrepair tests, the measurement is carried out at power transformers for a voltage of 110 kV and more or a power of 31500 kVA and more
		In operation, the value of tgδ is not standardized, but it must be taken into account in a comprehensive assessment of the results of measuring the state of the insulation. Measurements during operation are carried out with unsatisfactory results of oil tests and (or) chromatographic analysis of gases dissolved in oil, as well as in the scope of complex tests. The results of measurements of winding insulation tgδ, including the dynamics of their changes, should be taken into account when considering the data of all tests comprehensively	For transformers for a voltage of 220 kV, tgδ is recommended to be measured at a temperature not lower than 20 °C, and up to 150 kV, not lower than 10 °C. Measurements are made according to the schemes of Table. 3 (Annex 3.1) See also note 3
2.4. Power frequency overvoltage test:
1) insulation of windings 35 kV and below, together with inputs	К	See table. 5 (Appendix 3.1). Test duration - 1 min. The highest test voltage with partial replacement of windings is assumed to be 90%, and during major repairs without replacing windings and insulation or with replacing insulation, but without replacing windings - 85% of the value indicated in Table. 5 (Annex 3.1)	When overhauling oil-filled transformers without replacing windings and insulation, testing the insulation of windings with increased voltage is not necessary. Insulation testing of dry-type transformers is mandatory
2) insulation of testable tie rods, bandages, yoke half bandages, pressure rings, yoke beams and electrostatic screens		Produced with a voltage of 1 kV for 1 min., unless more stringent test standards are established by the manufacturer	The test is carried out in case of opening the transformer to inspect the active part. See also 3.25
3) isolation circuits of protective equipment	К	Produced with a voltage of 1 kV for 1 min. The value of the test voltage when testing the insulation of electrical circuits of manometric thermometers is 0,75 kV for 1 min.	The insulation (with respect to grounded parts) of circuits with connected current transformers, gas and protective relays, oil gauges, shut-off valve and temperature sensors is tested with the connectors of manometric thermometers disconnected, the circuits of which are tested separately
2.5. DC winding resistance measurement	K, M	Should differ by no more than 2% from the resistance obtained on the corresponding branches of other phases, or from the values of factory and previous operational measurements, unless there are special reservations in the transformer passport During operation, measurements can be made during complex tests of the transformer	It is carried out on all branches, unless otherwise indicated in the factory passport and if this does not require the removal of the active part. Before measuring the resistance of the windings of transformers equipped with voltage regulation devices, at least three complete switching cycles should be performed.
2.6. Checking the transformation ratio	К	It should differ by no more than 2% from the values obtained on the corresponding branches of other phases, or from the factory (passport) data. In addition, for transformers with an on-load tap-changer, the difference in transformation ratios should not exceed the value of the control step	Produced at all stages of the switch
2.7. Checking the connection group of the windings of three-phase transformers and the polarity of the outputs of single-phase transformers	К	The group of connections must correspond to the passport data, and the polarity of the terminals must correspond to the designations on the shield or transformer cover	Produced during repairs with partial or complete replacement of windings
2.8. Measurement of current and no-load losses	К	The value of current and no-load losses is not standardized. Measurements are made for transformers with a capacity of 1000 kVA and more	One of the following measurements is taken: a) at rated voltage, no-load current is measured 2) at low voltage, no-load losses are measured according to the schemes according to which the measurements were made at the factory
2.9. Assessment of the state of switching devices	К	Carried out in accordance with the requirements of the instructions of manufacturers or normative and technical documents
2.10. Tank density test	К	The duration of the test in all cases is at least 3 hours. Oil temperature in the tank of transformers with voltage up to 150 kV is not lower than 10 °С, transformers 220 kV - not lower than 20 °С There should be no oil leakage. Sealed transformers and those without an expander are not tested	Produced: for transformers with voltage up to 35 kV inclusive - by hydraulic pressure of the oil column, the height of which above the level of the filled expander is assumed to be 0,6 m; for wavy tanks and with plate radiators - 0,3 m for transformers with oil film protection - by creating an excess air pressure of 10 kPa inside the flexible shell for other transformers - by creating an excess pressure of nitrogen or dry air of 10 kPa in the above-oil space of the expander
2.11. Checking cooling devices	К	Devices must be in good working order and meet the requirements of the factory instructions	Produced according to standard and factory instructions
2.12. Checking the means of protecting the oil from exposure to ambient air	K, T, M	Checking the air dryer, nitrogen and film oil protection systems, thermosiphon or adsorbing filters is carried out in accordance with the requirements of the manufacturer's instructions or regulatory and technical documents	Indicator silica gel should have a uniform blue color of the grains. A change in the color of the silica gel grains to pink indicates its moisture.
2.13. Transformer oil test:			Produced: 1) after major repairs of transformers; 2) at least 1 time in 5 years for transformers with a power higher than 630 kVA, operating with thermosiphon filters; 3) at least 1 time in 2 years for transformers with a power higher than 630 kVA, operating without thermosyphon filters Produced once every 1 years, as well as during complex tests of the transformer
1) from transformers	K, T, M	For transformers with voltage up to 35 kV inclusive - according to the indicators of paragraphs 1 - 5, 7 of the table. 6 (Appendix 3.1)
1) from transformers	K, T, M	For transformers with a voltage of 110 kV and above - according to the indicators of paragraphs 1 - 9 of Table. 6 (Appendix 3.1), and for transformers with film protection, additionally according to clause 10 of the same table
2) from the tanks of the contactors of the on-load tap-changers	T, M	Oil should be changed: 1) at breakdown voltage below 25 kV in contactors with 10 kV insulation, 30 kV - with 35 kV insulation, 35 kV - with 40 kV insulation, 110 kV - with 220 kV insulation; 2) if water is found in it (qualitative definition) or mechanical impurities (visual definition)	Produced in accordance with the manufacturer's instructions for this switch
2.14. Testing of transformers by switching on the rated voltage	К	In the process of 3 - 5-fold switching on of the transformer at rated voltage and exposure under voltage for a time of at least 30 minutes. there should be no phenomena indicating an unsatisfactory condition of the transformer	Transformers operating in a block with a generator are connected to the network by raising the voltage from zero
2.15. Chromatographic analysis of gases dissolved in oil	М	Assessment of the state of the transformer and determination of the nature of possible defects is carried out once every 1 months. in accordance with the recommendations of the guidelines for the diagnosis of developing defects based on the results of a chromatographic analysis of gases dissolved in oil	The state of transformers is assessed by comparing the measured data with the boundary concentrations of gases in oil and by the rate of increase in the concentration of gases in oil
2.16. Moisture assessment of solid insulation	K, M	Permissible value of moisture content of solid insulation after overhaul - 2%, operated - 4% by weight; during operation it is allowed not to determine if the moisture content of the oil does not exceed 10 g/t Produced for the first time in 10 - 12 years after switching on, then 1 time in 4 - 6 years for transformers with a voltage of 110 kV and higher with a power of 60 MVA or more	During a major overhaul, it is determined by the moisture content of the samples placed in the tank, in operation - by calculation
2.17. Assessment of the state of the paper insulation of the windings:
by the presence of furan compounds in oil	М	The permissible content of furan compounds, including furfural, is given in paragraph 11 of the table. 6 (Annex 3.1)	Produced by chromatographic methods 1 time in 12 years, and after 24 years of operation - 1 time in 4 years
according to the degree of polymerization of paper	К	The resource of paper insulation of the windings is considered exhausted when the degree of polymerization of paper decreases to 250 units
2.18. Short circuit resistance measurement (Z_k) transformer	K, M	Z values_k should not exceed the original by more than 3%. For three-phase transformers, the difference in Z values is additionally normalized_k by phases on the main and extreme branches - it should not exceed 3%	Produced for transformers with a capacity of 125 MVA or more (in the presence of an on-load tap changer - on the main and both extreme branches) after exposure to a short-circuit current transformer exceeding 70% of the calculated value, as well as in the scope of complex tests
2.19. Bushing test	K, M	Manufactured in accordance with Section 10
2.20. Testing built-in current transformers	K, M	Produced in accordance with the instructions of paragraphs 20.1, 20.3.2, 20.5, 20.6, 20.7 section 20
2.21. Thermal imaging control	М	Produced in accordance with established standards and manufacturer's instructions

Notes
1. Tests according to paragraphs 2.1, 2.3, 2.8 - 2.12, 2.13, 2.15 and 2.16 for dry-type transformers of all capacities are not carried out.
2. Measurements of insulation resistance and tgδ must be made at the same temperature or reduced to the same temperature. The measured values of tgδ insulation at an insulation temperature of 20 °C and above, not exceeding 1%, are considered satisfactory, and their recalculation to the initial temperature is not required.
3. Power transformers 6 - 10 kV with power up to 630 kVA are not subjected to overhaul tests and measurements.

See other articles Section Rules for the technical operation of consumer electrical installations (PTE).

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Controlling objects using air currents 04.05.2024

The development of robotics continues to open up new prospects for us in the field of automation and control of various objects. Recently, Finnish scientists presented an innovative approach to controlling humanoid robots using air currents. This method promises to revolutionize the way objects are manipulated and open new horizons in the field of robotics. The idea of controlling objects using air currents is not new, but until recently, implementing such concepts remained a challenge. Finnish researchers have developed an innovative method that allows robots to manipulate objects using special air jets as "air fingers". The air flow control algorithm, developed by a team of specialists, is based on a thorough study of the movement of objects in the air flow. The air jet control system, carried out using special motors, allows you to direct objects without resorting to physical ... >>

Purebred dogs get sick no more often than purebred dogs 03.05.2024

Caring for the health of our pets is an important aspect of the life of every dog owner. However, there is a common assumption that purebred dogs are more susceptible to diseases compared to mixed dogs. New research led by researchers at the Texas School of Veterinary Medicine and Biomedical Sciences brings new perspective to this question. A study conducted by the Dog Aging Project (DAP) of more than 27 companion dogs found that purebred and mixed dogs were generally equally likely to experience various diseases. Although some breeds may be more susceptible to certain diseases, the overall diagnosis rate is virtually the same between both groups. The Dog Aging Project's chief veterinarian, Dr. Keith Creevy, notes that there are several well-known diseases that are more common in certain breeds of dogs, which supports the notion that purebred dogs are more susceptible to disease. ... >>

Random news from the Archive

Faux leather against drugs 30.09.2018

Researchers from the University of Chicago offer a peculiar way to deal with drug addiction - with the help of patches of genetically modified skin.

As you know, not so long ago, biotechnologists have a very effective tool for making the necessary amendments to the genome - a tool called CRISPR (which we have repeatedly written about). Using CRISPR, it is possible to insert genes that code for certain proteins into the DNA of skin cells, and then, after waiting for the skin cells to form the desired piece of skin, transplant them onto the body.

Previously, Xiaoyang Wu and his colleagues had already done similar experiments, forcing skin cells to synthesize insulin, so that the transplanted patch helped maintain normal blood sugar levels in diabetic mice. Now, instead of insulin, they decided to introduce the gene for butyrylcholinesterase, an enzyme that destroys cocaine, into skin cells. We have this enzyme anyway, it works with different substances, and the cocaine molecule is just similar to the molecules that butyrylcholinesterase deals with. However, the enzyme that we have is not very active, at least in relation to cocaine. But there is an improved laboratory version of it, which breaks down the drug 4400 times more efficiently.

Butyrylcholinesterase is much larger than insulin, and there were doubts that skin cells, which normally do not synthesize it (the enzyme is normally formed in the liver), will be able to handle it. However, the transplanted anti-cocaine skin worked as it should: two weeks after the transplant, the mice calmly tolerated the dose of the drug that had literally killed them before.

Other interesting news:

▪ Apple iMac computers

▪ Multicolored photons

▪ Individual beacon to rescue the victim

▪ The debut of the robot conductor

▪ Three years under the gaze of TV cameras

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Lighting. Article selection

▪ John Rockefeller article. Famous aphorisms

▪ article Why is the Tierra del Fuego archipelago called so? Detailed answer

▪ article Coca bush. Legends, cultivation, methods of application

▪ article Bonding leather to iron and wood. Simple recipes and tips

▪ article The spectator draws cards conceived by others. Focus Secret

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews