Transformer oils and other liquid dielectrics are used for filling electrical transformers, oil switches, circulating cooling systems, and other high-voltage devices, where they are used as an insulating and heat-removing medium, for extinguishing an electric arc arising between the contacts of a switch, and also as a cooling agent. Electrical devices operate at elevated temperatures.
| Index | Rate by brand | ||||||
| Non-additive oils | Oil with additives | ||||||
| T22 | T30 | T46 | T57 | TP-22 | TP-30 | TP-46 | |
| Kinematic viscosity, cSt: at 50 ° С at 40 ° С | 20-23 - | 28-32 - | 44-48 - | 55-59 - | 20-23 - | - 41,4-50,6 | - 61,2-74,8 |
| Viscosity index, not less | |||||||
| Acid number, mg KOH / g oil, no more | 0,02 | 0,02 | 0,02 | 0,05 | 0,07 | 0,5 | 0,5 |
| Demulsification number, s, no more | |||||||
| Color, units CNT, no more | 2,0 | 2,5 | 3,0 | 4,5 | 2,5 | 3,5 | 5,5 |
| Temperature, ° С: flashes (open crucible), not lower than solidification, not higher | -15 | -10 | -10 | - | -15 | -10 | -10 |
| Density at 20 ° С, kg / m 3, no more | |||||||
| Ash content of base oil, %, no more | 0,005 | 0,005 | 0,010 | 0,020 | - | 0,005 | 0,005 |
| Oxidation stability: residue after oxidation, %, no more acid number after oxidation, mg KOH / g | 0,10 - | 0,10 - | 0,10 - | - - | 0,005 - | 0,01 0,4 | 0,008 1,5 |
| |
rounds (70-80 0 C). With electric discharges, the temperature rises even more, which accelerates the oxidation of dielectrics and leads to the formation of an insoluble sediment (sludge), and during extinguishing of the electric arc - to the formation of carbon and water particles.
Sludge and carbon particles, deposited on the surface of the internal elements of the electrical apparatus, impair heat transfer, violate electrical insulation, which can cause an accident. The appearance of water in the dielectric leads to a decrease in its dielectric strength. The presence of acids will corrode the metal parts of the machine and deteriorate the cotton insulation.
Table 9. Quality standards for transformer oils
GOST 9972-74 * and 3274-72 *
| Index | Petroleum oils grades | Synthetic oil OMTI | ||
| TP-22S / TP-22B | TP-30 | TP-46 | ||
| Kinematic viscosity at 50 0 С, mm 2 / s | 20-23 | 28-32 | 44-48 | 28-29 |
| 0,07/0,02 | 0,03 | 0,05 | 0,04 | |
| Stability: mass fraction sediment after oxidation,%, no more | 0,005/0,01 | 0,005 | 0,005 | - |
| Acid number after oxidation, mg KOH per 1 g of oil, no more | 0,1/0,35 | 0,6 | 0,7 | - |
| Ash output,%, no more | 0,005/0,01 | 0,005 | 0,005 | 0,15 |
| Demulsification number, min, no more | 3/5 | 3,0 | 3,0 | 3,0 |
| Flash point, determined in an open crucible, 0 С, not lower | 186/180 | |||
| Autoignition temperature in air, 0 С, not lower | - | |||
| -15 | -10 | -10 | -17 |
Note. The numbers in the brand designation mean the average kinematic viscosity of the oil.
In connection with these most important requirements for the quality of the dielectric are high resistance (stability) against oxidation, the absence of water and mechanical impurities, enough low temperature solidification, high dielectric strength and low dielectric losses.
Dielectric losses in a dielectric are caused by conduction currents arising from the process of polarization of molecules and ions under the action of an alternating electric field. Charge carriers can be ions formed as a result of the dissociation of molecules, as well as larger colloidal particles... Dielectric losses are estimated by the tangent of the angle of dielectric losses tgδ. The lower the tanδ, the lower the dielectric losses in the oil. The tanδ value for a given dielectric depends on its temperature and increases when the oil is heated. Electric strength and tgδ are determined according to GOST 6581-75.
The service life of the dielectric in transformers is 5-10 years. In this regard, very high requirements are imposed on its quality.
Transformer oils are obtained from low-sulfur and sulphurous oils. From low-sulfur oils, oils of two grades are produced: transformer without additives and transformer with antioxidant additive ionol. Oils are subjected to sulfuric acid purification, followed by neutralization with alkali and sometimes with additional purification with bleaching earth.
Two grades of transformer oil are produced from sulphurous oils: selective phenolic oil with an antioxidant additive ionol and oil with hydrogenation purification. Oils with increased content aromatic hydrocarbons have a high oxidation and electrical resistance, in lesser degree emit gases when exposed to electrical discharges. Complete removal aromatic hydrocarbons from oil in the process of purification worsens its antioxidant properties, however, an excessive amount of aromatic hydrocarbons, especially polycyclic, increases the tgδ of transformer oils. Therefore, for each type of oil, an optimal ratio of naphthenic and aromatic hydrocarbons is established. The characteristics of the main properties of transformer oils are given in table. nine
Table 10 Basic properties of liquid and plastic dielectrics
| Index | Petroleum oil | Silicon-organic liquid PESZH-D | Petroleum jelly condenser | |
| transformer | for capacitors | |||
| Density at 20 0 С, kg / m 3 | 880-890 | 900-920 | 990-1000 | 820-840 |
| Acid number, mg KOH per 1 g of oil, no more | 0,01-0,05 | 0,01-0,015 | 0,05-0,07 | 0,03-0,04 |
| Pour point, 0 С, not higher | -45 | -45 | -80 | 37-40 |
| Flash point of vapors, 0 С, not lower | - | - | ||
| Ash content,%, not more | 0,005 | 0,0015 | - | 0,004 |
| Viscosity at 20 0 С, 10 -6 m 2 / s | 28-30 | 35-40 | 70-80 | - |
| Specific volume resistivity at 20 0 С, Ohm m | 10 12 -10 13 | 10 12 -10 13 | 10 10 -10 12 | 10 12 -10 13 |
| Relative dielectric constant at 20 0 С | 2,1-2,4 | 2,1-2,3 | 2,6-2,0 | 3,8-4,0 |
| Dielectric loss tangent at 20 0 С and 50 Hz | 0,001-0,003 | 0,003-0,005 | 0,0002-0,003 | 0,0002 |
| Electric strength at 20 0 С and 50 Hz, MV / m | 15-20 | 20-25 | 18-20 | 20-22 |
Note. Transformer oil is produced in four grades: TK, T-750, T-1500, PT.
All electrical insulating liquids (oils) should not contain water-soluble acids, alkalis and mechanical impurities.
Transformer oil is a refined oil fraction, that is, it is a mineral oil. It is obtained by distillation of oil, where this fraction boils at 300 - 400 ° C. Depending on the grade of the feedstock, the properties of transformer oils are different. The oil has a complex hydrocarbon composition, where average weight molecules range from 220 to 340 amu The table shows the main components and their percentage in the composition transformer oil.
The properties of transformer oil as an electrical insulator are mainly determined by the value. Therefore, the presence of water and fibers in the oil is completely excluded, since any mechanical impurities worsen this indicator.
The pour point of transformer oil is from -45 ° C and below, this is important to ensure its mobility in low-temperature operating conditions. The lowest oil viscosity contributes to efficient heat dissipation, even at temperatures from 90 to 150 ° C in case of outbreaks. For different brands of oils, this temperature can be 150 ° С, 135 ° С, 125 ° С, 90 ° С, not lower.
An extremely important property of transformer oils is their stability under oxidation conditions; transformer oil must maintain the required parameters for a long period of operation.
As for the RF specifically, all grades of transformer oils used in industrial equipment are necessarily inhibited by an antioxidant additive - ionol (2,6-di-tertiary butylparacresol, also known as agidol-1). The additive interacts with active peroxide radicals arising in the chain of the oxidative reaction of hydrocarbons. Thus, inhibited transformer oils have a pronounced induction period during oxidation.
At first, oils susceptible to additives oxidize slowly as the resulting oxidation chains are interrupted by the inhibitor. When the additive is depleted, the oil oxidizes at the normal rate as without the additive. The longer the induction period of oil oxidation, the higher the effectiveness of the additive.
A lot of the effectiveness of the additive is associated with the hydrocarbon composition of the oil, and with the presence of non-hydrocarbon impurities that promote oxidation, which can be nitrogenous bases, petroleum acids and oxygen-containing products of oil oxidation.
When the petroleum distillate is refined, the aromatic content is reduced, non-hydrocarbon inclusions are removed, and ultimately the stability of the ionol-inhibited transformer oil is improved. Meanwhile, there is an international standard “Specification for Fresh Petroleum Insulating Oils for Transformers and Circuit Breakers”.
Transformer oil is flammable, biodegradable, almost non-toxic and does not harm the ozone layer. The density of transformer oil ranges from 840 to 890 kilograms per cubic meter. One of essential properties- viscosity. The higher the viscosity, the higher the dielectric strength. At the same time, for normal operation in and in circuit breakers, the oil should not be very viscous, otherwise the cooling of the transformers will not be effective, and the circuit breaker will not be able to quickly break the arc.
A compromise is needed here regarding viscosity. Typically, the kinematic viscosity at 20 ° C, for most transformer oils, lies in the range from 28 to 30 mm2 / s.
Before filling the apparatus with oil, the oil is purified using deep thermal vacuum treatment. According to the current guidance document "Scope and Test Standards for Electrical Equipment" (RD 34.45-51.300-97), the air concentration in transformer oil, poured into transformers with nitrogen or film protection, into sealed instrument transformers and sealed bushings, should not be higher than 0, 5 (determined by gas chromatography), and the maximum water content is 0.001% by weight.
For power transformers without film protection and for leaky bushings, a water content of no more than 0.0025% of the mass is permissible. As for the content of mechanical impurities, which determines the oil purity class, it should not be worse than the 11th for equipment with a voltage of up to 220 kV, and no worse than the 9th for equipment with a voltage higher than 220 kV. The breakdown voltage, depending on the operating voltage, is shown in the table.
When oil is filled, the breakdown voltage is 5 kV lower than that of oil before filling into the equipment. A decrease in the cleanliness class by 1 and an increase in the percentage of air by 0.5% is permissible.
Oxidation conditions (method for determining stability - according to GOST 981-75)
The pour point of the oil is determined in a test where a tube of thickened oil is tilted 45 ° and the oil remains at the same level for a minute. For fresh oils, this temperature should not be lower than -45 ° C.
This parameter has key value for . However, in different climatic zones pour point requirements are different. For example, in southern regions it is allowed to use transformer oil with a pour point of -35 ° C.
Depending on the operating conditions of the equipment, the standards may vary, there may be some deviations. For example, arctic grades of transformer oil should not solidify at temperatures above -60 ° C, and the flash point drops to -100 ° C (flash point is the temperature at which heated oil produces vapors that become flammable when mixed with air).
In general, the flash point should not be lower than 135 ° C. Also important are characteristics such as the ignition temperature (the oil ignites and burns at it for 5 or more seconds) and the autoignition temperature (at a temperature of 350-400 ° C, the oil ignites even in a closed crucible in the presence of air).
Transformer oil has a thermal conductivity of 0.09 to 0.14 W / (m × K), and it decreases with increasing temperature. The heat capacity, on the other hand, increases with increasing temperature, and can be from 1.5 kJ / (kg × K) to 2.5 kJ / (kg × K).
With coefficient thermal expansion the standards for the size of the expansion tank are related, and this coefficient is in the region of 0.00065 1 / K. The resistivity of transformer oil at 90 ° C and under conditions of an electric field strength of 0.5 MV / m in any case should not be higher than 50 Ghm * m.
As well as viscosity, resistivity oil decreases with increasing temperature. The dielectric constant- in the range from 2.1 to 2.4. The tangent of the dielectric loss angle, as mentioned above, is associated with the presence of impurities, so for pure oil it does not exceed 0.02 at 90 ° C under conditions of a field frequency of 50 Hz, and in oxidized oil it can exceed 0.2.
The dielectric strength of the oil is measured during a 2.5 mm breakdown test with an electrode diameter of 25.4 mm. The result should not be lower than 70 kV, and then the dielectric strength will be at least 280 kV / cm.
In spite of Taken measures, transformer oil can absorb gases and dissolve a significant amount of them. Under normal conditions, 0.16 milliliters of oxygen, 0.086 milliliters of nitrogen and 1.2 milliliters of carbon dioxide will easily dissolve in one cubic centimeter of oil. Obviously, oxygen will begin to oxidize a little. If gases are released on the contrary, this is a sign of a winding defect. So, by the presence of gases dissolved in transformer oil, defects of transformers are revealed through chromatographic analysis.
The service lives of transformers and oil are not directly related. If the transformer is capable of operating reliably for 15 years, then it is advisable to clean the oil every year, and regenerate after 5 years. However, to prevent the rapid depletion of the oil resource, quite specific measures are provided, the adoption of which will significantly extend the service life of the transformer oil:
Installation of expanders with filters to absorb water and oxygen, as well as gases emitted from oil;
Avoiding working oil overheating;
Periodic cleaning;
Continuous oil filtration;
The introduction of antioxidants.
High temperatures, the reaction of oil with conductors and dielectrics - all this promotes oxidation, which is intended to prevent the antioxidant additive mentioned at the beginning. But regular cleaning is still required. High-quality cleaning of the oil returns it to a usable condition.
What can serve as a reason for the withdrawal of transformer oil from service? It can be contamination of the oil with permanent substances, the presence of which did not lead to deep changes in the oil, and then it is enough to carry out mechanical cleaning. In general, there are several cleaning methods: mechanical, thermophysical (distillation) and physicochemical (adsorption, coagulation).
If an accident occurs, the breakdown voltage has dropped sharply, carbon deposits have appeared, or chromatographic analysis has revealed a problem, the transformer oil is purified directly in the transformer or in the switch, simply by disconnecting the device from the network.
When regenerating used transformer oil, up to 3 fractions of base oils are obtained for the preparation of other commercial oils, such as motor, hydraulic, transmission oils, cutting fluids and greases. On average, after regeneration, 70-85% of oil is obtained, depending on the applied technological method. Chemical regeneration is more expensive. When regenerating transformer oil, it is possible to obtain up to 90% of the base oil of the same quality as the fresh one.
25.1 Quality control of transformer oils during receipt and storage
A batch of transformer oil arriving at the power plant must be subjected to laboratory tests in accordance with the requirements of section 5.14 of the Rules technical exploitation power plants and networks Russian Federation(RD 34.20.501-95).
Standard values of quality indicators for fresh oil, depending on its brand, are given in table. 25.1. The table was compiled on the basis of the requirements of the current GOST and TU for the quality of fresh transformer oils at the time of development of this document.
25.1.1 Inspection of transformer oil after transportation
An oil sample is taken from the transport container in accordance with the requirements of GOST 2517-85. A sample of transformer oil is subjected to laboratory tests according to quality indicators 2, 3, 4, 11, 12, 14, 18 from table. 25.1.
Quality indicators 2, 3, 4, 14, 18 are determined before the oil is drained from the transport container, and 11 and 12 can be determined after the oil is drained.
Indicator 6 should be additionally determined only for special arctic oils.
25.1.2 Control of transformer oil drained into tanks
Transformer oil, poured into oil storage tanks, is subjected to laboratory tests according to quality indicators 2, 3, 4, 18 from table. 25.1 immediately after it has been taken from the transport container.
25.1.3 Inspection of stored transformer oil
Stored oil is tested according to quality indicators 2, 3, 4, 5, 11, 12, 14, 18 from table. 25.1 with a frequency of at least 1 time in 4 years.
25.1.4. Expanding the scope of control
Oil quality indicators from table. 25.1, not specified in clauses 25.1.1-25.1.3, are determined, if necessary, by the decision of the technical manager of the energy company.
25.2 Quality control of transformer oils during filling
In electrical equipment
25.2.1 Requirements for fresh transformer oil
Fresh transformer oils prepared for filling into new electrical equipment must meet the requirements of table. 25.2.
25.2.2 Requirements for recovered and refined oils
Regenerated and (or) purified operating oils, as well as their mixtures with fresh oils, prepared for filling into electrical equipment after repair, must meet the requirements of Table. 25.3.
25.3 Quality control of transformer oils during their operation
In electrical equipment
25.3.1 Scope and frequency of tests
The scope and frequency of oil tests are indicated in the sections for specific types of electrical equipment, normative values quality indicators are given in table. 25.4.
Based on the results of laboratory tests of the oil, the areas of its operation are determined:
The area of "normal oil condition" (the range from the maximum allowable values after oil filling in electrical equipment, given in table. 25.2, column 4, and to the values limiting the area of normal oil condition in operation, given in table. 25.4, column 3), when the state of the oil quality guarantees reliable performance electrical equipment and at the same time, the minimum necessary control of indicators 1-3 from the table is sufficient. 25.4 (abridged analysis);
The area of "risk" (the interval from the values limiting the area of normal oil condition, given in table 25.4, column 3, to the maximum permissible values of oil quality indicators in operation, given in table 25.4, column 4), when the deterioration of even one quality indicator oil leads to a decrease in the reliability of the operation of electrical equipment and more frequent and extended monitoring is required to predict its service life and (or) take special measures to restore the operational properties of the oil in order to prevent its replacement and the withdrawal of electrical equipment for repair.
Table 25.1
Quality indicators of fresh domestic transformer oils
Index |
Oil brands and numbers normative documents |
||||||||||
THAT |
THAT |
THAT |
THAT |
THAT |
GOST 10121-76 |
TU 38.401.1033-95 |
TU 38.101.1271-89 |
THAT |
test method standard |
||
1. Kinematic viscosity, mm / s (CCt), not more at: |
|||||||||||
2. Acid number, mg KOH per 1 g of oil, no more |
GOST 5985-79 |
||||||||||
3. Flash point in a closed crucible, ° С, not lower |
GOST 6356-75 |
||||||||||
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
GOST 6307-75 |
|||||
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
GOST 6370-83 |
|
6. Pour point, ° С, not higher |
GOST 20287-91 |
||||||||||
7. Ash content,%, no more |
GOST 1461-75 |
||||||||||
8. Soda test, optical density, points, no more |
GOST 19296-73 |
||||||||||
9. Clarity at 5 ° С |
Transparent |
Transparent |
Transparent |
GOST 982-80, p. 5.3 |
|||||||
10. Test of corrosive effects on copper plates of M1 or M2 grade in accordance with GOST 859-78 |
Withstands |
Withstands |
Withstands |
Withstands |
Withstands |
Withstands |
Withstands |
Withstands |
GOST 2917-76 |
||
11. Tangent of dielectric loss angle,%, not more at 90 ° С |
GOST 6581-75 |
||||||||||
12. Stability against oxidation: |
|||||||||||
Mass of volatile acids, mg KOH per 1 g of oil, no more |
|||||||||||
Absence |
Absence |
Absence |
Absence |
Absence |
Absence |
||||||
Acid number of oxidized oil, mg KOH per 1 g of oil, no more |
|||||||||||
13. Stability against oxidation, IEC method, induction period, h, not less |
IEC 1125 (V) -92 |
||||||||||
14. Density at 20 ° С, kg / m3, no more |
GOST 3900-85 |
||||||||||
15. Color on the TsNT colorimeter, CNT units, no more |
GOST 20284-74 |
||||||||||
GOST 19121-73 |
|||||||||||
RD 34.43.105-89 |
|||||||||||
18. Appearance |
Clean, transparent, free from visible dirt, water, particles, fibers |
Visual control |
|||||||||
___________________
___________________
* at 40 ° С,
** at -40 ° С.
(Modified edition, Amendment No. 2)
Table 25.2
Requirements for the quality of fresh oils prepared for filling
into new electrical equipment
Note |
||||
after filling into electrical equipment |
||||
6581-75, kV, not less |
Electrical equipment: |
|||
up to 35 kV inclusive |
||||
from 60 to 150 kV inclusive |
||||
from 220 to 500 kV inclusive |
||||
Electrical equipment: |
||||
over 220 kV |
||||
When using arctic oil (AGK) or oil for switches (MBT), the value of this indicator is determined by the standard for the oil brand according to table. 25.1 |
||||
GOST 1547-84 (quality) |
Absence |
Absence |
||
Absence (11) |
Absence (12) |
|||
6. The tangent of the angle of dielectric losses at 90 ° С according to GOST 6581-75,%, |
Power and |
|||
no more* |
||||
Electrical equipment of all types and voltage classes |
Absence |
Absence |
||
In arbitration control, the definition of this indicator should be carried out in accordance with the IEC 666-79 standard or / and RD 34.43.208-95 |
||||
9. Pour point, GOST 20287-91, ° С, not higher |
||||
11. Stability against oxidation according to GOST 981-75: |
Power and instrument transformers from 110 to 220 kV inclusive |
Process conditions: 120 ° С, 14 h, 200 ml / min О2 |
||
acid number of oxidized oil, mg KOH / g oil, no more; |
||||
Power and measuring transformers over 220 to 750 kV inclusive, oil-filled bushings 110 kV and above |
In accordance with the requirements of the standard for a specific brand of oil, approved for use in this equipment |
For fresh oil, determination according to IEC 474-74 or 1125 (B) -92 is allowed |
||
* It is allowed to use for filling power transformers up to 500 kV inclusive TKp transformer oil according to TU-38.101.980-81 and up to 220 kV inclusive TKp oil according to TU 38.401.5849-92, as well as their mixtures with other fresh oils, if the tgd value at 90 ° C will not exceed 2.2% before pouring and 2.6% after pouring and the acid number is not more than 0.02 mg KOH / g, with the rest of the quality indicators in full compliance with the requirements of the table.
Table 25.3
Requirements for the quality of recovered and refined oils prepared for filling
into electrical equipment after repair1)
Oil quality index and test method standard number |
The maximum permissible value of the oil quality indicator |
Note |
||
intended for filling into electrical equipment |
after pouring into electric |
|||
1. Breakdown voltage according to GOST |
Electrical equipment: |
|||
6581-75, kV, not less2) |
up to 15 kV inclusive |
|||
up to 35 kV inclusive |
||||
from 60 to 150 kV inclusive |
||||
from 220 to 500 kV inclusive |
||||
2. Acid number according to GOST 5985-79, mg KOH / g oil, no more |
||||
Instrument transformers up to 220 kV inclusive |
||||
3. Flash point in a closed crucible, according to GOST 6356-75, ° С, not lower |
Power transformers up to 220 kV inclusive |
When using arctic oil (AGK) or oil for switches (MBT), the value of this |
||
the indicator is determined by the standard for the brand of oil according to table. 25.1 |
||||
Transformers with film or nitrogen protection, hermetically sealed instrument transformers |
It is allowed to determine this indicator by the Karl Fischer method or by the chromatographic method according to RD 34.43.107-95 |
|||
Power and instrument transformers without special oil protection |
||||
according to GOST 1547-842) (qualitatively) |
Electrical equipment, in the absence of requirements of manufacturers for the quantitative determination of this indicator |
Absence |
Absence |
|
Electrical equipment up to 220 kV inclusive |
Absence (11) |
Absence (12) |
||
RTM 34.70.653-83,%, no more (purity class according to GOST 17216-71, no more) |
Electrical equipment over 220 to 750 kV inclusive |
|||
6. The tangent of the angle of dielectric losses at 90 ° C according to GOST 6581-75,%, |
Power transformers up to 220 kV inclusive |
The oil sample is not subjected to additional processing |
||
Instrument transformers up to 220 kV inclusive |
||||
Power and measuring transformers St. 220 to 500 kV inclusive |
||||
Power and measuring transformers St. 500 to 750 kV inclusive |
||||
Electrical equipment of all types and voltage classes |
Absence |
Absence |
||
Power transformers up to 220 kV inclusive |
In arbitration control, the definition of this indicator |
|||
4-methylphenol or ionol), according to RD 34.43.105-89,% mass, not less |
Power and instrument transformers up to 750 kV inclusive |
should be carried out in accordance with IEC 666-79 or / and RD 34.43.208-95 |
||
9. Pour point according to GOST 20287-91, ° С, not higher |
Electrical equipment filled with arctic oil |
|||
Transformers with foil protection |
||||
11. Stability against oxidation according to GOST 981-753) |
Power and measuring transformers over 220 to 750 kV inclusive |
Process conditions: 130 ° С, 30 h, 50 ml / min О2 |
||
acid number of oxidized oil, mg KOH / g oil, no more |
||||
mass fraction of sediment,%, no more |
Absence |
|||
Electrical equipment: |
||||
73,%, not more |
up to 220 kV inclusive |
|||
St. 220 to 500 kV inclusive |
||||
St. 500 to 750 kV inclusive |
||||
_____________________
1) The use of regenerated and purified operating oils for filling high-voltage bushings after repair is not allowed, this electrical equipment is filled after repair with fresh oils that meet the requirements of table. 25.2.
2) In oil switches, it is allowed to use regenerated or purified operating oils, as well as their mixtures with fresh oils, if they meet the requirements of this table (paragraphs 1 and 4) and have an industrial cleanliness class of no more than 12 (GOST 17216-71).
3) If necessary, according to the decision of the technical manager of the enterprise, it is allowed to pour the regenerated and purified operational transformer oil into power and instrument transformers up to 500 kV inclusive, if the stability against oxidation corresponds to the norm for TKp oil (see table 25.1), and the remaining quality indicators will meet the requirements of this table.
Table 25.4
Requirements for the quality of operating oils
Oil quality index and number |
Oil quality index value |
Note |
||
test method standard |
bounding area of normal state |
maximum allowable |
||
1. Breakdown voltage according to GOST |
Electrical equipment: |
|||
6581-75, kV, not less |
up to 15 kV inclusive |
|||
up to 35 kV inclusive |
||||
from 60 to 150 kV inclusive |
||||
from 220 to 500 kV inclusive |
||||
2. Acid number according to GOST 5985-79, mg KOH / g oil, no more |
||||
3. Flash point in a closed crucible in accordance with GOST 6356-75, ° С, not lower |
Power and instrument transformers, leaking oil-filled bushings |
Decrease of more than 5 ° С in comparison with the previous analysis |
||
Transformers with film or nitrogen protection, hermetically sealed oil-filled bushings, hermetically sealed instrument transformers |
It is allowed to determine this indicator by the Karl Fischer method or chromatography |
|||
Power and instrument transformers without special oil protection, leaking oil-filled bushings |
physical method according to RD 34.43.107-95 |
|||
according to GOST 1547-84 (qualitatively) |
Electrical equipment, in the absence of requirements of manufacturers for the quantitative determination of this indicator |
Absence |
Absence |
|
GOST 6370-83,% (purity class according to GOST 17216-71, no more); |
Electrical equipment up to 220 kV inclusive |
Absence (13) |
Absence (13) |
|
RTM 34.70.653-83,%, no more (purity class according to GOST 17216-71, no more) |
Electrical equipment over 220 to 750 kV inclusive |
|||
6. Tangent of dielectric loss angle according to GOST 6581-75,%, not more, |
Power and measuring transformers, high-voltage bushings: |
The oil sample is not subjected to additional processing |
||
at a temperature of 70 ° C / 90 ° C |
110-150 kV inclusive |
Norm tgd at 70 ° С |
||
220-500 kV inclusive |
optional |
|||
Power transformers, sealed high-voltage bushings, sealed instrument transformers up to 750 kV inclusive |
||||
Leaky high-voltage bushings and instrument transformers up to 500 kV inclusive |
||||
Transformers without special oil protection, leaking oil-filled bushings over 110 kV |
||||
Power and measuring transformers, leaky high-voltage bushings, over 110 kV |
This indicator is determined according to RD 34.43.105-89 |
|||
Foil-protected transformers, sealed oil-filled bushings |
Determination by chromatographic method according to RD 34.43.107-95 is allowed |
|||
Transformers and bushings over 110 kV |
This indicator is determined by chromatographic methods according to RD 34.43.206-94 or |
|||
_________________
* Indicator 11 is recommended to be determined in case of detection in transformer oil significant quantitiesСО and СО2 by chromatographic analysis of dissolved gases, which indicate possible defects and processes of destruction of solid insulation.
(Modified edition, Amendment No. 1)
25.3.2 Extended transformer oil tests
The need to expand the scope of testing of oil quality indicators and (or) to increase the frequency of control is determined by the decision of the technical director of the power company.
25.3.3 Requirements for transformer oils topped up in electrical equipment
Transformer oils added to electrical equipment during its operation must meet the requirements of table. 25.4, column 3.
The volumetric weight of transformer oil is not a fixed nameplate value. It is clear that this oil, like any other liquid, will have a different volume when placed in different vessels. Therefore, let's talk about the characteristics of the passport, such as the volumetric weight of transformer oil.
Determination of volumetric weight
Let's start with the definition. The volumetric weight of oil is the ratio of its weight at a temperature of +20 ºС to the weight of water occupying the same volume, but already at a temperature of +4 ºС.
Indicators of the norm of the volumetric weight of oil for transformers
This indicator is not standardized. At a temperature of +20 ºС for transformer oil, it is 0.856-0.886. If you heat, then the value of the volumetric weight will decrease, and with cooling, on the contrary, it will increase.
Change rate
To determine the volumetric weight of oil at a temperature that differs from +20 ºС, it is necessary to subtract it when it rises, and when it decreases, add the coefficient of change in the volumetric weight for each degree. Typically, for electrical insulating oils, the numerical value of this indicator is 0.0007 per 1 ºС.
GOST
You can also use a special technique described in GOST-3900-47 to determine the volumetric weight. There is also a table in which corrections for temperature not equal to +20 ºС are placed.
Devices for determining the volumetric weight of transformer oil
In practice, the most in a simple way determining the volumetric weight is the use of a hydrometer (oil density meter) device. A portion of the test oil is collected in a glass cylinder, and then the hydrometer is placed there. The counting is carried out along the upper edge of the meniscus.
Influence of temperatures
If the oil temperature is changed by +100 ºС, for example, from -35 ºС to +65 ºС, then its volume will change by about 7%. Taking into account the fact that during operation the temperature can vary over a wider range, the volume of the expander must be selected at the level of 9-10% of the oil volume.
| Calculate, find out the volumetric weight: physical properties. | The quantities. | Number of kg in 1 liter, kg / liter. | For calculations, reference data from: | Now you can find out how much it weighs with a tool such as: | Measurement error. | - |
| How many kg is the weight of 1 liter of transformer oil - a liter can. | We use the reference data on density and specific gravity, calculating from the formula we obtain the volumetric weight. | 0.89 - 0.90 | Directory physical properties, GOST, TU. | Liter jar. | up to 5% | - |
Quite often, in practice, we are faced with situations when we need to find out what is the weight of 1 liter of transformer oil. Usually, such information is used to convert the mass to other volumes, for those containers, the displacement of which is known in advance: cans (0.5, 1, 2, 3 l), bottles (250 mm, 0.5 ml, 0.75, 1, 1.5, 2, 5 l), glasses (200 ml, 250 ml), canisters (5, 10, 15, 20, 25 l), flasks (0.25, 0.5, 0.75, 0.8, 1 l) buckets (3, 5, 7, 8, 10, 12, 15, 18, 20, 25, 30 l), flasks and cans (3, 5, 10, 22, 25, 30, 40, 45, 50, 51, 200 l), barrels (30, 50, 60, 65, 75, 127, 160, 200, 205, 227, 900 l), tanks, cylinders, tanks (0.8 m3, 25.2, 26, 28.9, 30.24, 32.68, 32.7, 38.5, 38.7, 40, 44.54, 44.8, 46 , 46.11, 46.86, 50, 54, 54.4, 54.07, 55.2, 61, 61.17, 62.39, 63.7, 65.2, 73, 73.1, 73.17, 75.5, 62.36, 88.6 m3, 99.2, 101.57, 140, 159, 161.5 m3). In principle, even pots and pots can be estimated by weight if you know how much one liter of transformer oil weighs. For household use and some independent work, the question can be asked differently when the question is not the weight of 1 liter of transformer oil, but how much a liter can (jar) weighs. Usually you are interested in how many grams or kilograms are in a liter can. Finding such data: how much it weighs on the Internet is not as easy as it seems. The fact is that the generally accepted format for submitting material in any reference books, tables, technical specifications and GOST boils down to bringing only the density and specific gravity of transformer oil. In this case, the indicated units of measurement are one m3, cubic meter, cubic meter or cubic meter. Less often 1 cm3. And we are interested in how much a liter volume weighs. Which leads to the need for additional conversion of cubic meters (m3) to liters. This is inconvenient, although it is possible to do the correct conversion of cubes into liters on your own. Using the ratio: 1 m3 = 1000 l. For the convenience of site visitors, we independently made recalculations and indicated how much one liter of transformer oil weighs in Table 1. Knowing the weight of 1 liter of transformer oil, you not only determine the mass liter cans, but you can easily calculate how much any other container weighs for which the displacement is known. At the same time, you need to understand the undesirability and impossibility of accurate estimates made on the basis of such recalculations for large containers with a significant volume of displacement. The fact is that with such calculation methods, a large error arises, which is acceptable only in the sense of an approximate estimate of the mass. Therefore, professionals use special tables that indicate how much, for example, a truck or rail tanker, a barrel weighs. On the other hand, for applied and domestic purposes, for home conditions, the calculation method based on the liter volume is quite suitable and can be applied in practice. In those cases when we need more accurate data, for example: during laboratory research, for examination, for debugging a production process, setting up equipment, and so on. The weight of 1 liter of transformer oil is best determined experimentally, through weighing on accurate scales, according to a special technique, and not use reference, theoretical, tabular average data on density and its specific gravity.
