Transformer oil is a petroleum-derived product. It is used as an electrical insulating material, a heat dissipating and arcing medium, and an environment that protects solid insulation from the ingress of air and moisture. As you can see, the list of tasks performed is quite wide, which puts forward certain requirements for the properties of transformer oils. In this article I would like to talk about what the viscosity of transformer oil is.
Among other properties electrical insulating oils, the viscosity is perhaps one of the most important. Fresh oil, which is just being poured into the transformer, should have the lowest possible viscosity. This will help improve heat dissipation from the windings.
A similar situation is observed in oil circuit breakers. Their oil must have high mobility and low viscosity in order to minimize the resistance to moving parts. Modern switches put forward new requirements for the viscosity of oils and the dependence of its increase on a decrease in temperature.
What is oil viscosity?
Viscosity is one of essential properties transformer oils, which is associated with its great influence on the heat transfer processes occurring in oil-filled equipment.
When performing engineering calculations, the concepts of specific, kinematic and dynamic viscosity are used. As in many cases, there is a trade-off when choosing oil for electrical equipment. The thing is that a material with a high viscosity has a good effect on electrical insulating properties, and low viscosity reduces the cooling capacity. Therefore, in practice, it is chosen the best option, which is able to ensure good performance of both the first and second functions.
Since the operating conditions of power transformers are quite difficult and can be characterized by elevated temperatures, it is worth considering the change in viscosity during heating. An increase in temperature leads to a decrease in viscosity and vice versa.
Usually in the reference literature you can find several values of the viscosity of the transformer oil indicated for a certain temperature. Using well-known mathematical methods (interpolation, extrapolation, etc.), it is easy to find the value of the viscosity at the temperature of interest, even if it is not indicated in the reference book. For example, the average value of kinematic viscosity for transformer oil is (28-30) ∙ 10 -6 m 2 / s.
Conditional and kinematic viscosity of transformer oil
A parameter such as conditional viscosity, is determined using a special device - an Engler viscometer, according to the method described in GOST 6558-52. In this case, one looks at the so-called water number of the viscometer: i.e. outflow of 200 cm3 of distilled water at 20 ºС. It should not be less than 50 and more than 52.
Kinematic viscosity determined using a capillary viscometer (Pinkevich viscometer), which has the form of a U-shaped tube. The measurement technique is set out in GOST 33-82.
In practice, when choosing the viscosity of oils, it is necessary to look for a compromise, since, on the one hand, its high value has a good effect on the electrical insulating properties, but worsens the cooling capacity and increases the resistance to moving parts of mechanisms. Low viscosity has the opposite effect.
As a rule, different grades of transformer oils have different viscosities. This indicator depends significantly on temperature.(if the oil is heated, then its viscosity decreases), therefore, in the reference literature, in most cases, several values of this indicator are indicated at different temperatures.
For example, for positive operating temperatures from 50 ºС to 90 ºС the viscosity of oils of various origins can differ by about two times. For various oils at a positive temperature, the temperature gradient of viscosity does not exceed 1 mm 2 / s per 1 ºС.
When negative temperatures viscosity different varieties oils can rise very unevenly. Judge for yourself: in the range -20 ºС… -30 ºС the temperature gradient of viscosity is 60-70, -30 ºС… -40 ºС - 90-370, -40 ºС… -50 ºС - 800-6000, and in the range -50 ºС … -60 ºС can reach 50,000 mm 2 / s at 1 ºС and higher.
If the change in the viscosity of transformer oils occurs in the region low temperatures, then in this case it is necessary to take into account such a phenomenon as anomaly viscosity. Also, a discount on high viscosity values should be made in the event that a powerful circulating-cooled transformer is commissioned. In such devices, the oil is exposed to low temperatures for a long time.
In devices such as oil circuit breakers or contactors for voltage regulation under load of transformers, performance is also directly dependent on viscosity.
Measuring the viscosity of transformer oils
Determination of the conditional viscosity of transformer oils is carried out using special devices - Engler viscometers. They consist of brass and metal vessels, a calibrated tube, stopper and indicator pins.
The viscosity of oil in Engler's degrees is the time required for the expiration of 200 milliliters of oil heated to a temperature of 50 ° C, divided by the time required for the expiration of the same volume of distilled water, but already at a temperature of 20 ° C.
To find the dynamic and kinematic viscosity, special empirical formulas are used that take into account the force acting on a solid ball in oil, its radius, speed of movement, radius and height of the vessel. The kinematic viscosity is obtained by dividing the known dynamic viscosity by the density of the transformer oil.
In addition to Engler's devices, other viscometers can also be used to measure the relative viscosity: rotary, ball, electrorotational, capillary and plastoviscometers.
To maintain the optimal numerical value of the viscosity of transformer oil throughout its entire service life, it is necessary to use special equipment. The thing is that during the operation of power transformers, a number of unfavorable factors act on oils: sunlight, high temperatures, air oxygen, mechanical impurities, etc. The combination of these factors leads to a deterioration in the operating parameters of oils and their deviation from the standardized values. First of all it comes about the breakdown voltage, acid number, dielectric loss tenge, flash point. Viscosity is no exception.
Therefore, in order to maintain all operational parameters of transformer oil at the level of standardized values, it is necessary to perform certain measures: cleaning, drying and regeneration.
Company GlobeСore offers a wide range of equipment designed to work with transformer oils. Application of technologies GlobeCore allows not only to maintain the parameters of transformer oils at the proper level, but also to restore them in case of deterioration.
Plants for purification, drying and regeneration of transformer oils from the company GlobeCore Is an energy efficient and environmentally friendly solution to the problem of maintaining and deteriorating the quality characteristics of transformer oils! To ensure the reliable operation of your oil-filled equipment, it is quite simple to contact the specialists of our company and with their help to choose the installation of the required performance.
Oil switches and reactor equipment. In reactor equipment, they serve as a medium for extinguishing the arc.
Requirements
The electrical insulating qualities possessed by transformer oils depend on the dielectric loss. The dielectric strength of transformer oils can be greatly reduced by water and a variety of fibers. Therefore, these substances should not be in its composition. An important parameter is the pour point. To maintain mobility in the cold, this indicator for the working fluid should be - 45 ° C and below. In order for heat to be removed with maximum efficiency, the liquid must have a minimum viscosity at the flash point, which for different brands should not be less than 150-95 ° C.
The most important parameter possessed by transformer oils is oxidation stability, or the ability to maintain constant performance during operation for a long time. Most of The used grades of transformer oils are stabilized by such additives against oxidation as ionol or agidol-1. Their action is based on the ability to react with active peroxide radicals formed during the chain reaction of hydrocarbon oxidation. Ionol-stabilized transformer fluids most often oxidize with a pronounced induction period.
In the initial stage, oils that remain susceptible to additives are oxidized very slowly, since all oxidation foci that appear in the oil are suppressed by the inhibitor. When the additive is depleted, the oxidation rate approaches that at which the original oil is oxidized. The longer the induction cycle of oxidation, the more effective the additive is. The effect of the additive is determined by the hydrocarbon composition of the transformer oil and impurities of other non-hydrocarbon compounds that enhance oil oxidation (these are nitrogenous bases, naphthenic acids, oxygen-containing oxidation products).
Transformer oils are designed to insulate parts and assemblies of power transformers that are under the influence of voltage, to remove heat from parts that are heated during their operation, and to protect the insulation from moisture.
Options
Transformer oil, the characteristics of which are completely determined by its content, in turn, largely depends on the chemical composition of the feedstock and the cleaning methods used. In the used brands of transformer oils there are differences in chemical composition and performance characteristics, and they are designed for different purposes. New oil-immersed transformers only require completely fresh oils that have not been used before. Each batch of liquid that is used for filling must have a manufacturer's certificate. Before pouring transformer oil coming from an oil refinery into a power transformer, it must be cleaned from moisture, gases and mechanical impurities.
Moisture can be contained in transformer oil in different form... It can be sediment, emulsion and solution. Before filling, the transformer oil is subjected to complete cleaning from moisture contained in the oil in the state of emulsion and in the form of sludge. As a solution, moisture does not significantly affect the tangent of the loss angle and the dielectric strength, however, it promotes an increase in the oxidizability of the liquid for transformers and a deterioration in the stability of its composition. In this regard, obtaining values of the breakdown voltage and the tangent of the loss angle that meet the standards cannot serve as a criterion for complete cleaning.
An important parameter is the density of the transformer oil. You need to know it in order to calculate the mass of the product received at the enterprise. The density of transformer oil allows you to find out its hydrocarbon composition.
At a pressure equal to atmospheric, in the dissolved state in the oil of the transformer there can be up to 10% air. If power transformers are equipped with film and nitrogen protection, then before filling the special oil must be degassed in order to achieve a residual gas content not exceeding 0.1% by weight.
After cleaning is done, there should be no mechanical impurities in the oil.
Measurement of oil parameters
The parameters of oils are checked by analyzing their electrical insulating and physicochemical characteristics:
- electrical strength;
- loss tangent;
- moisture content measurement;
- measuring the gas content in oil by means of an absorptiometer consists in determining the degree of change in the residual pressure in a certain container after samples of the test liquid have been poured into it;
- measurement of the quantitative composition of mechanical impurities by passing a sample dissolved in gasoline through an ash-free paper filter.
The method for determining the moisture content of oil is based on the fact that hydrogen is released during the reaction of moisture in the oil with oxygen hydride.
Transformer oil testing
Before putting the transformers into operation, the transformer oil is tested.
For transformer equipment, all rated voltages are tested for oil from the on-load tap-changer tank in full accordance with the manufacturer's manual. Oil for equipment with power up to 630 kVA, which is installed in electrical networks, it is allowed not to be tested.
Transformer oil is tested by customers in a certified laboratory, which is certified for the right to test it.
Centrifugation
This method of processing transformer oil consists in removing moisture and suspended particles by centrifugal forces. This removes only the moisture that is in the form of an emulsion and the particles in the solid state. The specific gravity of particles during centrifugation must be greater than that of the transformer oil being processed. This method predominantly purifies the liquid for power transformers with voltages up to 35 kV, or prepares it.
Filtration
The method consists in passing the oil through porous-type partitions, which retain all impurities contained in it.
Adsorption treatment
The method of purifying transformer oil by means of adsorption is based on the absorption of water and other impurities by various adsorbents. In their capacity, synthetic zeolites are used, which have a high absorption capacity, especially in relation to water particles. Purification of transformer oil with zeolites makes it possible to remove moisture from its composition, which is in the state of solution.
Vacuum treatment
The basic element of the cleaning method is the degasser. Crude butter first it is heated to a temperature of 50-60 ° C. After that, oil is sprayed in the degasser at its first stage. Further, it flows down in a thin stream along the surface of the Raschig rings. In this case, the first stage is evacuated by means of a vacuum pump. The released water and gas vapors are pumped out through an air filter and a zeolite cartridge. From the tank of the first stage degasser, the oil flows by gravity into the second stage, where it is finally dried and degassed. At the final stage, the transformer oil passes through a fine filter and is fed into the transformer.
Waste oil
The used transformer oil is recovered in serial oil recovery plants using silica gel.
GK transformer oil
The technical liquid received the indicated marking on the basis of the method of its production. Transformer oil GK is produced using hydrocracking technology. Paraffinic sulphurous oils are used as raw materials for its manufacture. This type of oil has high insulating properties and is recommended for use in a variety of high-voltage equipment. Transformer oil GK contains an ionol additive and has the best antioxidant properties.
Under steady-state conditions and natural cooling of the transformer, the oil temperature in each horizontal plane remains unchanged (Fig. 8-1).
Rice. 8-1. Oil temperature along the height of the transformer tank [L. 8-1].
It should be noted that only in the boundary layers of oil (about 3 mm thick), directly washing the surface of the coils and the tank, temperature fluctuations occur. In order to ensure a sufficient life span of the transformer insulation, it is important to reduce the temperature faster, that is, to more intensively remove heat from the heated wire [L. 8-1].
The value of the heat transfer coefficient, among other variables, is determined physical properties coolant: density, heat capacity, thermal conductivity and viscosity [L. 8-2, 8-3].
The density of commercial transformer oils usually varies within fairly narrow limits: 0.860-0.900.
With enough for many practical tasks the accuracy of the temperature dependence of the density is determined approximately by the equation
https://pandia.ru/text/80/153/images/image291.gif "width =" 26 "height =" 24 "> - density at a temperature of 20 ° С; t - temperature for which the density is calculated; α - temperature correction of density by 1 ° С (Table 8-1).
Table 8-1. Average temperature corrections for the density of petroleum oils [L. 8-4].
Heat capacity and thermal conductivity transformer oils are temperature dependent and related to the density of the oil.
In fig. 8-2 and 8-3 show the corresponding ratios borrowed from [L. 8-5].
Rice. 8-2. The thermal conductivity coefficient of transformer oils of various densities depending on temperature [L. 8-5].
To determine the thermal conductivity coefficient of transformer oils in the temperature range from 0 to + 120 ° C, you can use the nomograms [L. 8-6]; if necessary, this parameter is determined experimentally [L. 8-7].
Rice. 8-3. Specific heat transformer oils of different density depending on temperature [Л..jpg "width =" 347 "height =" 274 ">
Rice. 8-4. Practical coefficients of heat transfer of heat exchangers, depending on the flow rate and viscosity of the coolant [L. 8-9]. 1 - flow rate 1.2 m / s; 2 - the same 0.3 m / s.
Viscosity pure hydrocarbons varies widely depending on the size and structure of the molecule. Distinguish the dynamic viscosity η, usually expressed in centipoise (1 cs 10-3 kg / ms), which is used to express the absolute forces acting between liquid layers and kinematic viscosity. The latter is the ratio of the dynamic viscosity of the liquid at a given temperature to its density at the same temperature: νк = η / ρ. The use of νk is very convenient when studying the motion of viscous fluids.
An increase in the molecular weight of paraffinic hydrocarbons leads to an increase in viscosity. For aromatic hydrocarbons, with an increase in the length of the side chain, the viscosity increases approximately according to the parabolic law (relative to the number of carbon atoms in the side chains) (Fig. 8-5).
Rice. 8-5. The relationship between viscosity and side chain length for alkylbenzenes (dashed line) and β-alkylnaphthalenes (solid line) [L. 8-10].
The presence of cycles in hydrocarbon molecules leads to an increase in their viscosity. How more complex structure rings, the more elm-guest at a given molecular weight. The viscosity of alkyl-substituted aromatic hydrocarbons increases with the number of side chains. [L. 8-10. 8-13].
A functional relationship has been established between the parameters that determine the viscosity properties of the oil and its hydrocarbon composition, which is experimentally confirmed by the example a large number oil samples. It is indicated that using such a relationship, it is possible, based on the data of the structural group analysis of the oil, to calculate the values of its viscosity at any temperature exceeding the pour point of the oil [L. 8-14].
Studies carried out with various oil distillates of domestic oils [L. 8-15], show that the best viscosity-temperature characteristics are possessed by oil fractions containing naphthenic and paraffinic hydrocarbons. Removal of the paraffin portion from such fractions usually leads to an increase in the level of viscosity and an improvement in the low temperature properties of oils.
The aromatic fraction of the oil is characterized by an improvement in the viscosity-temperature properties with an increase in the content of hydrocarbons with big amount carbon atoms in chains.
The data presented indicate that the structure of hydrocarbons determines not only the absolute value of their viscosity, but also the nature of the temperature dependence of the viscosity. This characteristic has great importance when using oils in transformers, devices for switching under load, as well as in oil circuit breakers.
It is very important that at low temperatures the viscosity of the transformer oil is as low as possible; in other words, the curve characterizing the temperature dependence of the oil viscosity should be fairly flat. Otherwise, with a high viscosity of oil in a cooled transformer, it will be difficult to remove heat from its windings in the initial period after switching on, which will lead to their overheating. In switching devices of transformers and oil switches, an increase in oil viscosity creates an obstacle to the movement of moving parts of the equipment, which entails a malfunction. In this regard, in some standards for transformer oil viscosity is normalized at a temperature of -30 ° C. The change in the viscosity of transformer oil depending on temperature is well described by the Walter equation [L. 8-16].
where ν - kinematic viscosity, cst; T - temperature, ° K; p and m are constants.
On the basis of this formula, a special nomogram is built, with the help of which, knowing the viscosity of the oil at two specific temperatures, it is possible to approximately establish its viscosity at any given temperature [L. 8-17]. In the region of high viscosity values (i.e., at low negative temperatures), the nomogram can be used only as long as the oil remains a Newtonian fluid and there is no viscosity anomaly. At temperatures below minus 20 ° C, deviations of the viscosity values from the straight line on the nomogram are sometimes observed. For most transformer oils, the limit of use of the nomogram corresponds to a viscosity of approximately 1,000-1,500 cst. Another disadvantage of nomograms of this kind is that double logarithm leads to a smoothing of the viscosity-temperature dependence and the slopes of the corresponding straight lines for different oils differ little.
In some cases, use the so-called F scale [L. 8-18]. When constructing this scale, the temperature is plotted on the abscissa axis in a uniform scale. A viscosity scale is applied to the ordinate axis in such a way that for a given transformer oil, taken as a standard, the temperature dependence of viscosity is characterized by a straight line. Then, for other transformer oils, the dependence of viscosity on temperature will also be depicted as a straight line. This allows interpolation and extrapolation of the viscosity values of any transformer oil at two experimental points (Fig. 8-6).
Rice. 8-6. F scale for interpolation and extrapolation of the viscosity of transformer oils at different temperatures using two experimental points; When constructing the scale, the experimental dependence v = f (t) for commercial oil from Baku oils was used as a standard.
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.
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.
