Hydrophobic organosilicic compound for electric insulating structures

FIELD: electricity.

SUBSTANCE: hydrophobic organosilicic compound for electric insulating structures is made on the basis of organosilicic compositions of cold hardening. The compound contains silicon low-molecular rubber, a filler, and also a hardener or a catalyst. The compound in vulcanised condition is characterised by the value of the edge angle of wetting from 60° to 179°, tracking erosion resistance at duration of tests making at least 500 hours at working voltages of 6-750 kV, and also with arc resistance characterised with arc current value of at least 100 mA with duration of effect of at least 600 s.

EFFECT: increased reliability and higher service life of a hydrophobic electric insulating coating on the basis of a compound, which is provided by composition and ratio of compound components and specified operating properties of a coating in vulcanised condition.

5 cl, 14 dwg

 

The invention relates to hydrophobic silicon-based compounds (hereinafter - KOK), intended for application to the insulating structure, for example, high voltage insulators, and can be used to enhance blagorazumnogo voltage and increasing the electric strength of external insulation, working in conditions of pollution.

Known electrically insulating hydrophobic compound in the form of silicone pastes applied to the surface of the insulating structures, and used to improve blagorazumnyi voltage high-voltage insulation [Kim Yong Gift Pheonomenal. Operating experience of the silicone coating of cold hardening on the substations of the power systems of Ukraine // Electrical networks and systems. - 2006. No. 3. - P.32-35].

The disadvantage of this compound is that in the process of operation hydrophobic paste layer is saturated with pollutants and loses its hydrophobic properties, which results in low values withstand operating voltages, as well as the need for periodic replacement of the insulating structure.

How similar is selected insulating hydrophobic silicone elastomer that forms on the surface of the solid insulator protective film [Ravi S.G. RTV Silicone Rubber Coatings for Ceramic Insulators: Present Knowledge nd Future Requirements // 2001 Insulator World Congress, Shanghai, China, November 18-21 - Shanghai. - 2001. - P.361-368].

The lack of compound analog is not a high performance properties and lifetime of damage on the basis of the hydrophobic coating, which results in low values withstand operating voltages, as well as the need for periodic replacement of the insulating structure.

As the closest analogue (prototype) of the selected insulating hydrophobic organosilicon compound (COCS) cold hardening with a solid filler in the form of titanium dioxide and a hydroxide of aluminum, and with a liquid filler in the form of low molecular weight silicone fluids.

Thus the weight ratio between the compound and the low molecular weight silicone fluid is 1:(0,015-0,02), and the weight ratio between the compound and the hydrate of aluminum oxide is 1:(0,07-0,1) [Method of increasing blagorazumnogo high-voltage isolation. Patent UA №77628. IASC (2006) H01B 17/50 (2006.01) H01B 19/00, publ. 15.12.2006, bull. No. 12].

The disadvantages of the composition closest analogue are not high maintenance (electrical insulating) properties and lifetime of damage based hydrophobic coating (SE) due to the lack of optimal composition and ratio of components of the compound, the consequences of which are not high enough the value withstand operating voltages, as well as the need for periodic replacement of the insulating structure.

An object of the invention is to improve the reliability and increase the lifetime of the hydrophobic insulating coatings on the basis of the compound by establishing the optimal composition and ratio of the components of this compound, as well as its performance, in particular, insulating, properties in volcanoserver.com state, which will also lead to higher blagorazumnyi voltage high-voltage insulation with a hydrophobic coating on its basis throughout a long life of high-voltage insulation.

The technical problem is solved in that the hydrophobic silicone compound for insulating constructions based on one - or both supplied in two packages of organosilicon compositions of cold hardening, which contains low-molecular silicone rubber, a filler and a hardener or catalyst, what is new is that the compound in volcanoserver.com condition characterized by the value of the wetting angle of 60° to 179°, tregimeerotike resistance when the duration of the testing component of at least 500 hours at operating voltages 6-750 kV, as well as arcing, characterized by the value of the arc current is not less than 100 mA p and duration of exposure not less than 600 S.

The compound in devulcanization condition characterized viability at temperatures from 15°C to 35°C within 15-60 min, and volcanoserver.com the condition is characterized by the conditional bursting tensile strength not less than 0.55 MPa, elongation at break not less than 100%, specific volume electric resistance ρνnot less than 3,0×1014Ohm×cm, the specific surface electric resistance ρsnot less than 1.0×1015Ω, the tangent of dielectric loss angle tgδ at frequency 50 Hz no more than 0,008, electrical strength in distilled water of at least 10 kV/mm, and the strength of bonding with the metal when the Flack is not less than 0.60 N/m

The compound in volcanoserver.com condition is characterized by life, constituting not less than 10 years, when operating in conditions of temperatures from -60°C to + 65°C.

Compound as a low-molecular silicone rubber contains rubber stamps SCTN, as filler it contains as a solid filler in the form of a hydrate of aluminum oxide and carbon black acetylene and liquid filler in the form of low molecular weight silicone fluids brand 119-215, and as a hardener compound contains methyltriacetoxysilane.

The compound contains a 100.0 parts by weight of rubber of low molecular weight silicone fluid in to the number (1,25-2,5) parts by weight, the hydrate of aluminum oxide in the amount of (5-15,0) parts by weight, acetylene soot in the amount of (0,5-2,5) parts by weight and the curing agent in the amount of (2,5-6,5) parts by weight of

These conditions constitute the essence of the invention.

The causal connection between the set of essential features of the invention and achievable technical result is the following.

The various States of the environment on the outer surface of the high-voltage insulation layers are formed of different pollution intensity. Settling out of the air particles build up over time on the surface of the insulator layer pollution. This layer when moisture atmospheric moisture increases its conductivity, which further reduces the insulating ability of the insulation structures. This creates conditions for flashover of insulators not only when the overvoltage, but under normal operational mode.

Therefore, to improve the reliability of high-voltage insulation in areas with a high degree of air pollution (be) is an urgent task of strengthening the outer insulation to ensure the highest bit of stress in adverse conditions. The solution to this problem is the use of effective silicone hydrophobic coatings based on KOC.

It was found that h is about silicone hydrophobic coating is most appropriate to apply in areas where pollution in the atmosphere are mainly gaseous and fog-like components. At the same time, the main technical problem is the choice of the optimal proportions of the components of the applied hydrophobic insulating composition based on KOC. This, in turn, should provide the highest possible bit values of the stresses in the work of such insulating structures in the contamination of various degrees and moisture.

In areas with large be the outer insulation is often subjected to surface discharges. On the basis of numerous observations and measurements established that the majority of surface discharges has throws currents of the order of 10-30 mA, and under certain conditions 100 mA or more. Therefore, the arcing hydrophobic coatings based on KOK is one of the main reliability criteria for areas with high be.

Tests arcing was carried out according to the method of conducting bridge in exposure low high arc voltage in accordance with GOST 10345.1-78. This method allows you to give a rapid assessment of the sustainability of the dielectric material to the exposed surface discharges.

Hydrophobic coating, designed for testing was applied to pre-fat surface m is a metallic samples. After coating, the samples were aged prior to testing at least 7 days to ensure complete curing of the coating over the entire thickness. Before testing the samples in the locations of future arc (between the electrodes) using a magnetic thickness gauge can measure coating thickness. The test sample was placed on a ceramic spring-loaded stand ensures a snug fit of the electrodes to the test surface, and then applied a high voltage. The duration of arcing was recorded using a stopwatch.

The test facility has provided an initial current of 10 mA and a subsequent increase in steps of 10 mA each, up to 100 mA. The duration of exposure at each stage - 60 C.

Since the surface discharges occur in the first place, after wetting the surface before testing the specimens with hydrophobic coatings of different compositions were moistened in distilled water for 24 hours. The tests were stopped or when burning and electrical breakdown coverage (arc extinction), or after the sample was kept 60 with exposure to arc force current 100 mA (total test time was 600 s).

Visual observation revealed some regularities of fracture coatings by electric arc. When the small thickness of the coating layer (0.1 is m the coatings with the addition of conductive fillers) in the first seconds is an electrical breakdown and, as a consequence, the extinction of the arc, accompanied by a sharp increase in current at the control device more than 2 times.

When a sufficiently large thickness of the coating at a current of 10 mA for most of the samples arc burning in the air along the surface without causing any damage, as shown in figure 1 (arc when current 10 mA) and figure 2 (the state of the coating surface after 1 min its impact in current of 10 mA).

With increasing current up to 20 mA or more on the surface of any of the tested coatings were formed "track path", and the current value in the control device was increased by 2-4 mA. But the arc continued to burn, therefore, the coating remained good electrical insulating properties (an example is shown in figure 3, which shows the arc when current 50 mA) and figure 4, which shows the surface condition of the coating exposed to the current 50 mA after the power is turned off).

Prolonged arcing occurs quite significant heat, resulting in thermal degradation of the coating and, consequently, its breakdown and extinction of the arc, as shown in figure 5 (combustion products of degradation of the coating in the channel arc before its extinction) and figure 6 (showing the surface appearance of the coating after the extinction of the combustion products of degradation of the coating in the channel arc).

When inspecting the samples, performed last the tension and remove the charred surface layer, it was observed that if the arc is not extinguished, then in place of the "track" coating maintains its integrity, but with traces of destruction. Accordingly, we can distinguish two main stages in the destruction of coverage arc:

the appearance of the track in the form of damage (charring) only the surface layer of the coating (see Fig.7), this arc is not extinguished;

- destruction - burnout cover more than 50% of the thickness, the softening of the remaining layer (see Fig) and its arc when the arc is extinguished.

Definition of durastanti homogeneous coatings on the basis of the developed COCS containing acetylene soot (from 4-5% or more) and iron oxide (from 20-30% and more) on metal samples is impossible due to insufficient data for test electric strength (breakdown in the first seconds when the coating thickness 0.5 mm). In this regard, for compositions with addition of 0.5 to 2.5% carbon black acetylene and 5-15% of hydrate of alumina in the analysis of the results counted values obtained on samples with a thickness of from 0.25 to 0.5 mm.

Analysis of the results did not reveal a clear relationship between coating thickness and the time of its destruction under the action of an electric arc. On the basis of the obtained results we can draw the following conclusions:

1. When used as fillers hydrate of aluminum oxide is achieved by the greater increase in durastanti, and with the increase of its content in the composition of the arcing coatings on the basis of COCS increases.

2. The nature of the curves of the probability of burning coatings without fillers, (0,5-2,5)% acetylene carbon black and (1,25-2,5)% low molecular weight silicone fluids brand 119-215 very close, especially in the first stages of testing. Therefore, when introduced into the composition of these components without exceeding the above-mentioned concentrations of the arcing coverage will not decrease.

3. The arcing coating is markedly reduced when increasing the amount of low molecular weight silicone fluids brand 119-215 (3% or more).

According to the developed technical solutions, the compound in volcanoserver.com condition characterized tregimeerotike resistance when the duration of the test component is not less than 500 hours. This insulator is considered to have passed the test if after testing, the test chamber is not marked critical electrical damage. Because of this distinctive feature, which corallines with arcing (see Fig.9), should be considered separately.

Tracking is the process of gradual formation of conductive carbon tracks on the surface of the external insulation of high voltage equipment due to the combined effects of voltage, humidity and pollution is rd. The resistance of insulating materials to treking-erosion damage is measured by the class tracking resistance of materials.

There are two main ways to prevent the effects of training in the study of high-voltage insulating structure: 1) introduction of structural changes; 2) the use of insulating composite materials having resistance to tracking.

Implementation option the first way is to increase the path lengths of the leakage currents and, consequently, decrease the chances of education for the insulation of electrical discharges, leading to the formation of conductive tracks and breakdowns. The increase in the overall length cutting high-voltage insulating structure, which increases the distance between bare metal parts of different potentials, is one of the special constructive measures.

However, this approach is not always convenient and practical, as with increasing voltage class requires a fairly significant increase in the length of the insulating structure. The requirements of GOST 9920-89 to the working conditions of isolation and Regulations for electrical installation (REI) has multiple degrees be. For each of the degrees of pollution and various stress network determined the minimum length of the path of leakage current.

The decision is relevant role in the occurrence or absence of tracking play the materials themselves, used as insulation in high voltage outdoor installations. Not all materials are equally able to resist the phenomenon of tracking. Materials such as mica, porcelain and glass have high tracking resistance and, in a sense, are the standards. For this reason, glass and ceramics have been traditionally used for the production of high-voltage insulators.

With the development of the field of polymer composite materials and modern technology came the ability to create polymers having resistance to tracking. After conducting a series of experiments, we developed a special recipe antitrichomonal based material KOK, meet all the necessary requirements tracking resistance when the duration of the test component is not less than 500 hours, the rationale dielectric properties and composition of which is as follows.

Developed compound in volcanoserver.com condition characterized by the value of the wetting angle of α≥60° (see figure 10) and up to 179° (see 11). This option, which is most characteristic of hydrophobicity of the coating based on KOC, is primarily determined by the optimum composition of the COC.

The above distinctive feature can also qualitatively illustrate using figure 10-13. Pokemonemeraldlover measuring the wetting angle vulcanized original coatings on the basis KOK developed composition, were also carried out measurements of the contact angle of the surface and on samples of the same composition after a certain time of exposure to corona discharge, which amounted to 1 min, 2 min, 5 min, 10 min, 20 min, 30 min, 60 min and 120 minutes

The wettability of the surface of the coating after 10 min exposure to corona discharge shown in Fig, and after 60 min exposure to corona discharge shown in Fig (Fig and pig right drop on the surface is a control and is outside the area of impact). In the result, it was found that complete loss of hydrophobicity (α≈0°) on the entire surface, exposed to the crown (see Fig), comes after 10 min exposure to corona discharge.

When more prolonged exposure (60 min) values and gradually began to increase (see Fig). The best scores were obtained for the samples, which was introduced low molecular weight silicone fluid 119-215 and increased to (0,5-2,5) parts by weight, the amount of soot. This confirms the assumption that the recovery of hydrophobicity is associated with the diffusion of low molecular weight organosilicon compounds of the coating layer to the surface, and with the ability of carbon atoms To "bind" the active atoms of oxygen (ozone).

It is known that odnoupakovochnye compositions consist typically of polymer silanolate groups and taken in excess with respect to silanol groups methyltriacetoxysilane, which is well soluble in the polymer. This pre-prepared in the absence of water, the mixture is relatively stable in dry environments, and the process of structuring it occurs only under the influence of moisture in the air. That is, odnoupakovochnye hydrophobic composition can be used only on air for relatively thin coatings.

The disadvantages of such compositions include the inability to apply them in a confined space, in systems with limited access of air, to obtain a thick-walled products, as well as the allocation during curing carboxylic acid.

In the process of curing compositions formed film of cross-linked polymer, which hinders the diffusion of moisture air in the polymer mass, which affects the characteristics of the cured material. Dilution of odnoupakovochnye compositions solvents allows you to adjust the viscosity of the mixture, to slow down the polymerization in its entirety and get on the surface of insulators method of spraying a uniform coating of the desired thickness.

As the hydrophobicity of the outer insulation is in most cases carried out at existing facilities, i.e. in the field, the process of preparing a hydrophobic composition should be as simple as possible, and at the same time to provide with sufficient accuracy the ratio of the components (i.e. optimal the activity of the composition is determined by examining the optimality of the resulting operational properties utverzhdenii composition).

Studies have shown that the introduction of the KOK any component (substance) to improve one of the characteristics of the obtained polymer coating may deteriorate the performance of his other characteristics. In this regard, the optimization of the composition of the COC is a complex task, the complexity of which depends on the number of components included in the coating composition. She is the definition of the parameter optimization and affecting factors, the choice of model and experiment plan (laboratory testing), testing, analysis of results and decision making.

Parameter optimization should be universal and effective from the point of view of the description of the final result, to be a quantitative value, which has a physical meaning and should quite easily be measured or calculated.

The main properties of polymer coatings on the basis of insulating KOK, designed to restore or enhance blagorazumnyi characteristics of the outer insulation is its hydrophobicity. Hydrophobic properties of the vulcanized coating directly characterized by the value of the wetting angle of the surface α. However, a single measurement of α characterizes the hydrophobicity at small surface area, so the definition pregnen the th hydrophobicity of the whole object rather time-consuming task. However, studies have shown that hydrophobicity is directly related to the change in the wetting of the surface coverage of a number of physical (electrical insulating) properties.

When wetting the actual insulation constructions (insulators) coated depending on the hydrophobicity of the past (and still in operation and pollution) reduced surface resistivity ρsand increases the leakage current Iut. In addition, it is known that for the detection of defects in the insulation (dielectric materials) in some cases, using the measurement of the tangent of dielectric loss angle tgδ.

Siloxane coatings of cold hardening can be in the form of a layer of polymer material, within which there are many air pockets, formed by evaporation of the solvent. The volume of these inclusions are much less than the volume of polymeric material. When humidification portion inclusions near the surface are filled with water.

Since the distribution and orientation of pores and voids in the floor, filled with moisture can greatly fluctuate under the influence of such factors as the mode of coating application, environmental conditions, etc. when the same amount of water uptake values of dielectric permittivity s samples of the same is of a material can vary considerably. In addition, changes in s samples with moisture less significant than tgδ, and for their determination requires accurate measurement of the coating thickness, which imposes special requirements to measuring instruments and quality samples.

Thus, to ensure the effective conduct of operations in the field KOK designed for hydrophobic coatings of cold hardening, should be primarily resistant to the possible ingress of impurities and possess vitality, providing work in a wide range of temperatures. Therefore, we can conclude that the best basis for applying silicone hydrophobic coating of cold hardening, in spite of the limitations, will still odnoupakovochnye KOK.

Well-known currently, compounds of this type include "Sylgard" (USA), KLT-30A (Russia), RPC-102 (Ukraine). The dielectric characteristics of the sample coatings (solid polymer films)obtained by curing these compounds are shown in table 1.

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Table 1
Dielectric characteristics of SE derived from single-component compounds of cold hardening
CompositionThe specific volume resistance ρν, Ohm×cmSurface resistivity ρsOhmsThe tangent of dielectric loss tgδThe relative dielectric permittivity, ε
"Sylgard"2,03×1014of 1.2×10150,0029is 3.08
KLT-30A3,03×10141,7×10150,00282,38
RPC 1024,63×1014of 1.9×10150,00201,88

Since the optimized object is a hydrophobic silicon containing coating of cold hardening, the main factors influencing the process of its formation and define its properties, are components that are included in the COC, and their number. Select the desired components was due to both their advantages and their disadvantages from the point of view of electrical properties and processability get the th KOK (see table 2).

From the above table it follows that one of these components for further consideration as optimizing factors it is advisable to investigate the following:

1. The hydrate of aluminum oxide (the main purpose to increase durastanti).

2. Iron oxide (II) (increase durastanti and colonoscopist).

3. Low molecular weight silicone fluid 119-215 (increase the speed of recovery of hydrophobicity after exposure to corona, reduced water absorption).

4. Carbon black is acetylene (staining of the coating, increasing colonoscopist).

The main purpose of the hydrate of aluminum oxide and iron oxide (II) in the composition is the same. The properties (primarily dielectric) is influenced by environmental conditions during coating (temperature and relative humidity), the viscosity of the composition and the amount applied per unit area (indicates the thickness of the coating).

In accordance with the decision on the metal samples (5 specimens of 100 mm diameter for measuring dielectric properties and water absorption, and 5 rectangular samples of 70 mm×35 mm to determine durastanti) spray application method were applied following water composition based on KOK (here the numbers in parentheses indicate the % content of the W ingredient for COCS):

Table 2
Advantages and disadvantages of the components introduced into the composition of hydrophobic KOK
fillerdignitydisadvantages
Carbon black (C)Getting painted coating, the formation of additional bonds (increasing the mechanical strength and colonoscopist)Reduced arcing and ρνincrease tgδ and ε.
Titanium dioxide (TiO2)Increases resistance to arcingComplicated preparation process of the composition. With equal dielectric characteristics to increase durastanti much lower than the hydrate of aluminum oxide.
Iron oxide (II) (FeO)Increases resistance to arcing. Getting painted coating, the formation of additional bonds (increasing the mechanical strength and colonoscopist)Decreasing ρνincrease tgδ and ε. With equal dielectric characteristics uvelichivayuschaya inferior to the hydrate of aluminum oxide.
Aluminum oxide (Al2O3)Increases resistance to arcing.Decreasing ρνincrease tgδ and ε.
The hydrate of aluminum oxide Alg(Al2O3×3H2O)Increases resistance to arcing. In comparison with aluminum oxide at equal durastanti coating has better dielectric characteristics.Decreasing ρνincrease tgδ and ε.
Low molecular weight silicone fluid 119-215 (K)Increases the rate of recovery of hydrophobicity after exposure to corona discharge. Reduced water absorption. Improved dielectric characteristics.Reduced arcing. When the content is 10% or more of the compound significantly slows down the polymerization of the coating.
Silicone fluid PMS-100Reduced water absorption. Improved dielectric characteristics. Possible partial replacement used when applying easy-flammable liquids (solvents)Reduced arcing (especially when the content is more than 5% by weight to the of mpanda). Inferior liquid 119-215 speed recovery of hydrophobicity after exposure to corona discharge.

composition No. 1: KOK (100)+FeO(26)+K(l)+s(0);

composition No. 2: KOK (100)+Alr(5)+(1,25)+C(1);

composition No. 3: KOK (100)+FeO(14)+K(1)+C(4);

composition No. 4: KOK (100)+Alr(3)+K(1,5)+C(2,5);

composition No. 5: KOK (100)+FeO(26)+K(3,5)+C(3);

composition No. 6: KOK (100)+Alr(7)+(5)+C(4);

composition No. 7: KOK (100)+FeO(14)+(3,0)+(1);

composition No. 8: KOK (100)+Alr(20)+(5)+(5);

composition No. 9: KOK (100)+Alr(11)+(2,0)+s(0.5);

composition No. 10: KOK (100)+Alr(10)+K(2,5)+C(3,5);

composition No. 11: KOK (100)+Alr(18)+(4)+(5);

composition No. 12 (control): KOK (100)+C(1).

After determining the thickness of coatings obtained on all samples was carried out rejection: if the average thickness was less than 150 μm or values of the confidence interval were more than 10% of the average value, then the sample was excluded from testing. The averaged characteristics of the hydrophobic coating compositions No. 1 to No. 8 are shown in table 3.

Table 3
The averaged characteristics of the hydrophobic coating compositions No. 1 to No. 8
compositioncharacteristics in the initial stateafter 24 h of hydration in disti the profiled water prirode
the Δtgδ
dagosto
bone t, c
ρνOhm×cmtgδερν, Ohm×cmtgδε
No. 14.26 deaths×10140,00453,19to 2.29×10140,01063,250,0061-
No. 24,47×10140,00732,532,62×10140,01812,770,0108137,2
No. 33,55×10140,00593,09to 2.41×10140,01133,200,0052to 83.5
No. 410,5×10140,0084 2,556,24×10140,02272,990,0143197,5
No. 510,14×10140,00563,03of 5.06×10140,01113,210,005512,5
No. 63,50×10140,00852,892,75×10140,01693,110,0084224,7
No. 7of 2.72×10140,00362,871,80×10140,00852,930,004936,2
No. 8to 3.41×10140,00832,49the 2.46×10140,02062,80 0,0123449,2

During the test for each sample was carried out: external examination and determination of dielectric parameters (ρν, tgδ, ε) with a frequency of 1 time per day during the initial period of the test (up to 4 days) and 1 every 2-3 days thereafter. According to the results of visual observation of the surface condition of the samples was noted the following:

1) after 2 days from the start of the trials the appearance of visible changes of the surface coating on the effects of corona discharge;

2) after 8 days the appearance of darkening the surface (about 50% of the area) at a distance of 4 mm from the edge of the high voltage electrodes and the emergence of signs of the influence of corona discharge (faint rosy hue when observed at an acute angle) at a distance of 7 mm from the edge of the electrodes;

3) for the period through 11-17 days - increased darkening of the surface (100% area) at a distance of 5 mm from the edge of the high voltage electrodes and the distribution of traces of impact (low iridescent shade) to a distance of 8 mm from the edge of the electrodes;

4) after 29 days - increased darkening of the surface and the expansion of this area to a distance of 6 mm from the edge of the electrodes;

5) over the entire period from 31 to 60 days (end of test) -the size of the areas with a visible change in the surface condition almost seminalis: area darkened surface was in the form of rings with diameters of 26 mm and 12 mm, and the traces from the effects of corona discharge was noted at a distance of 9 mm from the edge of the electrodes.

Throughout the test period ρν, tgδ and ε test pieces were changed slightly. All obtained values were in the range of possible deviations due to the uneven thickness of the samples and variations in the ambient temperature during measurement. Changes in surface conditions in the area affected by the corona discharge indicate the processes of destruction of polymer material.

It was found that after 10 or more days after the start of testing these processes are beginning to stabilize, and the rate of destruction of the coatings with soot content of 3.5-5% (compositions No. 10 and No. 11) is less than that of coatings containing 0.5% and 1% (formulations # 9 and # 12).

Based on the obtained results, we can draw the following conclusions:

1) samples of organosilicon compositions with increased to 3.5-5% soot content (compositions No. 10 and 11) are more resistant to the effects of corona discharge of long duration; however, the optimal content of carbon black is 0.5 to 2.5%;

2) the increase in the content of carbon black is not lowered water-repellent properties, determined by the increase in mass after hydration in distilled water;

3) samples containing 1,25-2,5% low molecular weight silicone fluids 119-215, possom hydrophobic properties (moisture absorption) are only slightly inferior to samples containing 3.5-4% low molecular weight silicone fluids 119-215.

4) In order to increase tregimeerotike resistance of the coating as antipyrine in its composition is administered and the hydrate of aluminum oxide Al R has a greater solubility in the Solvent oil than titanium dioxide, which greatly facilitates the preparation of water-repelling compositions in "field conditions" (directly on the site of waterproofing).

The presence of chemically bound water allows part of the molecules of the hydrate of aluminum oxide to participate in the one-component polymerization of organosilicon compounds of cold hardening. This increases the rate of polymerization, and some of the aluminum atoms is included in the structure of the polymer chains, which increases their resistance to thermal degradation.

The increase in the number of hydrate of aluminum oxide increases democractically coverage. But at the same time reduces the specific volume resistivity and increases the tangent of dielectric loss angle measured on the sample after 24 hours of hydration in distilled water.

5) Increase the proportion of low molecular weight silicone fluids 119-215 (more than 2.5%, i.e. up to 3-5% or more by weight COCS), as shown by the experiments, slows down the polymerization processes. As a result, the surface shall rnost coating may long remain sticky and particles contaminated particles, fallen during this time, saturate the surface layer, reducing its dielectric characteristics.

KOK ensures the formation of a mechanically stable coatings, and low molecular weight silicone fluid 119-215 fills the free spaces formed during solidification, preventing the penetration of water molecules and ions of salts due to their diffusion from the environment. This reduces the moisture permeability and moisture absorption coating, increases its resistance to surface leakage currents and partial discharges.

After a comprehensive analysis of all the data about the changing characteristics of the test samples (α, ρν, tgδ, ε), together with the available information on the mechanisms of oxidation of organic polymers, it was concluded that the proposed mechanism of physical-chemical "destruction" hydrophobic coatings studied type includes the following steps:

Stage # 1. The oxidation of a metal of groups active oxygen atoms:

≡Si-CH3+2O•⇒≡Si-HE+H2CO↑

Chemical interaction takes place with a slight increase in mass. Group - OH formed on the surface of the coating easily form hydrogen bonds with water molecules and with the increase in the number of these groups, the surface becomes hydrophilic properties (sharp drop hydrophobic properties after crackower the military effects of corona discharge).

Stage # 2. The increase in the "structuring" of the surface is the formation of new Si-O links ("links"):

≡Si-OH+HO-Si≡⇒≡Si-O-Si≡+H2O

≡Si-HE+H3C-Si≡⇒=Si-O-Si≡+CH4

≡Si-HE+H3C-Si≡+O2=⇒=Si-O-Si≡+CO2↑+H2

This chemical interaction takes place with decreasing mass. The result: compacted surface layer is hindered diffusion of oxygen into the coating. The decrease in the number of groups OH on the surface of the coating contributes to the restoration of hydrophobic properties.

Stage # 3. Destruction at both ends of the siloxane chains with the formation of low-molecular siloxanes:

HO-Si(CH3)2-O-Si(CH3)2-O-Si(CH3)2-O-Si≡⇒

⇒[Si(CH3)2-O]3+HO-Si≡

Chemical reactions of this type are no mass change. In the "output" on the surface of low molecular weight siloxanes are recovered hydrophobic properties (increase of the contact angle of the surface in the zone of influence of corona discharge, as well as the emergence of a rosy tint on the surface.)

Stage # 4. Oxidative degradation:

... - Si(CH3)2-...+O3⇒H2CO↑+CH4↑+SiO2

Chemical transformation takes place with a slight increase in mass. As a result of such processes is the accumulation of silicon dioxide on the surface of the coating (the mind is isenia Shine and smoothness of the surface, as well as the appearance of dark hours).

It should be noted that the chemical reaction of step 1 is the "initiator" of the reaction stages # 2 and # 3. When prolonged exposure to corona discharge these reactions (reduction and increasing mass) occur simultaneously, resulting in the destruction mechanism of silicone coating has a very complex character.

Since the results of visual inspection on samples not detected geometric "growth" area of influence of corona discharge, it is possible to make the following assumptions:

- all tested coatings (compositions No. 9-No. 12) have coronopifolia sufficient for their successful application for at least 5 years in the insulation of existing high-voltage lines and substations;

- temporary loss of hydrophobicity on separate parts of the surface due to the impact of the crown will not cause a significant reduction blagorazumnyi characteristics gidrofobizirovannogo insulator as a whole.

The effectiveness of this technical solution is confirmed by the results of comparative tests on the samples and on the real insulators. The samples were tested in the chamber of the fog in continuous flow surface leakage current characteristic of the operation (4-5 mA), and the insulators in the cell salt fog when exposed to the operating voltage and the surface is rnostly partial discharges.

As follows from the results of tests on samples and insulators, the hydrophobic coating "KOK+low molecular weight silicone fluid has a better performance than the well-known floor. The optimum weight ratio between the compound and the low molecular weight silicone fluid is 1:(0,0125-0,025).

The composition may be applied to the surface of the insulation spray (mechanized), by immersing the processed product in the composition or brush. To provide the necessary viscosity of the composition when applied mechanically using the device type of spray gun are encouraged to use the solvent-Solvent oil". After application to the surface, the solvent evaporates, without affecting the electrical characteristics of the coating.

The optimum weight ratio between the compound and the hydrate of aluminum oxide for maximum increase mesocestoides, while maintaining the dielectric characteristics of the coating to the relevant regulations of silicone rubber (TU 3.72-00216473-028-2001)is 1:(0.05 to 0.15) by weight of the compound.

In developed technical solution, the curing KOK is carried out using a catalyst (hardener) methyltriacetoxysilane or To-10C at room temperature in the presence of power and air. This is because the catalyst-To-10C (methyltriacetoxysilane) has an acidic reaction, because when in contact with moisture in the air it rapidly hydrolyzed with the formation of acetic acid. It is in large quantities is released during the curing of the rubber SCTN the addition of hydrogen atoms of hydroxyl groups of the rubber to the acidic residues of the catalytic Converter.

Vulcanization takes place only in the presence of moisture in the air. If this occurs before the hydrolysis of the acetate groups, and then condensation of molecules with crosslinking agents containing three functional groups, resulting in increased molecular weight. Released acetic acid, having a characteristic odor, evaporates from the system.

Aggressive concentrated acetic acid, as shown by tests, causes corrosion damage of carbon steel. Acid secretion is accompanied by shrinkage of the water-repellent. Shrinkage of water-repellent and corrosion of steel are the main causes of insufficient adhesive strength of the connection surface konstruktivnih elements insulator with a wetting agent, resulting in the peeling of water-repellent surface of the insulator and the penetration of moisture to the surface of the insulator and the interface of the insulator-coated".

Attempt to use other catalysts from which eridania rubber SCTN, not forming acetic acid, have not yielded positive results. Thus, the use of well-known catalyst For-18 (tetraethoxysilane) has considerably complicated the technology of waterproofing, increased curing time and did not improve quality insulators.

The complexity of the technology was that the water-repellent agent with a catalyst K-18 is a two and require mixing before application. The vulcanization reaction proceeds very slowly, so it requires acceleration corresponding catalysts are acidic or alkaline in nature. These are metal salts or ORGANOMETALLIC compounds: Sn, Pb, Ti, Zn. Mainly used octoate tin Sn(OOCC7H15)2.

The curing reaction with catalyst K-18 is also accompanied by the release of by-product (in this case alcohol) and, as a result, the shrinkage of the sealant (water-repellent). In addition, the use of water-repellent with catalyst K-18 requires pre-priming the surface of metals.

The above analysis of the mechanisms of curing water-repellent agent showed that sealing insulators should be substances, solidification which occurs without shrinkage and without allocation of by-products, i.e. using K-YUS (methyltriacetoxysilane).

Developed technical solution is illustrated by the ri using 1-14, where: figure 1 shows an arc on the surface of the vulcanized coating at a current of 10 mA; figure 2 shows the state of the coating surface after 1 min its impact in current of 10 mA; figure 3 shows a character arc when current 50 mA; figure 4 shows the surface condition of the coating exposed to the current 50 mA after the power is turned off; figure 5 shows the combustion products of degradation of the coating in the channel arc before its extinction; 6. shows the surface appearance of the coating after the extinction of the combustion products of degradation of the coating in the channel of the arc; 7 shows the surface appearance of the coating after removal of the charred surface layer in areas where there was the extinction of the arc; Fig shows the surface appearance of the coating after removal of the charred surface layer in areas where there was the extinction of the arc; figure 9 schematically shows the mechanism of the emergence and development of tracking; figure 10 shows the character of wettability gidrofobizirovannogo the surface of the insulator which is characterized by the value of the wetting angle α≥60°; figure 11 shows the character of wettability gidrofobizirovannogo the surface of the insulator after 2 years of operation in the area of cement plant, which is characterized by the value of the wetting angle α=179°; Fig shows the wettability of the surface of dormancy is itia after 10 min of cessation of exposure to corona discharge (right drop on the surface is a control and is outside the area of impact); on Fig shows the wettability of the surface coating after 60 min exposure to corona discharge (right drop on the surface is a control and is outside the area of impact); Fig shows the resilience of the water-repelling composition at ambient temperature +20°C, +25°C, +30°C +35°C and +40°C depending on the amount of organic solvent for KOK.

Preparation and application of liquid SE on the basis of the developed KOK as follows.

The desired hydrophobic KOK prepared on the basis of low-molecular silicone rubber, filler, hardener and solvent. Moreover, as the low-molecular silicone rubber using rubber stamps SCTN, as filler is used as a solid filler in the form of a hydrate of aluminum oxide and carbon black acetylene and liquid filler in the form of low molecular weight silicone fluids 119-215, and as a hardener use methyltriacetoxysilane. The solvent KOK use an organic solvent grade "oil solvent".

Preparation of a solution of a hydrophobic coating desired consistency is as follows. In the compound before mixing with low molecular weight silicone fluid 119-215 impose additional solid filler in the form of acetylene soot, the Les and the resulting liquid composition is thoroughly mixed before the formation of the desired homogeneous mixture.

However KOK contains a 100.0 parts by weight of rubber hydrate of aluminum oxide in the amount of 5.0 to 15.0 parts by weight, acetylene soot in the amount of 0.5 to 2.5 parts by weight, of low molecular weight silicone fluid 119-215 in the amount of 1.25 to 2.5 parts by weight, methyltriacetoxysilane in the amount of 2.5 to 6.5 parts by weight of

Then in the tank for mixing and pouring the solvent, and then add the fillers in the form of a hydrate of aluminum oxide, and the resulting solution is stirred to form a homogeneous mixture.

Moreover, the weight ratio between KOC and the solvent is selected depending on the ambient temperature, while the desired weight ratio by 100.0 parts by weight of rubber is (0,85-1,0) parts by weight at ambient temperatures up to 25°C and (1,05-1,4) parts by weight when the ambient temperature is over 25°C. At the same time applying a hydrophobic coating is carried out at an ambient temperature not lower than minus 10°C and the absence of precipitation, and dew.

Cooked SE on the basis of COCS in devulcanization condition characterized by viability (viability) at a temperature from 15°C to 35°C within 15-60 min (see Fig). After that make cleaning gidrofobiziruyuschey surface from the existing dirt and put a layer of cooked hydrophobic composition of the required thickness. Approximately 30 min after the application of SE vulcanizer what is and gidrofobizirovannym insulating design may be used.

Thus, the advantage of the developed KOK in comparison with analogues and the prototype is the increased reliability and longer service life caused vulcanized SE based on the COCS, the optimization of its structure, which also leads to the increase blagorazumnyi voltage high-voltage insulation throughout the long period of its use.

For example, the results of testing electrical insulating structures obtained using the proposed technical solution, the permissible operating voltage and the electric field is confirmed by the reduction of the probability of overlapping chains of insulators due to contamination by at least 15-20%.

All tested hydrophobizated insulators tested on takingemotional resistance (more than 500 hours) and can be operated in areas with a high level of serrazanetti atmosphere to the 4th be inclusive, the relative humidity of the atmosphere within 20-100%, the value of the maximum allowable operating voltage is supplied to the insulating structure, within 6-750 kV.

The amplitude of the main leakage currents through hydrophobizated insulators were 1.5-2 times less than through insulators without coating. In actual use, this value will be larger, because the surface is th organosilicon polymer coatings significantly less polluted. In addition, the resulting hydrophobic coating based KOK specified structure in volcanoserver.com condition has improved performance properties compared compared with the known coatings (see table 4).

Table 4
The dielectric characteristics of the coatings obtained on the basis of the developed KOK-component cold curing
Compositionthe specific volume resistance ρνnot less thansurface resistivity ρsnot less thanthe tangent of dielectric loss tgδ, no more thanthe relative dielectric permittivity, ε, of not less than
On the basis of the developed KOK4,82×1014of 2.0×10150,0083,11

In addition, developed KOK characterized in volcanoserver.com state specific volume electric resistance ρνnot less than 3,0×1014Ohm×cm, the specific surface electric resistance ρsnot less than 1.0×105 Ω, the tangent of dielectric loss angle tgδ at frequency 50 Hz no more than 0,008, conditional bursting tensile strength not less than 0.55 MPa, elongation at break not less than 100%, electrical strength in distilled water of at least 10 kV/mm, and the strength of bonding with the metal when the Flack is not less than 0.60 N/m

Optimization of the composition and ratio of components KOK, in turn, minimizes the loss of consumables when the hydrophobization of the surface of the insulating structures based coating KOK.

The effectiveness of the developed KOK when it is used in the application of technology SE mechanized method is confirmed by more than 15-year positive experience of its application in substations that are located in areas with heavy industrial pollution.

At the same time most optimal composition of SE, as well as improved cleaning and self-cleaning" get gidrofobiziruyuschey surface high-voltage insulation allow preventive measures to exclude work on the removal of the "old" SE layer before applying the "new" and ensure the effective operation of the coating without additional preventive measures for at least 10 years.

The results of the conducted research can is also used in the manufacture of the outer polymeric insulation of the other high-voltage electrical equipment: surge arresters, reference and bushings, current transformers and voltage.

1. Hydrophobic organosilicon compound for insulating constructions based on one - or both supplied in two packages of organosilicon compositions of cold hardening, which contains low-molecular silicone rubber, a filler and a hardener or catalyst, characterized in that the compound in volcanoserver.com condition characterized by the value of the wetting angle of 60° to 179°, tregimeerotike resistance when the length of trials, amounting to at least 500 h at operating voltages 6-750 kV, as well as arcing, characterized by the value of the arc current is not less than 100 mA with duration of exposure not less than 600 C.

2. The compound according to claim 1, characterized in that it is in devulcanization condition characterized viability at temperatures from 15°C to 35°C within 15-60 min, and volcanoserver.com the condition is characterized by the conditional bursting tensile strength not less than 0.55 MPa, elongation at break not less than 100%, specific volume electric resistance ρvnot less than 3,0·1014Ohm×cm, the specific surface electric resistance ρsnot less than 1.0·1015Ω, the tangent of dielectric loss angle tgδ at frequency 50 Hz no more than 0,008, elec the historical strength in distilled water of at least 10 kV/mm, as well as the strength of bonding with the metal when the Flack is not less than 0.60 N/m

3. The compound according to claim 1, characterized in that it is in volcanoserver.com condition is characterized by life, constituting not less than 10 years, when operating in conditions of temperatures from -60°C to + 65°C.

4. The compound according to claim 1, characterized in that as the low-molecular silicone rubber it contains rubber stamps SCTN, as filler it contains as a solid filler in the form of a hydrate of aluminum oxide and carbon black acetylene and liquid filler in the form of low molecular weight silicone fluids brand 119-215, and as a hardener compound contains methyltriacetoxysilane.

5. The compound according to claim 4, characterized in that it contains a 100.0 parts by weight of rubber of low molecular weight silicone fluid in an amount of 1.25 to 2.5 parts by weight of the hydrate of aluminum oxide in the amount of 5-15,0 parts by weight, acetylene soot in the amount of 0.5 to 2.5 parts by weight and the curing agent in the amount of 2.5 to 6.5 parts by weight of



 

Same patents:

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FIELD: electricity.

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FIELD: electricity.

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The invention relates to electrical engineering, in particular to the production technology insulators for the electrical industry

FIELD: electricity.

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EFFECT: improving reliability and increasing service life of applied water-proof electric-insulating coating in vulcanised condition.

6 cl, 2 dwg, 2 tbl

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