RU2405223C1 - Electrically insulating liquid composition based on vegetable oil - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: complex of oxidation inhibitors based on alkyl phenols together with synergetics based on alkyl sulphides, as well as chelating agents and antiseptic agents are added into electrically insulating vegetable oil-based composition using low-viscosity thinner.

EFFECT: better stabilisation of dielectric composition.

2 cl, 1 tbl, 4 ex

Description

The invention relates to the field of electrical engineering, for the production of electrical insulating liquid compositions based on vegetable oils and their use as a cooling dielectric fluid for power and distribution transformers, reactors, power cables. Currently, in the electrical industry, electrical insulating liquid compositions based on vegetable oils are used: Envirotemp, Biotemp, and Midel (TVOommen "Vegetable oils for liquid-filled transformers", IEEE Electrical Insulation Magazine, No. 1, 2002, volume 18, p.6 ÷ 11) [1], Biotemp and Midel (M. Hammer, R. Badnt, AJSchwab "Electrcal properties of rape-seed oil", Conference on Electrical Insulation and Dielectric Phenomena, 2002, p. 83 ÷ 86) [2], which have been used in electrical equipment of medium and low power in Europe, Canada, and the United States for 10–15 years. The use of such liquids allowed to increase the level of fire safety and the ecology of electrical equipment.

Common features of the considered liquid compositions:

1. The main component is refined vegetable oil.

2. Modifying additives:

- antioxidants (oxidation inhibitors);

- antiseptics;

- diluents.

Known insulating liquid in vegetable oil or a mixture of vegetable oils, which are triglycerides of vegetable acids (oleic, erucic, palmitic, stearic and some other saturated and unsaturated acids). (US Pat. No. 2002109128 (A1), class H01B 3/20, published August 15, 2002) [3] The liquid contains an antioxidant selected from the group: butylated hydroanisole, tert-butylhydroquinone, butylated hydrotoluene, trahydrobutrophenone, ascorbyl palmitate, propyl gallate and α tocopherol, β-tocopherol, Δ-tocopherol. As a diluent, this composition includes substances selected from the group: polyvinyl acetate oligomers, acrylic oligomers, polyvinyl acetate and acrylic polymers, as well as mixtures thereof. The disadvantage of this composition is the low level of viscosity. It is used for equipment for the generation and distribution of electricity.

In another invention (Patent WO 0078900 (A1), class H01B 3/20, published December 28, 2000) [4] an electrical insulating liquid based on high oleic soybean oil containing antioxidants is proposed. As an antioxidant, tert-butylhydroquinone is used, which is introduced in an amount of (0.02 ÷ 1.0) wt.%. The use of a mixture of antioxidants is also considered: citric acid in an amount of (0.001 ÷ 0.1) wt.% And tert-butylhydroquinone in an amount of (0.02 ÷ 1.0) wt.%. Methyl esters having carbon atoms (16 ÷ 18) in the molecular chain are used as diluent. A common disadvantage of the above inventions is the use of insufficiently effective antioxidants, which can adversely affect the stability of the dielectric properties of these compositions during operation of the equipment.

Closest to the proposed compositions of our invention is a dielectric fluid based on vegetable (rapeseed or sunflower) oil, which is used for electrical equipment, power transformers (Patent US 2006030499 (A1), class H01B 3/20, published 02/09/2006) [ 5]. The composition includes from (0.1 ÷ 0.3) wt.%, An antioxidant or a mixture of several antioxidants: butylated hydroxyanisole, butylated hydroxytoluene, mono-tert-butylhydroquinone. To improve technological properties, (1 ÷ 24) wt.% Insulating liquids selected from the group consisting of mineral oil, synthetic esters, synthetic hydrocarbons are introduced into the composition.

The composition has the following technical indicators:

1) dielectric strength - not less than 35 kV / 2.5 mm;

2) pour point - not more than minus 25 ° C;

3) ignition temperature - not less than 300 ° С;

4) oxidative stability - not less than 100 hours.

The disadvantage of this solution is the reduced level of dielectric strength and oxidative stability of the composition (100 hours).

The essential features of our invention are the introduction of a complex of new additives into the composition of vegetable oil, which contribute to increasing the stability level of the properties of the insulating composition during its operation. This will increase the level of reliability and durability of electrical equipment: power and distribution transformers, reactors, capacitor columns, power cables. The aim of the present invention is, in comparison with the closest analogue (prototype), increasing the level of dielectric properties and oxidative stability of the composition based on vegetable oil while maintaining a sufficiently high level of its technological properties.

As the basis of the composition, vegetable oil is used: rapeseed, sunflower, corn or a mixture of these oils, which have a high content of oleic acid fatty esters. The oil is first cleaned of impurities: refined, bleached, deodorized. In order to increase the level of dielectric properties and oxidative stability, a complex of special additives is introduced into the oil, which were first used in this technical solution: oxidation inhibitors together with synergists, chelating agents for binding metal cations, antibacterial substances. To lower the level of viscosity and pour point, low-viscosity diluents are introduced into the composition:

1. Alkylphenols (2,6-di-tert-butyl-4-methylphenol, 3-tert-butyl-4-hydroxyanisole, 2-tert-butyl-4-hydroxyanisole and mixtures thereof) are used as oxidation inhibitors (primary stabilizers) and 4-hydroxydiphenylaniline in an amount of (0.1 ÷ 0.5) wt.%.

2. Dialkyl sulfides were used as synergists: bis (stearyl propionate) sulfide, bis (lauryl propionate) sulfide, 4,4'-diaminodiphenyl sulfide, and mixtures thereof in an amount of (0.1 ÷ 0.5) wt.%.

3. As chelating agents used are 8-hydroxyquinoline, 8-hydroxyquinaldin, anthranilic acid, disalicylidenealkyl diamines in an amount of (0.1 ÷ 0.5) wt.%.

4. As antiseptics, 8-hydroxyquinoline, 8-hydroxyquinaldin, benzoic acid in the amount of (0.05 ÷ 0.5) wt.% Were used.

Strengthening the inhibitory effect of additives is achieved by the simultaneous introduction of synergists (secondary stabilizers) and chelating agents, which together enhance the action of the main inhibitors (primary stabilizers). It should be noted the special role of chelates (8-hydroxyquinoline and 8-hydroxyquinaldine), which are both chelating agents and antiseptics. In order to maintain a low level of viscosity and reduce the pour point of the oil, low-viscosity esters based on phthalic acid and primary saturated alcohols are used as diluents. Alcohols contain in the molecular chain (2 ÷ 8) carbon atoms. The esters were introduced in an amount of (5.0 ÷ 20.0) wt.%. Mixing oil with additives is carried out in a reactor equipped with a stirrer and heating.

The method of preparation of the composition:

a) - purified oil is loaded into the reactor;

b) - heated to a temperature of 40 ± 5 ° C;

c) - add additives;

g) - mix the components for 30 ÷ 60 minutes;

d) - cooled to ambient temperature.

The test compositions are carried out according to the following parameters:

1. Breakdown voltage at AC according to IEC 60158 (2.5 mm), kV, min;

2. Dielectric loss tangent at 25 ° С according to IEC 60247;

3. Oxidative stability according to IEC 61125C, hours;

4. Viscosity at 40 ° according to ISO 3104, cSt;

5 Pour point according to IEC 60814, ° C.

The compositions of the studied compositions (wt.%) Are given in the examples: 1 ÷ 4.

Example 1

- 2,6-di-tert-butyl-4-methylphenol 0.5 - bis (lauryl propionate) sulfide 0.5 - 8-hydroxyquinoline 0.5 - dioctylphthal 20,0 - rapeseed oil 78.5

Example 2

- 2,6-di-tert-butyl-4-methylphenol 0.1 - bis (lauryl propionate) sulfide 0.1 - 8-hydroxyquinoline 0.1 - dioctyl phthalate 5,0 - rapeseed oil 94.7

Example 3

- 2,6-di-tert-butyl-4-methylphenol 0.5 - bis (stearyl propionate) sulfide 0.5 - 8-hydroxyquinaldine 0.5 - dibutyl phthalate 5,0 - a mixture of oils (rapeseed and sunflower (1: 1) by weight) 93.5

Example 4

- 2,6-di-tert-butyl-4-methylphenol 0.1 - bis (stearyl propionate) sulfide 0.1 - 8-hydroxyquinaldine 0.1 - dibutyl phthalate 20,0 - a mixture of oils (rapeseed and sunflower 1: 1 by weight) 79.7

Test Results for Test Compositions The name of indicators Examples one 2 3 four Breakdown voltage AC kV, min 53 54.5 52 51.5 Dielectric loss tangent at 25 ° С 0.02 0,03 0,03 0,03 Oxidative stability, hour, not less 164 164 164 164 Viscosity at 40 ° С, cSt 25 thirty 31 28 Pour point
° C -28 -twenty -twenty -23

From the analysis of the results of the tests it follows that the increase in the value of dielectric properties and oxidative stability in electrical insulating liquid compositions based on vegetable oil occurs due to the introduction of a complex of special additives: oxidation inhibitors based on alkyl phenols together with synergists based on alkyl sulfides, chelating agents, antiseptics, and diluents based on alkyl phthalates in the following ratio of components, (wt.%):

- alkyl phenols 0.1 ÷ 0.5 - dialkyl sulfides 0.1 ÷ 0.5 - chelating agents 0.1 ÷ 0.5 - antiseptics 0.05 ÷ 0.5 - thinners 5.0 ÷ 20.0 - vegetable oil (or a mixture of oils) 78.5 ÷ 94.7

The introduction of the proposed complex of additives (oxidation inhibitors together with synergists, chelating substances) into vegetable oil (or into a mixture of oils) leads to an increase in dielectric properties and oxidative stability, which we observe in comparison with the parameters in the composition of a close analogue (prototype), namely:

1. Breakdown voltage increased by (16.5 ÷ 8.5) kV.

2. Oxidative stability increased by 64 hours.

The proposed composition has a fairly high level of technological properties (low viscosity and pour point). Thus, the proposed technical solution provides a higher value of the dielectric properties and oxidative stability of the insulating liquid composition, thereby improving the reliability, durability of electrical equipment, as well as improving the environment.

Information sources

[one]. T.V. Oommen. "Vegetable oils for liquid-filled transformers.", In IEEE lec-trical Insula tion Magazine, vol. 18, No. 1, 2002, p. 6 ÷ 11.

[2]. M. Hammer, R. Badnt, A. J. Schwab. "Electrical properties of rape-seed oil", Conference on Electrical Insulation and Dielectric Phenomena (CEID), 2002, pp. 83 ÷ 86.

[3]. Patent US2002109128 (A1), class H01B 3/20, published August 15, 2002.

[four]. Patent WO 0078900 (A1), class H01B 3/20, published December 28, 2000.

[5]. US patent 2006030499 (A1), class H01B 3/20, published 02/09/2006.

Claims (2)

1. An electrical insulating liquid composition based on vegetable oil or a mixture of vegetable oils, mainly rapeseed, sunflower, corn, pre-purified, with a high content of oleic acid fatty esters, as a coolant for high-voltage equipment, containing an oxidation inhibitor based on alkyl phenol selected from the group containing 2,6-di-tert-butyl-4-methylphenol, 3-tert-butyl-4-hydroxyanisole, 2-tert-butyl-4-hydroxyanisole, and mixtures thereof, and 4-hydroxydiphenylaniline, dialk-based stabilizer lsulfide selected from the group: - bis (stearyl propionate) sulfide, bis (lauryl propionate) sulfide, 4,4'-diaminodiphenyl sulfide and mixtures thereof, a chelating agent selected from the group - 8-hydroxyquinoline, 8-hydroxyquinaldine, anthranilic acid, disalicylidenealkyl diamine, selected from the group - 8-hydroxyquinoline, 8-hydroxyquinaldine, benzoic acid, as well as a diluent in the form of a mixture of a low-viscosity phthalic acid ester and primary saturated alcohol, in the following ratio, wt.%:
alkyl phenol 0.1 ÷ 0.5 dialkyl sulfide 0.1 ÷ 0.5 chelating agent 0.1 ÷ 0.5 antiseptic 0.05 ÷ 0.5 diluent 5.0 ÷ 20.0 vegetable oil or a mixture of oils 78.5 ÷ 94.7 2. Electrical insulating liquid composition based on vegetable oil according to claim 1, characterized in that the preliminary cleaning of the oil is carried out by refining, bleaching, deodorization, refining.