DE2935211A1 - ELECTRICAL DEVICE WITH AN ELECTRICAL ELEMENT IMPREGNATED WITH OIL AND AN ELECTRICAL INSULATING OIL - Google Patents

Description

Electrical device with an electrical element that works with oil is impregnated, and an electrical insulating oil

The invention relates to an electrical device comprising an electrical element impregnated with oil and an electrical one Insulating oil.

In various electrical devices, such as capacitors, transformers and cables, insulation paper and / or is used Plastic film used as dielectric or insulation material, with mineral oil being the most commonly used insulating oil with which the devices are impregnated.

However, mineral oil has such a high pour point and viscosity that it is difficult to make an insulating or dielectric Impregnate material deeply with oil. Electrical devices impregnated with mineral oil therefore have inferior performance electrical properties, such as corona property and dielectric breakdown strength, that extend the life of the device to decrease. As the viscosity increases with decreasing temperature, the electrical properties become electrical Devices impregnated with insulating oil of high viscosity

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- 5 are significantly deteriorated in a cold environment.

The invention is therefore based on the object, the electrical To improve the properties of electrical devices impregnated with oil. In particular, the electrical devices be compact and light. In particular, the properties of such oil-impregnated electrical devices are intended which have plastic film (plastic film) as an insulating material or a dielectric material can be improved.

In addition, an electrical insulating oil for oil-impregnated electrical devices are specified, which improves their electrical properties.

Electrical devices according to the invention are impregnated with an insulating oil having a composition having the structural formula

ο-

CH ₃

wherein R is selected from the group consisting of CH and C ₂ H ₅ .

The composition in which R is the compound CH- is 1-rienyl-1- (methy ^ tenyl) -ethane, which is hereinafter abbreviated to MDE, the composition in which R is the compound C ₂ H ₅ , 1-Hienyl-1- (Ethy ^> henyl) -ethane, which is hereinafter abbreviated to EDE.

The electrical devices according to the invention are also impregnated with a mixture of EDE and MDE.

According to the invention, either EDE or HDE or a mixture is used. both of these compositions are used as insulating oils in electrical devices. The mixture of EDE and MDE is hereinafter referred to as E / MDE «,

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EDE, MDE and E / MDE have a lower pour point and before a lower viscosity, a higher ignition point, a higher one Luminous gas generation voltage (glow voltage) and a higher dielectric constant than mineral oil. In other words, an electrical insulating oil with one of these compositions has better electrical properties than mineral oil.

For electrical devices that have plastic film (plastic film), which is non-porous and has a smoother surface than insulating paper, as insulating material or dielectric, it is difficult for the insulating oil to penetrate the film. A low viscosity of the oil increases its ability to penetrate the plastic film to penetrate. Since the oil according to the invention has a lower Having viscosity than mineral oil, the electrical properties of devices impregnated with that oil, such as the dielectric breakdown strength and so on, improved.

The oil according to the invention is also good in terms of swellability and solubility of plastic film better than mineral oil. If a plastic film has a high swellability, i.e. absorbs so much oil that it swells, the apparent volume of the film increases, so that the gaps or Passages between the film layers for the passage of oil are narrowed and the oil circulation caused by them is reduced will. When the plastic film absorbs a lot of oil, voids (bubbles) are created between the film layers. The result is an increase in temperature of the electrical device and etie simultaneous reduction of their dielectric breakdown strength or breakdown strength. If larger amounts of plastic film are dissolved in the oil, the electrical properties of the film deteriorate.

By using the oil of the present invention in conjunction with a plastic film, it is possible to prevent such a temperature rise to prevent the dielectric strength of the electrical device from improving and deterioration to prevent the properties of the film.

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The oil according to the invention is particularly useful as an insulating oil "for electrical" Capacitors suitable. In the case of a capacitor impregnated with an oil according to the invention, the energy density is (the product of the dielectric constant and the square of the field strength) is considerably higher than that of one with Mineral oil impregnated capacitor. With the same energy density Can the capacitor volume therefore be reduced?

A capacitor according to the invention withstands overvoltages longer stood before breakdown occurs as a capacitor impregnated with mineral oil or other conventional insulating oils.

The invention is described in more detail below with reference to the drawing. Show it;

Fig. 1 shows the percentage of only insulating paper as the dielectric capacitors that a constantly over the If value lying Jöbetriebs AC voltage without breakdown withstand,

Figure 2 graphically shows the percentage of both insulating paper and polypropylene film as the dielectric Capacitors, one constantly over the characteristic value withstand lying operating AC voltage without breakdown,

Figure 3 graphically shows the percentage of polypropylene film alone as a dielectric having capacitors that have an operating AC voltage that is constantly above the nominal value withstand without a breakthrough,

Fig. 4 Corona ignition voltage characteristics of polypropylene film alone as dielectric capacitors depending on the heating time,

Fig. 5 Characteristic curves of the corona ignition voltage of capacitors which

both insulating paper and polypropylene film as Have dielectric, depending on the heating time and

6 Characteristic curves of the temperature rise of transformers during a heating test.

The oils according to the invention are first described below. The dielectric properties of the invention Oils are given in Table I, which at the same time contains the characteristic values of mineral oil (hereinafter referred to as MO abbreviated), from 1-rienyl-1- (dimethylphaiyl) ethane (hereinafter abbreviated to PXE) and from alkylbenzene (hereinafter abbreviated to Aß). PXE and AB were recently used as insulating oils proposed for oil-impregnated electrical devices.

As the table shows, the oils of the invention differ from the known oils is that the viscosity of the oils according to the invention at 30 ⁰ C is below 5 cst.

Table I.

EDE MDE E / MDE Md PXE AB

Specific gravity 0.980 0.983 0.982 0.879 0.988 0.870 Ignition point ( ⁰ C) 148 144 146 135 148 136

Pour point ( ⁰ C) <-60 ^ -60 <-60 -32 -47.5 <-60 Viscosity 3Q ° C (cst) 4.1 4.0 4.1 10 6.5 10

O ⁰ C (cst) 10.5 10.5 10.5 60.3 22.3 55.2

Luminous gas generation voltage (kV / mm) 81 81 81 45 78 52 dielectric

(§S ^g ir60 Hz) ^{2 '45 2} ' ^{45 2 '45 2} ' ^{20 2 '49 2} > ¹⁷

Dielectric losses

(80 ° C, 60 Hz) (%) 0.01 0.01 0.01 0.005 0.01 0.007

As you can see, EDE, MDE and E / MDE have a lower one

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Pour point and a lower viscosity, especially at lower temperatures, than MO and PXE and a lower one Viscosity than Aß. Furthermore, the dielectric constant and the luminous gas generation voltage (glow voltage) of EDE, MDE and E / MDE higher than that of MO and so on.

The swellability and solubility of plastic film, in particular Polypropylene film (hereinafter abbreviated to PP) in relation to oil will be described below. Table II shows the swollen amount and dissolved amount of PP film and the amounts caused by conventional oils.

As the table shows, to oils of the invention differ from the usual oils characterized in that the swollen amounts of the oils according to the invention at 80 ⁰ C under 2%.

Table II EDE MDE E / MDE MO PXE Aß

Swollen amount (%) 1.4 1.4 1.4 8.6 2.9 8.5 Dissolved amount (%) 0.06 0.06 0.06 0.15 0.10 0.16

The values were measured after PP FiIm had been immersed at 80 ⁰ C in the oils for thirty days. As can be seen, the oils according to the invention are more poorly absorbed by PP-FiIm than MO, PXE and Aβ, and, moreover, PP-FiIm is more poorly dissolved in the oils according to the invention than in the known oils.

As already mentioned, these properties have a "favorable influence on those obtained with the oils according to the invention impregnated electrical devices.

The following details the improvements that by impregnating electrical devices with

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oils according to the invention is achieved.
example 1

Type No. 1 to Type No. 3 capacitors were manufactured and tested. Type No. 1 was used to form the dielectric Element of the capacitor a paper roll of four sheets of insulating paper with a thickness of 25 µm and a density of 0.85 g / cm. The capacity was 1.5 uF.

In the case of type no. 2, PP-FiIm with a Thickness of 18 µm was laid a sheet of insulating paper with a thickness of 18 µm and a density of 0.80 / cm, and then the wound up three sheets to form the dielectric element of the capacitor. The capacity was 12

In the case of type no. 3, two sheets of PP film with a thickness of 18 µm wound to form the dielectric element (dielectric) of the capacitor. The capacity was 10 uF.

The capacitors to be tested were impregnated with oils according to the invention and with MO, PXE and AB, and then the Dielectric constant 8, the field strength G (V / µm) and the energy density £ G measured. The measurement results are in the Table III given.

Furthermore, the corona voltage (V / pm) was determined for various Temperatures measured. The measurement results are given in Table IV.

Tabel C. III 2697 capacitor VJ 4272 Type no. 3.70 Lr 1 2.67 27 2 40

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_ 11 -

3 2.25 41 3782

1 3.70 27 2697

MDE 2 2.67 40 4272

3 2.25 41 37ö2

1 3.70 27 2697

E / MOE 2 2.67 40 4272

3 2.25 41 3782

1 3.70 27 2697

PXE 2 2.67 38 3855

3 2.25 37 3080

1 3.2 17 925

MO 2 2.62 32 2683

3 2.23 32 2283

2.25 41 IV 20 ° C 3.70 27 65 2.67 40 90 2.25 41 95 3.70 27 65 2.67 40 90 2.25 41 95 3.70 27 65 2.67 38 90 2.25 37 95 3.2 17th 63 2.62 32 88 2.23 32 93 Tabel 55 -40 ⁰ C 65 47 75 65 65 47 65 65 47 65 65 35 50 47 17th 15th 15th

Oil condenser -40 ⁰ C 20 ° C 80 ⁰ C type Wr.

1 47 65 90

EDE 2 65 90 120

3 65 95 120

1 47 65 90

MDE 2 65 90 120

3 65 95 120

1 47 65 90

E / MDE 2 65 90 120

3 65 95 120

1 35 63 90

PXE 2 50 88 110

3. 47 93 110

1 17 55 70

MO 2 15 65 75

3 15 75 75

As Table III shows, those with EDE, MDE or E / MDE

.impregnated capacitors have a significantly higher energy density

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than those impregnated with MO or PXE. The energy density of the capacitors impregnated with the oils according to the invention is, for example of type IMr. 1. about three times higher than that of one capacitor impregnated with MO. Because the volume of a capacitor is inversely proportional to its energy density the volume of a capacitor impregnated with EDE, MDE or E / MDE can be reduced to about one third of the volume a capacitor impregnated with MO.

As can be seen from Table IV, is with the invention Capacitors have a corona ignition voltage and therefore the dielectric strength higher than that of those impregnated with MO or PXE Capacitors, especially at low temperatures. The reason for this is seen in the fact that the invention Oils have lower pour points and viscosity values compared to MO etc., especially at low temperature.

The wettability of the oils according to the invention and that of MO etc. were compared on the basis of the wetting of PP films.

3 2 While the area wetted by MO 7 x 10 mm and that of

PXE wetted area was 18 χ 10 ^ mm ² , EDE, MDE and E / MDE all wetted an area of 23 x 10 ^ mm ² . This shows that the oils of the present invention had better wettability than MO and so on. The reason for this is believed to be that the oils according to the invention penetrate PP film layers more easily in order to immerse them.

The area wetted by the oils was measured as follows: First, 0.02 cm of the oil was applied to a sheet of PP film on which another sheet of film was then dropped from a height of 2 cm. After 20 minutes the area wetted by the oil droplet in the film layer measured.

Figures 1 to 3 show the percentage of capacitors that a constantly applied AC voltage from one and a half times the nominal voltage at a temperature of

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80 ⁰ C withstood. Line A applies to capacitors that were impregnated with EDE, MDE and E / MDE; the stepped line ü applies to capacitors that were impregnated with MO; and the angled line C is for capacitors impregnated with PXE.

1 was a capacitor of the type IMr mentioned. 1, in Fig. 2 by type no. 2 and in Fig. around those of the type Wr. 3. Ten capacitors were tested for each type of oil and for all three types.

For example, in the test according to FIG. 2, in the case of the capacitors impregnated with MO, 20 % of all capacitors had a dielectric breakdown on the hundredth day and a further 30% on the one hundred and twenty day and with a further 20 % on the one hundred and thirty day. Overall, only 30 % of the capacitors withstood the overload.

In contrast, none of the ones impregnated with EDE, MDE and E / MDE existed Capacitors breakdown after 140 days. The same applies to the other capacitor types. With Capacitors impregnated with oils according to the invention therefore have a significantly longer service life than the known capacitors.

Figures 4 and 5 illustrate the dependence of the Coronazündspannung (V / pm, 25 ⁰ C) impregnated with the oil and then heated to 70 ° C capacitors of the heating time. In Fig. 4 Is it capacitors of the type mentioned Ur , 3 and in FIG. 5 by type no. 2. In both FIGS. 4 and 5, curve A applies to the capacitors impregnated with EDE, MDE and E / MDE, curve B applies to the capacitors impregnated with MO and the curve C for the capacitors impregnated with PXE »

For example, as shown in Fig. 5, the Coroma reaches ignition voltage in the case of the capacitors impregnated with MO after a

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Heating time of about 40 hours a saturation value, while in the case of the capacitors impregnated with the oil according to the invention the saturation value is reached after a heating time of about 15 hours. 4 shows the same behavior. The reason for this is seen in the fact that the invention Oils have good penetrability due to good wettability on PP film and have a low viscosity.

Compared to capacitors impregnated with MO or PXE as suggested in recent years, the oils according to the invention therefore enable the production of capacitors with smaller dimensions (smaller volume) as well as the increase in dielectric strength, corona ignition voltage and service life. The oils of the invention are particularly suitable at low temperatures and for the impregnation of capacitors at low ambient temperatures should be used.

Also with regard to the interaction with PP-FiIm, the Oils according to the invention are favorable, so that PP film is particularly suitable as the dielectric of a capacitor or a part thereof is. A fiction, contemporary s oil can be used not only for power capacitors, but also for direct current capacitors will.

Example 2

In this example, power cables have been manufactured and tested.

The power cables were two meters long and wrapped in a strip of insulation paper with PP-FiIm was coated. The cable temperature was maintained at about 70 ° C while a tension of one and a half times the actual value applied to the cables. After a hundred days, eight out of ten cables impregnated with MO occurred and on six out of ten cables that were impregnated with AB

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dielectric breakthrough or breakdown. Against it joined all cables impregnated with EDE, MDE and E / MDE, no breakthrough after a hundred days.

It is believed that those impregnated with MO and Aü Cables the PP-FiIm was dissolved in the oils, so that the viscosity of the oils increased and the convection was blocked, resulting in a rapid rise in oil temperature and ultimately dielectric breakdown. When with the invention Oiling impregnated cables, however, a smaller amount of the PP film was dissolved, so that the viscosity of the oils remained unchanged and no dielectric breakdown occurred. It can therefore be assumed that with the invention Oil-impregnated cables have a longer service life in practice.

Example 3

In this example, transformers have been manufactured and tested.

The nominal data of the transformers were 5000 kVA and 77 kV, whereby the windings were insulated with PP-FiIm. Table IV shows the corona ignition voltage of the transformers when impregnated with the oils mentioned.

EDE Tabel V MO kV 110 kV MDE E / MDE <80 kV 40 ⁰ C 120 kV 110 kV 110 kV 100 20 ° C 120 kV 120 kV

6 shows the rise in transformer temperature as a function of time. Curve B applies to a transformer impregnated with MO and shows that its temperature ^{reaches 50 °} C. after about ten hours, while curve A applies to a transformer impregnated with EDE, MDE or E / MDE and

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shows that the transformer temperature is after about 7.5 hours reaches a value of 45 ° C.

The reason why the transformers impregnated with oils according to the invention have a higher corona ignition voltage and a better one Temperature behavior than those impregnated with MO are seen in the fact that the oils according to the invention have a have a lower pour point and viscosity so that they penetrate deeply into the dielectric and as it increases Temperature a convection occurs, which counteracts the rise in temperature.

Electrical devices designed according to the invention therefore have a compact structure, a long service life, and short ones Corona losses and high dielectric breakdown strength, especially at low temperature. When using PP film as a dielectric and insulation material for the electrical devices is the effect of the oils according to the invention no deterioration in the favorable properties of this film. The oils are biodegradable, so there is no danger pollution is avoided.

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Claims (12)

Claims 1 ,} Electrical device comprising an electrical element impregnated with an oil composed of a composition, characterized in that the composition has the structural formula GH ₃ wherein R is selected from a group formed from CH ₃ and C ₃ H ₅ . 2. Device with an electrical element impregnated with oil is characterized in that the oil is a mixture of a first composition having the structural formula ο- GH. CH ₃ and from a second composition having the structural formula 0 30012/074 3. Apparatus according to claim 1 or 2, characterized in that the element is a capacitor element. 4. Apparatus according to claim 1 or 2, characterized in that the element is a cable element. 5. Apparatus according to claim 1 or 2, characterized in that the element is a transformer element. 6. Apparatus according to claim 1 or 2, characterized in that the element at least plastic film as an insulating material having. 7. Apparatus according to claim 6, characterized in that the plastic film is a polypropylene film. 8. Apparatus according to claim 3, characterized in that the dielectric of the capacitor is a polypropylene film having. 9. Apparatus according to claim 3, characterized in that the dielectric of the capacitor is a combination of Has polypropylene film and insulation paper. 10. The device according to claim 3, characterized in that the dielectric of the capacitor is an insulating paper having. 11. Electrical insulating oil having a composition, characterized in that the composition is the Structural formula η having. 030012/0749 12. Electrical insulating oil »characterized in that the oil is a mixture of a first composition with the structural formula IH ₂ CH ₃ and from a second composition having the structural formula I ^ 2 "5 GII ₃ 0300 1 2/0749