DE2531392C3 - Electrical insulating fluid - Google Patents

Description

3 °

The invention relates to new electrical insulating fluids, in addition to electrical insulating fluids known type additionally at least one compound selected from the group of monoeyanophenoxybenzenes, Contain monocyanobiphenyls and monocyanoterphenyls and in capacitors, Transformers and all other electrical equipment are used.

It is known that the electrical insulating liquids used to insulate electrical equipment must possess a number of properties in addition to each use adjusted relative dielectric constant a weak initial conductivity and after good resistance to thermal decomposition, low vapor tension, a lower freezing point etc. Numerous substances have already been used individually or in a mixture with one another as electrical Insulating fluids are used, for example mineral oil, chlorinated biphenyls and certain esters organic acids. It is true that these substances have the properties required for their use in electrical devices Totality of properties, but there are very few substances that have all the required properties have at the same time optimally formed, ss For example, electrical insulating wedges have poor conductivity and / or good durability the relative dielectric constant is somewhat weak compared to thermal decomposition, at least for certain uses, you

The increase in the loss factor when operating electrical Apparatus is avoided according to the CIl-PS 343474 that the electrical insulating liquids contain up to 2.35% by weight of 8-hydroquinoline. The relative dielectric constant should be determined by this ds Addition are not affected. Special compounds containing silicon and / or nitrogen as additives for electrical flashovers suppressing insulation

Liquid liquids are known from ClI-PS Γ.35 535.

The invention is based on the object of providing electrical insulating fluids with other additives, which are particularly well suited to the relative dielectric constant of the oil to increase without affecting their durability.

This task is performed by electrical isothermal fluids, in particular for use in capacitors or transformers, which consist of a electrical insulating fluid of a known type and a compound selected from the group monocyanophenoxybenzenes, Monocyanobiphenyls and Monocyanoterphenyls exist.

From the three isomers which can be used according to the invention Of the monocyanophenoxybenzenes, l-cyano-4-phenoxybenzene should be emphasized, the one known compound is with melting point 45 to 47 C ". which, however, the phenomenon of hypothermia may have; their boiling point is 173 ° C / 12 mm Hg; their dielectric constant is 15.0 at 26 (; the vapor tension is sufficiently low to allow use in electrical insulating liquids to allow according to the invention.

The compound is, for example, by reacting copper-l-cyanide with l-bromo-4-phenoxybenzo! in Pyridine according to J.M. Bonnier, J.Court and R.Dufournet (Bulletin de la Societe Chimique de France, 1966, pages 1285-7).

The well-known compound 3-Cyunobiphenyl with Melting point 43 to 45 C can also be used individually or in a mixture with one of the other isomers be used according to the invention; however, 2-cyanobiphenyl or 4-cyanobiphenyl or are preferred Their mixtures are used due to their more easily accessible wedge. The following description relates therefore focus more on these two compounds in detail.

These compounds known per se can be obtained with the aid of working methods known per se for example by allowing copper (I) cyanide to act on a 2- or 4-IIalogenobiphenyl or a mixture thereof, in a polar solvent. Other manufacturing methods for these compounds are described in the literature.

The 2-cyanobiphenyl has a melting point of 32 to 33 C but is generally supercooled. Its density d is 1.100 at 21 C, the dielectric constant 17.60 at 22 C and 14.10 at 90 C. The The melting point of 4-cyanobiphenyl is 85 C, its density d 1.050 is 90 C and its dielectric constant 12.40 also at 90 C. The vapor tension of these isomers is sufficiently low to enable their use in electrical equipment.

As monocyanoterphenyls the o-, in- or p-Tcrphcnyle come into question, which on one of the three nuclei carry a CN substituent, as well as the mixtures of these isomers. Since these isomers are general difficult to separate, they generally liogon in In the form of mixtures, which can be resinous or crystalline. For example, one can produce Copper (i) cyanide act on Monohalogenterphenylc in a polar solvent. Below is an example of an exact working method / ur Production of a mixture of Mcnoeyanoterphenylen specified: Fin rich in o- and m-isomers Mixture of terphenylon is chlorinated li η ti then de-

...- _{t unl} a fraction having a Chlorierungsf d of 1.015 M ^"! Isolate chlorine / mol of terphenyl. ° I ^a collected fraction with copper (l) cyanide Ehrend 40 h reacted at 200 C. Then by distillation, a mixture of isomers η Monocyanoterphenyle isolieu, passes the I · 180 to 200 C under 1.2 mm Hg and the nielektriznätskonstante at 90 C 11 is the thermal and chemical resistance of these rfindungsgemüß to be used Cyanoverbindun- ι ^e _Wurt] e. assessed by examining the evolution of their f tlahigkeit from aging this purpose ine liquid was prepared by dissolving the Cyanorbindungen in a euiektischen mixture of Binhenyl and Perphenylen;. this liquid was Frmere time through subjected to the action of heat 150 C) u ^nler nitrogen atmosphere and eriodisch the dielectric loss factor (tg <5) _{measured under L ^ j 2.} The euiectic mixture of diphenyl and terphenylene is not particularly an unequal dielectric Ctric impregnating agent, but is an interesting carrier material for investigating the stability or resistance of additives because it is very harmful itself and consequently does not affect the results obtained. The following three mixtures were prepared according to the invention:

continuation lg ι) / Λ lg rt / H lg r) 7C Test duration / j _ 22nd 24 161 - 23 ~ 185 16.4 32 34 233 - - 41 282 47 - 3 (M - 38 50 330 50 - 352 - 36 - 377

Mixture A
1. Cyano-4-phenoxy benzene

Eutectic mixture of biphenyl and terphenylene
Dielectric constant i / 90 C

25th

75 5.00

Mixture B

Mixture of the 1 some η of cyanobiphenyl

o-isomer 9.6%
p-isomer

P-ISUHIt. 90.4%

Eutectic mixture of biphenyl and terphenylene
Dielectric constant r / 90 C

72 5.03

Mixture C

2-cyano-biphenyl

Eutectic mixture of biphenyl and terphenylene

Dielectric constant r / 90 <

The measurement results are summarized in the table below. ₍

Table 1

25th

75 5.02

Test duration
H

tu (5 / C

0
I. 6.4 5, H.
4.7 11.5 I.
Ί - 16 7.5 12th
12th 16.8 2 s
4!
65 l) 14th
15.5

17 The list shows that the compounds examined have sufficient stability and This is all the more so since the test temperature was higher than the usual usage temperatures.

According to the above-described cyano compounds in a mixture with electrical Known type of insulating fluids used; this includes, for example, mineral oil, castor oil, chlorobiphenyls, aromatic hydrocarbons and their alkylates, esters of organic acids, for example Esters with aromatic cores, aliphatic esters, in particular 2-ethylhexyl-2-ethylhexanoate. Especially It is advantageous to use these compounds together with other fluids, for their part have a weak or low dielectric constant. But of course they know insulating liquids can also be added, which have a relatively high dielectric constant, whereby this addition then increases the total dielectric constant of the mixture to the desired value is set. How much cyano compound is used depends on the dielectric constant the selected value of the end product. In general it can be said that one or the other of these Isomers make up 3 to 50% by weight of the final mixture can. In this way one obtains a range of insulating liquids, the numerous Meet the requirements of use.

If a mixture of cyano compounds is used, the choice of the different substances depends apart from their relative solubility in the electrical insulating fluid of the known type. Lis is very convenient and it is therefore preferred to start from mixtures such as those obtained from technical starting materials, for example in the case of the monocyanobiphenyls starting from the technical mixtures of 2-1 IaIogenbiphenyl and 4-llalogenbiphenyi.

The electrical insulating liquid according to the invention, Wedges are made by simply mixing the components at a temperature at which the cyano prevention » is liquid, preserved and often prior to its use one common in the dielectric field Subjected to pretreatment, for example with activated earths.

You can also use electrical insulating fluids Customary additives may be added, for example substances that reduce the surface tension reduce the liquid like silicone oils, AiUis oxidants or also cleaning substances such as

Epoxies
Below are a few examples of initiation

Appropriate composition given.

example 1 The following mixture was prepared:

Containing dichlorodiphenyl-i-fraction

75% w / w 2,4-isomer 64% w / w /,

Eutectic mixture of bipheny!

and terphenyl 31% by weight

1-cyano-4-phenoxybenzene 5 wt .- 'i' "

This electrical insulating liquid had a dielectric constant of 5.05 at 90 (. After aging at 150 for 50 hours, the dielectric losses (tg S) measured at the same temperature were below 50 II / 12% (0.12).

Example 2

A mixture was prepared from 75% by weight of eutectic biphenyl-terphenyl mixture and 25 wt% 1-cyano ^ phenoxybenzene. The relative Dielectric constant was 5.0 at 90 (; the dielectric losses of this liquid changed little with the Zeil.

Example 3

By mixing 92 parts by weight of diotyl phthalate and 8 parts by weight of 1-cyano-4-phenoxybenzo! received a liquid with a relative dielectric constant of 5.0 at 90 C.

Example 4 The following mixture was prepared:

Dioctyl phthalate 80% by weight ¹ ',' ,,

Mixture of o- and p-cyanobiphenylc. containing 9.6%. o- and 90.4% p-isomer 20 wt .- ", · ;.

The viscosity of this liquid was 9.6 cSt at 60 C and 4.6 cSt at 90 C, dielectric constant 6.16 at 90 C. After aging for 500 hours at 150 (under nitrogen, the value of the loss angle had changed stabilized at 150 C and below 50 Hz at 98% (0.98); this is sufficient stability or Resistant wedge for practical applications.

Example 6
Hs was made from a mixture

2-ethylhe \ yl-2-ethylhexanoate
o-cyanobiphynyl

80 cicw.-20 wt.

Example 5 Fs the following mixture was prepared:

Diisobutyl phthalate 80 parts by weight ^'1 / ,,

Mixture of o- and p-cyanobipheny!

(9.6% o- and 90.4% p-isomer) 20 wt .- "/;

The viscosity of this mixture was 6.85 cSl at 60 C; the dielectric constant was 7.26 at 90 c. The viscosity of this mixture was 1.34 cSl at 90 (; the dielectric constant was 4.71 at 90 <.

Example 7

A mixture was prepared which contained 7t) wt. euclical mixture of bipheny! and terphenylene

is and 30 C) Cw .-% mixture of isomeric monocyanoterphenyls with boiling point 180 to 200 (71.2 mm 11g and dielectric constant 11/90 (contained.

This mixture had a viscosity of 5 cSt, a dielectric constant also at

jo 90 C of 4.8 and a loss factor tg δ at time / = 0 at 150 C under 50 Hz = 8% (0.08). Some possible uses of the electrical insulating liquids according to the invention are explained below with reference to the drawing.

1 shows an element of a wound capacitor consisting of the two electrodes in the form of foils 1 and 2 made of aluminum or another Metal separated by the insulating layers 3 and 4. The insulating layers in turn exist

ν from paper foils or from plastic foils or else made of a laminate such as two polyolefin films with a paper layer in between. Tongues 5 and 6 are the power connections. Fig. 2 shows in section a capacitor bc-

is standing out of the metal container 1 with a tight-fitting Ceiling! 2, a wound capacitor element 3. as shown in FIG. 1, from connection points 4 and 5. which connect the armatures of the winding capacitor to the outer terminals 6 and 7.

The capacitor pan is filled with the liquid dielectric according to Example 1. This impregnates the dielectric material and fills the gaps and spaces in the entire device.
Fig. 3 shows a transformer with a high-voltage terminal 1, a NicderspannungsklemmeZ. the transformer housing (tub) 3, ßefestigungsflanschen 4, insulating walls 5 and 6, the low-voltage winding 8 and the magnetic core 10 on the one hand and the high-voltage winding 9 and the

so separate transformer housing on the other hand. The parts marked 7 are insulating spacers. The low voltage and high voltage coils are made from a solid dielectric material for example paper isolated.

The transformer housing was filled with the (ic mix according to Example 6, which filled all empty spaces and cavities and penetrated the vetch! and other impregnable parts of the device.
Of course, the following can be used:

the provided electrical insulation fluids also for all other forms of filling in known devices apply.

llici / u 2 sheets

Claims (4)

Patent claims: 1. Electrical insulating fluid, especially for use in capacitors or transformers gates, consisting of an electrical insulating liquid of known type and a connection selected from the group consisting of monocyanophenoxybenzenes, monocyanobiphenyls and monocyanoterphenyls. ι ο 2. insulating liquid according to claim 1, characterized in that it contains 2 to 50% monocyanophenoxybenzenes, Contains monocyanobiphenyls and / or monocyanoterphenyls. 3. Insulating liquid according to claim 1 or 2, there- is characterized in that it is known as an insulating liquid Ar! Mineral oil, castor oil, a chlorobiphenyl, Contains esters of organic acids or aromatic hydrocarbons and their alkylates. 4. insulating liquid according to any one of claims 1 to 3, characterized in that it contains usual additives, especially to reduce the surface tension of the liquid, antioxidants or contains cleaning substances.