FI63129B - ELEKTRISK APPARAT MED FOERBAETTRAT DIELEKTRISKT SYSTEM - Google Patents

Description

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Patent and Registration Office The Public Utilities were published on December 31, 1982 (32) (33) (31). , Illinois, USA (72) John Lapp, Franklin, Wisconsin, Fred S. Sadler, Racine, Wisconsin, USA (74) Oy Kolster Ab (5U) Electrical device with improved dielectric system - Elektrisk apparat med förbättrat dielektriskt system

The present invention is directed to an electrical device, such as a capacitor, having an improved dielectric system. The capacitor includes alternating layers of a metal film and a dielectric material, wherein the dielectric material consists of a combination of a polymer film and paper impregnated with a liquid dielectric composition containing a mixture of monohalogenated diphenyloxide and a monohalogenated alkyl di-phenyl oxide group, wherein The corona properties of the capacitor are improved and its dielectric losses are small and the liquid dielectric composition is substantially biodegradable.

In the manufacture of capacitors, such as power factor correction capacitors, capacitor packs are formed of alternating layers of a metal film and a solid dielectric material, whereby the dielectric material is impregnated with a liquid dielectric rubber.

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In the past, kraft paper was commonly used as a dielectric material, and the dielectric losses of this type of capacitors were relatively large, limiting their use to capacitors of 100 kvar and smaller.

A combination of paper and a polymer film such as a polypropylene film has also been used as a dielectric layer in capacitors. The dielectric losses of the paper-film capacitor are substantially lower than that of the paper capacitor alone and its reliability is better, allowing its use in capacitors with higher quartz capacity. Paper into paper in a vo dielectric layer imposes certain limitations, but acts as an absorbent material to improve capacitor saturation with liquid dielectric rubber.

For several years, polychlorinated diphenyls have been used as a liquid dielectric rubber in power factor correction capacitors, and this dielectric rubber muddy an efficient dielectric system that has made several improvements to capacitors possible. For example, in recent years the housing volume per kvar has decreased by a factor of about 8, dielectric losses have decreased by a factor greater than 5, the cost per kvar has decreased by a factor of about 2. These improvements are due, at least in part, to the use of polychlorinated diphenyls in liquid form. impregnating agent.

Although polychlorinated diphenyls, such as trichlorodiphenyl, form an efficient dielectric system for the capacitor, their use has posed certain ecological problems because some polychlorinated diphenyls are in fact non-biodegradable, so if pollution of the environment and does not decompose in significant amounts, even over several years. Another drawback is that polychlorinated diphenyls tend to bioconcentrate in animals and have been shown to be toxic.

The invention relates to an electrical device, such as a capacitor with an improved dielectric system, and to a method of manufacturing a capacitor. The capacitor comprises alternating layers of a metal film and a dielectric material consisting of a combination of a polymer film and a paper. The dielectric material is impregnated with a liquid dielectric composition containing a mixture of monohalogenated diphenyloxide and monohalogenated alkyldiphenyloxide, wherein the alkyl group contains 1 to 20 carbon atoms per molecule. The liquid dielectric composition generally contains 3,631 29 to about 5 to 95 weight percent monohalogenated diphenyloxide and 95 to 5 weight percent monohalogenated alkyl diphenyloxide. In addition, the dielectric composition may contain 0.01 to 10% of an epoxy compound that acts as a cleaning additive to neutralize chlorine ions or other decomposition products formed or released from the impregnating agent or other materials in the condenser during use.

The polymeric material may be made of a material such as polypropylene, polyethylene, polyester or the like, and the surface of the film and / or the opposite surface of the metal film may be provided with rougheners for a liquid dielectric material to achieve complete saturation of the film during liquid treatment.

In the manufacture of a capacitor, the capacitor housing containing the solid dielectric layer is dried under vacuum at a temperature below 60 ° C, preferably at room temperature, for a time sufficient to remove water vapor and other gases from inside the capacitor. The liquid dielectric rubber is recycled or otherwise mixed under vacuum to remove gases from it. After separate degassing of the capacitor and the dielectric liquid, the liquid is placed inside the capacitor. When the capacitor is filled, the liquid is placed under vacuum or pressurized at a temperature below 60 ° Csb, preferably at room temperature. After impregnation, the vacuum is removed and the condenser is sealed.

The dielectric losses of the capacitor according to the invention are small and its corona properties are excellent at temperatures in the range of -40 ° C to + 90 ° C. An additional advantage is that the liquid dielectric composition is less hazardous to the environment than polychlorinated hydrocarbons because it is less toxic, has less biodegradation to living organisms, and has a higher biodegradability than polychlorinated diphenyls.

The dielectric system, manufactured by the method of the invention for removing gases from the dielectric system, is capable of operating under elevated temperatures of up to 125 ° C without dispersion of the polymer layers or liquid dielectric rubber. Improved stability at elevated temperatures allows the use of a dielectric system in large power factor correction capacitors, which typically have an operating temperature range (enclosure temperature) of -40 ° C to + 70 ° C, as well as smaller equalization or special capacitors, whose operating temperature can always rise up to 100 o.

As a further advantage, the method according to the invention eliminates the need for post-treatment, which has often been necessary when using conventional manufacturing methods. Usually, the elimination of the post-treatment up to 72 hours substantially shortens the total manufacturing time of the capacitor, thus reducing the manufacturing cost.

Other objects and advantages will become apparent from the following presentation. Fig. 1 is a perspective view of a capacitor made according to the present invention, Fig. 2 is a perspective view of a capacitor pack, Fig. 3 is a graph showing the solidification points compared to a paper-film capacitor using chlorinated diphenyl as a impregnating agent in the prepared paper-film capacitor.

Figure 1 shows a typical capacitor comprising an outer shell 1 with side walls 2, a base 3 and a cover 4. In use, the housing 1 is hermetically sealed and is provided with a small closure hole 5 through which dielectric liquid is added to the housing during manufacture. In addition, a vacuum tube can be connected to the hole 3 for vacuum drying of the capacitor during manufacture. A pair of connection terminals 6 extend through the cover and have them isolated from the cover.

An array of capacitor packs 7 is housed in the housing 1, and each capacitor pack, as shown in Fig. 2, comprises wound metal film layers 8 separated by a dielectric layer 9. The electrodes are attached to the metal foil layers 8 and the electrodes of the different constraints are connected in series for final connection to the terminal 6.

The metal film layers 8 may be formed of any desired electrically conductive material, generally a metal such as aluminum or the like. The layers 8 may be flat sheets or surface roughening such as compression deformations on one side of the film and corresponding protrusions on the other side may be formed on the layers, as disclosed in U.S. Patent 3 * 746,933.

The solid dielectric layers 9 consist of combinations of a polymeric film such as polypropylene, polyethylene, polyester or polycarbonate and a fibrous cellulosic material such as kraft paper, absorbent paper, absorbent wood fiber materials and the like. The polymeric films may be in the form of smooth-surfaced strips or may be a polymeric sheet such as polypropylene having a thin layer of polyolefin fibers attached thereto, as disclosed in U.S. Patent 3,772,578.

The polymer film generally consists of up to 90% by weight of the dielectric layer and in most cases 30 to 90% by weight, preferably 70 to 85% by weight of the dielectric layer.

It is important that there are irregularities or deformations in the surface of the polymer film and / or in the surface of the opposing metal film 8 that the two opposing surfaces are not in constant close contact with each other. The irregularities on the surface provide a suction or capillary effect for the liquid dielectric, allowing the liquid to be completely saturated during the treatment of the film 9.

The dielectric layers 9 are impregnated with a liquid dielectric composition containing a mixture of monohalogenated diphenyloxide and monohalogenated alkyldiphenyloxide, wherein the alkyl group contains 1 to 20 carbon atoms.

The monohalogenated diphenyloxide is used in an amount of about 9 to 95% by weight of the mixture, with the monohalogenated alkyl diphenyloxide forming the remainder. In many applications, monohalogenated diphenyloxide is used in an amount of 10 to 70% by weight of the composition, with the remainder being monohalogenated alkyl diphenyloxide.

In both components, chlorine is the preferred halogen, although other halogens such as bromine may be used. The halogen atom is usually located in the para position in both components, and in a typical process for the preparation of compounds, about 80 to 100 percent of the halogen atoms are in the para position, with the remainder 0-20 percent in the ortho position.

The alkyl group of the monohalogenated alkyl diphenyloxide preferably contains 3 to 16 carbon atoms and may be either straight-chain or branched, and the particular position and number of branches is not critical to the invention.

Specific examples of the dielectric composition that can be used in the capacitors of the invention include: 50% mono-bromodiphenyl oxide and 50% mono-chlorododecyldiphenyloxide; 30% monochlorodiphenyl oxide and 70% monochlorododecyl diphenyl oxide; 80% monochlorodiphenyl oxide and 20% monochlorohexyl diphenyloxide; 40 TL monochlorodiphenyl oxide and 60% monochlorobutyl diphenyl oxide; 20% monochlorodiphenyl oxide and 80% monochloropropyl diphenyl oxide; 35% monochlorodiphenyl oxide and 65% monochlorohexyldiphenyloxide; 17 Z mono-chlorodiphenyl oxide and 83% mono-chlorobutyldiphenyl oxide.

The dielectric composition may further contain 0.01 to 10% by weight, preferably 0.2 to 1.5% by weight, of an epoxide cleaning additive which neutralizes the decomposition products released or formed from the liquid impregnating agent and other materials in the condenser during its use. Neutralizing agents or cleaning agents are in the form of 1,2-epoxy-3-phenoxypropane; bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate; 1-epoxyethyl-3,4-epoxycyclohexane; 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane carboxylate; 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate and mixtures thereof. Epoxy compounds are able to effectively neutralize decomposition products, thus improving the dielectric properties of the capacitor and its service life.

Monohalogenated diphenyloxides can be prepared by conventional methods using halogenated diphenyloxide using an aluminum halide such as aluminum chloride or other protic acids to give a mixture of o- or p-halo-diphenyloxide, as disclosed in U.S. Patent 2,022,634.

Similarly, monohalogenated alkyl diphenyloxide can be prepared by known methods, wherein the halodiphenyl oxide is treated with a small amount of aluminum chloride, followed by the gradual addition of the alkyl halide or olefin while maintaining the reaction mixture at the reaction temperature as disclosed in U.S. Patent No. 2,170,989.

No particular procedure is required to mix the two ingredients and can be mixed at room temperature or at elevated temperatures. Alternatively, the mixture can be obtained by an alkylation process, in which case the alkylation is terminated after a sufficient time to obtain the desired ratio of mono-halogenated alkyldiphenyloxide to mono-halogenated diphenyloxide. When using this procedure to obtain lower alkyl alkylation, a small percentage of di-alkylation may occur.

To manufacture a condenser according to the invention, a vacuum or vacuum is initially created inside the condenser housing containing the condenser pack for a time sufficient to remove water vapor or other gases from inside the condenser. A vacuum is formed inside the housing 1 by connecting a line between the vacuum device and the hole 5. Usually a vacuum of less than 100 micrometers and preferably less than 30 micrometers and longer than .40 hours of vacuum drying period is conventional, although the time depends on the size of the vacuum.

In order to prevent molecular expansion of the polymer film, the temperature must be kept below 60 ° C and vacuum drying is preferably performed at a temperature below 43 ° C, such as room temperature. from low-concentration areas until equilibrium is reached. It has been found that heating the polymer film adversely affects the diffusion rate due to the expansion of the molecular structure. When heated, it is important to avoid heating the polymer film to a temperature above 60 ° C when drying the capacitor.

The dielectric liquid is separately subjected to a vacuum drying treatment to remove gases from the liquid dielectric rubber. The degassing treatment uses a vacuum below 500 micrometers and a vacuum below 50 micrometers is recommended. The time of vacuum drying of the liquid should be sufficient to remove the gases from the liquid. In order to accelerate the removal of gases, it is advantageous to circulate the liquid either by circulating the liquid or by mixing it. The removal time of the gases depends on various factors such as the viscosity of the liquid, the size of the vacuum, the method of mixing and other factors. Generally, the duration of the vacuum drying treatment for the liquid is longer than 12 hours.

During the vacuum drying treatment, the liquid is preferably kept at room temperature. Heating can be used, but the temperature of the liquid released from the gases must be below 60 ° C and preferably below 43 ° C when added to the condenser. The degassed liquid dielectric rubber is added to the capacitor housing 1 by means of a tube attached to the hole 5 while maintaining a vacuum. After filling the capacitor housing, a vacuum of less than 100 micrometers and preferably less than 30 micrometers is applied to the liquid for a time sufficient to completely impregnate the solid dielectric layers with the dielectric liquid. In most cases, impregnation times longer than 24 hours are used. During this period, the temperature of the solid dielectric layers in the capacitor and the temperature of the dielectric liquid are kept below 60 ° C and preferably below 43 ° C, such as at room temperature.

Alternatively, after filling, a vacuum of 0.07 to 0.28 3 kp / cm can be applied to the liquid dielectric rubber in the capacitor to improve the saturation of the solid polymer layers. Normally, pressure is applied to the dielectric fluid for more than 30 minutes. The manner in which the pressure is applied to the liquid is not critical, although it is recommended not to use a pressurized gas in direct contact with the liquid, as the gas can be absorbed into the liquid and the absorbed gases have a detrimental effect on the dielectric properties of the system.

After the impregnation or absorption cycle, the vacuum or pressure, if used, is removed and the condenser is closed.

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In the past, post-treatment has often been used, in which the sealed condenser was heated to a temperature of about 85 ° C for up to 72 hours to improve saturation and achieve better reliability. The post-treatment procedure is not required when using the method according to the invention, although the post-treatment can be used without adverse effects, but it substantially prolongs the total preparation time. By eliminating post-processing, a considerable reduction in manufacturing time can be achieved and this is important for production reasons.

It has been found that the liquid dielectric composition used in the capacitor of the invention more easily saturates the polymer film than conventional impregnating agents such as trichlorodiphenyl. This increase in saturation rate is dependent on the surface energy of the composition and also depends, at least in part, on the relatively low viscosity of the composition. An increase in saturation rate can cause significant time savings in capacitor fabrication.

The relative dielectric constant of the liquid dielectric composition used in the electrical device according to the invention is considerably smaller than the dielectric constant of polychlorinated diphenyls; for example, a mixture containing 17% monochlorodiphenyl oxide and 83% monochlorobutyl diphenyl oxide has a relative dielectric constant of about 4.4 while capacitor grade trichlorophenyl has a relative dielectric constant of about 5.9. This significant difference in relative dielectric constants could be expected to result in poor choice of dielectric composition of the invention compared to capacitor-grade polychlorinated diphenyls, since the relative dielectric constant usually directly determines capacitance and this lower relative dielectric constant could be expected to result in a larger volume. However, it has been unexpectedly found that the use of the dielectric composition of the invention in combination with a solid dielectric paper-film combination does not cause a significant reduction in capacitance compared to a similar capacitor impregnated with polychlorinated diphenyls.

In comparison, a capacitor having only a paper dielectric layer and impregnated with a dielectric composition according to the invention operates as expected so that the capacitance is reduced compared to a whole paper capacitor impregnated with polychlorinated diphenyl.

Thus, a full paper capacitor impregnated with a composition of the invention would have to be made to be about 20% larger in volume than a polychlorinated diphenyl impregnated whole paper capacitor or electric box supports.

It has been found that if a polymer blend such as polypropylene is impregnated with a polychlorinated diphenyl such as trichlorodiphenyl, the relative dielectric constant of the polymer blend increases slightly. However, quite unexpectedly, the relative dielectric constant of the polymer film increases considerably when impregnated with the dielectric composition of the invention, so that the relative dielectric constant of the film impregnated with the dielectric composition of the invention is slightly greater than compared to about 5.9 polychlorinated diphenyl. Even when adding 25 to 50 paper to a dielectric system using the composition of the invention, there is only a decrease in capacity of about 1% compared to an identical system using capacitor-grade polychlorinated diphenyl. This corresponds to the expected 5-6% decrease in capacitance calculated from the relative dielectric constants of the materials. Thus, although the relative dielectric constant of the liquid of the invention is significantly lower than that of polychlorinated diphenyl, the capacitance of the paper-film capacitor impregnated with the dielectric composition of the invention is comparable to the capacitance of a capacitor using polychlorinated diphenyl.

The composition of the invention, although monochlorinated, forms a stable system. Traditionally, stability has been associated with increased chlorination, but it has been found that the liquid dielectric system of the invention provides a stable system comparable to that obtained with trichlorod-phenyl and tetrachlorodiphenyl. In addition, a lower degree of chlorination is a clear advantage, making the compositions more biodegradable, less toxic, and less prone to bioconcentration in living organisms.

The liquid dielectric composition is substantially completely biodegradable, which means that if the dielectric composition is released into the environment due to leakage or rupture of the housing or disposal of obsolete capacitors, the liquid dielectric rubber decomposes into harmless compounds without significant harm to the environment. On the other hand, capacitor-grade polychlorinated diphenyls have been found to persist in the environment and are not readily biodegradable.

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Polychlorinated diphenyls have also been found to be bioconcentrated in fish and animals and to be toxic. By comparison, the dielectric fluid of the invention is less hazardous to the environment because it is less bioconcentrated in a living organism and less hazardous to fish and mammals. For example, capacitor-grade polychlorinated diphenyls are bio-enriched in fish 100 to 200 times as much as a mixture containing 17% by weight of monochlorodiphenyl oxide and 83% by weight of monochlorobutyldiphenyl oxide. In addition, the oral acute toxicity of capacitor-grade polychlorinated chlorines is about 10 times higher than that of the dielectric liquid composition of the invention.

An important point in capacitor design is the partial discharge voltage (DIV). It is important that the dielectric rubber is not allowed to operate under conditions of partial breakthroughs, as the dielectric system will deteriorate in the presence of such partial discharges and the service life of the system will be significantly shortened Tavast i.

Curve 3 shows the values of the pour points of the mixtures of mono-chlorodiphenyl oxide and mono-chlorododecyldiphenylox obtained under experimental conditions at which the temperature was constant for several hours before the readings were determined. As can be seen from this curve, chlorododecyldiphenyloxide alone has a solidification point of about 0 ° C and pure monochlorodiphenyloxide has a crystallization point of about -18 ° C. However, contrary to expectations, the pour point of the mixture of the two substances is lower than that of either component alone. For example, a 50:50 mixture of two ingredients has a pour point of about -45 ° C and most mixtures have pour points well below -20 ° C.

Since capacitors can be exposed to very low ambient temperatures during use, it is desirable that the solidification point of the dielectric fluid be low. The reduced pour point provided by the mixture of the two components ensures that the liquid dielectric rubber does not crystallize and remains in the liquid state throughout the operating temperature range of the capacitor.

The solidification point of the dielectric fluid according to the invention is lower than that of capacitor-grade polychlorinated diphenyls. As a result, the capacitor according to the invention can be used up to a temperature of -45 ° C and even at a temperature as low as -60 ° C, depending on the mixture of ingredients used in the liquid dielectric rubber.

It has been found that the reliability of most dielectric systems at low temperatures is relatively poor. Dielectric systems which have been allowed to stabilize under electrically loaded conditions at very low temperatures are particularly prone to premature damage, especially if the system is switched on at very low temperatures. It is therefore important that the losses of the dielectric system at low temperatures are high, as high Thus, the dielectric loss properties of the dielectric system of the invention meet the basic requirements, being high at low temperatures, thus improving reliability.

The DIV value of the film-paper capacitor according to the present invention impregnated with the dielectric liquid according to the invention is higher in the conventional operating temperature range than that of the corresponding capacitor using polychlorinated diphenyl as an impregnating agent. To demonstrate this, a series of capacitors were fabricated using two sheets of 12.5 micrometer electrical grade polypropylene film separated by a single sheet of 9 micrometer kraft paper as dielectric layers (74% polypropylene film and 26% kraft paper). This laminated dielectric rubber was placed between an aluminum foil with a nominal thickness of 6.15 micrometers.

A group of capacitors were impregnated with capacitor-grade polychlorinated diphenyl (Aroclor 1016, which is essentially a mixture of trichlorodiphenyl and tetrachlorodiphenyl) and 0.5% by weight of the epoxy additive bis (3,4-epoxy-6-methylcyclohexylmethyl).

Another group of capacitors was impregnated with a dielectric liquid according to the invention, which was a mixture of 17% by weight of monochlorodiphenyl oxide and 83% by weight of monochlorobutyldiphenyl oxide and 0.5% by weight of the same epoxide additive.

All capacitor samples were dried in a vacuum oven at 105 ° C for 48 hours with a vacuum of less than 100 micrometers. In each case, the dielectric liquid was dried separately under vacuum at 20 ° C for 48 hours with a vacuum below 100 micrometers. The capacitors were cooled to 60 ° C and the dielectric liquids were added to the housings and allowed to soak for 72 hours at 60 ° C, applying a vacuum of less than 100 micrometers to the liquid. After this impregnation period, the vacuum was removed from each sample and the capacitors were sealed.

Capacitor samples were used in all cases electrically loaded at room temperature for 24 hours at 1800 volts per 25.4 micrometer. After this period of use, the DIV value was determined for different temperatures

In patients between -45 ° C and + 90 ° C. The results of this experiment are shown in Figure 6.

Figure 6 shows DIY values as a function of temperature for film-paper capacitor samples impregnated with polychlorinated diphenyl and a dielectric composition according to the invention.

As can be seen from Figure 6, the DIV values of the capacitors made according to the invention are higher in the conventional operating temperature range than those of the capacitors in which polychlorinated diphenyl was used as the impregnating agent. In addition, the characteristic depression at -20 ° C to 0 ° C that occurs with capacitors using polychlorinated diphenyl is not present in the samples impregnated with the dielectric composition of the invention. The absence of this characteristic depression is important because an increased safety limit is achieved, which ensures that the normal operating stress is well below the corona voltage or, if the system safety factor is kept approximately the same as that used with polychlorinated diphenyl, higher stresses can be used. This gives a capacitor whose volume is smaller by the same kvar value.

These experiments show that a capacitor according to the invention with a DIY value greater than 60 kV / mm can be constructed at all temperatures between -40 ° C and + 90 ° C.

The film-paper capacitor of the present invention is also stable under operating conditions. The stability and reliability of the system are indicated by the values in Table 1 below. In these series of experiments, sample capacitors were fabricated using two 19 micrometer polypropylene films and one 9 micrometer sheet of sheet paper as a dielectric material, and this laminated structure was placed between aluminum films with a nominal thickness of 6.5 micrometers.

The capacitors were saturated with a mixture of 17β-mono-chloro-diphenyloxide and 85% of mono-chlorobutyldiphenyl oxide. In addition, 0.5 io of epoxy additive (EHL-4-4289) was used. · KalYo paper-capacitor samples were treated in the same manner as described above for SXY temperature experiments.

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Table I

Sample no * Initial DIV reading DIV value DIV value after 192 hours of operation DIV value after 192 hours _ kV / 25.4 nm_ at 1800 V. After 2100 V

a 1.86 2.14 kV / 25.4 jm 2.35 kV / 25.4 pb 2.11 2.19 "2.35 o 1.83 2.05" 2.21 "d 1.62 2, 22 "2.38 e 2.05 2.22 M 2.38 f 2.03 2.30" 2.38

Avg. 1.92 2.17 "2.34

Table I shows the initial DIV value, the DIV value after 192 hours of operation at 1800 volts in kilovolts per 25 * 4 micrometers and the DIV value at 192 hours at 2100 volts in kilovolts per 25f4 micrometres.

As can be seen from Table I, operation under electrically loaded improves DIV values, which is important as it shows that the system does not deteriorate, but in fact improves under electrically loaded.

The capacitors of the capacitors according to the invention have a relatively high DIV value over the entire operating temperature range, thus giving good overall properties and having low dielectric losses. Higher DIV values provide an improved safety margin, ensuring that the number of volts per millimeter is well below the DIV value, allowing the number of volts per millimeter to be increased safely.

Claims (12)

1. An electrical apparatus provided with a pair of electrically conductive elements positioned in spaced relation to each other and suitable to provide an electrical potential between them, and a dielectric system located between said element, as may be noted, that said dielectric system has a dielectric material composed of polymeric film and cellulose fiber materials, and a liquid dielectric composition impregnated in said dielectric material, said dielectric composition comprising a mixture of monohalogenated diphenyl oxide and monohalogenated alkyl diphenyl oxide, wherein the alkyl group contains 1 carbon atoms 1 molecule. Apparatus according to claim 1, characterized in that said dielectric material is composed of 30-90 wt-56 polymeric film and 70-10 wt6 of said cellulose fiber material. Apparatus according to claim 1, characterized in that the polymer coating film is polypropylene film and the cellulose fiber material is paper. Apparatus according to any one of claims 1-3, characterized in that the monohalogenated diphenyloxide is present in an amount of from 5 to 95% by weight of the mixture. Apparatus according to any one of claims 1-4, characterized in that the dielectric composition has a lowest flow temperature below -20 ° C. Apparatus according to any one of claims 1-5, characterized in that the composition includes an epoxide cleanser in an amount of 0.1-10% by weight of said mixture, and that said epoxide cleanser is selected from the group consisting of 1,2 epoxy. -3-phenoxypropanebis (3,4-epoxy-6-methylcyclohexylmethyl) adipate # 1-epoxyethyl-3,4-epoxy-cyclohexane 3,4-epoxy-cyclohexylmethyl-3,4-epoxy-6-methyl-cyclohexanecarboxylate; and mixtures thereof. Apparatus according to any one of claims 1-6, characterized in that the halogen in said mono-halogenated diphenyloxide is bromine and the halogen in said mono-halogenated alkyl diphenyloxide is chlorine. Apparatus according to any one of claims 1-7, characterized in