CS202905B1 - Electric condenser particularly the capacitous type - Google Patents

Description

SUMMARY OF THE INVENTION The present invention relates to electrical capacitors, in particular power type, in which the liquid insulator forming the solid dielectric impregnant is a mixed mineral mineral oil based product. The purpose of the invention is to improve the technical and technological parameters of these capacitors, in particular the power types, to increase their lifetime and operational reliability, together with an improvement in their specific characteristics, while manufacturing is to be simple, economical and environmentally friendly.

In addition to the various types of capacitors with conventional paper dielectric and oil impregnants, whose certain indisputable advantages, but also various drawbacks, are well known. Also produced are types with special solid dielectrics and liquid impregnants, where the liquid insulating components consist of a] synthetic liquids, a mixture of these with a mineral oil content) or mixtures with different polymeric additives, which are used here mainly for their lowering surface tension effects of the liquid system. to increase the electrical impact strength, stability under long-term thermal-voltage loading, to increase compatibility, to reduce interactions with the rigid insulation component in the case of some rigid synthetic film dielectrics. The disadvantage of these solutions, however, is the fact that by their application they achieve the required improvement for the needs of practice only to a limited extent, the improvements are only partially, one-sided and mostly associated with the simultaneous deterioration of other important characteristics or parameters. essential becomes more demanding, technically, technologically and economically less effective. This has led to the search for and implementation of further solutions, and it can be stated that, as a result, this is currently the case; became one of the most widespread types, especially in power capacitors, those where, instead of oil, the liquid insulating components are impregnants based on stabilized chlorinated diphenyls. These species exhibit certain indisputable advantages and advantages. This is mainly due to the non-flammability of their impregnating component, its higher permittivity, chemical stability, and at the same time the cost of this component is relatively advantageous. However, the main drawback is the environmental failure of this impregnating component, its tendency to form decomposition products under partial discharges, unsuitability in the manufacture of self-regenerating capacitors, and the unsuitability and impossibility of being used in combination with some rigid synthetic film, plastics, dielectrics e.g. polystyrene, polycarbonate and other types.

Disadvantages of the prior art are eliminated by the solution according to the invention, characterized in that the liquid insulator of the solid dielectric is a mixed impregnant of mineral insulating oil, preferably a condenser oil, the viscosity of which at 20 ° C is 20 to 100 mm ² s ^-1 , a solidification value of not more than - 30 ° C, a loss factor at 20 ° C of not more than 0,0012, and containing, as a mixed component, a proportion of 0,1 to 75% by weight of the propene polymerization or oligomerization product; 100 ° C 4 to 50 mm ² s ^-1 , density at 20 ° C 0.815 to 0.940 g / cm ³ , electrical strength of at least 20 kV / mm and a loss factor at 90 ° C of maximum 0.002.

The solution according to the invention effectively eliminates the unfavorable properties and effects in the insulating system of capacitors of known classical and special embodiments, which occur here due to the action of decomposition products, in particular hydrogen. It is possible to achieve an increase in the working field values of the electric field and an improvement in the specific characteristics of the capacitors associated with an increase in their service life and operational reliability. The solid component of the insulator, the dielectric of the capacitors, achieves a perfect pre-impregnation with an environmentally friendly component, the loss factor of which is less than 1.10 ² at 90 ° C. Due to the relative permittivity achieved, it is possible to produce high-quality capacitors even with dielectrics whose solid insulator component is made of synthetic foils, for example polyethylene, polypropylene, polycarbonate, or other materials and combinations thereof.

The production of capacitors according to the invention is structurally, materially, technologically and operationally advantageous, simple, economical. The possibility of applying the solution according to the invention is broadly universal, it is given for power capacitors as well as for so-called suppression, pulse, high-frequency, auxiliary starting, resp. even for most special designs to operate at temperatures ranging from -40 to + 90 ° C across the full spectrum of the technically used frequencies.

The envisaged direct user of the invention is the field of electrical production producing electrical capacitors. The availability of materials needed for the realization of new types of capacitors is given immediately, materials are available! under favorable conditions, in sufficient quantities and in the required quality.

Example

To verify the solutions of the invention are evaluated alone najskůr liquid impregnants for the intended types of capacitors, in particular, impregnating 1: minerálnykondenzátorovýolej, the viscosity at 20 "C was 30.7 mm ² s ^d, bodtuhnutia 45 C, the value of loss factor at 20 ° C 0.0012 and density at 20 ° C 0.8920 g / cm ³ ;

impregnant 2: polypropylene, oil having an average molecular weight of 600, a viscosity at 100 ° C of 16.9 mm ² S ^-1 , a density at 20 ° C of 0.8437 g / cm ³ , an electrical strength of 20.8 kV / mm and a loss factor at 90 ° C of 0.00018;

impregnant 3: 25 wt. % impregnant 1 and 75 wt. % additive 2, additivated with 0.3 wt. % antioxidants 4 K -

2,6-di-tert-butyl-p-cresol;

impregnant 4: 75 wt. % Impregnant 1 and 25 wt. % impreg-. nantu 2.

The physico-chemical and dielectric properties of these impregnants which have been found in this context are listed below for the impregnant 1 - 2 - 3 - 4. These are kinematic viscosities at 20 ° C [mm ² s-lj: 30,7 - 120.7 - 390.7 - 65.1; density d ²⁰ 4 [g / cm ³ ]: 0.8920 - 0.8437 - 0.8546 - 0.9785; Flash point in closed crucible PM [° Cj: 149 - 129 - 138 - 145; loss factor [tg delta. 10 ² ]: 2.7865 - 0.01833 - 0.0920 - 1.0550; resistivity [Ohm. m]. 10 ¹⁰ : 1.262 - 26.77 - 23.15 - 4.783; after aging in the presence of air at 80 ° C for 400 hours - loss factor [tg delta. 10 ² ]: 4.1813 - 0.052 - 0.0482 - 1.426; resistivity [Ohm. m]. 10 ¹⁰ : 0.4489 - 1079.6 - 157.86 - 1.4414. The electrical properties, both in the initial state and in the state after the cane aging, are determined at 90 ° C 50 Hz.

From a comparison of the physicochemical properties of the impregnants to be evaluated, it can be seen that the properties of the pure mineral oil, impregnant 1, are most closely related to those of impregnants 3 and 4 which are proposed for the capacitors of the invention. There is the possibility of a good pre-impregnation without the necessity of changing the technology of the capacitor production and without changing the impregnation station. In addition, improved electrical properties are also beneficial here, not only in the original state but also after aging.

Next, we proceeded to verify the already functional properties directly on the model capacitors, whose capacity was

- 6 approximately 10 ^G, and with each impregnant random samples of n = 14 capacitors - series 1 to 4 were used for evaluation.

. On these selections for new condensates; In particular, the ionization threshold values - the initial ionization voltage U _ion , as a measure of the pre-impregnation of the capacitor coil, and the breakdown voltage values of the capacitors U _pr , which limit the magnitude of the operating voltage. In addition, the same selections of n = 14 capacitors across all four series were monitored for changes in the tg delta loss factor that occurred after a 38-day accelerated aging cycle at 80 ° C and a connected 2 kV DC voltage, registering the number of model capacitors that have experienced a breakthrough during the accelerated aging cycle. The results obtained in this way are given below in order of the respective series of capacitors 1 - 2 - 3 —- 4. Mean values of the initial ionization voltage U _ion [kV]: 3,43 - 3,15 - 3,93 - 4.42; breakdown voltage U _pr2 [KV]: 4.79 - 3.98 - 4.61 - 4.73; loss factor tg delta. 10 ² at 60 ° C: 0.056 · - 0.088 - 0.063 - 0.087. The values given refer to the flood state. The mean values after 38 days of accelerated aging at 80 ° C at a connected 2 kV DC voltage were at the tg delta loss factor. 10 ² at 60 ° C: 0.110 - 0.132 - 0.092 - 0.124; number of capacitors in series: 8 - 4 - 2 - 0.

From a comprehensive comparison of the data, we can see the beneficial effect of the mixed impregnant capacitors of the invention in the direction of increased lifetime of these capacitors, which is optimal in particular in the solution of the present invention when impregnant 4 and the corresponding capacitor series 4 are applied.

The mean of the initial tension ioinizácie The _ion capacitor model series 1 was 3.43 kV with a standard deviation of 1.23 kV. For Series 4 capacitors, this value was 4.42 kV with a standard deviation of 0.41 kV. Thus, not only an increase in the observed trait occurred, but also its stabilization expressed in a substantially lower standard deviation of the observed trait. As a result, the ionization in the coil was less, there was no significant destruction of the dielectric and deterioration of its properties, which are expressed by the life of the capacitor. In addition, it can be concluded that the double bonds in the structure of the polypropylene oil molecules: ptispié in the mixture to bind the gases produced by random ionization, e.g. overheating and the like, so that squeezing the polypropylene oil in the impregnant is also directly a stabilizer from this point of view.

Mean values of breakdown voltage, U _pr for series 1 and 4 practically do not differ: 4.79 and 4.73 kV. However, in the statistical processing of the values of the results of the _pr , values were calculated below which, at the selected significance level of 0.01, where the risk of misstatement is 1%, no more than 1% of the values of the monitored capacitors decrease. In the case of Series 1, the critical minimum value is expressed as 0.97 kV, in the case of Series 4 this value is substantially higher, up to 3.65 kV. Thus, the risk of a capacitor breakthrough in the operating mode has decreased substantially and its operational reliability has increased considerably.

These terminals confirmed the lifetime measurements of the capacitors by the accelerated aging method, which showed a significantly longer lifetime for the capacitors of the invention compared to the capacitors with impregnant only from mineral oil or only from polypropylene oil. This illustrates the number of model capacitors that broke out of a total of 14 random samples during the accelerated aging cycle. In the case of Series 1, 8 capacitors were breakthrough, but for Series 4 there was no breakthrough in either capacitor. The series 2 capacitors did not have good pre-impregnation of the coils, which resulted in lower values of mean values of breakdown voltage U _pv , .4,61 kV for series 3 and 3,98 kV for series 2 compared to series 3 and 4 capacitors. lower values of the mean values of the initial ionization voltage Ui _on , 3.93 kV for series 3 and 3.15 kV for series 2. The measured parameters were all the more unfavorable, the higher the viscosity had the liquid impregnant, and this unfavorable effect was manifested by increased number of shifted capacitors 4 pieces of series 2 and 2 pieces of series 3 The capacitors, which remained intact after 38 days of stress, remained virtually unchanged from the original state.

Claims (1)

An electrical capacitor, in particular of the power type, wherein the liquid insulator forming a solid dielectric impregnant is a mineral oil based blend product, wherein the liquid solid dielectric liquid insulator is a mixed mineral oil insulating impregnant, preferably a condenser oil having a viscosity of 20 ° C. 20 to 100 mm ² s ^-1 , pour point not more than -30 ° C, body loss value at 20 ° C not more than 0.0012, and containing 0.1 to 75 percent by weight of propene polymerization or oligomerization product as a blend component, molecular weight of which is 168 to 3000, viscosity at 100 ° C 4 to 50 mm ² s ⁴ , density at 20 ° C 0.815 to 0.940 g / cm ³ , electrical strength of at least 20 kV / mm and loss factor at 90 ° C maximum 0,002.