CS212876B1 - Electrical insulating non-slip impregnant overlay paper insulation of high-voltage power cables - Google Patents

Abstract

Electrically insulating, non-flowing impregnator for layered paper insulation of high-voltage power cables. Non-flowing mixed impregnator based on mineral oil, specific amorphous polypropylene and petroleum wax. The impregnator is suitable for high-voltage power cables intended for routes with larger height differences, or intended for vertical installation. The invention can be used primarily in cable plants, where the relevant types of high-voltage, especially 22 and 35 kV power cables with classic impregnable insulation are manufactured.

Description

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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroinsulating non-slip impregnants for laminated paper insulation of high-voltage, high-current cables of conventional construction. These are types where the average life expectancy usually exceeds 30 years. The purpose of the solution is to obtain a new type of non-slippery impregnant of suitable properties, which is more advantageous compared to the current technology, technologically and economically.

By impregnating the paper insulation with suitable oil-type materials, its electrical, breaking strength is increased to 10 to 15 times. In conventional power cables with laminated paper insulation impregnated with a conventional oil-based impregnant deposited on routes with a higher height difference, as well as conventional operating cycles, exhibiting alternating heating with cooling, the impregnant migrates and flows radially and axially along the paper insulation. In this way, impregnated spaces and voids, cavities in the insulation, in which ionization is generated, are gradually produced by impregnant, resulting in an electrical cross-section of the cable. Practical limits of acceptable height differences on a conventional cable route range from about 5 to 14 meters. for example, in ČSN37 5054. These constraints cannot be compensated by using even the highest quality impregnant types. For cables designed for routes with higher altitude differences or to install vertically, it is necessary to use specifically, so-called non-slippery impregnants, usually also referred to as "non draining comoupounds". Barbecue types of such impregnants have been developed and are available, based on both natural and synthetic materials and mixtures thereof, using a variety of raw materials.

Moreover, impregnants of this type require, in addition to the usual requirements, ie their suitability from the point of view of technical, technological, economical, efficiency of their use, price and availability of the necessary raw materials, to have very good electrical and physical properties before by application, but also after application, to have an aging resistance, but in addition to having a specifically low viscosity at the usual temperature, in order to enable them to best impregnate the paper insulation, on the other hand, the viscosity of the same impregnating agent must be as high as possible. cable operating temperatures to avoid impregnation migration or leakage to lower locations. The same impregnating agent must also have suitable theological properties, be sufficiently adhering to both the insulation and the metal cores, be sufficiently plastic even at low temperatures and have a low coefficient of thermal expansion in order to lay down, respectively. the thermal cycles in the cable did not crack, break the paper insulation and create cracks or voids in the impregnated insulation. The difficulty of meeting the combined requirements, in many ways contradictory, leads to the fact that known solutions are predominantly a compromise and the requirements are usually met only one hundred years or, to a sufficient extent, uncomplexed. At the same time, given the diversity of these postulates, achieving essential results can only be expected by the use of composite materials, ie, mixed types of impregnants composed of multiple active ingredients and appropriate defined materials and their proportions in a given combination. The essential component of such mixtures remains the liquid insulator, usually mineral oil or synthetic oil, the properties of which are modified by the integrated components of other mixed ingredients and additives.

Different type polymers, which are added to the oil types of impregnants such as plasticizers, adhesion promoters and also as pour point elevators, have the property of increasing the viscosity index of the composition, the more the polymer has a higher molecular weight, polymer structure also plays an important role. However, the influence of the impregnation process on the insulation of the cables, due to the increased viscosity of such impregnating agent, has a negative effect. It is then necessary to select the higher impregnating temperatures or longer impregnating sachets in the pre-impregnation, which, however, does not adversely affect the electrical and functional properties of the cables produced. Due to the lack of microcrystalline petroleum waxes of the appropriate type, respectively. analogous constituents with gradations above 85 ° C which, without falling out of the mixture and capable of providing the impregnant with a sufficiently high pour point, are in part absorbed by polymer additives. High molecular weight polymers with an average molecular weight of 15,000 or more usually can provide at least the desired high flow temperature, but because it is not possible to integrate larger amounts of them, impregnants do not achieve the requisite plasticity. Polymers with a lower molecular weight of about 3,000, oily-honey-like consistency, may be added in sufficient quantity to achieve good plasticity and tackiness, and these will only minimally affect the impregnating drop point. However, by limiting the choice of suitable types which also need to meet a number of specific requirements, including those of a high quality, technological and applied nature, due to their limited availability, high cost and other circumstances, the use of these polymers appears to be inefficient. and economically disadvantageous and also their application usually requires the addition of other ingredients to increase the drop point of the impregnant, and it is not always possible to avoid the dropping of some of the components that occurs in some cases.

The disadvantages of the prior art are eliminated by the solution according to the invention. In essence, this solution is characterized in that the electro-insulating impregnant for the laminated paper insulation of high-voltage power cables is a homogenized blend of 20 to 74 wt. C, and another portion in the mixture is 1 to 30 percent by weight percentamorphic polypropylene, the punch point of which is at least 70 ° C and contains 5 to 40 percent by weight of stereoblock structures and isotactic fractions dispersed in the atactic polymer to determine this content by Natta fraction analysis as a proportion of insoluble n-heptane at room temperature. An alternative solution is in principle similar to im-pregnant, characterized in that it contains 20 to 75 percent by weight of isolating oil, 1 to 10 percent by weight of pervent colophony, 25 to 75 percent by weight of the specified microcrystalline petroleum wax and a proportion of 1 to 30 specific amorphous polypropylene. A suitable further embodiment of the solution is an impregnating agent which is characterized in that it comprises a proportion of 95 to 99% by weight 3 212 87

The specified blend impregnating blend of from 20 to 74% by weight of insulating oil, from 25 to 75% by weight of microcrystalline petroleum wax and from 1 to 30% by weight of atactic polypropylene, or from 20 to 73% by weight of insulating oil, from 1 to 10% by weight pereent colophony, 25 to 75 pereent of microcrystalline petroleum wax and 1 to 30 pereent of amorphous polypropylene, which is non-volatile impregnant is homogenized with a 1 to 5 pereent polyolefin, preferably high pressure polyethylene, characterized by a melt flow index of 50 to 500 and a maximum density of 0.920 g / cm ^.

The inconvenient impregnant of the present invention may be regarded as a complex solution to both the technical and application aspects. The necessary ingredients of the mixture are commonly available, their price is relatively low, advantageous. Types of paraffin oils, including so-called pseudorafinates, are also suitable for insulating tax purposes. The amorphous poly (propylene) based blend constitutes a secondary material, e.g. practically a waste product arising from the production of isotactic polypropylene by the Ziegler.Natt process. Its applicability is determined by the choice and pre-heat treatment, where the water and solvent are removed, thereby obtaining a melt which contains a mixture of atactic, stereoblock and isotactic polypropylene, generally of a different composition from each production batch. Each of these amorphous polypropylene components performs a distinctly different and, at the same time, beneficially on the resultant functional properties for a given purpose, i.e. as part of a non-slippery impregnant. The content of the reactive polymer, whose molecular weight is about 10,000, ensures its good solubility, and in view of its structure, which is dense, honey-like, sticky consistency with the cold flow, in the non-slippery impregnant it makes it good plasticity and adhesion, virtually without adversely affecting the height of the impregnating heat. The present stereoblock structures with a wide range of molecular weights up to 300,000 together with the isotactic polymer are only limited solubility at the operating temperature of the cables, dispersed therein and thus creating spatial barriers against the migration of the impregnating agent, thus acting as an effective drop point enhancer. In the case of amorphous polypropylenes that contain less high molecular weight structures, increasing the drop point by integrating a small amount of additional polymer in the mixture.

The proportion of amorphous polypropylene improves the electrical properties not only in the freshly prepared impregnating agent, but also has a beneficial effect on its oxidation stability, since it exhibits minor changes in dielectric properties in the area of impregnation temperatures, and thus changes in dielectric properties after long-term aging. This makes it possible to eliminate or substantially limit the content of natural resin, the colophony in the mixture, which, due to its polar structure, has an adverse effect on the electrical properties. Thus, the proportion of the specific amorphous polypropylene fulfills the function of the plasticizer in the composition, increases its adhesion, reduces the viscosity index and also acts as an antioxidant. In consequence, the non-slippery impregnant with higher technical parameters and extended application possibilities is also suitable for cables with higher voltages, for example 22, 35 kV or even higher.

The mixture of ingredients forms a stable gel whose proportions are not separated even during long-term operation of the cables. The blended product does not degrade, does not change the properties, nor does its 4 212 876 overheat to higher temperatures during preparation and application, respectively. during the downloaded operating conditions, so it provides the permanently required properties of the respective cables. The practice requirements meet the solution comprehensively, eliminating the major part of the existing inadequacies so far in the production as in the application, in terms of technical, technological and economics. EXAMPLE 1 12 parts by weight of amorphous polypropylene having a point of detection, as determined by the ring-ring test, were added to a component of 38% by weight of a high tension insulating cable, corresponding to CSN 65 6846, heated to 160 ° C. The stage ČSN 65 7060 was 154 ° C. The component contained 85.10% by weight of the atactic polymer, 12.10% by weight of the stereoblock polymer, and 2.90% by weight of the isotactic polymer, in the determination of this content by n-heptane analysis.

After homogenization of the two components, 50 parts by weight of cerezine 80, corresponding to GOST 2488-73, which had a drop point according to Ubbelohd of 82 ° C, a viscosity of 100 ° C of 14.3 mm 2, s, and a viscosity of 14.3 mm 2, were added to the solution, with stirring. specific internal resistance at 100 ° C 1.5.101 ^ Ohm.m. Until the ingredients were homogenized, the temperature was maintained at 100 τ 120 ° C with stirring. The non-sluggish impregnant obtained had a drop point of Ubbelohde at 79 ° C and the viscosity here at 50 ° C was 50 mPa.s. The etrattor factor at baseline, at 100 ° C and 50 Hz was 0.0157, the specific internal resistivity at 100 ° C was 1.3.10 ^ θ Ohn.m

After artificial aging of the ČSN 65 6846 stage, the loss factor had a value of 0.0374 at 100 ° C and a measured internal resistance at the same temperature of 8.7.10 Ohm.m. The resulting non-slippery impregnant was applied to 22 kV heavy current cables, whose conductive Cu core was insulated with 48-layer wound paper insulation from soda-cellulose podium ČSN 50 2622. The cables could be used for routes without limiting height differences, including the possibility of vertical installation. Example 2 To a proportion of 50% by weight of an oil-type impregnant containing 87% by weight of high tension cable oil of CSN 65,6846, 8% by weight of amorphous polypropylene, specified in Example 1 and a ratio of 5% by weight of Greek colophony, after heating of this to 120 ° C, 50% by weight of ceresine was added, while stirring, as specified in Example 1, while the temperature was maintained at 100-120 ° C with stirring until the components were homogenized. The prepared non-slurry impregnant had a drop point of Ubbelohde 75 ° C and a viscosity at 100 ° C of 25 mPa.s. The loss factor in the flood state at 100 ° C and 50 Hz had a value of 0.03792; the specific internal resistance value at 100 ° C was Ο, 55.1ΟΊ'θ Ohm.m. The loss factor was 0.05752 at 100 ° C and the specific internal resistance at 100 ° C was 4.3.10 ^ Ohm.m. The non-slippery impregnant obtained fully complies with the application requirements for similar types of high-voltage high-voltage cables as in Example 1, up to 35 kV, intended for unimpeded or high-altitude routes. to store vertically.

Claims (3)

EXAMPLE 3 To a weight percent of 97% by weight of impregnant Specified as in Example 2 immediately after the addition of ceresin, successive, at 120 ° C, adding 3% by weight of Bralen SA 200 polyethylene having a flow index of O while stirring. melt 200 and a density of 0.916 g / cm, said temperature being maintained throughout the mixing of the ingredients until homogenized. The non-sluggish impregnant produced had a drop point of Ubbelohde of 83 ° C, a viscosity of 100 ° C of 36 mPa.s. The loss factor at 100 ° C and 50 Hz was 0.0225, the specific internal resistance at 100 ° C was 0.74.10 µm. After artificial aging, according to ČSN 65 6846, the loss factor value was 0.05097 at 100 ° C and the specific internal removal at 100 ° G was 5.5.10 µm. The resulting non-slurry impregnant was applied for similar purposes and in a manner similar to those of Examples 1 and 2 for 22 and 35 kV cables intended to be mounted on highway routes without limitation or restriction. on the vertical installation, it being assumed that there are fried operating conditions here, in particular increased short-term transients of the usual maximum cables of the respective cables. In particular, the invention can be used directly in cables, where the respective types of high-voltage, especially 22 and 35 kV, power-bearing cables with laminated paper insulation are produced. SUBJECT OF THE INVENTION What is claimed is: 1. An electroinsulating non-sputtering impregnant for laminated paper insulation of high tension power cables, based on a mineral oil / olefin polymer blend, characterized in that the impregnating agent is a homogenized blend of components containing 20 to 74 weight percent insulating oil, 25 to 75 weight percent microcrystalline petroleum oxide , preferably electrolytic ceresine, the Ubbe-lohde drop point is at least 70 ° C, and the additional blend is from 1 to 30 percent by weight percentamorphic polypropylene, the punch point of which is at least 70 ° C and contains 5 to 40 percent by weight the stereoblock structures and the isotactic particles dispersed in the attacker polymer in the determination of this content by Natta fraction analysis as a non-soluble fraction in n-heptane at room temperature. 2. An electroinsulating non-sagging impregnating agent according to claim 1, comprising from 20 to 73 percent by weight of insulating oil, from 1 to 10 percent by weight of colophony, from 25 to 75 percent by weight of the specified microcrystalline petroleum wax, and from 1 to 30 percent by weight of the specified microcrystalline petroleum wax. Specified amorphous polypropylene. 3. An electroinsulating non-sagging impregnating agent according to claim 1, characterized in that it comprises from 95 to 99% by weight of the specified mixed non-sagging impregnant of 20 to 74% by weight of insulating oil, 25 to 75% by weight of microcrystalline wax and 1 to 30% by weight of atactic polypropylene, or from 20 to 73 percent by weight of insulating oil, from 1 to 10 percent by weight of colophony, from 25 to 75 percent by weight of microcrystalline petroleum wax, and from 1 to 30 percent by weight of 6,212,878 percent of amorphous polypropylene, which has a homogeneous proportion of 1 to 5 percent by weight of impregnating impregnant polyolefin, preferably a high pressure polyethylene, characterized by a melt index of 50 to 500 and a density of at most 0.920 g / cm 2. Price: 2,40 Kčs Printed by Moravian Printing Works, Operation 12, Leninova 21, Olomouc OPE A In A Description of the Invention, Authorized Certificate No. 212 876Int.Cl. B Ol B 3/20 In the description of the invention for the author's certificate no. Correct: Electro-insulating non-slip impregnant for layered paper insulation of high-voltage ailn-jet filaments Office for Inventions and Discovery