UA148322U - THREE-PHASE POWER CABLE LINE WITH EXTERNAL FORCED COOLING - Google Patents

Abstract

Three-phase power cable line with external forced cooling contains three identical single-core cables, the axes of which are at the vertices of an equilateral triangle, in the plane of the perpendicular section of the cable line, each of which has at least copper or aluminum conductive conductor, main conductor located on the surfaces of the conductive core and the main electrical insulation of the conductive core, copper electromagnetic shield, insulating outer sheath and located in one of the three identical in size, part of the cable line housing. In each part of the housing of the cable line, except for a single-core cable, there are two plastic cooling pipes of the same shaped cross-section, in which cooling water flows in opposite directions. The cable line has two pipes located next to the body of the cable line, which are connected by pipes at the ends of the construction site of the cable line with plastic cooling pipes of shaped cross section. The housing of the cable line contains three radially arranged steel magnetic sheets and an outer sheath, which is made of non-magnetic non-conductive moisture-resistant tape material.

Description

The useful model belongs to the technical means of transportation and distribution of electric energy and can be used in the design and laying of cable networks of large and extra large capacities.

Well-known three-phase cable lines (CL) of high power, made of three single-core cables of high and ultra-high voltage. Each of these three cables contains, as a minimum, a copper or aluminum conductor, the main electrical insulation of the conductor, semi-conductive shields on the surfaces of the conductor and the main electrical insulation of the conductor, a copper electromagnetic shield (EME), and an insulating outer sheath of the cable.

The location of individual three cables in a three-phase KL "triangle" |Z) is known. With this design, the cables are adjacent to each other with their sheaths, and the distance between the centers of the current-conducting cores forms an equilateral triangle in the plane of the perpendicular section

KL The main advantage of such CL is its electrical symmetry. The symmetric three-phase system of currents and voltages applied to the beginning of such a CL remains the same symmetric at its end.

The main disadvantage of the KL design located in a "triangle" is the following. The effective thermal resistance of the soil, which is used for the thermal calculations of KL, has a maximum value due to the minimum value of the surface area of the KL, which gives heat to the soil. As a result, the current carrying capacity of the CL decreases due to the increased thermal resistance. There is also a second disadvantage of the KL located in a "triangle". In such a KL, the electromagnetic shields of each cable are as close as possible to the current-conducting cores of neighboring cables. Figure 4 shows that eddy currents are induced in the solid electromagnetic shields of each cable of a three-phase cable under the action of the external magnetic fields of neighboring cables of this cable, which do not depend on the EME connection means or their grounding means. Losses from eddy currents in the EME cause additional heating of the cables and, as a result, an additional decrease in the carrying capacity of the CL current as a whole.

The well-known design of CL, which is presented in 111.

A three-phase power cable contains three identical single-core cables, the axes of which are located at the vertices of an equilateral triangle, in the plane of the perpendicular section of the cable, each of which has, at least, a copper or aluminum current-conducting core, the main electrical insulation

From the current-conducting core, two semi-conductive shields are located on the surfaces of the current-conducting core and the main electrical insulation of the current-conducting core, a copper electromagnetic screen and an insulating outer shell. At the same time, all three cables are located inside the housing, which is made of steel magnetic sheets in such a way that each of the cables is located inside a part of the housing, each of which has the same dimensions for each of the three cables. At the same time, the housing has three non-magnetic gaps on the outer shell in the tangential direction in the plane of the perpendicular section of the housing and along the axis of the cable along the entire length of the cable, which have the same dimensions and the same distance from each other. In the KL design, which is presented in |1), the presence of the KL case, which is made of steel magnetic sheets, significantly shields the external magnetic flux from the adjacent KL cables. At the same time, the "longitudinal" currents in the electromagnetic shields of the cables are reduced and, as a result, the total heat losses in the KL are generally reduced. Thus, in the three-phase power cable line, the design of which is presented in (1), the current carrying capacity increases, which is a positive effect.

The design and principle of action of the three-phase power CR, which are presented in (1), are the closest technical solutions for the construction of a three-phase power CR with increased current carrying capacity.

The design of the three-phase power cable line presented in (1) is taken as the closest analogue in the development of the proposed three-phase power cable line with external forced cooling.

The disadvantage of the closest analogue is the following.

The current-carrying cores of the nearest CL analogue are heated due to the operating current in these cores, and the copper electromagnetic screens of each CL cable can be heated either by the action of "longitudinal" currents in the copper-wire electromagnetic screens when they are grounded on both sides, or due to eddy currents in dense electromagnetic screens when any means of their connection and grounding. The three-phase power cable line, the design of which is presented in (1), is cooled by a natural means. The heat flow, which is due to the heating of the current-conducting conductors and screens of the KL, goes, overcoming the thermal resistance of the main electrical insulation of the KL cables, their outer sheaths and the thermal resistance of the surrounding soil to the point where the temperature is taken as the calculated temperature of the surrounding environment. The total thermal resistance of the electrical insulation and the surrounding soil for high- and ultra-high-voltage power cables has a fairly significant value. As a result, for all CLs that are located in the ground and are cooled naturally, the current carrying capacity is quite small. Even for copper current-carrying cores of high-voltage CRs, the current density offered by manufacturers does not exceed 1 A/mm". This is a fundamental drawback of such CRs and requires an increase in the permissible current density in current-carrying cores.

The problem is solved by the fact that a three-phase power cable line with external forced cooling, containing three identical single-core cables, the axes of which are located at the vertices of an equilateral triangle, in the plane of the perpendicular section of the cable line, each of which has, at least, a copper or aluminum conductive core , the main electrical insulation of the current-conducting core, two semi-conductive shields located on the surfaces of the current-conducting core and the main electrical insulation, a copper electromagnetic shield, an insulating outer shell and located in one of three parts of the cable line body of the same size. In each part of the case, in addition to the single-core cable, there are two plastic cooling pipes of the same cross-section, in which cooling water flows in opposite directions. The cable line housing contains three radially arranged steel magnetic sheets and an outer sheath that fixes all six plastic cooling tubes in the position of best surface contact with the insulating outer cable sheath and the steel magnetic sheets of the cable line housing and is made of any non-magnetic moisture-resistant tape material. At the same time, the cable line has two pipes, which are located next to the body of the cable line and are connected by means of nozzles at the ends of the construction section of the cable line with plastic cooling pipes of a shaped section.

The essence of the useful model is explained by the following drawings: - in fig. 1 shows the design of a part of a three-phase power cable line with external forced cooling, which is located in the cable line housing; - in fig. 2 shows the complete construction of a three-phase power cable line with external forced cooling.

In fig. 1 shows part of the design of a three-phase power KL with external forced cooling. This part of the CL contains three identical single-core cables, each of which has, at least, a copper or aluminum conductive core 1, the main electrical insulation 2 of the conductive core, two semiconducting screens C and 4, which are located, respectively, on the surface of the conductive core 1 and on the outer surface main electrical insulation 2, copper electromagnetic shield 5 and insulating outer shell 6. All three cables of this part of the KL are located inside the KL body in such a way that the axes of the single-core cables are at the vertices of an equilateral triangle, in the plane of the perpendicular section of the KL. At the same time, in each part of the CL housing, in addition to the single-core cable, there are two plastic cooling pipes 8 of the same cross-section, in which cooling water 9 flows in opposite directions, and the housing of the cable line contains three radially located steel magnetic sheets 7 and an outer shell 10. which fixes all six plastic cooling pipes 8 in a pressed state in the position of the best surface contact with the outer sheath 6 of the CL cable and the steel magnetic sheets 7. In addition, the cable line housing contains the outer sheath 10, which is made of any non-magnetic moisture-resistant tape material.

In fig. 2 presents the complete design of a three-phase power KL with external forced cooling. Such a complete structure includes a part of a three-phase power cable line with external forced cooling, which is shown in fig. 1 and, in addition, contains a pressure water pipe 11 and a non-pressure water pipe 14, which are located next to the housing

CL and connected to plastic cooling pipes 8 with the help of nozzles 12 and 15 from one end and with the help of nozzles 13 and 16 from the other end of the construction site CL.

A three-phase power cable line with external forced cooling works as follows.

When the operating current flows along the current-conducting wire 1 in accordance with Joule's law-

Lenza this vein heats up. In high and ultra-high voltage cables, the main electrical insulation 2 is heated due to the through-conduction current and polarization of the material. When the electromagnetic shields 5 of copper-wire construction are grounded on both sides in the CL, they are heated by the so-called "longitudinal" currents that flow in the shields 5. If the electromagnetic shields 5 have a dense structure, such screens are also heated due to eddy currents, regardless of the means of their connection and grounding in the KL. The heating of semiconductor screens C and 4 is very small and is always neglected in the thermal calculations of CL.

In the cable line of natural cooling, which is taken as the closest analogue, the total heat flow from the heated current-conducting cores 1, the main electrical insulation 2, and the electromagnetic shields 5, overcoming the thermal resistance of the main electrical insulation 2, the outer protective sheaths 6 of the KL cables and the surrounding KL soil, passes into the environment, i.e. it passes into an isothermal environment, the temperature of which is taken as constant in thermal calculations of CL and is called the temperature of the surrounding environment. This is the theoretical basis for the calculation of KL, which are laid in the ground, work in a constant load mode and are cooled by a natural means.

In the design of the proposed three-phase power cable line with external forced cooling, water from the pressure pipe 11 through the nozzle 12 with the help of a water distribution collector (not shown in the drawing) is fed into three cooling plastic pipes 8 of a shaped cross-section located one through the other from one end of the construction site KL . Through the nozzle 13, water from the pressure pipe 11 is supplied to the other three cooling pipes 8 at the opposite end of the construction site CL by means of a water distribution manifold. At the same time, water flows in opposite directions in two cooling pipes 8 adjacent to the surface of the outer protective shell of one KL cable. Water in the cooling pipes 8 when flowing along the KL cable is heated due to heat transfer to it from the heated surface of the cable. When water flows in opposite directions, the heating temperature of the cable surface will be the same anywhere along the construction site of the KL. After passing through the cooling pipes 8, the heated water flows into the non-pressure pipe 14 through the nozzles 15 and 16, respectively, at the beginning and at the end of the construction site KL. The shaped cross-section of the cooling pipes 8 is selected under the condition of ensuring the maximum area of thermal contact with the outer surface of the cable and the steel magnetic sheet 7 of the cable line body. The outer shell 10 presses the surfaces of the cooling pipes 8 to the outer surface of the cable and to the surfaces of the steel magnetic sheets 7, thus providing the minimum possible value of thermal resistance for the heat flow that is diverted to the cooling water 9. There is only one mandatory condition for the outer shell 10 - it must be non-magnetic and non-conductive. The technology of applying fabric structure tapes, which have the ability to tighten with subsequent impregnation, can be proposed, which makes the outer shell 10 waterproof and at the same time waterproof. This technology, in addition to pressing the cooling pipes 8 to the surface of the cable, additionally provides protection of the steel sheets 7 from moisture in the soil. The steel body of the KL represents

There are three steel magnetic sheets 7 with it, which are pre-welded into the structure at an angle of 120" in the radial direction, and of a length that is technologically convenient during the installation of the KL. During the preliminary manufacture of the KL body, a design can be provided when the steel magnetic sheets 7 are welded with a small-diameter steel pipe for additional laying of fiber optic cable in the KL (see Fig. 1). Installation of single-core cables and cooling pipes 8 in the KL body, as well as the application of the outer shell 10 takes place directly at the construction site of the cable line.

Thus, the physical effect of reducing the total thermal resistance for a three-phase power cable line with external forced cooling and thereby increasing the current carrying capacity of this cable line is as follows.

The thermal resistance of the soil, which is the heaviest, is excluded from the total thermal resistance of the cable line. However, despite the fact that the additional thermal resistance of the wall of the plastic cooling pipe 8 appears and the temperature of the surrounding environment increases due to the heating of the water U in the cooling pipes 8, the total thermal resistance for the proposed cable line design is significantly reduced, compared to the closest analog of a cable line.

We will illustrate this conclusion with an example of a comparative simplified calculation of the maximum allowable value of the phase operating current for the closest analogue of a three-phase power cable line and for the design of a three-phase power cable line with external forced cooling, which is proposed. Both KL are made of the same single-core cables of the APvP2gzh 1 x 630/120-64/110 brand, have a construction length of 600 m and are laid in the ground with a specific thermal resistance of -12 K-m/W at a depth of n-1.2 m

For the closest analogue of a three-phase power line laid in the ground, the total thermal resistance UAt is calculated as |З

ХК - Кт Ко Кк, (1) where: Ко and Ко" are, respectively, thermal resistances of the main electrical insulation and the outer sheath of the single-core cable.

These thermal resistances are the same for the two CL designs under consideration, and after calculations are equal to |З

Ky - 027 Kk m/W

Ku; - 0033 km/W

Kk . . . 753 is the effective thermal resistance of the soil for the closest analogue of a three-phase power KL, taking into account the mutual heating of the rusidian, KL coils. This thermal resistance is calculated as gi bo. and ! 58 and 57

Kgta - Zp - 3.1 and - : 4 ((b.----- 2 3-8 5---

Evil Kk iv iv 5 Kk 5 Kk

K-m/W, (2) where: p. depth from the soil surface to the axis of the lower cable, m; t - interaxial distance between cables along the vertical axis, m; 5. interaxial distance between cables in KL, m;

K - the outer radius of the single-core cable in KL, m.

Ki" -125

K-m/W

The total thermal resistance of the closest analogue of the design of the three-phase power KL.

MK 155 km/W

The maximum allowable value of the phase operating current I for the closest analogue of the design of a three-phase power KL, which operates in the stationary mode, is determined on the basis of the thermal akon Ohm |ZI. "SUK, UK et t; (3) where: i. the maximum permissible temperature of the main electrical insulation made of cross-linked polyethylene (m -90 275);

Is - the temperature of the surrounding environment (we take Yi re -20275);

K, - the electrical resistance of an aluminum conductive core at the temperature of the core I -90750 3, taking into account the effect of eddy currents and the effect of the proximity of cables in KL per 1 m of cable length.

Thus, for the closest analogue of the construction of a three-phase power cable line, we have the maximum permissible value of the phase operating current, which is -867 A

For the design of the proposed three-phase power cable line with external forced cooling, the total thermal resistance will be:

HC - Ky Ko Kz (4)

Kz 0077 Kk muW,

Kt o. . . . .

From where: - the thermal resistance of the wall of the plastic cooling pipe of the 8-shaped section.

For this construction of the cable line, it can be roughly considered that the temperature of the surrounding environment is the average temperature of water 9 at the inlet and outlet of the cooling pipes 8. This temperature depends on the flow of water through the passage section of the cooling pipes 8 depending on the pressure in the pressure pipe 11 and length of construction site KL.

Approximate calculation |4| showed that at the temperature of the conductive core 1, which is equal to -90 2C, the flow rate of water is 20 liters per minute throughout one cooling pipe 8 and the length of the construction section of the cable line is 600 m, the average temperature of water 9 in the cooling pipe will be -47-50 76.

Thus, the maximum permissible value of the phase operating current in the current-conducting core 1 of the three-phase power CL cable line with external forced cooling, which is proposed, will be equal to when using (3)

And t -1373-1324 A, which is 58-53 95 more than in the design of the closest analogue of a three-phase power cable line.

The presented advantages allow us to draw a general conclusion about the positive effect of the design and principle of operation of the proposed three-phase power cable line with external forced cooling.

Sources of information: 1. Patent of Ukraine for a utility model Mo 99421 НО1 9/00, publ. 10.06.2015, Bull. Me11. 2. M.N. Bronguleeva, S.S. Horodetskyi. Kabelnewe lines of high voltage.-M.: GZY, 1963, 437 p. 3. Fundamentals of cable technology. Ed. V.A. Privezentseva. Ed. 2nd - M: "Znergia", 1975, 4726. 4. Ya. Turovsky. Technical electrodynamics. Trans. from Polish - M: "Znergy", 1974, 4886b.

Claims (1)

15 USEFUL MODEL FORMULA A three-phase power cable line with external forced cooling, containing three identical single-core cables, the axes of which are located at the vertices of an equilateral triangle, in the plane of the perpendicular section of the cable line, each of which has at least a copper or 20 aluminum conductive core, the main electrical insulation of the current-conducting core, two semi-conductive shields located on the surfaces of the current-conducting core and the main electrical insulation of the current-conducting core, a copper electromagnetic shield, an insulating outer shell and located in one of the three equal-sized parts of the cable line body, which is distinguished by the fact that in each part of the body of the cable line, except for the single-core cable, there are two plastic cooling pipes of the same cross-section, in which cooling water flows in opposite directions, and at the same time, the cable line has two pipes located next to the body of the cable line, which united for help of the nozzles at the ends of the construction site of the cable line with plastic cooling pipes of a shaped cross-section, and the body of the cable line contains three radially located steel magnetic sheets and an outer shell made of non-magnetic, non-conductive, moisture-resistant tape material. NP AK o deki PI i det o nn y - AS. non I still M sn - and Esp p; ssh sha she a She shi shi oo TV r ya ZHK r osi i ia Zoo onya p ia MEDNYKH u zhyutieya, TE Fig. 1