BG67470B1 - Three-phase on-load tap changer for distribution transformers - Google Patents

Abstract

The on-load tap changer comprises a carrier head (1), an insulating cylinder of two sectors (2, 3) and a bottom (4). On the cylinder axis are located one main vacuum arc-suppression chamber (V1) and one supplementary vacuum arc-suppression chamber (V2) for each phase (X, Y, Z). On the inverted mirror imaged arc-suppressing chambers (V1 and V2) are mounted radial contact bridges (27, 28) that contact the U-shaped fixed contact elements (29) located on the periphery of the insulation cylinder (2, 3). The movable contact terminals of the arc-suppressing chambers (V1 and V2) also have radial contact bridges (39) and an opening and closing system of (V1 and V2). The three main vacuum arc-suppression chambers (V1) are secured to an insulation sector (25) by a pipe connected to a Maltese gear (21) located in the carrier head (1). The supplementary vacuum arc-suppression chambers (V2) are also secured to a second insulation sector (22) carrying resistors (R) connected to a second Maltese gear (24). The two Maltese gears are rotated in two-step switching by two angled rollers (13) of double transmission (12), which is driven unevenly by springs (10) via a disc (9) and a worm gear (11-14). The output shaft (15) is directly coupled to a motor-driven drive shaft. The on-load tap changer can be mounted vertically or horizontally in the transformer. It can be used both in linear regulating winding coil and in coils interrupted in the middle. There is on embodiment wherein the on-load tap changer can be removed for supervision without opening the transformer.

Description

(54) HA VOLTAGE STEP-UP REGULATOR FOR DISTRIBUTION TRANSFORMERS

Field of technique

The invention relates to a three-phase step voltage regulator, operating as an on-load selector, applied to the regulation of the on-load voltage of relatively small power transformers. Vacuum arc extinguishing chambers can be used in such step regulators.

Prior art

A step regulator /1/ is known with an electrical diagram of regulation under load, interrupted in the middle. It has a contact bridge of two main arcing contacts and a contact bridge of two auxiliary arcing contacts with a resistor connected between them. Switching according to this scheme is done /2/ by a two-stage spring energy accumulator, which contains a main spring with levers connected to a vertical insulating shaft that carries the main contact bridge and an auxiliary spring with levers connected to a vertical insulating shaft that carries the auxiliary contact bridge with resistors. Two-step switching is performed. The step regulator is three-phase with three phases located one below the other in an insulating cylinder attached to a supporting head /3/. This step-up regulator is built into the oil space of a distribution transformer.

A disadvantage of this step regulator is that there is no option with vacuum arc extinguishing chambers. Another disadvantage is that it cannot be used for a linear regulation scheme. A disadvantage is that the spring energy accumulator is complex and difficult to adjust.

Another step regulator /4/ is known, in which there is one main vacuum arc extinguishing chamber and one auxiliary vacuum arc extinguishing chamber per phase, connected by a current limiting resistor. It also works with two-step switching. It uses even and odd Maltese wheels and a double translation with two rollers that switches them sequentially one after the other. Gear pairs rotate two vertical insulating shafts, on which the main vacuum arc extinguishing chambers and the auxiliary vacuum arc extinguishing chambers for the three phases are mounted separately. The supporting structure is composed of a supporting head, a vertical insulating cylinder and a bottom. The mechanisms are located in the bearing head, and U-shaped fixed contact elements, which can be 10 or more in number, are mounted at equal angles on the inner surface of the insulating cylinder. There are also movable contact bridges that connect these fixed contact elements with vacuum arc extinguishing chambers in a certain order. There is also an additional Maltese gear which, via a lever system, drives an externally located preselector.

A disadvantage of this step-up regulator is that it is complex and of large overall dimensions, which does not provide the task set here to have a small step-up regulator for distribution transformers. The main vacuum arc extinguishing chamber and the auxiliary vacuum arc extinguishing chamber are located side by side, and the fixed contact elements can be more than 10 pieces. This increases the diameter and transverse dimension of the insulating cylinder. Mechanisms are more and more complicated due to the fact that there are variants with different number of positions and side selector.

A step regulator /5/ for distribution transformers with a more special design is also known. It has only one vacuum arc extinguishing chamber per phase and a two-step selector. There is no spring energy accumulator, and quick shifting is done by a mechanical system. It is mounted under the hood, above the active part of the distribution transformer, and the electrical system is in a separate box.

A disadvantage of this step regulator is that it does not provide vertical mounting, and its placement under the cover of the transformer makes it difficult to mount the bushings for medium and low voltage. Another disadvantage is that switching the vacuum arc chamber twice in one switch reduces the electrical resource, and the lack of a spring battery can cause problems in the event of a sudden interruption of the power supply during switching.

A disadvantage is that the mechanical system and the electrical system of the motor drive are separated, which makes revisions difficult and does not meet the requirements of the standard. In order to carry out an inspection and possible repair, the power supply must be switched off and the transformer must be opened. It is also a disadvantage that it does not regulate in a circuit with a break in the middle.

Technical essence of the invention

The task of the invention is to create a three-phase step voltage regulator for distribution transformers, which has a simplified construction and small dimensions and weight. To be able to work both with a linear regulation scheme and with one interrupted in the middle. To be able to be built into the transformer, both horizontally and vertically. There should also be an option with an oil-sealed oil pan and the possibility of revision without opening the transformer.

The task is solved with a three-phase step voltage regulator operating as a selector under load, containing an oil vessel composed of a bearing head, an insulating cylinder and a bottom. A spring energy accumulator and a double translation with Maltese wheels are located in the bearing head. There is one main vacuum arc extinguishing chamber and one auxiliary vacuum arc extinguishing chamber, which are connected by resistors, for each phase. The three main vacuum arc extinguishing chambers are mounted on an insulating shaft, and the three auxiliary vacuum arc extinguishing chambers are mounted on a second insulating shaft located parallel to the first. On the inner surface of the insulating cylinder, at an equal angular distance, fixed contact elements are mounted, which contact movable contact bridges, connecting them alternately with the vacuum arc extinguishing chambers.

According to the invention, the main vacuum arc-extinguishing chamber and the auxiliary vacuum arc-extinguishing chamber of each phase are located along the axis of the insulating cylinder mirror-image to each other with the adjacent fixed contact terminals to which radial contact bridges are attached. They contact U-shaped fixed contact elements mounted at equal angles on the inner surface of the insulating cylinder. The movable contact terminals of the vacuum arc extinguishing chambers also have radial contact bridges in contact with shunt rings. The three main vacuum arc extinguishing chambers of the three phases are attached to an insulating segment of pipe, and the three auxiliary vacuum arc extinguishing chambers are attached to a second insulating segment to which a resistor is also clamped. Each segment is connected to a Maltese wheel mounted in the bearing head. The two Maltese wheels are capable of two-step rotation by two angled rollers on the double translation, which interacts with the worm wheel with a worm on the output shaft, directly coupled to the drive shaft of the motor drive.

The movable contact terminal of each vacuum arc extinguishing chamber has a rocker arm, a flexible connection and contact springs. The rocker has a roller which, when switching, is in contact with the front teeth of an insulating disk and is capable of opening the corresponding vacuum arc extinguishing chamber, and the rocker is provided with a sliding connection for adjusting the contact solution.

The worm wheel has a tooth that meshes with a tooth on a disc to load the springs. The connection between the disc and the double translation is made by the teeth of an angular backlash clutch.

The step regulator can regulate under load both transformers with a linear regulation winding and those with a regulation winding interrupted in the middle. In this case, the two contact bridges connected to the two terminals of the corresponding vacuum arc extinguishing chamber are displaced at an angle of 36° and contact two adjacent fixed contact elements. At the auxiliary chamber, the connection between the two contact bridges is broken and the resistor is turned on there.

The step regulator can be mounted vertically next to the active part of the transformer or horizontally above the active part, under the cover.

The step regulator described can be installed in an additional oil-sealed oil pan, the mechanisms being mounted on a supporting flange, under which a contact system is fixed. It is electrically connected to the terminals of the insulating cylinder through plug-in contact assemblies.

An advantage of the step voltage regulator according to the invention is that it has a simplified construction with small dimensions and weight, suitable for installation in distribution transformers. Another advantage is that it can work both in a linear control coil circuit and in a circuit with a mid-interrupted control coil. Another advantage is that the step regulator can be mounted both vertically and horizontally. It is also an advantage that there is an option that the step regulator can be removed for revision without opening the transformer.

Explanation of the attached figures

An exemplary embodiment of the step voltage regulator for distribution transformers, according to the invention, is shown in the attached figures, from which:

Figure 1 represents the two electrical circuits by which a step-up regulator can regulate the voltage under load:

a) Line diagram;

b) Schematic with a regulation coil interrupted in the middle.

Figure 2 - two possible ways of embedding the step regulator in the boiler of the distribution transformer:

a) Vertical installation;

b) Horizontal installation.

Figure 3 - longitudinal section through the step regulator and six transverse sections.

Figure 4 - variant where the step regulator is built into an oil-sealed oil pan and can be removed for inspection.

Examples of implementation of the invention

The one shown in Fig. 1, a) a linear scheme of regulation under load contains a main coil A, a regulation coil B, with contact elements C connected to the deviations of the regulation coil, a linear terminal D, one main vacuum arc extinguishing chamber V1 and one auxiliary vacuum arc extinguishing chamber V2 connected in series with resistor R. This is a circuit diagram of one phase and the other two phases are like it and not shown. Most often, the three phases are isolated from each other and connected in a delta. In this case, 9 steps can be switched.

The circuit shown in Fig. 1, b) has a regulation coil B interrupted in the middle, which in this case provides a range of ±4 steps. It is characteristic of the step regulator, according to the invention, that with small structural changes of the contact system, both one scheme and the other can be used.

In Fig. 2 shows two possible options for embedding the step regulator E in the schematically shown boiler F of the distribution transformer. The bearing head H (pos. a) of the step regulator is mounted on the cover K of the transformer, to which, as it is assumed, the active part L is attached. The motor drive M is also clamped to the cover K and is connected to the bearing head by a shaft N. An advantage of this option is that it does not change the way of installation of the medium and low voltage feed-throughs, not shown.

In Fig. 2, b) the step regulator E is installed horizontally under the cover K of the transformer. The bearing head H is the same, but with a slightly changed construction. It is connected to the motor drive through an angle gear P.

In Fig. 3 shows the construction of the step regulator, in the case of vertical installation. Bearings are the head 1, the insulating cylinder composed of two segments 2 and 3, in order to facilitate assembly, and a bottom 4. The bearing head 1 is composed of a body 5 with a flange 6 and a cover 7. Inside the head there is a vertical axis 8, on which are bearing a disc 9 connected to one end of a switching spring 10, a worm gear 11 and a double translation 12 with two drive rollers 13 located at a certain angle to each other on both sides of the double translation 12. The worm wheel 11 is driven by a worm 14, part of the shaft 15 which is connected to the motor drive (Fig. 2). The interaction between the worm wheel 11 and the disc 9 to tension the switching springs 10 takes place through the two teeth 16 and 17 (p-r B-B). The interaction between the disk and the double translation takes place through the two teeth 18 and 19 (рр С-С), between which a free movement 20 is provided. In the center, along the axis of the oil pan, on the housing 5, a lower Maltese wheel 21 is mounted, connected with segment 22 of insulating pipe. A shaft 23 is supported in this Maltese wheel, on which an upper Maltese wheel 24, connected to a second segment 25, and a digital disk 26 are mounted.

Three auxiliary vacuum arc extinguishing chambers V2 are mounted to segment 22, one for each phase X, Y, Z. Three main vacuum arc extinguishing chambers V1 are mounted to segment 25, mirrored to V2. Phases X and Y implement the scheme of Fig. 1, a) (pp. D-D). To reduce the number of drawings of the Z phase, a design implementing the scheme of Fig. 1, b) (p -p E-E). The fixed terminal of the vacuum arc extinguishing chamber V1 is connected to a contact bridge 27, and the fixed terminal of the vacuum arc extinguishing chamber V2 located next to it - to a contact bridge 28. This bridge is isolated from V2 and between it and V2 a resistor R is connected, which is fixed of the segment 22. In the phases X and Y the two bridges are located one below the other in a static position and are in contact with one of ten U-shaped fixed contact elements 29 fixed at equal angular distances on the inner surface of the insulating cylinder composed of the segments 2 and 3. The terminal 30 of the movable contact element of each vacuum arc extinguishing chamber is connected to a rocker 31 with a roller 32, which contacts an insulating disk 33 with front teeth 34. The rocker 31 is connected to the terminal 30 by rollers 35 and has contact springs 36 and a flexible connection 37. The adjustment of the contact solution of the vacuum arc extinguishing chamber is done by a special sliding connection 38, established on the rocker 31. The flexible connection 37 is connected to a contact bridge 39, which is in contact with a current drain ring 40 with a terminal 41. The terminals 41 of the vacuum arc extinguishing chamber V1 and the vacuum arc extinguishing chamber V2 are connected to an external conductor 42.

How is the circuit from Fig. 1, b) can be seen on phase Z and section E-E. Two contact bridges 43 and 44 are connected to the two terminals of the vacuum arc extinguishing chamber V1 and are established on two adjacent U-shaped fixed contact elements 45 (in this case located at an angle of 36°). Analogous contact bridges are mounted on the two terminals of the vacuum arc extinguishing chamber V2, but a resistor R is connected between them. The U-shaped contact elements 45 of the main vacuum arc extinguishing chamber V1 and of the auxiliary vacuum arc extinguishing chamber V2 are connected by a wire 46. The lower ends of the two segments 22 and 25 are supported on the axis 47 mounted on the bottom 4.

The step regulator of Fig. 3 is located in the oil space of the distribution transformer and is not separately oiled, as is the case with step regulators of power transformers. In order to revise the step regulator, the transformer must be opened. In Fig. 4 shows a variant in which the step regulator from Fig. 3 is placed in an oil-tight vessel composed of a bearing head 1, an insulating cylinder 2 and a bottom 3. The bearing head 1 has a body 4 with a flange 5 and a cover 6. The contact systems 7 of the step regulator from Fig. 3 are fixed under a supporting flange 8, on which the mechanisms are mounted, designated by the same numbers as those in Fig. 3. The bearing head of the step regulator from Fig. 3 is dropped. The fixed end of the switching springs 10 is clamped to a column 9 mounted on the supporting flange 8. To make a revision with the transformer turned off, the cover 6 is removed and the supporting flange 8 is taken out together with the mechanisms and contact systems 7. The electrical connection is made from ten plug contacts A for each phase X, Y, Z and one or more plug contacts B for the current terminal.

The operation of the step regulator is as follows.

The drive shaft of the motor drive is connected to the input shaft 15 (Fig. 3) of the step regulator. The worm 14 rotates the worm wheel 11 one turn per shift. Through the tooth 16, the worm wheel 11 is rotated, with the help of the tooth 17, the disc 9 and the switching springs are tensioned. When the dead center of the carrier of the movable end of the spring is passed, the energy in it is released. The tooth 18 of the disc 9 rotates the tooth 19 of the double translation 12 in a jumping fashion, which performs a rotation of 180°. The two translation rollers 13 successively move the two Maltese wheels 21 and 24 in an angular step of 36°. Thus, segment 22 rotates the three auxiliary vacuum arc extinguishing chambers V2, and segment 25 the three main vacuum arc extinguishing chambers V1. The movable contact bridges 27 and 28 successively switch to the adjacent fixed contact element 29. The roller 32 of the corresponding rocker 31 through the tooth 34 of the disc 33 opens the corresponding vacuum arc extinguishing chamber during the rotation and passage from one fixed contact element to the adjacent one becomes current-free. This is how power switching takes place.

When adjusting in a coil interrupted in the middle (Fig. 1, b), the two contact bridges 43 and 44 (Fig. 3, p-r E-E, phase Z) of the main vacuum arc extinguishing chambers are switched sequentially, and then of the auxiliary vacuum arc extinguishing chambers. In reverse switching, the sequence is reversed.

Claims (1)

Step-down voltage regulator for distribution transformers, containing an oil pan consisting of a carrying head, an insulating cylinder and a bottom, a spring energy accumulator and a double translation with Maltese wheels located in the carrying head, one main vacuum arc extinguishing chamber and one auxiliary vacuum arc extinguishing chamber connected with a phase resistor mounted on two insulating shafts performing two-step switching, fixed contact elements located on the inner surface of the insulating cylinder and movable contact bridges connecting these contact elements to the vacuum arc extinguishing chambers, characterized in that the main vacuum arc extinguishing chamber (V1) and the auxiliary vacuum arc extinguishing chamber (V2) of each phase (X, Y, Z) are located along the axis of the insulating cylinder (2, 3) mirroring each other with the adjacent fixed contact terminals to which radial contact bridges are attached (27, 28) contacting U-shaped fixed contacts elements (29) mounted at equal angles on the inner surface of the insulating cylinder (2, 3), and the movable contact terminals of the vacuum arc extinguishing chambers (V1, V2) also have radial contact bridges (39) contacting current-discharge rings (40) , with the three main vacuum arc extinguishing chambers (V1) of the three phases (X, Y, Z) being fixed to an insulating segment (25) of a pipe, and the three auxiliary vacuum arc extinguishing chambers (V2) being fixed to a second insulating segment (22), on which a resistor (R) is also caught, wherein the segment (25) is connected to a Maltese wheel (24) mounted in the bearing head (1) and the segment (22) is connected to a second Maltese wheel (21), both Maltese wheels are capable of two-step rotation by two rollers (13) displaced at a certain angle on the double translation (12), which is in interaction with the worm wheel (11) with a worm (14) on an output shaft (15), directly coupled with motor drive drive shaft.