WO2008078178A2

WO2008078178A2 - Compact isolator switch for medium and high voltage

Info

Publication number: WO2008078178A2
Application number: PCT/IB2007/004131
Authority: WO
Inventors: Giampietro Tosi
Original assignee: Giampietro Tosi
Priority date: 2006-12-22
Filing date: 2007-12-18
Publication date: 2008-07-03
Also published as: WO2008078178A3; ITMI20062490A1

Abstract

Three-pole positionable compact isolator switch for medium and high voltage, set in a rack structure (11) at a crossbar element (13) which acts as a guide element for a case (14) of a circuit breaker group (15), the case being rotatable with respect to the rack structure (11) and translatable, once rotated, with respect to and within the crossbar element (13) between an operative position contained within such crossbar element and a non-operative position extracted from such element (13), the circuit breaker group (15) being arranged between upper connectors and lower connectors (16, 17) integral with the crossbar element (13), inside the case (14) an operating stem (18) being translatable for the engagement and disengagement of a movable contact (26) and a fixed contact (29) for each pole, wherein each movable contact (26) is maintained in the engagement and disengagement positions by the collaboration of return springs (24, 45), identifying the various positions by means of a respective forked square lever (10) connected by means of pivoting (19) to the operating stem (18).

Description

COMPACT ISOLATOR SWITCH FOR MEDIUM AND HIGH VOLTAGE

The present invention refers to a compact isolator switch for medium and high voltage, in particular with limited bulk. There has always been the need to place distribution boxes or equipment in a manner so as to have the least possible bulk. The reason for this lies in the fact that generally such equipment is situated in places which are not very accessible. In these externally-closed boxes, both operating circuit breakers and isolator switches are provided which are usually under load and situated within suitable racks or containers. These racks or containers provide at least two compartments or sections, separated by a separator or wall. In fact, in a first compartment, which is usually placed on top of the second compartment, are situated the isolator switch groups which are under load, additionally to the bars under stress. In the lower compartment, to which/ from which the cables arrive/depart, the general circuit breaker group is arranged along with possible other auxiliary elements, such as protection fuses, etc.

The isolator switch groups are situated in a manner so as to be visible, such that the operator can easily detect when the same are open. In such a manner, the operator can carry out the required functions and interventions in complete safety, even if the upper bars are under voltage.

It must be recalled that the operator must at all costs avoid coming into contact with parts under voltage, even only for accidental and non-predictable reasons .

This parts arrangement necessarily leads to a certain bulk determined by the presence of the two compartments and by the separation between the isolator switch group and the circuit breaker.

A partial solution of the air arrangements of such equipment was achieved by proposing more compact equipment, in which the parts were arranged in hermetic cases filled with suitable gas, such as sulphur hexafluoride (SF6) , which allows decreasing the minimum distances required for the interruption and isolation.

These arrangements also proposed a separation between the isolation zone and the zone dedicated to the circuit breaker, thus determining certain bulk along with uncertainty of the worker operations, since there remains the possibility that the operator operates on the switch with voltage presence.

The object of the present invention is that of making a compact isolator switch for medium and high voltage which is capable of giving maximum safety in the most limited spaces, possibly resolving all of the technical problems set forth above.

A further object is that of making an isolator switch with extremely simple and reliable structure, immediately observed by the operator so to reassure him of the actual opening of the isolator switch and the deactivation in any condition.

Another, further object of the present invention is that of making an isolator switch which has easily reachable parts, for possible interventions of any type.

These objects according to the present invention are attained by making a compact isolator switch according to claim 1.

Further characteristics of the invention are underlined in the subsequent claims.

The characteristics and advantages of a compact isolator switch for medium and high voltage according to the present invention will be more evident from the following exemplifying and non-limiting description, referred to the enclosed schematic drawings in which:

Figure 1 is a perspective view of a isolator switch for medium and high voltage arranged in a rack, made according to the present invention and with the switch group only partially disengaged and extracted, Figures 2a and 2b are further perspective views of the single isolator switch of figure 1 inserted in the crossbar element, respectively top views and bottom views, engaged in a completely closed operative position and inserted under load,

Figure 3 is a view similar to that of figure 2, in which the circuit breaker group was rotated with respect to the fixed parts of the isolator switch, from which it results disengaged, and where a separation is made between the upper and lower sections,

Figures 4 and 5 are side elevation views of ends of that illustrated in figures 2 and 3, clarifying the two shown positions,

Figure 6 is a perspective view of the single circuit breaker group which shows the slide case, the elements contained therein and a closure cover of one end,

Figure 7 is a perspective view of a part of the elements of an enlarged step,

Figures 8 and 9 are cross sections rotated 90° from each other, of part of elements of one pole in a first position in which the control rod is found in an initial opening step,

Figures 10-11 are sections entirely similar to those of figure 8, in which subsequent steps are shown through which from the first open position, safely isolated and grounded, one arrives at a position in which the circuit breaker is reported in the closed position .

With reference to figure 1, a rack 11 is partially and schematically shown, made for example of a section bar, within which a compact isolator switch group for medium and high voltage 12 is mounted, built according to the present invention. The isolator switch group 12 can of course be made with the desired number of poles, as a function of the specific needs. The rack or framework 11 does not provide for any specific compartment for housing the current supply conductors or voltage bars, but only makes a housing for the under load group .

In the non- limiting embodiment represented in the drawings, the 3 -pole isolator switch is situated at a crossbar element 13 which also acts as a guide element for the case 14 of a circuit breaker group, indicated in its entirely with 15, rotatable with respect to the rack structure 11 and translatable, once rotated, with respect to and within the crossbar element 13 between an operative position contained within such crossbar element and a non-operative position extracted from such crossbar element 13.

In such a manner, with the circuit breaker group 15 extracted, there remains within the box 11 only the ground wire and the fixed parts of the isolator switch connected to upper connectors and to lower connectors 16 and 17 .

The case 14 acts as a slide on the crossbar element 13, when the switch 15 is in the rotated and disconnected position, permitting its extractability from the box 11.

Figures 4 and 5 show how, according to the invention, section bars 40 are used which, in the disconnected circuit breaker position, act on one side as ground wire elements as well as stable guide elements of the switch 15 in its extraction step. On the other side, such stable guide element is made by a T bar 41 fixed to the crossbar element 13, where it acts as a stop for the rotation. A further rotation stop is also arranged on the upper part, in 47, where it too acts as an extraction guide. A pair of ground plates 48 is placed on the sides of the inner bodies of the circuit breaker, creating a protected separation. It is also indicated how the circuit breaker 15 is rotatable between the inserted operative position and the rotated position, ready for the extraction, due to the presence of bearing elements 42, integral with the crossbar element 13, which act on a load-bearing core 43. Such core 43 is made, for example, in the front part of the circuit breaker 15, where it can be fixed. The central portion of the front bears a rod device 49 for the initial separation for the disconnecting of the pliers of the isolator switch (arrow F in figure 2b, towards the left for the observer) , as well as for the insertion of the same in the operative position (arrow F in figure 2b, towards the right for the observer) . More in particular, the invention provides that within the 3 -pole case 14, an operating stem 18 is arranged, one end thereof exiting from an open control end of the case 14.

The operating stem 18 is constrained by means of a pivoting 19 between the ends of two flanking arms 20 which constitute a fork-type square lever 10. In the centre, the two arms 20 are pivoted in 21 to a fixed support 22, of box type, which surrounds both the operating stem 18 and the square lever 10. The pivoting 21 has an axis parallel to that of the pivoting 19. The other free end of the two arms 20, in a hole 23, constrains an end of a helical spring 24, such spring 24 at its other end in turn being constrained to a notch seat 25 of an extension 126 of a movable contact 26 arranged within each vacuum shell 44 of the single pole. The fixed contact 29 is also placed within such shell 44. Flexible junction plates 46 connect the extension 126 of the movable contact with the outside.

Such extension 126 of the movable contact has lateral pins 27, arranged perpendicular to the displacement axis of the movable contact 26, which is inserted in externally-open slots 28 made in the fixed support 22. These lateral pins 27 act as guide elements of the extension 126 of the movable contact 26 in its operating movement between an engagement position and a disengagement position with respect to the fixed contact 29. Inside the shells 44, between the movable contact 26 and the external case of the shell 44, elastic elements 45 are arranged which tend to maintain the movable contact 26 and the fixed contact 29 in a normally engaged position. The elastic force developed by such elastic elements 45 inside the shells and acting on the movable contact 26 is at least equal to the minimum elastic starting force developed by the helical springs 24, reason for which there is an arrangement of open movable 26 and fixed 29 contacts (figs . 8 and 9) .

Figure 6 shows, in an exploded representation, the circuit breaker group 15, the case 14 and the various elements arranged alongside the related portions containing them.

Figures 8 - 11 show the steps which lead to the operative closure of the contact by means of the actuation of the operating stem 18.

Figure 1 shows a position in which the case 14 is in the extraction step from the crossbar element 13 outside of the rack 11, with complete disengagement between the parts. With the operating stem 18 and the additional related elements in disengaged position, the case 14 is inserted, acting as a slide, in the crossbar element 13 within the rack 11. In such a manner, the position is assumed of the parts as shown in figure 5, and from such position the case 14 is rotated until it is brought into the position shown in figure 4, in which the circuit breaker group 15 is ready to become operative . At this point, the actuation occurs of the operating stem 18, according to the various steps illustrated in the additional respective detail drawings .

Figures 8 and 9 show an initial step as described above .

Figure 10 in fact illustrates a second step in which a first movement of the operating stem 18 causes a rotation for a certain arc of the square lever 10, which begins to drive open the pair of helical springs 24. The springs 24, in turn at the other end, begin to act under traction on hollow seats of the extension 126 of the movable contact 26. In these steps, the interaction between the elastic elements 45 and the helical springs 24 allow an advancement of the movable contact 26 which is positioned against the fixed contact 29. Figure 11 shows how, due to the continued rotation of the square lever 10, the movable 26 and fixed 29 contacts, already engaged, undergo an overpressure thrust. This occurs since the helical spring 24, which develops a greater thrust, has overcome the smaller force developed by the elastic elements 45 due to the continued advancement of the operating stem 18, so to achieve the final operating engagement.

In this final stable engagement position, there is a complete contact of the finding, in which the operating stem 18 has completed its forward travel (remaining locked) and has determined the stable engagement between the contacts 26 and 29. The square lever 10 has completed its rotation, bringing itself into a functioning dead centre. It is clear that only one step has been discussed here, but the same occurs also for the remaining steps of the group of the invention.

Consequently, in this position, the compact isolator switch for medium and high voltage of the present invention is activated in complete safety.

From such position, in fact, should the operator have to intervene, he will have to disengage the operating stem 18 from the position just indicated as attained (figure 11) to that initially described (figures 8 and 9), before being able to proceed to the rotation of the case 14 with the related parts inserted therein.

Only once such manoeuvre has been carried out can the operator proceed with the rotation of the case 14 by an angle of 90°, passing from the position of figures 2 and 4 to that of figures 3 and 5.

Once this operation has been completed as well, the operator can proceed with the extraction of the case 14 from the crossbar element 13 in complete safety, as shown in figure 1.

Moreover, it should be underlined how the spaces occupied by a compact isolator switch for medium and high voltage according to the present invention are actually limited to the minimum, with considerable advantages for its placement in the plant.

Consequently, it is indicated how an isolator switch according to the present invention has an extremely compact structure, even if it ensures great safety. The operator is reassured since he can detect on his own that the electrical isolation has occurred and is effective, due to the extraction of the circuit breaker group.

Claims

1. Three-pole positionable compact isolator switch for medium and high voltage, set in a rack structure (11) at a crossbar element (13) which acts as a guide element for a case (14) of a circuit breaker group (15), said case being rotatable with respect to the rack structure (11) and translatable, once rotated, with respect to and within the crossbar element (13) between an operative position contained within such crossbar element and a non-operative position extracted from such element (13), said circuit breaker group (15) being arranged between upper connectors and lower connectors (16, 17) integral with said crossbar element (13), inside said case (14) an operating stem (18) being translatable for the engagement and disengagement of a movable contact (26) and a fixed contact (29) for each pole, wherein each movable contact (26) is maintained in the engagement and disengagement positions by the collaboration of return springs (24, 45) , identifying the various positions through a respective forked square lever (10) connected by means of pivoting (19) to said operating stem (18) .

2. Isolator switch according to claim 1, characterised in that said square lever (10) for each pole is pivoted (in 19) to a fixed support (22) arranged within said case (14), said fixed support (22) providing externally-open slots (28) adapted to receive lateral pins (27) externally projecting from said movable contact (26, 126) .

3. Isolator switch according to claim 1, characterised in that said square lever (10) for each pole is in the form of a fork which provides two flanked arms (20) , between which said operating stem (18) is arranged at a first end, pivoted in (19) .

4. Isolator switch according to claim 3, characterised in that said forked square lever (10) for each pole at its second ends provides for, inserted in upper holes (23), one end of a spring (24) of a pair of springs (24) , which at the other end are integral with said movable contact (26, 126) .

5. Isolator switch according to claim 4, characterised in that said movable contact (26) is extended downward into an extension (126), on which said ends of the springs (24) are constrained.

6. Isolator switch according to claim 1, characterised in that the circuit breaker group (15) is translatable with respect to said crossbar element (13), when placed in non-operative position, on one side along a section bar (40) that, in the disconnected circuit breaker position, acts as ground wire element of the circuit breaker group (15) , and on the other side along a T bar (41) fixed to said crossbar element ( 13 ) .

7. Isolator switch according to claim 1, characterised in that the circuit breaker group (15) has, constrained thereto, a load-bearing core (43) rotatable on bearing elements (42) integral with the crossbar element (13).