GB2040580A - An actuating and locking device for a switching installation - Google Patents

Abstract

An actuating and locking device, in particular for use in a medium voltage switching installation, comprises a bus bar system (4), a disconnecting means (2), a power or load switch (1, 5), earth and measuring contacts accessible through ports (3) and a cable terminal (8). The disconnecting means (2) comprises a double throw switch having an operative position (Fig. 1) and an earthing position (Fig. 3). The power or load switch (1, 5), the double throw switch (2) and the cable access ports (3) are mutually locked such that the measuring contacts (3) are accessible only in the earthed cable condition. <IMAGE>

Description

SPECIFICATION An actuating and locking device for a switching installation The invention relates to a three phase medium voltage switching installation generally completely embedded and insulated by a potting resin and the like comprising essentially a bus bar system, a disconnecting means, a power or a load switch, measuring contacts and a cable terminal. This device may however also be used for high voltage installations.

A switching installation of this type is known among others from a publication in Holecpost, 1970, Nr. 1, pages 6-21, inclusive. The switching installation known from this publication comprises a fixed and a mobile part, which can be wheeled out, the fixed part including the bus bars and the cable terminal both accommodated in a sheet steel casing and the mobile part including essentially the power switch mounted on a switching carriage.

In case of such a mobile switching installation one may wheel out the switch after interrupting the power or load switch and disconnection of the bus bar and the switch whereupon the earthing installation may be connected to the switch and the cable may be earthed in a reliable and completely safe manner through the switch by wheeling in the switch followed by switching in the switch. For subjecting the cable to tests and measurements the switch has likewise to be wheeled out whereupon the cable contacts become free and will be accessible for the measuring instruments. After performing the measurement operation these measuring contacts are completely covered by wheeling in the switch so that the system will be completely insulated again.

Earthing the cable which has to be attended to is a means for protecting those who have to work on the cable. However, the earthing per se is an operation not without risks. There exists for that matter the possibility of earthing parts under tension for instance by choosing a wrong group and not or insufficiently ascertaining whether the cable to be earthed is tension-free indeed.

Accordingly this risk has to be minimized by earthing the cable via the power or load switch like in the above mentioned device. Before completing such an earth connection there will thus have to be completed a disconnection between the bus bar system and the cable whereupon the cable is wheeled out and the earthing set is connected. After wheeling in again the cable will then be earthed via the power switch.

In main feediny stations, industrial Tnstailations and similar large stations in which by virtue of working regulations requirements have to be met with respect to the possibility of wheeling out and changing the switch, the above mentioned installations that may be wheeled out will show full advantage also with respect to earthing the cable for the purpose of measurements.

In smaller stations wherein the possibility of wheeling out and changing the switch is not of decisive importance such installations that may be wheeled out are however relatively expensive in view of the very possibility of wheeling out.

Moreover the switching installations that may be wheeled out will require a larger surface area when compared with fixedly mounted switching installations whereby the compactness and consequently also the total investment costs among others for a building are disadvantageously affected by such an installation which may be wheeled out.

In order to reduce these total investment costs for smaller stations it is attractive to rely on the use of switching installations having a fixed construction. However together with the omission of the possibility of wheeling out also the possibility of utilizing this possibility of wheeling out for measurement and earthing purposes disappears so that a solution for these operations has to be found in another suitable and consequently safe and reliable manner in which there should be maintained the other favourable properties of the switching installation which may be wheeled out such as the complete insulation thereof. Especially for such switching installations having a fixes construction a real problem constituted the provision of measurement and earthing contacts accessible only under predetermined conditions.

The present invention now provides a medium voltage installation satisfying the last mentioned requirements in which the said problems have been solved and which is characterized in that the disconnecting means is embodied in a disconnecting double throw switch having an operative position and an earthing position; that measurement and earthing contacts may be closed up by means of lockable cable access ports and that the power or load switch, the disconnecting double throw switch and the cable access ports are mutually locked in such a manner that the measurement and earthing contacts are accessible only in the earthed condition of the cable.

In order to warrant the safety of the device according to the present invention in a simple and perfect way, the invention furthermore provides means for locking the disconnecting double throw switch and the cable access ports when the power or load switches have been closed and for dislocking the disconnecting double throw switch when the power or load switch has been opened, the opened power or load switch being locked in every intermediate position of the disconnecting double throw switch which locking will be released in the locked earthing position of the disconnecting double throw switch; the locking of the cable access ports being released when the power or load switch has been closed and the disconnecting double throw switch has been locked in its earthing position; and the disconnecting double throw switch being locked in its earthing position when the cable access ports have been opened while the power or load switch may freely be switched on and off.

A preferred embodiment of an actuating and locking device according to the present invention is characterized by a first locking cam cooperating with a flap for closing up the cable access ports which first locking cam keeps the closing up flap in its closed position by means of a stop provided on a lever for actuating the disconnecting double throw switch when the disconnecting double throw switch is in its operative position; a second locking cam also cooperating with the closing up flap which second locking cam keeps the closing up flap in its closed position by means of a locking cam provided on the driving means of the power or load switch when the power or load switch is in its open position; coupling means connected to the disconnecting double throw switch and to a locking bar so that said coupling means are moved simultaneously with the disconnecting double throw switch when actuating the disconnecting double throw switch which coupling means may lock the disconnecting double throw switch either in its operative position or in its earthing position by means of a locking means capable of locking the locking bar at one of its two ends thereof, which locking means may be operated by a locking lever and an actuating bar connected thereto; a stop provided on the locking lever preventing the power or load switch from being switched in on the ones hand by means of a locking crank when the disconnecting double throw switch has been released and preventing on the other hand the locked disconnecting double throw switch from being released when the power or load switch has been opened; a second stop coupled with said second locking cam locking the locked lever for the actuating bar when the closing up flap has been opened.

The invention will now be described in further detail with reference to the drawings in which an embodiment has been represented.

Figures 1, 2 and 3 show a device according to the present invention together with the corresponding circuit arrangements in the three different positions; Figure 4 shows a preferred embodiment of the actuating and locking device according to the invention.

With reference to Figures 1 to 3 inclusive it will be clear that the power or load switch 1 may connect the cable 8 to the fixed contacts 5 of the power or load switch 1, which contact 5 has been connected to the upper connection contact of the disconnecting double throw switch 2. By means of this disconnecting double throw switch 2 the latter contact may be connected to the lower contact which has been connected to the bus bar 4. When the connecting bar of the disconnecting double throw switch 2 is in its upper position the upper end of this connecting bar will be connected to the earthing strip 6 so that the cable 8 will be connected to earth when the power or load switch 1 has been closed.

With reference to Figure 1 in which the switching installation has been shown in its operative condition the disconnecting double throw switch 2 is in its operative position and the power or load switch 1 has been closed so that the cable 8 and the bus bar 4 have been connected to each other via the mobile and the fixed contact 5 of the power or load switch 1 and the disconnecting double throw switch 2. In the operative condition the power or load switch 1 may freely be switched off and thereupon be switched in. When the power or load switch 1 has been switched in both the disconnecting double throw switch 2 and the cable access ports 3 will however be locked, thus preventing a load being switched off by means of the disconnecting double throw switch 2 and likewise preventing a dangerous voltage being accessible via the measuring the earthing contacts.If now the power or load switch 1 is opened the locking of the disconnecting double throw switch 2 is released. IR in the latter case the disconnecting double throw switch 2 is brought from its operative position into the earthing position the power or load switch 1 will be locked in its opened position like indicated in Figure 2. The cable access ports 3 will then also be locked. Only when the disconnecting double throw switch 2 has been brought completely in its earthing position the power or load switch 1 may again be closed like indicated in Figure 3. The cable 8 may then be connected to the earthing strip 6 by means of the power or load switch 1, i.e.

via the mobile and the fixed contact 5 and the disconnecting double throw switch 2.

In order to get access to the measurement and earthing contacts for measurement or earthing operations the power or load switch 1 has to be switched in first of all however by means of which the locking of the cable access ports 3 is released and the measurement and earthing contacts have been earthed with certainty. When the cable access ports 3 are accessible the disconnecting double throw switch 2 has been locked in order to prevent a possible disconnection of the earthing on the bus bar side. When the cable access ports 3 are opened the power or load switch 1 may freely be switched in and off, respectively, thus providing for the earthing of the cable 8 and the possibility to perform measurements on said cable, respectively.

With reference to Figure 4 there has been shown an embodiment in which the described locking may be achieved in a switching installation according to the invention.

In order to render it possible to lock the disconnecting double throw switch 2 shown in the operative condition this switch has been coupled with a locking bar 11 by means of an U-shaped coupling plate 29. At the two ends thereof the locking bar 11 has been provided with annular grooves 1 2 by means of which the locking bar 11 may be kept within a key shaped hole 10 in a locking strip 30 thus keeping the disconnecting double throw switch 2 also in the fixed position due to the coupling via the coupling plate 29.

In the shown position the discqnnecting double throw switch 2 is in the operative position thereof and the bus bar 4 has been connected to the fixed contact 5 of the power or load switch 1. In order to bring the disconnecting double throw switch 2 into the earthing position the U-shaped coupling plate 29 has to be moved up by means of the actuating lever 27 and the connecting strip 28 fixed to the actuating lever 27 and the U-shaped coupling plate 29 so that the disconnecting double throw switch 2 is likewise raised by means of the insulated pulling bar 9 connected to the Ushaped coupling plate 29 and will connect the fixed contact 5 of the power or load switch 1 to the earthing strip 6.Before the disconnecting double throw switch may be brought into its earthing position the locking bar 11 will first of all have to be released by moving the locking strip 30 in the direction indicated by an arrow A so that the annular groove 12 will not be locked any longer within the more narrow part of the key shaped hole 10. The locking bar 11 may then freely be moved within the larger part of the key shaped hole 10 so that also the disconnecting double throw switch 2 coupled to said locking bar 11 by means of the coupling plate 29 may freely be moved and may be brought into the earthing position. Upon reaching the earthing position the lower annular groove 1 2 will be present in the key shaped hole 10 so that the disconnecting double throw switch 2 may again be locked in this position.

The locking strip 30 may be moved to and fro by means of a locking lever 13 one end of which is present within a recess in the locking strip 30 fitting about said locking lever 13 and which at the other end thereof may be operated by means of an actuating bar 14 while the locking lever 13 may be rotated about a fulcrum 23 mounted close to the locking strip 30.

In the shown opened position of the power or load switch 1 the locking lever 13 may freely be moved. When the power or load switch 1 of which only the driving shaft 19 has been represented is closed by rotating the driving shaft 1 9 in the direction indicated by the arrow B a locking crank 18 fixedly mounted on the driving shaft 19 will also be rotated in the direction C so that this crank will reach such a position that the forward movement of the locking lever 13 in the direction of the arrow D is blocked because a stop 15 mounted on said locking lever 13 will engage the locking crank 18. Hence the locking of the disconnecting double throw switch 2 may not be released in the closed position of the power or load switch 1.By means of the locking crank 18 and the stop 1 5 there is likewise attained the result that upon release of the disconnecting double throw switch 2, i.e. the locking lever 13 being in the forward position, the stop will be positioned below the locking crank 1 8 so that the locking crank 18 and consequently also the driving shaft 1 9 may not be rotated to the left for switching in the power or load switch 1.

The cable access ports 3 and consequently also the measurement contacts 32 may be closed up by means of a closing flap 20 rotatably mounted by means of hinging arms 25 and 26, respectively.

To the hinging arm 25 there has been fixedly connected an arm 24 the upper end of which has been fixed to a transverse strip 1 7 constituting a first locking cam 22 at its left hand end. The actuating lever 27 has been provided with a stop 21 in such a manner that in the shown operative position of the disconnecting double throw switch 2 this stop 21 prevents the closing up flap from being opened because the first locking cam 22 is arrested by the stop 21. If the disconnecting double throw switch 2 has not been locked the actuating bar 27 may however always freely be moved up and down by means of the locking bar 11 and the locking strip 30.In this instance "not locked" means that the stop 1 5 on the locking lever 1 3 is positioned below the locking crank 1 8 so that the power or load switch i may not'be switched in.

As long as the disconnecting double throw switch 2 is in the operative position and consequently the actuating lever 27 is in the lower position the closing up flap 20 cannot be opened.

Furthermore the opening of the closing up flap 20 is also dependent on the position of the power or load switch 1, that is in such a manner that the closing up flap may only be opened when the power or load switch 1 has been switched in. For achieving this result the transverse strip 1 7 terminates upwardly at the right hand side in a second locking cam or pushing strip 1 6. This pushing strip 16 is of such a shape and length and has furthermore been provided at such a location that the free end of the pushing strip 1 6 will be just below the extension of the locking crank 18 when power or load switch 1 has been opened and the closing up flap 20 has been closed. Not shown guide means prevent the pushing strip 16 from optionally being pushed away sideways.When the closing flap 20 is opened in the direction of the arrow F the pushing strip 1 6 will be urged upward which upward movement in the shown position is prevented by the extension of the locking crank 18. Thus the pushing strip 1 6 may be moved upwardly and the closing up flap 20 may be turned down only when the power or load switch 1 is in its closed position For preventing a release of the locking of the disconnecting double throw switch 2 when the closing up flap 20 has been opened the pushing strip 1 6 has been coupled to the second locking cam 22 by means of the transverse strip 17. This transverse strip 17 now constitutes a stop for the locking lever 13. In the opened position of the shutting flap 20 the stop 1 7 will for that matter be present at the location facing the end of the locking lever 13 opposite to the locking strip 30 so that the actuating bar 14 may not be moved in the direction indicated by the arrow K and the locking lever 1 3 may thus not be moved and the locking of the disconnecting double throw switch may not be released either.

The shutting flap 20 may only be opened when the disconnecting double throw switch 2 is in its upper earthing position and has been locked and the power or load switch 1 is in its closed position.

When the closing up flap 20 has been opened and the pushing strip 16 is in its upper position the power or load switch may be opened because the closing up strip 16 has been mounted resiliently so that the locking crank 1 8 may push the pushing strip sideways. When the power or load switch 1 remains in its opened position and the closing up flap 20 is closed the pushing strip 1 6 will spring back again so that it will again be blocked by means of the locking crank 1 8.

The invention being thus described it will be obvious that the same is not restricted to the embodiment represented and discussed above but that modifications and variations thereof are possible without departure from the spirit and scope of the invention.

Claims (7)

1. An actuating and locking device, for a switching installation, comprising a bus bar system, a disconnecting means, a power or load switch, earth and measuring contacts and a cable terminal, the disconnecting means being embodied in a disconnecting double throw switch having an operative position and an earthing position, lockable cable access ports to close up the measuring contacts, wherein the power or load switch, the disconnecting double throw switch and the cable access ports are mutually lockable in such a manner that the measuring contacts are accessible only in the earthed condition of the cable, means for locking the disconnecting double throw switch and the cable access ports when the power or load switch has been closed and for dislocking the disconnecting double throw switch when the power or load switch has been opened, the opened power or load switch being locked in every intermediate position of the disconnecting double throw switch which locking will be released in the locked earthing position of the disconnecting double throw switch, the locking of the cable access ports being released when the power or load switch has been closed and the disconnecting double throw switch has been locked in its earthing position, and the disconnecting double throw switch being locked in its earthing position when the cable access ports have been opened while the power or load switch may freely be switched in and off.

2. A device as claimed in claim 1, comprising a first locking cam co-operated with a flap for closing up the cable access ports, said first locking cam maintaining the closing up flap in its closed position by means of a stop provided on a lever for actuating the disconnecting double throw switch when the disconnecting double throw switch is in its operative position, a second locking cam also co-operating with the closing up flap, said second locking cam maintaining the closing up flap in its closed position by means of a locking cam provided on the driving means of the power or load switch when the power or load switch is in its opened ppsition, coupling means connected to the disconnecting double throw switch and to a locking bar so that said coupling means are moved simultaneously with the disconnecting double throw switch when actuating the disconnecting double throw switch, said coupling means being adapted to lock the disconnecting double throw switch either in its operative position or in its earthing position by means of a locking means capable of locking the locking bar at one of the two ends thereof, said locking means being operable by a locking lever and an actuating bar connected thereto, a stop provided on the locking lever preventing the power or load switch from being switched in by means of a locking crank when the disconnecting double throw switch has been released and preventing the locked disconnecting double throw switch from being released when the power or load switch has been opened, and a second stop coupled with said second locking cam locking the locked lever for the actuating bar when the closing up flap has been opened.

3. A device as claimed in claim 2, wherein the closing up flap comprises hinging arms, at least one of which is coupled with the first and second locking cams.

4. A device as claimed in claim 3, wherein the first and second locking cams each comprise an end of a strip connected to one of the hinging arms and the second locking cam consists of a pushing strip capable of arresting the locking crank.

5. A device as claimed in either claim 3 or claim 4, wherein the coupling means comprise a coupling plate to which one end of the locking bar and one end of a pulling bar of the disconnecting double throw switch have been connected, and both the locking bar and the pulling bar are guided through openings in a locking means located below the coupling plate, said locking means being in the shape of a locking strip by means of which the pulling bar may be locked in its extreme positions for locking the disconnecting double throw switch.

6. A device as claimed in claim 5, wherein the locking bar at each one of its ends is provided with an annular groove capable of co-operating with a slot debouching into the opening of the locking strip, the width of the slot being equal to the diameter of the annular groove, and the locking strip is movable in a transverse direction with respect to both the locking bar and the pulling bar and by means of the actuating bar connected to one end of the locking lever, the other end of the locking lever fitting in a recess in the locking strip and the locking lever being rotatable about a fulcrum mounted close to the locking strip.

7. An actuating and locking device for a switching installation substantialiy as hereinbefore described with reference to the accompanying drawings.