Patent Publication Number: US-4256934-A

Title: Disconnecting switch arrangement

Description:
The present invention relates to a disconnecting switch arrangement, and more particularly to a high voltage disconnecting switch equipped with an earthing device for use particularly in a metal clad insulated substation in an electric power system. 
     In recent years, the spot network system has been developed for electric power systems. In the spot network system, metal insulated substations are inevitable in order to reduce the space for installing the substation. A disconnecting switch is used to disconnect the busbars of a power line from electrical equipment after the current from the power line is interrupted by some other switching device such as, for example, a vacuum interrupter. Accordingly, a number of disconnecting switches are used in a metal clad insulated substation in a spot network system together with the other electrical equipment such as circuit breakers, and transformers. Further, a number of earthing devices are required in a high voltage metal clad insulated substation in order to ground the electrical equipment after the busbars are disconnected from the electrical equipment by the circuit breakers and disconnecting switches. 
     In the prior art, a disconnecting switch and an earthing device are normally installed individually in a metal clad insulated substation, and such a separate disconnecting switch and earthing device must allow for a large radius of rotation of the contact blades. Accordingly, in such installations, the relative spacing of the high voltage apparatus and conductors, irrespective of the exact geometric shape of the high voltage components of the system, must be equal to at least the theoretical minimum flash over distance between points, because the electrical fields are extremely inhomogeneous. The waste of space is therefore considerable because in most of the space provided, the field strengths are actually very low. Such a conventional metal clad insulated substation, therefore, is large and expensive. 
     In one use, the disconnecting switch is employed to disconnect an excitation current of a primary winding of a transformer. In this case, a secondary current of the transformer is interrupted by a circuit breaker such as a vacuum interrupter for interrupting the load current. After the secondary winding of the transformer is disconnected from a load line, the excitation current, however, must be interrupted by the disconnecting switch. It is, however, undesirable to interrupt the current using a conventional disconnecting switch, because a complicated and castle operating unit is required to obtain a high speed disconnection, and a wide disconnecting area is necessary for making the disconnecting distance so long. 
     It is, therefore, an object of the present invention to provide an improved high voltage disconnecting switch arrangement which requires comparatively little space in the direction of the switching movement so that in multi-phase installations the disconnecting switch and the earthing device can be arranged in a very small space. 
     It is a further object of the present invention to provide a disconnecting switch arrangement suitable for underground use which is reliable, economical and easily operated. 
     It is still another object of the present invention to provide a disconnecting switch arrangement as described above which is capable of modifications and adaptations, particularly for being used to interrupt a relatively low current, and including an arcing contact member. 
     With above objects in view the invention provides basically for a disconnecting switch arrangement for disconnecting a busbar from an electrical machine and for earthing the electrical machine, comprising, in combination, at least one disconnecting unit including a stationary contact member having a contact portion and a common stationary contact member positioned spaced apart a constant distance from said stationary contact member and connected to said electrical machine and a common movable contact member for connecting stationary contact member, at least one earthing unit for grounding said electrical machine and including an earthing contact member, said common stationary contact member and said common movable contact member for connecting the common stationary contact member and the earthing contact member, and an actuating unit for operating said common movable contact member so as to be alternately connected electrically between said stationary contact member and said common movable contact member of the disconnecting unit and between said common movable contact member and said earthing contact member of the earthing unit. 
     The novel features which characterize the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which: 
    
    
     FIG. 1 is a diagram of an example of a substation in which a disconnecting switch arrangement is used, 
     FIG. 2 is a sectional side view showing one phase of a three-phase high voltage disconnecting switch arrangement in accordance with the present invention, 
     FIG. 3 is a sectional elevation of a disconnecting switch arrangement along line III--III of FIG. 2, 
     FIG. 4 is a sectional side view of a disconnecting unit and an earthing unit forming a part of the arrangement in accordance with the present invention, taken along line IV--IV of FIG. 3, 
     FIG. 5 is a side view of a disconnecting switch arrangement in accordance with the present invention, looking along arrow V in FIG. 3, 
     FIG. 6 is a side view of a supporting member forming a part of an actuating unit in a disconnecting switch arrangement according to the present invention, 
     FIGS. 7 to 13 are side views corresponding to FIG. 4, of modifications of the present invention each of which shows the operation of a disconnecting unit equipped with an arcing contact member, and 
     FIG. 14 is a sectional elevation of a disconnecting unit and an earthing unit forming a part of the arrangement in accordance with the present invention, the section being taken along line XIV--XIV. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, there is shown a substation of an electric power system, which employs a high voltage disconnecting switch arrangement according to the present invention. The disconnecting switch arrangement comprises, substantially, a first disconnecting unit 2a which is electrically connected to a power line 8 and an interrupting unit 6, a first earthing unit 4a for grounding the line to an item of electrical equipment such as the interrupting unit 6 after the power line 8 is disconnected from the interrupting unit 6 by the first disconnecting unit 2a, a second disconnecting unit 2b which is electrically connected between the interrupting unit 6 and a load line 10, and a second earthing unit 4b for grounding the line part of the interrupting unit 6 after the interrupting unit 6 is disconnected from the load line 10 by the second disconnecting unit 4b. 
     The disconnecting units 2a and 2b and the earthing units 4a and 4b are, in this case, contained in a first tank 12 which is filled with insulating oil. The interrupting unit 6 is contained a second tank 14. 
     Certain words are used in this specification indicating direction, relative position, and the like. Such words are used only as seen in the particular drawings of embodiments, and the parts so described may, in actual use, have different directions, relative positions, and the like. Examples of such words are &#34;upper&#34;, &#34;lower&#34;, &#34;vertical&#34; &#34;horizontal&#34;. 
     FIG. 2 shows the mechanical construction of the disconnecting switch arrangement of FIG. 1. As is shown in FIG. 2, an adapter plate 16 is fixed hermetically and liquid-tightly to the first tank 12 by bolts 18. On the inner surface 16a is provided the first disconnecting unit 2a, the first earthing unit 4a,  the second disconnecting unit 2b and the second earthing unit 4b. 
     The first disconnecting unit 2a comprises a stationary contact member 20 mounted on the inner surface 16a of the adapter plate 16, a common stationary contact member 22 at a standard spacing from the stationary contact member 20 and a common movable contact member 26a which is described in more detail below. The first earthing unit 4a comprises the common stationary contact member 22 and an earthed contact member 24 at the same standard spacing from the common stationary contact member 22 as the stationary contact member 20, and the common movable contact member 26a. 
     The second disconnecting unit 2b comprises a stationary contact member 28 mounted on the inner surface 16a of the adaptor plate 16 in the same way as the stationary contact member 20 of the first disconnecting unit 2a, a common stationary contact member 30 at the standard spacing from the stationary contact member 28, and a common movable contact member 26b. The second earthing unit 4b comprises the common stationary contact member 30, an earthed contact member 32 which is mounted on the inner surface 16a of the adaptor plate 16 at the standard spacing from the common stationary contact member 30, and the common movable contact member 26b. 
     Three pairs each of the disconnecting units 2a, 2b and the earthing units 4a, 4b are provided, in this embodiment, to form a three-phase circuit which consists of an U-phase, a V-phase and a W-phase, as is shown in FIG. 3. 
     As illustrated in FIG. 2, the interrupting unit 6 consists of three interrupting devices in the form of vacuum interrupters 6u, 6v and 6w, but vacuum interrupter 6v and 6w are not visible in the drawing. 
     As is shown in FIGS. 2 and 3, the stationary contact member 20 of the disconnecting units 2a for the U, V and W phases are connected to busbars 8u, 8v and 8w respectively of the power line 8. The busbars 8u, 8v and 8w pass through cable heads 34u, 34v and 34w which are secured to the first tank 12 by an insulating board 36a. The busbars 36u, 36v and 36w are turned perpendicularly to the busbars 8u, 8v and 8w, and pass through an insulating spacer 36b to connect to another power line (not shown in the drawing). The common stationary contact member 22 is electrically connected to the stationary contact side of the interrupting member 6 which is in this embodiment in the form of the vacuum interrupters 6u, 6v and 6w by connecting conductors 38u, 38v and 38w. The connecting conductors 38v and 38w are not shown in the drawings. 
     In the second disconnecting unit 2b, each of the common stationary contact members 30 is connected to the switched side of the vacuum interrupters 6u, 6v and 6w by way of connecting conductors 40u, 40v and 40w. Conductors 40v and 40w are not illustrated in the drawing. Furthermore, each of the stationary contact members 28 is connected to the load line 10 by way of conductors 42u, 42v and 42w (see FIG. 3), through a connector head 44. An additional earthing unit 46 earthed by a lead 48 is provided so as to be switched on and off between a fixed contact 44a mounted on the connector head 44. A conservator 50 is provided at an upper portion of the first tank 12. The first tank 12 is secured on a fixing base 52. The second tank 14 enclosing the interrupting unit 6 is mounted on a base plate 54a which forms part of an operating unit 54. 
     As is shown in FIG. 3, an actuating unit 56 is provided to operate the common movable contact units 26a and 26b. The actuating unit 56 includes a first operating rod 58a to which are mounted the common stationary contact members 24a for the U, V and W phases, and a second operating rod 58b to which are mounted the common stationary contact members 24b for the U, V and W phases in the same manner as the first operating rod 58a. The actuating unit 56 further includes first supporting members 60a pivotally supporting one end portion of the operating rods 58a and 58b and second supporting members 60b pivotally supporting the other ends of the operating rods 58a and 58b and a drive means 80 for actuating the common movable members 26a and 26b, through a connecting plate 62. 
     FIG. 4 shows a specific structure for the disconnecting units 2a and 2b and the earthing units 4a and 4b. As is best shown in FIGS. 3 and 4, a circular hole 16b is formed in the adaptor plate 16 and a conductive mounting plate 64 having a circular hole 64a is fastened to the adaptor plate 16 by a plurality of fastening bolts 18 as shown in FIG. 3. An insulated conductor assembly 72 is secured on the adaptor plate 16 to form the common stationary contact member 22. The insulated electrical conductor 72 is formed of an elongated electrical conductor 74 of fixed length and surrounded by a cone-shaped insulator 76. Both ends of the conductor 74 are exposed for connecting to other conductors. One end of the conductor 74 is formed as a contact portion 74a which has a smaller diameter and is adapted to be connected with and disconnected from the common movable contact member 26a or 26b, and the other end portion is connected to the conductor 38u, 38v or 38w to be connected to the unswitched contact side of the vacuum interrupter 6u, 6v or 6w. The cone-shaped insulator 76 is mounted on the adaptor plate 16 by holding a flange portion 76a between the adaptor plate 16 and the conductive fastening plate 64. An insulated conductor assembly 64 is formed with an elongated conductor 66 of fixed length with a circumferential insulating layer 68. One end of the conductor 66 projects from the insulator 68, and has an end portion formed with a smaller diameter a contact portion 66a which is connected to and disconnected from the common movable contact member 26a or 26b. A connector portion 66b is also provided at the same end of the conductor 66. The insulator 68 of the insulated conductor assembly 66 is secured by a screw 70 so as to construct the stationary contact member, at the current spacing from the conductor 72 of the common stationary contact member 22. An earthing conductor 78 is spaced at the same standard distance from the insulated electrical conductor 72 of the common stationary contact member 22 and is aligned with respect to the insulated conductor 66 of the stationary contact member 20 and the insulated conductor 72 of the common stationary contact member 22. One end of the earthing conductor 78 is formed as a smaller diameter contact portion 78a to be connected to and disconnected from the common movable contact member 26a or 26b, and the other end of the electric conductor 78 is formed as a threaded portion 78b. To construct the earthing member 24, the earthing conductor 78 is fixed to the conductive plate 64 which is grounded by suitable means. The common movable contact member 26a or 26b is formed of a pair of contact blades 25 and 27, a connecting rod 29 and an insulating member 31. At portions near each end, the blades 25 and 27 are separated by spacers 33 and held together by screws 70. One end of the connecting rod 29 is embedded in one end portion of the insulating member 31. The other end portion of the connecting rod 29 has a flattened portion which is inserted into the gap formed between the contact blades 25 and 27, and is fastened to the contact blades 25 and 27 by a screw 70, at a central portion of the contact blades 25 and 27. A base portion of the insulating material 31 is fixed to the operating rod 58a or 58b of the actuating unit 56 in order to connect the common movable contact member 26a or 26b respectively with the actuating unit 56. 
     FIGS. 3 and 5 show the actuating unit 56 of a disconnecting switch arrangement according to the present invention. As described above the actuating unit 56 comprises the actuating rods 58a and 58b to which are mounted the common movable contact members 26a and 26b, first supporting members 60a and second supporting members 60b which support and pivotably connect to the actuating rods 58a and 58b, and the drive means 80. 
     As is shown in FIGS. 3 and 5, a pair of first supporting members 60a are mounted on the inner side 16a of the adaptor plate 16, spaced apart at a given distance from each and in alignment with each other. The drive means 80 is also mounted on the adaptor plate 16 in an intermediate position between the first supporting members 60a. In the first supporting member 60a, a base plate 84 is attached to the adaptor plate 16 by suitable fastening means, and a support 86 is fixed to the base plate 84 by a fixing plate 88 and bolts 18. A U-shaped trunnion 90 is mounted on the support 86. A link 92 is pivotably connected to the trunnion 90 by a pin 94, and the link 92 is pivotably engaged with the actuating arm 62 by a connecting pin 96. In the drive means 80, an electric motor 82 is mounted on the adaptor plate 16 by means of an H-shaped spacer 98. A support such as a U-shaped channel member 100 is fixed to the adaptor plate 16 by a base plate 102 and a fastening flange 104 and bolts 18. Thus, the base plate 102 is fixed to the inner side 16a of the adaptor plate 16. The fastening plate 102 is fastened to one end of the U-shaped channel member 100 by welding, and the fastening flange 104 is fixed to the base plate 102 by bolts 18. Bearings 106 are mounted on both end portions of the channel member 100. A driving shaft 108 is supported by the bearings 110 so that one end portion passes through the fastening plate 104, the base plate and an oil sealing 112, and the extreme end of the driving shaft 102 is coupled with the shaft 82a of the motor 82. The other end of the driving shaft 108 supports a driving bevel gear 114a. As shown in FIGS. 3 and 5, a U-shaped trunnion 116 is mounted on the channel member 100 by a plate 118. A shaft 120 supporting a driven bevel gear 114b which meshes with the driving bevel gear 114a  is mounted rotatably in the trunnion 116 so as to be perpendicular to the driving shaft 108. One end of a lever 122 is fixedly attached to the rotating shaft 120, and the other end is pivotably connected to an intermediate portion of the actuating rod 62 by a pin 124. 
     As best seen in FIG. 6, for each of the second supporting members 60b, a base plate 126 is secured to the inner surface 16a of the adaptor plate 16 by welding or similar means. A pair of supports in the form of channel members 130a and 130b are secured to the base plate 126 by fixing plates 128a and 128b which are fastened to one end of channel members 130a and 130b, respectively, by bolts 18. Fastening plates 132a and 132b are secured to the other end of channel members 130a and 130b, respectively. Furthermore, a U-shaped trunnions 134a and 134b are fastened to fastening plates 132a and 132b. A lever 136a is pivotably connected to the trunnion 134a by a pin 138a. An end portion of the lever 136a is pivotably connected to a connecting plate 142 by means of a connecting pin 140. One end of a lever 136b is rotatably mounted to the trunnion 134b by a pin 138b. The other end portion of the lever 136b is rotatably connected by a fixed pin 144 to the end of the actuating rod 58a or 58b. 
     In operation, each of the busbars 8u, 8v and 8w of the power line 8 is connected to a first disconnecting member 2a and the first disconnecting member 2a is connected to the interrupting unit 6. The interrupting member 6 is engaged with the second disconnecting member 2b, and the second disconnecting member 2b is connected to the load cable 10 through the connector head 44. Accordingly, as illustrated in FIG. 2, the busbar 8u, 8v or 8w is electrically connected to the load cable 10 by way of the first disconnecting unit 2a, the interrupting unit 6 and the second disconnecting unit 2b. 
     In order to disconnect the load cable 10 from the busbars 8u, 8v and 8w, the interrupting unit 6 is actuated initially to interrupt the current flowing from the power line 8 to the load cable 10. After the actuation of the interrupting unit 6, the first and second disconnecting units 2a and 2b must be actuated to disconnect the load cable 10 from the busbar 8u, 8v and 8w of the power line 8. After the power line 8 is disconnected by the disconnecting units 2a and 2b from the load cable 10, the interrupters must be grounded in order to discharge any electric charge stored in them. In a disconnecting switch arrangement in accordance with the present invention, the disconnecting units 2a and 2b are interlocked with the earthing unit 4a and 4b by the operation of the common movable contact members 26a and 26b, which are actuated by the actuating unit 56. When the power line 8 is electrically connected to the load cable 10, as is shown in FIGS. 2 and 3, the common movable contact member 26a connects the stationary contact member 20 to the common stationary member 22 is the first disconnecting unit 2a and, in the same manner, the common movable contact member 26b connects the stationary contact member 28 to the common stationary contact member 30. 
     In this condition, when the driving shaft of the actuating unit 56 is rotated by the motor 82 in the clockwise direction as seen from the right in FIG. 5, (arrow l 1 ), the driving bevel gear 114a turns the driven bevel gear 114b in the clockwise direction as indicated by arrow l 2 , and thereby the lever 122 attached to the shaft 120 of the driven bevel gear 114b rotates in the same direction about the shaft of the driven gear 114b. The rotation of the lever 120 is transmitted to the connecting lever 62 and thereby the connecting lever 62 being pivotably supported by the first supporting members 62a and the second supporting members 62b by means of the levers 92, 138a and 138b, moves through a semicircular path as indicated by a broken line. As the movement of the connecting rod 62, the operating rods 58a and 58b are moved together with the connecting rod 62. The movement of the operating rods 58a and 58b makes the contact blades 25 and 27 move in the same direction so that the contact blades 25 and 27 disconnect from the disconnecting members 2a, 2b and connect to the earthing members 4a, 4b as shown by a broken line in FIGS. 4 and 5. 
     In the earthed and disconnected condition, the connection operation can be performed by the reverse operation to the disconnecting operation described above. Namely, the motor is rotated in an anti-clockwise direction, turning the driving shaft 102 in an anti-clockwise direction as seen from the right in FIG. 5 (arrow l 3 ), and thereby the driving bevel gear 114a drives the driven bevel gear 114b in the anti-clockwise direction. The rotation of the driven gear 114b is transmitted to the common movable contact members 26a and 26b by the link 122, the connecting arm 62 and the operating rods 58a and 58b to perform the semicircular motion. By this movement of the common movable contact member 26a and 26b in the anti-clockwise direction, the common movable contact members 26a and 26b are isolated from the earthing members 4a and 4b, respectively and thereafter are connected to the disconnecting units 2a and 2b, respectively. 
     According to the disconnecting switch arrangement described above, because of the construction of the movable contact members 26a and 26b driven by the rotating lever 122, the range of travel of the movable contact members can be made relatively small, and therefore the equipment can be used as a compact alternating current device. Furthermore, since the movable contact members, stationary contact members and drive means of the disconnecting units and earthing or grounding units are used in common an interlock between the disconnecting unit and the earthing or grounding unit is intrinsic. There is thus no need to provide such an interlock separately, so that part are saved and the construction is siplified. 
     FIGS. 7 to 14 show a modification of the disconnecting switched arrangement in accordance with the present invention. In the modified form of the disconnecting switch arrangement, there is provided an arcing member contact 150 for interrupting the arc current which flows between the common movable contact member 26a or 26b and the stationary contact member 20 or 28 or the common stationary contact member 22 or 30 of the disconnecting unit 2a or 2b, if the disconnecting unit 2a or 2b is used, for example, to interrupt an energizing current of a transformer (not shown in the drawing). 
     As shown in FIGS. 7 to 14, the arcing contact member 150 includes an arcing contact means which consists of a long and slender conducting plate 152, a link 154 which connects a base portion of the conducting plate plate 152 to a common movable contact member 26a or 26b, a contact driving means for driving the electric conductive plate 152 and a disconnecting delaying means for delaying the electrical disconnection of the common movable contact member 26a or 26b from the stationary contact members 20 or 28 and 22 or 30. The contact driving means includes a spring 162 which is interposed between the conducting plate 152 and a projection 168 formed on the common movable contact member 26a or 26b. Thus, one end of the spring 164 is engaged with the conducting plate 152 by a fixed pin 166, and other end is engaged with a projection 168 on the connecting rod 29. A base portion of the contact plate 152 is pivotably connected to an end portion of the lever 154 by an engaging pin 160, and a base portion of the lever 154 by a pin 158. The disconnection delaying means includes a roller 156 provided between the plate 152 and the lever 154 by the pin 160. The disconnection delaying means further comprises a conductor 66 of the stationary contact member 20 or 28 longer than conductor 74, a groove 176 formed in a contact portion 74a of the conductor 74, an engaging pin 170 which is embedded in the contacting portion 74a, an axial recess 172 provided on the contacting portion 66a of the conductor 66 and a groove 174 provided on the surface of an intermediate portion of the conductor 66. 
     Operation will now be described with reference to the disconnecting switch arrangement as constructed above. 
     FIG. 7 shows a connecting condition of a disconnecting unit 2a or 2b. In the connecting condition of the disconnecting units 2a and 2b, the conductor 66 of the stationary contact member 20 or 28 is connected to the conductor 74 of the common stationary contact member 22 or 30 by means of the contact blades 25 and 27 of the common movable contact member 26a or 26b. In this case, the arcing contact member 150 connects electrically between conductors 76 and 74. In this case, the curved end portion 152a of the arcing contact 152 is positioned in the groove 176 of the contact portion 74a of the conductor 74 and engaged with the engaging pin 170. The roller 156 engages in the recess 174 in the conductor 66. 
     As the common movable contact member 26a or 26b is moved in the direction indicated by arrow l 4 , the the movable contact blade is separated from the contact portion 74a of the conductor 74 while the roller 156 slides over the recess 174 and drops in the recess 172, and the common contact blade 25 or 27 is still engaged with the contacting portion 66a of the conductor 66, as is shown in FIG. 8. 
     In this case, the spring is gradually stretched and the excitation current of the transformer flows through the arcing blade 152, as shown in FIG. 8. As the common movable contact blade 25 or 27 moves further, when the roller 156 is located at the extreme end of the contacting portion 66a, the end portion 152a disengages from the engaging pin 170 and thereby the arcing contact 152 is swiftly rotated about the roller 156 in the counter clockwise direction. Now the arcing contact blade 25 or 27 is fully separated from the contacting portion 74a so that no arc is generated therebetween. The common movable contact member is fully separated from the both of the stationary contact member 20 or 28 and the common stationary contact member 22 or 30, as shown in FIG. 9. In this situation the common movable contact member 26a or 26b is further moved through a semicircular path in clockwise direction as shown by an arrow l 5 , the common movable blade engages with the contacting portion 74a of the conductor 74 and the earthed conductor 78 to ground the equipment, as shown in FIG. 10. 
     From the state of FIG. 10, when the common movable contact member 24a or 24b is moved back in the counter-clockwise direction, the common movable contact 25 or 27 contacts initially with the contacting portion 66a of the stationary contact member 20 or 28, as is shown in FIG. 11. Under the condition shown in FIG. 11, the roller 156 engages with the step of the recess 172 and the arcing contact 152 is pulled in the clockwise direction, and thereby the intermediate portion of the arcing contact 152 is pressed against a projecting portion 29a thereof. When the common movable contact member 26a or 26b moves through the semicircular path as indicated by arrow l 7 , the movable contact blades 25 and 27 contact with the contact portion 74a of the conductor 74, as is shown in FIG. 12. As the common movable contact member 26a or 26b continues to move, when the end portion 152a of the arcing contact 152 hits on the stopping pin 170, the turning force in the counter-clockwise direction is applied to the arcing contact 152 and then the arcing contact 152 rotates in an anti-clockwise direction about its end portion 152a. By the rotation of the arcing contact 152, the roller 156 slides over the step of the recess 172 and thereafter drops into the recess 174 of the conductor 66. Immediately after the roller 156 drops into the recess 174, the roller 156 is engaged with the stepping portion of the recess 174 as is shown in FIG. 13. In the state shown in FIG. 13, the arcing contact 152 is pulled by a component force of the tension of the spring 162, and slides on the projecting end of the connecting rod 29. From the state shown in FIG. 13, when the common movable contact blades 25 and 27 are further moved in the direction shown by arrow l 9 , the arcing contact 152 springs upward as seen in the diagram and thereafter its end portion 152a engages with the engaging pin 170 as shown in FIG. 7. 
     According to the above described modification of the present invention the movable contact members and actuating linkages including the arc prevention mechanism are shared between the disconnecting units and and the earthing or grounding units. Therefore it is possible to make a disconnecting switch arrangement according to the present invention which is of compact design and simple construction. Furthermore, the speed of disconnection of the contacts which would otherwise arc, is made very high, giving an arc prevention means of very high reliability. Therefore a simple and compact disconnecting switch arrangement for both connecting and disconnecting an excitation current and earthing or grounding equipment is provided by the present invention. 
     While the present invention has been described in terms of a preferred embodiment and a modification thereof this is not to be taken as limitative of the present invention as many additions and modifications thereto will be apparent to those skilled in the art but the invention is rather to be taken as defined by the appended claims. 
     It will be understood that each of the elements described above or two or more together, may also find a useful application in other types of high voltage disconnecting switch arrangements differing from the types described above. 
     While the invention has been illustrated and described as embodied in high voltage disconnecting switch arrangement with turnable common movable contact members, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.