GB2143089A

GB2143089A - Switchgear

Info

Publication number: GB2143089A
Application number: GB08414875A
Authority: GB
Inventors: Minoru Nakahata; Chitoshi Ogura; Nobuyuki Orito; Teruaki Suginaka
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1983-06-10
Filing date: 1984-06-11
Publication date: 1985-01-30
Also published as: GB2143089B; GB8414875D0; DE3421265A1; DE3421265C2

Abstract

Switchgear for connecting a load 20 to a ring main power distribution circuit comprises a pair of load switches 36, 38 in series with the ring 18, and a power feeder switch consisting of a vacuum switch 50 and a disconnectlng switch 48 in series, there being no fuse on the power feeder side. The entire switchgear is SF6 insulated. <IMAGE>

Description

SPECIFICATION Switchgear This invention relates to switchgear and more particularly to switchgear particularly suitable for use in a power distribution network.

A typical power distribution system comprises an annular or ring-shaped power distribution network connected to an electric source and the network includes series-connected switchgear which are groups of switches for distributing electrical power to a desired power consuming system connected thereto. Generally, a conventional switchgear includes two load switches for closing and opening the power distribution network and a power feeder switch connected between the load switches. The load switches are connected in series with each other in the ring-shaped circuit and at least one pair of the load switches is always open to supply the electrical power to the load through the power feeder switch. When any trouble occurs in the distribution network, the load switches may be selectively switched on or off to achieve desired power distribution.The conventional switchgear also comprises a power fuse connected in series with the power feeder switch for protecting the load side equipment.

If any trouble occurs in the load side system, a power fuse in the switchgear circuit melts to open the circuit. The melted fuse may be replaced with a new fuse after opening the power feeder switch and connecting it to earth through a closed grounding switch. When trouble occurs in the ring-shaped circuit network, the load switches may be selectively opened or closed to enable the loads to receive power from the power supply through the circuit network.

Thus, in the conventional switchgear, since a power fuse is used, protection in the overload region is difficult and remote operation is impossible. Also, since air is used as the main insulation, the structure becomes bulky and is sensitive to surface pollution.

Accordingly, an object of the present invention is to provide switchgear in which the above mentioned disadvantages of the conventional switchgear are obviated.

Another object of the present invention is to provide switchgear in which no power fuse is employed and many disadvantages associated with the power fuse are eliminated.

Still another object of the present invention is to provide switchgear in which there is no need for replacing the power fuse, a reliable electrical insulation is ensured, and in which the overall size of the switchgear is made smaller.

Accordingly, the switchgear for use in a power distribution circuit network of the present invention comprises two load switches for connecting and disconnecting the power distribution circuitry; a power feeder switch connected between said load switches for supplying electric power therefrom; and an operating mechanism for operating said switches; characterized in that said power feeder switch comprises a vacuum switch. The switchgear may further comprise a hermetically sealed housing for containing therein said load switches and said vacuum interrupter, and an electrically insulating gas filled within said housing.

The present invention will now be described in more detail in conjunction with the embodiment of the present invention taken in conjunction with the accompanying drawings, in which: Fig. 1 is a circuit diagram illustrating a power distribution system; Fig. 2 is a circuit diagram illustrating a switchgear constructed in accordance with the present invention.

Fig. 3 is a front view showing the switchgear of the present invention; Fig. 4 is a side view of the switchgear shown in Fig. 3; Fig. 5 is a partial view illustrating the operating linkage for interlocking the load switches and the disconnect switch and showing the position for opening both the load switches and the disconnect switch; Fig. 6 is a view similar to Fig. 5 illustrating the position in which the load switches are closed while the disconnect switch is closed; Fig. 7 is a view similar to Fig. 5 illustrating the position in which the load switches are open and the disconnect switch is closed immediately after the disconnect switch is allowed to move into the open position.

Referring now to the drawings and more particularly to Fig. 1, in which a typical ring-main power distribution system is schematically illustrated, a ring-shaped power distribution circuit network 10 is supplied with electric power by a power transformer 12 having one end thereof connected to an electric power source (not shown) and the other end thereof to a circuit interrupter 14. The ring-shaped power distribution circuit network 10 comprises a plurality of switchgears 1 6 connected at their inputs 1 8 in series with each other in a loop. The outputs 20 of the respective switchgears 1 6 are connected to a plurality of loads 22 through loadside transformers 24, respectively.

The switchgear 1 6 comprises, as shown in Fig.

2, a hermetic housing 26 filled with an electrically insulating gas 28 such as an SF6 gas, a pair of source side terminal conductors 30 and 32 connected at respective one end thereof to the inputs 18 and extending through the housing 26, and a load side terminal conductor 34 connected at one end thereof to the output 20 and hermetically extending through the housing 26.

The respective other ends of the source side terminal conductors 30 and 32 are connected to load switches 36 and 38, respectively, which are connected in series by a connecting conductor 40. The load switches 36 and 38 include grounding terminals 42 and 44, respectively. The load side terminal conductor 34 is connected at its other or inner end to the connecting conductor 40 between the load switches 36 and 38 through a power feeder switch 46 which comprises a disconnecting switch 48 and vacuum switch 50 serially connected to the disconnecting switch 48.

The disconnecting switch 48 has a grounding terminal 52. The switchgear 1 6 further comprises an operating mechanism 54 for operating the various switches 36, 38, 48 and 50 in the switchgear 1 6 in desired operating modes.

With the above arrangement, when the movable contacts of the switches 36 and 38 are moved into the closed position and the disconnect switch 48 as well as the vacuum switch 50 of the power feeder switch 46 are closed, electrical power is supplied to the load 22 through the transformer 24 from the ring-main power distribution circuit network 1 0. When the movable contacts of the switches 36,38 and 48 are brought into contact with the grounding terminal 42, 44 and 52, respectively, their respective movable contacts are connected to earth. In this connection it is to be noted that the vacuum 8 switch 50 should be closed after the disconnect switch 48 is closed, i.e., after the movable contact of the disconnect switch 48 is connected to the connecting conductor 40 or the grounding terminals 52.

According to the present invention, since a vacuum interrupter is employed in place of a power fuse, there is no need for replacing the fuse after a conductor therein has been melted, and, accordingly, a remotely operated recovering operation is possible. Also, reliable electrical insulation is provided making the overall size of the switchgear smaller. Further, a wide range of electrical currents can be interrupted by the vacuum interrupter. Also, since all the components are contained within a hermetic housing filled with an electrically insulating gas, reliable insulation is obtained and the operating life of the switchgear is lengthened.

Figs. 3 and 4 illustrate one example of a threephase switchgear 1 6 constructed in accordance with the present invention. The switchgear 1 6 comprises a hermetic housing 26 filled with an electrically insulating gas such as SF6 gas. The walls of the housing 26 support electrical bushings 60 and 62 through which the source side terminal conductors 30 and 32 respectively extend, and an electrical bushing 64 for the load side terminal conductor 20. The ends of the load side terminal conductors 30 and 32 inside of the housing 26 have mounted thereon movable contact blades 66 and 68 pivoted at pivots 70 and 72, respectively. The movable contact blades 66 and 68 are connected to insulating operating rods 74 and 76, respectively, which are connected to operating levers 78 and 80 mounted on operating shafts 82 and 84, respectively.By actuating the operating shafts 82 and 84 by the operating mechanism 54, the movable contact blades 66 and 68 can be actuated between a closed position shown in Fig.

3 in which the blades 66 and 68 are in contact with contact elements on the connecting conductor 40, and a grounded position in which the movable contact blades 66 and 68 separate from the connecting conductor 40 and engage the grounding terminals 42 and 44, respectively.

The connecting conductor 40 is supported in the housing 26 by an insulator 86, and the grounding terminals 42 and 44 are also rigidly supported within the housing by a suitable support (not shown). In the closed position, the source side terminal conductors 30 and 32 are connected to each other through the contact blades 66 and 68 and the connecting conductor 40, and in the grounding position, the source side terminal conductors 30 and 32 are grounded to earth. The movable contact blades 66 and 68 can also be positioned in an open position in which the movable contact blades 66 and 68 are separated from both the connecting conductor 40 and the grounding terminals 42 and 44 and stay between the closed and the grounding positions.

The switchgear 1 6 of the present invention further comprises the disconnecting switch 48 including a movable contact blade 88 connected to the operating mechanism 54 so that the blade 88 is selectively moved to rotate about a shaft 90 between the closed position shown in Fig. 3, the open position and the grounding position. The operating mechanism 54 includes an operating shaft 91 which, when rotated, causes the movement of the disconnecting switch 48. In the illustrated closed position, a contact element on the connecting conductor 40 engages the movable contact blade 88 so that the conductor 40 is electrically connected to the vacuum interrupter 50 through a rigid conductor terminal 92 and a flexible conductor 94 connected to a movable contact rod 96 of the vacuum interrupter 50. The movable contact rod 96 is actuated by a rotatable shaft 97 of the operating mechanism 54.When the movable contact blade 88 is moved into the open position by the operating mechanism 54, the blade 88 separates from the connecting conductor 40, and when the contact blade 88 is in the grounding position, it engages with the grounding terminal 42.

The operating mechanism 54 for the load switches 36 and 38 as well as the disconnecting switch 48 is interlocked to the vacuum switch 50 by an operating linkage 98 connected between the operating shafts 91 and 97 so that the movable contact 96 of the vacuum interrupter 50 engages or separates from a stationary contact 100 of the vacuum switch 50 according to the mode of operation of the switches 36,38 and 48.

Figs. 5 to 7 illustrate the interconnecting linkage 98 between the operating shafts 91 and 97 for interlocking the vacuum switch 50 and the disconnecting switch 48 shown in Figs. 3 and 4.

As previously described in conjunction with Figs.

3 and 4, the rotation of the operating shaft 91 causes the opening and closing movements of the movable contact blade 90 of the disconnecting switch 48 through the links connecting the operating shaft 91 to the blade 90. Similarly, the rotation of the operating shaft 97 causes the opening and the closing movements of the movable contact rod 96 of the vacuum interrupter 50 through the linkage between the operating shaft 97 and the movable contact rod 96.These operating shafts 91 and 97 are interconnected by the linkage 98 which comprises a lever 102 secured on the operating shaft 91, an operating link 1 04 pivotally connected at one end thereof to the tip of the operating lever 102 by a pin 106, a connecting link 108 connected at one end thereof by a pin 110 to a midpoint of the operating link 104, and a lever 1 12 pivoted by a pin 1 14 at one end thereof to the other end of the link 108 and secured at the other end thereof to the main shaft 97. The operating linkage 98 further comprises a latch 11 6 pivotally mounted on a stationary pin 120, a trigger lever 122 pivotally supported on a stationary pin 124, and a spring lever 126.

The latch 116 is biased in the counterclockwise direction about the pin 120 in Fig. 5 by a torsion spring 128 of which one end engages the latch 116 while the other end of the spring 128 is connected to the spring lever 126 by a pin 130 at one end of the lever 126. The other end of the spring lever 1 26 is pivotally connected to the pin 110 which connects the operating link 104 and the connecting link 1 08. The trigger lever 1 22 is also biased by a torsion spring 132 in the clockwise direction. The spring 1 32 is wound around the pin 124 and engages at one end thereof with a stationary pin 134 and at the other end thereof with a pin 136 mounted on the trigger lever 122.The operating linkage 98 further comprises a tension spring 138 for closing the disconnecting switch 48 connected between a stationary pin 140 mounted on a structural member of the switchgear and a pin 142 mounted on the end of the operating link 104 remotest from the end on which the pin 106 is mounted. In the illustrated position, the pin 142 engages the connecting link 108, and prevents further clockwise rotation of the link 104 relative to the link 108. The pin 106 connecting the operating lever 102 and the operating link 104 has rotatably mounted thereon a roller 144 which is brought into a rolling contact with the cam surface 146 of the latch 1 6. The latch 1 6 also comprises a first and a second latch surface 148 and 150, respectively, engaging the trigger member 122.The first latch surface 148 is in engagement with the trigger member 122 in the position shown in Fig. 5, and the second latch surface 1 50 is in engagement with the trigger member 122 in the position shown in Fig. 6. The trigger member 122 comprises an engaging end 1 52 which engages the second latch surface 150 of the latch member 116 in the position shown in Fig. 6.

In Fig. 5, when the operating mechanism 54 causes the operating shaft 97 to rotate clockwise to close the vacuum switch 50 through the linkage as shown in Fig. 3, the lever 112 secured to the shaft 97 transmits the rotational force through the connecting link 108, the operating link 104 and the operating lever 102 to the operating shaft 91 to rotate the shaft 91 clockwise. The clockwise rotation of the operating shaft 91 is transmitted through the linkage to the movable contact blade 88 of the disconnecting switch 48 shown in Fig. 3 to move the blade 88 into its closed position shown in Fig. 3.It is to be noted that the length relationship between the levers 112, 102 and the links 104, 108 and the angular relationship of the levers 102 and 112 relative to the shaft 91 and 97, respectively, are properly selected such that the movable contact blade 88 engages the contact element on the connecting conductor to close the disconnecting switch 48 prior to the closure of the vacuum switch 50.

After the closure of the vacuum switch 50 and the disconnecting switch 48 has been completed, the operating link 104 is moved in an upper position in which spring energy is stored in the torsion spring 128, and after the completion of the clockwise rotation of the operating lever 102, the latch member 1 16 is rotated clockwise about the pin 120 so that the roller 144 on the pin 106 may contact the cam surface 146 of the latch member 11 6, and therefore, the engaging end 1 52 of the trigger member 122 engages the second latch surface 1 50 as shown in Fig. 6, thereby holding the latch member 116 and the operating lever 102 in the illustrated position in which the disconnecting switch 48 and the vacuum switch 50 are in the closed positions.

When the vacuum interrupter 50 is tripped open by a trip mechanism included in the operating mechanism 54, the main operating shaft 97 rotates counterclockwise from the position shown in Fig. 6 into the position shown in Fig. 7 which is similar to that shown in Fig. 5.

This counterclockwise rotation of the shaft 97 also causes a counterclockwise rotation of the operating link 104 about the pin 106 which, together with the shaft 91 held in the same position as shown in Fig. 6, is held stationary in this mode of operation. This counterclockwise rotation of the operating link 104 causes the tension spring 1 38 to be stretched.Just before the operating link 104 completes its rotation, it pushes the trigger pin 1 36 on the trigger member 122 to rotate the latter counterclockwise about the pin 1 24 against the clockwise spring force of the spring 1 32. Then, the engagement between the second latch surface 1 50 of the latch member 11 6 and the engaging end 1 52 of the trigger member 122 is released to release the latch member 116 under the biasing spring force of the spring 128. Since the spring 128 is charged at this time due to the lowered position of the pin 130 disposed on the spring lever 126 and due to the counterclockwise rotation of the operating link 104, the latch member 1 16 rotates counterclockwise about the pin 120, with the roller 144 on the operating lever 102 rolling along the cam surface 146 of the latch member 116. When the roller 144 moves off from the cam surface 146 of the latch member 1 16, the operating link 104 is rotated clockwise due to the tension stored in the spring 1 38 to rotate the operating shaft 91 also in the counterclockwise direction, thereby opening the disconnecting switch 48. It is to be noted that the dimensions of the various components of the above-described operating mechanism are selected such that the time between the opening of the vacuum switch 50 and the opening of the disconnecting switch 48 is not less than one cycle.

With the above arrangement, the disconnecting switch is interlocked with a vacuum interrupter by a specially designed linkage, so that the operating intervals of the disconnecting switch and the vacuum interrupter are stable, thereby ensuring a current and voltage interruption. Also the space required for mounting the switches is reduced.

Claims

1. A switchgear for use in a power distribution circuit network, comprising: two load switches for connecting and disconnecting the power distribution circuitry; a power feeder switch connected between said load switches for supplying electric power therefrom; and an operating mechanism for operating said switches: characterized in that said power feeder switch comprises a vacuum switch.

2. A switchgear as claimed in claim 1 , further comprising a hermetically sealed housing containing therein said load switches and said vacuum switch and an electrically insulating gas filling said housing.

3. A switchgear as claimed in claim 1 or 2, wherein said power feeder switch further comprises a disconnecting switch serially connected to said vacuum switch.

4. A switchgear as claimed in any one of claims 1 to 3, wherein said load switches and said disconnecting switch are connectable to earth.

5. A switchgear as claimed in any preceding claim, wherein said operating mechanism comprises a linkage connected between said load switches and said disconnecting switch.

6. A switchgear as claimed in claim 5, wherein said linkage includes a mechanism for opening said disconnecting switch after the opening of said vacuum switch.

7. Power switchgear substantially as herein described with reference to Figures 2 to 7 of the accompanying drawings.