Patent Description:
Switchgears are switching mechanisms used to control and protect electrical equipment, such as equipment operated by utilities, commercial building owners, and operators of distributed renewable generation assets such as solar farms and wind turbines. Such switchgears include various medium voltage devices (e.g., devices rated for 12kV or 24kV) for a range of applications, such as a ring main unit (RMU).

For any given equipment specification or application, it is desirable to provide a reliable and compact switchgear with a small footprint. It is also desirable to provide a earthing disconnection switch (or disconnector and earthing switch) with three positions - on, off (or isolation), and earth - to facilitate in-situ testing of cable integrity and improve the ease of maintenance of the switchgear. It is particularly desirable to combine a three-position disconnector and earthing switch with a compact switchgear.

Document <CIT> discloses a knife switch including an operator device for moving a contact knife between a first open position and a second position in electrical contact with a contact element. A free end of the contact knife is provided with a dynamic electric field control device including an electrically conductive element.

The matter for protection is set out in the appended claims.

Disclosed herein is a switchgear, comprising a plurality of switching devices configured to disconnect a power supply from a load. Each switching device comprises: a plurality of poles, each pole associated with a respective switch having a fixed contact and a moveable contact, and an actuating mechanism comprising a shaft, the shaft configured to rotate to transfer an external input force to move the moveable contact and open or close the switches of the switching device. The plurality of switching devices are arranged along a first axis, and the plurality of poles of each switching device are arranged along a respective second axis perpendicular to the first axis. Each shaft is arranged perpendicular to the first axis and is configured to rotate around a rotational axis parallel to the second axes. By way of this depth-wise switchgear architecture, the width of the switchgear may be reduced. A more compact switchgear with a smaller footprint may therefore be provided.

In some examples, the switchgear further comprises a plurality of disconnector and earthing switches, each disconnector and earthing switch associated with a respective one of the plurality of poles, and each disconnector and earthing switch having a disconnector blade pivotable around a first end of the disconnector blade between three different positions. The three positions comprise: a first position in which the disconnector and earthing switch is closed and the power supply is connected to the load through the disconnector blade; a second, isolation, position in which the disconnector and earthing switch is open and the power supply is disconnected from the load; and a third position in which the power supply is disconnected from the load and a second end of the disconnector blade is electrically connected to an earthing contact. The earthing disconnection switch is a three-position disconnector and earthing switch, or 3PS.

When a three-position disconnector and earthing switch 3PS is provided in combination with the above-described switchgear architecture, a reliable device with a small footprint can be provided which can more easily tested in-situ (improve the ease of maintenance). In particular, the architecture can help allow a width of the switchgear product to be reduced, providing for a more compact switchgear whilst still allowing for provision of a three-position disconnector and earthing switch.

In some examples, the switchgear further comprises a housing having first and second side walls, wherein the switching devices are arranged along the first axis between the first and second side walls of housing.

Optionally, the first end of each disconnector blade is pivotably coupled to the respective switch, and wherein each disconnector blade is configured to rotate around the pivot from the first position to the second position, wherein the rotation is towards the second side wall of the housing.

In some examples, the second side wall comprises: an end insulator configured to contact, when the disconnector blades of the poles disposed proximate to the second side wall are in the second position, the second end of said disconnector blades; and/or an insulating sheet. In some examples, the second side wall comprises two shields, each shield comprising a metallic plate covered in an insulating material, wherein when the disconnector blades of the poles disposed proximate to the second side wall are in the second position, the second end of said disconnector blades is disposed between the two shields. The presence of insulating materials or sheets, even without physical contact, can act as an obstruction to help breakdown electrical current paths. This can help avoid dielectric failure, and may thereby improve dielectric performance.

In some examples, the switchgear further comprises a flexible link electrically connecting the first end of each disconnector blade and the moveable contact. This can facilitate movement of the disconnector blade. In some examples, each disconnector blade is operated by a four-bar crank rocker mechanism. Optionally, each disconnector and earthing switch is arranged between the respective switch and the shaft along a respective third axis perpendicular to the first and second axes.

In some examples, a plane in which disconnector blade rotates is offset from an operating axis of the respective switch. This offset can facilitate a greater degree of movement of the disconnector blade of the disconnector and earthing switch, which facilitates improved clearance between the first, second and third positions of the disconnector blade. Dielectric performance may therefore be improved.

In some example implementations, the switchgear further comprises a plurality of busbar assemblies, each busbar assembly comprising a plurality of main busbars and a plurality of branch busbars alternately arranged along the first axis, each main busbar extending parallel to the first axis to electrically connect corresponding poles of adjacent switching devices, wherein, when the disconnector blades are in the first position, the second end of each disconnector blade is electrically connected to a respective branch busbar, wherein each branch busbar is electrically coupled to a respective main busbar to provide a conduction path between adjacent switching devices.

Optionally, each branch busbar comprises a partially spherical end. This can help reduce end effects. Optionally, each of the plurality busbar assemblies is insulated at either end.

In some examples, each respective switch comprises a vacuum interrupter, wherein the moveable contact of the vacuum interrupter is moveable by the actuating mechanism and is arranged between the fixed contact of the vacuum interrupter and the shaft of the actuating mechanism.

In some examples, the switchgear is a three-way switchgear. The plurality of switching devices consist of: a first switching device; a second switching device; and a third switching device, wherein each of the first, second and third switching devices comprise three poles.

In some particular example implementations, the first switching device is a first load break switch LBS, the second switching device is a second load break switch LBS, and the third switching device is a vacuum circuit breaker VCB. The insulating material/sheets can be provided within the enclosure of the VCB, which can be formed in part by the second side wall of the housing. However, any other types and combinations of switches or switching devices can be used.

In some examples, the disconnector and earthing switch is a three-position switch, or 3PS. In some particular implementations, the 3PS is an off load 3PS switch. In some implementations, one off load three-position disconnector and earthing switch is in series with a vacuum circuit break VCB (an example implementation of a switching device) and two off load 3PS are in series with respective load break switches LBS (another example implementation of a switching device).

Optionally, the switchgear further comprises a plurality of disconnector and earthing switches, each disconnector and earthing switch associated with a respective one of the plurality of poles, and each disconnector and earthing switch having a disconnector blade pivotable around a first end of the disconnector blade between two or more different positions. The two or more positions comprise: a first position in which the disconnector and earthing switch is closed and the power supply is connected to the load through the disconnector blade; and a second position in which the power supply is disconnected from the load and a second end of the disconnector blade is electrically connected to an earthing contact. This can be implemented as a two-position earthing disconnection switch.

In some examples, the two or more positions further comprise a third, isolation, position in which the disconnector and earthing switch is open and the power supply is disconnected from the load. In some examples, the disconnector and earthing switch (also called an earthing disconnection switch) is a 3PS switch.

Also disclosed herein is a busbar assembly, comprising: a plurality of cylindrical main busbars, each comprising an inner hole extending through a length of the main busbar; a plurality of branch busbars, a first end of each branch busbar comprising a hole and a second end of each branch busbar comprising a spherical portion; and a threaded rod extending through the inner hole of each main busbar and the hole of each branch busbar. The threaded rod extends along a first direction between a first end and a second end. The plurality of main busbars and the plurality of branch busbars are alternately arranged on the threaded rod along the first direction. In some examples, each main busbar comprises an outer insulating sleeve colinear with the inner hole.

Also disclosed herein is a switchgear comprising the busbar assembly. The switchgear further comprises: a housing comprising first and second side walls offset along the first direction, the first side wall comprising a first insulating mount configured to threadably engage with the first end of the threaded rod and the second side wall comprising a second insulating mount configured to threadably engage with the second end of the threaded rod. In some examples, the first insulating mount is an insulating bush. In some examples, the second insulating mount is an epoxy insulator.

The following description is with reference to the Figures.

With reference to the schematic of <FIG>, an existing switchgear architecture is shown in plan (top down) view. This example switchgear is a <NUM>-way, <NUM>-phase (or <NUM>-pole) device with a two-position earthing disconnection switch (also termed a disconnector and earthing switch) having two positions (on, earth). The actual disconnector and earthing switch, or earthing disconnection switch, is not shown. The switchgear has multiple switching devices.

Each switching device of the switchgear (here the switchgear is shown with a combination of two load break switches LBS and one vacuum circuit breaker VCB) is arranged in a panel along a longitudinal direction <NUM> (or first axis <NUM>), with the phases/poles (L1, L2, L3) for each switching device similarly arranged along the longitudinal direction. This arrangement is termed herein a "longitudinal" or "width wise" orientation. In one specific example of an existing switchgear, such a longitudinal/width wise architecture provides a width w (along the longitudinal direction <NUM>) of <NUM>, with a depth d (along a transverse direction <NUM> perpendicular to the longitudinal direction) of <NUM>. However, it will be understood that switchgears may have other dimensions and may include any suitable combination of switch types.

With reference to the schematic of <FIG>, a new switchgear architecture in accordance with the present invention is shown in plan (top down) view. This example switchgear <NUM> is a <NUM>-way, <NUM>-phase (or <NUM>-pole) device with a three-position earthing disconnection switch (also termed a disconnector and earthing switch) having three positions (on, off or isolation, earth). The actual earthing disconnection switch, or disconnector and earthing switch, is not shown.

Each switching device (here the switchgear is shown with a combination of two load break switches LBS and one vacuum circuit breaker VCB) is arranged in a panel along a longitudinal direction <NUM>, but the phases/poles <NUM> (210a, 210b, 210c) for each switching device <NUM> (208a, 208b, 208c; in this particular example, LBS-208a, LBS-208b, VCB-208c) are arranged along the transverse direction <NUM> (the poles for each switch are arranged along a respective second axis <NUM>). This arrangement is termed herein a "transverse" or "depth wise" orientation. In one specific example of the proposed switchgear, such a transverse/depth wise architecture provides a width w (along the longitudinal direction <NUM>) of <NUM>, with a depth d (along a transverse direction <NUM> perpendicular to the longitudinal direction <NUM>) of <NUM>. However, it will be understood that switchgears with this orientation may have other dimensions and may include any suitable combination of switch types. For example, any switchgear may be provided with a plurality of switching devices, each switching device having a plurality of poles, arranged in accordance with the architecture of <FIG>.

In other words, the switchgear arrangement of <FIG> can be generally implemented for any switchgear comprising a plurality of switching devices configured to disconnect a power supply from a load. Each switching device comprises a plurality of poles, each pole associated with a respective switch having a fixed contact and a moveable contact, and an actuating mechanism comprising a shaft. The shaft is configured to rotate to transfer an external input force to move the moveable contact and open or close the switches of the respective switching device. The plurality of switching devices are arranged along a first axis (<NUM>). The plurality of poles of each switching device are arranged along a respective second axis (<NUM>) perpendicular to the first axis. Each shaft is arranged perpendicular to the first axis and is configured to rotate around a rotational axis parallel to the second axes.

By way of the novel switchgear architecture illustrated in <FIG>, the width of the switchgear product may be reduced, providing for a more compact switchgear whilst still allowing for provision of a three-position earthing disconnection switch (three-position disconnector and earthing switch). When a three-position disconnector and earthing switch is provided within the switchgear in combination with the above-described architecture, a reliable device with a small footprint can be provided which can more easily tested in-situ (improve the ease of maintenance).

The general switchgear architecture and its associated advantages will be discussed in more detail below with reference to example implementation details of the switchgear.

With reference to <FIG> and <FIG>, a perspective view and side view of a switchgear <NUM> is shown. The example of <FIG>, <FIG> is a three-way switchgear having three switching devices <NUM>: a first switching device 208a, a second switching device 208b, and a third switching device 208c. In this particular example implementation, the switchgear has a combination of two load break switches LBS <NUM>-a, <NUM>-b and one vacuum circuit breaker VCB-208c with an offload 3PS (three position disconnector and earthing switch). However, the switchgear is not limited to this example implementation, and any suitable combination of switching devices and earthing disconnection switch can be used.

The switching devices are provided within a housing <NUM> and are schematically divided by the dashed lines in <FIG>. Each of the first, second and third switching devices comprise three poles 210a, 210b, 210c arranged in a depth-wise or transverse direction <NUM> (as in <FIG>).

Each of the plurality of poles <NUM> is associated with a respective switch <NUM> having a fixed contact and a moveable contact, and an actuating mechanism comprising a shaft <NUM>. The shaft is configured to rotate to transfer an external input force from outside the housing <NUM> to move the moveable contact and open or close the switches of the poles <NUM> of the switching device <NUM>. The switching devices <NUM> are arranged along a first axis (<NUM>), and the plurality of poles <NUM> of each switching device are arranged along a respective second axis (<NUM>) perpendicular to the first axis. Each shaft <NUM> is arranged perpendicular to the first axis and is configured to rotate around a rotational axis parallel to the second axes <NUM> in response to user engagement or user interaction. One shaft <NUM> drives all the poles <NUM> of one of the switching devices 208a.

The housing has a first side wall 216a (the portion of the first side wall enclosing the switching components is not shown) and a second side wall 216b. The switching devices <NUM> are arranged along the first axis <NUM> between the first and second side walls 216a, 216b of housing <NUM>.

With further reference to <FIG> (<FIG>, <FIG>) and <FIG>, a switchgear <NUM> (which is an example implementation of switchgear <NUM>) also comprises a plurality of disconnector and earthing switches <NUM>, each disconnector and earthing switch associated with a respective one of the plurality of poles <NUM>. Each disconnector and earthing switch has a disconnector blade <NUM> which is pivotably connected, at a first end <NUM>, to the associated switch. The disconnector blade is arranged to pivot at this first end between three different positions, as is further illustrated in <FIG>.

Each disconnector and earthing switch <NUM> is arranged between the respective switch <NUM> (formed of the moving and fixed contacts) and the shaft <NUM> along a respective third axis <NUM> perpendicular to the first and second axes (in series with the switch <NUM>). The switch <NUM> is operated/actuated by a drive rod <NUM> which is connected to the shaft <NUM> to transfer the rotation of the shaft <NUM> in response to an external input force into movement of the moveable contact along the third axis <NUM>, which is also referred to herein as the operating axis. The moveable contact is moveable by the drive rod <NUM> of the actuating mechanism and is arranged between the fixed contact and the shaft <NUM> of the actuating mechanism.

In some examples, the switch <NUM> is implemented as, or comprises, a vacuum interrupter (or VI). The VI can be implemented as part of a VCB or other circuit breaker, or as part of any other type of switching device (such as the LBS described above). The top contact of the vacuum interrupter VI is the moveable contact, moveable by the actuating mechanism is response to rotation of the shaft <NUM>. With reference to <FIG>, the fixed contact of the vacuum interrupter VI is fixed to a bottom plate 216c of the housing <NUM> via a support plate (not shown). The bottom plate 216c and first and second sidewalls 216a, 216b at least partially define a switching compartment of the switchgear <NUM>, <NUM>. The switching compartment described herein is air insulated, however any other insulating medium which fulfils the required dielectric / thermal requirements (such as a vacuum, pressurised air, SF6 (sulphur hexafluoride) or other gaseous dielectric medium, or inert gas) may be provided within the switching compartment.

A housing of the VI covers the fixed and moving contacts and is bolted to the support plate. Column supports formed of an insulating material (not shown) can be bolted between the support plate and the bottom plate 216c to hold the support plate within the switching compartment of the housing <NUM>. In this particular example, the VI is mounted on a bushing <NUM>. The bushing <NUM> is bolted to the bottom plate 216c and is fixed to the support plate with epoxy.

The VI housing acts as a support for the hinge or pivot point at the first end <NUM> of the disconnector blade <NUM> (see e.g., <FIG>). The first end of each disconnector blade is pivotably coupled to the respective switch <NUM>. The first end of the disconnector blade <NUM> can be pivotably coupled to the switch between the moveable contact and the shaft <NUM>. In this particular example, the first end of the disconnector blade <NUM> is pivotably coupled to a top of the VI housing which surrounds the fixed and moveable contacts of the switch.

A metallic shield (not shown) can be provided within the VI housing, placed between the moveable contact and the first end of the disconnector blade. The metallic shield acts to help shield the disconnector blade and the hinge/pivotable coupling from any electric field within the vacuum interrupter. As discussed above, the moving contact moves within the VI housing in response to actuation/rotation of the shaft <NUM>. In particular, rotation of the shaft <NUM> actuates the drive rod <NUM> of the actuating mechanism, pulling the moveable contact along the operating axis towards the shaft <NUM> and opening the switch <NUM>.

In the following example, the disconnector and earthing switch is described with reference to a 3PS disconnector and earthing switch. However, it will be understood that the switchgear architecture described can be implemented without any disconnector and earthing switch, or with any disconnector and earthing switch having two or more positions. With reference to <FIG> and <FIG>, the disconnector blade <NUM> is arranged in a first position in which in which the 3PS disconnector and earthing switch is closed and the power supply is connected to the load through the disconnector blade (via a busbar, as discussed further below). This current path is shown further in <FIG>. In this first position, current flows through the switchgear <NUM> via the fixed and moveable contacts and the disconnector blade. The switchgear <NUM> further comprises a flexible link <NUM> electrically connecting the first end <NUM> of each disconnector blade and the respective moveable contact. By using a flexible link <NUM>, movement of the moving contact relative to the fixed hinge/pivot point of the disconnector blade <NUM> is facilitated, allowing actuating of the switch <NUM>.

In response to user actuation of a direct break mechanism <NUM> (shown in <FIG>), the disconnector blade is moved from the first position to a second position, which is shown in <FIG>. The direct break mechanism <NUM> comprises a second shaft and a second actuating mechanism which is operated by rotation of the second shaft. A user can rotate the second shaft by turning or rotating an external handle, and the second actuating mechanism is rotated in response to rotation of the shaft. In this example, the second actuating mechanism is a four-bar crank rocker mechanism <NUM>, but any suitable actuating/driving mechanism may be used. In particular, in response to rotation of the second shaft of the direct break mechanism <NUM>, the disconnector blade is configured to rotate around the pivot from the first position to the second position, wherein the rotation is towards the second side wall 216b of the housing. In some examples, the second side wall forms part of the switching device 208c, which can be a vacuum circuit breaker, VCB. In other words, the second side wall can form part of the enclosure of the VCB.

The operation of the direct break mechanism <NUM> can be dependent on the particular combination of switching devices and disconnector and earthing switch. In this particular example, the disconnector and earthing switch is an off load 3PS arranged in series with the switch <NUM>, which is implemented as part of a VCB (switching device). The 3PS can be operated only when the VCB is in open position, and interlocking mechanisms are provided accordingly. The 3PS direct break mechanism <NUM> will interlock with the VCB mechanism to ensure the switchgear is operated as per switchgear standard mechanical interlock requirements. An example operation is set out below:.

In the second position of <FIG>, the 3PS disconnector and earthing switch is open and the power supply is disconnected from the load (the current path between the load and the power supply through the disconnector blade <NUM> is broken). This second, intermediate position is an isolation position in which the disconnector and earthing switch is "off" or isolated. The disconnector blade <NUM> can be moved into this off or isolation position without a corresponding actuation of the switches <NUM> of the switching devices <NUM> of the switchgear (i.e. independent of rotation of the shaft <NUM>) - as discussed above, in some implementations (such as when the disconnector and earthing switch is an off load 3PS) this operation is dependent on the switching device (e.g. the VCB) being in an open state.

In response to further user actuation of the second shaft of the direct break mechanism <NUM> in the same direction of rotation, the disconnector blade is moved from the second position to a third position, which is shown in <FIG>. In particular, the disconnector blade is configured to rotate around the pivot from the second position to the third position, wherein the rotation is again towards the second side wall 216b of the housing. In the third position, the power supply is disconnected from the load and a second end <NUM> of the disconnector blade is electrically connected to an earthing contact <NUM>. The disconnector blade <NUM> can be moved into this earthed position without a corresponding actuation of the switches <NUM> of the switching devices <NUM> of the switchgear (i.e. independent of rotation of the shaft <NUM>) - as discussed above, in some implementations (such as when the disconnector and earthing switch is an off load 3PS) this operation is dependent on the switching device (e.g. the VCB) being in an open state.

The disconnector and earthing switch <NUM> can thus be activated or controlled via mechanism <NUM> independently of the shaft <NUM> which controls or actuates the moving contact of the switches. In the example described above, the disconnector blade <NUM> is coupled to a fixed component (the housing of the VI) and is therefore decoupled from the actuation of the switch <NUM>; in other words, actuation of the switchgear <NUM>, <NUM> via shaft <NUM> does not actuate the disconnector and earthing switch <NUM>. However, it will be understood that in other examples the second actuating mechanism (of the disconnector and earthing switch) can be configured such that, when the moving contact is opened by shaft <NUM> to disconnect the power supply from the load, the disconnector blade <NUM> of the disconnector and earthing switch is correspondingly moved to the third, earthed, position. In this way, the current path through each respective switch <NUM> of the switchgear <NUM>, <NUM> is automatically opened in two different locations when the switch <NUM> is opened. In other examples, interlock mechanisms can prevent actuation of the direct break mechanism <NUM> if the switching device is open.

As can also be seen from <FIG>, a plane (shown side on, labelled as <NUM>) in which the disconnector blade <NUM> rotates is offset from this operating axis <NUM> of the respective switch by an offset, d. This offset allows a respective second actuating mechanism to be placed next to each switch <NUM> without interfering with actuation of the drive rod <NUM>.

In some implementations, each disconnector and earthing switch comprises two or more disconnector blades. By using two disconnector blades, two parallel paths are created for current flow. This can help to improve thermal performance. In other examples, each disconnector and earthing switch comprises a single disconnector blade. When there are two blades, the offset, d, also allows a compression spring to be connected to and placed between the two blades. The compression spring acts to pull both disconnector blades inward toward one another. When the disconnector blade moves to the on or earth position and engages with the on or earth contacts, then the two blades can move outward around the contacts, either due to the size/shape of the contacts or repulsive forces generated during e.g., short circuit tests. The compression spring is arranged to generate an inward force that will help counter repulsive forces and pull the blades together so they remain in good electrical connection with the one and earth contacts. Electrical contact may therefore be improved.

Moreover, the offset can facilitate a greater degree of movement of the disconnector blade of the disconnector and earthing switch, which facilitates improved clearance between the first, second and third positions of the disconnector blade illustrated in <FIG>.

For example, as shown in <FIG>, the offset allows the total degree of rotation of the disconnector blade of each switch <NUM> to be greater than <NUM> degrees. In some particular examples, theta_1 is between <NUM> and <NUM> degrees, optionally between <NUM> and <NUM> degrees, optionally between <NUM> and <NUM> degrees, optionally about <NUM> degrees. In some particular examples theta_2 is between <NUM> and <NUM> degrees, optionally between <NUM> and <NUM> degrees, optionally between <NUM> and <NUM> degrees, optionally about <NUM> degrees. In some particular examples, the clearance a between the first, "on", position and the second, "off" or isolation, position is between <NUM> and <NUM>, optionally between <NUM> and <NUM>, optionally between <NUM> and <NUM>, optionally about <NUM>. In some particular examples, the clearance b between the second, "off" or isolation, position and the third, earth, position is between <NUM> and <NUM>, optionally between <NUM> and <NUM>, optionally between <NUM> and <NUM>, optionally about <NUM>. However, it will be understood that the particular degrees of rotation theta_1, theta_2 and the particular clearances a, b will depend on the specific configuration and dimensions of the switchgear <NUM>, <NUM>.

Offsetting the plane of rotation of the disconnector blade <NUM> and the operating axis <NUM> thus facilitates use of a three-position disconnector and earthing switch <NUM> (or 3PS) within a compact switchgear <NUM>, <NUM>. A more compact, reliable switchgear may therefore be provided by use of the three-position disconnector and earthing switch 3PS provided herein.

With reference to <FIG>), one or more insulating or isolating features may be provided to improve electrical safety during the isolation, second, position. These features may be provided individually, or in combination with one or more other insulating features (including features not described herein). It will be understood that the second end <NUM> of the disconnector blade <NUM> can be shaped to accommodate the insulating/isolating features described in <FIG> whilst still allowing movement of the disconnector blade from the second position to the third, earthed, position of <FIG>.

In one example, shown in <FIG>, the second side wall 216a of the housing comprises an end insulator 600a. The end insulator is configured to contact, when the disconnector blades of the poles disposed proximate to the second side wall (e.g., the poles of the third switching device 208c) are in the second position, the second end <NUM> of said disconnector blades. In some examples, the end insulator (also called a support insulator as it supports the disconnector blade) comprises a copper portion which is in contact with the second end <NUM> of the disconnector blade <NUM>. This end/support insulator 600a reduces field end effects at the second end <NUM> of the disconnector blade <NUM> and provides a dielectrically better performance compared to a high electric field in air.

In one example, shown in <FIG>, the second side wall 216a of the housing comprises one or more shields 600b. In this example, there are two shields 600b, each shield comprising a metallic plate <NUM> covered in an insulating material <NUM>. When the disconnector blades <NUM> of the poles disposed proximate to the second side wall (e.g., the poles of the third switching device 208c) are in the second position, the second end <NUM> of said disconnector blades is disposed between the two shields 600b. This shield 600b reduces field end effects at the second end <NUM> of the disconnector blade <NUM>. Furthermore, the use of an insulating core means the high field is partly contained in the insulating material, which improves dielectric performance as compared to a high electric field in air.

In one example, shown in <FIG>, the second side wall 216a of the housing comprises an insulating sheet 600c. The insulating sheet 600c can be formed from any suitable insulating material. The insulating sheet 600c need not contact the second end <NUM> of the disconnector blades of the poles disposed proximate to the second side wall (e.g., the poles of the third switching device 208c) are in the second position. The presence of the insulating sheet 600c, even without physical contact, acts as an obstruction to breakdown electrical current paths and can help avoid dielectric failure, thereby improving dielectric performance as compared to an equivalent switchgear with no insulating sheet 600c.

The use of one or more insulating features on the second side wall 216b of the housing facilitates use of a three-position disconnector and earthing switch <NUM> within a compact switchgear <NUM>, <NUM>. A more compact, reliable switchgear may therefore be provided by use of the insulating features provided herein.

With reference to <FIG>), a busbar assembly <NUM> suitable for use with the switchgear <NUM>, <NUM> is described.

The busbar assembly <NUM> comprises a plurality of cylindrical main busbars <NUM>, each comprising an inner hole extending through a length of the main busbar. The busbar assembly also comprises a plurality of branch busbars <NUM>. A first end of each branch busbar comprises a hole <NUM> and a second end of each branch busbar comprises a spherical portion <NUM>. The use of a spherical (i.e., curved) portion at the second end of the branch busbar <NUM> acts to reduce or avoid high fields at the second end of the branch busbar. The second end of the disconnector blade contacts a corresponding branch busbar in the first, on, position to connect the power supply and the load.

A threaded rod <NUM> extends through the inner hole of each main busbar <NUM> and the hole <NUM> of each branch busbar <NUM>. The branch busbars <NUM> are configured to electrically connect to respective disconnector blades in the first, on, position. The threaded rod extends along a first direction <NUM> between a first end and a second end. The plurality of main busbars and the plurality of branch busbars are alternately arranged on the threaded rod along the first direction <NUM>. In some examples, each main busbar comprises an outer insulating sleeve <NUM> colinear with the inner hole.

With further reference to <FIG>, a switchgear <NUM>, <NUM> comprising the busbar assembly is described. As discussed above, the switchgear comprises a housing comprising first 216a and second 216b side walls offset along the first direction <NUM>. The first side wall 216a comprises a first insulating mount <NUM> configured to threadably engage with the first end of the threaded rod <NUM>. The second side wall 216b comprises a second insulating mount <NUM> configured to threadably engage with the second end of the threaded rod <NUM>. In some examples, the first insulating mount <NUM> is an insulating bush. In some examples, the second insulating mount <NUM> is an epoxy insulator. However, other insulating mounts may be used, as required by the size and use/application of the switchgear.

With reference to <FIG>, a plan view of a switchgear <NUM>, <NUM> in accordance with the current disclosure and comprising a busbar assembly <NUM> is described. The example of <FIG> is a three-way switchgear having three switching devices <NUM>: a first switching device 208a, a second switching device 208b, and a third switching device 208c. The switching devices are provided between first 216a and second 216b side walls of the switchgear housing, arranged along a first axis <NUM>.

In this particular example, a distance d1 between the first and second switching devices 208a, 208b is equal to a distance between the second and third switching devices 208b, 208c. However, to provide a compact footprint, a distance d2 between the third switching device and the second side wall 216b of the housing is less than d1. Moreover, a distance d3 between the first switching device and the first side wall 216a of the housing is less than d1 and less than d2. The dimension d2 is limited by the need to provide sufficient insulation/isolation during the second, "off" position of the 3PS disconnector and earthing switch <NUM>. The insulating feature(s) described with reference to <FIG> facilitate a smaller dimension d2, which helps provide a more compact switchgear.

In accordance with the above disclosure, each of the first, second and third switching devices comprise three poles 210a, 210b, 210c arranged in a depth-wise or transverse direction <NUM> (as in <FIG>). In other words, the switching devices <NUM> are arranged along a first axis (<NUM>), and the plurality of poles <NUM> of each switching device are arranged along a respective second axis (<NUM>) perpendicular to the first axis. Each of the plurality of poles <NUM> is associated with a respective switch <NUM> having a fixed contact and a moveable contact. Each of the plurality of poles <NUM> is also associated with an disconnector and earthing switch <NUM>, as discussed with reference to <FIG>.

A plurality of busbar assemblies <NUM> as described with reference to <FIG> are arranged between the operating shaft <NUM> (not shown) and the switches <NUM>. The busbar assemblies <NUM> are insulated at each end and coupled to the housing of the switchgear, as described with reference to <FIG>. Each busbar assembly comprises a plurality of main busbars <NUM> and a plurality of branch busbars <NUM> alternately arranged along the first axis <NUM>.

In this example, each busbar assembly <NUM> comprises two main busbars <NUM>, each main busbar extending parallel to the first axis to electrically connect corresponding poles <NUM> of adjacent switching devices <NUM>. For example, one main busbar connects pole 210a of switch/device 208a and pole 210a of switch/device 208b and another main busbar connects pole 210a of switch/device 208b and pole 210a of switch/device 208c. However, there may be one more than two main busbars per assembly.

Claim 1:
A switchgear (<NUM>, <NUM>), comprising:
a plurality of switching devices (<NUM>) configured to disconnect a power supply from a load, each switching device comprising:
a plurality of poles (<NUM>), each pole associated with a respective switch (<NUM>) having a fixed contact and a moveable contact, and
an actuating mechanism comprising a shaft (<NUM>), the shaft configured to rotate to transfer an external input force to move the moveable contact and open or close the switches of the switching device;
wherein:
the plurality of switching devices are arranged along a first axis (<NUM>),
the plurality of poles of each switching device are arranged along a respective second axis (<NUM>) perpendicular to the first axis, and
each shaft is arranged perpendicular to the first axis and is configured to rotate around a rotational axis parallel to the second axes; and
a plurality of disconnector and earthing switches (<NUM>), each disconnector and earthing switch associated with a respective one of the plurality of poles, and each disconnector and earthing switch having a disconnector blade (<NUM>) pivotable around a first end (<NUM>) of the disconnector blade between three different positions, the three positions comprising:
a first position in which the disconnector and earthing switch is closed and the power supply is connected to the load through the disconnector blade;
a second, isolation, position in which the disconnector and earthing switch is open and the power supply is disconnected from the load; and
a third position in which the power supply is disconnected from the load and a second end (<NUM>) of the disconnector blade is electrically connected to an
earthing contact (<NUM>), characterised in that the first end of the disconnector blade is pivotably coupled to the respective switch.