Isolating switch for electric railway or tramway

Abstract

An isolating or disconnection switch 1 for mounting on a conducting rail 5 or overhead wire system of a railway or tramway comprises an electrical actuator 6 arranged to close and open contacts 7a, 7b

Description

Technical Field

[0001] The present invention relates to a disconnection or isolation switch for use in electric railways, tramways and the like. Background

[0002] Electric railways, tramways and the like are supplied with power either by overhead wires or using conductor rails in a three or four rail system. In both cases it is often necessary to isolate portions of the wires or rails from the electrical supply to allow maintenance or other work to be carried out safely.

[0003] Isolation can be provided by switchgear enclosed in a cabinet sited adjacent to the track. Examples of such switchgear are manufactured by L.C. Switchgear and include their SD - LCS2 (TIS) single pole supply disconnector. Often a supply disconnector is combined with a switch to bond the supply rail to the negative pole of the supply in order to guard against inadvertent re-energisation. Such a piece of switchgear occupies a relatively large space and in some situations, such as in a tunnel, there is not enough room to site a cabinet near to the track. In other cases, it may be difficult to provide the cabinet with the electrical services needed to operate the switchgear and associated equipment.

[0004] In these circumstances a manually operated switch is conventionally employed to provide isolation between the supply and the third rail. One type of manually operated switch is known as a hook switch, which derives its name from the pole with a hook on the end used to operate the switch. A hook switch for a three or four rail system typically comprises a casting that carries current to the rail and is bolted directly to the flange of the rail. Mounted on the casting, but isolated from it, is a pivot for a switch blade. Mounted directly onto the casting is a contact jaw with which the switch blade makes contact. The switch is provided with clamps at the pivot for the switch blade and the contact jaw; these are to prevent the vibrations from passing rolling stock opening or closing the switch. To clamp or unclamp the switch blade the operator must use the hook to strike the clamp with considerable force.

[0005] The hook switch is only suitable for opening and closing under no load conditions and the operator must check that there is no current flowing through the switch before attempting to open or close it. Failure to do so can result in large, dangerous arcing at the switch contacts. Even if there is no current flowing, the manual operation of the hook switch requires the operator to be close to the supply rail which he or she is isolating in order to gain safe access to the portion of rail associated with the switch.

[0006] In wet weather the pole with the hook may not provide adequate insulation for the operator. Although the switch is not intended to be operated unless the power supply has already been isolated elsewhere it is possible to operate the prior art switch with power on or even when passing current. Whilst doing so it is possible for the hook to bridge the contact gap or short the live parts to ground. Statements of the Invention

[0007] Aspects of the invention are defined in the accompanying claims.

[0008] In at least some embodiments of the invention, an isolating or disconnection switch for mounting directly or indirectly on a conducting rail or overhead wire system of a railway or tramway comprises an electrical actuator arranged to close and open contacts to respectively connect and disconnect an electrical supply from the conducting rail or overhead wire system.

[0009] The switch may have a linear moving contact that moves linearly into contact with a fixed contact. The moving contact may be a bridging contact that makes contact in a closed position between two fixed contacts. The actuator may be a linear actuator or a rotary actuator.

[0010] The electrical actuator may be inhibited if a power supply cable connected to the switch is energised. In particular, the electrical actuator may be inhibited from opening the switch if current is flowing through the switch. Hence, arcing when opening or closing the switch may be prevented.

[0011] The switch may include an insulating housing or cover which insulates electrically conductive parts from the operator. The housing or cover may prevent ingress of dirt or water into the switch. The switch may include an indicator to show whether the switch is open or closed.

[0012] The electrical actuator may be operated by a remote controller. The remote controller may be connected to the switch by a low voltage cable. Alternatively, the remote controller may be wirelessly connected to the switch. In either case, the operator may operate the switch from a safe distance using the remote controller.

[0013] The remote controller may be configured only to operate certain switches, so as to prevent unauthorised operation of other switches.

[0014] The switch may include, or be connected to an electrical power supply such as a low voltage supply or a battery, to provide power to the actuator. In the case of a wired remote controller, the power supply may be provided by the remote controller through the low voltage cable.

[0015] The feature of a remote control that may be removably or wirelessly connected to an isolating or disconnection switch is considered to be independently inventive. Hence, according to another aspect of the present invention there is provided an isolating or disconnection switch for comprises an electrical actuator arranged to close and open contacts to respectively connect and disconnect an electrical supply from the conducting rail or overhead wire system of an electrical railway or tramway, wherein the electrical actuator is operable by a remote controller removably or wirelessly connected to the switch. Brief Description of the Drawings

[0016] Specific embodiments will now be described with reference to the accompanying drawings, as listed below. Fig. 1 is a plan view of a switch in an embodiment of the invention, mounted on a rail. Figs. 2a and 2b are first perspective views of the switch with its cover removed, connected between a power cable and a rail, respectively in closed and open positions. Figs. 3a and 3b are second perspective views of the switch with its cover removed, respectively in closed and open positions. Detailed Description of Embodiments

[0017] The Figures show an isolating or disconnecting switch 1 in an embodiment of the invention, electrically connected between a conductor rail 5, of the type used in an electric railway ortramway track, and a power supply cable or cables 2 for supplying power to the rail 5, typically at high current (e.g. 2-4.4 kA) and a DC voltage of 750 V. The switch 1 is operable selectively to connect and disconnect the power supply to the rail 5. The switch 1 may be opened so as to isolate a part of the track, for example for maintenance or in an emergency.

[0018] The switch 1 is mounted on the conductor rail 5 by a first mounting bracket 3 electrically connected to the rail 5, and a second mounting bracket 4 electrically insulated from the rail 5. The mounting brackets 3, 4 may be bolted or clamped to the rail 5. Alternatively, the mounting brackets 3, 4 may be indirectly mounted on the rail 5, for example via one or more adapters designed to allow the switch 1 to be arranged in an alternative position with respect to the rail 5, for example to avoid a local obstruction.

[0019] The switch 1 may have a removable cover 10 as shown in Fig.l; the cover 10 is removed in the other Figures. The cover 10 provides electrical insulation of the internal components of the switch 1 from the operator. In the configuration shown in Fig.l, an electrical connection 2a between the cable(s) 2 and the switch 1 extends beyond the cover 10. In an improved arrangement, the cover 10 extends over or beyond the electrical connection 2a so that no uninsulated parts are accessible to the operator. Preferably, the cover 10 prevents or at least reduces ingress of dirt and / or water into the internal parts of the switch 1.

[0020] In the embodiment shown in Figures 2a-b and 3a-b, the switch 1 comprises: a first fixed contact assembly 7a connected to the first mounting bracket 3 which is electrically connected to the rail 5, a second fixed contact assembly 7b attached to the second mounting bracket 4 which is electrically insulated from the rail 5, the second fixed contact assembly 7b being electrically connected to the power supply cable(s) 2; a bridging contact assembly 8 for providing a bridging contact between the first and second fixed contact assemblies 7a, 7b when in a closed position, the bridging contact assembly 8 being moveable linearly (e.g. slideable) between the closed position and an open position in which no bridging contact is provided; and an electrical actuator 6 connected to the bridging contact assembly 8 (in this case, by a pair of connecting rods 9) so as to move the bridging contact assembly 8 between the closed and open positions.

[0021] In the embodiment shown, the electrical actuator 6 is mounted on a base 14 connected to the first and second contact assemblies 7a, 7b. The cover 10 may be mounted on the base 14.

[0022] In this embodiment, the first and second contact assemblies 7a, 7b comprise a plurality of parallel electrically conductive fixed contact plates, and the bridging contact assembly 8 comprises a plurality of parallel electrically conductive bridging contact plates which slide between the fixed contact plates. Contact springs mounted on the bridging contact plates may be arranged to make electrical contact with the fixed contact plates. Alternatively, contact springs may be mounted on the fixed contact plates and arranged to make electrical contact with the bridging contact plates. This arrangement provides a large contact surface of low electrical resistance, such that the switch is suitable for high current applications.

[0023] Advantageously, the bridging contact assembly 8 moves in a direction substantially parallel to the rail 5, unlike the rotational motion of the prior art manual switch, so that the switch 1 comprises a compact elongate unit that can be mounted parallel to the rail 5, and can therefore be used in confined spaces. Moreover, the unit can be mounted so as not to project above the rail 5 and therefore may avoid causing an obstruction.

[0024] An arrow or other indicator 15 can be fixed to a convenient moving part of the switch 1, in this case the connecting rod 9. The indicator 15 is visible through a transparent portion of the cover 10, giving a visual indication of the switch condition, either open or closed. Alternatively or additionally, an audible or other type of indication may be provided.

[0025] The actuator 6 may be a linear actuator arranged to move the connecting rods 9 reciprocally in response to a control signal, so as to selectively open and close the switch 1. Alternatively, the actuator 6 may be a rotating actuator. The actuator 6 may comprise an electric motor.

[0026] The control signal may be provided by a remote controller 12, shown schematically in Fig. 1, which may be removably connectable to the linear actuator 6 by means of a remote control connector on or accessible through the cover 10. The remote controller 12 may include a cable 13 for connection to the remote control. The remote controller 12 may include a power source, such as a battery, which provides electrical power to the actuator 6 and which may be recharged without the operator needing to access the switch 1. Alternatively, the battery may be integrated with the switch, and provided within the cover 10. Alternatively, there may be a low power mains connection to the actuator 6.

[0027] Alternatively, the remote controller 12 may be wirelessly connected to the switch 1 so as to control the actuator 6 by means of wireless control signals. The wireless connection may be a wireless peer-to-peer connection, such as Bluetooth (RTM).

[0028] In either the wired or wireless cases, the remote controller 12 may allow the operator to operate the switch 1 from a safe distance with reduced risk of electrocution and / or from arcing. The remote controller 12 may include an indicator for indicating whether the switch is open or closed, so that the operator does not need to check this in the vicinity of the power rail 5.

[0029] The switch 1 may be configured so as to be only controllable by a suitably configured remote controller 12. For example, the remote controller 12 may be configured to send an authentication code to the switch 1, which may only be operable by the remote controller 12 if the authentication code is recognised. Alternatively, in the case of a wired remote controller 12, the cable connection to the switch may be by means of a proprietary connector only able to receive a correctly configured connector on the cable. In this way, access to the switch 1 may be restricted, and the remote controller 12 may be configured so as to operate only certain switches, for example in an authorised area of track.

[0030] The switch 1 may include one or more sensors arranged to indicate the status of the switch 1 to the remote controller 12, for example whether the switch 1 is connected to the electrical supply or passing current. The remote controller 12 and / or the actuator 6 may be configured not to open or close the switch 1 when the sensor(s) indicate that power is supplied to the switch 1 and / or the switch is passing current.

[0031] The above-described embodiment is arranged for mounting on a live rail, for example in a three or four rail system. In an alternative embodiment, the switch 1 may be mounted directly or indirectly on an overhead power cable or wire, or wire / cable termination, in an electric railway or tramway, and may be arranged to disconnect or isolate the overhead power cable from the power supply.

[0032] Alternative embodiments, which may become apparent to the skilled person on reading the above description, may nevertheless fall within the scope of the invention as defined by the following claims. 26 03 24

Claims

1. An isolating or disconnection switch for mounting directly or indirectly on, or mounted directly or indirectly on, a conducting rail or overhead wire of a railway or tramway, and for connection to, or connected to, one or more power cables for supplying power to the conducting rail or overhead wire, the switch including a linear moving contact and an electrical actuator arranged to move the linear moving contact linearly so as to close and open the switch so as respectively to connect and disconnect the supply of power to the conducting rail or overhead wire.

2. The switch of claim 1, comprising first and second fixed contacts electrically connected or connectable respectively to the rail or overhead wire and to the one or more power cables.

3. The switch of claim 2, including first and second mounting brackets each mounted or mountable, directly or indirectly, to the conducting rail or overhead wire, wherein the first fixed contact is electrically connected or connectable to the first mounting bracket and the second fixed contact is electrically connected or connectable to the second mounting bracket.

4. The switch of claim 2 or claim 3, wherein the linear moving contact comprises a bridging contact that makes contact in a closed position between the first and second fixed contacts.

5. The switch of claim 4, wherein each of the first and second fixed contacts comprises a plurality of parallel electrically conductive fixed contact plates, and the bridging contact assembly comprises a plurality of parallel electrically conductive bridging contact plates arranged to slide between the first and second fixed contacts.

6. The switch of any preceding claim, wherein the electrical actuator comprises a linear actuator connected to move the bridging contact assembly reciprocally.

7. The switch of any preceding claim, for mounting directly or indirectly on, or mounted directly or indirectly on, a conducting rail of a railway such that the bridging contact assembly moves linearly in a direction substantially parallel to the conducting rail.

8. The switch of any preceding claim, having a remote controller for controlling the electrical actuator so as to close and open the switch.

9. The switch of claim 8, wherein the remote controller is removably connected or connectable to the switch by a cable.

10. The switch of claim 9, wherein the remote controller includes a power supply arranged to supply power to the electrical actuator via the cable.26 03 2411. The switch of claim 8, wherein the remote controller is wirelessly connected or connectable to the switch.

12. The switch of any one of claims 1 to 9 or claim 11, including a power supply for supplying power to the electrical actuator.

13. The switch of claim 10 or claim 12, wherein the power supply comprises a battery.

14. The switch of claim 8, or any one of claims 9 to 13, arranged to prevent unauthorised operation by the remote controller.

15. The switch of any preceding claim, arranged to prevent operation of the switch when power is supplied to the switch and / or when current is flowing through the switch.

16. The switch of any preceding claim, including a removable cover or housing arranged to insulate electrically conductive parts of the switch from the operator and / or to prevent ingress of dirt and / or water into the switch.

17. The switch of any preceding claim, including an indicator arranged to indicate whether the switch is open or closed.

18. The switch of claim 17 when dependent directly or indirectly on claim 8, wherein the indicator is provided in the remote controller.

19. The switch of any preceding claim, comprising an elongate unit arranged to be mounted, or mounted extending parallel to the conducting rail or overhead wire.

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