Apparatus and method for use in a power delivery system

Abstract

An apparatus for use in an electric power delivery system, the apparatus comprising: a DC circuit breaker having a first terminal and a second terminal and configured to automatically switch from a closed state to an open state during an overcurrent condition; a disconnector in series with the DC circuit breaker, the disconnector having a first terminal for connection with a first polarity terminal of a DC power source, a second terminal for connection with a second polarity terminal of the DC power source, and a common terminal connected with the first terminal of the DC circuit breaker, the disconnector having at least a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and an interlock mechanism coupled with the DC circuit breaker and the disconnector, the interlock mechanism configured to disable the DC circuit breaker to prevent automatically switching from the closed state to the open state during the overcurrent condition when the disconnector is in the second position.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a direct current (DC) circuit breaker for use in a power delivery system, and in particular to an apparatus and associated method for disabling a DC circuit breaker to prevent automatic opening in response to overcurrent when the power delivery system is grounded for maintenance. BACKGROUND

[0002] DC power delivery systems are widely used, for example for delivering power to a conductive rail of a transportation system. Examples include railway and tramway infrastructure in which DC current is supplied to a live (e.g. positive voltage) conductive rail, such as a live third rail or live overhead cable. Such power delivery systems require automatic circuit breaker protection to quickly and automatically disconnect the live conductive rail from the power supply in the event of an overcurrent condition. This overcurrent can be caused by many types of event, such as damage to the cable support structure, displacement of the cable or rail, accidental short circuit of the live conductive rail to ground or an overload condition in a load device using the power delivery system.

[0003] Power delivery systems also require a mechanism for placing the conductive rail in a safe (e.g. grounded) maintenance condition when personnel need to work on the infrastructure. In this way, when the live conductive rail is taken out of service, any inadvertent connection of the conductive rail to the power supply or a lightning strike on the conductive rail somewhere in the network does not cause damage to other parts of the infrastructure or harm to personnel working on the infrastructure.

[0004] In existing infrastructure, one way of providing a safe maintenance condition for the conductive rail is to manually attach a shorting bar or clamp between the conductive rail and a negative voltage return rail or a grounded rail (sometimes referred to as "rail bonding"). To improve efficiency and safety, a further method of bonding the rail has recently been developed which involves the use of a locally or remotely controlled switch. However, under certain installation arrangements, negative return current can be possible to flow in the positive direction through the power delivery system. This potentially trips the DC circuit breaker in the bonding configuration and leaves the conductive rail live and unsafe.

[0005] The listing or discussion of a previously published document or any background in the specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects / embodiments of the present disclosure can address one or more of the problems in the background. SUMMARY

[0006] According to a first aspect, there is provided an apparatus for use in a power delivery system, the apparatus comprising:

[0007] A DC circuit breaker having a first terminal and a second terminal and configured to automatically switch from a closed state to an open state during an overcurrent condition;

[0008] A disconnector in series with the DC circuit breaker, the disconnector having a first terminal for connection with a first polarity terminal of the DC power source, a second terminal for connection with a second polarity terminal of the DC power source, and a common terminal connected with the first terminal of the DC circuit breaker, the disconnector having at least a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and

[0009] An interlock mechanism coupled with the DC circuit breaker and the disconnector, the interlock mechanism configured to disable the DC circuit breaker to prevent the automatic switching from the closed state to the open state during the overcurrent condition when the disconnector is in the second position.

[0010] The DC circuit breaker can include first and second contacts corresponding to the first and second terminals. The first and second contacts can be located on first and second contact arms of the DC circuit breaker, respectively, and at least one of the first and second contact arms can be movable.

[0011] The DC circuit breaker can include a trip device configured to cause movement of the at least one movable contact arm during the overcurrent condition, and the interlock mechanism can be coupled to the trip device and configured to disable the DC circuit breaker by inhibiting operation of the trip device.

[0012] The trip device can include an electromagnetic actuator having an armature mechanically coupled with the at least one movable contact arm. The electromagnetic actuator can be configured to generate a magnetic flux in response to the overcurrent causing movement of the armature and a corresponding movement of the at least one movable contact arm.

[0013] The interlock mechanism can be configured to inhibit operation of the trip device by inhibiting movement of the armature.

[0014] The armature can be mechanically coupled to the at least one movable contact arm by a latch, and the interlock mechanism can be configured to inhibit operation of the trip device by inhibiting movement of the latch.

[0015] The electromagnetic actuator can include a primary armature mechanically coupled with the at least one movable contact arm such that the magnetic flux causes movement of the primary armature and a corresponding movement of the at least one movable contact arm, and a secondary armature configured to move when the magnetic flux exceeds a predetermined magnitude. The movement of the secondary armature can decrease a magnetic reluctance of the electromagnetic actuator triggering movement of the primary armature, and the interlock mechanism can be configured to inhibit operation of the trip device by inhibiting movement of the primary armature or the secondary armature.

[0016] The interlock mechanism can be coupled to at least one movable contact arm of the DC circuit breaker and can be configured to disable the DC circuit breaker by inhibiting movement of the at least one movable contact arm.

[0017] The interlock mechanism can include a mechanical or electromechanical assembly including a blocking component configured to contact and physically constrain the at least one movable contact arm, armature, or latch when the disconnector is in the second position so as to inhibit said movement.

[0018] The interlock mechanism can be configured to inhibit operation of the trip device by diverting magnetic flux generated by the electromagnetic actuator and thereby inhibiting movement of the armature.

[0019] The interlock mechanism can include a soft magnetic material configured to attract magnetic flux away from the armature when the disconnector is in the second position so as to inhibit said movement.

[0020] The trip device can be a direct-acting trip device or an indirect-acting trip device.

[0021] The direct-acting trip device can include an electromagnetic actuator. The indirect-acting trip device can include one or more of a protective relay and a transducer.

[0022] The interlock mechanism can be configured to enable the DC circuit breaker to automatically switch from a closed state to an open state during an overcurrent condition when the disconnector is in the first position.

[0023] The DC circuit breaker can be a unidirectional circuit breaker configured to automatically switch from a closed state to an open state during an overcurrent condition in a forward direction and remain in a closed state independent of current level in a reverse direction.

[0024] The DC circuit breaker can be a bidirectional circuit breaker configured to automatically switch from a closed state to an open state during an overcurrent condition in a forward direction and a reverse direction.

[0025] The forward direction can correspond to current flowing from a first terminal to a second terminal of the DC circuit breaker, and the reverse direction can correspond to current flowing from the second terminal to the first terminal of the DC circuit breaker.

[0026] The disconnector can be interlocked to prevent switching between the first position and the second position when the DC circuit breaker is in the closed state.

[0027] The disconnector can have a third position in which both the first terminal and the second terminal are electrically isolated from the common terminal.

[0028] The disconnector can comprise a visual position indicator indicating its state in the first or second position (or third position).

[0029] The second terminal of the DC circuit breaker can be coupled to a first conductive rail of the power delivery system.

[0030] The first polarity connector of the DC power source can be coupled to a third rail or overhead cable of the transportation system, and the second polarity connector of the DC power source can be coupled to a rail of the transportation system.

[0031] The disconnector can comprise:

[0032] at least one movable contact arm in electrical connection with the common terminal; and

[0033] a shutter mechanism configured to at least incompletely obstruct a first gap between the at least one movable contact arm and the first terminal when the disconnector is in the second position, and to at least incompletely obstruct a second gap between the at least one movable contact arm and the second terminal when the disconnector is in the first position.

[0034] The at least one movable contact arm can comprise a single contact arm configured to perform a pivotal or translational movement between a first position in contact with the first terminal and a second position in contact with the second terminal. The shutter mechanism can comprise a first shutter and a second shutter. The first shutter can be configured to open and close a passage between the single contact arm and the first terminal such that the first shutter is open when the single contact arm is in the first position and closed when the single contact arm is in the second position, and the second shutter can be configured to open and close a passage between the single contact arm and the second terminal such that the second shutter is open when the single contact arm is in the second position and closed when the single contact arm is in the first position.

[0035] The at least one movable contact arm can include first and second reciprocating arms each in electrical connection with a common terminal. The first reciprocating arm can be movable between a non-contact position isolated from the first terminal and a contact position in contact with the first terminal, and the second reciprocating arm can be movable between a non-contact position isolated from the second terminal and a contact position in contact with the second terminal. The shutter mechanism can include first and second shutters. The first shutter can be configured to open and close a passageway between the first reciprocating arm and the first terminal such that the first shutter is open when the first reciprocating arm is in the contact position and the second reciprocating arm is in the non-contact position and closed when the first reciprocating arm is in the non-contact position and the second reciprocating arm is in the contact position. The second shutter can be configured to open and close a passageway between the second reciprocating arm and the second terminal such that the second shutter is open when the second reciprocating arm is in the contact position and the first reciprocating arm is in the non-contact position and closed when the second reciprocating arm is in the non-contact position and the first reciprocating arm is in the contact position.

[0036] The first and second reciprocating arms can be connected to each other via a seesaw mechanism and driven by a common motor such that the first reciprocating arm moves from the non-contact position to the contact position while the second reciprocating arm moves from the contact position to the non-contact position, and vice versa.

[0037] The first and second reciprocating arms can be driven by respective motors such that the first reciprocating arm moves from the non-contact position to the contact position only once the second reciprocating arm has moved from the contact position to the non-contact position, and the second reciprocating arm moves from the non-contact position to the contact position only once the first reciprocating arm has moved from the contact position to the non-contact position.

[0038] The first and second shutters can each include at least one door biased to close a passageway between the at least one movable contact arm and the respective terminal, and the at least one movable contact arm can include an opening member configured to force the at least one door open against the bias when the at least one movable contact arm moves toward the respective terminal.

[0039] The at least one door can include one or more hinged doors biased by a spring or gravity to close the passageway, and the opening member of the at least one movable contact arm can be configured to push the one or more hinged doors open against the spring or gravity bias when the at least one movable contact arm moves toward the respective terminal.

[0040] The at least one door can include a pair of doors that come together to close the passageway. Each door can have a protruding member configured to engage an opening member of the at least one movable contact arm, and the opening member is shaped to be wedge shaped to force the doors open against the bias when the at least one movable contact arm is moved toward the respective terminal.

[0041] The at least one movable contact arm of the DC circuit breaker and the disconnector can be housed within an arc containment enclosure, and the first terminal and the second terminal of the disconnector can be located outside of the arc containment enclosure. The switch mechanism can be configured to open and close a respective passageway outside of the arc containment enclosure through which the at least one movable contact arm must travel to contact the first terminal and the second terminal.

[0042] The first terminal and the second terminal of the disconnector can be separated from each other by an insulating barrier.

[0043] The DC circuit breaker and the disconnector can be formed on a common detachable unit of the power delivery system.

[0044] The common detachable unit can be mounted on wheels to facilitate detachment from and reattachment to the power delivery system.

[0045] The common detachable unit can further include one or more of a shunt, a fuse, and a transducer of the power delivery system.

[0046] According to a second aspect, there is provided a method of configuring a power delivery system, the method comprising:

[0047] connecting a disconnector to a DC power source such that a first terminal of the disconnector is connected to a first polarity terminal of the DC power source and a second terminal of the disconnector is connected to a second polarity terminal of the DC power source, the disconnector having at least a first position in which the first terminal is connected to a common terminal of the disconnector and a second position in which the second terminal is connected to the common terminal of the disconnector;

[0048] connecting the common terminal of the disconnector to a first terminal of a DC circuit breaker, the DC circuit breaker having the first terminal and a second terminal and being configured to automatically switch from a closed state to an open state during an overcurrent condition;

[0049] coupling an interlock mechanism to the DC circuit breaker and the disconnector such that the interlock mechanism is able to disable the DC circuit breaker to prevent the automatic switch from the closed state to the open state during the overcurrent condition when the disconnector is in the second position;

[0050] connecting the second terminal of the DC circuit breaker to a first power line; and

[0051] connecting the second terminal of the disconnector and the second polarity terminal of the DC power source to the second power line.

[0052] The method can further comprise placing the first and second power lines in a working condition by switching the disconnector to the first position and then setting the DC circuit breaker to a closed configuration.

[0053] The method can further comprise placing the first and second power lines in a safe maintenance condition by switching the DC circuit breaker to an open condition, then switching the disconnector to the second position, and then switching the DC circuit breaker to a closed condition.

[0054] The first power line can be a live (e.g. positive) conductor rail of a railway or tramway infrastructure, and the second power line can be a return (e.g. negative) conductor rail of the railway or tramway infrastructure.

[0055] According to a third aspect, there is provided a transfer switch comprising:

[0056] a first terminal, a second terminal, and a common terminal;

[0057] at least one movable contact arm electrically connected to the common terminal and movable between a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and

[0058] a shutter mechanism configured to at least incompletely obstruct a first gap between the at least one movable contact arm and the first terminal when the transfer switch is in the second position and to at least incompletely obstruct a second gap between the at least one movable contact arm and the second terminal when the transfer switch is in the first position.

[0059] The transfer switch can be a disconnector for use in a power delivery system, the first terminal can be connected to a first polarity terminal of a DC power source, and the second terminal can be connected to a second polarity terminal of the DC power source.

[0060] According to a fourth aspect, there is provided a method of configuring a transfer switch, the method comprising:

[0061] providing a first terminal, a second terminal, and a common terminal;

[0062] electrically connecting at least one movable contact arm to the common terminal such that it is movable between a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and

[0063] A shutter mechanism is provided that is configured to at least partially obstruct a first gap between the at least one movable contact arm and the first terminal when the transfer switch is in the second position, and to at least partially obstruct a second gap between the at least one movable contact arm and the second terminal when the transfer switch is in the first position.

[0064] The method can further comprise using the shutter mechanism to move the at least one movable contact arm to the first position while obstructing the second gap, or using the shutter mechanism to move the at least one movable contact arm to the second position while obstructing the first gap.

[0065] According to a fifth aspect, there is provided an apparatus as substantially described herein with reference to the accompanying drawings and as shown in the accompanying drawings.

[0066] Optional features described in relation to the isolating switch of the first aspect can also be applicable to the transfer switch of the compatible third aspect.

[0067] The steps of any method disclosed herein do not have to be carried out in the precise order disclosed, unless explicitly stated or understood otherwise by a person skilled in the art.

[0068] A corresponding computer program for implementing one or more of the methods disclosed herein, which computer program may or may not be recorded on a carrier, is also within the present disclosure and covered by one or more of the described example embodiments.

[0069] The present disclosure includes one or more corresponding aspects, example embodiments, or features individually or in various combinations whether or not specifically stated in this combination or individually, including as claimed. A corresponding device for performing one or more of the discussed functions is also within the present disclosure.

[0070] Throughout this specification, descriptors relating to position, orientation or movement, such as "left", "right", "up", "down", "horizontal" and "vertical", and any adjectival and adverbial derivatives of the same, are used in their sense of relative position, orientation or movement as presented in the figures. However, such descriptors are not intended to be limiting in any way to the intended use of the invention described or claimed.

[0071] The above summary is intended to be merely an illustrative and not a limiting. BRIEF DESCRIPTION OF DRAWINGS

[0072] The description will now be presented in relation to the accompanying drawings, by way of example only, and with reference to the following illustrations:

[0073] Figure 1 a to Figure 1 d illustrates different states of the circuit for rail conduction;

[0074] Figure 2a A fault current is shown flowing through the electrical circuit in a feeder configuration;

[0075] Figure 2b A fault current is shown flowing through the electrical circuit in a conductor-on configuration;

[0076] Figure 3 A fault current is shown flowing from an adjacent track through a track parallel room to a neighboring substation;

[0077] Figure 4a A device is shown including an interlock mechanism to resolve Figure 3 the scenario shown in the device;

[0078] Figure 4b A device is shown in Figure 4a where the interlock mechanism is in a locked state;

[0079] Figure 5 A trip device of a DC circuit breaker is shown in a tripped state;

[0080] Figure 6a More details of the interlock mechanism in Figure 4a are shown;

[0081] Figure 6b More details of the interlock mechanism in Figure 4b are shown;

[0082] Figure 7 Another device is shown including an interlock mechanism to resolve Figure 3 the scenario shown in the device;

[0083] Figure 8a A disconnector / transfer switch is shown including a single movable contact arm configured to perform a pivoting motion;

[0084] Figure 8b A disconnector / transfer switch is shown including a single movable contact arm configured to perform a translational motion;

[0085] Figure 9 Another disconnector / transfer switch is shown including first and second movable contact arms and respective shutters;

[0086] Figure 10 A device is shown including Figure 9 a disconnector / transfer switch with additional opening means for opening the respective shutters;

[0087] Figure 11An insulating barrier for isolating a first terminal and a second terminal of a disconnector / transfer switch is shown;

[0088] Figure 12 A disconnector / transfer switch is shown Figure 9 having a visual position indicator, a fuse, and a transducer; and

[0089] Figure 13 A withdrawable trolley is shown having a DC circuit breaker and a disconnector / transfer switch that is decoupled from a cabinet of a power delivery system. DETAILED DESCRIPTION

[0090] Figure 1 A schematic diagram of a power delivery system for delivering power to a conductive rail of a railway infrastructure is shown. A DC power source 1 has a positive output terminal 2 and a negative output terminal 3. The DC power source 1 can be a rectifier that receives an alternating current (AC) input. The positive output terminal 2 is connected to a busbar 4 via a circuit breaker 5. The busbar 4 is connected to a disconnector 10 that is connected to a unidirectional circuit breaker 20. The negative output terminal 3 of the power source 1 is connected to a negative return conductive rail 6 of the railway infrastructure. The circuit breaker 20 is connected to a positive conductive rail 7 of the railway infrastructure.

[0091] In one configuration, the positive conductive rail 7 can be an overhead cable or catenary suitable for current collection by a pantograph. In another configuration, the positive conductive rail can be a live third rail, such as a rigid conductor placed alongside or between tracks of a railway track. The negative return conductive rail 6 can be a railway track or a tram track.

[0092] The disconnector 10 has a first terminal 11 that is electrically connected to the busbar 4 and thereby to the positive output terminal 2 of the power source 1. The disconnector 10 has a second terminal 12 that is electrically connected to the negative output terminal 3 of the power source 1 and to the negative return conductive rail 6. The disconnector 10 has a third terminal that can be described as a common terminal 13 that is connected to a first terminal 21 of the unidirectional circuit breaker 20. The disconnector 10 has a first position in which its first terminal 11 is electrically connected to the common terminal 13 and a second position in which its second terminal 12 is connected to the common terminal 13, such as a single pole, two position configuration.

[0093] The circuit breaker 20 has a first terminal 21 and a second terminal 22 and is unidirectional in the sense that it is configured to automatically open the contacts of the circuit breaker upon detection of an overcurrent condition in the first (positive) direction, in this case for current flow from the first terminal 21 to the second terminal 22, and does not automatically open the contacts of the circuit breaker upon current flow or overcurrent flow in the reverse direction, i.e. current flow from the second terminal 22 to the first terminal 21. The circuit breaker 20 can be configured to trip in the positive direction at any suitable current level deemed to be an overcurrent condition.

[0094] The busbar 4 can feed other disconnector and circuit breaker equipment not shown in the figures, for example those configured to feed other sections of the conductive rails 6, 7 of the railway infrastructure.

[0095] In use, the power delivery system will be in a normal service ("feed") configuration, as shown in Figure 1 a, in which power is delivered from the power source 1 to the rails 6 and 7 by the closed (as labelled) circuit breaker 5, the disconnector 10 in the first position (terminals 11 and 13 connected) as shown, and the closed (as labelled) circuit breaker 20.

[0096] In order to bring the power delivery system into a safe ("conduct") configuration for maintenance, not only must the connection between the busbar 4 and the positive conductive rail 7 be broken, but the positive rail 6 and the negative rail 7 must also be shorted together.

[0097] In a first step, as shown in Figure 1 b, the circuit breaker 20 is set to an open condition, for example by deliberately tripping the circuit breaker using a manual override or an electronic trip, or by an actual overcurrent fault condition that causes the circuit breaker to open automatically. As can be seen, the disconnector 10 is now unloaded and can be safely switched to the second position (terminals 12 and 13 connected) as indicated in Figure 1 c.

[0098] In Figure 1 c, the disconnector 10 is now in the second position with the second terminal 12 connected to the common terminal 13, and so the negative conductive rail 6 and the negative terminal 3 of the power source 1 are coupled to the first terminal 21 of the circuit breaker. At this point, the circuit breaker 20 is reset or otherwise caused to close the contacts of the circuit breaker and effectively short the positive conductive rail 7 and the negative conductive rail 6 together, leaving the conductive rail 7 in a safe condition as shown in figure Id for maintenance or the like. To reconnect the power delivery system to the working condition, the steps discussed above are reversed.

[0099] In the arrangement shown, the positive terminal 2 of the power supply 1 has a first polarity and is connected to the disconnector 10, the circuit breaker 20 and the "live" conductive rail 7, while the negative terminal 3 has a second polarity and is connected to the "safe" negative return rail 6, which is normally held at or near ground potential. However, it will be appreciated that this can be reversed, with the positive terminal 2 of the power supply being connected as the "safe" potential at or near ground potential, and the negative terminal 3 providing power to the "live" conductive rail 7. In this respect, the first and second polarities of the power supply terminals can be reversed.

[0100] The disconnector 10 can also be provided with a third stable position (not shown) corresponding to an intermediate or "isolated" position, in which neither the first terminal 11 nor the second terminal 12 is electrically connected to the common terminal 13, such that both the first terminal 11 and the second terminal 12 are electrically isolated from the common terminal 13. In this way, the conductive rail 7 can be completely isolated from the positive and negative output terminals 2, 3 of the power supply 1.

[0101] Figure 2a and Figure 2b is a schematic diagram of a power delivery system, showing the flow of overcurrent (fault current) through Figure 1 the circuit in a feeder configuration and a through configuration, respectively. When overcurrent is flowing in the feeder configuration in the bus-to-cable direction as Figure 2a indicated, the one-way circuit breaker 20 will trip to open the connection of the live conductive rail 7 to the power supply 1. On the other hand, when overcurrent is flowing in the through configuration in the cable-to-through direction as Figure 2b indicated, the circuit breaker 20 will remain closed to allow current to flow to ground via the negative return rail 6. The one-way nature of the circuit breaker 20 thereby ensures that an inadvertent or accidental connection of the rail 7 to the power supply, or its exposure to a discharge such as a lightning strike, will not cause the circuit breaker 20 to trip to an open condition, which would potentially leave the conductive rail 7 live and unsafe.

[0102] However, as mentioned in the background section, there are scenarios in which negative return current can potentially flow through the power delivery system in the positive direction, which potentially trips the DC circuit breaker 20 in the through configuration.

[0103] Figure 3This is a schematic diagram showing a railway segment including eastbound track 71 and westbound track 72. The railway's DC power supply is provided by a series of substations 73 spaced apart along the tracks. Substations 73 convert AC power to DC and boost the voltage to compensate for losses caused by inefficiency in the conductor rails 7. Between these substations 73 are track parallel (TP) chambers 74 used to connect and disconnect adjacent segments 7a to 7e of the conductor rails 7. Unfortunately, many TP chambers 74 do not have rectifier power supplies 1 and therefore do not have local negative terminals. Thus, when a conductor rail 7 of a track 72 is energized (westbound track in this example) and a conductor rail 7 of the nearby track 71 is grounded (eastbound track in this example), up to 50% of the negative return current 75 on the westbound track 72 can flow in the positive direction through the TP chamber 74 toward the negative terminal of the power supply 1 at the nearest substation 73. If a fault 8 on the energized (westbound) track 72 generates an overcurrent 75, this can then cause the unidirectional circuit breaker in the TP chamber 74 to trip and open the circuit, and energize and unsafely energize the grounded conductive rail 7 on the nearby (eastbound) track 71.

[0104] The apparatus and associated methods that can solve this problem will now be described. Other examples depicted in the figures have been provided with reference numerals corresponding to similar features of the previously described examples. These numbered features may appear in the figures but may not be directly referenced in the description of these particular examples. These are still provided in the figures to aid in understanding further examples, particularly features of similar, previously described examples.

[0105] Figure 4a and Figure 4b A side view of an example device for use in a power transmission system is shown. In addition to the previously described DC circuit breaker 20 and disconnector 10, the device includes an interlocking mechanism 9. The interlocking mechanism 9 is coupled to the DC circuit breaker 20 and disconnector 10 and is configured to disable the DC circuit breaker 20 when the disconnector 10 is in the second position (i.e., the on state) to prevent automatic switching from a closed state to an open state during overcurrent conditions. This helps ensure continuity of conduction. With the inclusion of the interlocking mechanism 9, the DC circuit breaker 20 no longer needs to be unidirectional. Therefore, it can be a bidirectional circuit breaker configured to automatically switch from a closed state to an open state in both the positive and negative directions during overcurrent conditions.

[0106] The DC circuit breaker 20 comprises a first contact and a second contact corresponding to the first terminal 21 and the second terminal 22 (the first terminal 21 is not visible from this perspective). The first and second contacts are located on the first contact arm 14 and the second contact arm 15 of the DC circuit breaker 20, respectively. In this example, the first contact arm 14 is movable by rotating about the pivot 16, while the second contact arm 15 is fixed in place, but both contact arms 14, 15 can be movable. When the DC circuit breaker 20 is in a closed state, the first and second contacts are in physical (and thus electrical) contact with each other to allow current to flow therebetween.

[0107] The DC circuit breaker 20 further comprises an actuator 17 configured to cause movement of the movable contact arm 14 in response to a control signal to open the DC circuit breaker 20, and a tripping device 18 comprising an armature 19 configured to cause movement of the movable contact arm 14 during an overcurrent condition. Movement of the movable contact arm 14 causes the first and second contacts to separate from each other to form a contact gap, thereby switching the DC circuit breaker 20 from the closed state to an open state. In Figure 4a and Figure 4b An optional arc displacement mechanism can also be seen in Figs. 1 1 and 12. The arc displacement mechanism comprises a soft magnetic winding 23 configured to generate a magnetic flux in response to a control signal or an overcurrent. The ends 24 of the soft magnetic winding 23 are positioned on opposite sides of the contact gap and are shaped to form a flux gap across the contact gap. Furthermore, the ends 24 of the soft magnetic winding 23 are also shaped to diverge over the magnetic flux gap towards an arc chute, such as an arc runner (not shown). When an arc is formed between the first and second contacts of the DC circuit breaker 20, the magnetic flux across the contact gap directs the arc towards the arc chute, where it is quickly extinguished.

[0108] The actuator 17 can comprise any existing mechanism to open the DC circuit breaker 20. In Figure 4a and Figure 4b In Figs. 1 1 and 12, the actuator 17 takes the form of an electromagnetic latch configured to release stored energy in a compression spring and cause linear movement of a plunger 25. The plunger 25 then contacts the movable contact arm 14, which rotates about the pivot 16 and causes the first and second contacts to separate.

[0109] Figure 5Further details of the tripping device 18 are shown schematically. In this example, the tripping device 18 is a direct-acting tripping device including an electromagnetic actuator, but alternatively, it can be an indirect-acting tripping device (e.g., including a protective relay or transducer). The electromagnetic actuator includes a permanent magnet 26 and an adjacent (primary) armature 19 mechanically coupled to a movable contact arm. The armature 19 forms part of a yoke 28 having a predetermined air gap 29. The flux 30 from the permanent magnet 26 results in a holding force on the armature 19 that overcomes the stored force of the compression spring 31. In an overcurrent condition, current flows through the coil 32 of the electromagnetic actuator, which induces a flux 33 in the yoke 28 opposite to the flux 30 of the permanent magnet 26. Under a predetermined magnitude of overcurrent (and therefore flux 33), the stored force of the compression spring 31 exceeds the holding force of the permanent magnet 26 and releases the armature 19. The predetermined magnitude of the overcurrent / flux 33 is determined at least in part by the size of the air gap 29 in the yoke 28. The armature 19 is then accelerated forward by the action of the spring 31, which causes the movable contact arm to move to trip the DC circuit breaker.

[0110] In some examples, the electromagnetic actuator may further include a secondary armature 27 configured to move when the flux 33 in the yoke 28 exceeds a predetermined level. Figure 5 As shown, the movement of the secondary armature 27 reduces the magnetic resistance that triggers the movement of the primary armature 19 by the yoke 28. This helps prevent the tripping device from gradually becoming unstable at currents close to a predetermined level. Instead, the secondary armature 27 provides a step change to the tripping flux 33, which ensures that the tripping device opens the DC circuit breaker at the correct current level.

[0111] like Figure 4a and Figure 4b As shown in the device, the interlocking mechanism 9 is connected between the disconnecting switch 10 and the tripping device 20 (the mechanical connection between the tripping device 18 and the movable contact arm 14 is not shown). When the disconnecting switch 10 is in the first position ( Figure 4a When the interlocking mechanism 9 is in the unlocked state, this allows the primary armature 19 to move under overcurrent conditions. This enables the DC circuit breaker 20 to disconnect the energized conductive rail from the power supply when the equipment is in the feeder configuration. However, when the disconnecting switch 10 is in the second position ( Figure 4b When the device is in the ON configuration, the interlock mechanism 9 is in the OFF state, which inhibits (e.g., restrains or even prevents) the movement of the primary armature 19 under overcurrent conditions. When the device is in the ON configuration, this disables the DC circuit breaker 20 to prevent automatic switching from the OFF state to the OFF state.

[0112] Figure 6a and Figure 6b Shown in side view Figure 4a and Figure 4bFurther details of the interlocking mechanism 9 are provided. As shown, the interlocking mechanism 9 includes a mechanical assembly (although it may alternatively be an electromechanical assembly) fixed to the actuator 17 by a first bracket 34 and a second bracket 35. The mechanical assembly has a proximal link arm 36, a mid-section link arm 37, and a distal link arm 38, which are pivotally connected to each other at a pivot 39. One end of the proximal link arm 36 is pivotally connected to the disconnector 10 by a sliding connector 40, and the proximal link arm 36 and the mid-section link arm 37 are pivotally connected to the first bracket 34 by another pivot 39. The distal link arm 38 is pivotally connected to the second bracket 35 at its midpoint and has a stopping member 41 at one end. To help ensure the repeatability of the interlocking mechanism 9, the mid-section link arm 37 includes a spring 42. This prevents problems associated with component tolerances between different units and between operations of the same unit, where the disconnector 10 may stop in a slightly different position each time due to external factors such as motor voltage.

[0113] When the disconnecting switch 10 is switched from the first position to the second position, the interlocking mechanism 9... Figure 6a The configuration shown has been changed to Figure 6b The configuration is shown. As illustrated, the sliding connector 40 moves to the right, causing the proximal link arm 36 to rotate about the connecting pivot 39 into a more vertical orientation. This raises the connecting ends of the middle link arm 37 and the distal link arm 38. Since the distal link arm 38 is pivotally connected to the second support 35 at its midpoint, the distal link arm 38 rotates into a more horizontal orientation in which the blocking member 41 abuts the (primary) armature 19 of the electromagnetic actuator, thereby inhibiting their movement.

[0114] Figure 7 A perspective view of another example of the device is shown. In this example, the electromagnetic actuator of the tripping device 18 includes a fixed core 43 and a movable core 44. The movable core 44 is attached to an armature 45, which is then mechanically coupled to a movable contact arm 14 by a latch 46. As shown, the latch 46 is configured to rotate about a first pivot 47. In the event of an overcurrent, the current flowing through the fixed core 43 generates a magnetic flux that attracts the movable core 44. This causes a downward movement of the armature 45, which in turn causes rotation of the latch 46 about the first pivot 47 and a corresponding rotation of the movable contact arm 14 about a second pivot 48.

[0115] To inhibit corresponding movement of the movable contact arm 14, the interlocking mechanism 9 is configured to inhibit movement of the latch 46. To achieve this, the interlocking mechanism 9 includes a hook-shaped blocking member 41 that engages between the latch 46 and the movable contact arm 14 when the disconnect switch is in the second position. In an alternative arrangement, the hook 41 may instead engage between the armature 45 and the movable contact arm 14.

[0116] In a further example (not shown), the interlock mechanism 9 can be configured to magnetically, rather than mechanically, disable the trip device 18. In this scenario, the interlock mechanism 9 can be configured to divert the magnetic flux 33 generated by the electromagnetic actuator and thereby inhibit movement of the armature 19, 45. This can be achieved by forming the interlock mechanism 9 from a soft magnetic material configured to attract the magnetic flux 33 away from the armature 19, 45 or moving core 44.

[0117] Furthermore, rather than disabling the DC circuit breaker 20 by inhibiting operation of the trip device 18, the interlock mechanism 9 can be coupled to the moveable contact arm 14 itself and configured to inhibit movement thereof. Although not shown, it will be appreciated that this can be achieved using a variety of different (electro)mechanical interlock configurations, including blocking components 41 configured to contact and physically constrain the moveable contact arm 14.

[0118] The apparatus described herein can be modified to include an interlock system that prevents the disconnector 10 from being operated in one or both directions when the circuit breaker 20 is in the closed condition. Furthermore, if the disconnector 10 is provided with a third (“isolated”) position, the interlock system can be configured to prevent the disconnector 10 from being switched to one or more of the first, second and third positions.

[0119] Figure 8a A schematic view of a disconnector 10 in series with a DC circuit breaker 20 contained within a ground cabinet 49 is shown. In this example, the disconnector 10 comprises a moveable contact arm 50 electrically connected to the common terminal 13, which is configured to pivot between a first position in contact with the first terminal 11 (connected to the positive busbar) and a second position in contact with the second terminal 12 (connected to the negative busbar).

[0120] Figure 8b An alternative disconnector 10 is shown, in which the moveable contact arm 50 is configured to translate between the first and second positions. In this example, the moveable contact arm 50 is attached to a drive screw 77, which is rotated by the motor 59 and gear box 76 to drive the moveable contact arm 50 along the axis of the drive screw 77. The moveable contact arm 50 comprises a connector 79 having a male portion 80 and a female portion 81 for making a physical (and electrical) connection with corresponding portions 80’, 81’ on the first and second terminals 11, 12. To accommodate lateral movement without disconnecting from the common terminal 13, segments of the moveable contact arm 50 are formed from a flexible conductive material 78 (e.g. a bendable metal strip such as flexible copper).

[0121] However, a problem with the disconnector 10 is the proximity of the first terminal 11 and the second terminal 12. In order to be able to switch between the first position and the second position, the terminals 11, 12 are typically located in close proximity to each other. This creates the possibility of a flashover (or arcing flashover) between the terminals 11, 12, with positive fault currents of up to 200,000 A.

[0122] The present device can be configured to solve this problem by incorporating a shutter mechanism into the disconnector 10 that is driven by the movable contact arm 50. The shutter mechanism can be configured to at least partially obstruct the first gap 51 between the movable contact arm 50 and the first terminal 11 when the disconnector 10 is in the second position, and to at least partially obstruct the second gap 52 between the movable contact arm 50 and the second terminal 12 when the disconnector 10 is in the first position. By obstructing the gap 51, 52 between the movable contact arm 50 and the other terminal, the likelihood of an arc forming between the terminals 11, 12 is reduced. While there is still a possibility of a flashover between the first (positive) terminal 11 and the grounded cabinet 49, the positive-to-ground fault current is likely to be less than 15,000 A. Thus, the presence of the shutter mechanism reduces the severity of the maximum potential fault current and electrical explosion during a flashover event.

[0123] Although not shown in Figure 8a or Figure 8b One example of the shutter mechanism includes a first shutter and a second shutter. The first shutter and the second shutter can include a conductive material (e.g., formed of a metal or alloy such as steel) or an electrically insulating material (e.g., formed of polycarbonate or another electrically insulating material). In this example, the first shutter is configured to open and close a passageway between the movable contact arm 50 and the first terminal 11, such that the first shutter is open when the movable contact arm 50 is in the first position and closed when the movable contact arm 50 is in the second position. Similarly, the second shutter is configured to open and close a passageway between the movable contact arm 50 and the second terminal 12, such that the second shutter is open when the movable contact arm 50 is in the second position and closed when the movable contact arm 50 is in the first position.

[0124] Figure 9Another example of a disconnector 10 is shown in plan view. In this example, the movable contact arm 50 comprises a first shuttle arm 53 and a second shuttle arm 54 that are each electrically connected with the common terminal 13. The first shuttle arm 53 is movable between a non-contact position, in which it is isolated from the first terminal 11, and a contact position, in which it is in contact with the first terminal 11, and the second shuttle arm 54 is movable between a non-contact position, in which it is isolated from the second terminal 12, and a contact position, in which it is in contact with the second terminal 12. For this example, it is important that not only is the gap 55 between the first terminal 11 and the second terminal 12 blocked to help prevent direct flashover therebetween, but also that the passage between each shuttle arm 53, 54 and the respective terminal 11, 12 is closed when the shuttle arms 53, 54 are in the non-contact position. This is because the first shuttle arm 53 and the second shuttle arm 54 are electrically connected with each other and thus at the same electrical potential. As such, closing the passage helps prevent indirect flashover between the first terminal 11 and the second terminal 12 via the first shuttle arm 53 and the second shuttle arm 54.

[0125] The shutter mechanism of this example also comprises a first shutter 56 and a second shutter 57. The first shutter 56 is configured to open and close the passage between the first shuttle arm 53 and the first terminal 11, such that the first shutter 56 is open when the first shuttle arm 53 is in the contact position and the second shuttle arm 54 is in the non-contact position, and closed when the first shuttle arm 53 is in the non-contact position and the second shuttle arm 54 is in the contact position. Similarly, the second shutter 57 is configured to open and close the passage between the second shuttle arm 54 and the second terminal 12, such that the second shutter 57 is open when the second shuttle arm 54 is in the contact position and the first shuttle arm 53 is in the non-contact position, and closed when the second shuttle arm 54 is in the non-contact position and the first shuttle arm 53 is in the contact position.

[0126] As shown in Figure 9 the first shuttle arm 53 and the second shuttle arm 54 are connected to each other via a seesaw mechanism 58 and driven by a common electric motor 59, such that the first shuttle arm 53 moves from the non-contact position to the contact position at the same time as the second shuttle arm 54 moves from the contact position to the non-contact position, and vice versa. Nonetheless, the first shuttle arm 53 and the second shuttle arm 54 can alternatively be driven by respective electric motors, such that the first shuttle arm 53 only moves from the non-contact position to the contact position once the second shuttle arm 54 has already moved from the contact position to the non-contact position, and the second shuttle arm 54 only moves from the non-contact position to the contact position once the first shuttle arm 53 has already moved from the contact position to the non-contact position. For the former arrangement, there can be a short time interval in which both the first shutter 56 and the second shutter 57 are not fully open at the same time. The latter arrangement can therefore provide a slightly higher level of arc protection.

[0127] The first opener / closer 56 and the second opener / closer 57 may each include at least one door 60, which is biased to close the passage between at least one movable contact arm 50 and corresponding terminals 11, 12, and the at least one movable contact arm 50 may include an opening member 61 configured to force at least one door 60 open against bias as at least one movable contact arm 50 moves toward the corresponding terminals 11, 12. For example, the openers / closers 56, 57 may include a single hinged door or a pair of hinged doors 60 biased by springs or gravity, and the opening member may be configured to push open (one or more) doors 60 against the spring / gravity bias. Electronic control may also be used, configured to send signals to one or more sliding doors to open or close them based on the sensed position of at least one movable contact arm 50.

[0128] Figure 10 The connection to the DC circuit breaker 20 shown in Figure 4 is illustrated. Figure 9 A perspective view of the disconnector switch 10. As can be seen in this figure, the first opener 56 and the second opener 57 each include a pair of doors 60 that, under the bias of a spring 62, engage together to close the passage. Each door has a protruding member 63 configured to engage the opening member 61 of a corresponding movable contact arm 53, 54. Furthermore, the shape of the opening member 61 of the movable contact arms 53, 54 is defined as a wedge to separate the protruding member 63, forcing the door 60 to open against the spring bias as the movable contact arms 53, 54 move toward the corresponding terminals 11, 12. When the movable contact arms 53, 54 retract from the corresponding terminals 11, 12, the spring bias closes the door 60 again to reduce the risk of flashover.

[0129] Figure 11 Further details of the first terminal 11 and the second terminal 12 of the disconnecting switch 10 are shown. In this example, the first terminal 11 and the second terminal 12 are separated from each other by an electrical insulating barrier 64 (e.g., formed of polycarbonate or another electrical insulating material). The insulating barrier 64 is used to block the gap 55 between the first terminal 11 and the second terminal 12 to help prevent direct flashover between them. Furthermore, in some examples, at least one movable contact arm 50 of the DC circuit breaker 20 and the disconnecting switch 10 can be housed within an arc-limiting housing (e.g., like...). Figure 8aThe ground cabinet 49) is shown to contain any arc generated therein. In this scenario, the first terminal 11 and the second terminal 12 of the disconnector 10 can be located outside the arc limiting enclosure, and the shutter mechanism can be configured to open and close a respective passage outside the arc limiting enclosure through which at least one movable contact arm 50 must travel to contact the first terminal 11 and the second terminal 12. In this way, an arc caused by a fault within the arc limiting enclosure will be sufficiently contained to prevent harm to anyone approaching the equipment, while the shutter mechanism serves to suppress an arc between the first terminal 11 and the second terminal 12 of the disconnector 10 that would otherwise result in a significant flow of fault current.

[0130] Figure 12 is a perspective view of another example of a disconnector 10. In this example, the disconnector 10 further includes a visual position indicator 65 that indicates its status in the first position or the second position (or the third isolation position, if applicable). The visual position indicator 65 is provided by a drive indicator signal, but other types are possible. For example, the housing 66 of the disconnector 10 can include a window through which the relevant moving parts can be seen. The disconnector 10 also includes fuses, transducers, and any other electronic circuitry 67 required to control the disconnector 10.

[0131] Figure 13 A common disconnectable unit 68 is shown detached from a cabinet 70 of a power delivery system. The DC circuit breaker and the disconnector are incorporated into the common disconnectable unit 68, which brings them together to simplify implementation of interlock mechanisms coupled therebetween. In this example, the common disconnectable unit 68 is mounted on wheels 69 to form an extractable trolley to facilitate detachment from and re-attachment to the power delivery system. As Figure 8a As shown in the schematic diagram, the cabinet 70 itself can be grounded.

[0132] This arrangement allows easy access to the DC circuit breaker and the disconnector for maintenance or emergency replacement without the need to shut down the busbar of the substation (which can be a costly operation) or even a section of the railway network (typically, even more costly) for a significant amount of time when either component fails. Furthermore, one extractable trolley 68 can be quickly replaced with another in order to restore the railway network when needed.

[0133] In some examples, one or more of the shunt, the fuse, and the transducer (or any other traction supply voltage components 67) of the power delivery system can also be incorporated into the common disconnectable unit / trolley 68. This further enhances the safety, maintainability, and testability of the equipment by allowing the electronic protection system to comprehensively test from the shunt to the transducer when disconnected from the DC traction supply.

[0134] The present device has been described in the context of a power supply system for supplying electric power to a conductor rail 6, 7 of a railway or tramway infrastructure. However, it can be applied more generally to any power supply system in which a conductor, normally at live potential, must be grounded or short-circuited to a conductor at a safe potential when in a maintenance or shutdown condition.

[0135] The Applicant hereby discloses separately each and every feature described herein and any combination of two or more such features, to the extent such features or combinations are capable of being carried out based on the knowledge in the art of the description as a whole irrespective of whether such feature or combination is explicitly mentioned or not as a separate feature or combination of features. The Applicant indicates that the aspects / embodiments disclosed can consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications can be made within the scope of the disclosure.

Claims

1. An apparatus for use in a power transmission system, the apparatus comprising: A DC circuit breaker having a first terminal and a second terminal and configured to automatically switch from a closed state to an open state during an overcurrent condition. A disconnecting switch connected in series with the DC circuit breaker, the disconnecting switch having a first terminal for connection to a first polarity terminal of a DC power supply, a second terminal for connection to a second polarity terminal of the DC power supply, and a common terminal for connection to the first terminal of the DC circuit breaker, the disconnecting switch having at least a first position and a second position, in the first position the first terminal is connected to the common terminal, and in the second position the second terminal is connected to the common terminal; as well as An interlocking mechanism connected to the DC circuit breaker and the disconnecting switch is configured to disable the DC circuit breaker when the disconnecting switch is in the second position to prevent automatic switching from the closed state to the open state during the overcurrent condition.

2. The device of claim 1, wherein the DC circuit breaker includes a first contact and a second contact corresponding to the first terminal and the second terminal, the first contact and the second contact being located on a first contact arm and a second contact arm of the DC circuit breaker, respectively, and wherein at least one of the first contact arm and the second contact arm is movable.

3. The device of claim 2, wherein the DC circuit breaker includes a tripping device configured to cause movement of at least one movable contact arm during the overcurrent condition, and wherein the interlocking mechanism is coupled to the tripping device and configured to disable the DC circuit breaker by inhibiting operation of the tripping device.

4. The device of claim 3, wherein the tripping device comprises an electromagnetic actuator having an armature mechanically coupled to the at least one movable contact arm, the electromagnetic actuator being configured to generate a magnetic flux in response to an overcurrent causing movement of the armature and a corresponding movement of the at least one movable contact arm.

5. The device of claim 4, wherein the interlocking mechanism is configured to suppress the operation of the tripping device by suppressing the movement of the armature.

6. The device of claim 4, wherein the armature is mechanically coupled to the at least one movable contact arm by a latch, and wherein the interlocking mechanism is configured to suppress operation of the tripping device by suppressing movement of the latch.

7. The device of claim 4, wherein the electromagnetic actuator comprises a primary armature and a secondary armature, the primary armature being mechanically coupled to the at least one movable contact arm such that the magnetic flux causes movement of the primary armature and a corresponding movement of the at least one movable contact arm, the secondary armature being configured to move when the magnetic flux exceeds a predetermined level, the movement of the secondary armature reducing the magnetic resistance at which the electromagnetic actuator triggers movement of the primary armature, and wherein the interlocking mechanism is configured to suppress operation of the tripping device by suppressing movement of the primary armature or the secondary armature.

8. The device of claim 4, wherein the interlocking mechanism is configured to suppress the operation of the tripping device by transferring the magnetic flux generated by the electromagnetic actuator and thereby suppressing the movement of the armature.

9. The device of claim 8, wherein the interlocking mechanism comprises a soft magnetic material configured to attract the magnetic flux away from the armature when the disconnecting switch is in the second position in order to suppress the movement.

10. The device of claim 2, wherein the interlocking mechanism is coupled to the at least one movable contact arm of the DC circuit breaker and configured to disable the DC circuit breaker by inhibiting movement of the at least one movable contact arm.

11. The device according to any one of the preceding claims, wherein the disconnecting switch comprises: At least one movable contact arm electrically connected to the common terminal; as well as An opening / closing mechanism is configured to at least partially block the first gap between the at least one movable contact arm and the first terminal when the disconnecting switch is in the second position, and at least partially block the second gap between the at least one movable contact arm and the second terminal when the disconnecting switch is in the first position.

12. The device of claim 11, wherein the at least one movable contact arm comprises a first reciprocating arm and a second reciprocating arm, each electrically connected to the common terminal, the first reciprocating arm being movable between a non-contact position isolated from the first terminal and a contact position contacting the first terminal, and the second reciprocating arm being movable between a non-contact position isolated from the second terminal and a contact position contacting the second terminal, and The opening / closing mechanism includes a first opening / closing device and a second opening / closing device. The first opening / closing device is configured to open and close the passage between the first reciprocating arm and the first terminal, such that the first opening / closing device is open when the first reciprocating arm is in the contact position and the second reciprocating arm is in the non-contact position, and is closed when the first reciprocating arm is in the non-contact position and the second reciprocating arm is in the contact position. The second opening / closing device is configured to open and close the passage between the second reciprocating arm and the second terminal, such that the second opening / closing device is open when the second reciprocating arm is in the contact position and the first reciprocating arm is in the non-contact position, and is closed when the second reciprocating arm is in the non-contact position and the first reciprocating arm is in the contact position.

13. The device of claim 12, wherein the first reciprocating arm and the second reciprocating arm are connected to each other via a seesaw mechanism and driven by a common motor, such that the first reciprocating arm moves from the non-contact position to the contact position while the second reciprocating arm moves from the contact position to the non-contact position, and vice versa.

14. The device of claim 12, wherein the first reciprocating arm and the second reciprocating arm are driven by respective motors such that once the second reciprocating arm has moved from the contact position to the non-contact position, the first reciprocating arm moves only from the non-contact position to the contact position, and once the first reciprocating arm has moved from the contact position to the non-contact position, the second reciprocating arm moves only from the non-contact position to the contact position.

15. The device of claim 11, wherein the at least one movable contact arm comprises a single contact arm configured to pivot or translate between a first position contacting the first terminal and a second position contacting the second terminal, and The opening / closing mechanism includes a first opening / closing device and a second opening / closing device. The first opening / closing device is configured to open and close the passage between the single contact arm and the first terminal, such that the first opening / closing device is open when the single contact arm is in the first position and closed when the single contact arm is in the second position. The second opening / closing device is configured to open and close the passage between the single contact arm and the second terminal, such that the second opening / closing device is open when the single contact arm is in the second position and closed when the single contact arm is in the first position.

16. The device of claim 12, wherein the first opener and the second opener each include at least one door, the at least one door being biased to close the passage between the at least one movable contact arm and the corresponding terminal, and wherein the at least one movable contact arm includes an opening member configured to force the at least one door to open against the bias as the at least one movable contact arm moves toward the corresponding terminal.

17. The device of claim 16, wherein the at least one door comprises a pair of doors that come together to close the passage, each door having a protruding member configured to engage the opening member of the at least one movable contact arm, and wherein the shape of the opening member is determined to be a wedge that separates the protruding member to force the door to open against the bias when the at least one movable contact arm moves toward the corresponding terminal.

18. The device of claim 11, wherein the at least one movable contact arm of the DC circuit breaker and the disconnecting switch is housed within an arc-limiting housing, and the first terminal and the second terminal of the disconnecting switch are located outside the arc-limiting housing, and wherein the switch mechanism is configured to open and close a corresponding passage outside the arc-limiting housing, the at least one movable contact arm being required to travel through the corresponding passage to contact the first terminal and the second terminal.

19. The device according to any one of claims 1-10, wherein the first terminal and the second terminal of the disconnecting switch are separated from each other by an insulating barrier.

20. The device according to any one of claims 1-10, wherein the DC circuit breaker and the disconnecting switch are formed on a common disconnectable unit of the power transmission system.

21. The device of claim 20, wherein the common detachable unit is mounted on wheels to facilitate detachment from and reattachment to the power transmission system.

22. The device of claim 20, wherein the common disconnectable unit further comprises one or more shunts, fuses, and transducers of the power transmission system.

23. A method for configuring a power transmission system, the method comprising: The isolating switch is connected to a DC power supply such that a first terminal of the isolating switch is connected to a first polarity terminal of the DC power supply and a second terminal of the isolating switch is connected to a second polarity terminal of the DC power supply. The isolating switch has at least a first position and a second position. In the first position, the first terminal is connected to a common terminal of the isolating switch, and in the second position, the second terminal is connected to the common terminal of the isolating switch. The common terminal of the disconnecting switch is connected to the first terminal of the DC circuit breaker, which has a first terminal and a second terminal and is configured to automatically switch from a closed state to an open state during an overcurrent condition. The interlock mechanism is connected to the DC circuit breaker and the disconnecting switch such that when the disconnecting switch is in the second position, the interlock mechanism can disable the DC circuit breaker to prevent automatic switching from the closed state to the open state during the overcurrent condition. Connect the second terminal of the DC circuit breaker to the first power line; as well as Connect the second terminal of the disconnecting switch and the second polarity terminal of the DC power supply to the second power line.

24. A computer program comprising computer code configured to perform the method of claim 23.

25. A transfer switch, comprising: First terminal, second terminal, and common terminal; At least one movable contact arm is electrically connected to the common terminal and is movable between a first position and a second position, wherein in the first position the first terminal is connected to the common terminal and in the second position the second terminal is connected to the common terminal; as well as An opening / closing mechanism is configured to at least partially block the first gap between the at least one movable contact arm and the first terminal when the switch is in the second position, and at least partially block the second gap between the at least one movable contact arm and the second terminal when the switch is in the first position.

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