Switchgear with a locking device

Abstract

The invention relates to a method for controlling an interlocking device (14) of a switchgear (2) which has an electrical device (6) with a conductor (12) representing a hazard potential, wherein the interlocking device (14) is electrically is controllable and the locking device (14) can be in a closed state in which it blocks access to the equipment (6) and in an open state in which it allows access to the equipment (6), the method comprising the following steps: - Detection of a magnetic field (24) in a monitoring area around the current conductor (12); - Determining a current (I) in the conductor (12) based on the detected magnetic field (24); - if the current measurement has yielded a current (I) greater than or equal to a defined threshold value in the conductor (12), actuate the locking device (14) so ​​that it is in its closed state; and - if the current determination has resulted in a current (I) smaller than the defined threshold value in the conductor (12), actuate the locking device (14) so ​​that it is in its open state.

Description

[0001] The present invention relates to a switchgear assembly with a locking device. Technical background

[0002] For safety reasons, in order to prevent the formation of an arc, doors and access panels on medium-voltage switchgear that provide access to electrical equipment carrying dangerous voltage may only be opened when it is ensured that no current can flow. Electrical equipment could, for example, be a switching device. Similarly, movable electrical equipment, such as movable circuit breakers, may only be removed from their housing when it is ensured that no current can flow.

[0003] To prevent access to electrical equipment carrying dangerous voltage, switchgear is often equipped with mechanical interlocking devices, see e.g. DIN EN IEC 62271-200 VDE 0671-200:2023-04 High-voltage switchgear and controlgear, Part 200: Metal-enclosed AC switchgear and controlgear for rated voltages above 1 kV up to and including 52 kV (IEC 62271-200:2021); German version EN IEC 62271-200:2021, issue date: 2023-04. When a switching device is in the "switched on" position, a locking bolt is positioned by a kinematic chain so that the switching device cannot be moved out of its position in the housing; this reliably prevents an arc from forming at housing contacts such as the tulip contacts of the switching device. Doors and maintenance hatches are locked against opening in the same way.

[0004] JP S54-107846 U (Hitachi, Ltd.) 1979-07-30 describes a method for controlling an interlocking device (9) of a switchgear assembly comprising an electrical device (1) with at least one conductor representing a hazard potential, wherein the interlocking device (9) is electrically controllable and the interlocking device (9) can be in a closed state in which it blocks access to the device (1) and in an open state in which it allows access to the device (1).

[0005] CN 1 06 877 221 A (POWER SUPPLY COMPANY OF STATE GRID ANHUI ELECTRIC POWER COMPANY; STATE GRID CORPORATION OF CHINA) 2017-06-20 describes that in a switchgear, a door is locked by a control unit which, based on values ​​from sensors via data lines, controls a locking device by means of a control line.

[0006] Currently used mechanical locking devices have significant disadvantages due to their inherent design: - An assessment of whether a safe, de-energized state exists can be made based on a defined switching position of a switching device. If a switching device cannot reach this defined switching position due to a defect (e.g., a switch can no longer be switched off), maintenance personnel are denied access to the switching device. Access to the switching device via doors and maintenance hatches, or removal of the switching device from its housing, is then only possible by manipulating the locking mechanism. - The mechanical locking devices must operate smoothly and should require only a small amount of the energy supplied for a switching operation of the switching device. Therefore, the kinematic chains are constructed from relatively lightweight components that are also relatively resistant to mechanical stress. These components do not always withstand the forces applied by maintenance personnel during operation, and a locking mechanism can be bent to the point of failure. - If, in an application, both multiple access points to a switching cell and the extension of a switching device need to be locked in parallel, the mechanical design effort is very high and it is very difficult to adjust correctly. Summary of the invention

[0007] One object of the present invention is to improve the locking mechanism of a switchgear assembly.

[0008] There is a method for controlling an interlocking device of a switchgear assembly that includes electrical equipment with at least one conductor posing a hazard potential. The electrical equipment may be a switching device, such as a circuit breaker. The electrical equipment may be permanently installed in an enclosure of the switchgear assembly, such as a switch cabinet, a switch box, a high-voltage compartment of a switch box, or a switchgear panel, and may therefore be safely isolated from its surroundings; access to the electrical equipment may thus be controlled by a door or a service hatch located in the enclosure.In a switching cell, a distinction is made between a high-voltage compartment and a low-voltage compartment: A high-voltage compartment of a switching cell is a compartment in which a load current is switched; a low-voltage compartment of a switching cell is a compartment in which switching and control currents flow; the prefix "high-voltage" in the term "high-voltage compartment" should not be understood as high voltage >36 kV according to DIN EN 50160, but rather as a distinction from the low-voltage compartment. Thus, medium voltages, for example 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, 35 kV, can also be present in a high-voltage compartment of a switching cell. The electrical equipment can also be portable, as is the case, for example, with...This is the case with movable circuit breakers in a pull-out unit; access to the electrical equipment can be controlled in this case by preventing movement of the equipment via the interlocking device: the equipment cannot thus be moved out of the pull-out unit, which prevents a potentially unsafe contact with the equipment. In both variants of electrical equipment, fixed or movable, access to the equipment can therefore be blocked.

[0009] The locking device is electrically controllable. It can be in a closed state, blocking access to the equipment, or in an open state, allowing access. One process step involves detecting a magnetic field in a monitoring area around the at least one conductor. Another process step involves determining the current in the at least one conductor based on the detected magnetic field. A further process step, if the current determination yields a current greater than or equal to a defined threshold value in the at least one conductor, activates the locking device so that it is in its closed state.And a further procedural step involves, if the current determination has yielded a current smaller than the defined threshold in at least one current conductor, activating the locking device so that it is in its open state.

[0010] Access to electrical equipment while current is flowing must be avoided, as access or contact means that a person, another living being such as an animal or a plant or part of a plant (e.g., a branch, twig, or cone of a conifer), or even an inanimate object such as a tool (e.g., screwdriver, wire stripper) could come into such close contact with the equipment that the person or object could be endangered, e.g., by an unintended electrical arc from the equipment, or that the equipment could be damaged or destroyed (e.g., by a short circuit between two phases). In contrast, access to electrical equipment while no current is flowing may be intentional and desired, e.g., in the case of maintenance or repair of the electrical equipment by qualified personnel.

[0011] The problem is solved by a switchgear assembly according to the invention. The switchgear assembly comprises an electrical device which has at least one conductor that poses a potential hazard. The switchgear assembly has an electrically controllable interlocking device that can be in a closed state, in which it blocks access to the device, and in an open state, in which it allows access to the device. The switchgear assembly has two or more magnetic field sensors designed to detect a magnetic field in a monitoring area around the at least one conductor. The magnetic field sensors are arranged at two or more different locations in the monitoring area. The switchgear assembly has two or more magnetic field sensors per conductor.The switchgear includes a control unit for determining the current in at least one conductor based on the detected magnetic field and for controlling the interlocking device. The control unit is configured to control the interlocking device so that it is in the closed position if the current measurement yields a current greater than or equal to a defined threshold value in the at least one conductor. Furthermore, the control unit is configured to control the interlocking device so that it is in the open position if the current measurement yields a current less than the defined threshold value in the at least one conductor. The switchgear also includes a data line for transmitting measured values ​​from the magnetic field sensor to the control unit.And the switchgear has a control line for transmitting control commands from the control unit to the locking device.

[0012] The term "at least one conductor" can refer to a single conductor (e.g., one phase of a three-phase network) or multiple conductors, as in a three-phase circuit breaker for a three-phase network. In all cases where only one conductor is mentioned, the expert understands that this could refer to any number of conductors, e.g., one or more lines of a three-phase three-phase system.

[0013] The underlying idea of ​​the invention is that an assessment of whether a safe, current-free state exists is not based on a defined switching position of the switching device, but rather on monitoring the actual current flow that could trigger an arc.

[0014] The invention has, among other things, the following advantages: - Because a locking device used according to the invention is electrically controllable, any number of locking devices can be controlled in parallel without any problems. This was not the case with known mechanical locking devices. - The magnetic field detection allows a switching device blocked in an ON position to be accessed when a higher-level switch has de-energized the affected switchgear, so that no magnetic field is measured anymore. - A locking mechanism using an electrically controlled locking device can be designed using the closed-circuit principle so that no energy from the electrical equipment is required to activate the locking mechanism. - Mechanical damage to the mechanical locks due to excessive force applied by maintenance personnel can be easily prevented by design.

[0015] Preferred applications of the invention are medium-voltage switchgear and medium-voltage switchgear, but also low-voltage switchgear and low-voltage switchgear. Further applications include electrical operating rooms and control cabinets. Embodiments of the invention

[0016] Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0017] According to a preferred embodiment of the invention, the locking device operates by means of an electromagnet according to the closed-circuit principle. Locking is effected by an electromagnet which, in its active state, releases the doors from opening or the switching device from extending. The electromagnet is controlled by a magnetic field measurement performed by at least one magnetic field sensor installed within the switchgear, which determines the magnetic field in the area to be monitored, e.g., in the area of ​​the power supply to the equipment. If a magnetic field with a frequency corresponding to the frequency of the current flowing in the at least one conductor is detected at an intensity that indicates a current flowing through the conductor(s), the electromagnet remains in its rest position and prevents the access points from opening or the switching device from extending.An advantage of this is that a locking mechanism using an electromagnet can be designed using the closed-circuit principle in such a way that no energy from the electrical equipment is required to activate the locking mechanism.

[0018] According to a preferred embodiment of the invention, if the current measurement reveals a current below the defined threshold in the conductor(s), the interlocking device is automatically controlled by a control unit, either directly or following an external trigger command, to be in its open position. If no current flow is detected, the interlocking device is moved to its open position, either directly or triggered by an external trigger command, e.g., by operation by maintenance personnel, and access to the switchgear or the extension of the switching device is permitted.

[0019] According to the invention, the switchgear comprises two or more magnetic field sensors for detecting a magnetic field in a monitoring area around the at least one current conductor, wherein the magnetic field sensors are arranged at two or more different locations within the monitoring area. To reliably cover every electrical load case in three-phase systems, at least two magnetic field sensors, e.g., Hall sensors, are to be used at different locations within the monitoring area. This ensures that in all load conditions (symmetrical load, unbalanced load, different power factors cos phi of the three phases of a three-phase line), at least one of the magnetic field sensors can detect a magnetic field resulting from the three phases of a three-phase line.

[0020] According to a preferred embodiment of the invention, the switchgear has a release unit designed as an HMI (= Human Machine Interface) to receive a release command from an operator of the switchgear, e.g. by pressing a push button or by sending a release command from a communication device such as a smartphone, and in response to the received release command, to trigger the control unit to actuate the locking device, so that the locking device switches to the open state if the current determination has resulted in a current smaller than the defined threshold value in the current conductor.

[0021] According to a preferred embodiment of the invention, the control unit is configured to receive the defined threshold value as input and to monitor the function of the at least one magnetic field sensor. The control unit can include evaluation electronics for this purpose. It is possible for the control unit to monitor adjustable threshold values ​​for the release of the electromagnet, monitor both the function of the magnetic field sensors and the intensity of the measured magnetic fields, and decide on the activation of the electromagnet depending on the intensity of the measured magnetic fields.

[0022] According to a preferred embodiment of the invention, the switchgear has two or more locking devices, all of which are controlled by the control unit. Exemplary implementation examples of the drawings

[0023] The invention will now be explained using several exemplary embodiments and the accompanying drawings.

[0024] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood through the following description of exemplary embodiments, which will be explained in more detail with reference to the drawings. The drawings are schematic and not to scale. Fig. 1 a switchgear with a current-carrying conductor; Fig. 2 the switchgear of Fig. 1, but without current flow in the conductor; Fig. 3 a flowchart of a process; Fig. 4 a medium-voltage switchgear; and Fig. 5 a section of a switchgear panel of the medium-voltage switchgear. Detailed description of the exemplary implementations

[0025] For simplicity, the current-carrying conductors are represented by a single line in the diagrams ("single line diagram"). This representation should not be interpreted restrictively, but includes any number of conductors; three-phase power systems are typically used.

[0026] Fig. Figure 1 shows a switchgear 2 (switching cell) which has a housing 4 (high-voltage compartment of the switching cell) in which an electrical device 6, here: a switching unit, is permanently installed. Outside the high-voltage compartment, in the low-voltage compartment, is the electronics, etc. A conductor 12 runs through the electrical device 6, which poses a hazard to an operator of the switchgear (repair technician, plant operator, maintenance personnel, inspector, etc.) if current I flows through the conductor 12. Fig. Figure 1 shows a single-phase electrical system. It can also be read as a "single-line diagram" of a three-phase electrical system, in which all three phases are technically identical.

[0027] To protect against personal injury, the switching device 6 is permanently mounted and enclosed within the housing 4 and is accessible only through a door 16 of the housing 4. An electrically controlled locking device 14 is capable of either blocking or allowing the opening of the door 16. The locking device 14 can be moved into a closed position by a control command, thereby blocking the door 16 and thus preventing access to the switching device 6. Conversely, the locking device 14 can also be moved into an open position by a control command, thereby releasing the door 16 and thus allowing access to the switching device 6. The locking mechanism is activated by an electromagnet 18, which, when energized, releases the door 16 by retracting a door bolt.

[0028] A current I in the conductor 12 generates a magnetic field 24 in the vicinity of the conductor 12. This field can be detected by two magnetic field sensors 10, which are arranged in the area around the conductor 12, the so-called monitoring zone. The magnetic field sensors 10 transmit the measured values ​​they have recorded with respect to the magnetic field 24 via data lines 26 to a control unit 8, where the measured values ​​are evaluated. Based on the recorded magnetic field measurements, the control unit 8 determines the current I in the conductor 12. Since the current determination by the control unit 8 has resulted in a current I in the conductor 12 that is greater than or equal to a defined threshold value, the control unit 8 controls the locking device 14 so that it is in its closed state. Because the locking device 14 is in its closed state, it blocks the door 16.The control commands with which the control unit 8 controls the locking device 14 are transmitted from the control unit 8 to the locking device 14 via a control line 28.

[0029] Furthermore, the switchgear 2 has a trip unit 20, from which an external trip signal 22 can be sent to the control unit 8, e.g., by manually pressing a push button (electric switch) or by sending a trip command from a communication device such as a smartphone to the trip unit 20. The trip unit 20 can be configured as an HMI to receive a trip command from an operator of the switchgear. In response to a received trip command, the trip unit 20 triggers the control unit 8 by means of a trip signal 22, so that the control unit 8 actuates the interlocking device 14 such that the interlocking device 14 switches to the open state if the current measurement has shown a current less than the defined threshold value in the conductor 12.

[0030] Fig. Figure 2 shows the same switchgear 2 as in Fig. 1, except that no current is now flowing in the conductor 12. Therefore, the two magnetic field sensors 10 do not measure a magnetic field generated by a current flow. The control unit 8, by evaluating the measured values ​​received from the two magnetic field sensors 10, concludes that no current is flowing in the conductor 12.

[0031] Although the magnetic field sensors 10 may measure one or more other magnetic fields, e.g. the Earth's magnetic field or a magnetic field of an electromagnet or permanent magnet located in the vicinity of the switchgear 2, the control unit 8 is able to assign a magnetic field to a current through the conductor 12 if the magnetic field varies at a frequency that corresponds to the frequency of the current flowing in the conductor 12.

[0032] Since the current measurement by the control unit 8 resulted in a current of zero, i.e., a current less than a defined threshold value, the control unit 8 controls the locking device 14 so that it is in its open state. The control commands with which the control unit 8 controls the locking device 14 are transmitted from the control unit 8 to the locking device 14 via the control line 28. Since the locking device 14 is in its open state, it does not block the door 16. The locking device 14 releases the door 16, which can therefore be opened to grant access 30 to the switching device 6.

[0033] Fig. Figure 3 shows a flowchart of a method for controlling an interlocking device of a switchgear assembly. The switchgear assembly includes an electrical device with a live conductor that poses a potential hazard. The interlocking device is electrically controllable. The interlocking device can be in a closed state, blocking access to the device, or it can be in an open state, allowing access. The method includes a step 31 in which a magnetic field is detected in a monitoring area around the live conductor. The method includes a subsequent step 32 in which the current in the live conductor is determined based on the detected magnetic field.Following the aforementioned step 32, a test step 33 is performed: either (first alternative 34) the current measurement has yielded a current greater than or equal to a defined threshold value in the conductor, or (second alternative 36) the current measurement has yielded a current less than the defined threshold value in the conductor. In the case of the first alternative 34, the locking device 35 is actuated so that it is in its closed state. In the case of the second alternative 36, the locking device 37 is actuated so that it is in its open state.

[0034] Fig. Figure 4 shows a front side 40 of a medium-voltage switchgear 2 comprising four enclosures 4.1, 4.2, 4.3, 4.4 (“switchgear bays”). Each of the enclosures 4.1, 4.2, 4.3, 4.4 has a switchgear compartment 41, a cable connection compartment 42, a busbar compartment 43 and a low-voltage compartment 44. A circuit breaker 6 is arranged in the switchgear compartment 41.

[0035] Fig. Figure 5 shows a section of the right-hand housing 4.4. The circuit breaker 6 is mounted on guide rails 45, by means of which the circuit breaker 6 can be pulled out 46A and pushed back 46B from the switchgear compartment 41 towards the front 40 for replacement, repair, and maintenance. A conductor 12 runs through the circuit breaker 6, which, when the circuit breaker 6 is pushed 46B into the switchgear compartment 41, is electrically connected to a power supply 48 by means of plug-in contacts 47, e.g., tulip contacts. One of the plug-in contacts 47 is connected to a busbar and another to the cable in the cable connection compartment; this is a "common" design in which energy flows from the busbar to the outgoing circuits.

[0036] The conductor 12 poses a hazard to an operator of the switchgear (repairman, plant personnel, maintenance personnel, inspectors, etc.) if current I flows through the conductor 12. To protect against personal injury, the circuit breaker 6 is located in the switchgear compartment 41 and is only accessible after the circuit breaker 6 has been pulled out of the switchgear compartment 41 towards the front 40.

[0037] In the switch compartment 41 on the front 12, a locking device 14 with an electromagnet 18 is arranged. Depending on the position to which the electromagnet 18 moves a movable bolt (locking bolt), it can block or allow rail-bound movement (i.e., travel on the rails 45) of the circuit breaker 6 on the rails 45. The locking device 14 can be brought into a closed state by a control command, thus blocking rail-bound movement of the circuit breaker 6 and therefore access to it. Since the locked state is the rest state, it is also possible that no control command is required to bring the locking device 14 into a closed state.On the other hand, the locking device 14 can also be brought into an open state by a control command, thereby enabling rail-bound movement of the circuit breaker 6 and thus allowing access to the circuit breaker 6. The locking is effected by means of the electromagnet 18, which, in the active (energized) state, enables the rail-bound movement of the circuit breaker 6 by retracting the movable bolt.

[0038] A current I in the conductor 12 generates a magnetic field in the vicinity of the conductor 12, which can be detected by two magnetic field sensors 10 located in the area around the conductor 12, the so-called monitoring zone. The magnetic field sensors 10 transmit the measured values ​​they have acquired with respect to the magnetic field 24 via data lines 26 to a control unit 8 located in the low-voltage compartment 44, where the measured values ​​are evaluated. Based on the acquired magnetic field measurements, the control unit 8 determines the current I in the conductor 12. Since the current determination by the control unit 8 has resulted in a current I in the conductor 12 that is greater than or equal to a defined threshold value, the control unit 8 controls the locking device 14 so that it is in its closed state.Since the locking device 14 is in its closed state, it blocks any rail-bound movement of the circuit breaker 6. The control commands with which the control unit 8 actuates the locking device 14 are transmitted from the control unit 8 to the locking device 14 via a control line 28. Reference symbol list 2 Switchgear 4 Housing, switch panel, switch cell 4.1 Housing, control panel 4.2 Housing, control panel 4.3 Housing, control panel 4.4 Housing, control panel 6 electrical equipment, switching device 8 Control unit 10 Magnetic field sensor 12 conductors 14 Locking device 16 Door 18 Electromagnet 20 trigger unit 22 Trigger command 24 Magnetic field 26 Data line 28 Control line 30 access 31st procedural step 32nd process step 33. Procedure step 34th process step 35th process step 36th process step 37th process step 40 Front 41 Switch room 42 Cable connection room 43 Busbar compartment 44 Low-voltage room 45 rails 46A Pulling the circuit breaker 46B Pushing in the circuit breaker 47 Insert contacts (tulip contacts) of the circuit breaker 6 48 Power supply I Electricity

Claims

[1] Switchgear (2) comprising: - an electrical device (6) with at least one conductor (12) that presents a hazard potential; - an electrically controlled locking device (14) which can be in a closed state in which it blocks access to the equipment (6) and in an open state in which it allows access to the equipment (6); - two or more magnetic field sensors (10) for detecting a magnetic field (24) in a monitoring area around the at least one current conductor (12), wherein the magnetic field sensors (10) are arranged at two or more different locations in the monitoring area; - a control unit (8) for determining a current (I) in the at least one current conductor (12) on the basis of the detected magnetic field (24) and for controlling the locking device (14) so ​​that it is in its closed state if the current determination has resulted in a current (I) greater than or equal to a defined threshold value in the at least one current conductor (12), and for controlling the locking device (14) so ​​that it is in its open state if the current determination has resulted in a current (I) less than the defined threshold value in the current conductor (12); - a data line (26) for transmitting measured values ​​from the magnetic field sensor (10) to the control unit (8); and - a control line (28) for transmitting control commands from the control unit (8) to the locking device (14), wherein the switchgear (2) has two or more magnetic field sensors (10) per conductor (12). [2] Switching system (2) according to claim 1, wherein the locking device (14) has an electromagnet (18) which operates according to the quiescent current principle. [3] Switchgear (2) according to one of claims 1 or 2, comprising a release unit (20) designed as an HMI to receive a release command from an operator of the switchgear (2) and, in response to the received release command, to trigger the control unit (8) to actuate the locking device (14) so ​​that the locking device (14) switches to the open state if the current determination has resulted in a current (I) less than the defined threshold value in the current conductor (12). [4] Switchgear (2) according to one of claims 1 to 3, wherein the control unit (8) is configured to receive the defined threshold value as input and to monitor the function of the at least one magnetic field sensor (10). [5] Switchgear (2) according to one of claims 1 to 4, comprising two or more locking devices (14) all of which are controlled by the control unit (8).

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