Circuit breaker with control module

Abstract

A single-pole circuit breaker (100) is configured to conduct a current (I) while the single-pole circuit breaker is closed. The single-pole circuit breaker comprises: a trip unit (102) configured to open the single pole circuit breaker when the current exceeds a threshold current; an energy harvester (104) configured to harvest energy during operation (either a switching on operation, switching off operation or continuous current supply when connected to a load) of the single-pole circuit breaker; and a control module (106) powered by the energy harvester, wherein the control module is configured to send data relating to the operation of the single pole circuit breaker to an external device via a wireless communication. The energy harvester may harvest mechanical energy input to the circuit breaker such that actuation of the circuit breaker from an open position to a closed position deforms a dielectric elastomer.

Description

Field This disclosure relates to a circuit breaker with a control module. In particular, the disclosure relates to a single-pole circuit breaker with a control module for sending wireless communications. Background The performance of a circuit breaker is affected over its lifecycle by the operating conditions it has experienced. For example, a circuit breaker that has experienced many short circuit conditions may require maintenance or replacement at an earlier time in comparison to a circuit breaker that has experienced no faults. It is useful for a circuit breaker to comprise a control electronics for recording and sending information relating to the operation of the device to external entitles. Control electronics for providing such communications may be powered using a neutral line of a circuit breaker. In single-pole circuit breakers, however, no such neutral line is present. Therefore, it is not straightforward to combine control electronics for use in multi-pole circuit breakers with single-pole circuit breakers. There is a need, therefore, for a single-pole circuit breaker that is capable of recording and / or sending data relating to the operating conditions of the device to external devices. Summary Disclosed herein is a single-pole circuit breaker and a method of operating the singlepole circuit breaker. A single-pole circuit breaker is configured to conduct a current while the single-pole circuit breaker is closed. The single-pole circuit breaker comprises a trip unit configured to open the single-pole circuit breaker when the current exceeds a threshold current; an energy harvester configured to harvest energy during operation of the single-pole circuit breaker; and a control module powered by the energy harvester, wherein the control module is configured to send data relating to the operation of the single-pole circuit breaker to an external device via a wireless communication. Because the control module is powered by energy harvested during operation of the circuit breaker, control circuitry can be provided without the need for power supplied by a neutral line. The information provided by the control module to an external device can be used to make decisions regarding the maintenance, safety, and lifespan of the circuit breaker. In some examples, the energy harvester is configured to harvest energy during one or more of: a switching on operation, a switching off operation, or continuous current supply when connected to a load. In some examples, the single-pole circuit breaker comprises storage means configured to store the harvested energy, and the control module is powered from the storage means. In some examples, the circuit breaker comprises an engagement knob for manual opening and closing of the circuit breaker. In some examples, the energy harvester is configured to harvest mechanical energy input by an external entity to the engagement knob, wherein the energy harvester comprises the engagement knob and a dielectric elastomer element coupled to the engagement knob, the energy harvester being configured such that actuation of the engagement knob from an open position to a closed position causes the dielectric elastomer element to be deformed into a stretched state and wherein movement of the engagement knob from the closed position to the open position allows the dielectric elastomer element to return to a relaxed state, wherein the capacitance of the dielectric elastomer element is lower in the relaxed state than the stretched state such that an initial voltage across the dielectric capacitor increases when the single-pole circuit breaker is opened. In some examples, the increased voltage across the dielectric elastomer is used to power on the control module for a period of time after the single-pole circuit breaker is opened, and the control module sends data relating to the operation of the device in a wireless communication to the external device during the period of time that the control module is powered on. In some examples, the single-pole circuit breaker comprises a voltage source configured to provide the initial voltage across dielectric elastomer element when the dielectric elastomer element is in the stretched state. In some examples, the trip unit is a magnetic trip unit comprising a magnetic element, and wherein the energy harvester comprises a coil winding disposed around at least part of the magnetic element. In some examples, the coil winding is formed of an amorphous magnetic wire. In some examples, the magnetic element comprises a solenoid through which the current flows, and wherein the current in the solenoid induces a second current in the coil winding or a voltage between ends of the coil winding. In some examples, the coil winding is disposed inside the solenoid. In some examples, the data relating to the operation of the single-pole circuit breaker comprises one or more of: an indication that a short circuit condition has occurred; an indication that an overload condition has occurred; a number of times that a short circuit condition has occurred; a number of times that an overload condition has occurred; the amount of time that the single-pole circuit breaker has spent connected to a load; the magnitude of current during a short circuit condition or overload condition; and the number of switching operations that the single-pole circuit breaker has performed. In some examples, the control module is configured to measure a voltage across the coil winding, and wherein the control module is configured to calculate a current in the solenoid based on the voltage across the coil winding. In some examples, the control module is configured to increment a short circuit counter when the voltage across the coil winding increases above a first threshold value within a second threshold time duration; and the control module is also configured to increment an overload counter when the voltage across the coil winding increases above a third threshold value within a fourth threshold time duration and the short circuit counter is not incremented, wherein the first threshold is greater than the third threshold and the second threshold time duration is less than the fourth threshold time duration, and wherein the data relating to the operation of the singlepole circuit breaker comprises the value of short circuit counter and the value or the overload counter. In another aspect of the disclosure, a method of operating a single-pole circuit breaker is provided. The method comprises: harvesting energy from the single-pole circuit breaker when the single-pole circuit breaker in operation; providing the harvested energy to a control module; and sending, from the control module to an external device, data relating to the operation of the single-pole circuit breaker to an external device via a wireless communication. In some examples, the method of claim further comprises opening, by a trip unit of the single-pole circuit breaker, electrical contacts of the single-pole circuit breaker when a current flowing through the single-pole circuit breaker exceeds a threshold current; wherein the data relating to the operation of the single-pole circuit breaker comprises an indication that the circuit breaker has been opened. Brief Description of the Figures The detailed description is with reference to the following figures. Figure 1 shows a schematic diagram of a controllable circuit breaker and a system comprising the circuit breaker and a remote device; Figure 2a and 2b illustrate cross-sectional views of a single-pole circuit breaker in a closed position and an open position respectively; Figures 3a and 3b illustrate cross-sectional views of a portion of a single-pole circuit breaker in a closed position and an open position respectively; Figure 4 shows a circuit diagram illustrating a simple circuit suitable for use in an energy harvesting mechanism In an example of a single-pole circuit breaker; Figure 5 shows a schematic diagram of an energy harvesting mechanism in another example of a single pole-circuit breaker; Figure 6 illustrates a schematic cross-sectional view of a single-pole circuit breaker comprising an example of an energy harvesting mechanism; Figure 7 shows a flowchart illustrating an example method of using a circuit breaker as described herein. Detailed Description With reference to Figure 1, a controllable circuit breaker 100 is described. The circuit breaker is preferably a single-pole circuit breaker. The circuit breaker is optionally a low voltage circuit breaker, for example for residential or domestic applications, such as a miniature circuit breaker, MCB. However, the principles described herein are applicable to any type of circuit breaker, including but not limited to an RCD, RCCB, RCBO, or other. Preferably the circuit-breaker comprises at least one of a coil winding in a main current path or an engagement knob for user actuation of a switching mechanism. As shown in Figure 1, a current line 118 is defined through the circuit breaker 100, along which a current I flows when the circuit breaker 100 is closed. The current conduction line can be opened or closed by operation of a switch or other opening mechanism 120; when the switch is dosed, the circuit breaker is closed and current J flows. This switch 120 can be opened to interrupt the current flow through the circuit breaker 100. Preferably, the switch 120 comprises electrical contacts that are mechanically separated from each other when the switch 120 is opened. The circuit breaker 100 comprises a trip unit 102, which is configured to open the circuit breaker when the current exceeds a threshold. The threshold is a predetermined threshold and can be determined by the requirements or application of the circuit breaker. The threshold may defined by a time-current curve that depends on the duration for which the current occurs. For example, the trip unit may be configured such that the duration for which an overcurrent must occur before tripping is shorter when the magnitude of the current is greater. Any suitable trip unit or trip mechanism can be used to open the circuit breaker 100 in response to an overcurrent or other fault condition. For example, the tip unit 102 may be a magnetic trip unit. The circuit breaker further comprises an energy harvester 104 configured to harvest energy from the circuit breaker during operation. Operation of the circuit breaker includes, for example, switching operations from on to off, switching operations from off to on, and continuous current conduction when supplying power to a connected load. Any suitable energy harvester can be used. Specific examples of the energy harvesters 104 are discussed below in more detail with reference to Figures 2 to 7. By providing a passive energy harvester within the circuit breaker, ambient energy generated during normal operation of the circuit breaker 100 can be used to power control electronics to provide data relating to the operation of the circuit breaker to an external device. This is of particular advantage in applications where power cannot be drawn from the supply side in an "off" condition of the breaker and / or where there is no neutral line available. The circuit breaker further comprises a control module 106, which is powered by the energy harvester 104. The control module 106 comprises a wireless communication interface and is configured to send data relating to the operation of the single-pole circuit breaker to an external device 114 via wireless communication. The data relating to the operation of the single-pole circuit breaker may comprise an indication that the circuit breaker has opened the switch 120 on detecting a trip condition. In some examples, the control module 106 may determine Information relating to various aspects of the operation of the single-pole circuit breaker. For example, the control module 106 may determine one or more of: the occurrence of a short circuit condition; the occurrence of an overload condition; the number of times that a short circuit condition has occurred; the number of times that an overload condition has occurred; the amount of time that the single-pole circuit breaker has spent connected to a load; the magnitude of current during a short circuit condition or overload condition; and the number of switching operations that the single-pole circuit breaker has performed. The control module 106 is configured for wireless communication with the external device 114, where the device 114 Is provided remote from the circuit breaker 100 (this is an optional feature, as indicated by the dashed lines in Figure 1). Any suitable wireless communication protocol can be used to communicate between the remote device 114 and the control module 110, including but not limited to, any cellular connection (e.g. 2G, 3G, 4G, 5G), a Wi-Fi connection, a Bluetooth connection, a Bluetooth Low Energy BLE connection, a Zigbee connection, or the like. The disclosure is not limited to these specific protocols, and it will be understood that communication using any future wireless communication protocols is also envisaged herein. By providing a wireless communication module in this way, information relating to the operation of the circuit breaker can be provided to the external device 114. The information relating to the operation of the circuit breaker can be can be stored and used by the external device 114 or other external parties to assess the performance and condition of the circuit breaker. This information can be used to make decisions regarding the maintenance, replacement, or continued use conditions of the circuit breaker. In some examples, the energy harvester 104 may generate sufficient power to continuously power the control module 106. In these examples, information may be provided wirelessly to an external device at regular time intervals or only when a particular operating condition has occurred, such as when a switching operation occurs. In other examples, the energy harvester 104 may only generate sufficient power to power the control module 106 during particular operating conditions, such as during a short-circuit condition, an overcurrent condition or when a switching operation takes place. In these examples, the control module 106 may be powered on in for a short period of time during which it is able to wirelessly communicate with an external device. For example, the control module 106 may be provided with power by the energy harvester for a period of several seconds. For example, in some embodiments the control module may be provided with power from the energy harvester for a period of up to 5 seconds. With reference to Figures 2a, 3b, 3a, 3b and 4, an example of a single-pole circuit breaker in which the energy harvester 104 comprises a dielectric elastomer element 220 is described. In this embodiment, mechanical energy provided to an engagement knob 210 is converted into electrical power by the stretching and relaxation of the dielectric elastomer element 220. A detailed discussion of principles of electrical energy generation using dielectric elastomer materials can be found in A Review of Dielectric Elastomer Generator Systems, Moretti et al., Advanced Intelligent Systems, Volume 2, Issue 10. The circuit breaker 100 comprises a line terminal 234 and a load terminal 233. A current line 118 (the current line within the circuit breaker is not shown) is defined through the circuit breaker between the line terminal 234 and the load terminal 233. When the circuit breaker 100 is closed, a current I flows between the line terminal 234 and the load terminal 233 via a trip unit 102 and a switch 120. The switch 120 preferably comprises electrical contacts that that are configured to be mechanically separated when the trip unit 120 of the circuit breaker detects that the current I exceeds a threshold current. The trip unit 102 comprises a solenoid 231 and armature 232 shown in Figures 2a and 2b. The trip unit 102 may be substantially the same as that described in more detail below with reference to Figure 5. The circuit breaker comprises an engagement knob 210 that can be manually operated by a user to open and close the switch 120, and thereby turn the circuit breaker off or on. The mechanical contacts of the switch 120 may be coupled to a spring mechanism 230 that biases the mechanical contacts of the switch 120 into an open position. When the engagement knob 210 is moved by a user into the closed position, the spring mechanism 230 is compressed, and the switch 120 is held in the closed position by a latch mechanism. On detecting a current exceeding a threshold, the trip unit 102 may release the latch mechanism, causing the spring to force the switch 120 into an open position in which the mechanical contacts are separated. While the embodiments described herein specify that a user actuates the engagement knob 210, another external entity, such as a mechanical actuator, may be used to actuate the engagement knob 210. The energy harvester 104 comprises the engagement knob 210 and a dielectric elastomer element 220 coupled to the engagement knob 210. The dielectric elastomer element 220 has a greater capacitance when stretched than when in a relaxed state. The dielectric elastomer element 220 is preferably a substantially flat membrane and may have the form of a substantially rectangular strip. The dielectric elastomer element 220 is formed from a dielectric elastomer material, such as an acrylic elastomer or a silicone elastomer (polydimethylsiloxane). A first end of the dielectric elastomer element 220 is coupled to engagement knob 210. The first end of the dielectric elastomer element 220 may be directly connected to a linkage element 211 that is connected to a rotating portion of the engagement knob 210. A second end of the dielectric elastomer element 220 may be fixed within the circuit breaker 100. Rotation of the engagement knob 210 by a user from an open position to a closed position causes the first end of the dielectric elastomer element 220 to move away from the fixed second end, thereby causing the dielectric elastomer element 220 to be stretched. In other words, part of the mechanical energy provided by the user when moving the engagement knob 210 from the open position to the closed position is used to induce a strain in the dielectric elastomer element 220. The dielectric elastomer element 220 is chosen such that its capacitance increases when it is in a stretched state. While the dielectric elastomer element 220 is in the stretched state, a voltage source 131 applies an initial voltage between upper and lower surfaces of the dielectric elastomer element 220. The voltage source 131 may comprise a capacitor or supercapacitor. When the engagement knob 210 moves back from the closed position to the open position, for example when the circuit breaker is tripped on detecting a short circuit condition, the dielectric elastomer element 220 returns to the relaxed state. The capacitance of the dielectric elastomer element 220 decreases as it returns to its relaxed state, and a voltage across the dielectric elastomer element 220 increases. As the voltage across the dielectric elastomer element 220 increases while the charge remains constant, the electrical energy of the dielectric elastomer element 220 increases. The increased voltage across the dielectric elastomer element 220 is used to power the control module 106 or to charge a storage unit 110 that is used to power the control module 106. The increased voltage may also be used to charge the voltage source 131 that provides the initial voltage to the dielectric elastomer element 210 for the next cycle. During the above-described process, mechanical energy provided by a user when moving the engagement knob 210 from the open position to the closed position and stretching the dielectric elastomer element 210 is converted into electrical energy. In this example, mechanical energy Is input into the circuit breaker 100 when the engagement knob 210 is moved from the open position to the closed position, and electrical energy is generated when the circuit breaker 100 returns to the open position from the closed position. As such, electrical energy is extracted during a switching cycle of the circuit breaker 100. For example, electrical energy may be extracted when the trip unit 102 Identifies a current that exceeds a pre-defined threshold and causes the circuit breaker 100 to open. The circuit breaker 100 may use the energy generated when the circuit breaker 100 is opened to power on the control module 106 for a period of time. During the period of time in which the control module 106 is powered, the control module 106 may send a wireless communication to an external device 114 including data relating to the operation of the circuit breaker 100. For example, the control module 106 may provide an indication that the circuit breaker 100 has opened under a tripping condition, or may provide an indication of the total number of times that the circuit breaker 100 has been opened under current. In some examples, the control module 106 may be provided with or infer further information regarding the operation of the circuit breaker and may provide this information to the external device 114. The energy harvester 104 may provide a DC current directly to the control module 106 or may provide energy to a storage 110. Where the energy harvester 104 provides energy to a storage 110, the energy harvester 104 may provide sufficient energy to the storage 110 after a switching single cycle to power the control module 106. In some examples, the energy harvester 104 may provide energy to the storage 110 over several cycles before sufficient energy has accumulated to allow the control module 106 to power on and send a wireless communication to the external device. In examples where the control module 106 does not send a wireless communication with every switching cycle, the control module 106 may be provided with sufficient energy to power on each cycle and increment a counter indicating a number of switching cycles of the device. Figure 4 illustrates a simple circuit diagram that is suitable for use in the energy harvester 104 of this embodiment. A voltage source 131 is provided in parallel with the dielectric elastomer element 220 and with a storage 110. A first diode 141 Is disposed between the voltage source 131 and the dielectric elastomer element 220, and a second diode 141 is disposed between the dielectric elastomer element 220 and the storage 110. The voltage source 131 may be a pre-charged capacitor, which is charged by the dielectric elastomer element 220 at the end of the charging cycle. The use of first and second diodes 141 in the circuit arrangement of Figure 4 removes the requirement for switch synching during the energy harvesting cycle. Alternatively, switches can be provided to selectively isolate the voltage source 131, the dielectric elastomer element 220 and the storage 110 from each other. After the dielectric elastomer element 220 has been stretched into the stretched state, the voltage source 131 may be connected to the dielectric elastomer element 220 to cause charge to build up on opposite sides of the dielectric elastomer element 220. The dielectric elastomer element 220 may then be disconnected from the voltage source 131 and the storage 110 before returning to the relaxed state. As such, the amount of charge on the dielectric elastomer element 220 remains constant as the capacitance increases and the voltage across the dielectric elastomer element 220 increases. In the relaxed state, the dielectric elastomer element 220 may be connected to the storage 110 to provide energy to the storage 110 and may be connected to the voltage source 131 to charge the voltage source for the next energy harvesting cycle. Other circuitry and energy harvesting cycles may be used in order to provide the variable capacitor harvesting means. Figures 5 and 6 illustrate an alternative embodiment in which the energy harvester 104 comprises a coil winding 536 disposed around the solenoid 231 of the trip unit 102. The coil winding 536 may also be disposed inside of the solenoid 231 in a variation of this embodiment that is not illustrated. The arrangement of the circuit breaker 100 in this embodiment may be substantially the same as that described with reference to Figures 2a and 2b other than the energy harvester 104, and features not directly relating to the energy harvester 104 are not described below in order to avoid repetition. In this example, the trip unit 102 is a magnetic trip unit. Magnetic trip units (also called herein magnetic release mechanisms) are configured to trip when the magnetic force generated by the current flowing through the circuit breaker exceeds a certain threshold. They typically have a solenoid 231 or similar mechanism that pulls or pushes a component (also called an armature or solenoid plunger) in order to physically trip the breaker. For example, the current flowing through the circuit breaker 100 flows through the coll of wire forming part of the solenoid 231, generating a magnetic force within the core 230 of the coil. As the current through the circuit breaker Increases, so does the magnetic force, and once the magnetic force is large enough the component moves and opens the circuit breaker. The magnetic trip unit 102 of Figure 5 comprises a magnetic element, in this example a solenoid 231 wound around a magnetic core 230. The solenoid 231 is part of current line 118. A component or armature 232 is configured to move in the direction indicated by the arrow when the current I flowing through the solenoid 231 exceeds a threshold. The threshold is a predetermined threshold, and can be determined by the requirements or application of the circuit breaker. The threshold may be defined by a time-current curve. The movement of the armature 232 trips the circuit breaker 100 by opening the switch mechanism 120 and interrupting the current flow along current line 118. The energy harvester 104 in this instance comprises a coil winding 536 disposed around at least part of the solenoid 231. By arranging the coil winding 536 around the solenoid 231, the coil winding 536 and the solenoid 231 are magnetically coupled. An alternating current I flowing through the solenoid 231 therefore induces a second current I_2 in the coil winding or a voltage between the ends of the coil winding. In this way, energy can be harvested from the trip unit when the circuit breaker is on. The induced current I_2 or voltage can be used to power the control module 106 while the circuit breaker is on and / or can be stored and used when the circuit breaker is off. In this way, an additional power supply can be provided which is partially independent to the supply and which can power a control module 106 to allow wireless communication even when no power is supplied to the circuit breaker. An example implementation of the circuit breaker of Figure 1, which utilises the trip unit 120 and energy harvesting mechanism 104 described in Figure 5, is now discussed in more detail with reference to Figure 6. An example circuit breaker 100 is shown in Figure 6. The circuit breaker 100 comprises a trip unit 102 configured to open the circuit breaker when the current exceeds a threshold current. The trip unit 102 comprises the solenoid 231, core 230 and armature 232 shown in Figure 5. The energy harvester 104 comprises the coil winding 536 disposed around at least part of the solenoid 231 of the trip unit 102. A current line 118 is defined through the circuit breaker (the current line within the circuit breaker is not shown) such that a current I flows through the trip unit 102. In this example, the circuit breaker further comprises an AC to DC converter 630 electrically connected to the coil winding 536. Any suitable AC to DC converter can be used, including but not limited to any combination of AC to DC rectifier(s). Storage means 110 are also provided to store the energy harvested by the energy harvester 104. In this example, the AC to DC converter 630 is coupled between the coil winding 236 and the storage means 110. Any suitable storage means can be used, including but not limited to electrochemical storage (such as a battery), electrical (such as a capacitor or supercapacitor), and / or mechanical (such as a spring). The use of storage means 110 allows the control module 106 of the circuit breaker to be operated even when there is no power from the supply side along current line 118. The circuit breaker 100 further comprises a control module 106 as discussed above. The control module is powered by the energy harvester. The control module can be powered directly from the energy harvester, for example, it can have its own internal battery or energy storage means to store the harvested energy and allow for operation of the control module when the circuit breaker is off. This arrangement is shown in Figure 6, where the control module 106 is shown as being electrically coupled to the energy harvester 104 via the AC to DC converter 630. In other examples (not illustrated here), the control module can be electrically coupled to the energy storage means 110. In this example, the control module 106 may draw power from the energy harvester 104 at any time while a current flows through the circuit breaker 100. The control module 106 may, therefore, be continually powered while the circuit breaker 100 is closed. Alternatively, the control module 106 may be configured only to draw power from the energy harvester 104 under certain conditions, such as when a switching operation occurs. Although specific examples of the energy harvester and trip unit are described herein with reference to Figures 2 and 3, it will be understood that any suitable mechanisms can be used within the circuit breaker of Figure 1. For example, the trip unit may comprise a thermal element (such as a bimetallic strip) instead of or as well as a magnetic element, and the energy harvester may utilise the thermoelectric effect and / or the piezoelectric effect to harvest energy from the thermal element. In other examples, the piezoelectric effect may be used to harvest energy from any moving components of the trip unit 102. Alternatively, other arrangements may be provided which use electromagnetic principles. For example, the trip unit may cause a permanent magnet to rotate in an external magnetic field, thereby inducing a current in a conductor which is arranged within the external magnetic field. In some examples, the coil winding 536 is formed of an amorphous magnetic material. The amorphous magnetic material may be formed by quenching of a molten metal to prevent formation of a crystalline structure. In these examples, it is particularly advantageous that the coil winding 536 is disposed inside the winding of the solenoid 231, outside of the solenoid coil or parallel to the solenoid coil. When the coil winding 536 is disposed inside the solenoid 231, the coil winding 536 Is disposed between the solenoid 231 and the core 230. The use of an amorphous magnetic material provides an energy harvester having a smaller footprint in comparison to a similar arrangement using a coil winding 536 formed of a conventional conducting wire. In particular, the number of turns of the coil winding 536 can be reduced In comparison to conventional materials. The amorphous magnetic material provides a good magnetization effect, which achieves a greater power output. The coil winding 536 may be shaped to have coils with a rectangular, circular or half-circular shape In order to achieve a compact design. With reference to Figure 7, a method of using or operating a single-pole circuit breaker 100 as described herein Is provided. At operation S10, the method comprises harvesting energy from the single-pole circuit breaker when the single-pole circuit breaker in operation. Energy may be harvested during a switching operation of the circuit breaker 100, such as the switching on of the circuit breaker 100 by a user providing a mechanical input to an engagement knob 210, as described with reference to Figures 2a to 4. Energy may also be harvested from a current flowing through the circuit breaker, as described with reference to Figures 5 and 6, or via any other energy harvesting mechanism. At operation S20, the method comprises providing the harvested energy to a control module 106. As described above, the energy may be provided directly to the control module 106 from the energy harvester 104, or the energy may be provided to a storage 110 that can be used to power the control module. As operation S30, the method comprises sending, from the control module 106 to an external device 114, data relating to the operation of the single-pole circuit breaker to an external device via a wireless communication. The data may comprise comprises one or more of: an indication that a short circuit condition has occurred; an indication that an overload condition has occurred; a number of times that a short circuit condition has occurred; a number of times that an overload condition has occurred; the amount of time that the single-pole circuit breaker has spent connected to a load; the magnitude of current during a short circuit condition or overload condition; and the number of switching operations that the single-pole circuit breaker has performed. In examples of the disclosure in which a coil winding 536 is coupled to the solenoid 231 of the trip unit 102, the control module 106 may be configured to infer information relating to the operation of the circuit breaker 100 from measurements taken on the coil winding 536. In these examples, the control module 106 comprises means for measuring the voltage between ends of the coil winding 536. The coil winding 536 is magnetically coupled to the solenoid 231. An AC current / in the solenoid 231 generates a voltage between the ends of the coil winding 536 that is related to the AC current I. The control module 106 is configured to infer the current I in the solenoid based on the magnitude of the voltage induced in the coil 536. The control module 106 may classify a current I in the solenoid 231 based on the induced voltage measured in the coil winding 536. The classification of the current! may be performed in accordance with a pre-defined time-current curve. The predefined time current curve may be defined in accordance with a standard, such as IEC 60898-1. Where the control module 106 determines that the current I in the solenoid 231 (or the voltage cross the coil winding 536) has increased above a first threshold value within a second threshold time duration, the control module 106 determines that a short circuit event has occurred. The control module 106 increments a counter of short circuit events and the circuit breaker trips. When the short circuit conditions are not detected but the control module 106 determines that the current I in the solenoid 231 (or the voltage cross the coil winding 536) has increased above a third threshold value within a fourth threshold time duration (wherein the third threshold value is lower than the first threshold value and the fourth threshold duration time duration is greater than the second threshold time duration), the control module 106 determines that an overload current has occurred. The control module 106 then increments an overload current counter. When the control module 106 detects a current I in the solenoid 231 that is not classified as a short circuit condition or an overload condition according to a pre-defined time-current curve, the control module 106 may calculate a time spent on the load. The first threshold may be between 5 to 10 times the rated current of the circuit breaker. The second threshold may be 100ms. The third threshold may be between 1.45 to 2.45 times the rated current increase. The fourth threshold may be between 1 seconds and 5 seconds. Different thresholds can be used based on the desired tripping characteristics and use application of the circuit breaker. The values of the first to fourth thresholds may be adjustable to achieve suitable performance characteristics. The control module 106 may provide data to the external device 114 via a wireless communication including one or more of: the count of short circuit events, the count of overload events, the time spent on load, the number of switching events, the current switching status (i.e. on or off), the magnitude of a current during an overload, and the magnitude of a current during a short circuit event. The control module 106 may have access to pre-stored data defining characteristics of the circuit breaker and the coil winding. For example, the control module 106 may be able to access pre-stored data values relating to one or more of: the current rating of the circuit breaker, the number of coils in the solenoid, the diameter of the coils of the solenoid, the number of coils in the coil winding, the diameter of the coils of the coil winding, the inductance of the coil winding, the inductance of the solenoid, physical constants (such as the permeability of free space), material properties of the trip unit (such as the permeability of the core), and information regarding time-current curves for different current ratings. The control module 106 may calculate a relationship between a measured voltage in the coil winding 536 and the current I in the circuit breaker based on the pre-stored values. The control module may also determine a suitable time-current curve for classification based on the pre-stored current rating of the circuit breaker. In particular, the control module 106 may determine a constant of proportionality between the measured voltage in the coil winding 536 and the current I in the circuit breaker. The above described process for deriving information regarding the operation of the circuit breaker can be achieved in a single-pole circuit breaker without a neutral line based on measurements of current derived from direct measurements of a voltage in a coil winding 536 coupled to a solenoid of a main current path. Though the above disclosure describes embodiments in which the energy harvester 104 comprises a dielectric elastomer element 220 and a coil winding 536 separately, these energy harvesting means could be combined in a single device. For example, energy harvested from a coil winding 536 could be used to power a control module 106 while current is flowing in the circuit breaker, while energy harvested from a dielectric elastomer element 220 could be used to power the control module after tripping of the circuit breaker. By providing an energy harvesting mechanism within the circuit breaker as described 5 above, which is not directly connected to the power supply to the circuit breaker, sufficient power can be provided to the control module 106 to provide wireless communications with an external device 114. The information provided to the external device may allow maintenance and prognostic evaluation of the circuit breaker to be performed. 10

Claims

1. A single-pole circuit breaker (100) configured to conduct a current (I) while the single-pole circuit breaker is closed, the single-pole circuit breaker comprising:a trip unit (102) configured to open the single-pole circuit breaker when the current exceeds a threshold current;an energy harvester (104) configured to harvest energy during operation of the single-pole circuit breaker; anda control module (106) powered by the energy harvester, wherein the control module is configured to send data relating to the operation of the single-pole circuit breaker to an external device via a wireless communication.

2. The single-pole circuit breaker of claim 1, wherein the energy harvester is configured to harvest energy during one or more of: a switching on operation, a switching off operation, or continuous current supply when connected to a load.

3. The single-pole circuit breaker of claim 1 or claim 2, further comprising storage means (110) configured to store the harvested energy, wherein the control module is powered from the storage means.

4. The single-pole circuit breaker of any preceding claim, wherein the circuit breaker comprises an engagement knob (210) for manual opening and closing of the circuit breaker.

5. The single-pole circuit breaker of claim 4, wherein the energy harvester (104) is configured to harvest mechanical energy input by an external entity to the engagement knob (210),wherein the energy harvester comprises the engagement knob (210) and a dielectric elastomer element (220) coupled to the engagement knob, the energy harvester being configured such that actuation of the engagement knob (210) from an open position to a closed position causes the dielectric elastomer element to be deformed into a stretched state and wherein movement of the engagement knob from the closed position to the open position allows the dielectric elastomer element (220) to return to a relaxed state,wherein the capacitance of the dielectric elastomer element (220) is lower in the relaxed state than the stretched state such that an initial voltage across the dielectric capacitor increases when the single-pole circuit breaker is opened.

6. The single-pole circuit breaker of claim 5, wherein the increased voltage across the dielectric elastomer is used to power on the control module for a period of time after the single-pole circuit breaker is opened, andwherein the control module (106) sends data relating to the operation of the device in a wireless communication to the external device (114) during the period of time that the control module is powered on.

7. The single-pole circuit breaker of claim 5 or claim 6, further comprising a voltage source (131) configured to provide the initial voltage across dielectric elastomer element when the dielectric elastomer element is in the stretched state.

8. The single-pole circuit breaker of any of claim 1 to 4, wherein the trip unit is a magnetic trip unit comprising a magnetic element, and wherein the energy harvester comprises a coil winding (536) disposed around at least part of the magnetic element.

9. The single-pole circuit breaker of claim 8, wherein the coil winding (546) is formed of an amorphous magnetic wire.

10. The single-pole circuit breaker of claim 8 or claim 9, wherein the magnetic element comprises a solenoid through which the current ( / ) flows, and wherein the current (I) in the solenoid induces a second current (I_2) in the coil winding (536) or a voltage between ends of the coll winding (536).

11. The single-pole circuit breaker of claim 10, wherein the coil winding (536) is disposed inside the solenoid (231), outside of the solenoid (231) or parallel to the solenoid.

12. The single-pole circuit breaker of any preceding claim, wherein the data relating to the operation of the single-pole circuit breaker comprises one or more of: an indication that a short circuit condition has occurred; an indication that an overload condition has occurred; a number of times that a short circuit condition has occurred; a number of times that an overload condition has occurred; the amount of time that the single-pole circuit breaker has spent connected to a load; the magnitude of current during a short circuit condition or overload condition; and the number of switching operations that the single-pole circuit breaker has performed.

13. The single-pole circuit breaker of any of claims 8 to 12, wherein the control module (106) is configured to measure a voltage across the coil winding (536), andwherein the control module is configured to calculate a current in the solenoid (231) based on the voltage across the coil winding.

14. The single-pole circuit breaker of claim 13, wherein the control module (106) is configured to increment a short circuit counter when the voltage across the coil winding (536) increases above a first threshold value within a second threshold time duration; andwherein the control module (106) is configured to increment an overload counter when the voltage across the coil winding (536) increases above a third threshold value within a fourth threshold time duration and the short circuit counter is not incremented,wherein the first threshold is greater than the third threshold and the second threshold time duration is less than the fourth threshold time duration, andwherein the data relating to the operation of the single-pole circuit breaker comprises the value of short circuit counter and the value or the overload counter.

15. A method of operating a single-pole circuit breaker, the method comprising: harvesting energy from the single-pole circuit breaker (100) when the singlepole circuit breaker in operation;providing the harvested energy to a control module (106); andsending, from the control module to an external device (114), data relating to the operation of the single-pole circuit breaker to an external device via a wireless communication.

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