CLIAMS:1. An electronic trip unit of a circuit breaker, comprising
a voltage regulator;
a first storage capacitor (C1);
a second capacitor (C2) and a voltage limiter (D5) connected in parallel and in series with the first storage capacitor (C1) in a manner such that when supply current flows to charge said first storage capacitor (C1), limiting voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
2. The trip unit of claim 1, wherein the unit is operatively coupled with a load and a power source.
3. The trip unit of claim 1, wherein the unit further comprises a controller, a trip mechanism, and a plurality of sensors, wherein responsive to detecting a fault event, the controller actuates the trip mechanism to disconnect a load from power source by activating a switch.
4. The trip unit of claim 3, wherein the trip mechanism is actuated by sending current through an actuator coil, wherein the current is sent through the coil by discharging energy in the first storage capacitor.
5. The trip unit of claim 1, wherein the trip unit is a self-powered electronic trip unit.
6. The trip unit of claim 1, wherein the trip unit comprises a current transformer and Rogowski coils that are operatively coupled to a rectifier.
7. The trip unit of claim 1, wherein the voltage limiter (D5) is a voltage limiting diode that is reverse mounted parallel to the second capacitor (C2).
8. The trip unit of claim 1, wherein once the current starts flowing, the second capacitor (C2) and the first storage capacitor (C1) start charging such that when the voltage at the terminals of the second capacitor (C2) reaches the limiting voltage, the voltage limiter (D5) holds the voltage at a value equal to the limiting voltage, enabling bus voltage to quickly reach a value equal to the limiting voltage at the start of charging of the first storage capacitor (C1).
9. The trip unit of claim 1, wherein the voltage limiter presents the limiting voltage that is greater than or equal to the nominal supply voltage of a controller to enable the controller to operate as soon as the second capacitor (C2) starts charging such that when circuit breaker is powered on, the controller is powered on with a shorter delay.
10. A circuit breaker comprising an electronic trip unit, the electronic trip unit comprising
a voltage regulator;
a first storage capacitor (C1);
a second capacitor (C2) and a voltage limiter (D5) connected in parallel and in series with the first storage capacitor (C1) in a manner such that when supply current flows to charge said first storage capacitor (C1), voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
,TagSPECI:TECHNICAL FIELD
[0001] The present disclosure generally relates to the field of circuit breaker. In particular, the present disclosure pertains to fast powering electronic trip unit associated with a self-powered circuit breaker.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art
[0003] The circuit-interrupting technique/ mechanism is an integral part of any electrical circuit of today that has evolved over the time and provides safety to electrical circuit from any fault. Present day compact circuit breakers encompass current protective devices or trip units, that function in response to any fault or abnormal circuit behavior such as over currents, ground fault currents, and short circuits that can occur in an electrical distribution system. A typical Circuit Breaker include an electronic trip unit, which has various blocks such as power supply, signal sensing, signal conditioning, data processing, memory management, user interface, data communication, configuration switches for setting the adjustment parameters of the trip unit and tripping mechanism.
[0004] An electronic protection device can protect a load from fault events by monitoring the current drawn by the load and disconnecting the load from its power source upon detecting a fault event. In some cases, the electronic protection device of present day can also be self-powered, that is, the device can be powered from the same current that the device monitors. Self-powered electronic protection devices are conventionally powered from a rectified secondary winding of a current transformer (CT), with the monitored current sent through a primary winding of the CT.
[0005] The conventional current sensing systems for electronic trip units employ a pair of current transformer and Rogowski coil in each phase (and in the neutral, if a neutral is used). The current transformer outputs are applied to respective full-wave bridge rectifiers for self powering the trip circuit. The rectified output of each line is then filtered by storage capacitor and Rogowski outputs are applied to signal conditioning circuits for current measurement. A signal related to the measured root mean square (RMS) current is then applied to the trip circuit which causes circuit breaker to trip when the measured current of a given magnitude exists for more than a given time threshold.
[0006] Trip units for circuit breakers are used to automatically operate the circuit breaker under fault current conditions. The time required for the circuit breaker to open will depend on the fault current magnitude and nature. In general the ground fault current magnitudes depend on the grounding method used in the circuit. Solidly and low impedance grounded systems may have high levels of ground fault currents. These high levels typically require line tripping to remove the fault from the system, which can be easily achieved. However, high-impedance ground fault tripping is critical in self-powered protection devices because the time taken to trip this fault at the instant of closing the breaker depends on the storage capacitor voltage. At lower currents, the storage capacitor takes more time to charge and hence may delay the tripping in case of fault current.
[0007] Hence, there is a need for an inexpensive solution for fast tripping of the circuit breaker during low current ground fault condition at the instant of closing the breaker or fast powering the tripping unit of circuit breaker.
[0008] Further, as soon as the circuit breaker is closed for the trip unit with microcontroller to be able to function properly, it is necessary to wait for a short but significant start-up time, in which the electrical and electronic parts are subject to a transient that brings them up to steady-state conditions. Once this time has elapsed, the trip unit is able to perform the normal functions of protection and to control opening of the circuit by the circuit-breaker. So, one of the important performance parameters for any tripping units is the start up time Tst of the trip unit. The start-up time Tst of tripping unit depends upon different factors such as power-supply start-up time (Tps) of the supply device of the trip unit, the supply device having as input the stretch of electrical network protected by the circuit-breaker and as output a supply adequate for the characteristics of the trip unit. Another factor on which start-up time Tst of tripping unit depends includes the time of stabilization of the hardware components of the trip unit (Thw) necessary for operation of the microcontroller (for example, the oscillator), and time of initialization of the software (Tsw) present in the microcontroller. The other factor on which start-up time Tst of tripping unit depends can also be the time for calculating the currents (Tc), i.e., the time necessary for processing the signal coming from the current sensors in a form which is useful for generating the signal for actuation of the protections. Hence the start up time Tst of tripping unit can be function of Tst=f(Tps, Thw, Tsw, Tc). For example the the start up time Tst of tripping unit can be Tst=Tps+Thw+Tsw+Tc.
[0009] A circuit breaker will not be able to trip down the circuit for any fault during start up time, which is required to bring the circuit breaker in normal working condition and hence any failure or fault that may occur in the part of the system protected by the circuit-breaker during this time Tst cannot be adequately interpreted by the trip unit.
[0010] In the known art, progressively more rapid systems and components have been studied and introduced, capable of reducing the time Tst to values in the region of few mill second like 5 ms. The state of the art solutions for reduction of Tst is not insufficient and will hence the existing circuit breakers may not work properly in the case of instantaneous short circuits. In the case of instantaneous short circuits, fast tripping is desirable in the region of 2 ms.
[0011] There arises a problem that the detection delay of approx 1.4 ms causes an increase in the interrupting current at a time of interruption and the passing energy due to the interrupting current in an instantaneous tripping operation when a short circuit happens in the turn-on mode of a circuit breaker, which disadvantageously affects the interruption performance of the circuit breaker.
[0012] FIG. 3 is an example showing relation of the interrupting currents when the operation delay of 1.4 ms happens in the over current detection with the estimated short-circuit current Ip defined as 30 kA. The short-circuit current is 17 kA in the case of a 2 ms operating time without the 1.4 ms delay from the short-circuit current starting up to the interruption after an over current is detected, while the short circuit current is 26 kA in the case of a 3.4 ms operating time with the 1.4 ms delay. The difference there between is about 9 kA.
[0013] FIG. 2 is a block diagram of an existing trip circuit 200 for a self-powered electronic protection device. The circuit 200 can include a rectifier 202 that is configured as a diode bridge rectifier for rectifying AC current from the CT secondary winding. The rectifier 202 includes four rectifying diodes D1, D2, D3, and D4. The first output of the CT secondary winding is connected to the anode of the first rectifying diode D1 and the cathode of the fourth rectifying diode D4. The second output of the CT secondary winding is connected to the anode of the second rectifying diode D2 and the cathode of the third rectifying diode D3. The cathodes of the first rectifying diode D1 and the second rectifying diode D2 are both connected to the DC bus line 204, and the anodes of the third rectifying diode D3 and the fourth rectifying diode D4 are both connected to the common ground. The rectifier 202 provides a DC power source from the CT secondary winding to the trip mechanism circuit, and Regulators 1 and 2 (206-1 and 206-2). The DC bus voltage 202 is built by charging the storage capacitors C1. Control logic will get command 208 from controller 210 for changing the power supply configuration. The Regulator 1/2 206 can be used for stepping down the bus voltage 204 to lower voltage 212 for the controller 210 section, communication section and display section. Rogowski sensor 214 output is connected to the controller 210 via signal conditioning circuit 216. External crystal 218 is used for supplying clock to the controller 210. In existing trip devices such as shown in FIG. 3, the voltage regulator 1/2 206 is designed to supply a voltage 212 to the controller 210 that is generally supplied by the bus voltage 204 at the terminals of the storage capacitor C1. In these trip devices, the storage capacitor C1 is generally charged by means of the secondary current coming from the current sensors. One problem of such trip devices is that the charging time of the storage capacitor C1 designed to supply electric power to the actuator is generally long. The rise time of the electronic processing unit supply voltage 212, which depends on the voltage 204 at the terminals of the storage capacitor C1, is therefore also long. For the electronic processing unit 210 to operate normally, the bus voltage 204 at the terminals of the storage capacitor C1 must be higher than the nominal value of the electronic processing unit supply voltage 212. Thus, when the circuit breaker is powered on, the storage capacitor C1 charge tends to delay power-on of the electronic processing unit of the trip device.
[0014] Therefore, there exists a need of an electronic trip device of circuit breaker equipped having a means to reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker, to ameliorate the performance during short circuit and ground fault conditions.
[0015] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0016] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0017] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0018] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0019] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
[0020] An object of the present disclosure is to provide a fast powering electronic trip unit associated with a circuit breaker.
[0021] Another object of the present disclosure is to provide a circuit breaker that ensures that the electronic processing unit of the circuit breaker is powered-on as soon as possible when the circuit breaker is powered-on.
[0022] Another object of the present disclosure is to provide fast tripping during short circuit fault condition at the instant of closing the breaker.
[0023] Another object of the present disclosure is to provide fast tripping during low current ground fault condition at the instant of closing the breaker.

SUMMARY
[0024] Aspects of the present disclosure relate to a self powered electronic trip unit of a circuit breaker that enables fast tripping and fast powering in case of tripping condition so as to the reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions such as short circuit fault and low current ground fault at the instant of closing the breaker, to ameliorate the performance during short circuit and ground fault conditions.
[0025] According to one embodiment, the present disclosure relates to an electronic trip unit of a circuit breaker that includes a voltage regulator, a first storage capacitor (C1), and a second capacitor (C2) and a voltage limiter (D5) that are connected in parallel with each other, and in series with the first storage capacitor (C1), in a manner such that when supply current flows to charge said first storage capacitor (C1), voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
[0026] According to one embodiment, the proposed trip unit can be operatively coupled with a load and a power source, wherein the unit further comprises a controller, a trip mechanism, and a plurality of sensors, wherein responsive to detecting a fault event, the controller actuates the trip mechanism to disconnect a load from the power source by activating a switch.
[0027] In another aspect, the trip mechanism can be actuated by sending current through an actuator coil, wherein the current can be sent through the coil by discharging energy in the first storage capacitor. In yet another aspect, the trip unit is a self-powered electronic trip unit and can include a current transformer (CT) and Rogowski coils that can be operatively coupled to a rectifier. In another aspect, the voltage limiter (D5) is a voltage limiting diode that is reverse mounted parallel to the second capacitor (C2), wherein once the current starts flowing, the second capacitor (C2) and the first storage capacitor (C1) start charging such that when the voltage at the terminals of the second capacitor (C2) reaches the limiting voltage, the voltage limiter (D5) holds the voltage at a value equal to the limiting voltage, enabling bus voltage to quickly reach a value equal to the limiting voltage at the start of charging of the first storage capacitor (C1).
[0028] According to one embodiment, the voltage limiter can present the limiting voltage that is greater than or equal to the nominal supply voltage of a controller to enable the controller to operate as soon as the second capacitor (C2) starts charging such that when circuit breaker is powered on, the controller is powered on with a shorter delay.
[0029] In an aspect, the present disclosure relates to a circuit breaker having an electronic trip unit, wherein the electronic trip unit includes a voltage regulator, a first storage capacitor (C1), and a second capacitor (C2) and a voltage limiter (D5) connected in parallel and in series with the first storage capacitor (C1) in a manner such that when supply current flows to charge said first storage capacitor (C1), voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
[0030] In yet another aspect, the present disclosure relates to a self powered electronic trip unit of a circuit breaker that can include a current transformer (CT) and Rogowski coils configured to self power the electronic trip unit and provide sample current values through a signal condition circuit to a controller, a rectifier circuit configured to rectify alternating current received from the CT to provide a direct current (DC) values to power other components of self-powered electronic trip unit, a first storage capacitor connected with the terminal of rectifier circuit and configured to drive a tripping mechanism, a voltage raising means for raising DC voltage comprising a second storage capacitor and a voltage limiter connected in parallel with the first storage capacitor, wherein the controller can be configured to receive current values from the signal conditioning circuit, compare with predefined threshold values to detect a fault condition, and issue a tripping command to a tripping mechanism in case of fault condition, and wherein the tripping mechanism can be configured to receive the tripping command from the controller to disconnect protected load from power source, wherein the trip mechanism can be actuated by discharging energy stored in the first storage capacitor.
[0031] In an embodiment, the voltage raising means can be connected in series with the first storage capacitor and can be configured to provide raised DC power to other components of the self powered electronic trip unit during the start up time. In an embodiment, the voltage raising means can be connected with the first storage capacitor in such a way that, when the supply current flows to charge the first storage capacitor, a voltage equal to the sum of voltage at the terminals of first storage capacitor and the voltage at the terminals of voltage limiter will be built up.
[0032] The self powered electronic trip unit of circuit breaker can further include a switch that can be configured to regulate the DC bus voltage on instruction of the controller that periodically issues a switch signal to close and open the switch so as to provide desired DC bus voltage to drive the electronic tripping unit.
[0033] The self powered electronic trip unit can further include one or more regulators that are configured to step down the DC voltage supplied by the rectifier circuit to lower the voltage for the controller.
[0034] In an embodiment, the rectifier circuit can be configured to rectify AC current received from CT secondary winding, wherein DC powered part of the circuit may include one or a combination of a regulator, a tripping mechanism unit, a control logic unit, and a controller.
[0035] In an embodiment, the current transformer (CT) and Rogowski coils self power the electronic trip unit, wherein the current carried by a first conductive line connecting power source to load can be configured to flow through a primary winding of the CT and Rogowski coils such that the current in the CT and Rogowski secondary windings is proportional to the current flowing through the first conductive line.
[0036] In an embodiment, the voltage limiter can be implemented by a reverse-mounted voltage limiting diode that can be connected in parallel with the second capacitor so that when the first storage capacitor is charged, the DC voltage supplied to other part of the circuit quickly reaches to a value equal to the sum of the voltage at the terminals of the first storage capacitor and of the limiting voltage of said voltage limiting diode. As soon as the current starts flowing, first storage capacitor and the second capacitor start charging simultaneously. When the voltage at the terminals of the second capacitor reaches the limiting voltage, the voltage-limiting diode holds this voltage at a value equal to said limiting voltage so that the voltage quickly reaches a value equal to the limiting voltage at the beginning of charging of the first storage capacitor. The voltage-limiting diode can advantageously present a limiting voltage that is greater than or equal to the nominal supply voltage of the controller that enables the controller to operate as soon as the second capacitor starts charging. In this way, when the circuit breaker is powered on, the controller can be powered-on with a shorter delay.
[0037] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components

BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0039] FIG. 1 illustrates an exemplary block diagram of an electronic protection device.
[0040] FIG. 2 illustrates an exemplary block diagram of an existing trip circuit.
[0041] Fig. 3 illustrates an exemplary waveform diagram showing a relation of interrupting current values when an operation start delay happens in an over current detecting circuit.
[0042] FIG. 4 illustrates an exemplary block diagram of a proposed trip circuit in accordance with an embodiment of the present disclosure.
[0043] FIG. 5 illustrates an exemplary graph showing advantage of proposed trip unit over existing trip unit at start-up condition

DETAILED DESCRIPTION
[0044] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0045] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0046] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0047] All components of electronic tripping unit described herein can be arranged in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0048] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0049] Aspects of the present disclosure relate to a self powered electronic trip unit of a circuit breaker that enables fast tripping and fast powering in case of tripping condition so as to the reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions such as short circuit fault and low current ground fault at the instant of closing the breaker, to ameliorate the performance during short circuit and ground fault conditions.
[0050] According to one embodiment, the present disclosure relates to an electronic trip unit of a circuit breaker that includes a voltage regulator, a first storage capacitor (C1), and a second capacitor (C2) and a voltage limiter (D5) that are connected in parallel with each other, and in series with the first storage capacitor (C1), in a manner such that when supply current flows to charge said first storage capacitor (C1), voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
[0051] According to one embodiment, the proposed trip unit can be operatively coupled with a load and a power source, wherein the unit further comprises a controller, a trip mechanism, and a plurality of sensors, wherein responsive to detecting a fault event, the controller actuates the trip mechanism to disconnect a load from the power source by activating a switch.
[0052] In another aspect, the trip mechanism can be actuated by sending current through an actuator coil, wherein the current can be sent through the coil by discharging energy in the first storage capacitor. In yet another aspect, the trip unit is a self-powered electronic trip unit and can include a current transformer (CT) and Rogowski coils that can be operatively coupled to a rectifier. In another aspect, the voltage limiter (D5) is a voltage limiting diode that is reverse mounted parallel to the second capacitor (C2), wherein once the current starts flowing, the second capacitor (C2) and the first storage capacitor (C1) start charging such that when the voltage at the terminals of the second capacitor (C2) reaches the limiting voltage, the voltage limiter (D5) holds the voltage at a value equal to the limiting voltage, enabling bus voltage to quickly reach a value equal to the limiting voltage at the start of charging of the first storage capacitor (C1).
[0053] According to one embodiment, the voltage limiter can present the limiting voltage that is greater than or equal to the nominal supply voltage of a controller to enable the controller to operate as soon as the second capacitor (C2) starts charging such that when circuit breaker is powered on, the controller is powered on with a shorter delay.
[0054] In an aspect, the present disclosure relates to a circuit breaker having an electronic trip unit, wherein the electronic trip unit includes a voltage regulator, a first storage capacitor (C1), and a second capacitor (C2) and a voltage limiter (D5) connected in parallel and in series with the first storage capacitor (C1) in a manner such that when supply current flows to charge said first storage capacitor (C1), limiting voltage equal to sum of voltage at terminals of said first storage capacitor (C1) and of voltage at terminals of the voltage limiter (D5) is built, wherein the limiting voltage of greater than or equal to a nominal supply voltage of the controller required by the voltage regulator for starting a controller of the trip unit is achieved before the first storage capacitor charges to the voltage value required by the regulator to enable fast tripping.
[0055] Different embodiments of the present disclosure relates to a self powered electronic trip unit of circuit breaker that enables fast tripping and fast powering in case of tripping condition so as reduce the reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker, to ameliorate the performance during short circuit and ground fault conditions.
[0056] The self powered electronic trip unit of circuit breaker includes a current transformer (CT) and Rogowski coils that are configured to self power the electronic trip unit and provide sample current values through a signal condition circuit to a controller. The trip unit can further include a rectifier circuit configured to rectify alternating current received from the CT to provide direct current (DC) values to power other components of self-powered electronic trip unit. The trip unit can further include a first storage capacitor that is connected with the terminal of rectifier circuit and is configured to drive a tripping mechanism. The trip unit can further include a voltage raising means for raising DC voltage having a second capacitor and a voltage limiter that is connected to the second capacitor in parallel, and in series with the first storage capacitor. In an aspect, the controller can be configured to receive current values from the signal conditioning circuit, compare with predefined threshold values to detect a fault condition, and issue a tripping command to tripping mechanism in case of fault condition, and a tripping mechanism configured to receive the tripping command from the controller to disconnect protected load from the power source, wherein the trip mechanism can be actuated by discharging energy stored in the first storage capacitor.
[0057] In an embodiment, the voltage raising means can be connected in series with the first storage capacitor and can be configured to provide raised DC power to the other components of self powered electronic trip unit during the start up time. In an embodiment, the voltage raising mean can be connected with the first storage capacitor in such a way that when the supply current flows to charge the first storage capacitor, a voltage equal to the sum of voltage at the terminals of first storage capacitor and the voltage at the terminals of voltage limiter is built up.
[0058] The self powered electronic trip unit of circuit breaker can further include a switch configured to regulate the DC bus voltage on instruction of the controller that periodically issue a switch signal to close and open the switch so as to provide desired DC bus voltage to drive the electronic tripping unit.
[0059] The self powered electronic trip unit can further include one or more regulators that can be configured to step down the DC voltage supplied by the rectifier circuit to lower voltage for the controller.
[0060] In an embodiment, the rectifier circuit can be configured to rectify AC current received from CT secondary winding. The DC powered part of the circuit may include one or a combination of a regulator, a tripping mechanism unit, a control logic unit, and a controller.
[0061] In an embodiment, the current transformer (CT) and Rogowski coils can self power the electronic trip unit, wherein the current carried by a first conductive line connecting power source to load can be configured to flow through a primary winding of the CT and Rogowski coils such that the current in the CT and Rogowski secondary windings are proportional to the current flowing through the first conductive line.
[0062] In an embodiment, the voltage limiter can be implemented by a reverse-mounted voltage limiting diode and can be connected in parallel with the second capacitor so that when the first storage capacitor is charged, the DC voltage supplied to other parts of the circuit quickly reaches to a value equal to the sum of the voltage at the terminals of the first storage capacitor and of the limiting voltage of said voltage limiting diode. As soon as the current starts flowing, first storage capacitor and second capacitor starts charging simultaneously. When the voltage at the terminals of the second capacitor reaches the limiting voltage, the voltage-limiting diode holds this voltage at a value equal to the limiting voltage so that the voltage quickly reaches a value equal to the limiting voltage at the beginning of charging of the first storage capacitor. The voltage-limiting diode can advantageously present a limiting voltage greater than or equal to the nominal supply voltage of the controller that enables the controller to operate as soon as the second capacitor starts charging. In this way, when the circuit breaker is powered on, the controller can be powered-on with a shorter delay.
[0063] The present disclosure therefore provides an electronic trip device and a circuit breaker that is equipped with such a trip device, a means to reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions such as short circuit fault and low current ground fault at the instant of closing the breaker to ameliorate performance during short circuit and ground fault conditions.
[0064] In an embodiment, the present disclosure provides an electronic trip unit, which employs, as major components, a power supply, a signal conditioning circuit for each line, data processing, data communication, memory management, user interface, and configuration switches for setting the adjustment parameters of the trip unit. The circuit is applicable to both three and four wire systems. Opening of the circuit breaker can be accomplished by a conventional mechanical mechanism, which is activated by an electromagnetic latching mechanism triggered by the electronic trip unit. In an aspect, the power supply section can include output from current transformer, bridge rectifier, and voltage regulator section for microcontroller, communication section, and display section. As mentioned previously, there is a need for fast tripping of the circuit breaker during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker, here incorporated a hardware configuration. According to one embodiment, the hardware configuration can include a parallel connected capacitor and voltage limiter connected in series with the storage capacitor in such a way that when the supply current flows to charge the storage capacitor, voltage equal to the sum of the voltage at the terminals of the storage capacitor and of the voltage at the terminals of the voltage limiter will be built up. The limiting voltage can be greater than or equal to a nominal value of the supply voltage of the electronic processing unit. In this method, the voltage required by the regulator for starting the controller can be achieved before the storage capacitor charges to the voltage value required by the regulator. In this way, the power supply start-up time can be reduced and hence fast tripping can be achieved during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker.
[0065] In an aspect, as soon as the circuit breaker is closed, for the trip unit to be able to function properly, it is necessary to wait a short but significant start-up time, in which the electrical and electronic parts are subject to a transient that brings them up to steady-state conditions. Once this time has elapsed, the trip unit is able to perform normal functions of protection and to control opening of the circuit by the circuit-breaker. In the case of instantaneous short circuits, tripping is desirable in times in the region of 2 ms.
[0066] High-impedance ground fault tripping is critical in self powered protection devices because the time taken to trip this fault at the instant of closing the breaker depends on the storage capacitor voltage. At lower currents the storage capacitor takes more time to charge and hence delayed tripping of the fault. Hence, the present disclosure provides an electronic trip device and a circuit breaker equipped with such a trip device, a means to reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker.
[0067] FIG. 1 illustrates an exemplary block diagram 100 of a fast powering electronic trip unit design in accordance to an embodiment of the present disclosure. As shown in the FIG. 1, an electronic tripping unit 128 may be connected between a power source 102 and a protected load 106 to provide quick tripping by switching one or more power lines such as power lines 118, 120, 122 with the help of a switch 104. In an example implementation, the power source 102 can be a polyphone alternating current (AC) power source, which can include three conductive lines such as power lines 118-122 for providing three phases of a supply current, and can be arranged in a delta or wye configuration. In an example implementation, while the power source 102 is illustrated as having three conductors carrying three phases of a supply current, it is possible that in different implementations, polyphase power sources with supply currents having more than three or less than three phases, such as a single phase power source can be used.
[0068] In an example configuration, the protected load 106 can be an inductive motor load or any other electric load that needs to be protected in case of fault current condition. The electronic tripping unit 128, also referred interchangeably as electronic protection device 128 can include a first sensor-1 108, a second sensor-2 110, a third sensor-3 112, a controller 114, and a trip mechanism 116. In an example implementation, the controller 114 can receive the outputs of the three sensors 108-112, compare with a predefined threshold, detect fault condition, and issue a tripping single to trip mechanism 116. The controller 114 can be connected to the trip mechanism 116 and can be configured to actuate the trip mechanism 116 in case a fault condition is detected by the controller. The trip mechanism 116 on receiving the tripping signal from controller 114 can actuate the switch 104, which can disconnect the protected load 106 from the power source 102.
[0069] In an example implementation, the trip mechanism 116 can be actuated by sending current through an actuator coil. The current can be sent through the actuator coil by discharging energy in the storage capacitors by biasing a transistor to complete a circuit including the energy storage and the actuator coil. The actuator coil can be a portion of a solenoid, and the mechanical movement due to actuation of the solenoid can cause a mechanical lever, rod, linkage, or rotating element to open electrical contacts in the trip mechanism 116, either directly or indirectly.
[0070] In an example implementation, the controller 114 can be a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or any another electronic device suitable for receiving signals indicative of an electrical characteristic (e.g., current or voltage) of the power source , comparing with predefined thresholds and detect fault conditions. The controller 114 can analyze the received signals to determine whether a fault condition has occurred, and causes the trip mechanism 116 to actuate by issuing the trip signal 124. The trip mechanism 116 triggers a tripping signal to switch 104 to disconnect the power source 102.
[0071] In an example implementation, the electronic protection device 128 can be self-powered, meaning that electronic components of the electronic protection device 128 can be powered by same current or voltage that the electronic protection device 128 is monitoring. In other words, by self powered, it is meant that the electronic protection device 128 does not have an independent power supply but rather derives its power from the conductive line or lines, such as power line 118, power line 120 or power line 122, that the electronic protection device 128 is monitoring.
[0072] The electronic protection device 128 can be configured to enable fast tripping and provide fast powering of electronic protection device 128 in case of tripping condition so as to reduce the start-up time for fast tripping of the circuit breaker during critical fault conditions like short circuit fault and low current ground fault at the instant of closing the breaker, to ameliorate the performance during short circuit and ground fault conditions.
[0073] With reference to FIGs. 1 and 4, in an aspect, the self-powered electronic protection device 128 includes a current transformer (CT) and Rogowski 402 output. The current carried by the first conductive line 118 can be configured to flow through a primary winding of the CT and Rogowski, such that the current in the CT and Rogowski secondary windings are proportional to the current flowing through the first conductive line 118. The CT secondary winding has a first and second output connected to a rectifier 404. The rectifier 404 rectifies the alternating current from the CT secondary winding to provide a direct current (DC) power source to the remaining electronic components within the self-powered electronic protection device 128.
[0074] In an implementation of the self-powered electronic protection device 128, the switch S3 is used to regulate the DC bus voltage of the trip mechanism circuit. Closing the switch S3 causes DC current to flow back to the anode of the rectifier 404. The controller 114 can be configured to periodically close and open the switch S3 by issuing the switch signal to provide a desired DC bus voltage for the trip mechanism circuit.
[0075] In an aspect, when compared with FIG. 2 of existing trip unit, the proposed electronic trip device represented in FIG. 4 comprises, in addition, a voltage raising means to raise the bus voltage 406 to supply voltage to the regulator ½ 408-1 and 408-2, wherein the voltage raising means being connected between the cathode of the diode 404 and the first storage capacitor C1. In the case represented in FIG. 4, the voltage raising means comprises a second capacitor C2 and a voltage limiting diode D5 reverse-mounted parallel to said second capacitor C2, so that, when the first storage capacitor C1is charged, the bus voltage 406 quickly reaches a value equal to the sum of the voltage at the terminals of the first storage capacitor C1 and of the limiting voltage of said diode D5. As soon as the current starts flowing, second capacitor C2 and first storage capacitor C1 start charging simultaneously. When the voltage at the terminals of the second capacitor C2 reaches the limiting voltage, the voltage-limiting diode D5 holds this voltage at a value equal to said limiting voltage. In this way, the bus voltage 406 quickly reaches a value equal to the limiting voltage, at the beginning of charging of the first storage capacitor C1. The voltage-limiting diode can advantageously present a limiting voltage greater than or equal to the nominal supply voltage 410 of the controller 114, which enables the controller 114 to operate as soon as the second capacitor C2 starts charging. In this way, when the circuit breaker is powered on, the controller 114 is powered-on with a shorter delay. In an aspect, the changing values of the bus voltages 204 and 406, versus time are respectively represented in FIG. 5 during a transient power-on phase of a circuit breaker.
[0076] In an aspect, up to the time t1 of the waveform 406, the supply current flows through the capacitor C2, via the diode 404, to charge the first storage capacitor C1. The bus voltage 406 very quickly reaches a value equal to the limiting voltage of the diode D5, which is in this instance substantially equal to the nominal value of the supply voltage 410 of the controller 114. Thus, at the time t1, the bus voltage 406 has a value substantially equal to the nominal value of the voltage 410. The voltage regulator 1/2 408 is therefore sufficiently supplied to deliver a voltage equal to the nominal value of the voltage 410.
[0077] In another aspect, it can be noted that at the time t1 of the waveform 204, value of the voltage at the terminals of the storage capacitor C1 is significantly lower than the nominal value of the voltage 410 because the voltage regulator 1/2 is directly supplied by the bus voltage 204 at the terminals of the storage capacitor C1, this value of the bus voltage would still not be sufficient to enable the voltage regulator 1/2 to deliver a nominal supply voltage of the controller 114.
[0078] Between the times t1 and t3 of waveform 406, the supply current is used to charge the first storage capacitor C1. The bus voltage 406 is substantially equal to the sum of the voltage at the terminals of the first storage capacitor C1 and of the limiting voltage of the diode D5.
[0079] It should be noted that at the time t2 of the waveform 204, the voltage at the terminals of the storage capacitor C1 is equal to the nominal value of the voltage 410. It is only at this time t2 that this voltage 204 is sufficient to enable the voltage regulator1/2 to deliver a voltage equal to the nominal value of the voltage 410. Thus, in this embodiment, the trip device of the invention enables power-on of the electronic processing unit to be advanced. The gain in time of proposed trip device as shown in FIG.4 compared with existing trip device as shown in FIG. 2 where the voltage regulator 1/2 is directly supplied by the voltage at the terminals of the storage capacitor C1 is t2 - t1.
[0080] At the time t3, the bus voltage 406 reaches the maximum value and the controller 114 regulates this voltage using switch S3. Closing the switch S3 causes diversion of current back to the anode of the rectifier 404, so that no current flows through the storage capacitor C1. The controller 114 can be configured to periodically close and open the switch S3 by issuing the switch signal to provide a desired DC bus voltage 406 for the trip mechanism circuit.
[0081] At the time t4, the controller 114 issues a trip command upon detecting a fault condition and the bus voltage 204 of the circuit shown in FIG. 2 falls to zero because the storage capacitor C1 discharges to actuate the trip mechanism. Whereas the bus voltage 406 of the circuit shown in FIG. 4 maintains the voltage required by the regulator 1/2 for the continuous operation of controller 114. This is achieved because the trip mechanism is connected across the first storage capacitor C1.
[0082] In an aspect, the proposed trip device ensures that the electronic processing unit is powered-on as soon as possible when the circuit breaker is powered-on. Furthermore, faster tripping can be achieved compared to the conventional method during short circuit fault condition at the instant of closing the breaker. Furthermore, faster tripping can be achieved compared to the conventional method during low current ground fault condition at the instant of closing the breaker.
[0083] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0084] The present disclosure provides a fast powering electronic trip unit associated with a circuit breaker.
[0085] The present disclosure provides a circuit breaker that ensures that the electronic processing unit of the circuit breaker is powered-on as soon as possible when the circuit breaker is powered-on
[0086] The present disclosure provides a fast tripping during short circuit fault condition at the instant of closing the breaker.
[0087] The present disclosure provides fast tripping during low current ground fault condition at the instant of closing the breaker.