Claims:1. A system for monitoring connection of current transformer (CT) to an electronic trip unit (ETU) of a circuit breaker (CB), said systemcomprisinga sensing circuit configured to continuously sense signal at controller general input output pin (GPIO) Pin of the CB in a manner such when the CT is improperly connected to the ETU, an indicator connected to the controller GPIO pin changes state to indicate said improper connection.
2. The system of claim 1, wherein said indicator is a light indicator that is turned ON when the connection between the CT and ETU is improper and is kept in OFF state when the connection is proper.
3. The system of claim 1, wherein the CB is an air circuit breaker (ACB).
4. The system of claim 1, wherein the connection is monitored between the CT and release of the ETU.
5. The system of claim 1, wherein the indicator is an audio indicator.
6. The system of claim 1, wherein the CT is Rogowski coil.
7. The system of claim 1, wherein the sensing circuit comprises a first transistor, collector voltage value of which is zero when the CT is connected to the ETU, and in which case, logic low signal is sent to microcontroller of the ETU.
8. The system of claim 7, wherein when the CT disconnects from the ETU, the collector voltage value is 1.5V, and in which case, logic high signal is sent to the microcontroller of the ETU.
9. The system of claim 1, wherein when connection between the CT and the ETU is improper, no current path is provided and the indicator changes the state.
10. A method to monitor connection between a CT and an ETU, said method comprising the steps of:
configuring a sensing circuit to continuously sense signal at controller general input output pin (GPIO) Pin of the CB; and
changing state of an indicator connected to the controller GPIO pin when the CT is improperly connected to the ETU.
, Description:TECHNICAL FIELD
[0001] The present disclosure generally relates to the field ofcurrent transformers (CT). In particular, the present disclosure pertains toassessment of health of CTs.

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] A circuit breaker is an automatically operated electricalswitch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.Modern circuit breakers come with a microprocessor based electronics trip unitthat not only provide overcurrent protection but also provide comprehensive metering and extended protective relaying. Also, these intelligent trip units can communicate all this information to displays at the breaker or at remote locations.
[0004] For providing current protection, microprocessor based releases have to sense the fault by sensing current through CT and/or voltage through Rogowski coil, wherein CT may detect current supplied to a load by circuit breaker (CB) such as air circuit breaker (ACB), while the current detected by the current transformer is converted to a voltage by the Rogowski coil.In Air circuit breakers, the electronics trip unit senses fault current and gives command to flux shift device for opening the contacts of the breakers. All current based protection therefore depends upon the measure value of voltage through Rogowski coil/CT.
[0005] As all protection relies on the base of sensing current, if the CT/Rogowski coil is not properly connected to the release or if there is an inter-winding damage to CT/Rogowskicoil, ETU (Electronic Trip Unit) will detect it as a no fault condition even if there is a Short-Circuit of KA.
[0006] There is therefore a need for systems and methods that enable efficient detection of situations when CT is not connected properly to the release.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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 groups used in the appended claims.

OBJECTS OF THE INVENTION
[0012] An object of the present disclosure is to enable efficient detection of situations when CT is not properly connected to release.
[0013] An object of the present disclosure is to enable efficient detection of situations when CT has an inter-winding damage.
[0014] An object of the present disclosure is to enable efficient detection of situations when Rogowski Coil is not properly connected to release or when the Coil has an inter-winding damage.

SUMMARY
[0015] The present disclosure generally relates to the field of current transformers (CT). In particular, the present disclosure pertains to assessment of health of CTs.
[0016] In an aspect, the present disclosure relates to a system for monitoring connection of current transformer (CT) to an electronic trip unit (ETU) of a circuit breaker (CB), wherein the system includes a sensing circuit configured to continuously sense signal at controller general input output pin (GPIO) Pin of the CB in a manner such when the CT is improperly connected to the ETU, an indicator connected to the controller GPIO pin changes state to indicate said improper connection.
[0017] In an aspect, the indicator can be a light indicator that can be turned ON when the connection between the CT and ETU is improper and is kept in OFF state when the connection is proper. In another aspect, the CB can be an air circuit breaker (ACB). In yet another aspect, the connection can be monitored between the CT and release element of the ETU. In another aspect, the indicator can be an audio indicator.In an aspect, the CT is Rogowski coil.
[0018] In an aspect, the sensing circuit can include a first transistor, collector voltage value of which is zero when the CT is connected to the ETU, and in which case, logic low signal is sent to microcontroller of the ETU. On the other hand, when the CT disconnects from the ETU (or when the connection is not proper), the collector voltage value is 1.5V, and in which case, logic high signal is sent to the microcontroller of the ETU.
[0019] In an aspect, when connection between the CT and the ETU is improper, no current path is provided and the indicator changes the state.
[0020] The present disclosure further relates to a method to monitor connection between a CT and an ETU, said method comprising the steps of: configuring a sensing circuit to continuously sense signal at controller general input output pin (GPIO) Pin of the CB; andchanging state of an indicator connected to the controller GPIO pin when the CT is improperly connected to the ETU.
[0021] 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
[0022] 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.
[0023] FIG.1 illustrates an exemplaryrepresentation of power supply section having a sensing circuit in which aspects of the present disclosure can be implemented.
[0024] FIG. 2 illustratesexemplary constructional details of the proposed sensing/monitoring circuit/unit/module in which aspects of the present disclosure can be implemented.
[0025] FIG. 3 illustrates an exemplary flow diagram showing how improper connection between current transformer (CT) and release/electronic trip unit (ETU) is tested in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS
[0026] 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.
[0027] 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.
[0028] 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.
[0029] The present disclosure generally relates to the field of current transformers (CT). In particular, the present disclosure pertains to assessment of health of CTs.
[0030] In an aspect, the present disclosure relates to a system for monitoring connection of current transformer (CT) to an electronic trip unit (ETU) of a circuit breaker (CB), wherein the system includes a sensing circuit configured to continuously sense signal at controller general input output pin (GPIO) Pin of the CB in a manner such when the CT is improperly connected to the ETU, an indicator connected to the controller GPIO pin changes state to indicate said improper connection.
[0031] In an aspect, the indicator can be a light indicator that can be turned ON when the connection between the CT and ETU is improper and is kept in OFF state when the connection is proper. In another aspect, the CB can be an air circuit breaker (ACB). In yet another aspect, the connection can be monitored between the CT and release element of the ETU. In another aspect, the indicator can be an audio indicator. In an aspect, the CT is Rogowski coil.
[0032] In an aspect, the sensing circuit can include a first transistor, collector voltage value of which is zero when the CT is connected to the ETU, and in which case, logic low signal is sent to microcontroller of the ETU. On the other hand, when the CT disconnects from the ETU (or when the connection is not proper), the collector voltage value is 1.5V, and in which case, logic high signal is sent to the microcontroller of the ETU.
[0033] In an aspect, when connection between the CT and the ETU is improper, no current path is provided and the indicator changes the state.
[0034] The present disclosure further relates to a method to monitor connection between a CT and an ETU, said method comprising the steps of: configuring a sensing circuit to continuously sense signal at controller general input output pin (GPIO) Pin of the CB; andchanging state of an indicator connected to the controller GPIO pin when the CT is improperly connected to the ETU.
[0035] FIG. 1 illustrates an exemplaryrepresentation of power supply section 100 having a sensing circuit 114 in which aspects of the present disclosure can be implemented. As shown, the section 100, also referred to architecture/overall system 100, can include a power supply 100 operatively coupled with release 104, circuit breaker (CB) 112, and flux shift device (FSD) 108. Release 104 in turn can be coupled with an indicator 106 (visual/light or audio based, for instance), a sensing circuit 114, and with current transformer (CT) 102, wherein the sensing circuit 114 can be configured to continuously sense signal at controller general input output pin (GPIO) Pin of the CB in a manner such when the CT 102 is improperly connected to the Release/ETU 104, the indicator 106 connected to the controller GPIO pin changes state to indicate said improper connection.
[0036] In an aspect, the indicator 106 can be a light indicator that can be turned ON when the connection between the CT 102 and ETU/Release 104 is improper and is kept in OFF state when the connection is proper. In another aspect, the CB 112 can be an air circuit breaker (ACB). In yet another aspect, the connection can be monitored between the CT 102 and release element 104 of the ETU. In another aspect, the indicator 106 can be an audio indicator. In an aspect, the CT 102 can be Rogowski coil and various aspects of the present disclosure can be explained with respect to Rogowski coil and its use in air circuit breakers.
[0037] In an aspect, the sensing circuit 114 can include a first transistor (refer to Q1 of FIG. 2), collector voltage value of which is zero when the CT 102 is connected to the ETU, and in which case, logic low signal is sent to microcontroller of the ETU. On the other hand, when the CT 102 disconnects from the ETU (or when the connection is not proper), the collector voltage value is 1.5V, and in which case, logic high signal is sent to the microcontroller of the ETU.
[0038] In an aspect, when connection between the CT 102 and the ETU/Release 104 is improper, no current path is provided and the indicator 106 changes the state (for example LED indicator is turned ON). FIG. 2 illustrates an exemplary implementation of the proposed sensing circuit 114 having first transistor Q1, output of which helps determine/evaluate connection between the CT/Rogowski Coil 202 (in an implementation, same as CT 102 of FIG. 1) and Release/ETU.
[0039] It would be appreciated that ETU is basically a sensor that senses fault level through secondary output voltage of RogowskiCoil, which is equivalent to primary current and compares it with the reference voltage in the look-up table.When micro-proccessorsenses the fault level and finds the measured voltage greater than the look up table voltage, it allows the ETU to clear the fault within the specified time delay. Therefore, in order to detect and clear the fault, Rogowski must be properly connected to the ETU so as to sense it clearly, which is an oject of the present disclosure.
[0040] The present disclosure therefore provides a monitory mechanism (also referred to as a sensing circuit)that continuously senses signal at the controller GPIO pin in circuit breaker ON/OFF condition. In this scenario, in an implementation, micro-processor based ETU must be power-on through Aux supply so as to Power On the controller. Whenever Rogowskiis connected to the release through connector, Controller GPIO pin will change the state and trigger the LED to ON state showing that Rogowski is not connected to the release properly. In addition to that, in an aspect, if winding of Rogowski itself is broken,an alarm and/or an LED/light indicator can be switched ON to indicate the rogowski failure. Indication of rogowski failure can also be displayed on trip unit display.
[0041] In an exemplary implementation, release will be powered –On through 24V DC power supply module which will provide power to the controller.When rogowski is connected to the release, the collector voltage VC of Q1 will be zero & logic low signal to the microcontroller.As soon as the rogowski disconnects from the trip unit the VC at Q1 equals to 1.5V. This 1.5V is the logic high signal to the microcontroller pin.Whenever rogowski coil is not connected, also whenever there is a loose connection of the connector to the release, the current path will not be provided to the system it will trigger the alarm signal.Furthermore, during running condition due to any environmental or electrical factor if Rogowski internal winding gets damage, sensing circuit of the present disclosure can help get the same indicated. Therefore, continuous monitoring of the port pin, for instance in every 20ms,can give the indication of CT continuity to the release.
[0042] The present disclosure therefore enables real-time monitoring of healthiness of CT connectivity to release, and issuance of an alarm signal to capture actual failure of the fault.
[0043] FIG. 3 illustrates an exemplary flow diagram 302 showing how improper connection between current transformer (CT) and release/electronic trip unit (ETU) is tested in accordance with an embodiment of the present disclosure. At step 302, a sensing circuit is used to continuously sense signal at controller general input output pin (GPIO) Pin of the CB. At step 304, it is checked if GPIO Pin status is low such that if the Pin status is low, at step 306, state of an indicator that is connected to the controller GPIO pin is changed to ON to indicate that the CT is improperly connected to the ETU, whereas if the Pin status is high, at step 308, it can be concluded that the CT is properly connected to the ETU and therefore the indicator such as an LED indicator is not turned ON.
[0044] It would be appreciated that state ON/OFF of indicator can be configured to indicate any situation and therefore the same is only implementation oriented and does not limit the scope of the present invention. For instance, indicator can be kept ON when the connection between CT and ETU/release is healthy.
[0045] In an aspect, before activating the sensing circuit, method of the present disclosure can first Power ON the device through Aux Supply and then initialize all configured modules and peripherals, post which a scheduler can be started to execute the defined tasks, one of which is the working of the sensing circuit.
[0046] 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
[0047] The present disclosure enables efficient detection of situations when CT is not properly connected to release.
[0048] The present disclosure enables efficient detection of situations when CT has an inter-winding damage.
[0049] The present disclosure enables efficient detection of situations when Rogowski Coil is not properly connected to release or when the Coil has an inter-winding damage.