CLIAMS:1. A method for detecting fault current comprising the steps of:
receiving from an analog circuit, at a microcontroller of an electronic trip unit of a circuit breaker, sensed peak value of fault current; and
determining, at the microcontroller, if the sensed peak value of fault current is greater than a defined threshold such that when the sensed peak value of fault current is greater than the defined threshold, the microcontroller issues a tripping command to the circuit breaker.

2. The method of claim 1, wherein time taken from detection of peak value of fault current to issuance of the tripping command is within 5 ms.

3. The method of claim 1, wherein the microcontroller receives multiple sensed peak values of fault current from the analog circuit to compare each received sensed peak value with the threshold for reliable and accurate digital trip command.
,TagSPECI:TECHNICAL FIELD
[0001] The present disclosure relates to protection/electrical devices. More particularly, the present disclosure relates to methods for short circuit fault current sensing and tripping through an Electronic Trip Unit (ETU) of a 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] A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow. Intelligence of circuit breakers is in their respective Electronic Trip Units wherein an Electronic Trip Unit is a microprocessor based programmable device that measures and calculates current flowing through the circuit breaker and initiates a trip signal when appropriate. The trip unit senses the current level through current sensors and decides the tripping time of the circuit breaker. A trip unit is a part of a circuit breaker that opens the circuit in the event of over current fault condition such as thermal overload, short circuit, or ground fault.
[0004] Each fault typically has a predefined priority based on its severity, wherein short circuits/instantaneous faults are among the most severe and need to be cleared within few milliseconds. Sensing and fault clearing time for a short circuit fault by an existing standard electronic trip unit of MCCB is equal or more than 20ms with tolerance of 0ms to +20ms. Such time for issuing a trip command includes power up time for circuitry, software boot up time, signal processing time, and time taken for ADC sampling and logic for decision making, which makes it difficult to handle applications where severe short circuit faults needs to be addressed within 5ms with reliable and accurate digital trip commands.
[0005] There is therefore a need in the art for a method/system that reduces the time needed to address an overcurrent fault. There is also a need in the art for a method to achieve fast high fault current trip time in self- power mode at make-on fault condition.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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
[0011] An object of the present disclosure is to provide a method/system that reduces the time needed to address an overcurrent fault.
[0012] Another object of the present disclosure is to provide a method to achieve fast high fault current trip time in self- power mode at make-on fault condition.
[0013] Yet another object of the present disclosure is to provide a method/system that reduces the time needed to address an overcurrent fault within 5ms with tolerance of 0ms to +2ms.
[0014] Another object of the present disclosure is to provide an application where severe short circuit faults need to be addressed within 5ms with reliable and accurate digital trip command.

SUMMARY
[0015] The present disclosure relates protection/electrical devices. More particularly, the present disclosure relates to methods for short circuit fault current sensing and tripping through an Electronic Trip Unit (ETU) of a Circuit Breaker.
[0016] According to one embodiment, method of the present disclosure includes the steps of receiving from an analog circuit, at a microcontroller of an electronic trip unit of a circuit breaker, sensed peak value of fault current; and determining, at the microcontroller, if the sensed peak value of fault current is greater than a defined threshold such that when the sensed peak value of fault current is greater than the defined threshold, the microcontroller issues a tripping command to the circuit breaker.
[0017] In an aspect, the time taken from detection of peak value of fault current to issuance of the tripping command is within 5 ms. In another aspect, the microcontroller receives multiple sensed peak values of fault current from the analog circuit to compare each received sensed peak value with the threshold.
[0018] 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
[0019] 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.
[0020] FIG. 1 illustrates an exemplary block diagram showing fault current and tripping action mechanism in accordance with an embodiment of the present disclosure
[0021] FIG. 2 illustrates an exemplary flow diagram for taking tripping decisions based on peak values of fault current that are detected by the proposed analog circuit in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] The present disclosure relates protection/electrical devices. More particularly, the present disclosure relates to methods for short circuit fault current sensing and tripping through an Electronic Trip Unit (ETU) of a Circuit Breaker.
[0028] According to one embodiment, method of the present disclosure includes the steps of receiving from an analog circuit, at a microcontroller of an electronic trip unit of a circuit breaker, sensed peak value of fault current; and determining, at the microcontroller, if the sensed peak value of fault current is greater than a defined threshold such that when the sensed peak value of fault current is greater than the defined threshold, the microcontroller issues a tripping command to the circuit breaker.
[0029] In an aspect, the time taken from detection of peak value of fault current to issuance of the tripping command is within 5 ms. In another aspect, the microcontroller receives multiple sensed peak values of fault current from the analog circuit to compare each received sensed peak value with the threshold.
[0030] In yet another aspect, purpose of the proposed logic is to sense the ‘Make On’ Short Circuit fault, for instance above 10 times of nominal current of circuit breaker (10In) and provide reliable trip command within quarter cycle of fault current.
[0031] In existing/conventional systems, fault current is detected by ADC sample values taken over a period of cycle or half cycle and software algorithm is configured to detect the fault condition, leading to additional of time delay, making it difficult to achieve fault detection within quarter cycle.
[0032] In order to achieve faster sensing of fault condition, the present disclosure provides an analog sensing circuit, which measures and holds on the threshold value for minimum 5ms if the fault current peak value is more than the set threshold.
[0033] In an embodiment, threshold for analog circuit can be kept at particular level and when the microcontroller of the electronic trip unit of the circuit breaker powers up, the controller can be provided with the peak value sensed by the proposed analog circuit, which value can be sensed by ADC channel of the microcontroller. Several successive samples of this peak value can be sensed at regular intervals to filter out the noise signal(s) from actual fault signal(s) such that if a sensed sample value crosses the set threshold value, a tripping command can be issued by the microcontroller.
[0034] FIG. 1 illustrates an exemplary block diagram 100 showing fault current and tripping action mechanism in accordance with an embodiment of the present disclosure, wherein as shown, blocks 102 and 104 relate to powering up and resetting of the microcontroller of the electronic trip unit of the circuit breaker and function initialization to detect when the tripping action is to be initiated. Block 106 can be configured to receive incoming current and supplying the same to the microcontroller (as shown from block 106 to 104) as well as to the analog circuit (as shown from 106 to 108) of the present disclosure, wherein the analog sensing input circuit at block 108 can detect peak values of fault current and send them to the ADC of the microcontroller. At block 110, the ADC can perform sampling from analog to digital signal, based on which tripping action can be taken at block 112 by the microcontroller. As shown at block 114, along with taking input of peak values of fault current from the analog circuit, microcontroller of the present disclosure can further configured to incorporate factors such as voltage readiness of fault section detection (FSD).
[0035] FIG. 2 illustrates an exemplary flow diagram 200 for taking tripping decisions based on peak values of fault current that are detected by the proposed analog circuit in accordance with an embodiment of the present disclosure. At step 202, current sensing can be performed by the analog circuit, wherein at step 204, it is determined if fault current is detected. In case the fault current is detected at the analog circuit, at step 216, it is determined if the detected fault current is greater than a defined threshold (i.e. if the FSD voltage is healthy), wherein if the detected fault current is greater than the defined threshold, at step 218, fault section detection can be performed (i.e. FSD can be operated) and at step 220, fault detection flag can be reset. At step 222 thereafter, the tripping or other configured logic can be executed.
[0036] On the other hand, if at step 204, no fault current is detected by the analog circuit, logic high level detection of the analog trip comparator output can be performed at step 206. At step 208, it is determined if the logic high level is detected, which if not affirmative, the method moves to step 222, else, at step 210, counter of the analog trip comparator output can be incremented. At step 212, the counter incremented at step 210 can be compared at with a set count such that if the counter is not equal to the set count, the method moves to step 222, else the method moves to step 214 to set the fault detection flag indicating that fault current has been detected, and resetting the counter. The method can then move to step 216 as described above where it is determined if the detected voltage is greater than a defined threshold.
[0037] 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
[0038] The present disclosure provides a method/system that reduces the time needed to address an overcurrent fault.
[0039] The present disclosure provides a method to achieve fast high fault current trip time in self- power mode at make-on fault condition.
[0040] The present disclosure provides a method/system that reduces the time needed to address an overcurrent fault within 5ms with tolerance of 0ms to +2ms.
[0041] The present disclosure provides an application where severe short circuit faults need to be addressed within 5ms with reliable and accurate digital trip command.