Description:TECHNICAL FIELD
[0001] The embodiments of the present disclosure generally relate to measurement of alternating current (AC) in electrical circuits and current sensors used for monitoring current flow in power systems. More particularly, it relates to system, current measuring device and method for noise cancellation and accurate measurement of electric current.

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] Electronic trip units (ETU) have now been applied widely in intelligent low voltage circuit breakers (LVCB). When a fault current occurs, an electronic trip unit has to be able to send a trip signal to cut off a circuit, so as to protect the power line and electronic equipment.
[0004] In order to realize the above protection function of an electronic trip unit, it is necessary to make use of a large current measurement device to measure a current in power lines accurately regardless of whether the electronic equipment is operating normally or has a fault. In this case, the magnitude of the current may change in a very large range. Since the electronic trip unit will use the measured signal to calculate an accurate trip time so as to protect the power line and electronic equipment better, the measurement performed by the large current measurement device has to be very accurate. In order to prevent the circuit of an electronic trip unit from external interferences during its normal operation, an electrical isolation is also needed during the measurement. At the same time, when the large current measurement device is applied in a low voltage circuit breaker, such as a molded case circuit breaker (MCCB) or an air circuit breaker (ACB), it has to be capable of supplying power to the electronic trip unit via the power lines.
[0005] Ideally, current sensing/ measurement happens using current transformer (CT), a Rogowski coil or a current shunt. Often, we use shunt for current measurement for its cost and temperature co-efficient advantages.
[0006] As the alternating M/EM field gets coupled with the Alternating Primary current and inducing a noise over it. This leads to deviation in measurement because of M/EM field. Further, the current measurement through shunt also gets impacted by the external abnormal EM / Magnetic field by means of noise coupling.
[0007] However, the requirement of class of accuracy or/and detecting the abnormal field is also part of IS/IEC standards.
[0008] Usually, EM field is suppressed by a low pass filter in the measurement path to some extent.
[0009] Abnormal AC magnetic field is either detected using a magnetic detection circuit or IC or using a PCB hall sensor.
[0010] Field can be suppressed by using magneto resistance material for AC magnetic field.
[0011] Hence, there is a need for a simple, efficient and improved system, device and method that allows noise cancellation and accurate Root Mean Square (RMS) measurement in presence of abnormal alternating electro-magnetic (EM )/ magnetic (M) field.

SUMMARY
[0012] This section is provided to introduce certain objects and aspects of the present invention in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter. In order to overcome at least a few problems associated with the known solutions as provided in the previous section, an object of the present disclosure is to provide system, current measuring device and method for noise cancellation and accurate measurement of electric current.
[0013] The present invention enables to provide RMS Measurement accuracy in presence of abnormal AC magnetic fields/ EM fields.
[0014] The present invention enables to obtain accurate RMS measurement using Noise cancellation technique even in Abnormal AC EM/M field.
[0015] 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
[0016] The accompanying drawings, which are incorporated herein, and constitute a part of this invention, illustrate exemplary embodiments of the disclosed methods and systems in which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that invention of such drawings includes the invention of electrical components, electronic components or circuitry commonly used to implement such components.
[0017] FIG. 1 illustrates an exemplary current shunt device providing different plans of sensing, according to embodiments of the present disclosure.
[0018] FIG. 2 illustrates an exemplary sensor arrangement, according to embodiments of the present disclosure.
[0019] FIG. 3 illustrates an exemplary field distribution graph obtained for the exemplary sensor arrangement as shown in FIG. 2, according to embodiments of the present disclosure.
[0020] FIG. 4 illustrates a block diagram of a system for measuring an electric current, according to embodiments of the present disclosure.
[0021] FIG. 5 illustrates a method for measuring an electric current, according to embodiments of the present disclosure.
[0022] The foregoing shall be more apparent from the following more detailed description of the invention.
DETAILED DESCRIPTION
[0023] Various example embodiments will now be described more fully with reference to the accompanying drawings in which only some example embodiments are shown. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The present invention, however, may be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein.
[0024] Accordingly, while example embodiments of the invention are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the present invention to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the invention. Like numbers refer to like elements throughout the description of the figures.
[0025] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments of the present invention. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items.
[0026] It will be understood that when an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between,” versus “directly between,” “adjacent,” versus “directly adjacent,” etc.).
[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms “and/or” and “at least one of” include any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
[0028] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0029] Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are interpreted accordingly.
[0030] Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention.
[0031] In order to overcome at least a few problems associated with the known solutions as provided in the previous section, an object of the present disclosure is to provide system, current measuring device and method for noise cancellation and accurate measurement of electric current.
[0032] The present invention enables to provide RMS Measurement accuracy in presence of abnormal AC magnetic fields/ EM fields.
[0033] The present invention enables to obtain accurate RMS measurement using Noise cancellation technique even in Abnormal AC EM/M field.
[0034] The present invention will be explained in detail hereinbelow in conjunction with the drawings.
[0035] As shown in FIG. 1, two identical / non identical sensor calibrated to give synchronous output in the EM/M field are placed in a different axis to obtain the results of EM/M field variation with respect to time domain. In general, the EM/M wave can be any frequency which will be transverse in nature.
[0036] As the field is in sinusoidal form, the effect of the field is at peak at different axes. For example, a Sensor A is placed in X-axis whereas a sensor B is placed in Y or Z axis, so that the Magnitude of EM/M field is not getting coupled to both the sensors simultaneously. FIG. 2 illustrates an exemplary sensor arrangement, according to embodiments of the present disclosure. FIG. 3 illustrates an exemplary field distribution graph obtained for the exemplary sensor arrangement as shown in FIG. 2, according to embodiments of the present disclosure.
[0037] Working principle: Considering Sensor-A, the primary current flowing through the sensor element will be converted to secondary voltage by mutual inductance principle (Rogowski)/Resistive drop (in shunt, ohms law). An anti-aliasing filter is used to filter the conducted noise coupling to secondary, and same is acted as a Low pass filter for conducted field. The voltage drop in the secondary is proportional to the magnitude of current flowing. By using an ADC, the analog secondary voltage is converted into Digital samples.
[0038] In this invention, each digital sample of sensor-A is considered as SENSOR_1_SAMPLE and sensor-B digital output is considered as SENSOR_2_SAMPLE.
[0039] In ideal conditions, |SENSOR_1_ SAMPLE - SENSOR_1_ SAMPLE| = 0……………………………………………. (i)
i.e., Absolute difference between Sensor A sample output and sensor B sample output are same in the absence of EM/M field.
[0040] When the measuring element is getting affected by the external abnormal electromagnetic/ magnetic alternating field, the sensor-A which is directly proportional to primary current and additional noise current.
[0041] When field is acting on x-axis, means the Noise is coupled on the x -axis. At the same instance the other axis sensor is not impacted by EM/M field.
[0042] So, this invention holds good the below RMS accurate measurement equation,
I Noise = ABS (I Sensor_A – I Sensor_B) …………………………………………….(ii)
Where, ISensor_A is the RMS current which may be impacted with Noise
ISensor_B is the RMS current which is not impacted by external field
Now I Noise in ideal conditions, will be zero. And
I max = MAX (I Sensor_A – I Sensor_B) …………………………………………….(iii)
I Accurate = I Max – I
Noise………………………………….…………………………….(iv)
[0043] With the help of this invention, any measuring system can accurately measure the Electrical quantities by eliminating the Noise factor which is present/ generated in the environment
[0044] FIG. 4 illustrates a block diagram of a system for measuring an electric current, according to embodiments of the present disclosure.
[0045] In an exemplary embodiment, a current measuring device (100) is disclosed. The device includes an input end to receive an electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field; a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage; and a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage.
[0046] In this embodiment, the first sensor element (102) and the second sensor element (104) are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain.
[0047] In this embodiment, the first secondary voltage and the second secondary voltage are used to measure a magnitude of the electric current.
[0048] In this embodiment, the first sensor element and the second sensor element is a current transformer (CT), a Rogowski coil or a current shunt.
[0049] In this embodiment, the electric current is an Alternating current (AC), and wherein the magnitude is measured in the form of Root Mean Square (RMS) measurement.
[0050] In this embodiment, the current measuring device includes an output end to transfer the electric current to a connected electric component.
[0051] In this embodiment, the first sensor element and the second sensor element are identical or non-identical sensors calibrated to generate a synchronous output in the EM field or the M field.
[0052] In this embodiment, the first secondary voltage and the second secondary voltage of the EM field or the M field variation are obtained by mutual inductance.
[0053] In this embodiment, the first secondary voltage and the second secondary voltage is provided as an input to an anti-aliasing filter (AAF) (106) to filter a noise in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to the magnitude of the received electric current.
[0054] In this embodiment, the first secondary voltage and the second secondary voltage, after noise filtering, are converted into digital samples using an analog-to-digital converter (ADC) (108).
[0055] In another embodiment, a system for measuring an electric current is provided. The system includes a current measuring device (100) having an input end to receive an electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field; a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage; and a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage, an anti-aliasing filter (AAF) (106) to filter a noise in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to an magnitude of the received electric current; and an analog-to-digital converter (ADC) (108) to convert the first secondary voltage and the second secondary voltage into digital samples after noise filtering.
[0056] In this another embodiment, the first sensor element (102) and the second sensor element (104) are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain.
[0057] In this another embodiment, the first secondary voltage and the second secondary voltage are used to measure a magnitude of the electric current.
[0058] FIG. 5 illustrates a method for measuring an electric current, according to embodiments of the present disclosure.
[0059] At step 502, the electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field is received at an input end of a current measuring device.
[0060] At step 504, the received electric current is allowed to pass through a first sensor element and the received electric current is converted in to a first secondary voltage.
[0061] At step 506, the received electric current is allowed to pass through a second sensor element and the received electric current is converted in to a second secondary voltage.
[0062] The first sensor element and the second sensor element are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain.
[0063] At step 508, a noise is filtered in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to a magnitude of the received electric current.
[0064] At step 510, the first secondary voltage and the second secondary voltage are converted into digital samples, after noise filtering, by an analog-to-digital converter (ADC).
[0065] What are described above are merely preferred embodiments of the present invention, and are not to limit the present invention; any modification, equivalent replacement and improvement within the spirit and principle of the present invention should be included in the protection scope of the present invention.
[0066] The patent claims filed with the application are formulation proposals without prejudice for obtaining more extensive patent protection. The applicant reserves the right to claim even further combinations of features previously disclosed only in the description and/or drawings.
[0067] The example embodiment or each example embodiment should not be understood as a restriction of the invention. Rather, numerous variations and modifications are possible in the context of the present disclosure, in particular those variants and combinations which can be inferred by the person skilled in the art with regard to achieving the object for example by combination or modification of individual features or elements or method steps that are described in connection with the general or specific part of the description and are contained in the claims and/or the drawings, and, by way of combineable features, lead to a new subject matter or to new method steps or sequences of method steps, including insofar as they concern production, testing and operating methods.
[0068] References back that are used in dependent claims indicate the further embodiment of the subject matter of the main claim by way of the features of the respective dependent claim; they should not be understood as dispensing with obtaining independent protection of the subject matter for the combinations of features in the referred-back dependent claims. Furthermore, with regard to interpreting the claims, where a feature is concretized in more specific detail in a subordinate claim, it should be assumed that such a restriction is not present in the respective preceding claims.
[0069] Since the subject matter of the dependent claims in relation to the prior art on the priority date may form separate and independent inventions, the applicant reserves the right to make them the subject matter of independent claims or divisional declarations. They may furthermore also contain independent inventions which have a configuration that is independent of the subject matters of the preceding dependent claims.
[0070] Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
[0071] Example embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
, Claims:1. A current measuring device (100) comprising:
an input end to receive an electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field;
a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage;
a second sensor element (104) to allow passage of the received electric current therethrough and convert the received electric current in to a second secondary voltage;
wherein the first sensor element (102) and the second sensor element (104) are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain; and
wherein the first secondary voltage and the second secondary voltage are used to measure a magnitude of the electric current.
2. The current measuring device as claimed in claim 1, wherein the first sensor element and the second sensor element is a current transformer (CT), a Rogowski coil or a current shunt.
3. The current measuring device as claimed in claim 1, wherein the electric current is an Alternating current (AC), and wherein the magnitude is measured in the form of Root Mean Square (RMS) measurement.
4. The current measuring device as claimed in claim 1, wherein the current measuring device includes an output end to transfer the electric current to a connected electric component.
5. The current measuring device as claimed in claim 1, wherein the first sensor element and the second sensor element are identical or non-identical sensors calibrated to generate a synchronous output in the EM field or the M field.

6. The current measuring device as claimed in claim 1, wherein the first secondary voltage and the second secondary voltage of the EM field or the M field variation are obtained by mutual inductance.
7. The current measuring device as claimed in claim 1, wherein the first secondary voltage and the second secondary voltage is provided as an input to an anti-aliasing filter (AAF) (106) to filter a noise in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to the magnitude of the received electric current.
8. The current measuring device as claimed in claim 7, wherein the first secondary voltage and the second secondary voltage, after noise filtering, are converted into digital samples using an analog-to-digital converter (ADC) (108).
9. A system for measuring an electric current, the system comprising:
a current measuring device (100) having:
an input end to receive the electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field
a first sensor element (102) to allow passage of the received electric current therethrough and convert the received electric current in to a first secondary voltage;
a second sensor element (104) to allow passage of the received electric current therethrough and convert the received electric current in to a second secondary voltage;
wherein the first sensor element and the second sensor element are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain;
an anti-aliasing filter (AAF) (106) to filter a noise in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to an magnitude of the received electric current; and
an analog-to-digital converter (ADC) (108) to convert the first secondary voltage and the second secondary voltage into digital samples after noise filtering.
10. A method for measuring an electric current, the method comprising:
receiving (502), at an input end of a current measuring device, the electric current, wherein the electric current includes an alternating electro-magnetic (EM) or an alternating magnetic (M) field;
allowing (504) passage of the received electric current through a first sensor element and converting the received electric current in to a first secondary voltage;
allowing (506) passage of the received electric current through a second sensor element and converting the received electric current in to a second secondary voltage;
wherein the first sensor element and the second sensor element are positioned at different axis on the current measuring device to obtain the first secondary voltage and the second secondary voltage of the EM field or the M field variation with respect to a time domain;
filtering (508), by an anti-aliasing filter (AAF), a noise in the first secondary voltage and the second secondary voltage, such that voltage drop in the first secondary voltage and the second secondary voltage is proportional to a magnitude of the received electric current; and
converting (510), by an analog-to-digital converter (ADC), the first secondary voltage and the second secondary voltage into digital samples after noise filtering.