DESC:FIELD OF THE INVENTION

[001] This instant application, in general, pertains to current sensors, and more particularly to, a current sensor for use in sensing, control and monitoring of current signal in electrical power system and measuring of current.

BACKGROUND AND PRIOR ART

[002] A current sensor is a device that detects electric current (AC or DC) in a wire, in general, and generates a signal proportional to it. The generated signal could be an analog voltage or current or even digital output. It can be then be utilized to display the measured current or can be stored for further analysis in a data acquisition system or can be utilized for control purpose.

[003] With the advent of microprocessor-based protection and measurement equipments, it has become necessary to sense, control and monitor the current signals in electrical power systems and measure current in a wire. Conventionally, Rogowski coils are also suitable for measuring current in a variety of other applications, including, for example, measuring the current distribution in parallel fuses or in parallel bus bars.

[004] Rogowski coil is an electrical device for measuring alternating current (AC) or high speed current pulses. It consists of a helical coil of wire with the lead from one end returning through the centre of the coil to the other end, so that both terminals are at the same end of the coil. The whole assembly is then wrapped around the straight conductor whose current is to be measured.

[005] In prior art, inductive measuring procedures employing the Rogowski principle is comprises of several turns of the conductive coil disposed evenly on a non-conductive bobbin surrounding the primary conductor through which the current is to be measured. The former on which the winding is disposed can be a flexible plastic core or a printed circuit board on which the coil is implemented by metal deposits on each of the two phases of the plate. These embodiments talk of either a single Rogowski coil or a plurality of Rogowski coils connected in a cascaded fashion on a base plate.

[006] Reference is made to document US2011/0148561A1, wherein a low-cost and high-precision current sensing device and methods for use and manufacturing is disclosed. In one embodiment, the current sensing apparatus comprises a Rogowski-type coil which is manufactured in segments so as to facilitate the manufacturing process.

[007] Reference is made to document US2013/0193987A1, wherein devices for measuring electrical current and related systems and methods for forming and using such devices are disclosed which comprise Rogowski coils.

[008] Reference is made to document US Patent No. 5,414,400, which discloses a Rogowski coil comprising at least one printed circuit plate provided with a circular cutout, the coil being implemented by rectilinear metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof intersect in the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated through holes that pass through the thickness of the plate.

[009] Reference is made to document U.S. Patent No.7,227,442 which discloses precision printed circuit board based Rogowski coil formed including a printed circuit board including a first layer and second layer.

[0010] Reference is also made to document U.S. Patent No. 4,709,205 and U.S. Publication No. 2013/0043967A1, which disclose the use of plurality of Rogowski coils in a cascaded fashion disposed on a base plate to detect or monitor current signals.

[0011] However, the prior art documents cited above takes into account the non-magnetic nature of the core i.e. air-core and by this, various associated advantages like linearity response, non-saturation effect, better EMI response, cheaper structure due to the absence of the core etc. are claimed. One major concern of these embodiments is the strength of the measured signal from the Rogowski coil, which is feeble and thus needs further amplification to bring it up to the level of measurable range.

[0012] Thus, in view the hitherto drawbacks of the existing inductive measuring procedures, there exists a dire need to provide an improved circuit assembly that enhances the signal strength of the sensor output such that there is no needs of further amplification to bring it up to the level of measurable range, thereby bypassing the need of associated costly and complex signal processing and strengthening circuits.

SUMMARY OF THE INVENTION

[0013] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0014] An object of the present invention is to overcome the feebleness of output from almost all air-cored Rogowski current sensors or any weak output current sensor such as to improve signal to noise ratio which leads to better metering and protection accuracy.

[0015] Another object of the present invention is to provide a hybrid arrangement of a sensor device for augmenting the sensor output.

[0016] Still another object of the present invention is to eradicate the feebleness of the Rogowski sensors by meticulous insertion of a magnetic core into it, thus strengthening the signal output from the sensor and thus bypassing the need of associated costly and complex signal processing circuits.

[0017] In one aspect, a sensor for measuring a current in a conductor is disclosed. The sensor includes at least one inner coil, at least one outer coil, and one or more planar insulating substrates.

[0018] The at least one inner coil further includes at least one first printed conductor loop wound with a substantially constant winding density in a first direction on top layer on a first metallic substrate, and at least one second printed conductor loop wound with a substantially constant winding density in a first direction on bottom layer on the metallic substrate. The at least one second printed conductor loop is connected in series with the at least one first printed conductor loop, via a hole pierced through the first metallic substrate, forming a first section (A).

[0019] The at least one outer coil further includes at least one first printed conductor loop wound with a substantially constant winding density in a second direction on top layer on a second metallic substrate, and at least one second printed conductor loop wound with a substantially constant winding density in a second direction on bottom layer on the metallic substrate. The at least one second printed conductor loop is connected in series with the at least one first printed conductor loop, via a hole pierced through the second metallic substrate, forming a second section (B).

[0020] The one or more planar insulating substrates are formed by connecting the first section (A) continuously in odd sequence in forward direction and the second section (B) in even sequence in reverse direction.

[0021] In one implementation manner of the above aspect, the sensor further includes a current conductor with a substantially constant cross section adapted to enclose the at least one inner coil, the at least one outer coil, and the one or more planar insulating substrates.

[0022] In one implementation manner of the above aspect, the sensor further includes one or more analog integrator electronics incorporated in the first metallic substrate and the second metallic substrate.

[0023] In one implementation manner of the above aspect, the one or more planar insulating substrates is at least one circular metallic strip, preferably made of a sheet steel or an iron steel metal, passing through a cutout provided on the first metallic substrate and the second metallic substrate, and thereby adapted to induce magnetic field production whilst generating a resultant signal output of the sensor.

[0024] The present invention provides a hybrid sensor device for measuring of alternating current in a conductor by inclusion of a magnetic strip into a Rogowski coil or any weak output current sensor which improves signal to noise ratio which leads to better metering and protection accuracy.

[0025] In one implementation, a peak detector circuit is employed to detect the peak of the non-sinusoidal output from the said hybrid sensor (a combination of any air-cored current sensor and a magnetic ring which saturates early due to very low form factor) and it varies with the variance in the hybrid sensor output based on the primary current. A common notion of coreless trait attributed to a Rogowski current sensor is addressed differently (hybrid) here for better performance

[0026] Accordingly, the present invention by the said circular metallic strips magnetic characteristics assists in the induced magnetic field production that ultimately strengthens the resultant signal output from the sensor, thereby bypassing the need of associated costly and complex signal processing circuits in order to sense, control and monitor the current signals in electrical power systems.

[0027] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0028] Figure 1 illustrates a perspective view of the current sensor in accordance with an embodiment of the present invention.

[0029] Figure 2 illustrates a tear down view in accordance with an embodiment of the present invention.

[0030] Figure 3 illustrates a pictorial view of hybrid current sensor with metallic strip, in accordance with an embodiment of the present invention.

[0031] Figure 4(a) and 4(b) illustrates visualization of magnetic in sensor model of hybrid current sensor and rogowski current sensor respectively, in accordance with an embodiment of the present invention.

[0032] Figure 5(a) and 5(b) shows a time versus voltage graph to illustrate sensor output values of hybrid current sensor and rogoswki current sensor respectively, in accordance with an embodiment of the present invention

[0033] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0034] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0035] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0036] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0037] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0038] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that dethroughtion or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0039] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0040] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0041] The instant application discloses a hybrid arrangement of a current sensor for measuring an alternating current in a conductor.

[0042] The present invention achieves the objective by inclusion of a magnetic strip into a Rogowski coil or any weak output current sensor to form a hybrid structure of a sensor device, which improves signal to noise ratio which leads to better metering and protection accuracy. In one embodiment, a peak detector circuit can detect the peak of the non-sinusoidal output from the said hybrid sensor (a combination of any air-cored current sensor and a magnetic ring which saturates early due to very low form factor) and it can vary with the variance in the hybrid sensor output based on the primary current.

[0043] In one implementation, the layout of the current sensor coil includes:
i. A first printed conductor loop wound with a substantially constant winding density in a first direction on top layer on a metallic substrate and a second printed conductor loop wound with a substantially constant winding density in a first direction on bottom layer on a metallic substrate. The second loop connected in series with the first loop through a through hole pierced through a metallic substrate forms section A.
ii. A first printed conductor loop wound with a substantially constant winding density in a second direction on top layer on a metallic substrate, and a second printed conductor loop wound with a substantially constant winding density in a second direction on bottom layer on a metallic substrate. The second loop connected in series with the first loop through a through hole pierced through a metallic substrate forms section B.

[0044] In one implementation, a plurality of planar insulating substrate formed by connecting section a continuously in odd sequence in forward direction and the section B in even sequence in reverse direction.

[0045] In one implementation, the whole arrangement can be placed around a current conductor that has a substantially constant cross section.

[0046] In one implementation, the analog integrator electronics are also incorporated in the said PCB substrate which will give an added advantage of sheer compactness.

[0047] In one implementation, a circular metallic strip (sheet steel/iron steel) will pass through the cutout on the printed circuit board. By using said metallic strip’s magnetic characteristics, it assists in the induced magnetic field production which ultimately strengthens the resultant signal output from the said sensor.

[0048] The present invention eradicates the feebleness of the Rogowski sensors by meticulous insertion of a magnetic core into it, thus strengthening the signal output from the sensor and thus bypassing the need of associated costly and complex signal processing circuits.

WORKING EXAMPLE & RESULT ANALYSIS

[0049] According to one exemplary implementation, wherein the invention has been tested by 1kA primary current through the line conductor there is provided a result analysis of a comparison of a hybrid current sensors with normal rogowski sensors. Referring to figure 4(a) visualization of magnetic in sensor model of hybrid current sensor is shown. A circular metallic strip or metallic ring along with the rogowski coil which passes through the cut out on the printed circuit board that assist in inducing magnetic field production which ultimately strengthens the resultant signal output from the said sensor. Further, referring to figure 4(b) visualization of magnetic in rogowski current sensor clearly shows no metallic ring present with the rogoswki coil. The magnetic flux is calculated for both hybrid current sensor and Rogowski current sensor and a vector plot is drawn which shows the maximum and minimum values of vector plot T
Hybrid current sensor:
Maximum: 1.3573E +00
Minimum: 1.9419E -02
Rogowski current sensor:
Maximum: 7.4808E-02
Minimum: 1.5694-02

[0050] Referring now to figure 5(a) and 5(b), a time versus voltage graph is drawn to calculate the senor output value wherein X axis denotes time in seconds and Y axis denotes voltage in volts
The calculated sensor output values:
Hybrid current sensor:
Y axis: 0.5 mV/div, X axis: 10 msec/div
Rogoswki current sensor:
Y axis: 5 uV /div, X axis: 10 msec /div
It can be concluded from the sensor output values calculated from the graphical representation between time(in seconds ) and circuit voltage (in volts) that the hybrid current sensor yields amplified output as compared to normal rogowski sensor and a better signal to noise ratio hence the need for amplifier electronics is optional in case of hybrid current sensor .

[0051] Apart from what is disclosed above, some of the important features of the present invention, considered to be noteworthy are mentioned below:
i. The present invention strengthens the signal output from the sensor.
ii. The present invention is a means of easy interface with simple connections.
iii. The present invention provides a cost effective solution by using the existing hardware interface.
iv. The present invention eradicate the feebleness of the Rogowski sensors by meticulous insertion of a magnetic core into it, thus strengthening the signal output from the sensor and thus bypassing the need of associated costly and complex signal processing circuits.

[0052] It may be clearly understood by a person skilled in the art that for the purpose of convenient and brief description, for a detailed working process of the foregoing system, devices, and unit, reference may be made to a corresponding process in the foregoing device/apparatus embodiments, and details are not described herein again.

[0053] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and device may be implemented in other manners. For example, a plurality of units or components or mechanisms may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

[0054] The various mechanisms described as separate parts may or may not be physically separate, and the parts displayed as mechanisms may or may not be physical units, may be located in one position, or may be distributed at various location of the device. Some or all of the units may be selected to achieve the objective of the solution of the embodiment according to actual needs.

[0055] In addition, the mechanisms in the embodiments of the present invention may be integrated into one processing unit, or each of the mechanisms may exist alone physically, or two or more mechanisms may be integrated into one mechanism.

[0056] Although a hybrid current sensor and method thereof disclosed, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the hybrid current sensor and method thereof.
,CLAIMS:1. A sensor for measuring a current in a conductor, the sensor comprising:
at least one inner coil having:
at least one first printed conductor loop wound with a substantially constant winding density in a first direction on top layer on a first metallic substrate;
at least one second printed conductor loop wound with a substantially constant winding density in a first direction on bottom layer on the metallic substrate, wherein the at least one second printed conductor loop is connected in series with the at least one first printed conductor loop, via a hole pierced through the first metallic substrate, forming a first section (A);
at least one outer coil having:
at least one first printed conductor loop wound with a substantially constant winding density in a second direction on top layer on a second metallic substrate;
at least one second printed conductor loop wound with a substantially constant winding density in a second direction on bottom layer on the metallic substrate, wherein the at least one second printed conductor loop is connected in series with the at least one first printed conductor loop, via a hole pierced through the second metallic substrate, forming a second section (B);
one or more planar insulating substrates formed by connecting the first section (A) continuously in odd sequence in forward direction and the second section (B) in even sequence in reverse direction.

2. The sensor as claimed in claim 1, wherein the sensor further comprises a current conductor with a substantially constant cross section adapted to enclose the at least one inner coil, the at least one outer coil, and the one or more planar insulating substrates.

3. The sensor as claimed in claim 1, wherein the sensor further comprises one or more analog integrator electronics incorporated in the first metallic substrate and the second metallic substrate.

4. The sensor as claimed in claim 1, wherein the one or more planar insulating substrates is at least one circular metallic strip, preferably made of a sheet steel or an iron steel metal, passing through a cutout provided on the first metallic substrate and the second metallic substrate, and thereby adapted to induce magnetic field production whilst generating a resultant signal output of the sensor.

5. The system as claimed in claim 1 is characterized in that the sensor improves signal to noise ratio which leads to better metering and protection accuracy.