Circuit Breaker For Early Short Circuit Detection In An Electrical Network And A Method Thereof
Abstract:
The present disclosure relates to system and method enables to detect of short-circuit fault conditions in an electrical network. A method for early short circuit detection in an electrical network can include the steps of: receiving, a current signal sample, at a Rogowski coil that is configured as a current sensor in electrical network; processing, at Rogowski coil, the current signal sample to output derivative of the current signal sample; numerically integrating, at an integrator, the derivative of the current signal sample to obtain integrated current signal; processing, at a processing block, the integrated current signal to calculate estimated peak of the current signal; and comparing, at a main processing unit, the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value, detection flag being representative of a potential short circuit.
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Notices, Deadlines & Correspondence
4th Floor, SDDC-R,TC-2 Tower B,
L&T Business Park, Gate No. 5,
Saki Vihar Road, Powai, Mumbai – 400081, Maharashtra, India
2. GARG, Shaini
4th Floor, SDDC-R, TC-2 Tower B,
L&T Business Park, Gate No. 5,
Saki Vihar Road, Powai, Mumbai – 400081, Maharashtra, India
3. TANDON, Swati
34/5, lane no.6, Vijay Park Extn, Dehradun, Uttarakhand-248001, India.
Specification
Claims:
1. A method for early short circuit detection in an electrical network, said method comprising the steps of:
receiving, at a Rogowski coil that is configured as a current sensor in said electrical network, a current signal sample;
processing, at said Rogowski coil, the current signal sample to output derivative of the current signal sample;
numerically integrating, at an integrator, the derivative of the current signal sample to obtain integrated current signal;
processing, at a processing block, the integrated current signal to calculate estimated peak of the current signal; and
comparing, at a main processing unit, the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value, said detection flag being representative of a potential short circuit.
2. The method of claim 1, wherein said potential short circuit is confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
3. The method of claim 2, wherein upon said potential short circuit being confirmed, a trip signal is issued by a tripping unit.
4. The method of claim 1, wherein the estimated peak of the current signal is calculated as: .
5. The method of claim 1, wherein the estimated peak of the current signal is calculated using N point regression.
6. The method of claim 1, wherein said estimated peak of the current signal is further refined through Newton Raphson iterative technique, said Newton Raphson technique being processed based on point on wave.
7. The method of claim 1, wherein prior to the step of numerically integrating, the method performs high frequency filtering of the derivative of the current signal sample, followed by digitizing said filtered current signal sample.
8. A circuit breaker comprising a tripping unit, said circuit breaking comprising:
a Rogowski coil configured as a current sensor to receive a current signal sample, and process the current signal sample to output derivative of the current signal sample;
an integrator configured to numerically integrate the derivative of the current signal sample to obtain integrated current signal;
a processing block configured to process the integrated current signal to calculate estimated peak of the current signal; and
a main processing unit configured to compare the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value, said detection flag being representative of a potential short circuit.
9. The circuit breaker of claim 7, wherein said potential short circuit is confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
10. The circuit breaker of claim 7, wherein upon said potential short circuit being confirmed, a trip signal is issued by said tripping unit.
, Description:
TECHNICAL FIELD
[0001] The present disclosure relates to the short circuit fault detection, and more specifically relates to, but not by way of limitation, a system and method that enables to detect of short-circuit fault conditions in an electrical network, as well as to a device which uses this method.
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 invention will be illustrated with particular reference to a preferred application in a low-voltage electrical power distribution network, although this is not to be understood as limiting, and in any event the invention applies in general to both medium and low-voltage networks.
[0004] Faults (short circuits) are inevitable. Any power system is expected to suffer several faults each year. The number will depend on exposure to lightning and damage from trees, as well as the age of the system's components. When a short circuit fault occurs in the distribution network, a short circuit current will flow to the fault location. This short circuit current is detected and cleared by existing protection equipment, such as circuit breakers or fuses. However, when fault levels go beyond the existing design limits due to the connection of electrical equipments, uprating the capability of existing protection equipment such as circuit breakers is the only option to increase the fault level capabilities of the network.
[0005] Such faults may be caused because of the aging, supply overvoltage, and other such natural or man-made causes the electrical circuit contact or collide, and a sudden increase in current. Since the electrical short circuit line current suddenly increases, which large instantaneous heat release, heat much more than when the line is working properly, not only make the part of the electrical wiring insulation burned, but also can cause severe melted parts of the electrical circuit, causing fire fuel combustion, so the short-circuit failure caused the problem has been adversely affected and damage to production and life. Early Fault Detection is a technique intended to short circuit fault detection in micro second range.
[0006] In modern power distribution networks, short-circuit currents should be limited as much as possible in order to prevent damages to distribution lines and loads. Low-voltage systems comprise rising short-circuit powers and coupling of several networks. Conventional mechanical low-voltage protection devices obtain the mechanical energy required for switching off from a spring energy store and failure detection based on thermal-magnetic tripping units.
[0007] In modern automatic circuit breakers for low and medium voltage, devices for detecting faults are integrated in the circuit breakers, and such detection of faults is often performed by means of devices of electronic type. However, the detection of short-circuits, characterized by very high current and by the need for very rapid actuation so as to eliminate the fault, is still carried out at the present time by electromechanical devices based on the electrodynamics effect.
[0008] The calibration of these short-circuits detection devices is very difficult and is carried out on an empirical basis. This leads to low accuracy in the determination of the actuation times of the circuit breaker. Moreover, with these electromechanical devices it is not possible to gather, in the case of a short-circuit fault, detailed information about the fault such as, for example, the peak current characterizing the fault, the complex impedance of the circuit or the angle of the voltage at the moment of extinction of the fault. This information would be useful among other things for diagnostic and statistical purposes.
[0009] Efforts have been made in related art to address above stated problem by using method for detecting short-circuit conditions. An example of such short-circuit condition detection is recited in a United States Patent 6437576, entitled “method for detecting short-circuits conditions and device”, which uses this method. In this patent the method is based on estimating the electrical characteristics of the short-circuit load and calculating the peak value of the current on the basis of N successive samples of the instantaneous current and its first derivative. Further this disclosure relates to a method able rapidly to detect the initiating of short-circuit conditions in an electrical network. In addition to short circuit detection, simultaneous calculation of the short circuit power factor and of the phase of the voltage at the moment of short circuit is also possible. The patent claims the detection time in milliseconds. Another example of short-circuit condition detection methods are recited in United States Patents. 6313639 B1 and 6844737 B2. These patents are based on the root locus approach which involves the current and its first and second derivative or any two of them continuously and successively at the same time and are processed as a digital numerical sequence. The basic ideas behind these disclosures are to plot root loci for determination of thresholds, also called ‘limit curves’. Detection is based on the numerical sequences crossing their respective limit curves. These patents claim the detection time in microsecond range. Also, involvement of second derivative makes the method more sensitive to high frequency noise and harmonic interference in the current signal which will result in false detection.
[00010] Yet another example of such short-circuit condition detection is also disclosed in the Journal of Power and Energy Engineering, 2014, 2, 432-437. The papers provide various methods to detect the short circuit based on regression method which involves sequence of the current and it’s integral in time for determining the prospective current peak. Short circuit will be identified when estimated Current peak exceeds the preset threshold. This method is suitable only for sinusoidal signal at a given frequency for a resistive-inductive network.
[00011] Whereas there is certainly nothing wrong with existing techniques or methods or device used for short circuit fault detection, nonetheless, there still exists a need to provide an efficient, effective, reliable, improved and early short circuit detection systems and methods. Further, there exists a need short circuit detection method which recognizes the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault.
[00012] 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.
[00013] 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.
[00014] 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.
[00015] 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.
[00016] 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
[00017] An object of the present disclosure is to provide to a system and method for detection of short circuit fault.
[00018] Another object of the present disclosure is to provide a short circuit detection method that detects the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault.
[00019] Another object of the present disclosure is to provide an electrical fault detection system and method which reliably detects electrical faults, including information of level of fault ignored by conventional methods.
[00020] Another object of the present disclosure is to provide a system and method for short circuit detection in power system.
[00021] Another object of the present disclosure is to provide a system and method in which current peak is predicted before it actually reaches to its original peak.
[00022] Another object of the present disclosure is to provide a system and method is capable of detecting the current level precisely even with capacitor switching and nonlinear loads.
[00023] Another object of the present disclosure is to provide high performance DSP micro controller that allows high end processing for sophisticated control logic and thus leads to reliable fault detection.
SUMMARY
[00024] The present disclosure relates to the short circuit fault detection, and more specifically relates to, but not by way of limitation, a system and method that enables to detect of short-circuit fault conditions in an electrical network, as well as to a device which uses this method.
[00025] Embodiments of the present disclosure provide an efficient, effective, reliable, improved and early short circuit detection systems and methods. Further, the short circuit detection method according to the embodiments recognizes the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault.
[00026] Accordingly, an aspect of the present disclosure relates to a method for early short circuit detection in an electrical network. The method for early short circuit detection in an electrical network can include the steps of: receiving a current signal sample; processing, at said Rogowski coil, the current signal sample to output derivative of the current signal sample at a Rogowski coil that is configured as a current sensor in said electrical network, numerically integrating the derivative of the current signal sample to obtain integrated current signal at an integrator, processing the integrated current signal to calculate estimated peak of the current signal at a processing block, and comparing the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value at a main processing unit. In an aspect, said detection flag being representative of a potential short circuit.
[00027] In an aspect, the potential short circuit can be confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
[00028] In an aspect, upon said potential short circuit being confirmed, a trip signal can be issued by a tripping unit.
[00029] In an aspect, the estimated peak of the current signal can be calculated as:
[00030] In an aspect, the estimated peak of the current signal can be calculated using N point regression.
[00031] In an aspect, the estimated peak of the current signal can be further refined through Newton Raphson iterative technique, said Newton Raphson technique being processed based on point on wave.
[00032] In an aspect, wherein prior to the step of numerically integrating, the method performs high frequency filtering of the derivative of the current signal sample, followed by digitizing said filtered current signal sample.
[00033] An aspect of the present disclosure relates to a circuit breaker. In an aspect, the circuit breaker can include a Rogowski coil, an integrator, a processing block and a main processing unit. In another aspect, the Rogowski coil can be configured as a current sensor to receive a current signal sample, and process the current signal sample to output derivative of the current signal sample. In another aspect, the integrator can be configured to numerically integrate the derivative of the current signal sample to obtain integrated current signal. In another aspect, the processing block can be configured to process the integrated current signal to calculate estimated peak of the current signal. In another aspect, a main processing unit can be configured to compare the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value, said detection flag being representative of a potential short circuit.
[00034] In an aspect, said potential short circuit can be confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
[00035] In an aspect, upon said potential short circuit being confirmed, a trip signal is issued by said tripping unit.
[00036] In an aspect, wherein said estimated peak of the current signal is further refined through Newton Raphson iterative technique, said Newton Raphson technique/equation being processed based on point on wave.
[00037] In contrast to the conventional short circuit detection methods, the present disclosure illustrates a short circuit detection method which recognizes the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault. Further, in contrast to the existing conventional short circuit detection methods, the present invention provides an improved short circuit detection scheme through a numerical analysis of the current signal, making it more reliable in short circuit detection. Unlike the existing approaches, the measured parameter is current which in turn eliminates the requirement of high end filtering in case of noisy input.
[00038] Further, in contrast to the existing conventional short circuit detection methods, the present invention involves mathematical iterative approach which also involves determination of current peak through regression method; used as initial guess in newton Raphson, considering transient system configuration to effectively determine the short circuit current peak by taking N successive samples of current i(t) to give trip command. The present invention is also is capable of estimating correct peak at the time of fault under various system configurations and with variety of loads like machines with high inrush currents etc.
[00039] 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
[00040] 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. The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:
[00041] FIG. 1 illustrates a schematic diagram of a power system network consisting RL load in short circuit condition, in accordance with an exemplary embodiment of the present disclosure.
[00042] FIG. 2 illustrates a block diagram for carrying out an embodiment of the method for short circuit detection, in accordance with an exemplary embodiment of the present disclosure.
[00043] FIG. 3 illustrates flowchart for the arrangement shown in FIG. 2, in accordance with an exemplary embodiment of the present disclosure.
DETAILED DESCRIPTION
[00044] 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 scope of the present disclosure as defined by the appended claims.
[00045] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[00046] 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.
[00047] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[00048] 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.
[00049] 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.
[00050] 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.
[00051] The present disclosure relates to the short circuit fault detection, and more specifically relates to, but not by way of limitation, a system and method that enables to detect of short-circuit fault conditions in an electrical network, as well as to a device which uses this method.
[00052] Embodiments of the present disclosure provide an efficient, effective, reliable, improved and early short circuit detection systems and methods. Further, the short circuit detection method according to the embodiments recognizes the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault.
[00053] Accordingly, an aspect of the present disclosure relates to a method for early short circuit detection in an electrical network. The method for early short circuit detection in an electrical network can include the steps of: receiving a current signal sample; processing, at said Rogowski coil, the current signal sample to output derivative of the current signal sample at a Rogowski coil that is configured as a current sensor in said electrical network, numerically integrating the derivative of the current signal sample to obtain integrated current signal at an integrator, processing the integrated current signal to calculate estimated peak of the current signal at a processing block, and comparing the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value at a main processing unit. In an aspect, said detection flag being representative of a potential short circuit.
[00054] In an aspect, the potential short circuit can be confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
[00055] In an aspect, upon said potential short circuit being confirmed, a trip signal can be issued by a tripping unit.
[00056] In an aspect, the estimated peak of the current signal can be calculated as:
[00057] In an aspect, the estimated peak of the current signal can be calculated using N point regression.
[00058] In an aspect, the estimated peak of the current signal can be further refined through Newton Raphson iterative technique, said Newton Raphson technique being processed based on point on wave.
[00059] In an aspect, wherein prior to the step of numerically integrating, the method performs high frequency filtering of the derivative of the current signal sample, followed by digitizing said filtered current signal sample.
[00060] An aspect of the present disclosure relates to a circuit breaker. In an aspect, the circuit breaker can include a Rogowski coil, an integrator, a processing block and a main processing unit. In another aspect, the Rogowski coil can be configured as a current sensor to receive a current signal sample, and process the current signal sample to output derivative of the current signal sample. In another aspect, the integrator can be configured to numerically integrate the derivative of the current signal sample to obtain integrated current signal. In another aspect, the processing block can be configured to process the integrated current signal to calculate estimated peak of the current signal. In another aspect, a main processing unit can be configured to compare the estimated peak of the current signal with a threshold value to raise a detection flag when the estimated peak of the current signal is greater than the threshold value, said detection flag being representative of a potential short circuit.
[00061] In an aspect, said potential short circuit can be confirmed as a short circuit when detection flags are raised for N consecutive current signal samples.
[00062] In an aspect, upon said potential short circuit being confirmed, a trip signal is issued by said tripping unit.
[00063] In an aspect, wherein said estimated peak of the current signal is further refined through Newton Raphson iterative technique, said Newton Raphson technique/equation being processed based on point on wave.
[00064] In contrast to the conventional short circuit detection methods, the present disclosure illustrates a short circuit detection method which recognizes the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault. Further, in contrast to the existing conventional short circuit detection methods, the present invention provides an improved short circuit detection scheme through a numerical analysis of the current signal, making it more reliable in short circuit detection. Unlike the existing approaches, the measured parameter is current which in turn eliminates the requirement of high end filtering in case of noisy input.
[00065] Further, in contrast to the existing conventional short circuit detection methods, the present invention involves mathematical iterative approach which also involves determination of current peak through regression method; used as initial guess in newton Raphson, considering transient system configuration to effectively determine the short circuit current peak by taking N successive samples of current i(t) to give trip command. The present invention is also is capable of estimating correct peak at the time of fault under various system configurations and with variety of loads like machines with high inrush currents etc.
[00066] Furthermore, in contrast to the conventional system and method, the present invention provides a short circuit detection method that detects the fault at an early stage and gives a trip command to isolate the faulty system thereby eliminating the hazardous condition created by the fault. Further, present invention provides an electrical fault detection system and method which reliably detects electrical faults, including information of level of fault ignored by conventional methods. The availability of processors with high calculating capacity and the development of an algorithm capable of detecting the fault at early stage make it possible to obtain very high selectivity values, even when using molded-case circuit-breakers. Total selectivity can be accomplished between two circuit-breakers of the same size. On the contrary, when using the traditional method, the upstream circuit-breaker must be a larger size (thus implying larger overall dimensions) to guarantee selectivity. The present disclosure can include high performance micro controller and upgraded algorithm of short circuit detection to get more reliable and fast fault detection.
[00067] In contrast to the conventional system and method, the present invention provides a method and system for short circuit detection in power system. The electrical power system consists of so many different complex dynamic and interacting elements, which are always disposed to disturbance or an electrical fault. The use of high capacity electrical generating power plants and concept of grid required fault detection and operation of protection equipment in minimum possible time so that the power system can remain in stable condition. The faults on electrical power system are supposed to be first detected and then be classified correctly and should be cleared in least possible time a good fault detection system provides an effective, reliable, fast and secure way of a relaying operation.
[00068] In an aspect, the present invention provides an improved zone selective interlocking (ZSI) coordinated distribution system to limit fault stress on the system by reducing the time it takes to clear the fault.
[00069] In an aspect, the present invention provides a system and method that enables to predict current peak before it actually reaches to its original peak.
[00070] In an aspect, the present invention provides a system and method and apparatus or device with is an improved detection scheme where the predicted short circuit current peak from regression is then refined by a Newton Raphson iterative method. In case of noisy input signals peak estimation through regression alone would result in inaccurate prediction which may cause nuisance tripping in case of healthy conditions. The inclusion of Newton Raphson based iteration will further refine the predicted peak which leads to more accurate detection. High end processing is a necessity for implementation of such mathematical approach. Use of highly integrated and high-performance micro-controller makes it possible to perform the high end algorithm efficiently.
[00071] FIG. 1 illustrates a schematic diagram of a power system network consisting RL load in short circuit condition, in accordance with an exemplary embodiment of the present disclosure. As shown in FIG. 1 a schematic diagram of the power system network can include RL load 4 along with fault taking place at load side 5. A circuit breaker is provided with an electronic tripping unit 2. The RL network 3 represents the line impedance which is responsible for the fault power factor.
[00072] The differential equations for switching-on process of the single-phase RL circuit at a given frequency ? can be derived from the equivalent circuit at a rated voltage (root mean square value) v as a function of the time t:
[00073] The above system equation can be solved for current which is given as:
[00074] As the short circuit power factor is considered to be 0.9 or higher power factor range, the above equation can be solved as differential equation to find out Ip i.e. peak of the current value and point on wave (?). These values further refined with iterative mathematical approach here newton Raphson method is used. Algebraic equations for multi-variate newton Raphson can be written as:
Where X= (x1,…….,xn) is an n-dimensional vector. In proposed invention digitized current signal is represented as the function of its peak, power factor, and point on wave. The Newton-Raphson formula for multi-variate problem is:
Where Jf (X) is the Jacobian of function F(x):
[00075] FIG. 2 illustrates a block diagram for carrying out an embodiment of the method for short circuit detection, in accordance with an exemplary embodiment of the present disclosure. FIG. 2 illustrates the block diagram for carrying out the method for early short circuit detection in an electrical network.
[00076] In an embodiment, the Rogowski coil 5 can be preferably used as a current sensor that outputs derivative of current signal. The output signal from the Rogowski coil 5 can be digitized by an A/D converter 5A. The output signal from the A/D converter 5A can be numerically integrated by an integrator 6 to obtain the current signal (i(t)). Obtained signal sequence then fed to the processing block 7 and the calculation of estimated peak is carried out which further act as input to the main processing unit 8 and detection flag is raised when the calculated peak exceeds the threshold. Flag rising is preliminary information of the fault so the trip signal is issued when the condition is satisfied for N consecutive samples. The evaluation of current peak can be carried out within processing block 7 using the formula given by the following equation which further refined through Newton Raphson and the trip signal is issued by the tripping unit 9:
[00077] FIG. 3 illustrates flowchart for the arrangement shown in FIG. 2, in accordance with an exemplary embodiment of the present disclosure. In an exemplary embodiment, The Rogowski coil 5 can be used as current sensor which produces derivative of current as the output. High frequency filtering is carried out 10 prior to the digitizing process to compensate for the errors introduced in data acquisition process thus allowing accurate detection with industrial loads fed from converters/inverters. The filtered signal can be then integrated by numerical or digital integrator to get the current signal and further digitized by an A/D converter 11 for controller processing. Thus the detection algorithm is closely associated with the digital interface.
[00078] The proposed algorithm computes initial guess value for the current peak using N point regression or any other mathematical approach 12. The estimated current peak and point on wave (?) becomes the input variables for Newton Raphson 13 which intends to compute the short circuit peak in n (n=5) number of iterations by achieving convergence thresholds.
[00079] The next instant value of current is estimated with converged peak and ? from newton Raphson and then compared with the instantaneous current sample to compute the error Err as shown in block 14. The error is an indication of the accuracy of the predicted peak. Depending upon which threshold criteria Err meets defines the further course of action. If Err meets criteria1 (Err > TH1) then both initial guess and NR has to take place. If Err meets criteria 2 (Err > TH2 & Err < TH1) then only NR has to take place. Thus, the algorithm eliminates the need to perform the entire process at every instant of time thereby reducing the short circuit detection time. If Err meets criteria 3 (Err
Documents
Application Documents
#
Name
Date
1
201821012217-STATEMENT OF UNDERTAKING (FORM 3) [31-03-2018(online)]_50.pdf
2018-03-31
2
201821012217-STATEMENT OF UNDERTAKING (FORM 3) [31-03-2018(online)].pdf
2018-03-31
3
201821012217-REQUEST FOR EXAMINATION (FORM-18) [31-03-2018(online)]_44.pdf
2018-03-31
4
201821012217-REQUEST FOR EXAMINATION (FORM-18) [31-03-2018(online)].pdf
2018-03-31
5
201821012217-FORM 18 [31-03-2018(online)].pdf
2018-03-31
6
201821012217-FORM 1 [31-03-2018(online)]_35.pdf
2018-03-31
7
201821012217-FORM 1 [31-03-2018(online)].pdf
2018-03-31
8
201821012217-DRAWINGS [31-03-2018(online)]_61.pdf
2018-03-31
9
201821012217-DRAWINGS [31-03-2018(online)].pdf
2018-03-31
10
201821012217-DECLARATION OF INVENTORSHIP (FORM 5) [31-03-2018(online)].pdf