Design method and system for fault current measurement CT integrating energy acquisition and measurement

Abstract

The present invention discloses a design method and system for a fault current measurement CT that integrates energy collection and measurement. This system isolates the current sampling and power collection modules by cascading a large CT and a small CT. The CT system designed with this method offers the advantages of small size, low cost, high power collection efficiency, and non-interference between power collection and current measurement. It can be applied in scenarios where fault current measurement of transmission and distribution lines is required but conventional power supply access is inconvenient. By using electromagnetic induction in the CT to supply power to the fault current detection device, the system also accurately measures the fault current, demonstrating high practical and economic value.

Description

Technical Field

[0001] The present invention relates to the field of electrical automation technology, and in particular to a design method and system for a fault current measurement CT integrating energy acquisition and measurement. Background Art

[0002] Currently, grounding and short-circuit faults frequently occur in distribution lines, especially overhead lines, posing a threat to the safe and stable operation of the distribution network and the normal production and life of the people. To accurately identify the type and location of the fault, enabling timely troubleshooting and power restoration, a fault current detection and indication device (FID) is required. The FID is a key component of the FID, and its measurement accuracy and reliability directly impact the precision and accuracy of fault diagnosis. Because overhead distribution lines are typically high-voltage, ranging from 6 to 35 kV, and lack 220V / 380V mains power, the self-powered FID must be addressed.

[0003] The current mainstream technology is to use a separate power supply CT and a separate measurement CT to respectively realize the power supply and fault current measurement of the fault current detection and indication device. This method has high current sampling accuracy and good power supply effect, but has the problems of high cost and large power supply structure volume. In order to save cost and space, there is also a single CT that is used to time-share multiplex the functions of the power supply CT and the measurement CT through the control circuit. This method has the problems of discontinuous power supply, which affects the power supply efficiency, discontinuous CT sampling, and easy leakage of fault current. There is also a single CT core with two sets of coils wound on it, one set of coils is used for power supply, and the other set of coils is used for current measurement. This structure has the problem of mutual influence between power supply and current measurement, and the power supply process will affect the accuracy of current measurement. Summary of the Invention

[0004] In response to the problems shown above, the present invention provides a fault current measurement CT design method and system that integrates energy collection and measurement to solve the problems mentioned in the background technology, such as discontinuous power collection, which affects the power collection efficiency, discontinuous CT sampling, and easy leakage of fault current. At the same time, the power collection process affects the accuracy of current measurement.

[0005] A method for designing a fault current measurement CT that integrates energy extraction and measurement includes the following steps:

[0006] Design an integrated structure of a large CT and a small CT, and determine the connection relationship between each working module in the integrated structure based on power supply and measurement characteristics;

[0007] Modeling and analysis of large CT to determine the relationship between output power and core material and core structure size;

[0008] The optimal structure size and preferred core material of the large CT are determined based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirements of the current measurement module circuit;

[0009] The influence factor of power-taking performance on current measurement is calculated based on the optimal structural dimensions, the optimal structural dimensions are adjusted according to the influence factor, and the design parameters are generated based on the adjusted structural dimensions and the preferred magnetic core material for CT design.

[0010] Preferably, the design of an integrated structure of a large CT and a small CT, and determining the connection relationship of each working module in the integrated structure according to power supply and measurement characteristics, includes:

[0011] Determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with a small CT based on the working module group;

[0012] Determine the functional characteristics of the large CT and the small CT respectively, and determine the connection relationship of each working module in the integrated structure based on the functional characteristics and power supply and measurement characteristics;

[0013] Among them, the primary circuit of the large CT is connected to the power line under test, which is used to sense the current size of the measured line and transmit electric energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power supply module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power supply module circuit converts the large CT current into a stable voltage and power output to provide stable electric energy for the current measurement circuit module.

[0014] Preferably, the modeling and analysis of the large CT to determine the relationship between output power and the core material and core structure size includes:

[0015] Construct a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram:

[0016] E2=4.44fN2φ m

[0017] Among them, E2 represents the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, f represents the current frequency of the transmission line, N2 represents the number of turns of the secondary side of the power coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil;

[0018] According to the full current law equation, the magnetomotive force balance equation and the instantaneous output voltage of the secondary side of the power coil when the core is not saturated, the output power of the power coil after ignoring the hysteresis loss component of the core is determined;

[0019] The output power is expressed as a variable parameter related to the output power, and the relationship between the output power magnetic core material and the magnetic core structure size is determined according to the variable parameter.

[0020] Preferably, the determining of the optimal structural dimensions and preferred magnetic core material of the large CT based on the relationship between the output power of the large CT and the magnetic core material and the magnetic core structural dimensions in combination with the power requirements of the current measurement module circuit includes:

[0021] Obtain the saturation magnetic induction intensity and saturation current parameters of magnetic cores of different materials, and determine the effective cross-sectional coefficient of magnetic cores of different materials based on the saturation magnetic induction intensity and saturation current parameters;

[0022] Determine the expected cross-sectional coefficient for the core material based on the power requirements of the current measurement module circuit. Select the optimal core material based on the expected cross-sectional coefficient, effective cross-sectional coefficient, and the relationship between the maximum CT output power, core material, and core structure dimensions.

[0023] Determine the core cross-sectional parameters of the optimal core material according to the rated current parameters, the overload current multiple, and the target saturation current parameters of the optimal core material;

[0024] The optimal structural dimensions of the large CT are determined based on the core cross-sectional parameters.

[0025] Preferably, the method of calculating the influence factor of the power-taking performance on the current measurement according to the optimal structural dimensions, adjusting the optimal structural dimensions according to the influence factor, and generating design parameters for CT design according to the adjusted structural dimensions and the preferred magnetic core material includes:

[0026] Determine the magnetic induction intensity amplitude required for large CT operation based on the optimal structural dimensions, determine the magnetic field intensity amplitude based on the magnetic induction intensity amplitude, and determine the maximum energy current based on the magnetic field intensity amplitude;

[0027] Determine the maximum power consumption that can be provided by the power supply based on the maximum current of the power supply, and calculate the quotient of the maximum power consumption that can be provided by the power supply and the load power consumption of the measured circuit;

[0028] If the quotient is greater than 1, it is confirmed that there is an impact. If the quotient is less than 1, it is confirmed that there is no impact. According to the confirmation result, the optimal structural size is proportionally reduced and the calculation is repeated until there is no impact.

[0029] The adjusted structural dimensions are obtained and design parameters are generated based on the adjusted structural dimensions and the preferred magnetic core material for CT design.

[0030] A fault current measurement CT design system integrating energy acquisition and measurement, the system comprising:

[0031] The first determination module is used to design an integrated structure of a large CT and a small CT, and determine the connection relationship between the working modules in the integrated structure based on power supply and measurement characteristics;

[0032] Analysis module, used to model and analyze large CT to determine the relationship between output power and core material and core structure size;

[0033] The second determination module is used to determine the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirement of the current measurement module circuit;

[0034] The generation module is used to calculate the influence factor of power-taking performance on current measurement based on the optimal structural dimensions, adjust the optimal structural dimensions according to the influence factor, and generate design parameters for CT design based on the adjusted structural dimensions and the preferred magnetic core material.

[0035] Preferably, the first determining module includes:

[0036] Design submodules to determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with small CTs based on the working module group;

[0037] The first determination submodule is used to determine the functional characteristics of the large CT and the small CT respectively, and determine the connection relationship between the working modules in the integrated structure according to the functional characteristics and the power supply and measurement characteristics;

[0038] Among them, the primary circuit of the large CT is connected to the power line under test, which is used to sense the current size of the measured line and transmit electric energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power supply module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power supply module circuit converts the large CT current into a stable voltage and power output to provide stable electric energy for the current measurement circuit module.

[0039] Preferably, the analysis module includes:

[0040] The second determination submodule is used to build a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram:

[0041] E2=4.44fN2φ m

[0042] Among them, E2 represents the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, f represents the current frequency of the transmission line, N2 represents the number of turns of the secondary side of the power coil, φm It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil;

[0043] The third determination submodule is used to determine the output power representation of the power taking coil after ignoring the hysteresis loss component of the magnetic core based on the full current law equation, the magnetomotive force balance equation, and the instantaneous output voltage of the secondary side of the power taking coil when the magnetic core is not saturated;

[0044] The fourth determining submodule is configured to determine variable parameters related to the output power according to the output power representation, and determine a relationship between the output power magnetic core material and the magnetic core structure size according to the variable parameters.

[0045] Preferably, the second determining module includes:

[0046] The fifth determination submodule is used to obtain the saturation magnetic induction intensity and saturation current parameters of the magnetic cores of different materials, and determine the effective cross-sectional coefficient of the magnetic cores of different materials according to the saturation magnetic induction intensity and saturation current parameters;

[0047] A screening submodule is used to determine the expected cross-sectional coefficient of the material core according to the power requirement of the current measurement module circuit, and to screen the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the maximum CT output power and the core material and core structure size;

[0048] a sixth determination submodule, configured to determine a core cross-sectional parameter of an optimal core material according to a rated current parameter, an overload current multiple, and a target saturation current parameter of the optimal core material;

[0049] The seventh determination submodule is used to determine the optimal structural size of the large CT according to the core cross-sectional parameters.

[0050] Preferably, the generating module includes:

[0051] an eighth determination submodule, configured to determine a magnetic induction intensity amplitude required for operation of the large CT according to the optimal structural dimensions, determine a magnetic field intensity amplitude according to the magnetic induction intensity amplitude, and determine a maximum energy extraction current based on the magnetic field intensity amplitude;

[0052] A calculation submodule is used to determine the maximum power consumption that can be provided by the power supply according to the maximum current of the power supply, and calculate the quotient of the maximum power consumption that can be provided by the power supply and the load power consumption of the measured circuit;

[0053] An adjustment submodule is used to confirm that there is an impact if the quotient is greater than 1, and to confirm that there is no impact if the quotient is less than 1, and to adjust the optimal structural dimensions proportionally based on the confirmation result and repeat the calculation until there is no impact;

[0054] The generation submodule is used to obtain the adjusted structural dimensions and generate design parameters based on the adjusted structural dimensions and the preferred magnetic core material for CT design.

[0055] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0056] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0058] Figure 1 A flowchart of a design method for a fault current measurement CT with integrated energy extraction and measurement provided by the present invention;

[0059] Figure 2 Another workflow diagram of the method for designing a fault current measurement CT with integrated energy acquisition and measurement provided by the present invention;

[0060] Figure 3 This is a structural diagram of a fault current measurement CT design system with integrated energy acquisition and measurement provided by the present invention;

[0061] Figure 4 This is a structural diagram of a generation module in a fault current measurement CT design system with integrated energy acquisition and measurement provided by the present invention. DETAILED DESCRIPTION

[0062] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0063] Currently, grounding and short-circuit faults frequently occur in distribution lines, especially overhead lines, posing a threat to the safe and stable operation of the distribution network and the normal production and life of the people. To accurately identify the type and location of the fault, enabling timely troubleshooting and power restoration, a fault current detection and indication device (FID) is required. The FID is a key component of the FID, and its measurement accuracy and reliability directly impact the precision and accuracy of fault diagnosis. Because overhead distribution lines are typically high-voltage, ranging from 6 to 35 kV, and lack 220V / 380V mains power, the self-powered FID must be addressed.

[0064] The current mainstream technology uses a separate power supply CT and a separate measurement CT to respectively realize the power supply of the fault current detection and indication device and the measurement of the fault current. This method has high current sampling accuracy and good power supply effect, but it has the problems of high cost and large power supply structure volume. In order to save cost and space, there is also a single CT that uses time-sharing to multiplex the functions of the power supply CT and the measurement CT through the control circuit. This method has the problems of discontinuous power supply, which affects the power supply efficiency, discontinuous CT sampling, and easy leakage of fault current. There is also a single CT core with two sets of coils wound on it, one set of coils is used for power supply, and the other set of coils is used for current measurement. This structure has the problem of mutual influence between power supply and current measurement, and the power supply process will affect the accuracy of current measurement. To solve the above problems, this embodiment discloses a design method for a fault current measurement CT that integrates energy supply and measurement.

[0065] A design method for fault current measurement CT integrating energy acquisition and measurement, such as Figure 1 As shown, the following steps are included:

[0066] Step S101: Design an integrated structure of a large CT and a small CT, and determine the connection relationship of each working module in the integrated structure based on power supply and measurement characteristics;

[0067] Step S102: Modeling and analyzing the large CT to determine the relationship between output power and the core material and core structure size;

[0068] Step S103: determining the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirement of the current measurement module circuit;

[0069] Step S104: Calculate the influence factor of the power extraction performance on the current measurement according to the optimal structural dimensions, adjust the optimal structural dimensions according to the influence factor, and generate design parameters according to the adjusted structural dimensions and the preferred magnetic core material to perform CT design.

[0070] In this embodiment, the primary large CT is an open through-core structure, which is convenient for installation and removal. The installation and removal are live installations, which do not affect the normal operation of the transmission line. The small CT is a closed through-core structure.

[0071] In this embodiment, the magnetic core material of the small CT is an ultra-fine crystal alloy with good linearity and low saturation resistance;

[0072] The working principle of the above technical solution is as follows: an integrated structure of a large CT and a small CT is designed. The connection relationship between the various working modules in the integrated structure is determined based on the power supply and measurement characteristics. The primary circuit of the large CT is connected to the power line under test, sensing the current in the measured line and transferring power to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input of the current sampling module. The secondary circuit of the small CT is connected to the input of the current measurement circuit module. After processing by the current measurement circuit module, it is used for power line fault analysis. The current sampling module converts the large CT current into a stable voltage and power output to provide stable power to the current measurement circuit module. The small CT functions to isolate the current sampling module and the current measurement module to prevent direct interference between the two. The small CT is small in size and can be integrated within the fault current measurement device.

[0073] The beneficial effects of the above technical solution are as follows: by cascading a large CT and a small CT, the large CT serves as both a power supply and current measurement device, while the small CT serves as a secondary current signal transmission and isolation device, further reducing the large current signal to a small current signal while isolating the power supply circuit from the current measurement circuit. Power supply and measurement share the same large CT, and power supply and current measurement can be performed simultaneously without interfering with each other. This ensures maximum utilization of CT power supply energy while ensuring the continuity and accuracy of current sampling. This solves the problems of discontinuous power supply in traditional technologies, which affects power supply efficiency, and discontinuous CT sampling, which easily misses fault currents and affects the accuracy of current measurement.

[0074] In one embodiment, the design of an integrated structure of a large CT and a small CT, and determining the connection relationship between the working modules in the integrated structure based on power supply and measurement characteristics, includes:

[0075] Determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with a small CT based on the working module group;

[0076] Determine the functional characteristics of the large CT and the small CT respectively, and determine the connection relationship of each working module in the integrated structure based on the functional characteristics and power supply and measurement characteristics;

[0077] Among them, the primary circuit of the large CT is connected to the power line under test, which is used to sense the current size of the measured line and transmit electric energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power supply module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power supply module circuit converts the large CT current into a stable voltage and power output to provide stable electric energy for the current measurement circuit module.

[0078] The beneficial effects of the above technical solution are: it can ensure the working stability of each working module while also ensuring the mutual working compatibility between the modules, thereby improving the overall stability and reliability.

[0079] In one embodiment, the modeling and analysis of the large CT to determine the relationship between output power and the core material and core structure size includes:

[0080] Construct a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram:

[0081] E2=4.44fN2φ m

[0082] Among them, E2 represents the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, f represents the current frequency of the transmission line, N2 represents the number of turns of the secondary side of the power coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil;

[0083] According to the full current law equation, the magnetomotive force balance equation and the instantaneous output voltage of the secondary side of the power coil when the core is not saturated, the output power of the power coil after ignoring the hysteresis loss component of the core is determined;

[0084] The output power is expressed as a variable parameter related to the output power, and the relationship between the output power magnetic core material and the magnetic core structure size is determined according to the variable parameter.

[0085] In this embodiment, according to the full current law equation:

[0086] φ m =B m S=uH m S

[0087]

[0088] Among them, B m It is expressed as the amplitude of the magnetic induction intensity in the core of the power coil, H mIt represents the amplitude of the magnetic field strength in the core of the power coil, S represents the cross-sectional area of ​​the core of the power coil, u represents the magnetic permeability of the core, l represents the magnetic path length of the core of the power coil, N1 represents the number of turns of the primary side of the power coil, which can be considered as 1 turn, I u Expressed as the effective value of the magnetizing current of the power coil;

[0089] According to the magnetomotive force balance equation:

[0090] I1N1+I2N2=I m N1

[0091] I1 is the effective value of the transmission line current, I2 is the effective value of the secondary output current of the power coil, and I m is the effective value of the excitation current of the power coil. m It is divided into two parts, one of which is the magnetization component I that is in phase with the core. u The other part is the hysteresis loss component I which is in phase with the instantaneous output voltage of the secondary side of the voltage-taking coil when the core is not saturated. fe ;

[0092] Then, after neglecting the hysteresis loss component of the magnetic core, the output power of the power coil is expressed as:

[0093]

[0094] From the above formula, it can be seen that the output power of the power coil is only related to the magnetic permeability of the magnetic core, the cross-sectional area of ​​the magnetic core, the length of the magnetic path, and the magnitude and frequency of the primary side current, and has nothing to do with the number of turns of the secondary coil.

[0095] The beneficial effect of the above technical solution is that the relationship between the output power core material and the core structure size can be accurately determined based on the working characteristic equation of the power taking coil, and then the size design and material selection can be quickly carried out, ensuring the working stability of the power taking coil.

[0096] In one embodiment, determining the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size in combination with the power requirement of the current measurement module circuit includes:

[0097] Obtain the saturation magnetic induction intensity and saturation current parameters of magnetic cores of different materials, and determine the effective cross-sectional coefficient of magnetic cores of different materials based on the saturation magnetic induction intensity and saturation current parameters;

[0098] Determine the expected cross-sectional coefficient for the core material based on the power requirements of the current measurement module circuit. Select the optimal core material based on the expected cross-sectional coefficient, effective cross-sectional coefficient, and the relationship between the maximum CT output power, core material, and core structure dimensions.

[0099] Determine the core cross-sectional parameters of the optimal core material according to the rated current parameters, the overload current multiple, and the target saturation current parameters of the optimal core material;

[0100] The optimal structural dimensions of the large CT are determined based on the core cross-sectional parameters.

[0101] The beneficial effects of the above technical solution are: by selecting the magnetic core material according to the effective cross-sectional coefficient, the magnetic core material with the least impact can be selected based on the level of influence of the excitation current brought by the saturation magnetic induction intensity of the magnetic cores of different materials on the power supply, thereby ensuring the stability and reliability of the overall operation. Furthermore, by determining the core cross-sectional parameters of the optimal magnetic core material based on the rated current parameters, the overload current multiple and the target saturation current parameters of the optimal magnetic core material, the power supply and measurement synchronization process can be realized while ensuring that the magnetic core is not saturated, thereby improving the working stability and practicality.

[0102] In one embodiment, Figure 2 As shown, the method of calculating the influence factor of the power-taking performance on the current measurement according to the optimal structural dimensions, adjusting the optimal structural dimensions according to the influence factor, and generating design parameters for CT design according to the adjusted structural dimensions and the preferred magnetic core material includes:

[0103] Step S201: determining the magnetic induction intensity amplitude required for the operation of the large CT according to the optimal structural dimensions, determining the magnetic field intensity amplitude according to the magnetic induction intensity amplitude, and determining the maximum energy extraction current based on the magnetic field intensity amplitude;

[0104] Step S202: Determine the maximum power consumption that can be provided by the power supply according to the maximum current of the power supply, and calculate the quotient of the maximum power consumption that can be provided by the power supply and the load power consumption of the measured circuit;

[0105] Step S203: If the quotient is greater than 1, it is confirmed that there is an impact; if the quotient is less than 1, it is confirmed that there is no impact, and the optimal structural dimensions are proportionally reduced and adjusted according to the confirmation result and the calculation is repeated until there is no impact;

[0106] Step S204: Obtain the adjusted structural dimensions and generate design parameters based on the dimensions and the preferred magnetic core material to perform CT design.

[0107] In this embodiment, it is assumed that the core cross section is S=10*10mm 2 =10 -4 m 2 , in order to adapt to 35mm 2 Up to 300mm 2 For the transmission and distribution cables, taking into account the structural shell, the inner diameter d = 50mm and the outer diameter D = 70mm of the ring core are designed. Then:

[0108] Average magnetic path length l = 2πR = 0.1885m

[0109] Number of turns = 1000 (turns);

[0110] Vacuum magnetic permeability u0=4π*10 -7 H / m;

[0111] Permalloy magnet relative permeability u r =17000

[0112] Initial magnetic permeability u of Permalloy magnet i =u0*u r =0.021H / m;

[0113] After testing, the starting voltage is about 1.55V, the current is 280uA, and the power is 1.55*280uW=0.434mW.

[0114] Considering that the MPPT of the energy extraction circuit is set to 80% of the open circuit voltage, the open circuit voltage (assuming that all the primary current is used for excitation) is 1.55V / 80%=2V, ​​then the magnetic induction intensity amplitude is:

[0115]

[0116] Then the magnetic field strength is:

[0117]

[0118] The required excitation current is:

[0119]

[0120] If the primary current is 5A, minus the excitation current, then:

[0121]

[0122] Then the secondary current is

[0123]

[0124] This shows that the maximum current that can be extracted by the secondary energy extraction is 4.9674mA, and the power available is: 4.9674 * 2mW = 9.9348mW, which is much greater than the load power consumption of 0.434mW. The quotient of the two is greater than 1, confirming that the excitation current required for energy extraction has little impact on the measurement. As the primary current continues to increase, while the power consumption required for energy extraction remains unchanged, the required excitation current increases very little. Therefore, as the primary current increases, the impact of energy extraction on accuracy decreases as long as the magnetic core is not saturated, indicating that the impact of energy extraction on current measurement accuracy can be ignored.

[0125] The beneficial effects of the above technical solution are: it can reasonably, effectively and reliably evaluate the influence of the power-drawing effect brought by the magnetic core structure on the current measurement, thereby ensuring the rationality of the design of the magnetic core structure. At the same time, it ensures that the CT has a low cost and structural size, can meet the requirements of power drawing and current measurement at the same time, and power drawing does not affect the current measurement accuracy, further improving practicality.

[0126] In one embodiment, this embodiment also discloses a fault current measurement CT design system integrating energy acquisition and measurement, such as Figure 3 As shown, the system includes:

[0127] The first determination module 301 is used to design an integrated structure of a large CT and a small CT, and determine the connection relationship between the working modules in the integrated structure based on power supply and measurement characteristics;

[0128] An analysis module 302 is used to perform modeling analysis on the large CT to determine the relationship between output power and the core material and core structure size;

[0129] A second determination module 303 is configured to determine the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirement of the current measurement module circuit;

[0130] The generation module 304 is used to calculate the influence factor of the power extraction performance on the current measurement according to the optimal structural dimensions, adjust the optimal structural dimensions according to the influence factor, and generate design parameters according to the adjusted structural dimensions and the preferred magnetic core material to perform CT design.

[0131] The working principle and beneficial effects of the above technical solution have been explained in the method embodiment and will not be repeated here.

[0132] In one embodiment, the first determining module includes:

[0133] Design submodules to determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with small CTs based on the working module group;

[0134] The first determination submodule is used to determine the functional characteristics of the large CT and the small CT respectively, and determine the connection relationship between the working modules in the integrated structure according to the functional characteristics and the power supply and measurement characteristics;

[0135] Among them, the primary circuit of the large CT is connected to the power line under test, which is used to sense the current size of the measured line and transmit electric energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power supply module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power supply module circuit converts the large CT current into a stable voltage and power output to provide stable electric energy for the current measurement circuit module.

[0136] In one embodiment, the analysis module includes:

[0137] The second determination submodule is used to build a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram:

[0138] E2=4.44fN2φ m

[0139] Among them, E2 represents the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, f represents the current frequency of the transmission line, N2 represents the number of turns of the secondary side of the power coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil;

[0140] The third determination submodule is used to determine the output power representation of the power taking coil after ignoring the hysteresis loss component of the magnetic core based on the full current law equation, the magnetomotive force balance equation, and the instantaneous output voltage of the secondary side of the power taking coil when the magnetic core is not saturated;

[0141] The fourth determining submodule is configured to determine variable parameters related to the output power according to the output power representation, and determine a relationship between the output power magnetic core material and the magnetic core structure size according to the variable parameters.

[0142] In one embodiment, the second determining module includes:

[0143] The fifth determination submodule is used to obtain the saturation magnetic induction intensity and saturation current parameters of the magnetic cores of different materials, and determine the effective cross-sectional coefficient of the magnetic cores of different materials according to the saturation magnetic induction intensity and saturation current parameters;

[0144] A screening submodule is used to determine the expected cross-sectional coefficient of the material core according to the power requirement of the current measurement module circuit, and to screen the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the maximum CT output power and the core material and core structure size;

[0145] a sixth determination submodule, configured to determine a core cross-sectional parameter of an optimal core material according to a rated current parameter, an overload current multiple, and a target saturation current parameter of the optimal core material;

[0146] The seventh determination submodule is used to determine the optimal structural size of the large CT according to the core cross-sectional parameters.

[0147] In one embodiment, Figure 4 As shown, the generating module 304 includes:

[0148] An eighth determination submodule 3041 is configured to determine the magnetic induction intensity amplitude required for operation of the large CT according to the optimal structural dimensions, determine the magnetic field intensity amplitude according to the magnetic induction intensity amplitude, and determine the maximum energy extraction current based on the magnetic field intensity amplitude;

[0149] A calculation submodule 3042 is configured to determine the maximum power consumption that can be provided by the power supply according to the maximum current of the power supply, and calculate the quotient of the maximum power consumption that can be provided by the power supply and the load power consumption of the measured circuit;

[0150] An adjustment submodule 3043 is configured to determine if the quotient is greater than 1, that there is an impact, and if the quotient is less than 1, that there is no impact, and to adjust the optimal structural dimensions proportionally based on the confirmation result and repeat the calculation until there is no impact;

[0151] The generating submodule 3044 is used to obtain the adjusted structural dimensions and generate design parameters according to the adjusted structural dimensions and the preferred magnetic core material to perform CT design.

[0152] Those skilled in the art should understand that the first and second in the present invention simply refer to different application stages.

[0153] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow from the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

[0154] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A design method for a fault current measurement CT integrating energy extraction and measurement, characterized in that: The following steps are involved: Design an integrated structure of a large CT and a small CT, and determine the connection relationship between each working module in the integrated structure based on power supply and measurement characteristics; Modeling and analysis of large CT to determine the relationship between output power and core material and core structure size; The optimal structure size and preferred core material of the large CT are determined based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirements of the current measurement module circuit; Calculate the influence factor of power-taking performance on current measurement based on the optimal structural dimensions, adjust the optimal structural dimensions based on the influence factor, and generate design parameters based on the adjusted structural dimensions and the preferred magnetic core material to design the CT; The primary circuit of the large CT is connected to the power line under test, used to sense the current of the measured line and transmit electrical energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power module circuit converts the large CT current into a stable voltage and power output to provide stable electrical energy for the current measurement circuit module. The method of calculating the influence factor of the power-taking performance on the current measurement according to the optimal structural dimensions, adjusting the optimal structural dimensions according to the influence factor, and generating design parameters for CT design according to the adjusted structural dimensions and the preferred magnetic core material includes: Determine the magnetic induction intensity amplitude required for large CT operation based on the optimal structural dimensions, determine the magnetic field intensity amplitude based on the magnetic induction intensity amplitude, and determine the maximum energy current based on the magnetic field intensity amplitude; Determine the maximum power consumption that can be provided by the power taking according to the maximum current of the power taking, and calculate the quotient of the maximum power consumption that can be provided by the power taking and the load power consumption of the current power taking module circuit; If the quotient is greater than 1, it is confirmed that there is no impact. If the quotient is less than 1, it is confirmed that there is an impact. According to the confirmation result, the optimal structural size is proportionally adjusted and the calculation is repeated until there is no impact. The adjusted structural dimensions are obtained and design parameters are generated based on the adjusted structural dimensions and the preferred magnetic core material for CT design.

2. The method for designing a fault current measurement CT integrating energy acquisition and measurement according to claim 1 is characterized in that: The design of an integrated structure of a large CT and a small CT, and determining the connection relationship of each working module in the integrated structure based on power supply and measurement characteristics, include: Determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with a small CT based on the working module group; The functional characteristics of the large CT and the small CT are determined respectively, and the connection relationship of each working module in the integrated structure is determined according to the functional characteristics and power supply and measurement characteristics.

3. The method for designing a fault current measurement CT integrating energy acquisition and measurement according to claim 1 is characterized in that: The modeling and analysis of the large CT to determine the relationship between output power and the core material and core structure size includes: Construct a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram: in, It is represented as the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, and f is represented as the current frequency of the transmission line. It is expressed as the number of turns of the secondary coil of the power taking coil. It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil; According to the full current law equation, the magnetomotive force balance equation and the instantaneous output voltage of the secondary side of the power coil when the core is not saturated, the output power of the power coil after ignoring the hysteresis loss component of the core is determined; The output power is expressed as a variable parameter related to the output power, and the relationship between the output power magnetic core material and the magnetic core structure size is determined according to the variable parameter.

4. The method for designing a fault current measurement CT integrating energy acquisition and measurement according to claim 1 is characterized in that: The method of determining the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size in combination with the power requirement of the current measurement module circuit includes: Obtain the saturation magnetic induction intensity and saturation current parameters of magnetic cores of different materials, and determine the effective cross-sectional coefficient of magnetic cores of different materials based on the saturation magnetic induction intensity; Determine the expected cross-sectional coefficient for the core material based on the power requirements of the current measurement module circuit. Select the optimal core material based on the expected cross-sectional coefficient, effective cross-sectional coefficient, and the relationship between the maximum CT output power, core material, and core structure dimensions. Determine the core cross-sectional parameters of the optimal core material according to the rated current parameters, the overload current multiple, and the target saturation current parameters of the optimal core material; The optimal structural dimensions of the large CT are determined based on the core cross-sectional parameters.

5. A fault current measurement CT design system integrating energy acquisition and measurement, characterized in that: The system includes: The first determination module is used to design an integrated structure of a large CT and a small CT, and determine the connection relationship between the working modules in the integrated structure based on power supply and measurement characteristics; Analysis module, used to model and analyze large CT to determine the relationship between output power and core material and core structure size; The second determination module is used to determine the optimal structure size and preferred core material of the large CT based on the relationship between the output power of the large CT and the core material and core structure size, combined with the power requirement of the current measurement module circuit; A generation module is used to calculate the influence factor of power-taking performance on current measurement based on the optimal structural dimensions, adjust the optimal structural dimensions based on the influence factor, and generate design parameters based on the adjusted structural dimensions and the preferred magnetic core material for CT design; The primary circuit of the large CT is connected to the power line under test, used to sense the current of the measured line and transmit electrical energy to the secondary circuit of the large CT. The secondary circuit of the large CT is connected in series with the primary circuit of the small CT and the input end of the current power module circuit. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module. After being processed by the current measurement circuit module, it is used for power line fault analysis. The current power module circuit converts the large CT current into a stable voltage and power output to provide stable electrical energy for the current measurement circuit module. The generation module includes: an eighth determination submodule, configured to determine a magnetic induction intensity amplitude required for operation of the large CT according to the optimal structural dimensions, determine a magnetic field intensity amplitude according to the magnetic induction intensity amplitude, and determine a maximum energy extraction current based on the magnetic field intensity amplitude; A calculation submodule, configured to determine the maximum power consumption that can be provided by the power taking according to the maximum current of the power taking, and calculate the quotient of the maximum power consumption that can be provided by the power taking and the load power consumption of the current power taking module circuit; An adjustment submodule is used to confirm that there is no impact if the quotient is greater than 1, and to confirm that there is an impact if the quotient is less than 1, and to adjust the optimal structural dimensions proportionally based on the confirmation result and repeat the calculation until there is no impact; The generation submodule is used to obtain the adjusted structural dimensions and generate design parameters based on the adjusted structural dimensions and the preferred magnetic core material for CT design.

6. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 5 is characterized in that: The first determining module includes: Design submodules to determine the working module group related to energy acquisition and measurement, and design an integrated structure of a large CT cascaded with small CTs based on the working module group; The first determination submodule is used to determine the functional characteristics of the large CT and the small CT respectively, and determine the connection relationship between the working modules in the integrated structure according to the functional characteristics and power supply and measurement characteristics.

7. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 5 is characterized in that: The analysis module includes: The second determination submodule is used to build a working model of the large CT, generate a working equivalent diagram of the large CT based on the working model, and determine the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated based on the working equivalent diagram: in, It is represented as the instantaneous output voltage of the secondary side of the power coil when the magnetic core is not saturated, and f is represented as the current frequency of the transmission line. It is expressed as the number of turns of the secondary coil of the power taking coil. It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power coil; The third determination submodule is used to determine the output power representation of the power taking coil after ignoring the hysteresis loss component of the magnetic core based on the full current law equation, the magnetomotive force balance equation, and the instantaneous output voltage of the secondary side of the power taking coil when the magnetic core is not saturated; The fourth determining submodule is configured to determine variable parameters related to the output power according to the output power representation, and determine a relationship between the output power magnetic core material and the magnetic core structure size according to the variable parameters.

8. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 5 is characterized in that: The second determining module includes: A fifth determination submodule is configured to obtain saturation magnetic induction and saturation current parameters of magnetic cores of different materials, and determine effective cross-sectional coefficients of magnetic cores of different materials according to the saturation magnetic induction; A screening submodule is used to determine the expected cross-sectional coefficient of the material core according to the power requirement of the current measurement module circuit, and to screen the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the maximum CT output power and the core material and core structure size; a sixth determination submodule, configured to determine a core cross-sectional parameter of an optimal core material according to a rated current parameter, an overload current multiple, and a target saturation current parameter of the optimal core material; The seventh determination submodule is used to determine the optimal structural size of the large CT according to the magnetic core cross-sectional parameters.

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