Fault current measurement CT design method and system integrating energy taking and measurement

Abstract

The invention discloses an energy taking and measurement integrated fault current measurement CT design method and system. A current sampling module and an electricity taking module are isolated through a large CT and small CT cascading method. The CT system designed through the method has the advantages of being small in size, low in cost, high in electricity taking efficiency and free of mutual interference between electricity taking and current measurement, can be applied to a scene where the power transmission and distribution line fault current needs to be measured and a conventional power supply is inconvenient to access, obtains electric energy through electromagnetic induction of the CT and supplies the electric energy to a fault current detection device, meanwhile, the fault current is accurately tested, and the fault detection accuracy is improved. The method has high practical value 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] At present, grounding and short-circuit faults frequently occur in distribution lines, especially overhead lines, posing a safety threat to the safe and stable operation of the distribution network and the normal production and life of the people. In order to accurately identify the type and location of the fault so as to eliminate the fault in time and restore power supply, it is necessary to install a fault current detection and indication device. The fault current measurement CT is a key component of the fault current detection device, and its measurement accuracy and reliability directly affect the accuracy and precision of fault judgment. Since the distribution overhead lines are generally 6-35kV high-voltage lines and do not have 220V / 380V mains electricity, the self-power supply problem of the fault current detection and indication device must be solved.

[0003] The current mainstream technology is to use 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, which is time-division multiplexed as 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 groups of coils wound on it, one group of coils is used for power supply, and the other group 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 above-mentioned problems, 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 will affect the accuracy of current measurement.

[0005] A method for designing a fault current measurement CT integrating energy collection and measurement, comprising the following steps:

[0006] 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;

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

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

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

[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 according to 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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 the output power and the core material and the 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 taking coil when the magnetic core is not saturated based on the working equivalent diagram:

[0016] E2=4.44fN2φ m

[0017] Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking coil;

[0018] According to the total 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 output power of the power taking coil after ignoring the hysteresis loss component of the magnetic core is determined;

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

[0020] Preferably, the method of determining the optimal structure size and preferred core material of the large CT according to the relationship between the output power of the large CT and the core material and the core structure size in combination with the power requirement 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 according to the saturation magnetic induction intensity and saturation current parameters;

[0022] Determine the expected cross-sectional coefficient for the material core according to the power requirement of the current measurement module circuit, and select the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the large CT output power and the core material and the core structure size;

[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 the operation of the large CT according to the optimal structural size, 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;

[0027] 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 line;

[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 according to 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 of each working module in the integrated structure according to power supply and measurement characteristics;

[0032] An analysis module is 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 according to the relationship between the output power of the large CT and the core material and the 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 according to the optimal structural dimensions, adjust the optimal structural dimensions according to the influence factor, and generate design parameters for CT design according to 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 groups 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 groups;

[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 of each working module 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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 comprises:

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

[0041] E2=4.44fN2φ m

[0042] Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φm It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking 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 according to the full current law equation and 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 determination submodule is used to determine the relevant variable parameters of the output power according to the output power representation, and determine the relationship between the output power magnetic core material and the magnetic core structure size according to the relevant 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 section coefficient for the material magnetic core according to the power requirement of the current measurement module circuit, and screen out the optimal magnetic core material according to the expected section coefficient and the effective section coefficient and the relationship between the large CT output power and the magnetic core material and the magnetic core structure size;

[0048] A sixth determination submodule is used to determine the core cross-section parameters of the optimal core material according to the rated current parameters and the overload current multiple and the target saturation current parameters of the optimal core material;

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

[0050] Preferably, the generating module comprises:

[0051] An eighth determination submodule is used to determine the magnetic induction intensity amplitude required for the operation of the large CT according to the optimal structural size, 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;

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

[0053] An adjustment submodule is used to confirm that there is an impact if the quotient value is greater than 1, and confirm that there is no impact if the quotient value is less than 1, and to adjust the optimal structural size in proportion to 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 according to the 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 partly become apparent from the description, or 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 collection and measurement provided by the present invention;

[0059] Figure 2 Another working flow chart of the method for designing a fault current measurement CT integrating energy acquisition and measurement provided by the present invention;

[0060] Figure 3 A schematic diagram of the structure of a fault current measurement CT design system with integrated energy collection and measurement provided by the present invention;

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

[0062] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0063] At present, grounding and short-circuit faults frequently occur in distribution lines, especially overhead lines, posing a safety threat to the safe and stable operation of the distribution network and the normal production and life of the people. In order to accurately identify the type and location of the fault so as to eliminate the fault in time and restore power supply, it is necessary to install a fault current detection and indication device. The fault current measurement CT is a key component of the fault current detection device, and its measurement accuracy and reliability directly affect the accuracy and precision of fault judgment. Since the distribution overhead lines are generally 6-35kV high-voltage lines and do not have 220V / 380V mains electricity, the self-power supply problem of the fault current detection and indication device must be solved.

[0064] The current mainstream technology is to use 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 volume of the power supply structure. In order to save cost and space, there is also a single CT, which is time-division multiplexed as the power supply CT and the measurement CT through the control circuit. This method has the problems of discontinuous power supply, affecting the power supply efficiency, discontinuous CT sampling, and easy leakage of fault current. There is also a single CT core with two groups of coils wound on it, one group of coils is used for power supply, and the other group 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. In order 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 extraction and measurement, such as Figure 1 As shown, the following steps are included:

[0066] Step S101, designing 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;

[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 according to the relationship between the output power of the large CT and the core material and the core structure size combined with the power requirement of the current measurement module circuit;

[0069] Step S104: Calculate the influence factor of the power-taking 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, a large CT is an open through-core structure, which is convenient for installation and disassembly. The installation and disassembly 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 not prone to saturation;

[0072] The working principle of the above technical solution is: design an integrated structure of a large CT and a small CT, determine the connection relationship of each working module in the integrated structure according to the power supply and measurement characteristics, the primary circuit of the large CT is connected to the power line under test, sense the current size of the measured line and transmit 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 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, and is used for power line fault analysis after being processed by the current measurement circuit module. The current power module circuit converts the large CT current into a stable voltage and power output to provide stable power for the current measurement circuit module. The role of the small CT is to isolate the current power module and the current measurement module to avoid direct interference between the two. The small CT is small in size and can be integrated inside the fault current measurement device.

[0073] The beneficial effects of the above technical solution are as follows: through the method of cascading a large CT and a small CT, the large CT is used as a power supply and current measurement device at the same time, and the small CT is used as a secondary current signal transmission and isolation device, so as to further reduce the large current signal to a small current signal, and isolate the power supply circuit and the current measurement circuit at the same time. Power supply and measurement share the same large CT, and power supply and current measurement can be performed at the same time, and power supply and current measurement do not interfere with each other, which can ensure the maximum utilization of CT power supply energy and the continuity and accuracy of current sampling, solving the problems of discontinuous power supply in traditional technology, affecting power supply efficiency, discontinuous CT sampling, easy leakage of fault current, and the simultaneous existence of power supply process affecting 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 of each working module in the integrated structure according to 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 according to 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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 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 the output power and the core material and the 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 taking coil when the magnetic core is not saturated based on the working equivalent diagram:

[0081] E2=4.44fN2φ m

[0082] Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking coil;

[0083] According to the total 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 output power of the power taking coil after ignoring the hysteresis loss component of the magnetic core is determined;

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

[0085] In this embodiment, according to the full current law equation, it can be known that:

[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 is represented by the amplitude of the magnetic field strength in the core of the power-taking coil, S is represented by the cross-sectional area of ​​the core of the power-taking coil, u is represented by the magnetic permeability of the core, l is represented by the magnetic path length of the core of the power-taking coil, N1 is represented by the number of turns of the primary side of the power-taking coil, which can be considered as 1 turn, I u It is expressed as the effective value of the magnetizing current of the power taking 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, I m I 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 which 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 magnetic core is not saturated. fe ;

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

[0093]

[0094] From the above formula, it can be seen that the output power of the power taking 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 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 according to 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, the method of determining the optimal structure size and preferred core material of the large CT according to the relationship between the output power of the large CT and the core material and the 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 according to the saturation magnetic induction intensity and saturation current parameters;

[0098] Determine the expected cross-sectional coefficient for the material core according to the power requirement of the current measurement module circuit, and select the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the large CT output power and the core material and the core structure size;

[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 core material according to the effective cross-sectional coefficient, the 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 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 core material based on the rated current parameters, the overload current multiple and the target saturation current parameters of the optimal core material, the power supply and measurement synchronization process can be achieved while ensuring that the core is not saturated, thereby improving the working stability and practicality.

[0102] In one embodiment, Figure 2 As shown, the influence factor of the power-taking performance on the current measurement is calculated according to the optimal structural dimensions, the optimal structural dimensions are adjusted according to the influence factor, and the design parameters are generated according to the adjusted structural dimensions and the preferred magnetic core material to perform CT design, including:

[0103] Step S201, determining the magnetic induction intensity amplitude required for the operation of the large CT according to the optimal structural size, 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, determining the maximum power consumption that can be provided by the power taking according to the maximum current of the power taking, and calculating the quotient of the maximum power consumption that can be provided by the power taking and the load power consumption of the measured line;

[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; 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 structural 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 power 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 steel 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 energy-taking circuit MPPT 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] The secondary current is

[0123]

[0124] It can be seen that the maximum current that can be extracted by the secondary energy extraction is 4.9674mA, and the power that can be provided is: 4.9674*2mW=9.9348mW, which is much larger than the power consumption of 0.434mW required by the load. The quotient of the two is greater than 1, which confirms that the excitation current required for energy extraction has little effect on the measurement. When the primary current continues to increase, and the power consumption required for energy extraction remains unchanged, that is, the required excitation current increases very little, so as the primary current increases, as long as the magnetic core is not saturated, the impact of energy extraction on the accuracy will become smaller and smaller, indicating that the impact of energy extraction on the 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, and can meet the requirements of power drawing and current measurement at the same time, and the power drawing does not affect the current measurement accuracy, further improving the 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 of each working module in the integrated structure according to 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 the output power and the core material and the core structure size;

[0129] The second determination module 303 is used to determine the optimal structure size and preferred core material of the large CT according to the relationship between the output power of the large CT and the core material and the 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-taking 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 groups 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 groups;

[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 of each working module 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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 comprises:

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

[0138] E2=4.44fN2φ m

[0139] Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking 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 according to the full current law equation and 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 determination submodule is used to determine the relevant variable parameters of the output power according to the output power representation, and determine the relationship between the output power magnetic core material and the magnetic core structure size according to the relevant 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 section coefficient for the material magnetic core according to the power requirement of the current measurement module circuit, and screen out the optimal magnetic core material according to the expected section coefficient and the effective section coefficient and the relationship between the large CT output power and the magnetic core material and the magnetic core structure size;

[0145] A sixth determination submodule is used to determine the core cross-section parameters of the optimal core material according to the rated current parameters and the overload current multiple and the target saturation current parameters of the optimal core material;

[0146] The seventh determination submodule is used to determine the optimal structural dimensions 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 used to determine the magnetic induction intensity amplitude required for the operation of the large CT according to the optimal structural size, 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 used to determine the maximum power consumption that can be provided by power taking according to the maximum current of energy taking, and calculate the quotient of the maximum power consumption that can be provided by power taking and the load power consumption of the measured line;

[0150] An adjustment submodule 3043 is used to confirm that there is an impact if the quotient is greater than 1, and confirm that there is no impact if the quotient is less than 1, and to adjust the optimal structural size in proportion to 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 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 merely refer to different application stages.

[0153] Other embodiments of the present disclosure will be readily apparent to those skilled in the art after considering the specification and practicing the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present disclosure are 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 may 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 of each working module in the integrated structure based on power supply and measurement characteristics; Modeling and analysis of large CTs were performed to determine the relationship between output power and core material and core structure size; According to the relationship between the output power of the large CT and the core material and the core structure size, combined with the power requirements of the current measurement module circuit, the optimal structure size and preferred core material of the large CT are determined; The influence factor of the power-taking performance on the current measurement is calculated according to the optimal structural dimensions, the optimal structural dimensions are adjusted according to the influence factors, and the design parameters are generated according to the adjusted structural dimensions and the preferred magnetic core material to design the CT.

2. The method for designing a fault current measurement CT integrating energy extraction 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 according to 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; 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 according to the functional characteristics and power supply and measurement characteristics; 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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.

3. The method for designing a fault current measurement CT integrating energy extraction and measurement according to claim 1 is characterized in that: The modeling and analysis of the large CT to determine the relationship between the output power and the core material and the 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 taking coil when the magnetic core is not saturated based on the working equivalent diagram: E2=4.44fN2φ m Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking coil; According to the total 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 output power of the power taking coil after ignoring the hysteresis loss component of the magnetic core is determined; The output power is expressed as related variable parameters of the output power, and the relationship between the output power magnetic core material and the magnetic core structure size is determined according to the related variable parameters.

4. The method for designing a fault current measurement CT integrating energy extraction 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 according to the relationship between the output power of the large CT and the core material and the 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 according to the saturation magnetic induction intensity; Determine the expected cross-sectional coefficient for the material core according to the power requirement of the current measurement module circuit, and select the optimal core material according to the expected cross-sectional coefficient and the effective cross-sectional coefficient as well as the relationship between the large CT output power and the core material and the core structure size; 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. The method for designing a fault current measurement CT integrating energy extraction and measurement according to claim 1 is characterized in that: 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 the operation of the large CT according to the optimal structural size, 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; 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 line; 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. The adjusted structural dimensions are obtained and design parameters are generated based on the structural dimensions and the preferred magnetic core material to perform CT design.

6. A fault current measurement CT design system integrating energy extraction 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 of each working module in the integrated structure according to power supply and measurement characteristics; An analysis module is 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 according to the relationship between the output power of the large CT and the core material and the core structure size combined with the power requirement of the current measurement module circuit; The generation module is used to calculate the influence factor of power-taking performance on current measurement according to the optimal structural dimensions, adjust the optimal structural dimensions according to the influence factor, and generate design parameters for CT design according to the adjusted structural dimensions and the preferred magnetic core material.

7. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 6 is characterized in that: The first determining module includes: Design submodules to determine the working module groups 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 groups; 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 of each working module in the integrated structure according to the functional characteristics and the power supply and measurement characteristics; 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 line under test 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 acquisition module circuit in sequence. The secondary circuit of the small CT is connected to the input end of the current measurement circuit module and is used for power line fault analysis after being processed by the current measurement circuit module. The current power acquisition 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.

8. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 6 is characterized in that: The analysis module comprises: The second determination submodule is used to construct a working model of the large CT, generate a working equivalent diagram of the large CT according to the working model, and determine the instantaneous output voltage of the secondary side of the power taking coil when the magnetic core is not saturated according to the working equivalent diagram: E2=4.44fN2φ m Where E2 represents the instantaneous output voltage of the secondary side of the power taking 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 taking coil, φ m It is expressed as the amplitude of the magnetic flux passing through the magnetic core of the power taking 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 according to the full current law equation and 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 determination submodule is used to determine the relevant variable parameters of the output power according to the output power representation, and determine the relationship between the output power magnetic core material and the magnetic core structure size according to the relevant variable parameters.

9. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 6, characterized in that: The second determining module includes: 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; A screening submodule is used to determine the expected section coefficient for the material magnetic core according to the power requirement of the current measurement module circuit, and screen out the optimal magnetic core material according to the expected section coefficient and the effective section coefficient and the relationship between the large CT output power and the magnetic core material and the magnetic core structure size; A sixth determination submodule is used to determine the core cross-section parameters of the optimal core material according to the rated current parameters and the overload current multiple and the target saturation current parameters of the optimal core material; The seventh determination submodule is used to determine the optimal structural dimensions of the large CT according to the core cross-sectional parameters.

10. The fault current measurement CT design system integrating energy acquisition and measurement according to claim 6, characterized in that: The generating module comprises: An eighth determination submodule is used to determine the magnetic induction intensity amplitude required for the operation of the large CT according to the optimal structural size, 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; A calculation submodule, used to determine the maximum power consumption that can be provided by power taking according to the maximum current of energy taking, and calculate the quotient of the maximum power consumption that can be provided by power taking and the load power consumption of the measured line; An adjustment submodule is used to confirm that there is an impact if the quotient is greater than 1, and confirm that there is no impact if the quotient is less than 1, and to adjust the optimal structural size in proportion to 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 according to the structural dimensions and the preferred magnetic core material for CT design.

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