Detection device and method for a current transformer

Abstract

This invention provides a detection device and method for a current transformer. The detection device includes a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module. Firstly, compared to existing direct detection schemes, it avoids the true capacitance value of the distributed capacitance being completely obscured by interference signals, thereby improving detection accuracy. Secondly, the excitation source module can output multiple excitation voltages, and the multi-channel amplification module has multiple amplification channels with different amplification factors. Under the control of the main control module, a corresponding excitation voltage can be selected as the target excitation voltage, and a suitable amplification channel from the multi-channel amplification module can be selected for amplification processing. This allows the main control module to accurately acquire the target amplified voltage, further improving detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of device testing technology, and specifically to a testing device and method for a current transformer. Background Technology

[0002] As the core device for current measurement in power systems, the current transformer's measurement accuracy and anti-interference capability directly affect the system's safe and stable operation. In existing technologies, whether it is a traditional electromagnetic current transformer or a new electronic current transformer, parasitic capacitance, i.e., the distributed capacitance between the primary and secondary windings, is inevitably formed due to the physical structure between the primary and secondary windings (such as the distance between windings, insulation material, shielding method, etc.).

[0003] Distributed capacitance can distort the measurement accuracy of current transformers. Current technologies typically detect distributed capacitance to correct the measurement results. Current detection methods for distributed capacitance usually involve direct testing. However, the capacitance value of distributed capacitance is extremely small, far lower than the parasitic capacitance and inductance of typical test leads, fixtures, and the test circuit itself. When using conventional capacitance bridges or LCR (inductance, capacitance, resistance) testers for direct testing, the stray capacitance of the test leads will be connected in parallel with the distributed capacitance being measured. Changes in wiring methods, personnel proximity, and grounding shielding methods can all introduce errors that are difficult to quantify, causing the true capacitance value of the distributed capacitance to be completely obscured by interference signals, making accurate detection results impossible. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a detection device and method for current transformers.

[0005] In a first aspect, in one embodiment, the present invention provides a detection device for a current transformer, the detection device for the current transformer including a main control module, an excitation source module, a current sampling module and a multi-channel amplification module; The output of the excitation source module is used to electrically connect to the primary winding of the current transformer under test, the input of the current sampling module is used to electrically connect to the secondary winding of the current transformer under test, and the output of the current sampling module is electrically connected to the input of the multi-channel amplification module. The main control module is electrically connected to the control terminal of the excitation source module, the control terminal of the multi-channel amplification module, and multiple output terminals of the multi-channel amplification module. It is used to control the excitation source module to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, control the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and determine the distributed capacitance between the primary winding and the secondary winding of the current transformer under test based on the target amplification voltage and the target excitation voltage output by the corresponding amplification channel in the multi-channel amplification module. The excitation source module is used to output multiple excitation voltages, and the target excitation voltage is one of the multiple excitation voltages; the current sampling module is used to detect the leakage current flowing out of the secondary winding of the current transformer under test and output the sampling voltage.

[0006] In one embodiment, the current sampling module includes a sampling resistor; The first end of the sampling resistor is electrically connected to the input of the multi-channel amplifier module and is used to electrically connect to the secondary winding of the current transformer under test. The second end of the sampling resistor is used for grounding.

[0007] In one embodiment, the multi-channel amplification module includes a first multi-channel analog switch and multiple amplification units; The input terminal of the first multi-channel analog switch is electrically connected to the output terminal of the current sampling module, the multiple output terminals of the first multi-channel analog switch are electrically connected to the input terminals of the corresponding amplification units, and the control terminal of the first multi-channel analog switch and the output terminal of each amplification unit are electrically connected to the main control module. The input terminal of the first multi-channel analog switch is electrically connected to the corresponding amplification unit through its corresponding output terminal, so as to serve as an amplification channel in the multi-channel amplification module.

[0008] In one embodiment, each amplification unit includes a first operational amplifier, a first input resistor, and a first feedback resistor; The first end of the first input resistor is electrically connected to the output end of the first multi-channel analog switch, the second end of the first input resistor is electrically connected to the non-inverting input end of the first operational amplifier, the inverting input end of the first operational amplifier is electrically connected to the first end of the first feedback resistor, and the output end of the first operational amplifier is electrically connected to the second end of the first feedback resistor and the main control module, respectively.

[0009] In one embodiment, each amplification unit further includes a second operational amplifier, a second input resistor, and a second feedback resistor; The first end of the second input resistor is electrically connected to the output end of the first operational amplifier and the second end of the first feedback resistor, respectively. The second end of the second input resistor is electrically connected to the non-inverting input end of the second operational amplifier. The inverting input end of the second operational amplifier is electrically connected to the first end of the second feedback resistor. The output end of the second operational amplifier is electrically connected to the second end of the second feedback resistor and the main control module, respectively. The output of the first operational amplifier is electrically connected to the main control module through the second operational amplifier.

[0010] In one embodiment, the detection device for the current transformer further includes a multi-channel transmission module; Each input terminal of the multi-channel transmission module is electrically connected to the corresponding output terminal of the multi-channel amplification module, and the output terminal of the multi-channel transmission module is electrically connected to the main control module. The main control module is used to control the corresponding transmission channel in the multi-channel transmission module to connect to the target amplified voltage and transmit it to the main control module.

[0011] In one embodiment, the multi-channel transmission module includes a second multi-channel analog switch; Each input terminal of the second multi-channel analog switch is electrically connected to the corresponding output terminal of the multi-channel amplification module, and the control terminal and output terminal of the second multi-channel analog switch are electrically connected to the main control module. The input terminal of the second multi-channel analog switch is electrically connected to its output terminal to serve as a transmission channel in the multi-channel transmission module.

[0012] Secondly, in one embodiment, the present invention provides a method for detecting a current transformer, which is applied to the current transformer detection device in any of the above embodiments; the current transformer detection method includes the following steps executed by the main control module: The excitation source module controls the output of the target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and controls the sampling voltage output by the current sampling module to be connected to the corresponding amplification channel in the multi-channel amplification module, so as to obtain the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module. Determine the distributed capacitance between the primary and secondary windings of the current transformer under test based on the target amplification voltage and the target excitation voltage. The current sampling module is used to detect the leakage current flowing out of the secondary winding of the current transformer under test and output a sampling voltage.

[0013] In one embodiment, controlling the sampling voltage output of the current sampling module connected to the corresponding amplification channel in the multi-channel amplification module to obtain the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module includes: One amplification channel in the multi-channel amplification module is designated as the undetermined amplification channel, and the sampling voltage is connected to the undetermined amplification channel to obtain the undetermined amplification voltage output by the undetermined amplification channel. If the voltage to be amplified exceeds the preset voltage range, then another amplification channel in the multi-channel amplification module will be designated as the new amplification channel to be amplified. The process continues until the obtained undetermined amplification voltage does not exceed the preset voltage range, at which point the final obtained undetermined amplification voltage is determined as the target amplification voltage.

[0014] In one embodiment, controlling the excitation source module to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, controlling the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and obtaining the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module includes: The excitation source module controls the output of a predetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test. One amplification channel in the multi-channel amplification module is determined as the predetermined amplification channel. The predetermined amplification channel is connected to the sampling voltage and the predetermined amplification voltage output by the predetermined amplification channel is obtained. If the undetermined amplification voltage exceeds the preset voltage range, the excitation source module is controlled to output another undetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and another amplification channel in the multi-channel amplification module is determined as the new undetermined amplification channel. Until the obtained undetermined amplification voltage does not exceed the preset voltage range, the final output undetermined excitation voltage is determined as the target excitation voltage, and the final obtained undetermined amplification voltage is determined as the target amplification voltage.

[0015] The aforementioned current transformer detection device and method are configured with a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module. First, under the control of the main control module, the excitation source module outputs a target excitation voltage relative to the secondary winding of the current transformer under test, causing leakage current to flow through the secondary winding of the current transformer under test due to the distributed capacitance between its primary and secondary windings. The current sampling module detects the leakage current flowing out of the current transformer under test and outputs a sampling voltage. The multi-channel amplification module amplifies the detected voltage and outputs a target amplified voltage, enabling the main control module to detect the leakage current according to the target voltage. The distributed capacitance of the current transformer under test is determined by using the excitation voltage and the target amplified voltage characterizing the leakage current. Compared with the direct detection scheme in the prior art, this method avoids the true capacitance value of the distributed capacitance being completely covered by interference signals, thereby improving the accuracy of the detection. In addition, the excitation source module can output multiple excitation voltages, and the multi-channel amplification module has multiple amplification channels with different amplification factors. Under the control of the main control module, the corresponding excitation voltage can be selected as the target excitation voltage, and a suitable amplification channel in the multi-channel amplification module can be selected to achieve amplification processing. This allows the main control module to accurately obtain the target amplified voltage, thereby further improving the accuracy of the detection. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the detection device of a current transformer in one embodiment of the present invention; Figure 2This is a schematic diagram of the specific structure of the current transformer under test in one embodiment of the present invention; Figure 3 This is a schematic diagram of a specific circuit in one embodiment of the present invention when a current sampling module is provided; Figure 4 This is a schematic diagram of a specific circuit corresponding to the provision of two current sampling modules in one embodiment of the present invention; Figure 5 This is a schematic diagram of the specific structure of a multi-channel amplification module in one embodiment of the present invention; Figure 6 This is a schematic diagram of a specific circuit in one embodiment of the present invention when the amplification unit is used for the same-name terminal of the secondary winding and adopts single-stage amplification. Figure 7 This is a schematic diagram of a specific circuit in one embodiment of the present invention, when the amplification unit is used for the same-name terminal of the secondary winding and adopts two-stage amplification. Figure 8 This is a schematic diagram of a specific circuit in one embodiment of the present invention, when the amplification unit targets the opposite-named terminals of the secondary winding and employs two-stage amplification. Figure 9 A schematic diagram of the structure of the current transformer detection device further including a multi-channel transmission module in one embodiment of the present invention; Figure 10 This is a schematic diagram of a specific circuit for the multi-channel transmission module corresponding to the same-name terminals of the secondary winding in one embodiment of the present invention; Figure 11 This is a schematic diagram of a specific circuit for the multi-channel transmission module corresponding to the opposite-named terminals of the secondary winding in one embodiment of the present invention; Figure 12 This is a flowchart illustrating a current transformer detection method in one embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified. In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to implement and use the invention. In the following description, details are set forth for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be implemented without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed herein.

[0020] Firstly, such as Figure 1 As shown, in one embodiment, the present invention provides a detection device for a current transformer, which includes a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module.

[0021] The output of the excitation source module is used to electrically connect to the primary winding of the current transformer under test, the input of the current sampling module is used to electrically connect to the secondary winding of the current transformer under test, and the output of the current sampling module is electrically connected to the input of the multi-channel amplification module.

[0022] The main control module is electrically connected to the control terminal of the excitation source module to output the excitation control signal C0_CTL to the excitation source module; the main control module is electrically connected to the control terminal of the multi-channel amplifier module to output the amplification channel control signal Cx_CTL to the multi-channel amplifier module; the main control module is electrically connected to multiple output terminals of the multi-channel amplifier module to receive the amplification voltage TEST_1 and amplification voltage TEST_2.

[0023] The main control module controls the excitation source module to output a target excitation voltage U0 relative to the secondary winding to the primary winding of the current transformer under test. This target excitation voltage U0 serves as the potential difference between the primary and secondary windings, causing leakage current I to flow through the secondary winding of the current transformer under test under the influence of the distributed capacitance C0 between its primary and secondary windings. k .

[0024] The target excitation voltage U0 includes a power frequency voltage or harmonic voltage with a specific voltage amplitude. When the target excitation voltage U0 is applied to the primary winding of the current transformer under test, a capacitive coupling current, i.e., leakage current I, will be generated through the distributed capacitance C0. k With the target excitation voltage U0 remaining constant, the larger the capacitance value of the distributed capacitance C0, the greater the resulting leakage current I. k The larger the capacitance, the less the current flows through the secondary winding; instead of following the normal electromagnetic induction path, it is directly coupled to the secondary winding and flows out through it. Specifically, the distributed capacitance C0 = I k / (2π×f×U0), where f is the frequency of the target excitation voltage U0. It can be seen that when the distributed capacitance C0 remains constant, the larger the frequency f of the target excitation voltage U0 and / or the larger the target excitation voltage U0, the greater the leakage current I. k The larger.

[0025] The excitation source module is used to output multiple excitation voltages, and the target excitation voltage is one of the multiple excitation voltages.

[0026] The current sampling module is used to detect the leakage current I flowing out of the secondary winding of the current transformer under test. k Perform detection and output sampling voltage U k .

[0027] Among them, the current sampling module can use various methods to realize the leakage current I. k The detection.

[0028] The main control module is also used to control the sampling voltage U output by the current sampling module connected to the corresponding amplification channel in the multi-channel amplification module. k So that the corresponding amplification channel in the multi-channel amplification module can respond to the sampling voltage U k The amplification process is performed and the target amplified voltage (Amplified voltage TEST_1 or Amplified voltage TEST_2) is output. Based on the target amplified voltage (Amplified voltage TEST_1 or Amplified voltage TEST_2) and the target excitation voltage U0 output by the corresponding amplification channel in the multi-channel amplification module, the distributed capacitance C0 between the primary winding and the secondary winding of the current transformer under test is determined.

[0029] In this multi-channel amplification module, different amplification channels correspond to different amplification factors. The main control module can select the appropriate amplification channel to sample the voltage U. k The sample size is amplified to meet the sampling range requirements of the main control module.

[0030] Specifically, with Figure 1 Taking the specific parameters shown as an example, the multi-channel amplification module includes two amplification channels. If the main control module selects the first amplification channel, the amplification voltage TEST_1 output by the first amplification channel is used as the target amplification voltage. Similarly, if the main control module selects the second amplification channel, the amplification voltage TEST_2 output by the second amplification channel is used as the target amplification voltage.

[0031] In addition, in other embodiments, the excitation source module can output excitation voltages with different voltage amplitudes and frequencies. In this case, the main control module can also select the excitation voltage with the corresponding voltage amplitude and frequency as the target excitation voltage to adjust the output target amplification voltage.

[0032] As a supplement, the main control module can be electrically connected to the excitation source module and the multi-channel amplifier module via RS485 to output corresponding control signals; the main control module can also be electrically connected to the multi-channel amplifier module via RS232 to access the target amplification voltage.

[0033] The current transformer detection device described above is configured with a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module. First, under the control of the main control module, the excitation source module outputs a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test. This causes leakage current to flow through the secondary winding of the current transformer under test due to the distributed capacitance between its primary and secondary windings. The current sampling module detects the leakage current flowing out of the current transformer under test and outputs a sampled voltage. The multi-channel amplification module amplifies the detected voltage and outputs a target amplified voltage, enabling the main control module to detect the leakage current according to the target voltage. The distributed capacitance of the current transformer under test is determined by the excitation voltage and the target amplified voltage characterizing the leakage current. Compared with the direct detection scheme in the prior art, this avoids the true capacitance value of the distributed capacitance being completely covered by interference signals, thereby improving the accuracy of the detection. In addition, the excitation source module can output multiple excitation voltages, and the multi-channel amplification module has multiple amplification channels with different amplification factors. Under the control of the main control module, the corresponding excitation voltage can be selected as the target excitation voltage, and a suitable amplification channel in the multi-channel amplification module can be selected to achieve amplification processing. This allows the main control module to accurately obtain the target amplified voltage, thereby further improving the accuracy of the detection.

[0034] like Figure 2As shown, in one embodiment, the primary winding L1 of the current transformer under test CT1 is electrically connected to the output terminal of the excitation source module to receive the target excitation voltage U0. Under the action of the distributed capacitance C0, a leakage current I flows out from the corresponding terminal of the secondary winding L2 of the current transformer under test CT1. k1 The leakage current I flows out of the opposite terminal of the secondary winding L2 of the current transformer CT1 under test. k2 Leakage current I k1 Much greater than the leakage current I k2 .

[0035] If a certain margin of error is permissible, the leakage current I can be directly calculated. k1 As leakage current I k In this case, only one current sampling module and one multi-channel amplification module need to be configured. The current sampling module is used to sample the leakage current I. k1 Perform detection and output the corresponding sampling voltage U k1 This multi-channel amplifier module is used to sample the voltage U. k1 Perform amplification processing and output the corresponding amplified voltages TEST_11, TEST_12...TEST_1n.

[0036] To minimize errors, the leakage current I can be reduced. k1 and leakage current I k2 The sum of these is used as the leakage current I. k In this case, two current sampling modules and two multi-channel amplification modules need to be configured, one of which is used to sample the leakage current I. k1 Perform detection and output the corresponding sampling voltage U k1 The multi-channel amplification module corresponding to this current sampling module is used to sample the voltage U. k1 The amplification process is performed and the corresponding amplified voltages TEST_11, TEST_12...TEST_1n are output; another current sampling module is used to sample the leakage current I. k2 Perform detection and output the corresponding sampling voltage U k2 The multi-channel amplification module corresponding to this current sampling module is used to sample the voltage U. k2 Perform amplification processing and output the corresponding amplified voltages TEST_21, TEST_22...TEST_2n.

[0037] In one embodiment, the current sampling module includes a sampling resistor; the first end of the sampling resistor is electrically connected to the input of the multi-channel amplification module and is used to electrically connect to the secondary winding of the current transformer under test, and the second end of the sampling resistor is used to ground.

[0038] If the current sampling module and the multi-channel amplification module are each provided, such as Figure 3As shown, the current sampling module includes a sampling resistor R1. The first end of the sampling resistor R1 is electrically connected to the input end of the corresponding multi-channel amplification module and is used to electrically connect to the same-named end of the secondary winding L2 of the current transformer CT1 under test, so as to input the leakage current I. k1 And output sampling voltage U k1 The second terminal of the sampling resistor R1 is used for grounding.

[0039] If the current sampling module and the multi-channel amplification module are each provided in two forms, such as... Figure 4 As shown, the two current sampling modules each include a sampling resistor R1 and a sampling resistor R2. The first terminal of the sampling resistor R1 is electrically connected to the input terminal of the corresponding multi-channel amplification module and is used to electrically connect to the same-name terminal of the secondary winding L2 of the current transformer CT1 under test, so as to input the leakage current I. k1 And output sampling voltage U k1 The first terminal of the sampling resistor R2 is electrically connected to the input terminal of the corresponding multi-channel amplifier module and is used to electrically connect to the opposite terminal of the secondary winding L2 of the current transformer CT1 under test, so as to input the leakage current I. k2 And output sampling voltage U k2 The second terminals of sampling resistor R1 and sampling resistor R2 are respectively used for grounding.

[0040] like Figure 5 As shown, in one embodiment, it is used for sampling voltage U k1 The multi-channel amplification module for amplification includes a first multi-channel analog switch U11 and multiple amplification units.

[0041] The input terminal X of the first multi-channel analog switch U11 is connected to the output sampling voltage U. k1 The output terminal of the current sampling module is electrically connected to receive the sampling voltage U. k1 The multiple output terminals of the first multi-channel analog switch U11 (including output terminals X0, X1, X2, X3, X4, X5, X6 and X7) are electrically connected to the input terminals of the corresponding amplification units, respectively. The control terminals of the first multi-channel analog switch U11 (including control terminals A, B and C) and the output terminals of each amplification unit are electrically connected to the main control module.

[0042] The input terminal X of the first multi-channel analog switch U11 is electrically connected to the corresponding amplification unit through its corresponding output terminal, so as to serve as an amplification channel in the multi-channel amplification module.

[0043] The main control module can output channel control signals Cx_CTL111, Cx_CTL112, and Cx_CTL113 to the first multi-channel analog switch U11. Each control signal includes two states: low level and high level, thereby enabling eight combinations. This allows the input terminal X of the first multi-channel analog switch U11 to be connected to any one of the output terminals, and finally, the amplified voltage is output through the corresponding amplification unit.

[0044] Specifically, when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X0, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_11 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X1, the sampled voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_12 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X2, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_13 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X3, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_14 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X4, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_15 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X5, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_16 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X6, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage TEST_17 is generated; when the input terminal X of the first multi-channel analog switch U11 is connected to the output terminal X7, the sampling voltage U k1 After passing through the corresponding amplification unit, the output amplified voltage is TEST_18.

[0045] like Figure 6 As shown, in one embodiment, the amplification unit for outputting the amplified voltage TEST_11 includes a first operational amplifier U2111, a first input resistor R311, and a first feedback resistor R411.

[0046] The first end of the first input resistor R311 is electrically connected to the output terminal X0 of the first multi-channel analog switch U11. The second end of the first input resistor R311 is electrically connected to the non-inverting input terminal of the first operational amplifier U211. The inverting input terminal of the first operational amplifier U211 is electrically connected to the first end of the first feedback resistor R411. The output terminal of the first operational amplifier U211 is electrically connected to the second end of the first feedback resistor R411 and the main control module, respectively, to output the amplified voltage TEST_11.

[0047] Among them, the first operational amplifier U211, the first input resistor R311 and the first feedback resistor R411 are used to achieve in-phase amplification, and the amplification factor is R411 / R311.

[0048] like Figure 7 As shown, in one embodiment, the amplification unit for outputting the amplified voltage TEST_11 further includes a second operational amplifier U311, a second input resistor R511, and a second feedback resistor R611.

[0049] The first end of the second input resistor R511 is electrically connected to the output end of the first operational amplifier U211 and the second end of the first feedback resistor R411, respectively. The second end of the second input resistor R511 is electrically connected to the non-inverting input end of the second operational amplifier U311. The inverting input end of the second operational amplifier U311 is electrically connected to the first end of the second feedback resistor R611. The output end of the second operational amplifier U311 is electrically connected to the second end of the second feedback resistor R611 and the main control module, respectively. The output end of the first operational amplifier U211 is electrically connected to the main control module through the second operational amplifier U311.

[0050] The second operational amplifier U3111, the second input resistor R511, and the second feedback resistor R611 are used to achieve in-phase amplification, with a gain of R611 / R511. This embodiment also configures the first operational amplifier U211 and the second operational amplifier U311, enabling a two-stage operational amplifier configuration, thus allowing for more flexible implementation of amplification factor differences with other amplification units.

[0051] like Figure 8 As shown, in one embodiment, it is used for sampling voltage U k2 The multi-channel amplification module for amplification includes a first multi-channel analog switch U12 and multiple amplification units. The amplification unit for outputting the amplified voltage TEST_21 includes a first operational amplifier U221, a first input resistor R321, a first feedback resistor R421, a second operational amplifier U321, a second input resistor R521, and a second feedback resistor R621.

[0052] The input terminal X of the first multi-channel analog switch U12 is connected to the output sampling voltage U. k2 The output terminal of the current sampling module is electrically connected to receive the sampling voltage U. k2The multiple control terminals (including control terminal A, control terminal B and control terminal C) of the first multi-channel analog switch U12 are electrically connected to the main control module to respectively access the channel control signal Cx_CTL121, channel control signal Cx_CTL122 and channel control signal Cx_CTL123.

[0053] The first terminal of the first input resistor R321 is electrically connected to the output terminal X0 of the first multi-channel analog switch U12. The second terminal of the first input resistor R321 is electrically connected to the non-inverting input terminal of the first operational amplifier U221. The inverting input terminal of the first operational amplifier U221 is electrically connected to the first terminal of the first feedback resistor R421. The first terminal of the second input resistor R521 is electrically connected to the output terminal of the first operational amplifier U221 and the second terminal of the first feedback resistor R421. The second terminal of the second input resistor R521 is electrically connected to the non-inverting input terminal of the second operational amplifier U321. The inverting input terminal of the second operational amplifier U321 is electrically connected to the first terminal of the second feedback resistor R621. The output terminal of the second operational amplifier U321 is electrically connected to the second terminal of the second feedback resistor R621 and the main control module to output the amplified voltage TEST_21.

[0054] like Figure 9 As shown, in one embodiment, the detection device for the current transformer further includes a multi-channel transmission module.

[0055] Each input terminal of the multi-channel transmission module is electrically connected to the corresponding output terminal of the multi-channel amplification module to receive amplified voltages TEST_1 and TEST_2. The output terminal of the multi-channel transmission module is electrically connected to the main control module to output amplified voltage TEST_1 or amplified voltage TEST_2.

[0056] The main control module is used to control the corresponding transmission channel in the multi-channel transmission module to connect to the target amplified voltage and transmit it to the main control module.

[0057] Specifically, if the main control module selects amplified voltage TEST_1 as the target amplified voltage, it controls the multi-channel transmission module to connect to amplified voltage TEST_1 and output amplified voltage TEST_1; if the main control module selects amplified voltage TEST_2 as the target amplified voltage, it controls the multi-channel transmission module to connect to amplified voltage TEST_2 and output amplified voltage TEST_2.

[0058] This embodiment uses a multi-channel transmission module to achieve electrical connection between the multi-channel amplification module and the main control module, eliminating the need for the multiple output terminals of the multi-channel amplification module to be directly connected to the main control module, thereby reducing the interface occupation of the main control module.

[0059] like Figure 10As shown, in one embodiment, the multi-channel transmission module for respectively connecting amplified voltages TEST_11, TEST_12, TEST_13, TEST_14, TEST_15, TEST_16, TEST_17 and TEST_18 includes a second multi-channel analog switch U41.

[0060] Each input terminal of the second multi-channel analog switch U41 (including input terminal X0, input terminal X1, input terminal X2, input terminal X3, input terminal X4, input terminal X5, input terminal X6 and input terminal X7) is electrically connected to the corresponding output terminal of the multi-channel amplification module. The control terminal (including control terminal A, control terminal B and control terminal C) and output terminal X of the second multi-channel analog switch U41 are electrically connected to the main control module.

[0061] The input terminal of the second multi-channel analog switch U41 is electrically connected to its output terminal X to serve as a transmission channel in the multi-channel transmission module.

[0062] like Figure 11 As shown, in one embodiment, the multi-channel transmission module for respectively connecting amplified voltages TEST_21, TEST_22, TEST_23, TEST_24, TEST_25, TEST_26, TEST_27 and TEST_28 includes a second multi-channel analog switch U42.

[0063] Each input terminal of the second multi-channel analog switch U42 (including input terminal X0, input terminal X1, input terminal X2, input terminal X3, input terminal X4, input terminal X5, input terminal X6 and input terminal X7) is electrically connected to the corresponding output terminal of the multi-channel amplification module. The control terminal (including control terminal A, control terminal B and control terminal C) and output terminal X of the second multi-channel analog switch U42 are electrically connected to the main control module.

[0064] The input terminal of the second multi-channel analog switch U42 is electrically connected to its output terminal X to serve as a transmission channel in the multi-channel transmission module.

[0065] Secondly, in one embodiment, the present invention provides a method for detecting a current transformer, which is applied to the current transformer detection device in any of the above embodiments; the current transformer detection method includes the following steps executed by the main control module: The excitation source module controls the output of the target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and controls the sampling voltage output by the current sampling module to be connected to the corresponding amplification channel in the multi-channel amplification module, so as to obtain the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module. Determine the distributed capacitance between the primary and secondary windings of the current transformer under test based on the target amplification voltage and the target excitation voltage. The current sampling module is used to detect the leakage current flowing out of the secondary winding of the current transformer under test and output a sampling voltage.

[0066] The current transformer detection device used in the above-described current transformer detection method is configured with a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module. First, under the control of the main control module, the excitation source module outputs a target excitation voltage relative to the secondary winding of the current transformer under test, causing leakage current to flow through the secondary winding of the current transformer under test due to the distributed capacitance between its primary and secondary windings. The current sampling module detects the leakage current flowing out of the current transformer under test and outputs a sampled voltage. The multi-channel amplification module amplifies the detected voltage and outputs a target amplified voltage, enabling the main control module to... The module can determine the distributed capacitance of the current transformer under test based on the target excitation voltage and the target amplified voltage characterizing the leakage current. Compared with the direct detection scheme in the prior art, it can avoid the true capacitance value of the distributed capacitance being completely covered by the interference signal, thereby improving the accuracy of detection. In addition, the excitation source module can output multiple excitation voltages, and the multi-channel amplification module has multiple amplification channels with different amplification factors. Under the control of the main control module, the corresponding excitation voltage can be selected as the target excitation voltage, and the appropriate amplification channel in the multi-channel amplification module can be selected to achieve amplification processing, so that the main control module can accurately obtain the target amplified voltage, thereby further improving the accuracy of detection.

[0067] In one embodiment, controlling the sampling voltage output of the current sampling module connected to the corresponding amplification channel in the multi-channel amplification module to obtain the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module includes: One amplification channel in the multi-channel amplification module is designated as the undetermined amplification channel, and the sampling voltage is connected to the undetermined amplification channel to obtain the undetermined amplification voltage output by the undetermined amplification channel. If the voltage to be amplified exceeds the preset voltage range, then another amplification channel in the multi-channel amplification module will be designated as the new amplification channel to be amplified. The process continues until the obtained undetermined amplification voltage does not exceed the preset voltage range, at which point the final obtained undetermined amplification voltage is determined as the target amplification voltage.

[0068] Since the capacitance value of the distributed capacitance is completely unknown before detection, it is difficult to directly determine a suitable amplification channel. Therefore, in this embodiment, one amplification channel is first determined as the undetermined amplification channel, and amplification processing is performed based on this undetermined amplification channel. If the undetermined amplification voltage output by the undetermined amplification channel exceeds the preset voltage range, for example, if the sampling range of the main control module is 1V, the preset voltage range can be set to about 0.5V to ensure sampling accuracy. If the undetermined amplification voltage is only 10μV, it obviously exceeds the preset voltage range, and it can be determined that the undetermined amplification voltage is too small. Therefore, an amplification channel with a larger amplification factor can be determined as the new undetermined amplification channel.

[0069] In one embodiment, controlling the excitation source module to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, controlling the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and obtaining the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module includes: The excitation source module controls the output of a predetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test. One amplification channel in the multi-channel amplification module is determined as the predetermined amplification channel. The predetermined amplification channel is connected to the sampling voltage and the predetermined amplification voltage output by the predetermined amplification channel is obtained. If the undetermined amplification voltage exceeds the preset voltage range, the excitation source module is controlled to output another undetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and another amplification channel in the multi-channel amplification module is determined as the new undetermined amplification channel. Until the obtained undetermined amplification voltage does not exceed the preset voltage range, the final output undetermined excitation voltage is determined as the target excitation voltage, and the final obtained undetermined amplification voltage is determined as the target amplification voltage.

[0070] The difference between this embodiment and the above embodiments lies in the further control of the excitation source module. As mentioned in the above embodiments of the current transformer detection device, the larger the amplitude of the target excitation voltage and / or the higher the frequency of the target excitation voltage, the larger the leakage current. Therefore, in this embodiment, the amplitude and / or frequency of the excitation voltage can be further adjusted.

[0071] Specifically, in this embodiment, the excitation source module is first controlled to output a predetermined excitation voltage relative to the secondary winding, and one of the amplification channels is determined as the predetermined amplification channel and amplification processing is performed based on the predetermined amplification channel. If the predetermined amplification voltage output by the predetermined amplification channel exceeds the preset voltage range, for example, if the sampling range of the main control module is 1V and the preset voltage range can be set to about 0.5V to ensure sampling accuracy, and the predetermined amplification voltage is only 10μV, the predetermined amplification voltage obviously exceeds the preset voltage range, and it can be determined that the predetermined amplification voltage is too small. Therefore, the excitation source module can be controlled to output a predetermined excitation voltage with a larger voltage amplitude and the amplification channel with a larger amplification factor can be determined as the new predetermined amplification channel.

[0072] To make the embodiments of the above-described current transformer detection method clearer, the embodiments will now be described in combination, as follows: Figure 12 As shown, in one embodiment, the detection method for a current transformer includes: S1. The main control module sets the relevant parameters of the current transformer; S2. The main control module sends a distributed capacitance test command frame; S3. The main control module sends a command frame for outputting a pending excitation voltage (e.g., 50V) to the excitation source module. S4. After receiving the pending excitation voltage (e.g., 50V) output frame from the main control module, the excitation source module outputs the pending excitation voltage and sends a response frame to the main control module. S5. The main control module sends a command frame to the multi-channel amplification module to switch amplification channel 1. S6. The multi-channel amplification module receives the command frame for switching amplification channel 1 from the main control module, switches the amplification channel to amplification channel 1, and sends a response frame to the main control module. S7. Obtain the undetermined amplification voltage and feed it back to the main control module; S8. The main control module calculates the appropriate amplification channel and excitation voltage for the multi-channel amplification module based on the sampling range voltage (for example, when the sampling range is 1V and the excitation voltage is 50V, the returned amplification voltage is 10uV; at this time, the main control module can select an excitation voltage of 200V and select amplification channel 3, which has an amplification factor of 10000 times, so that the returned amplification voltage is about 0.4V). S9. Based on the calculation results of S8, the main control module sends a target excitation voltage output command frame (e.g., 200V) to the excitation source module. S10. After receiving the voltage (e.g., 200V) output frame from the main control module, the excitation source module outputs the corresponding target excitation voltage and sends a response frame to the main control module. S11. The main control module sends a command frame to the multi-channel amplification module to switch amplification channel x (e.g., amplification channel 3); S12. The multi-channel amplification module receives the command frame from the main control module to switch amplification channel x (e.g., amplification channel 3), switches the amplification channel to amplification channel x, and sends a response frame to the main control module. S13. Obtain the target amplified voltage and feed it back to the main control module; S14. The main control module calculates the size of the distributed capacitance based on the target amplification voltage and the target excitation voltage.

[0073] S15. The main control module calculates the error change of the leakage current within the operating range of the current transformer by measuring the size of the distributed capacitance, and determines whether it is applicable to the corresponding product.

[0074] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the detailed descriptions of other embodiments above, which will not be repeated here.

[0075] The detection device and method for a current transformer provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0076] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A detection device for a current transformer, characterized in that, The detection device of the current transformer includes a main control module, an excitation source module, a current sampling module, and a multi-channel amplification module; The output terminal of the excitation source module is used to be electrically connected to the primary winding of the current transformer under test, the input terminal of the current sampling module is used to be electrically connected to the secondary winding of the current transformer under test, and the output terminal of the current sampling module is electrically connected to the input terminal of the multi-channel amplification module. The main control module is electrically connected to the control terminal of the excitation source module, the control terminal of the multi-channel amplification module, and multiple output terminals of the multi-channel amplification module. It is used to control the excitation source module to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, control the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and determine the distributed capacitance between the primary winding and the secondary winding of the current transformer under test based on the target amplification voltage output by the corresponding amplification channel in the multi-channel amplification module and the target excitation voltage. The excitation source module is used to output multiple excitation voltages, and the target excitation voltage is one of the multiple excitation voltages; the current sampling module is used to detect the leakage current flowing out of the secondary winding of the current transformer under test and output the sampling voltage.

2. The detection device for a current transformer according to claim 1, characterized in that, The current sampling module includes a sampling resistor; The first end of the sampling resistor is electrically connected to the input end of the multi-channel amplification module and is used to electrically connect to the secondary winding of the current transformer under test. The second end of the sampling resistor is used for grounding.

3. The detection device for a current transformer according to claim 1, characterized in that, The multi-channel amplification module includes a first multi-channel analog switch and multiple amplification units; The input terminal of the first multi-channel analog switch is electrically connected to the output terminal of the current sampling module, the multiple output terminals of the first multi-channel analog switch are respectively electrically connected to the input terminals of the corresponding amplification units, and the control terminal of the first multi-channel analog switch and the output terminal of each amplification unit are respectively electrically connected to the main control module. The input terminal of the first multi-channel analog switch is electrically connected to the corresponding amplification unit through its corresponding output terminal, so as to serve as an amplification channel in the multi-channel amplification module.

4. The detection device for a current transformer according to claim 3, characterized in that, Each of the amplification units includes a first operational amplifier, a first input resistor, and a first feedback resistor; The first end of the first input resistor is electrically connected to the output end of the first multi-channel analog switch, the second end of the first input resistor is electrically connected to the non-inverting input end of the first operational amplifier, the inverting input end of the first operational amplifier is electrically connected to the first end of the first feedback resistor, and the output end of the first operational amplifier is electrically connected to the second end of the first feedback resistor and the main control module, respectively.

5. The detection device for a current transformer according to claim 4, characterized in that, Each of the amplification units further includes a second operational amplifier, a second input resistor, and a second feedback resistor; The first end of the second input resistor is electrically connected to the output end of the first operational amplifier and the second end of the first feedback resistor, respectively. The second end of the second input resistor is electrically connected to the non-inverting input end of the second operational amplifier. The inverting input end of the second operational amplifier is electrically connected to the first end of the second feedback resistor. The output end of the second operational amplifier is electrically connected to the second end of the second feedback resistor and the main control module, respectively. The output of the first operational amplifier is electrically connected to the main control module through the second operational amplifier.

6. The detection device for a current transformer according to claim 1, characterized in that, The detection device for the current transformer also includes a multi-channel transmission module; Each input terminal of the multi-channel transmission module is electrically connected to the corresponding output terminal of the multi-channel amplification module, and the output terminal of the multi-channel transmission module is electrically connected to the main control module. The main control module is used to control the corresponding transmission channel in the multi-channel transmission module to connect to the target amplified voltage and transmit it to the main control module.

7. The detection device for a current transformer according to claim 6, characterized in that, The multi-channel transmission module includes a second multi-channel analog switch; Each input terminal of the second multi-channel analog switch is electrically connected to the corresponding output terminal of the multi-channel amplification module, and the control terminal and output terminal of the second multi-channel analog switch are electrically connected to the main control module. The input terminal of the second multi-channel analog switch is electrically connected to its output terminal to serve as a transmission channel in the multi-channel transmission module.

8. A method for detecting a current transformer, characterized in that, The current transformer detection method is applied to the current transformer detection device according to any one of claims 1 to 7; the current transformer detection method includes the following steps executed by the main control module: The excitation source module is controlled to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and the corresponding amplification channel in the multi-channel amplification module is controlled to connect to the sampling voltage output by the current sampling module to obtain the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module. The distributed capacitance between the primary and secondary windings of the current transformer under test is determined based on the target amplification voltage and the target excitation voltage. The current sampling module is used to detect the leakage current flowing out of the secondary winding of the current transformer under test and output the sampling voltage.

9. The detection method for a current transformer according to claim 8, characterized in that, The step of controlling the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and obtaining the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module, includes: One of the amplification channels in the multi-channel amplification module is designated as the undetermined amplification channel, and the undetermined amplification channel is controlled to be connected to the sampling voltage and the undetermined amplification voltage output by the undetermined amplification channel is obtained. If the voltage to be amplified exceeds the preset voltage range, then another amplification channel in the multi-channel amplification module will be designated as the new amplification channel to be amplified. The process continues until the obtained undetermined amplification voltage does not exceed the preset voltage range, at which point the final obtained undetermined amplification voltage is determined as the target amplification voltage.

10. The detection method for a current transformer according to claim 8, characterized in that, The process of controlling the excitation source module to output a target excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, controlling the corresponding amplification channel in the multi-channel amplification module to connect to the sampling voltage output by the current sampling module, and obtaining the target amplified voltage output by the corresponding amplification channel in the multi-channel amplification module includes: The excitation source module is controlled to output a predetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test. One amplification channel of the multi-channel amplification module is determined as the predetermined amplification channel. The predetermined amplification channel is controlled to be connected to the sampling voltage and the predetermined amplification voltage output by the predetermined amplification channel is obtained. If the undetermined amplification voltage exceeds the preset voltage range, the excitation source module is controlled to output another undetermined excitation voltage relative to the secondary winding to the primary winding of the current transformer under test, and another amplification channel in the multi-channel amplification module is determined as a new undetermined amplification channel. Until the obtained undetermined amplification voltage does not exceed the preset voltage range, the final output undetermined excitation voltage is determined as the target excitation voltage, and the final obtained undetermined amplification voltage is determined as the target amplification voltage.

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