Field testing device and method for distribution network instrument transformers

Abstract

This application discloses a field testing device and method for distribution network transformers. The method employs a digital comparison approach, eliminating the need for a three-phase standard current transformer to match the transformer under test's ratio. It only requires the transformer under test to have a calibration point within the effective traceability range of the three-phase standard current transformer. Selecting a three-phase standard current transformer with a larger ratio can cover various transformer ratios under test in the field, effectively reducing the size and weight of the testing device and improving its convenience. This allows for on-site testing of the transformer under test. Furthermore, the device requires only a few wiring operations to accommodate transformers with various ratios, significantly reducing the number of wiring operations and time required, thus improving testing efficiency and safety. The method is simple, economical, scientific, practical, highly operable, and low-cost.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a field testing device and method for distribution network instrument transformers. Background Technology

[0002] Instrument transformers in distribution networks are key equipment between the primary and secondary windings of a distribution network system. They are subject to mandatory national verification and are mostly installed in power plants, substations, and dedicated / public transformer users for electricity metering and relay protection.

[0003] In most related technologies, the distribution network transformers used are disassembled and tested in the laboratory. With the advancement of ultra-high voltage transmission projects nationwide, the number of distribution network transformers requiring on-site testing is increasing daily, while on-site testing equipment is in short supply. Laboratory testing equipment is numerous, heavy, bulky, and inconvenient, making it difficult to test distribution network transformers at their application sites. Furthermore, laboratory testing equipment involves complex wiring, requiring multiple wiring operations for a single test, resulting in low efficiency and significant safety hazards, thus failing to meet the growing demand for on-site testing of distribution network transformers. Summary of the Invention

[0004] In view of this, this application provides a field testing device and method for distribution network transformers, which significantly reduces the size and weight of the testing device, can be directly applied to the field of distribution network transformers, improves the convenience of testing, reduces the number of wiring connections, and improves the efficiency and safety of testing.

[0005] According to one aspect of this application, a field testing device for distribution network transformers is provided. The device is connected to the distribution network transformer under test. The device includes: a three-phase standard voltage transformer, a three-phase standard current transformer, a voltage verification module, and a current verification module. The primary current circuit of the three-phase standard current transformer is connected in series with the primary current circuit of the distribution network transformer under test. The primary voltage circuit of the three-phase standard voltage transformer is connected in parallel with the primary voltage circuit of the distribution network transformer under test. The secondary current circuit of the three-phase standard current transformer is connected in parallel with the secondary current circuit of the distribution network transformer under test. The secondary current loops are respectively connected to the current verification module. The current verification module is used to receive the secondary current output by the three-phase standard current transformer and the transformer under test in the distribution network, and to determine the current detection result of the transformer under test in the distribution network. The secondary voltage loops in the three-phase standard voltage transformer and the transformer under test in the distribution network are respectively connected to the voltage verification module. The voltage verification module is used to receive the secondary voltage output by the three-phase standard voltage transformer and the transformer under test in the distribution network, and to determine the voltage detection result of the transformer under test in the distribution network.

[0006] According to another aspect of this application, a field testing method for distribution network transformers is provided, applied to the aforementioned field testing device for distribution network transformers. The method includes: a current verification module responding to a current detection command, determining the current detection result of the distribution network transformer under test based on the secondary currents output by a three-phase standard current transformer and the distribution network transformer under test; and a voltage verification module responding to a voltage detection command, determining the voltage detection result of the distribution network transformer under test based on the secondary voltages output by a three-phase standard voltage transformer and the distribution network transformer under test.

[0007] By utilizing the above technical solution, this application provides a field testing device and method for distribution network transformers. Employing a digital comparison-based testing method, it eliminates the need for the three-phase standard current transformer and the tested distribution network transformer to have identical transformation ratios. Only the calibration point of the tested distribution network transformer needs to be within the effective traceability range of the three-phase standard current transformer. Selecting a three-phase standard current transformer with a larger transformation ratio can cover various transformation ratios of the tested distribution network transformers in the field, effectively reducing the size and weight of the testing device and improving its convenience. This allows for on-site testing of the tested distribution network transformers. Furthermore, each component in the testing device requires only a few wiring operations to accommodate various transformation ratios of the tested distribution network transformers, significantly reducing the number of wiring operations and time required in the field, improving testing efficiency and safety. It boasts advantages such as simplicity, economy, scientific rigor, practicality, strong operability, and low cost.

[0008] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0009] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0010] Figure 1 This paper shows a structural block diagram of a field testing device for a power distribution network transformer provided in an embodiment of this application;

[0011] Figure 2 This paper shows a structural block diagram of another field testing device for distribution network transformers provided in an embodiment of this application;

[0012] Figure 3 This paper shows a structural block diagram of another field testing device for distribution network transformers provided in an embodiment of this application;

[0013] Figure 4A schematic diagram of the current verification module provided in an embodiment of this application is shown;

[0014] Figure 5 A schematic diagram of the voltage verification module provided in an embodiment of this application is shown;

[0015] Figure 6 This paper shows a structural block diagram of another field testing device for distribution network transformers provided in an embodiment of this application;

[0016] Figure 7 A flowchart illustrating the field testing method for distribution network instrument transformers provided in an embodiment of this application is shown.

[0017] Figure 8 A schematic diagram of the structure of the simulation comparison method detection device provided in the embodiment of this application is shown. Detailed Implementation

[0018] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this application means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “attached” to another element, it can be directly connected or attached to the other element, or there may be intermediate elements. Furthermore, “connected” or “attached” as used herein can include wireless connections or wireless interconnections. The term “and / or” as used herein includes all or any unit and all combinations of one or more associated listed items.

[0021] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art.

[0022] Distribution network instrument transformers are key equipment between the primary and secondary circuits of a distribution network system. They are subject to mandatory verification by the state and are mostly installed in power plants, substations, and dedicated / public transformer users for power metering and relay protection. With the release and implementation of the national verification standard JJG1165-2019 "Three-phase combined instrument transformers", distribution network instrument transformers need to undergo laboratory and field verification under rated operating voltage.

[0023] Currently, most testing of distribution network transformers is conducted in laboratories, leading to the following challenges in on-site testing: First, calibrating current boosters and standard current transformers under high voltage requires special shielding and insulation treatment, nearly doubling the size and weight of existing equipment, making it inconvenient to carry for on-site testing. Second, distribution network transformers operate in various environments, including pole-mounted, transformer-mounted, and metering cabinet locations, and existing testing equipment struggles to adapt to these complex environments and portability requirements. Third, the traditional laboratory calibration of current transformers uses a simulation comparison method (traditional differential measurement method), such as... Figure 8 As shown, the standard current transformer is required to have the same transformation ratio as the current transformer under test. In order to cover the transformation ratios of various types of current transformers under test, the standard current transformer has more than twenty current ratios, which is more than twice the size and weight of a single-ratio standard current transformer. It requires wiring more than ten times to complete one test. If the transformation ratio of the current transformer under test changes, it is necessary to rewire, resulting in low verification efficiency and significant safety hazards, with a low safety factor.

[0024] in, Figure 8 In the diagram, CT0 is the standard current transformer, CTx is the current transformer under test, L1, L2, P1, and P2 are the primary terminals of the current transformer, K1, K2, S1, and S2 are the secondary terminals of the current transformer, T0 is the secondary current input terminal of the standard current transformer in the analog comparison transformer calibrator, TX is the secondary current input terminal of the current transformer under test in the analog comparison transformer calibrator, and K is the differential current signal input terminal of the analog comparison transformer calibrator.

[0025] In view of this, this embodiment provides a field testing device for distribution network instrument transformers, such as... Figure 1 As shown, the device is connected to the transformer in the distribution network under test. The device includes: a three-phase standard voltage transformer, a three-phase standard current transformer, a voltage verification module, and a current verification module.

[0026] In this embodiment, a digital comparison method is used to calculate the measurement error of the current (voltage) of the transformer under test based on the secondary current (voltage) of the transformer under test and the standard transformer. It is not necessary for the three-phase standard current transformer and the transformer under test to have the same transformation ratio. It is only required that the calibration point of the transformer under test (i.e., the specific current value point for testing) is within the effective traceability range of the three-phase standard current transformer. Therefore, a three-phase standard current transformer with a larger transformation ratio can be selected to cover various transformation ratio transformers under test in the field. This can significantly reduce the size and weight of the three-phase standard current transformer, thereby improving the convenience of the overall testing device.

[0027] Specifically, such as Figure 1 As shown, on the one hand, the primary current loop in the three-phase standard current transformer 102 is connected in series with the primary current loop in the distribution network transformer 101 under test, so that when a large three-phase current is simultaneously input to the three-phase standard current transformer 102 and the distribution network transformer 101 under test, the primary current flowing through the three-phase standard current transformer 102 and the distribution network transformer 101 under test is the same, avoiding error calculation deviation caused by different primary currents and ensuring the accuracy of current detection.

[0028] Furthermore, the secondary current loops in the three-phase standard current transformer 102 and the distribution network transformer under test 101 are respectively connected to the current verification module 105. The low current portion, i.e., the secondary current, output after conversion by the three-phase standard current transformer 102 and the distribution network transformer under test 101 is input into the current verification module 105. This allows the current verification module 105 to calculate the error of the measured current of the distribution network transformer under test 101 based on the secondary currents output by the three-phase standard current transformer 102 and the distribution network transformer under test 101, and thus determine the current detection result of the distribution network transformer under test 101.

[0029] On the other hand, the primary voltage circuit in the three-phase standard voltage transformer 103 and the primary voltage circuit in the transformer under test 101 are connected in parallel so that when three-phase high voltage is input to both the three-phase standard voltage transformer 103 and the transformer under test 101 at the same time, the primary voltage of the three-phase standard voltage transformer 103 and the transformer under test 101 is the same, avoiding error calculation deviation caused by different primary voltages and ensuring the reliability of voltage detection.

[0030] Furthermore, the secondary voltage circuits in the three-phase standard voltage transformer 103 and the distribution network transformer under test 101 are respectively connected to the voltage verification module 104. The low voltage portion, i.e., the secondary voltage, output after conversion between the three-phase standard voltage transformer 103 and the distribution network transformer under test 101 is input to the voltage verification module 104. This allows the voltage verification module 104 to calculate the error of the voltage measured by the distribution network transformer under test 101 based on the secondary voltages output by the three-phase standard voltage transformer 103 and the distribution network transformer under test 101, thereby obtaining the voltage detection result of the distribution network transformer under test 101.

[0031] It should be noted that, as Figure 2 As shown, the three-phase high-voltage power source 206 can be used to provide three-phase high voltage and high current to the three-phase standard voltage transformer 103, the three-phase standard current transformer 102 and the transformer of the distribution network under test 101. According to relevant regulations and actual testing requirements, the corresponding three-phase high voltage and high current can be applied to simulate different operating conditions and improve testing efficiency and reliability.

[0032] It is worth mentioning that the corresponding part of the detection device can be selected to detect the transformer 101 under test according to the specific measurement type of the transformer 101. For example, if the transformer 101 under test is a current transformer, it can be connected to a three-phase standard current transformer 102 and a current verification module 105 to detect the error in the measured current of the transformer 101 and obtain the current detection result of the transformer 101. Similarly, if the transformer 101 under test is a voltage transformer, it can be connected to a three-phase standard voltage transformer 103 and a voltage verification module 104 to detect the error in the measured voltage of the transformer 101 and obtain the voltage detection result of the transformer 101. Furthermore, if the transformer under test 101 is a combined transformer consisting of a voltage transformer and a current transformer, then the transformer under test 101 is connected to the three-phase standard voltage transformer 103, the three-phase standard current transformer 102, the voltage verification module 104, and the current verification module 105, respectively, to detect the error of the measured voltage and measured current of the transformer under test 101, thereby obtaining the current detection result and voltage detection result of the transformer under test 101.

[0033] In practical applications, three-phase standard current transformers require special shielding and insulation treatment, and the error variation caused by leakage current must not exceed one-tenth of the error limit.

[0034] In one embodiment, such as Figure 3As shown, the field testing device for power distribution network transformers also includes: a current verification module comprising a first switching circuit, a single-phase digital current calibrator, and a first host computer. The single-phase digital current calibrator and the first host computer are respectively connected to the first switching circuit.

[0035] In this embodiment, the first switching circuit in the current verification module enables switching between different phases of the three-phase standard current transformer and the transformer under test in the distribution network. This allows the secondary currents of the same phase output from both the three-phase standard current transformer and the transformer under test to be simultaneously input to the single-phase digital current calibrator. The single-phase digital current calibrator then uses a time-division multiplexing method to detect the current errors of different phases of the transformer under test, thereby reducing the size and weight of the current transformer calibrator, further improving the convenience of the overall testing device, and enhancing the flexibility and specificity of current detection.

[0036] Among them, such as Figure 4 As shown, based on the rule that the secondary current loop of the current transformer cannot be in an open state, the three-phase output terminal and three-phase input terminal of the secondary current loop of the three-phase standard current transformer 102 and the transformer 101 of the distribution network under test are respectively connected to the terminals in the first switching circuit 304. In this way, the secondary current loop of the non-detection phase is short-circuited through the first switching circuit 304 to prevent the open circuit of the secondary current loop from causing serious harm to equipment and personnel, and to ensure the safety of the test.

[0037] Specifically, the A-phase, B-phase, and C-phase output terminals of the secondary current circuit in the three-phase standard current transformer 102 are respectively connected to the first terminal I in the first switching circuit 304. a0 I b0 I c0 In the three-phase standard current transformer 102, the input terminals of phase A, phase B, and phase C of the secondary current circuit are respectively connected to the second terminal I in the first switching circuit. an0 I bn0 I cn0 Connection. A first switch is provided between the first and second terminals of the same phase, so that when the first switch is closed, the secondary current loops of the corresponding phases of the first and second terminals in the three-phase standard current transformer 102 are short-circuited.

[0038] For a specific example, the first terminal I connected to the output terminal of phase A of the secondary current circuit in the three-phase standard current transformer 102 is... a0 And the second terminal I of the secondary current circuit A-phase input terminal in the three-phase standard current transformer 102. an0 A first switch J is set between them. a0 When the first switch J a0When closed, the secondary current circuit of phase A in the three-phase standard current transformer 102 is short-circuited. Similarly, the first terminal I corresponding to phase B is short-circuited. b0 Second terminal I bn0 A first switch J is set between them. b0 C corresponds to the first terminal I c0 Second terminal I cn0 A first switch J is set between them. c0 .

[0039] Similarly, the A-phase, B-phase, and C-phase output terminals of the secondary current loop in the tested distribution network transformer 101 are respectively connected to the third terminal I in the first switching circuit 304. ax I bx I cx The A-phase, B-phase, and C-phase input terminals of the secondary current loop in the tested distribution network transformer 101 are respectively connected to the fourth terminal I in the first switching circuit 304. anx I bnx I cnx Connection. A second switch is provided between the third and fourth terminals of the same phase, so that when the second switch is closed, the secondary current loops of the corresponding phases of the third and fourth terminals in the transformer under test 101 are short-circuited.

[0040] For a specific example, the third terminal I connected to the output terminal of phase A of the secondary current circuit in the current transformer 101 of the distribution network under test... ax And the fourth terminal I of the secondary current circuit A-phase input terminal in the tested distribution network transformer 101. anx A second switch J is installed between them. ax When the second switch J ax When closed, the secondary current loop of phase A in the tested distribution network transformer 101 is short-circuited. Similarly, the third terminal I corresponding to B is short-circuited. bx and the fourth terminal I bnx A second switch J is installed between them. bx C corresponds to the third terminal I cx and the fourth terminal I cnx A second switch J is installed between them. cx .

[0041] Furthermore, the first linkage switch J in the first switching circuit 304 I The first and third terminals, which are connected to the same phase, are used to input the secondary current of the three-phase standard current transformer 102 and the distribution network transformer 101 under test, which are in the same phase, to the single-phase digital current calibrator 305. Specifically, for example, when the first interlocking switch J... I Simultaneously connect the first terminal I corresponding to A. a0 With the third terminal I axAt that time, the secondary current of phase A output from the three-phase standard current transformer 102 and the current transformer 101 of the distribution network under test are simultaneously input to the single-phase digital current calibrator 305. Similarly, the first linkage switch J... I It can also connect the corresponding first terminal I of B at the same time. b0 With the third terminal I bx Or simultaneously connect the first terminal I corresponding to C. c0 With the third terminal I cx .

[0042] It should be noted that when the first linkage switch J I When switching to the current detection phase, the first and second switches corresponding to the non-detection phase need to be closed to short-circuit the secondary current loop of the three-phase standard current transformer 102 and the non-detection phase in the transformer 101 of the distribution network under test. Specifically, for example, if the current detection phase is phase A, then the first linkage switch J... I While switching to phase A, the first terminal I b0 With the second terminal I bn0 The first switch J between b0 First terminal I c0 With the second terminal I cn0 The first switch J between c0 Third terminal I bx With the fourth terminal I bnx The second switch J between bx Third terminal I cx With the fourth terminal I cnx The second switch J between cx All closed, and the first terminal I a0 and the second terminal I an0 The first switch J between a0 Disconnect to short-circuit the secondary current circuits of phase B and phase C in the three-phase standard current transformer 102 and the transformer 101 of the distribution network under test.

[0043] in, Figure 4 Middle I n0 I0 is the secondary current output terminal of the three-phase standard current transformer in the single-phase digital current calibrator, and I0 is the secondary current input terminal of the three-phase standard current transformer in the single-phase digital current calibrator. x For the secondary current input terminal of the single-phase digital current calibrator of the distribution network transformer under test, I nx This is the secondary current output terminal of the transformer in the distribution network under test for a single-phase digital current calibrator.

[0044] It is worth mentioning that, in this embodiment, the first host computer 306 automatically controls the first switch, the second switch, and the first linkage switch J. IThe opening and closing of the circuit enables accurate and rapid circuit switching to ensure that the secondary current of the input single-phase digital current calibrator 305 remains in phase.

[0045] In one embodiment, such as Figure 3 As shown, the field testing device for power distribution network transformers also includes: a voltage verification module comprising a second switching circuit, a single-phase digital voltage calibrator, and a second host computer. The single-phase digital voltage calibrator and the second host computer are respectively connected to the second switching circuit.

[0046] In this embodiment, the second switching circuit in the voltage verification module enables switching between different phases of the three-phase standard voltage transformer and the transformer under test in the distribution network. This allows the secondary voltages of the same phase output from both the three-phase standard voltage transformer and the transformer under test to be simultaneously input to the single-phase digital voltage calibrator. The single-phase digital voltage calibrator then uses a time-division multiplexing method to detect the voltage errors of different phases of the transformer under test, avoiding the need for separate calibration equipment for each phase. This reduces the number and size of voltage transformer calibrators, further improving the convenience of the overall testing device and enhancing the flexibility and specificity of voltage detection.

[0047] Specifically, such as Figure 5 As shown, the A-phase, B-phase, and C-phase output terminals of the secondary voltage circuit in the three-phase standard voltage transformer 103 are respectively connected to the fifth terminal U in the second switching circuit 301. a0 U b0 U c0 The A-phase, B-phase, and C-phase output terminals of the secondary voltage circuit in the tested distribution network transformer 101 are respectively connected to the sixth terminal U in the second switching circuit 301. ax U bx U cx Connection. The second linkage switch J in the second switching circuit 301. U Connect the fifth and sixth terminals, which are connected to the same phase, to input the secondary voltages of the three-phase standard voltage transformer 103 and the transformer 101 under test, which are in the same phase, to the single-phase digital voltage calibrator 302. For example, when the second linkage switch J... U Simultaneously connect the fifth terminal U corresponding to A. a0 With the sixth terminal U ax At the same time, the secondary voltages of phase A output from the three-phase standard voltage transformer 103 and the transformer 101 of the distribution network under test are simultaneously input to the single-phase digital voltage calibrator 302. Similarly, the second linkage switch J... U It can also connect to the fifth terminal U corresponding to B at the same time. b0 With the sixth terminal U bx Or simultaneously connect the fifth terminal U corresponding to C. c0 With the sixth terminal Ucx .

[0048] Additionally, the reference voltage U output from the neutral wire of the three-phase four-wire distribution network transformer 101 and the three-phase standard voltage transformer 103 are connected together. n0 U nx Through the seventh terminal U respectively n U n The input is sent to the single-phase digital voltage calibrator 302 to provide grounding protection for the three-phase standard voltage transformer 103 and the transformer under test in the distribution network, ensuring the stability of the phase voltage of the three-phase standard voltage transformer 103 and the transformer under test in the distribution network 101, and ensuring the normal operation and safety of the three-phase standard voltage transformer 103 and the transformer under test in the distribution network 101.

[0049] in, Figure 5 U0 is the secondary voltage input terminal of the three-phase standard voltage transformer in the single-phase digital voltage calibrator. x This is the secondary voltage input terminal of the transformer in the distribution network under test for a single-phase digital voltage calibrator.

[0050] It is worth mentioning that, in this embodiment, the second linkage switch J is automatically controlled by the second host computer 303. U The circuit can be opened and closed accurately and quickly, thereby ensuring that the secondary voltage input to the single-phase digital voltage calibrator 302 always remains in the same phase.

[0051] In one embodiment, such as Figure 6 As shown, the field testing device for distribution network transformers also includes: a three-phase voltage load box and a three-phase current load box.

[0052] Specifically, the three-phase voltage load box 601 is connected to the secondary voltage circuit of the transformer 101 of the distribution network under test, and the three-phase current load 302 is connected to the secondary current circuit of the transformer 101 of the distribution network under test.

[0053] In this embodiment, by connecting a three-phase voltage load box and a three-phase current load box, loads of different sizes are provided to the transformer under test, simulating the actual load conditions of the transformer under test. This allows the transformer under test to be in a state closer to actual operation during the test, ensuring that the transformer under test can stably and accurately output voltage and current signals when connected to actual loads, thereby more accurately evaluating the performance and accuracy of the transformer under actual working conditions.

[0054] Furthermore, such as Figure 7 As shown, this embodiment provides a field testing method for distribution network instrument transformers, applied to the aforementioned field testing device for distribution network instrument transformers. The method includes:

[0055] Step 701: The current verification module responds to the current detection command and determines the current detection result of the transformer under test based on the secondary current output of the three-phase standard current transformer and the transformer under test.

[0056] In this embodiment, after moving the detection device to the site of the distribution network transformer under test, there is no need to frequently replace the wiring of the three-phase standard current transformer. Simply connect the distribution network transformer under test to the detection device, and the user inputs the current detection command into the current verification module according to the detection requirements. Based on the current detection command, the current verification module obtains the secondary current output by the three-phase standard current transformer and the distribution network transformer under test, and calculates the error of the measured current of the distribution network transformer under test. This eliminates the need for cumbersome manual operation and improves the current detection efficiency and automation level of the transformer.

[0057] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully explain the specific implementation process of this embodiment, step 701, that is, the step in which the current verification module responds to the current detection command and determines the current detection result of the transformer under test based on the secondary current output by the three-phase standard current transformer and the transformer under test, specifically includes: the first host computer, according to the first phase to be measured indicated by the current detection command, determines the target first terminal, target second terminal, target third terminal and target fourth terminal connected to the first phase to be measured in the first switching circuit; the first host computer controls the first switch between the first terminal excluding the target first terminal and the second terminal excluding the target second terminal in the first switching circuit to close, so that the first phase to be measured in the three-phase standard current transformer is removed. The secondary current loop of the first phase is short-circuited; the first host computer controls the second switch in the first switching circuit to close between the third terminal of the target third terminal and the fourth terminal of the target fourth terminal, so as to short-circuit the secondary current loop of the transformer under test, excluding the first phase to be measured; the first host computer controls the first switch between the target first terminal and the target second terminal, and the second switch between the target third terminal and the target fourth terminal to open, and controls the first linkage switch in the first switching circuit to close, so as to connect the target first terminal and the target third terminal; the single-phase digital current calibrator receives the secondary current of the first phase to be measured output from the secondary current loop of the three-phase standard current transformer and the secondary current loop of the transformer under test, and determines the current detection result of the first phase to be measured of the transformer under test.

[0058] The current verification module includes a first switching circuit, a single-phase digital current calibrator, and a first host computer, with the single-phase digital current calibrator and the first host computer respectively connected to the first switching circuit.

[0059] In this embodiment, the first host computer in the current verification module detects the secondary current of each phase of the transformer under test in the distribution network according to the current detection command input by the user, using a time-division multiplexing method, and obtains the current detection results of each phase of the transformer under test, thereby improving the flexibility and pertinence of the detection.

[0060] It should be noted that the current detection command can include the phase to be detected this time, or it can include the detection sequence of the three phases. According to the instruction of the current detection command, the secondary current of the same phase is input to the single-phase digital current calibrator through the first linkage switch switching circuit, so as to obtain the current detection results of each phase of the transformer of the distribution network under test.

[0061] Specifically, the first host computer determines the target terminals connected to the first phase to be measured in the first switching circuit according to the first phase to be measured indicated by the current detection command. These target terminals are the first target terminal, the second target terminal, the third target terminal, and the fourth target terminal. The target terminal switching circuit is then used to simultaneously input the secondary current of the first phase to be measured output by the current transformer of the distribution network under test and the three-phase standard current transformer to the single-phase digital current calibrator.

[0062] For example, the first host computer controls the first switch between the first terminal of the target first terminal and the second terminal of the target second terminal in the first switching circuit to close, so as to short-circuit the secondary current loop of the non-detection phase in the three-phase standard current transformer, thereby ensuring the safety of detection.

[0063] Similarly, the first host computer controls the second switch in the first switching circuit to close between the third terminal of the target third terminal and the fourth terminal of the target fourth terminal, so as to short-circuit the secondary current loop of the non-detection phase in the transformer of the distribution network under test, so as to prevent the open circuit of the secondary current loop from causing serious harm to the equipment and personnel.

[0064] Furthermore, the first host computer controls the first switch between the first target terminal and the second target terminal, and the second switch between the third target terminal and the fourth target terminal to disconnect, and controls the first linkage switch in the first switching circuit to connect the first target terminal and the third target terminal, so that the secondary current of the first phase to be measured output by the current transformer under test and the three-phase standard current transformer is simultaneously input to the single-phase digital current calibrator through the first switching circuit. Thus, the single-phase digital current calibrator calculates the measurement error of the first phase to be measured of the current transformer under test based on the secondary current of the first phase to be measured output by the three-phase standard current transformer and the current transformer under test, and then determines the current detection result of the first phase to be measured of the current transformer under test.

[0065] For example, such as Figure 3 and Figure 4As shown, if the current detection command instructs to detect phases A, B, and C sequentially, then phase A is first taken as the first phase to be measured. At this time, the first terminal I connected to phase A... a0 Second terminal I an0 Third terminal I ax Fourth terminal I anx All are target terminals. Next, the first host computer 306 controls the first terminal I. b0 With the second terminal I bn0 The first switch J between b0 First terminal I c0 With the second terminal I cn0 The first switch J between c0 Third terminal I bx With the fourth terminal I bnx The second switch J between bx Third terminal I cx With the fourth terminal I cnx The second switch J between cx Closing, and controlling the first terminal I a0 and the second terminal I an0 The first switch J between a0 Disconnect to short-circuit the secondary current circuits of phase B and phase C in the three-phase standard current transformer 102 and the transformer 101 of the distribution network under test. Simultaneously, the first host computer 306 controls the first linkage switch J. I Simultaneously connect the first terminal I a0 With the third terminal I ax .

[0066] After the circuit switching is completed, the three-phase high-voltage power source 206 simultaneously applies the three-phase high current to both the three-phase standard current transformer 102 and the transformer under test (101) of the distribution network. This causes the secondary current of phase A output from both the three-phase standard current transformer 102 and the transformer under test (101) to be simultaneously input to the single-phase digital current calibrator 305. The single-phase digital current calibrator 305 then determines the current detection result of phase A of the transformer under test (101). Similarly, the first host computer 306 controls the first switch, the second switch, and the first linkage switch J. I The switching circuit sequentially inputs the secondary currents of phase B and phase C output from the three-phase standard current transformer 102 and the transformer under test 101 to the single-phase digital current calibrator 305, thereby determining the current detection results of phase B and phase C of the transformer under test 101 sequentially through the single-phase digital current calibrator 305.

[0067] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully explain the specific implementation process of this embodiment, the step of determining the current detection result of the first phase to be measured of the transformer under test specifically includes: converting the secondary current of the first phase to be measured output from the secondary current loop in the three-phase standard current transformer and the secondary current loop in the transformer under test into a first digital signal and a second digital signal, respectively; using the mean square root algorithm, determining the first amplitude of the first digital signal and the second amplitude of the second digital signal; performing spectral analysis on the first digital signal and the second digital signal, and using the discrete Fourier transform algorithm, determining the first phase information of the first digital signal and the second phase information of the first digital signal, respectively; determining the ratio difference based on the first amplitude and the second amplitude; determining the phase difference based on the first phase information and the second phase information; and determining the current detection result of the first phase to be measured of the transformer under test based on the ratio difference and the phase difference.

[0068] In this embodiment, by converting the secondary current into a digital signal and analyzing it, the ratio difference and phase difference between the tested distribution network transformer and the three-phase standard current transformer are accurately determined, thereby more accurately evaluating the performance of the tested distribution network transformer and identifying minute error changes.

[0069] For example, the secondary current of the first phase to be measured output by the three-phase standard current transformer and the transformer of the distribution network under test is converted into a first digital signal and a second digital signal respectively by an analog-to-digital converter (ADC) so as to represent the secondary current signal as a series of discrete digital values, which facilitates digital signal processing.

[0070] Next, for the first digital signal of the three-phase standard current transformer, the current amplitude is determined by calculating its root mean square (RMS) value. Specifically, for example, the first digital signal over a sampling period can be summed to obtain the first amplitude by averaging and taking the square root. Similarly, the second digital signal of the transformer under test in the distribution network is processed in the same way to obtain the second amplitude.

[0071] Meanwhile, for the first data signal and the second digital signal, the Discrete Fourier Transform (DFT) algorithm or other efficient spectrum analysis algorithms can be used to analyze the spectrum information of the secondary current, thereby quickly and accurately calculating the phase of the two secondary currents and obtaining the first phase information and the second phase information of the first digital signal.

[0072] Furthermore, based on the difference between the second amplitude and the first amplitude, and the ratio of the second amplitude to the first amplitude, a ratio difference is determined to reflect the difference in amplitude between the three-phase standard current transformer and the transformer in the distribution network under test. Simultaneously, based on the difference between the first phase information and the second phase information, a phase difference is determined to reflect the difference in phase angle between the three-phase standard current transformer and the transformer in the distribution network under test. Then, based on the ratio difference and the phase difference, the current detection result of the first phase to be measured in the transformer in the distribution network under test is determined, thus enabling accurate calculation of the error of the transformer in the distribution network under test using the digital comparison method.

[0073] In one embodiment, the on-site testing method for distribution network transformers further includes: identifying the accuracy class of the distribution network transformer under test; if the difference between the preset accuracy class of the three-phase standard current transformer and the accuracy class of the distribution network transformer under test does not meet the preset conditions, then controlling the first linkage switch to open, and controlling both the first switch and the second switch to close, and determining the abnormal information; displaying the abnormal information.

[0074] In this embodiment, the accuracy class of the tested distribution network transformer and the three-phase standard current transformer is matched to ensure that the three-phase standard current transformer and the tested distribution network transformer have a reasonable degree of matching in accuracy class. This is to prevent inaccurate test results due to mismatch in accuracy class, which would fail to truly reflect the performance of the tested transformer and improve the reliability and accuracy of the test.

[0075] For example, a high-definition camera can be used to photograph the nameplate of the transformer under test in the distribution network. Image recognition algorithms can then automatically identify the text information on the nameplate, including the accuracy class. For instance, Optical Character Recognition (OCR) technology can be used to convert the captured nameplate image into editable text, from which the accuracy class information can be extracted. Alternatively, high-precision measuring equipment can be connected to monitor and analyze the output signal of the transformer under test in real time. Transformers with different accuracy classes will exhibit differences in output signal stability and accuracy. By analyzing the characteristics of the output signal, such as fluctuation range, noise level, and linearity, the accuracy class of the transformer under test can be determined.

[0076] Furthermore, if the difference between the preset accuracy class of the three-phase standard current transformer and the identified accuracy class of the distribution network transformer under test does not meet the preset conditions, the first linkage switch is opened, and both the first and second switches are closed to disconnect the connection between the three-phase standard current transformer, the distribution network transformer under test, and the single-phase digital current calibrator. This ensures testing safety while avoiding erroneous detection, thus improving the reliability and accuracy of the test. Simultaneously, abnormal information, such as an accuracy class mismatch, is identified and displayed to prompt staff for further investigation.

[0077] The preset conditions can be set according to the requirements of the digital comparison method, where the accuracy class of the three-phase standard current transformer is three levels higher than that of the distribution network transformer being tested. For example, a three-phase standard current transformer with a 600A / 5A ratio and an accuracy class of 0.02S can be used to cover distribution network transformers of various ratios in the field. Furthermore, the measurement range of the three-phase standard current transformer is selected based on the maximum current requirement of the three-phase standard current transformer in the field. Similarly, since over 95% of distribution network transformers are at the 10kV voltage level, to meet the needs of field testing, the standard voltage transformer is set to 10kV with an accuracy class of 0.05.

[0078] Step 702: In response to the voltage detection command, the voltage verification module determines the voltage detection result of the transformer under test based on the secondary voltage output of the three-phase standard voltage transformer and the transformer under test.

[0079] In this embodiment, similar to the current verification module, the detection device is moved to the application site of the transformer under test in the distribution network. After connecting to the transformer under test, the user inputs a voltage detection command into the voltage verification module according to the detection requirements. Based on the voltage detection command, the voltage verification module obtains the secondary voltage output by the three-phase standard voltage transformer and the transformer under test, and calculates the error of the voltage measurement of the transformer under test. This avoids tedious manual operation, improves voltage detection efficiency, and enhances its automation level.

[0080] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully explain the specific implementation process of this embodiment, step 702, that is, the voltage verification module responds to the voltage detection command and determines the voltage detection result of the transformer under test based on the secondary voltage output by the three-phase standard voltage transformer and the transformer under test, includes: the second host computer determines the target fifth terminal and the target sixth terminal connected to the second phase under test in the second switching circuit according to the second phase under test indicated by the voltage detection command; the second host computer controls the second linkage switch in the second switching circuit to close to connect the target fifth terminal and the target sixth terminal; the single-phase digital voltage calibrator receives the secondary voltage of the second phase under test output by the secondary voltage circuit in the three-phase standard voltage transformer and the secondary voltage circuit in the transformer under test, and determines the voltage detection result of the second phase under test of the transformer under test.

[0081] The voltage verification module includes a second switching circuit, a single-phase digital voltage calibrator, and a second host computer. The single-phase digital voltage calibrator and the second host computer are respectively connected to the second switching circuit.

[0082] In this embodiment, the second host computer in the voltage verification module, based on the voltage detection command input by the user, also uses the time-division multiplexing method to detect the secondary voltage of each phase of the transformer under test in the distribution network, thereby obtaining the voltage detection results of each phase of the transformer under test in the distribution network, improving the efficiency and flexibility of the detection.

[0083] It should be noted that, similar to the current detection command, the voltage detection command can also include the phase to be detected this time, or include the detection sequence of the three phases. Thus, according to the voltage detection command, the secondary voltage of the same phase is input to the single-phase digital voltage calibrator through the second linkage switch to obtain the voltage detection results of each phase of the transformer in the distribution network under test.

[0084] For example, such as Figure 3 and Figure 5 As shown, if the voltage detection command instructs to detect phases A, B, and C sequentially, then phase A is first taken as the first phase to be measured. At this time, the fifth terminal U connected to phase A... a0 With the sixth terminal U ax For the target fifth terminal and the target sixth terminal. Next, the second host computer 303 controls the second linkage switch J. U Simultaneously connect the fifth terminal U a0 With the sixth terminal U ax Then, the three-phase high-current supplied by the three-phase high-voltage power source 206 is simultaneously applied to the three-phase standard voltage transformer 103 and the transformer under test 101, so that the secondary voltage of phase A output from the three-phase standard voltage transformer 103 and the transformer under test 101 is simultaneously input to the single-phase digital voltage calibrator 302, thereby determining the voltage detection result of phase A of the transformer under test 101 through the single-phase digital voltage calibrator 302. Similarly, the second linkage switch J is controlled by the second host computer 303. U The switching circuit sequentially inputs the secondary voltages of phase B and phase C output from the three-phase standard voltage transformer 103 and the transformer under test 101 to the single-phase digital voltage calibrator 302, thereby determining the voltage detection results of phase B and phase C of the transformer under test 101 sequentially through the single-phase digital current calibrator 302.

[0085] It should be noted that the process of determining the voltage detection result based on the secondary voltage is the same as the process of determining the current detection result based on the secondary current in the above embodiment, and will not be repeated here.

[0086] It is worth mentioning that if the transformer under test is a combined transformer, after switching the circuit through the first switch, the second switch, the first linkage switch and the second linkage switch, the three-phase high voltage and high current provided by the three-phase high voltage power source are simultaneously applied to the three-phase standard voltage and current transformers and the transformer under test, simulating the actual operating conditions of the transformer under test, so as to simultaneously detect the error of the measured current and the error of the measured voltage of the transformer under test.

[0087] In one embodiment, the on-site testing method for distribution network transformers further includes: if the current detection result or voltage detection result does not meet the preset error range, then the tested distribution network transformer is determined to be unqualified, and based on the current detection result or voltage detection result that does not meet the preset error range, a warning message is determined; and the warning message is displayed.

[0088] In this embodiment, the combination of automated detection and early warning can quickly and accurately determine the qualification of the tested distribution network transformers, reducing errors and time costs associated with manual judgment. Simultaneously, clear early warning information enables operators to take swift action, improving work efficiency.

[0089] For example, allowable error ranges can be preset based on the standard specifications, accuracy requirements, and relevant industry standards of the instrument transformer. If the current or voltage detection result is within the preset error range, the tested distribution network instrument transformer is deemed qualified; otherwise, it is deemed unqualified. Warning information is generated based on current or voltage detection results that do not conform to the preset error range. The warning information may include specific unqualified parameters (such as current or voltage values ​​exceeding the error range), the type of unqualified parameter (whether it is current or voltage unqualified), and possible problem indications (such as possible causes of faults). The determined warning information is displayed via a screen, indicator lights, sound, etc., so that operators can promptly understand the testing status and problems of the tested distribution network instrument transformer.

[0090] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0091] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A field testing device for distribution network instrument transformers, characterized in that, The device is connected to the transformer in the distribution network under test, and the device includes: a three-phase standard voltage transformer, a three-phase standard current transformer, a voltage verification module and a current verification module. The primary current loop of the three-phase standard current transformer is connected in series with the primary current loop of the transformer in the distribution network under test. The primary voltage circuit of the three-phase standard voltage transformer and the primary voltage circuit of the transformer in the distribution network under test are connected in parallel; The secondary current loop in the three-phase standard current transformer and the secondary current loop in the distribution network transformer under test are respectively connected to the current verification module. The current verification module is used to receive the secondary current output by the three-phase standard current transformer and the distribution network transformer under test, and to determine the current detection result of the distribution network transformer under test. The secondary voltage circuit of the three-phase standard voltage transformer and the secondary voltage circuit of the distribution network transformer under test are respectively connected to the voltage verification module. The voltage verification module is used to receive the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test, and to determine the voltage detection result of the distribution network transformer under test. The current verification module includes a first switching circuit, a single-phase digital current calibrator, and a first host computer, wherein the single-phase digital current calibrator and the first host computer are respectively connected to the first switching circuit. The A-phase, B-phase, and C-phase output terminals of the secondary current circuit in the three-phase standard current transformer are respectively connected to the first terminal in the first switching circuit. The input terminals of phase A, phase B, and phase C of the secondary current circuit in the three-phase standard current transformer are respectively connected to the second terminal in the first switching circuit. A first switch is provided between the first terminal and the second terminal, which are connected in the same phase; The A-phase, B-phase, and C-phase output terminals of the secondary current loop in the transformer under test are respectively connected to the third terminal in the first switching circuit. The A-phase, B-phase, and C-phase input terminals of the secondary current circuit in the transformer under test are respectively connected to the fourth terminal in the first switching circuit. A second switch is provided between the third terminal and the fourth terminal, which are connected in the same phase; In the first switching circuit, the first linkage switch is connected to the first terminal and the third terminal, which are connected in the same phase. The first host computer is used to control the opening and closing of the first switch, the second switch and the first linkage switch; The voltage verification module includes a second switching circuit, a single-phase digital voltage calibrator, and a second host computer, wherein the single-phase digital voltage calibrator and the second host computer are respectively connected to the second switching circuit; The A-phase, B-phase, and C-phase output terminals of the secondary voltage circuit in the three-phase standard voltage transformer are respectively connected to the fifth terminal in the second switching circuit. The A-phase, B-phase, and C-phase output terminals of the secondary voltage circuit in the transformer under test are respectively connected to the sixth terminal in the second switching circuit. The single-phase digital voltage calibrator receives the reference voltage output from the secondary voltage circuit of the three-phase standard voltage transformer and the secondary voltage circuit of the transformer in the distribution network under test through the second switching circuit. In the second switching circuit, the second linkage switch is connected to the fifth terminal and the sixth terminal, which are connected in the same phase. The second host computer is used to control the opening and closing of the second linkage switch.

2. The field testing device for distribution network transformers according to claim 1, characterized in that, The device further includes: a three-phase voltage load box and a three-phase current load box, wherein: The three-phase voltage load box is connected to the secondary voltage circuit of the transformer in the distribution network under test; the three-phase current load box is connected to the secondary current circuit of the transformer in the distribution network under test.

3. A method for on-site testing of distribution network instrument transformers, applied to the on-site testing device for distribution network instrument transformers as described in any one of claims 1-2, characterized in that, The method includes: The current verification module responds to the current detection command and determines the current detection result of the transformer under test based on the secondary current output by the three-phase standard current transformer and the transformer under test. The voltage verification module responds to the voltage detection command and determines the voltage detection result of the transformer under test based on the secondary voltage output by the three-phase standard voltage transformer and the transformer under test.

4. The method for on-site testing of distribution network instrument transformers according to claim 3, characterized in that, The current verification module includes a first switching circuit, a single-phase digital current calibrator, and a first host computer, wherein the single-phase digital current calibrator and the first host computer are respectively connected to the first switching circuit; the current verification module responds to a current detection command and determines the current detection result of the tested distribution network transformer based on the secondary current output by the three-phase standard current transformer and the transformer under test, including: The first host computer determines the target first terminal, target second terminal, target third terminal and target fourth terminal connected to the first phase to be measured in the first switching circuit according to the first phase to be measured indicated by the current detection command. The first host computer controls the first switch in the first switching circuit to close between the first terminal of the target first terminal and the second terminal of the target second terminal, so as to short-circuit the secondary current loop of the three-phase standard current transformer after removing the first phase to be measured. The first host computer controls the second switch in the first switching circuit to close between the third terminal of the target third terminal and the fourth terminal of the target fourth terminal, so as to short-circuit the secondary current loop of the transformer of the distribution network under test, after removing the first phase to be measured. The first host computer controls the first switch between the first target terminal and the second target terminal, and the second switch between the third target terminal and the fourth target terminal to be disconnected, and controls the first linkage switch in the first switching circuit to be closed to connect the first target terminal and the third target terminal; The single-phase digital current calibrator receives the secondary current of the first phase to be measured output by the three-phase standard current transformer and the transformer under test in the distribution network, and determines the current detection result of the first phase to be measured of the transformer under test in the distribution network.

5. The method for on-site testing of distribution network instrument transformers according to claim 4, characterized in that, The determination of the current detection result of the first phase to be measured of the transformer in the distribution network includes: The secondary currents of the first phase to be measured output by the three-phase standard current transformer and the transformer of the distribution network under test are converted into a first digital signal and a second digital signal, respectively. The first amplitude of the first digital signal and the second amplitude of the second digital signal are determined using the mean square root algorithm. Spectral analysis is performed on the first digital signal and the second digital signal, and the first phase information and the second phase information of the first digital signal are determined by using the discrete Fourier transform algorithm. Determine the ratio difference based on the first amplitude and the second amplitude; The phase difference is determined based on the first phase information and the second phase information; Based on the ratio difference and the phase difference, the current detection result of the first phase to be measured of the transformer in the distribution network under test is determined.

6. The method for on-site testing of distribution network instrument transformers according to claim 4, characterized in that, The method further includes: Identify the accuracy class of the measured distribution network transformer; If the difference between the preset accuracy class of the three-phase standard current transformer and the accuracy class of the distribution network transformer under test does not meet the preset conditions, the first linkage switch is controlled to open, and both the first switch and the second switch are controlled to close, and abnormal information is determined. Display the aforementioned error information.

7. The method for on-site testing of distribution network instrument transformers according to claim 3, characterized in that, The voltage verification module includes a second switching circuit, a single-phase digital voltage calibrator, and a second host computer, wherein the single-phase digital voltage calibrator and the second host computer are respectively connected to the second switching circuit; the voltage verification module responds to a voltage detection command and determines the voltage detection result of the tested distribution network transformer based on the secondary voltage output of the three-phase standard voltage transformer and the transformer under test, including: The second host computer determines the target fifth terminal and the target sixth terminal connected to the second phase under test in the second switching circuit according to the second phase under test indicated by the voltage detection command. The second host computer controls the second linkage switch in the second switching circuit to close, so as to connect the target fifth terminal and the target sixth terminal; The single-phase digital voltage calibrator receives the secondary voltage of the second phase to be measured output by the three-phase standard voltage transformer and the transformer under test in the distribution network, and determines the voltage detection result of the second phase to be measured of the transformer under test in the distribution network.

8. The method for on-site testing of distribution network instrument transformers according to claim 3, characterized in that, The method further includes: If the current detection result or the voltage detection result does not meet the preset error range, the tested distribution network transformer is determined to be unqualified, and a warning message is determined based on the current detection result or the voltage detection result that does not meet the preset error range. The warning information is displayed.

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