Power distribution network mutual inductor field detection device and method

Abstract

The invention discloses a field detection device and method for a power distribution network mutual inductor, and the method employs a detection method based on a digital comparison method, does not need the consistent transformation ratio of a three-phase standard current mutual inductor and a detected power distribution network mutual inductor, and only needs the verification point of the detected power distribution network mutual inductor to be within the effective traceability range of the three-phase standard current mutual inductor. The three-phase standard current transformer with the large transformation ratio can be selected to cover the detected power distribution network transformers with various transformation ratios on site, the size and weight of the detection device are effectively reduced, the convenience of the detection device is improved, and therefore the detected power distribution network transformers can be detected on the use site of the detected power distribution network transformers. And each device in the detection device can adapt to the tested power distribution network mutual inductors with various transformation ratios only by wiring for a small number of times, so that the on-site wiring times and time are greatly reduced, the detection efficiency and safety are improved, and the method has the advantages of simplicity, economy, scientificity, practicability, strong operability, low cost and the like.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to an on-site detection device and method for a distribution network transformer. Background Art

[0002] The transformer of the distribution network is the hub equipment between the primary and secondary of the distribution network system. It is a national mandatory verification instrument and is mostly installed in power plants, substations, special transformers / public transformers, etc. for power metering and relay protection.

[0003] In the related technology, most of the used distribution network transformers are disassembled and tested in the laboratory. With the advancement of the national ultra-high voltage transmission project, the number of distribution network transformers that need to be tested on site is increasing, but there is a shortage of on-site testing equipment. Due to the large number, heavy weight, large volume and poor convenience of the testing equipment in the laboratory, it is difficult to test the distribution network transformers at the site of use. In addition, the wiring of the testing equipment in the laboratory is complicated, and it takes more than a dozen wirings to complete a test. The calibration efficiency is low, and there are also great safety hazards, which cannot meet the growing demand for on-site testing of distribution network transformers. Summary of the invention

[0004] In view of this, the present application provides a distribution network transformer on-site detection device and method, which greatly reduces the volume and weight of the detection device, can be directly applied to the distribution network transformer use site, improves the convenience of detection, reduces the number of wiring times, and improves the efficiency and safety of detection.

[0005] According to one aspect of the present application, a field detection device for a distribution network transformer is provided, the device is connected to a distribution network transformer under test, and the device comprises: 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 in the three-phase standard current transformer is connected in series with the primary current loop in the distribution network transformer under test; the primary voltage loop in the three-phase standard voltage transformer is connected in parallel with the primary voltage loop in the distribution network transformer under test; the secondary current loop in the three-phase standard current transformer is connected in parallel with the secondary current loop in the distribution network transformer under test; The secondary current loops are respectively connected to the current verification module, and 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 determine the current detection result of the distribution network transformer under test; the secondary voltage loop in the three-phase standard voltage transformer and the secondary voltage loop in the distribution network transformer under test are respectively connected to the voltage verification module, and 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 determine the voltage detection result of the distribution network transformer under test.

[0006] According to another aspect of the present application, a distribution network transformer on-site detection method is provided, which is applied to the distribution network transformer on-site detection device described above, and the method includes: a current verification module responds to a current detection instruction, and determines the current detection result of the distribution network transformer under test according to the secondary current output by the three-phase standard current transformer and the distribution network transformer under test; a voltage verification module responds to a voltage detection instruction, and determines the voltage detection result of the distribution network transformer under test according to the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test.

[0007] By means of the above technical scheme, the present application provides a field detection device and method for distribution network transformers, which adopts a detection method based on a digital comparison method. It is not necessary for the three-phase standard current transformer to have the same ratio as the distribution network transformer under test. It is only necessary for the calibration point of the distribution network transformer under test to be within the effective traceability range of the three-phase standard current transformer. A three-phase standard current transformer with a larger ratio can be selected to cover the distribution network transformers under test with various ratios on site, which effectively reduces the volume and weight of the detection device and improves the convenience of the detection device, so that the distribution network transformer under test can be detected at the site where the distribution network transformer under test is used. In addition, each device in the detection device only needs a small number of wirings to adapt to the distribution network transformers under test with various ratios, which greatly reduces the number and time of on-site wiring, improves the efficiency and safety of the detection, and has the advantages of simple method, economy, science, practicality, strong operability, and low cost.

[0008] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0010] Figure 1 A structural block diagram of a distribution network transformer field detection device provided in an embodiment of the present application is shown;

[0011] Figure 2 A structural block diagram of another distribution network transformer field detection device provided in an embodiment of the present application is shown;

[0012] Figure 3 A structural block diagram of another distribution network transformer field detection device provided in an embodiment of the present application is shown;

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

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

[0015] Figure 6 A structural block diagram of another distribution network transformer field detection device provided in an embodiment of the present application is shown;

[0016] Figure 7 A schematic diagram of a flow chart of a method for on-site detection of a transformer in a power distribution network provided in an embodiment of the present application is shown;

[0017] Figure 8 A schematic diagram of the structure of an analog comparison method detection device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0018] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0019] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0020] Those skilled in the art will appreciate that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the 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 refer to an element as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, or there may be intermediate elements. In addition, the "connection" or "connection" used herein may include wireless connection or wireless fusion. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0021] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0022] The distribution network transformer is the hub equipment between the primary and secondary of the distribution network system. It is a national mandatory verification instrument and is mostly installed in power plants, substations, special transformers / public transformers, etc. for power metering and relay protection. With the release and implementation of the national verification regulations JJG1165-2019 "Three-phase combination transformers", distribution network transformers need to be tested in the laboratory and on-site under the rated working voltage.

[0023] At present, the detection of distribution network transformers is mostly carried out in laboratories, which makes the on-site detection of distribution network transformers face the following difficulties: First, the calibration of current boosters and standard current transformers under high voltage requires special shielding and insulation treatment, which causes the volume and weight to increase by nearly one-fold compared to the original equipment, making it inconvenient to carry for on-site calibration. Second, distribution network transformers have a variety of operating environments such as poles, box transformers, and metering cabinets. The existing detection equipment is difficult to adapt to various complex environments and portability requirements on site. Third, the calibration of traditional current transformers in the laboratory adopts the analog 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 various types of current transformer ratios under test, the current transformation ratios of the standard current transformer are more than 20, which is more than double the volume and weight of the single-ratio standard current transformer. It takes more than ten times of wiring to complete a test. When the transformation ratio of the transformer under test changes, it needs to be rewired, which leads to low verification efficiency, great safety hazards and low safety factor.

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

[0025] In view of this, a field detection device for a power distribution network transformer is provided in this embodiment, such as Figure 1 As shown, the device is connected to the distribution network transformer 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.

[0026] In this embodiment, a digital comparison method is adopted to calculate the error of the measured current (voltage) of the tested distribution network transformer according to the secondary current (voltage) of the tested distribution network transformer and the standard transformer. It is not necessary for the transformation ratio of the three-phase standard current transformer and the tested distribution network transformer to be consistent. It is only required that the calibration point of the tested distribution network transformer (that is, the specific current value point for detection) is within the effective traceability range of the three-phase standard current transformer. For this purpose, a three-phase standard current transformer with a larger transformation ratio can be selected to cover all types of tested distribution network transformers with various transformation ratios on site, which can greatly reduce the volume and weight of the three-phase standard current transformer, thereby improving the convenience of the overall detection device.

[0027] Specifically, 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 three-phase large current is input to the three-phase standard current transformer 102 and the distribution network transformer 101 under test at the same time, 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 loop in the three-phase standard current transformer 102 and the secondary current loop in the distribution network transformer 101 under test are respectively connected to the current verification module 105, so that the low current part output after conversion between the three-phase standard current transformer 102 and the distribution network transformer 101 under test, that is, the secondary current, is respectively input into the current verification module 105, so that the current verification module 105 calculates the error of the measured current of the distribution network transformer 101 under test according to the secondary current output by the three-phase standard current transformer 102 and the distribution network transformer 101 under test, and then determines the current detection result of the distribution network transformer 101 under test.

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

[0030] Furthermore, the secondary voltage circuit in the three-phase standard voltage transformer 103 and the secondary voltage circuit in the distribution network transformer 101 under test are respectively connected to the voltage verification module 104, so that the low voltage part output after conversion between the three-phase standard voltage transformer 103 and the distribution network transformer 101 under test, that is, the secondary voltage, is respectively input into the voltage verification module 104, so that the voltage verification module 104 calculates the error of the measured voltage of the distribution network transformer 101 under test according to the secondary voltage output by the three-phase standard voltage transformer 103 and the distribution network transformer 101 under test, and then the voltage detection result of the distribution network transformer 101 under test.

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

[0032] It is worth mentioning that the corresponding part of the detection device can be selected according to the specific measurement type of the distribution network transformer 101 to detect the distribution network transformer 101 under test. For example, if the distribution network transformer 101 under test is a current transformer, the distribution network transformer 101 under test can be connected with the three-phase standard current transformer 102 and the current verification module 105, so as to detect the error of the current measured by the distribution network transformer 101 under test, and obtain the current detection result of the distribution network transformer 101 under test. Similarly, if the distribution network transformer 101 under test is a voltage transformer, the distribution network transformer 101 under test can be connected with the three-phase standard voltage transformer 103 and the voltage verification module 104, so as to detect the error of the voltage measured by the distribution network transformer 101 under test, and obtain the voltage detection result of the distribution network transformer 101 under test. Furthermore, if the distribution network transformer 101 under test is a combined transformer composed of a voltage transformer and a current transformer, the distribution network transformer 101 under test 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, and the errors of the measured voltage and the measured current of the distribution network transformer 101 under test are respectively detected, so as to obtain the current detection result and the voltage detection result of the distribution network transformer 101 under test.

[0033] In actual application scenarios, three-phase standard current transformers require special shielding and insulation treatment, and the error change caused by the leakage current cannot exceed one tenth of the error limit.

[0034] In one embodiment, if Figure 3As shown, the field detection device for transformers in the power distribution network further includes: the current verification module includes a first switching circuit, a single-phase digital current verification instrument and a first host computer. The single-phase digital current verification instrument and the first host computer are respectively connected to the first switching circuit.

[0035] In this embodiment, the switching between different phases of the three-phase standard current transformer and the distribution network transformer under test is achieved through the first switching circuit in the current verification module, so that the secondary currents of the same phase output by the three-phase standard current transformer and the distribution network transformer under test are simultaneously input into the single-phase digital current calibrator, so that the current errors of different phases of the distribution network transformer under test are detected separately by the single-phase digital current calibrator in a time-sharing multiplexing manner, thereby reducing the volume and weight of the current transformer calibrator, further improving the convenience of the overall detection device, and improving the flexibility and pertinence of current detection.

[0036] Among them, Figure 4 As shown, based on the regulation that the secondary current circuit of the current transformer cannot be in a disconnected state, the three-phase output end and the three-phase input end of the secondary current circuit of the three-phase standard current transformer 102 and the tested distribution network transformer 101 are respectively connected to the terminals in the first switching circuit 304, so as to realize the short circuit of the secondary current circuit of the non-detection phase through the first switching circuit 304, so as to prevent the open circuit of the secondary current circuit from causing serious harm to equipment and personnel, thereby ensuring the safety of detection.

[0037] Specifically, the A-phase, B-phase, and C-phase output terminals of the secondary current loop 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 The A-phase, B-phase, and C-phase input terminals of the secondary current loop of the three-phase standard current transformer 102 are respectively connected to the second terminal I an0 ,I bn0 ,I cn0 A first switch is provided between the first terminal and the second terminal connected with the same phase, so that when the first switch is closed, the secondary current loop of the phase corresponding to the first terminal and the second terminal in the three-phase standard current transformer 102 is short-circuited.

[0038] For example, the first terminal I connected to the output end of the A phase of the secondary current loop in the three-phase standard current transformer 102 a0 , and the second terminal I connected to the A-phase input end of the secondary current loop in the three-phase standard current transformer 102 an0 A first switch J is provided between a0 , when the first switch J a0When closed, the secondary current loop of phase A in the three-phase standard current transformer 102 is short-circuited. b0 and the second terminal I bn0 A first switch J is provided between b0 , C corresponds to the first terminal I c0 and the second terminal I cn0 A first switch J is provided between 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 anx ,I bnx ,I cnx A second switch is provided between the third terminal and the fourth terminal connected with the same phase, so that when the second switch is closed, the secondary current loop of the phase corresponding to the third terminal and the fourth terminal in the tested distribution network transformer 101 is short-circuited.

[0040] For example, the third terminal I connected to the output end of the A phase of the secondary current loop of the tested distribution network transformer 101 ax , and the fourth terminal I connected to the A-phase input terminal of the secondary current loop in the tested distribution network transformer 101 anx A second switch J is provided between ax , when the second switch J ax When closed, the A-phase secondary current loop in the tested distribution network transformer 101 is short-circuited. bx and the fourth terminal I bnx A second switch J is provided between bx , C corresponds to the third terminal I cx and the fourth terminal I cnx A second switch J is provided between cx .

[0041] Furthermore, the first linkage switch J in the first switching circuit 304 I The first terminal and the third terminal of the same phase are connected to input the secondary current of the same phase output by the three-phase standard current transformer 102 and the tested distribution network transformer 101 into the single-phase digital current tester 305. For example, when the first linkage switch J I At the same time, connect the first terminal I corresponding to A a0 With the third terminal I axWhen the three-phase standard current transformer 102 and the A-phase secondary current output by the tested distribution network transformer 101 are simultaneously input to the single-phase digital current tester 305. I You can also connect the first terminal I corresponding to B at the same time b0 With the third terminal I bx , or connect the first terminal I corresponding to C at the same time 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 switch and the second switch corresponding to the non-detection phase need to be closed to short-circuit the secondary current loop of the non-detection phase between the three-phase standard current transformer 102 and the tested distribution network transformer 101. For example, if the current detection phase is phase A, the first linkage switch J I When switching to phase A, connect 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 are closed, and the first terminal I a0 and the second terminal I an0 The first switch J between a0 Disconnect to short-circuit the B-phase and C-phase secondary current loops of the three-phase standard current transformer 102 and the tested distribution network transformer 101.

[0043] in, Figure 4 Middle I n0 I0 is the secondary current input terminal of the three-phase standard current transformer of the single-phase digital current calibrator, I x It is the secondary current input terminal of the transformer of the distribution network under test of the single-phase digital current tester. nx It is the secondary current output terminal of the transformer of the distribution network under test of the 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 single-phase digital current tester 305 can realize accurate and rapid circuit switching to ensure that the secondary current input to the single-phase digital current tester 305 remains in phase.

[0045] In one embodiment, if Figure 3 As shown, the field detection device for transformers in the power distribution network further includes: the voltage verification module includes a second switching circuit, a single-phase digital voltage verification instrument and a second host computer. The single-phase digital voltage verification instrument and the second host computer are respectively connected to the second switching circuit.

[0046] In this embodiment, the switching between different phases of the three-phase standard voltage transformer and the distribution network transformer under test is realized through the second switching circuit in the voltage verification module, so that the secondary voltages of the same phase output by the three-phase standard voltage transformer and the distribution network transformer under test are simultaneously input into the single-phase digital voltage calibrator, so that the voltage errors of different phases of the distribution network transformer under test are detected separately by the single-phase digital voltage calibrator in a time-sharing multiplexing manner, avoiding the need to equip each phase with an independent verification device, thereby reducing the number and volume of voltage transformer calibrators, further improving the convenience of the overall detection device, and improving the flexibility and pertinence of voltage detection.

[0047] Specifically, 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 ax , U bx , U cx The second linkage switch J in the second switching circuit 301 U The third terminal is connected to the fifth terminal and the sixth terminal of the same phase, so as to input the secondary voltage of the same phase output by the three-phase standard voltage transformer 103 and the distribution network transformer 101 to the single-phase digital voltage tester 302. For example, when the second linkage switch J U At the same time, connect the fifth terminal U corresponding to A a0 With the sixth terminal U ax When the three-phase standard voltage transformer 103 and the A-phase secondary voltage output by the tested distribution network transformer 101 are simultaneously input to the single-phase digital voltage tester 302. U You can also connect the fifth terminal U corresponding to B at the same time b0 With the sixth terminal U bx , or connect the fifth terminal U corresponding to C at the same time c0 With the sixth terminal Ucx .

[0048] In addition, the reference voltage U output by the three-phase standard voltage transformer 103 and the neutral line of the three-phase four-wire distribution network transformer 101 under test is n0 , U nx Through the seventh terminal U n , U n 'Input to the single-phase digital voltage tester 302 to provide grounding protection for the three-phase standard voltage transformer 103 and the distribution network transformer under test, ensure the phase voltage stability of the three-phase standard voltage transformer 103 and the distribution network transformer under test 101, and ensure the normal operation and safety of the three-phase standard voltage transformer 103 and the distribution network transformer under test 101.

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

[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 opening and closing of the single-phase digital voltage tester 302 can accurately and quickly complete the circuit switching, thereby ensuring that the secondary voltage input to the single-phase digital voltage tester 302 always remains in the same phase.

[0051] In one embodiment, if Figure 6 As shown, the distribution network transformer on-site detection device 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 tested distribution network transformer 101, and the three-phase current load 302 is connected to the secondary current circuit of the tested distribution network transformer 101.

[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 for the distribution network transformer under test, simulating the actual load condition of the distribution network transformer under test, so that the distribution network transformer under test is in a state closer to the actual operation during the test process, ensuring that the distribution network transformer under test can stably and accurately output voltage and current signals when connected to the actual load, thereby more accurately evaluating the performance and accuracy of the transformer under actual working conditions.

[0054] Furthermore, if Figure 7 As shown, in this embodiment, a method for on-site detection of a distribution network transformer is provided, which is applied to the above-mentioned on-site detection device for distribution network transformer, and the method includes:

[0055] Step 701: In response to a current detection instruction, a current verification module determines a current detection result of the distribution network transformer under test according to secondary currents output by a three-phase standard current transformer and the distribution network transformer under test.

[0056] In this embodiment, after the detection device is moved to the use site of the distribution network transformer under test, there is no need to frequently replace the line of the three-phase standard current transformer. It is only necessary to connect the distribution network transformer under test to the detection device. The user inputs the current detection instruction in the current verification module according to the detection requirements. The current verification module obtains the secondary current output by the three-phase standard current transformer and the distribution network transformer under test based on the current detection instruction, and calculates the error of the measured current of the distribution network transformer under test. There is no need for tedious manual operation, which improves the current detection efficiency and automation level of the transformer.

[0057] Further, as a refinement and expansion of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, step 701, that is, the current verification module responds to the current detection instruction, and determines the current detection result of the distribution network transformer under test according to the secondary current output by the three-phase standard current transformer and the distribution network transformer under test, specifically includes: the first host computer determines the target first terminal, the target second terminal, the target third terminal and the 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 instruction; 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 to be measured is short-circuited; the first host computer controls the second switch between the third terminal excluding the target third terminal and the fourth terminal excluding the target fourth terminal in the first switching circuit to close, so as to short-circuit the secondary current loop of the first phase to be measured in the tested distribution network transformer except 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 be opened, 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 by the secondary current loop in the three-phase standard current transformer and the secondary current loop in the tested distribution network transformer, and determines the current detection result of the first phase to be measured of the tested distribution network transformer.

[0058] The current verification module includes a first switching circuit, a single-phase digital current calibrator and a first host computer, and the single-phase digital current calibrator and the first host computer are 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 tested distribution network transformer according to the current detection instruction input by the user, adopts a time-division multiplexing method, and obtains the current detection results of each phase of the tested distribution network transformer, thereby improving the flexibility and pertinence of the detection.

[0060] It should be noted that the current detection instruction may include the phase that needs to be detected this time, and may also include the detection order of the three phases, so that according to the instructions of the current detection instruction, the secondary current of the same phase is input into the single-phase digital current calibrator through the first linkage switch switching circuit to obtain the current detection results of each phase of the distribution network transformer under test.

[0061] Specifically, the first host computer determines the target terminals connected to the first phase to be measured, i.e., the target first terminal, the target second terminal, the target third terminal and the target fourth terminal, in the first switching circuit according to the first phase to be measured indicated by the current detection instruction, thereby switching the circuit according to the target terminals so that the secondary current of the first phase to be measured output by the tested distribution network transformer and the three-phase standard current transformer are simultaneously input into the single-phase digital current calibrator.

[0062] Exemplarily, the first host computer controls the closing of 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 short-circuit the secondary current loop of the non-detection phase in the three-phase standard current transformer to ensure the safety of detection.

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

[0064] Furthermore, 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 be disconnected, and controls the first linkage switch in the first switching circuit to connect the target first terminal and the target third terminal, so that the secondary current of the first phase to be measured output by the distribution network transformer under test and the three-phase standard current transformer is simultaneously input into the single-phase digital current calibrator through the first switching circuit, so that the single-phase digital current calibrator calculates the measurement error of the first phase to be measured of the distribution network transformer under test according to the secondary current of the first phase to be measured output by the three-phase standard current transformer and the distribution network transformer under test, and then determines the current detection result of the first phase to be measured of the distribution network transformer under test.

[0065] For example, Figure 3 and Figure 4As shown, if the current detection instruction indicates to detect phase A, phase B, and phase C in sequence, phase A is first used as the first phase to be tested. At this time, the first terminal I connected to phase A a0 , the second terminal I an0 、Third terminal I ax 、The fourth terminal I anx Then, 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 Close, and control the first terminal I a0 and the second terminal I an0 The first switch J between a0 The first host computer 306 controls the first linkage switch J to short-circuit the three-phase standard current transformer 102 and the B-phase and C-phase secondary current loops in the tested distribution network transformer 101. I At the same time, connect the first terminal I a0 With the third terminal I ax .

[0066] After the circuit switching is completed, the three-phase high current provided by the three-phase high-voltage power source 206 is simultaneously added to the three-phase standard current transformer 102 and the distribution network transformer 101 under test, so that the A-phase secondary current output by the three-phase standard current transformer 102 and the distribution network transformer 101 under test is simultaneously input to the single-phase digital current tester 305, thereby determining the current detection result of the A-phase of the distribution network transformer 101 under test through the single-phase digital current tester 305. By analogy, the first host computer 306 controls the first switch, the second switch and the first linkage switch J I The switching circuit is used to input the B-phase and C-phase secondary currents output by the three-phase standard current transformer 102 and the distribution network transformer 101 under test into the single-phase digital current calibrator 305 in sequence, thereby determining the current detection results of the B-phase and C-phase of the distribution network transformer 101 under test in sequence through the single-phase digital current calibrator 305.

[0067] Further, as a refinement and expansion of the specific implementation methods of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, the step of determining the current detection result of the first phase to be measured of the distribution network transformer under test specifically includes: converting the secondary current of the first phase to be measured outputted by the secondary current loop in the three-phase standard current transformer and the secondary current loop in the distribution network transformer under test into a first digital signal and a second digital signal respectively; using a mean square root algorithm to determine a first amplitude of the first digital signal and a second amplitude of the second digital signal; performing spectral analysis on the first digital signal and the second digital signal, and using a discrete Fourier change algorithm to determine first phase information of the first digital signal and second phase information of the first digital signal respectively; determining a ratio difference based on the first amplitude and the second amplitude; determining a 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 distribution network transformer under test based on the ratio difference and the phase difference.

[0068] In an 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, and the performance of the tested distribution network transformer is more accurately evaluated to identify slight error changes.

[0069] Exemplarily, the secondary current of the first phase to be measured output by the three-phase standard current transformer and the distribution network transformer under test is converted into a first digital signal and a second digital signal respectively through an analog-to-digital converter (ADC) to represent the secondary current signal as a series of discrete digital values ​​for facilitating 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 value (RMS). For example, the first digital signal within a sampling time can be squared and then averaged and squared to obtain the first amplitude. Similarly, the second digital signal of the distribution network transformer under test is processed in the same way to obtain the second amplitude.

[0071] At the same time, for the first data signal and the second digital signal, a discrete Fourier transform (DFT) algorithm or other efficient spectrum analysis algorithm can be used to analyze the spectrum information of the secondary current, so as to quickly and accurately calculate the phases of the two secondary currents and obtain the first phase information of the first digital signal and the second phase information of the first digital signal.

[0072] Furthermore, according to the difference between the second amplitude and the first amplitude and the ratio of the first amplitude, the ratio difference is determined to reflect the difference in amplitude between the three-phase standard current transformer and the distribution network transformer under test. At the same time, according to the difference between the first phase information and the second phase information, the phase difference is determined to reflect the difference in phase angle between the three-phase standard current transformer and the distribution network transformer under test. Then, according to the ratio difference and the phase difference, the current detection result of the first phase to be measured of the distribution network transformer under test is determined, so as to accurately calculate the error of the distribution network transformer under test by using the digital comparison method.

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

[0074] In this embodiment, it is detected whether the accuracy levels of the tested distribution network transformer and the three-phase standard current transformer match each other, ensuring that the three-phase standard current transformer and the tested distribution network transformer have a reasonable matching degree in terms of accuracy level, so as to prevent inaccurate detection results due to mismatch in accuracy levels between the two, and fail to truly reflect the performance of the tested transformer, thereby improving the reliability and accuracy of the detection.

[0075] Exemplarily, a high-definition camera can be used to photograph the nameplate of the distribution network transformer under test, and the text information on the nameplate, including the accuracy level, can be automatically identified by an image recognition algorithm. For example, optical character recognition (OCR) technology can be used to convert the photographed nameplate image into editable text, and then the accuracy level information can be extracted from it. High-precision measuring equipment can also be connected to monitor and analyze the output signal of the distribution network transformer under test in real time. Transformers with different accuracy levels will have certain differences in the stability and accuracy of the output signal. By analyzing the characteristics of the output signal, such as fluctuation range, noise level, linearity, etc., the accuracy level of the distribution network transformer under test can be determined.

[0076] Furthermore, if the difference between the preset accuracy level of the three-phase standard current transformer and the identified accuracy level of the tested distribution network transformer does not meet the preset conditions, the first linkage switch is controlled to be disconnected, and the first switch and the second switch are controlled to be closed to disconnect the connection between the three-phase standard current transformer and the tested distribution network transformer and the single-phase digital current tester, thereby ensuring the safety of detection, avoiding false detection, and improving the reliability and accuracy of detection. At the same time, abnormal information is determined, such as the mismatch of accuracy level, and abnormal information is displayed to prompt the staff to further check.

[0077] Among them, the preset condition can be set according to the detection requirements of the digital comparison method, and the accuracy level 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 ratio of 600A / 5A and an accuracy level of 0.02S can be used to cover distribution network transformers of various ratios in the field. In addition, the measurement range of the three-phase standard current transformer is selected according to the maximum current requirement of the three-phase standard current transformer on site. Similarly, more than 95% of the distribution network transformers are at a voltage level of 10kV. In order to meet the needs of on-site detection, the voltage level of the standard voltage transformer is 10kV and the accuracy level is 0.05.

[0078] Step 702: The voltage verification module responds to the voltage detection instruction and determines the voltage detection result of the distribution network transformer under test according to the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test.

[0079] In this embodiment, similar to the current verification module, after the detection device is moved to the use site of the distribution network transformer under test and connected to the distribution network transformer under test, the user inputs a voltage detection instruction in the voltage verification module according to the detection requirements. Based on the voltage detection instruction, the voltage verification module obtains the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test, and calculates the error of the measured voltage of the distribution network transformer under test, thereby avoiding tedious manual operations, improving the voltage detection efficiency, and enhancing its automation level.

[0080] Further, as a refinement and extension of the specific implementation methods of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, step 702, that is, the voltage verification module responds to the voltage detection instruction, and determines the voltage detection result of the distribution network transformer under test according to the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test, including: the second host computer determines the target fifth terminal and the target sixth terminal connected to the second phase to be tested in the second switching circuit according to the second phase to be tested indicated by the voltage detection instruction; 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 to be tested output by the secondary voltage circuit in the three-phase standard voltage transformer and the secondary voltage circuit in the distribution network transformer under test, and determines the voltage detection result of the second phase to be tested of the distribution network transformer under test.

[0081] The voltage verification module includes a second switching circuit, a single-phase digital voltage calibrator and a second host computer, and 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 also uses a time-division multiplexing method to detect the secondary voltage of each phase of the distribution network transformer under test according to the voltage detection instruction input by the user, and obtains the voltage detection results of each phase of the distribution network transformer under test, thereby improving the efficiency and flexibility of detection.

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

[0084] For example, Figure 3 and Figure 5 As shown, if the voltage detection instruction indicates to detect phase A, phase B, and phase C in sequence, phase A is first used as the first phase to be tested. At this time, the fifth terminal U connected to phase A is a0 With the sixth terminal U ax The second host computer 303 controls the second linkage switch J U At the same time, connect the fifth terminal U a0 With the sixth terminal U ax Then, the three-phase high current provided by the three-phase high-voltage power source 206 is simultaneously added to the three-phase standard voltage transformer 103 and the distribution network transformer 101 under test, so that the A-phase secondary voltage output by the three-phase standard voltage transformer 103 and the distribution network transformer 101 under test is simultaneously input to the single-phase digital voltage tester 302, thereby determining the voltage detection result of the A-phase of the distribution network transformer 101 under test through the single-phase digital voltage tester 302. By analogy, the second linkage switch J is controlled by the second host computer 303. U The switching circuit is used to input the B-phase and C-phase secondary voltages output by the three-phase standard voltage transformer 103 and the tested distribution network transformer 101 into the single-phase digital voltage calibrator 302 in sequence, thereby determining the voltage detection results of the B-phase and C-phase of the tested distribution network transformer 101 in sequence 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 distribution network transformer under test is a combined transformer, after the circuit is switched by the first switch, the second switch, the first linkage switch and the second linkage switch, the three-phase high voltage and large current provided by the three-phase high-voltage power source are simultaneously added to the three-phase standard voltage, current transformer and the distribution network transformer under test, simulating the actual operating conditions of the distribution network transformer under test, so as to simultaneously detect the error in measuring current and the error in measuring voltage of the distribution network transformer under test.

[0087] In one embodiment, the on-site detection method of the distribution network transformer also includes: if the current detection result or the voltage detection result does not meet the preset error range, it is determined that the distribution network transformer under test is unqualified, and based on the current detection result or the voltage detection result that does not meet the budgeted 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 eligibility of the tested distribution network transformer, reducing the error and time cost of manual judgment. At the same time, clear early warning information can enable operators to take quick action and improve work efficiency.

[0089] Exemplarily, the allowable error range can be pre-set according to the standard specifications, accuracy requirements and relevant industry specifications of the transformer. If the current detection result or the voltage detection result is within the preset error range, it is determined that the tested distribution network transformer is qualified. If it is not within the preset error range, it is determined that the tested distribution network transformer is unqualified. According to the current detection result or the voltage detection result that does not meet the preset error range, the early warning information is determined. The early warning information may include specific unqualified parameters (such as current values ​​or voltage values ​​that exceed the error range), unqualified types (whether the current is unqualified or the voltage is unqualified) and possible problem prompts (such as possible causes of failure, etc.). The determined early warning information is displayed through a display screen, indicator light, sound, etc., so that the operator can promptly understand the detection status and problems of the tested distribution network transformer.

[0090] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. Those skilled in the art will appreciate that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be changed accordingly and located in one or more devices different from the present implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple submodules.

[0091] The above serial numbers of this application are only for description and do not represent the advantages and disadvantages of the implementation scenarios. The above disclosure is only a few specific implementation scenarios of this application, but this application is not limited to them, and any changes that can be thought of by technicians in this field should fall within the scope of protection of this application.

Claims

1. A field detection device for a distribution network mutual inductor, characterized in that: The device is connected to the transformer of the distribution network to be tested, and the device comprises: 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 in the three-phase standard current transformer is connected in series with the primary current loop in the tested distribution network transformer; The primary voltage circuit in the three-phase standard voltage transformer and the primary voltage circuit in the tested distribution network transformer are connected in parallel; The secondary current loop in the three-phase standard current transformer and the secondary current loop in the tested distribution network transformer are respectively connected to the current verification module, and the current verification module is used to receive the secondary current output by the three-phase standard current transformer and the tested distribution network transformer, and determine the current detection result of the tested distribution network transformer; The secondary voltage circuit in the three-phase standard voltage transformer and the secondary voltage circuit in the distribution network transformer under test are respectively connected to the voltage verification module, and the voltage verification module is used to receive the secondary voltages output by the three-phase standard voltage transformer and the distribution network transformer under test, and determine the voltage detection result of the distribution network transformer under test.

2. The field detection device for transformer in the power distribution network according to claim 1, 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 A-phase, B-phase and C-phase output ends of the secondary current loop in the three-phase standard current transformer are respectively connected to the first terminal in the first switching circuit; The A-phase, B-phase and C-phase input terminals of the secondary current loop 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 connected with the same phase; The A-phase, B-phase and C-phase output terminals of the secondary current loop in the tested distribution network transformer 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 loop in the tested distribution network transformer 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 connected with the same phase; The first linkage switch in the first switching circuit is connected to the first terminal and the third terminal connected to 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.

3. The field detection device for transformer in the power distribution network according to claim 1, 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 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 tested distribution network transformer are respectively connected to the sixth terminal in the second switching circuit; The single-phase digital voltage tester receives the reference voltage output by the secondary voltage circuit in the three-phase standard voltage transformer and the secondary voltage circuit in the tested distribution network transformer through the second switching circuit; The second linkage switch in the second switching circuit is connected to the fifth terminal and the sixth terminal connected to the same phase; The second host computer is used to control the opening and closing of the second linkage switch.

4. The field detection device for transformer in the power distribution network according to claim 1, characterized in that: The device also 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 measured distribution network transformer; the three-phase current load box is connected to the secondary current circuit of the measured distribution network transformer.

5. A method for on-site detection of a transformer in a distribution network, applied to the on-site detection device for a transformer in a distribution network as claimed in any one of claims 1 to 4, characterized in that: The method comprises: The current verification module responds to the current detection instruction and determines the current detection result of the distribution network transformer under test according to the secondary current output by the three-phase standard current transformer and the distribution network transformer under test; The voltage verification module responds to the voltage detection instruction and determines the voltage detection result of the distribution network transformer under test according to the secondary voltage output by the three-phase standard voltage transformer and the distribution network transformer under test.

6. The on-site detection method for transformers in distribution network according to claim 5, 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 the current detection instruction, and determines the current detection result of the tested distribution network transformer according to the secondary current output by the three-phase standard current transformer and the tested distribution network transformer, including: The first host computer determines, in the first switching circuit, a target first terminal, a target second terminal, a target third terminal, and a target fourth terminal connected to the first phase to be measured according to the first phase to be measured indicated by the current detection instruction; 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 as to short-circuit the secondary current loop excluding the first phase to be measured in the three-phase standard current transformer; The first host computer controls the second switch between the third terminal excluding the target third terminal and the fourth terminal excluding the target fourth terminal in the first switching circuit to close, so as to short-circuit the secondary current loop of the tested distribution network transformer excluding the first phase to be tested; 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, so as to connect the first target terminal and the third target terminal; The single-phase digital current tester receives the secondary current of the first phase to be measured output by the three-phase standard current transformer and the tested distribution network transformer, and determines the current detection result of the first phase to be measured of the tested distribution network transformer.

7. The method for on-site detection of a transformer in a power distribution network according to claim 6, characterized in that: The step of determining a current detection result of a first phase to be measured of the tested distribution network transformer comprises: Converting the secondary current of the first phase to be measured output by the three-phase standard current transformer and the measured distribution network transformer into a first digital signal and a second digital signal respectively; Determine a first amplitude of the first digital signal and a second amplitude of the second digital signal by using a mean square root algorithm; Performing spectrum analysis on the first digital signal and the second digital signal, and using a discrete Fourier transform algorithm to respectively determine first phase information of the first digital signal and second phase information of the first digital signal; determining a ratio difference according to the first amplitude and the second amplitude; Determining a phase difference according to the first phase information and the second phase information; According to the ratio difference and the phase difference, a current detection result of a first phase to be measured of the tested distribution network transformer is determined.

8. The method for on-site detection of a transformer in a power distribution network according to claim 6, characterized in that: The method further comprises: Identifying the accuracy level of the tested distribution network transformer; If the difference between the preset accuracy level of the three-phase standard current transformer and the accuracy level of the tested distribution network transformer does not meet the preset condition, the first linkage switch is controlled to be opened, and the first switch and the second switch are controlled to be closed, and abnormal information is determined; The exception information is displayed.

9. The method for on-site detection of transformers in a power distribution network according to claim 5, 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 the voltage detection instruction, and determines the voltage detection result of the tested distribution network transformer according to the secondary voltage output by the three-phase standard voltage transformer and the tested distribution network transformer, including: The second host computer determines, in the second switching circuit, a target fifth terminal and a target sixth terminal connected to the second phase to be measured according to the second phase to be measured indicated by the voltage detection instruction; 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 tester receives the secondary voltage of the second phase to be measured output by the three-phase standard voltage transformer and the tested distribution network transformer, and determines the voltage detection result of the second phase to be measured of the tested distribution network transformer.

10. The on-site detection method for transformers in a power distribution network according to claim 5, characterized in that: The method further comprises: If the current detection result or the voltage detection result does not meet the preset error range, it is determined that the distribution network transformer under test is unqualified, and according to the current detection result or the voltage detection result that does not meet the budgeted error range, early warning information is determined; The warning information is displayed.

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