Wide-range current transformer field calibration system and self-checking method thereof

Abstract

A wide-range current transformer field calibration system and a self-checking method thereof, the field calibration system comprising a self-checking circuit and a CPU, the self-checking circuit comprising n groups of tap switches of a primary winding and n groups of tap switches of a secondary winding; a voltage input of a voltage regulating power supply is zero, the CPU controls the n groups of tap switches of the primary winding and the n groups of tap switches of the secondary winding to be closed or opened, a transformation ratio of a standard voltage transformer is consistent with a calibration transformation ratio of a tested current transformer; the CPU controls the voltage regulating power supply to make a current output by a current riser rise to 10% of a rated current of the standard current transformer, and performs self-checking on the field calibration system, if a current percentage value output by an error calibration device rises with a voltage rise of the voltage regulating power supply, and a display value is 0.1%, 1%, 5% or 10%, the self-checking is qualified; otherwise, the self-checking is unqualified. The present application solves problems of many field calibration test devices, complex wiring and difficult guarantee of accuracy.

Description

Technical Field

[0001] This invention belongs to the field of current transformer verification technology, specifically, it relates to a wide-range current transformer field verification system and its self-testing method. Background Technology

[0002] The JJG1021 "Verification Procedure for Power Transformers" requires that power transformers be verified on-site at substations and other locations. This necessitates transporting the current transformer field verification system to the site for testing.

[0003] A typical field calibration system for current transformers includes a voltage regulating power supply, a current boosting power supply, a compensation device, a standard current transformer, a load box, and a calibration instrument. The design involves numerous testing devices and complex wiring. With advancements in power and mechanical technologies, to improve the convenience of field testing of current transformers and reduce manpower and material costs, field calibration systems for current transformers have gradually moved towards integration in recent years. During transportation / testing, all components of the field calibration system are already internally fixed and connected.

[0004] Substations, especially those above 220kV, are often located in remote areas. Long-distance transportation and bumpy rides can cause loosening of internal wiring or damage to components in integrated current transformer testing equipment. In particular, an open circuit in the winding of a standard current transformer is not dangerous; a momentary overcurrent could damage the test system, even the test object, and pose a safety threat to the test personnel.

[0005] Existing technologies such as "A bus-type current transformer with self-calibration function" (CN216015049U) and "A current transformer with condition diagnosis function" (CN209785728U) propose configuring a self-calibration winding on the secondary winding side, and then verifying the current transformer under test according to the condition diagnosis method required by the regulations, so as to achieve the purpose of rapid on-site verification in conjunction with the transformer calibration device. However, configuring a secondary winding or condition diagnosis unit on the tested object requires changing the structure of the tested object, resulting in low adaptability. "A current transformer with condition diagnosis function" (CN205910331U) implements transformer condition diagnosis through a condition diagnosis switch control circuit. Essentially, it integrates the current transformer calibration device with a common single-ratio current transformer to form a new current transformer with condition diagnosis function, and puts them into operation together. When condition diagnosis is needed, the condition diagnosis of the common single-ratio current transformer is implemented through the condition diagnosis switch control circuit. Existing technologies such as the automatic calibration device and method for high current transformers (CN105929354A) and a programmable fully automatic wiring device for current transformers (CN107271944B) can perform fully automatic wiring and calibration of the tested transformers. However, none of them mention how to perform error verification on the tested voltage transformer using the transformer calibration equipment on site, or how to perform status diagnosis of the transformer calibration equipment. In particular, when the standard voltage transformer in the calibration system has a disconnected primary or secondary winding, loose wiring, or reversed polarity, it is impossible to detect the fault state of the system through self-calibration, which leads to incorrect on-site calibration results of the transformers and greatly reduces the reliability of the calibration results. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a wide-range current transformer field verification system and its self-testing method. This system enables self-testing of the field verification system before field verification of wide-range current transformers, thus solving the problems of numerous testing devices, complex wiring, and difficulty in ensuring accuracy in existing wide-range current transformer field verification technologies.

[0007] The present invention adopts the following technical solution.

[0008] This invention proposes a wide-range current transformer field calibration system, which includes: a voltage regulating power supply, a current booster, a standard current transformer, an error calibration device, a current transformer under test, and a load box; wherein, the voltage regulating power supply is connected to the standard current transformer through the current booster, and the standard current transformer is connected to the current transformer under test and then to the load box.

[0009] The field verification system also includes: a self-test circuit and an error verification device;

[0010] The first and last ends of the primary winding of a standard current transformer are L1 and LN, respectively, and multiple primary winding taps are provided between the first and last ends of the primary winding. The first and last ends of the secondary winding are S1 and Sn, respectively, and multiple secondary winding taps are provided between the first and last ends of the secondary winding.

[0011] The end of the primary winding of the standard current transformer is connected to the beginning of the primary winding of the current transformer under test. The beginning of the primary winding of the standard current transformer and the end of the primary winding of the current transformer under test are connected to the beginning and end of the secondary winding of the current booster. The end of the secondary winding of the standard current transformer is connected to the beginning of the secondary winding of the current transformer under test.

[0012] The error verification device includes a first measuring terminal T0 connected to the beginning of the secondary winding of a standard current transformer, a second measuring terminal K connected to the end of the secondary winding of the standard current transformer and the beginning of the secondary winding of the current transformer under test, and a third measuring terminal Tx connected to the end of the secondary winding of the current transformer under test through a load box.

[0013] The self-test circuit includes a primary tap switch group connected to the taps of each primary winding of the standard current transformer, and a secondary tap switch group connected to the taps of each secondary winding of the standard current transformer. By switching the primary tap switch group and the secondary tap switch group on and off, various transformation ratios of the standard current transformer can be realized.

[0014] n-1 taps are set between the beginning and end of the primary winding of a standard current transformer, and n-2 taps are set between the beginning and end of the secondary winding of a standard current transformer.

[0015] The primary tap switch group includes n primary tap switches. The first primary tap switch is connected in parallel between the end LN of the primary winding of the standard current transformer and the end of the output winding of the current booster. The second to nth primary tap switches are connected between the n-1 primary winding taps of the primary winding of the standard current transformer and the end LN of the primary winding.

[0016] The secondary tap switch group includes n secondary tap switches. One end of the second to nth secondary tap switches is connected to the first to n-2th taps of the secondary winding of the standard current transformer and the end of the secondary winding, respectively. The other ends of the second to nth secondary tap switches are connected together and then connected to the third measuring terminal Tx of the error verification device through the first secondary tap switch.

[0017] The field verification system also includes a measurement and control module. The output control terminal of the measurement and control module is connected to the control terminal of the voltage regulating power supply, the control terminal of the primary tap switch group and the control terminal of the secondary tap switch group. The output current boost signal controls the output voltage of the voltage regulating power supply, and the output standard transformer primary winding tap control signal and secondary winding tap control signal control the switching of each primary tap switch and secondary tap switch to realize multiple transformation ratios of the standard current transformer.

[0018] The input terminal of the measurement and control module receives the dial indicator signal and differential current signal output from the error verification device.

[0019] When the current input to the standard current transformer from the current booster is zero, the closing or opening of n primary tap switches and n secondary tap switches is controlled to make the transformation ratio of the standard voltage transformer consistent with the calibration transformation ratio of the current transformer under test. Then, the voltage regulator is controlled to increase the voltage rise and fall so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer. If the percentage value of the current output by the error verification device increases with the voltage of the voltage regulator and the displayed value meets the accuracy indication value and the standard indication value specified in the procedure, then the self-test of the field verification system is deemed qualified; otherwise, the self-test of the field verification system is deemed unqualified.

[0020] The accuracy value is 0.1%; the standard values ​​specified in the regulations include 1%, 5%, and 10%.

[0021] If the self-test fails, and the voltage of the adjustable power supply increases but the current percentage value output by the error verification device does not change, then the power supply is determined to be faulty, or the primary or secondary winding of the standard current transformer is disconnected.

[0022] If the self-test fails and the current percentage value output by the error verification device increases non-linearly with the increase of the voltage of the voltage regulating power supply, it is determined that the primary or secondary winding of the standard current transformer is not securely connected.

[0023] If the self-test fails and the error verification device displays a polarity error, the output current percentage value will increase non-linearly as the voltage of the voltage regulator increases, which indicates that the polarity terminals of the primary and secondary windings of the standard current transformer are reversed.

[0024] The n-group tap switches of the primary winding are three-phase contactors, and the operating current is 1 / 3 of the primary rated current.

[0025] The nth tap switch of the secondary winding is a relay with an operating current of 10A.

[0026] In another aspect, this invention also proposes a self-testing method for a wide-range current transformer field calibration system, comprising:

[0027] Step 1: The voltage input to the standard current transformer from the regulated power supply is zero;

[0028] Step 2: Use the verification ratio of the tested current transformer as the ratio of the standard voltage transformer;

[0029] Step 3: According to the transformation ratio of the standard voltage transformer, control the first primary tap switch to close, and control any tap switch from the second primary tap switch to the nth primary tap switch to close, and connect the corresponding primary winding tap terminal to the current booster.

[0030] Step 4: According to the transformation ratio of the standard voltage transformer, control the first secondary tap switch to close, and control any tap switch from the second secondary tap switch to the nth secondary tap switch to close, so that the corresponding secondary winding tap end and tail end are connected to the current booster.

[0031] Step 5: Control the voltage rise and fall of the voltage regulator so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer.

[0032] Step 6: Perform a self-test on the field verification system. If the current percentage value output by the error verification device increases with the voltage of the voltage regulator and the displayed value is 0.1%, 1%, 5%, or 10%, then the self-test is qualified; otherwise, the self-test is deemed unqualified.

[0033] Preferably, in step 1, when the first tap switch is closed and any one of the tap switches from the second tap switch to the nth tap switch is closed, the remaining tap switches are all open.

[0034] Preferably, in step 2, when the first tap switch is closed, and when any one of the tap switches from the second tap switch to the nth tap switch is closed, the remaining tap switches are all open.

[0035] Preferably, the method further includes:

[0036] Step 7: If the self-test fails, control the voltage input of the voltage regulator to the standard current transformer to return to zero, stop the self-test, and then repair the on-site calibration system.

[0037] The beneficial effects of this invention are that, compared with the prior art, the field verification system and its self-testing method proposed in this invention can easily and quickly determine whether the wide-range current transformer and the verification system can work normally and whether there is a fault. It can greatly improve the safety and accuracy of field testing of wide-range current transformers; it can complete the field verification of current transformers with different ratios, and the wiring is simple, convenient and quick, with a wide range of applications. Attached Figure Description

[0038] Figure 1This is a structural diagram of a wide-range current transformer field verification system proposed in this invention;

[0039] Figure 2 This is a circuit diagram of a wide-range current transformer field verification system proposed in this invention.

[0040] Figure 1 and 2 The annotations in the accompanying drawings are explained as follows:

[0041] 1-Voltage regulating power supply, 2-Current booster, CT0-Standard current transformer, CTx-Current transformer under test, 3-Error verification device, 4-Load box, 5-Self-test circuit;

[0042] P1, P2 - the two ends of the current booster output winding, L1 - the start end of the primary winding of the standard current transformer, LN - the end of the primary winding of the standard current transformer, S1 - the start end of the secondary winding of the standard current transformer, SN - the end of the secondary winding of the standard current transformer.

[0043] Figure 3 This is a schematic diagram of the self-test circuit in a wide-range current transformer field calibration system proposed in this invention.

[0044] Figure 4 This is a circuit diagram of a self-test circuit in a wide-range current transformer field calibration system proposed in this invention.

[0045] Figure 4 The annotations in the accompanying drawings are explained as follows:

[0046] K L1 K L2 K L3 K L4 ...K Ln -n sets of tap switches for the primary winding, K S1 K S2 K S3 K S4 ...K Sn - n sets of tap switches for the secondary winding

[0047] L2, L3, L4, ..., Ln - the first tap, second tap, third tap, ..., n-1 tap of the primary winding of a standard current transformer;

[0048] S2, S3, S4, ..., Sn-1 - the first tap, second tap, third tap, ..., n-2 taps of the primary winding of a standard current transformer;

[0049] Ip - Current percentage value;

[0050] Figure 5This is a flowchart of the self-test of the wide-range current transformer field calibration system in an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0052] This invention proposes a wide-range current transformer field verification system, such as... Figure 1 and 2 As shown, the system includes: a voltage regulating power supply 1, a current booster 2, a standard current transformer CT0, an error verification device 3, a current transformer under test CTx, and a load box 4; wherein, the voltage regulating power supply is connected to the standard current transformer through the current booster, and the standard current transformer is connected to the current transformer under test and then connected to the load box.

[0053] The current booster includes: an input winding and an output winding; the two ends of the output winding are P1 and P2 respectively; the voltage regulating power supply is connected to the input winding; the output windings P1-P2 are connected in series with the primary windings L1-LN of the standard current transformer; the secondary windings S1-SN of the standard current transformer are connected to the error verification device; the primary winding of the current transformer under test is connected in series with the primary winding of the standard current transformer; and the secondary winding of the current transformer under test is connected in series with the secondary winding of the standard current transformer.

[0054] The on-site verification system includes: self-test circuit 5 and error verification device;

[0055] The first and last ends of the primary winding of a standard current transformer are L1 and LN, respectively, and multiple primary winding taps are provided between the first and last ends of the primary winding. The first and last ends of the secondary winding are S1 and Sn, respectively, and multiple secondary winding taps are provided between the first and last ends of the secondary winding.

[0056] The end of the primary winding of the standard current transformer is connected to the beginning of the primary winding of the current transformer under test. The beginning of the primary winding of the standard current transformer and the end of the primary winding of the current transformer under test are connected to the beginning and end of the secondary winding of the current booster. The end of the secondary winding of the standard current transformer is connected to the beginning of the secondary winding of the current transformer under test.

[0057] The error verification device includes a first measuring terminal T0 connected to the beginning of the secondary winding of a standard current transformer, a second measuring terminal K connected to the end of the secondary winding of the standard current transformer and the beginning of the secondary winding of the current transformer under test, and a third measuring terminal T connected to the end of the secondary winding of the current transformer under test via a load box.x During error verification, the first measuring terminal T0 and the third measuring terminal T... x The working current loop is formed by the second measuring terminal K and the third measuring terminal T. x This forms a differential current loop.

[0058] The self-test circuit includes a primary tap switch group connected to the taps of each primary winding of the standard current transformer, and a secondary tap switch group connected to the taps of each secondary winding of the standard current transformer. By switching the primary tap switch group and the secondary tap switch group on and off, various transformation ratios of the standard current transformer can be realized.

[0059] n-1 taps are set between the beginning and end of the primary winding of a standard current transformer, and n-2 taps are set between the beginning and end of the secondary winding of a standard current transformer.

[0060] like Figure 4 As shown, a single-tap switch group includes n single-tap switches K L1 K L2 K L3 K L4 ...K Ln The first primary tap switch is connected in parallel between the end LN of the primary winding of the standard current transformer and the end of the output winding of the current booster; the second to the nth primary tap switches are connected between the n-1 primary winding taps of the primary winding of the standard current transformer and the end LN of the primary winding.

[0061] like Figure 4 As shown, the secondary tap switch group includes n secondary tap switches K S1 K S2 K S3 K S4 ...K Sn One end of the second to nth tap switches is connected to the first to n-2th taps and the end of the secondary winding of the standard current transformer, respectively. The other ends of the second to nth tap switches are connected together and then connected to the third measuring terminal T of the error verification device through the first tap switch. x .

[0062] Figure 4 In the middle, the test current transformer is also connected in parallel to the right side of the first tap switch, and at the same time, the two ends P1 and P2 of the current booster output winding are connected in series.

[0063] The voltage regulator is connected to the input winding of the current booster, and the two ends of the output winding of the current booster are connected to the series branch of the primary winding of the standard current transformer and the primary winding of the current transformer under test.

[0064] The field verification system also includes a measurement and control module. The output control terminal of the measurement and control module is connected to the control terminal of the voltage regulating power supply, the control terminal of the primary tap switch group and the control terminal of the secondary tap switch group. The output current boost signal controls the output voltage of the voltage regulating power supply, and the output standard transformer primary winding tap control signal and secondary winding tap control signal control the switching of each primary tap switch and secondary tap switch to realize multiple transformation ratios of the standard current transformer.

[0065] The input terminal of the measurement and control module receives the dial indicator signal and differential current signal output from the error verification device.

[0066] In the error verification device, the primary current of the current transformer under test is calculated based on the secondary current of the current transformer under test and the turns ratio of the standard current transformer. The ratio of the primary current to the rated primary current of the current transformer under test is used as the dial indicator signal, and the difference between the rated secondary current of the standard current transformer and the secondary current of the current transformer under test is used as the differential current signal.

[0067] The input terminal of the measurement and control module receives the dial indicator signal and differential current signal output by the error verification device. Based on the dial indicator signal, it verifies that the primary current of the current transformer under test is within the range of not less than 0.1% and not more than 200% as specified in the regulations. The ratio of the differential current signal to the rated secondary current of the standard current transformer is used as the measurement error of the current transformer under test.

[0068] When the current input to the standard current transformer from the current booster is zero, the closing or opening of n primary tap switches and n secondary tap switches is controlled to make the transformation ratio of the standard voltage transformer consistent with the calibration transformation ratio of the current transformer under test. Then, the voltage regulator is controlled to increase the voltage rise and fall so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer. If the percentage value of the current output by the error verification device increases with the voltage of the voltage regulator and the displayed value meets the accuracy indication value and the standard indication value specified in the procedure, then the self-test of the field verification system is deemed qualified; otherwise, the self-test of the field verification system is deemed unqualified.

[0069] The current percentage value output by the error verification device is the ratio of the secondary current to the rated current of a standard current transformer.

[0070] The accuracy value is 0.1%; the standard values ​​specified in the regulations include 1%, 5%, and 10%.

[0071] The accuracy value is set at 0.1% to meet the testing requirements of wide-range current transformers.

[0072] It is worth noting that the current percentage value displayed by the error verification device used in this embodiment of the invention is a non-limiting preferred choice. Those skilled in the art can choose different current percentage values ​​according to accuracy requirements and specifications.

[0073] like Figure 3 As shown, the CPU outputs control signals for the starting end L1, first tap L2, second tap L3, third tap L4, ..., n-1th tap Ln of the primary winding, and also outputs control signals for the starting end S1, first tap S2, second tap S3, third tap S4, ..., n-2th tap Sn-1 of the secondary winding; the CPU inputs boost current signal and voltage regulation signal to the voltage regulating device; the CPU reads dial indicator signal and differential current signal from the error verification device.

[0074] In this embodiment of the invention, the wide-range current transformer field calibration system is brought to the field after being debugged in the laboratory. Before operation, the system needs to undergo self-testing. Based on operational experience in engineering fields, problems often arise due to external factors such as transportation and actual site conditions, which can significantly reduce the accuracy and precision of on-site work. Therefore, self-testing of the system is proposed. The objects of self-testing are the wiring and electrical circuits of the standard current transformers and voltage regulating power supplies that make up the system. The self-testing criteria and conclusions derived from operational experience are as follows:

[0075] (1) If the voltage of the voltage regulator increases but the current percentage value output by the error verification device does not change when the self-test fails, it is determined that the power supply is faulty or the primary winding or secondary winding of the standard current transformer is disconnected.

[0076] (2) If the current percentage value output by the error verification device increases non-linearly with the voltage of the voltage regulating power supply when the self-inspection fails, it is determined that the primary winding or secondary winding of the standard current transformer is not securely connected.

[0077] (3) If the self-test fails, and the error verification device displays a polarity error, the output current percentage value will increase non-linearly as the voltage of the voltage regulator increases, which means that the polarity terminals of the primary and secondary windings of the standard current transformer are reversed.

[0078] The n-group tap switches of the primary winding are three-phase contactors, and the operating current is 1 / 3 of the primary rated current.

[0079] The nth tap switch of the secondary winding is a relay with an operating current of 10A.

[0080] It is worth noting that the selection of each tap switch and the operating current in the embodiments of the present invention are non-limiting preferred choices, and those skilled in the art can make different equipment selections and parameter selections according to engineering requirements.

[0081] In another aspect, this invention also proposes a self-testing method for a wide-range current transformer field calibration system, comprising:

[0082] Step 1: The voltage input to the standard current transformer from the regulated power supply is zero;

[0083] Step 2: Use the verification ratio of the tested current transformer as the ratio of the standard voltage transformer;

[0084] Step 3: According to the transformation ratio of the standard voltage transformer, control the first primary tap switch to close, and control any tap switch from the second primary tap switch to the nth primary tap switch to close, and connect the corresponding primary winding tap terminal to the current booster.

[0085] Step 4: According to the transformation ratio of the standard voltage transformer, control the first secondary tap switch to close, and control any tap switch from the second secondary tap switch to the nth secondary tap switch to close, so that the corresponding secondary winding tap end and tail end are connected to the current booster.

[0086] Step 5: Control the voltage rise and fall of the voltage regulator so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer.

[0087] Step 6: Perform a self-test on the field verification system. If the current percentage value output by the error verification device increases with the voltage of the voltage regulator and the displayed value is 0.1%, 1%, 5%, or 10%, then the self-test is qualified; otherwise, the self-test is deemed unqualified.

[0088] Preferably, when the first tap switch is closed, and any one of the tap switches from the second tap switch to the nth tap switch is closed, all other tap switches are open.

[0089] Preferably, in step 2, when the first tap switch is closed, and when any one of the tap switches from the second tap switch to the nth tap switch is closed, the remaining tap switches are all open.

[0090] Preferably, the method further includes:

[0091] Step 7: If the self-test fails, control the voltage input of the voltage regulator to the standard current transformer to return to zero, stop the self-test, and then repair the on-site calibration system.

[0092] In this embodiment of the invention, a self-test was performed on a wide-range current transformer field calibration system, such as... Figure 5As shown, the process includes:

[0093] S1. Before powering on, connect the field verification system according to the wiring method required by the procedure, and reliably ground the grounding terminal of the field verification system.

[0094] S2, connect the power cord, connect to a 220V power supply, and close the power switch. Confirm that the main and auxiliary coordinated voltage regulator is in the zero position, and the zero position indicator light will illuminate.

[0095] S3, input the verification ratio of the current transformer under test;

[0096] S4, controlled by the self-test software in the CPU, switches the primary winding to the primary tap corresponding to the verification ratio, thus short-circuiting the primary current boosting circuit.

[0097] S5, controlled by the self-test software in the CPU, switches the secondary winding to the secondary tap corresponding to the verification ratio, so that it is connected to the error measurement device T0 and K terminals;

[0098] S6, the self-test software starts to control the current to slowly increase to 10%In, and monitors the change of the "I / In (%)" percentage in the error check device. If the output voltage of the main and auxiliary coordinated voltage regulating power supply increases, the I / In (%) percentage will increase with the increase of the output voltage, and it can normally display several or one percentage current points of 0.1%, 1%, 5%, or 10%, then the self-test is qualified.

[0099] If the output voltage of the main and auxiliary coordinated voltage regulating power supply increases while the "I / In (%)" percentage does not change when adjusting within 10%In, it may be a power supply failure or a disconnection of the primary or secondary winding of the standard device. The wiring of the primary and secondary windings of the power supply and the standard device needs to be checked. Self-test fails.

[0100] If the corresponding percentage is not linear, it may be that the primary or secondary winding connection is not secure. The connection of the primary and secondary windings needs to be checked. Self-test failed.

[0101] If a polarity error message is displayed, it means that the polarity terminals of the primary and secondary windings of the standard current transformer are reversed, and the self-test fails.

[0102] S7. According to the test requirements, switch the short-circuit taps of the primary winding and the secondary winding, and repeat the above actions to complete the self-test of all test ratios.

[0103] If the self-test fails, the self-test software controls the main and auxiliary power supply to quickly return to zero. Stop the test and inspect the calibration system.

[0104] The beneficial effects of this invention are that, compared with the prior art, the field verification system and its self-testing method proposed in this invention can easily and quickly determine whether the wide-range current transformer and the verification system can work normally and whether there is a fault. It can greatly improve the safety and accuracy of field testing of wide-range current transformers; it can complete the field verification of current transformers with different ratios, and the wiring is simple, convenient and quick, with a wide range of applications.

[0105] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0106] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0107] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0108] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A wide-range current transformer field calibration system, comprising: The system comprises a voltage regulator, a current booster, a standard current transformer, a current transformer under test, and a load cell; wherein the voltage regulator is connected to the standard current transformer via the current booster, the standard current transformer is connected to the current transformer under test, and then connected to the load cell; its key feature is: The field verification system also includes a self-testing circuit and an error verification device; The first and last ends of the primary winding of a standard current transformer are L1 and LN, respectively, and multiple primary winding taps are provided between the first and last ends of the primary winding. The first and last ends of the secondary winding are S1 and Sn, respectively, and multiple secondary winding taps are provided between the first and last ends of the secondary winding. The end of the primary winding of the standard current transformer is connected to the beginning of the primary winding of the current transformer under test. The beginning of the primary winding of the standard current transformer and the end of the primary winding of the current transformer under test are connected to the beginning and end of the secondary winding of the current booster. The end of the secondary winding of the standard current transformer is connected to the beginning of the secondary winding of the current transformer under test. The error verification device includes a first measuring terminal T0 connected to the beginning of the secondary winding of a standard current transformer, a second measuring terminal K connected to the end of the secondary winding of the standard current transformer and the beginning of the secondary winding of the current transformer under test, and a third measuring terminal Tx connected to the end of the secondary winding of the current transformer under test through a load box. The self-test circuit includes a primary tap switch group connected to the taps of each primary winding of the standard current transformer, and a secondary tap switch group connected to the taps of each secondary winding of the standard current transformer. By switching the primary tap switch group and the secondary tap switch group together, multiple transformation ratios of the standard current transformer can be realized. n-1 taps are installed between the beginning and end of the primary winding of a standard current transformer, and n-2 taps are installed between the beginning and end of the secondary winding of a standard current transformer. The primary tap switch group includes n primary tap switches. The first primary tap switch is connected in parallel between the end LN of the primary winding of the standard current transformer and the end of the output winding of the current booster. The second to nth primary tap switches are connected between the n-1 primary winding taps of the primary winding of the standard current transformer and the end LN of the primary winding. The secondary tap switch group includes n secondary tap switches. One end of the second to nth secondary tap switches is connected to the first to n-2 taps of the secondary winding of the standard current transformer and the end of the secondary winding, respectively. The other ends of the second to nth secondary tap switches are connected together and then connected to the third measuring terminal Tx of the error verification device through the first secondary tap switch.

2. The wide-range current transformer field verification system according to claim 1, characterized in that: The field verification system also includes a measurement and control module. The output control terminal of the measurement and control module is connected to the control terminal of the voltage regulating power supply, the control terminal of the primary tap switch group and the control terminal of the secondary tap switch group. The output current boost signal controls the output voltage of the voltage regulating power supply, and the output standard transformer primary winding tap control signal and secondary winding tap control signal control the switching of each primary tap switch and secondary tap switch to realize multiple transformation ratios of the standard current transformer. The input terminal of the measurement and control module receives the dial indicator signal and differential current signal output from the error verification device.

3. The wide-range current transformer field verification system according to claim 2, characterized in that: When the current input to the standard current transformer from the current booster is zero, the closing or opening of n primary tap switches and n secondary tap switches is controlled to make the transformation ratio of the standard voltage transformer consistent with the calibration transformation ratio of the current transformer under test. Then, the voltage regulator is controlled to increase the voltage rise and fall so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer. If the percentage value of the current output by the error verification device increases with the voltage of the voltage regulator and the displayed value meets the accuracy indication value and the standard indication value specified in the procedure, then the self-test of the field verification system is deemed qualified; otherwise, the self-test of the field verification system is deemed unqualified. The accuracy value is 0.1%; the standard values ​​specified in the regulations include 1%, 5%, and 10%.

4. The wide-range current transformer field verification system according to claim 2, characterized in that: If the self-test fails, and the voltage of the adjustable power supply increases but the current percentage value output by the error verification device does not change, then the power supply is determined to be faulty, or the primary or secondary winding of the standard current transformer is disconnected.

5. The wide-range current transformer field verification system according to claim 1, characterized in that: If the self-test fails and the current percentage value output by the error verification device increases non-linearly with the increase of the voltage of the voltage regulating power supply, it is determined that the primary or secondary winding of the standard current transformer is not securely connected.

6. The wide-range current transformer field verification system according to claim 1, characterized in that: If the self-test fails and the error verification device displays a polarity error, the output current percentage value will increase non-linearly as the voltage of the voltage regulator increases, which indicates that the polarity terminals of the primary and secondary windings of the standard current transformer are reversed.

7. The wide-range current transformer field verification system according to claim 1, characterized in that: The n-group tap switches of the primary winding are three-phase contactors, and the operating current is 1 / 3 of the primary rated current.

8. The wide-range current transformer field verification system according to claim 1, characterized in that: The nth tap switch of the secondary winding is a relay with an operating current of 10A.

9. A self-testing method for a wide-range current transformer field calibration system, implemented using the self-testing system of the wide-range current transformer field calibration system according to any one of claims 1 to 8, characterized in that, The method includes: Step 1: The voltage input to the standard current transformer from the regulated power supply is zero; Step 2: Use the verification ratio of the tested current transformer as the ratio of the standard voltage transformer; Step 3: According to the transformation ratio of the standard voltage transformer, control the first primary tap switch to close, and control any tap switch from the second primary tap switch to the nth primary tap switch to close, and connect the corresponding primary winding tap terminal to the current booster. Step 4: According to the transformation ratio of the standard voltage transformer, control the first secondary tap switch to close, and control any tap switch from the second secondary tap switch to the nth secondary tap switch to close, so that the corresponding secondary winding tap end and tail end are connected to the current booster. Step 5: Control the voltage rise and fall of the voltage regulator so that the current output of the current booster rises to 10%In, where In is the primary rated current of the standard current transformer. Step 6: Perform a self-test on the field verification system. If the current percentage value output by the error verification device increases with the voltage of the voltage regulator and the displayed value is 0.1%, 1%, 5%, or 10%, then the self-test is qualified; otherwise, the self-test is deemed unqualified.

10. The self-testing method of the wide-range current transformer field calibration system according to claim 9, characterized in that, In step 1, when the first tap switch is closed, and when any one of the tap switches from the second tap switch to the nth tap switch is closed, all other tap switches are open.

11. The self-testing method of the wide-range current transformer field calibration system according to claim 9, characterized in that, In step 2, when the first tap switch is closed, and any tap switch from the second tap switch to the nth tap switch is closed, all other tap switches are open.

12. The self-testing method of the wide-range current transformer field calibration system according to claim 9, characterized in that, The method further includes: Step 7: If the self-test fails, control the voltage input of the voltage regulator to the standard current transformer to return to zero, stop the self-test, and then repair the on-site calibration system.

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