Synchronous Verification Method and System for Line Voltage Error of Y-Connected Three-Phase Voltage Transformers

Abstract

This application discloses a method and system for synchronously verifying line voltage errors of a Y-connected three-phase voltage transformer, relating to the fields of power system energy metering and transformer calibration technology. It employs three standard voltage transformers connected in a delta configuration to provide three sets of reference line voltages (A-B, B-C, C-A) without neutral point dependence; and uses a three-phase isolation transformer to convert the original line voltages a–b, b–c, and c–a of the Y-connected three-phase voltage transformer into electrically isolated a′–a. x b′–b x c′–c x Output; where a x b x c x It can be uniformly connected to the common ground interface of a three-phase transformer calibrator; the three sets of reference signals and the three sets of calibrated signals are synchronously acquired within a single boost cycle; this application solves the technical problems of existing three-phase transformer calibrators being unable to synchronously connect to the three-phase line voltage for error comparison, and only being able to verify one phase at a time, resulting in low efficiency, poor wiring repeatability, and system deviation introduced by neutral point offset.

Description

Technical Field

[0001] This application relates to the field of power system energy metering and transformer verification technology, specifically to a method and system for synchronously verifying line voltage error of a Y-connected three-phase voltage transformer. Background Technology

[0002] In the current construction of intelligent substations and high-precision power metering systems, error verification of three-phase voltage transformers (PTs) is a crucial link in ensuring the reliability of power settlement and relay protection operations. According to JJG 1021—2023 "Verification Procedure for Power Transformers" and DL / T 1245—2022 "Technical Guidelines for On-site Verification of Voltage Transformers," the mainstream verification method is a comparative measurement using a three-phase voltage transformer calibrator in conjunction with a standard. In existing technologies, conventional three-phase voltage transformer calibrators are designed with phase voltage verification as their core objective. Their hardware interfaces define clearly defined high / low potential terminals and default to grounding the low-potential terminal of the secondary side of the transformer to be calibrated. Standard voltage transformers also use a Y-connection and share a neutral point, meeting the "relative to zero" verification requirement. This type of equipment has been widely deployed in provincial metering centers, power plants, and substations, possessing high stability, multi-point automatic voltage ramping and ramping capabilities, and automatic error interpretation capabilities, forming the technical foundation for current on-site verification of voltage transformers.

[0003] However, the aforementioned existing technologies have significant limitations: on the one hand, in practical applications, the primary neutral point of a Y-connected three-phase voltage transformer is often not brought out, making it impossible to construct a reliable common reference zero potential. This causes the phase voltage verification results to be affected by the neutral point offset, making it impossible to accurately verify the error of this type of three-phase voltage transformer; on the other hand, although the line voltage (U AB U BC U CA Verification does not require a neutral point connection, which is theoretically more accurate. However, existing three-phase current transformer calibrators do not provide three independently isolated line voltage input channels. Their internal circuit structure is still designed based on "single standard signal + single calibration signal," making it impossible to achieve synchronous acquisition and parallel comparison of three-phase line voltages. They can only complete three independent verifications phase by phase, which is time-consuming, involves repeated wiring, and carries a high risk of human error. Furthermore, because the three secondary terminals a, b, and c of a Y-connected current transformer are all floating high potentials, any two points will have a line voltage output. Current three-phase current transformer calibrators only allow one low-potential terminal to be grounded. Forcibly connecting three sets of line voltages will cause a terminal short circuit or instrument protection lockout, resulting in verification interruption. Therefore, there is an urgent need for a technical solution that does not change the hardware structure of existing three-phase current transformer calibrators, but only requires external conversion and standard reconfiguration to achieve synchronous verification of three-phase line voltage errors in Y-connected current transformers. This would break through the functional limitations of traditional verification equipment and improve the efficiency and accuracy of metrological verification. Summary of the Invention

[0004] The purpose of this application is to provide a method and system for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer. This method can achieve synchronous verification of the three-phase line voltage error based on existing instruments. This application addresses the problem that existing three-phase transformer verification instruments, due to their phase voltage-oriented design, default single-point grounding, and lack of a line voltage reference source and the ability to reconstruct the potential of the calibrated side, cannot verify the three sets of line voltages (U0, U0, U0) of a Y-connected three-phase voltage transformer. AB U BC U CA The synchronous acquisition and parallel comparison process results in technical problems such as low verification efficiency, poor wiring repeatability, and system deviation caused by neutral point offset.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In a first aspect, this application provides a method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer, including:

[0007] The primary windings of three standard voltage transformers are connected in a delta configuration to the corresponding A, B, and C phase lines of the three-phase test power supply. Three sets of line voltages (AB, BC, and CA) are obtained from the secondary windings as reference signals. The output terminals are defined as high potential a0 / b0 / c0 and low potential a... x / b x / c x ;

[0008] A three-phase isolation transformer is connected to the secondary side of the three-phase voltage transformer connected in the Y-connection. The input terminal receives the original line voltages a–b, b–c, and c–a, and the output terminal generates three electrically isolated signals a′–a. x b′–b x c′–c x , where a x b x c x It serves as a common ground terminal and is also connected to the unified grounding interface of the three-phase transformer calibrator.

[0009] a0–a x b0–b x c0–c x The three sets of reference voltages are respectively connected to the standard channels of the three-phase transformer calibrator, and a′–a x b′–b x c′–c x Three sets of voltages to be calibrated are connected to the calibration channel of the three-phase transformer calibrator; all terminals synchronously collect ratio difference and phase difference data within a single boost cycle.

[0010] As a further improvement of this application, the turns ratio of the primary winding to the secondary winding of the three-phase isolation transformer is 1:1, the amplitude error is ≤±0.01%, the phase difference is ≤0.3′, and it supports linear response within the range of 20% to 120% of the rated voltage.

[0011] As a further improvement to this application, the isolation transformer adopts a three-phase five-limb iron core structure, with physical isolation between the primary and secondary windings, and the power frequency withstand voltage between each phase is ≥3kV.

[0012] As a further improvement to this application, the a x b x c x All three terminals are connected to the same low-potential grounding busbar, with a busbar width ≥ 50mm, thickness ≥ 5mm, material T2 copper, and grounding resistance ≤ 0.1Ω.

[0013] As a further improvement of this application, an insulation status monitoring module is provided between the grounding busbar and the housing of the three-phase transformer calibrator. The insulation status monitoring module collects the ground leakage current of the grounding busbar in real time and alarms accordingly.

[0014] As a further improvement of this application, the three-channel mutual inductor calibrator adopts a unified trigger signal to control the synchronous sampling of the three-channel ADC, with sampling jitter ≤1ns; all channels use the same TCXO reference clock.

[0015] As a further improvement to this application, during the verification process, a′–a x Three-phase harmonic disturbances are injected into the channel to verify that the three-phase mutual inductor calibrator still has the ability to judge synchronization error under non-sinusoidal voltage conditions.

[0016] As a further improvement to this application, the three-phase transformer calibrator constructs a joint least squares error model based on three sets of measured line voltage values ​​and simultaneously calculates U... AB U BC U CA The comprehensive error index.

[0017] As a further improvement to this application, the method for achieving synchronous measurement of three-phase line voltage errors includes:

[0018] Error verification was performed at 20%, 50%, 80%, 100%, and 120% of the rated voltage, and at 25% and 100% of the rated load.

[0019] Secondly, this application provides a synchronous verification system for line voltage error of a Y-connected three-phase voltage transformer, which implements the aforementioned method for synchronous verification of line voltage error of a Y-connected three-phase voltage transformer, including:

[0020] Three standard voltage transformers are used. The primary windings of these three standard voltage transformers are connected in a delta configuration to the corresponding A, B, and C phases of the three-phase test power supply. The secondary windings of these transformers obtain three sets of line voltages (AB, BC, and CA) as reference signals. The output terminals are defined as high potential a0 / b0 / c0 and low potential a... x / b x / c x ;

[0021] A three-phase isolation transformer is connected to the secondary side of the three-phase voltage transformer in a Y-connection configuration under test. The primary side of the three-phase voltage transformer is connected to the corresponding A, B, and C phase lines of the three-phase test power supply. The input of the three-phase isolation transformer receives the original line voltages a–b, b–c, and c–a from the three-phase voltage transformer in a Y-connection configuration under test, and the output generates three electrically isolated signals a′–a. x b′–b x c′–c x , where a x b x c x It serves as a common ground terminal and is also connected to the unified grounding interface of the three-phase transformer calibrator.

[0022] Three-phase mutual inductor calibrator, used to receive a0–a x b0–b x c0–c x Three sets of reference voltages and a′–a x b′–b x c′–c x Three sets of voltages to be calibrated; all terminals synchronously acquire ratio and phase difference data within a single boost cycle.

[0023] Compared with the prior art, this application provides a method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer, which has the following advantages:

[0024] Existing solutions lack line voltage reference sources and potential reconstruction capabilities, requiring multiple wiring and voltage boosting operations for the three sets of line voltages, resulting in a cumbersome and time-consuming process. This method, through standard-side delta connection and potential reconstruction on the calibrated side, achieves synchronous acquisition and parallel comparison of the three sets of line voltages within a single voltage boosting cycle, directly eliminating the time cost of multiple wiring and voltage boosting operations and improving calibration efficiency. If the secondary side of the Y-connected transformer is directly connected to a three-phase transformer calibrator, inconsistencies in grounding methods can easily lead to neutral point offset, introducing system deviations. This method, through a unified grounding interface design and three-phase isolation transformer potential reconstruction, ensures complete consistency between the standard side and the calibrated side potential references, eliminating errors caused by neutral point offset at the source and significantly improving the accuracy of line voltage error calibration. Traditional multi-stage calibration requires repeated disassembly and reassembly of the three sets of line voltages, which can easily introduce repeatability errors due to variations in wiring tightness and terminal contact conditions. This method only requires one wiring operation to complete the calibration of all three sets of line voltages, significantly reducing manual operations and improving the consistency and reliability of calibration results. This method eliminates the need for dedicated line voltage verification equipment. It expands the functionality of existing three-phase transformer calibrators simply by modifying standard voltage transformer delta connections and adding a three-phase isolation transformer. The modification cost is low, and the operation is easy, making it suitable for rapid application in fields such as power testing and transformer verification.

[0025] Other advantages, objectives and features of this application will be set forth in part in the description which follows; and in part will be apparent to those skilled in the art upon examination of the following description; or may be learned from practice of this application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the delta connection of the three-phase standard voltage transformer in this application;

[0027] Figure 2 This is a schematic diagram of the three-phase isolation transformer converting the secondary output of the three-phase voltage transformer under test in this application;

[0028] Figure 3 This is a schematic diagram of the three-phase line voltage error synchronous verification circuit of this application. Detailed Implementation

[0029] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] Explanation of relevant terms:

[0032] Phase voltage: In a three-phase AC circuit, the voltage between the phase line (live wire) and the neutral line (zero wire).

[0033] Line voltage: In a three-phase AC circuit, the voltage between phase lines (live wires).

[0034] Y-connected three-phase voltage transformer: An electrical device that connects the primary and secondary windings of a three-phase transformer in a star (Y) configuration to measure the line voltage and phase voltage of a three-phase circuit.

[0035] Delta connection: In a three-phase circuit, the beginning and end of three components (such as windings and loads) are connected in sequence to form a closed delta circuit.

[0036] Voltage transformer error verification: The process of measuring the ratio difference and phase difference of a voltage transformer under a specified voltage using specialized equipment to determine whether the error meets the requirements;

[0037] Three-phase current transformer calibrator: A specialized testing device that can simultaneously measure the ratio difference and phase angle difference of a three-phase current transformer or voltage transformer to verify whether its error meets the standard.

[0038] Isolation transformer: A type of transformer that isolates the input and output circuits through electrical insulation between the primary and secondary windings, and transmits electrical energy only through electromagnetic induction.

[0039] This application addresses the technical problems of existing three-phase current transformer calibrators, which are designed to face phase voltage and default to single-point grounding. In contrast, the secondary side terminals a, b, and c of Y-connected current transformers are all floating at high potentials, and at most only one terminal can be grounded. This results in the inability to synchronously connect the three-phase line voltage for error comparison, and the inability to verify each phase one by one. This leads to low efficiency, poor wiring repeatability, and system deviation caused by neutral point offset.

[0040] Error verification of Y-connected three-phase voltage transformers is divided into two methods: phase voltage error verification (relative to zero) and line voltage error verification (phase-to-phase). Phase voltage error verification (relative to zero) can be performed by simultaneously measuring the three-phase error using a three-phase voltage transformer calibrator. However, it requires connecting the primary neutral point of the three-phase voltage transformer to be calibrated, the neutral point of the three-phase voltage source, and the neutral point of the three-phase standard voltage transformer together to perform accurate verification. For some three-phase voltage transformers where the primary neutral point is not brought out, this verification method often fails to provide accurate verification results for Y-connected three-phase voltage transformers due to the actual potential shift of the neutral point. Line voltage error verification (phase-to-phase) does not require connecting the neutral point of the three-phase voltage transformer under test. It is a method that can accurately verify the error of any three-phase voltage transformer. However, currently available three-phase voltage transformer calibrators are designed for phase voltage error verification. The secondary terminals of the standard voltage transformer and the voltage transformer under test are connected to the calibrator with high and low potentials respectively. Furthermore, the low potential terminal of the secondary side of the Y-connected three-phase voltage transformer is grounded by default. Since only one of the three secondary terminals of the Y-connected three-phase voltage transformer can be grounded at most, conventional methods cannot simultaneously verify the three-phase line voltage error. This invention proposes a synchronous verification method for the line voltage error of Y-connected three-phase voltage transformers, which can achieve synchronous verification of the three-phase line voltage error based on existing instruments.

[0041] Currently, the line voltage error verification of Y-connected three-phase voltage transformers is performed phase-by-phase due to the limitations of the three-phase transformer verification instruments. This means that the AB, BC, and AC phases are checked three times sequentially. According to national standards and metrological specifications, error verification needs to be performed at 20%, 50%, 80%, 100%, and 120% of the rated voltage, as well as at 25% and 100% of the rated load. This results in numerous test points, making the phase-by-phase verification method inefficient.

[0042] Currently, all three-phase voltage transformer calibrators on the market are designed for phase voltage error verification. The secondary terminals of the standard voltage transformer and the voltage transformer being calibrated are connected to the three-phase voltage transformer calibrator with high and low potentials respectively. Furthermore, the secondary low potential terminal of the Y-connected three-phase voltage transformer is grounded by default. However, at most one of the three secondary terminals of the Y-connected three-phase voltage transformer can be grounded. Therefore, conventional methods cannot simultaneously perform three-phase line voltage error verification.

[0043] Therefore, this application provides a method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer. This method, through standard side reference voltage generation, calibrated side potential reconstruction, and three-channel synchronous acquisition, completes the parallel comparison of the three-phase line voltage error of the Y-connected transformer without modifying the existing three-phase transformer calibration instrument hardware; it includes the following steps:

[0044] Three fully insulated standard voltage transformers without neutral point leads were used. Their primary windings were connected in a delta configuration to form a test circuit. Three sets of line voltages (AB, BC, and CA) were obtained from the secondary windings as reference signals. The output terminals were defined as high potential a0 / b0 / c0 and low potential a0 / c0 / c0. x / b x / c x ;

[0045] A three-phase isolation transformer with a turns ratio of 1:1 is connected to the secondary side of the three-phase voltage transformer connected in the Y-connection. The input terminal receives the original line voltages a–b, b–c, and c–a, and the output terminal generates three electrically isolated signals a′–a. x b′–b x c′–c x , where a x b x c x It is a common ground terminal, which can be connected to the unified grounding interface of a three-phase transformer calibrator at the same time;

[0046] a0–a x b0–b x c0–c x The three sets of reference voltages are respectively connected to the standard channels of the three-phase mutual inductor calibrator, and a′–a x b′–b x c′–c x Three sets of voltages to be calibrated are connected to the calibration channel of the three-phase transformer calibrator; all six sets of terminals synchronously collect ratio difference and angle difference data within a single boost cycle;

[0047] A joint least squares error model was constructed based on three sets of measured line voltage values, and U was calculated simultaneously. AB U BC U CA The comprehensive error index eliminates the inconsistency deviations introduced by timing drift and contact resistance in phase-by-phase verification, and achieves synchronous verification in accordance with Clause 7.4 of JJG1021—2023 and Clause 5.2 of DL / T 1245—2022.

[0048] In the above scheme, the three-phase standard voltage transformer delta connection scheme uses three independent ungrounded standard voltage transformers as reference standards, and adopts a delta connection method to provide standard reference phase-to-phase voltages for the three-phase voltage transformer calibrator. The three-phase isolation transformer conversion scheme for the secondary output of the tested three-phase voltage transformer specifically uses a 1:1 three-phase isolation transformer to convert the three sets of secondary output line voltages ab, bc, and ca of the tested three-phase voltage transformer into three mutually isolated outputs a'-a. x b'-b x c'-c x .

[0049] The principle of this application is to achieve synchronous acquisition and error comparison of the line voltage of a Y-connected three-phase voltage transformer by optimizing the standard side wiring and reconstructing and electrically isolating the potential of the tested side. The direct construction of the standard side line voltage reference source is necessary because existing three-phase voltage transformer calibrators are designed to face phase voltage by default and cannot directly output line voltage reference signals. This method connects the primary windings of three standard voltage transformers to the three-phase test power supply in a delta connection. Utilizing the electrical characteristics of the delta connection—the winding voltage is naturally equal to the line voltage—the three sets of line voltages UAB, UBC, and UCA are directly obtained from the secondary windings as reference signals. Simultaneously, high / low potential terminals (a0 / b0 / c0 and a...) are defined. x / b x / c x This lays the foundation for subsequent common-ground comparison. The potential reconstruction and electrical isolation of the calibrated side are due to the problem that the primary line voltage on the secondary side of the Y-connected three-phase voltage transformer has inconsistent potential and the neutral point is prone to shift. Directly connecting it to the three-phase transformer calibrator will introduce system deviation.

[0050] Furthermore, this method achieves two core functions by connecting a three-phase isolation transformer to the calibrated side: electrical isolation and potential reconstruction. Electrical isolation cuts off stray current paths between the calibrated side and the three-phase transformer calibrator, avoiding the impact of external interference on calibration accuracy. Potential reconstruction converts the native line voltages a–b, b–c, and c–a into a signal a′–a that shares a common ground with the standard side. x b′–b x c′–c x This allows the standard channel and the channel being calibrated to share a unified grounding interface (a x / b x / c xThis eliminates potential difference deviations caused by inconsistent grounding. Finally, the standard-side reference voltage and the reconstructed voltage on the calibrated side are connected to the standard channel and the calibrated channel of the three-phase transformer calibrator, respectively, and the ratio and angle difference data of the three sets of line voltages are collected synchronously within a single boost cycle. Compared to the traditional segmented acquisition mode, synchronous acquisition avoids errors caused by voltage fluctuations and environmental interference during the boost process in terms of timing.

[0051] This application employs a delta-connected arrangement of three independent, fully insulated standard voltage transformers. It utilizes a three-phase isolation transformer to isolate the secondary outputs of the three-phase voltage transformers under test into three independent outputs. The technical solution of this application is described in detail below with reference to the accompanying drawings and embodiments:

[0052] This embodiment provides a method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer, achieving synchronous verification of the three-phase line voltage error based on existing instruments. The specific scheme is as follows:

[0053] Step 1: Three-phase standard voltage transformer delta connection scheme. Three independent ungrounded standard voltage transformers are used as reference standards and connected in delta configuration to provide standard reference phase-to-phase voltages for the three-phase transformer calibrator.

[0054] Step 2: Convert the secondary output scheme of the three-phase voltage transformer under test using a three-phase isolation transformer. Using a 1:1 three-phase isolation transformer, the three sets of secondary output line voltages ab, bc, and ca of the three-phase voltage transformer under test are converted into three mutually isolated outputs a'-a. x b'-b x c'-c x .

[0055] like Figure 1 The diagram shows a delta connection of three-phase standard voltage transformers. Three independent, ungrounded standard voltage transformers are used as reference standards and connected in a delta configuration to provide a standard reference phase-to-phase voltage for the three-phase transformer calibrator. The three independent ungrounded standard voltage transformers are TV... A TV B TV C TV A The voltage between phases A and B is measured, and the secondary output is a0-a. x0 TV B The secondary output of the phase-to-phase voltage (BC) is b0-b. x0 TV C The phase-to-phase voltage of CA is measured, and the secondary output is c0-c. x0 ; respectively provide reference signals to the three-phase standard input of the three-phase mutual inductor calibrator.

[0056] The primary windings of the three standard voltage transformers are connected in a closed loop, A→B→C→A, and the secondary winding output terminals are a0–a. x b0–b x c0–c x Each phase is independently grounded, forming a pure delta-shaped reference voltage source. This triangular structure is the fundamental guarantee of the independence of the standard side error. It ensures that the three-phase reference source itself is not affected by neutral point offset, meeting the basic requirement of stable metrological reference.

[0057] like Figure 2 The diagram shows the conversion of the secondary outputs of the three-phase voltage transformer under test using a three-phase high-precision isolation transformer. A 1:1 three-phase isolation transformer is used to convert the secondary line voltages ab, bc, and ca of the three-phase voltage transformer under test into three mutually isolated outputs a'-a. x b'-b x c'-c x , where a x b x c x It can be grounded simultaneously, providing calibration signals to the three-phase inputs of the three-phase mutual inductor calibrator.

[0058] like Figure 3 As shown, this is a three-phase line voltage error synchronous verification circuit. Three fully insulated standard voltage transformers are selected to measure the line voltages of groups AB, BC, and CA respectively. The three secondary terminals of the three standard voltage transformers can be defined as a0, b0, and c0 as high potentials, and a0 is defined as high potential. x0 b x0 c x0 The voltage is low, but since the secondary line voltage terminals a, b, and c of the three-phase voltage transformer under test are all high-voltage terminals, it is impossible to define a low-voltage terminal to connect to the existing three-phase voltage transformer calibrator for synchronous line voltage error verification. Therefore, a three-phase isolation transformer (with a 1:1 turns ratio between the primary and secondary windings) is used to convert the secondary line voltages ab, bc, and ca of the three-phase voltage transformer under test into mutually isolated a'-a' terminals. x b'-b x c'-c x Therefore, we can define a', b', and c' as high potentials, and define a... x b x c x The voltage is low, and it is connected to the existing three-phase transformer calibrator to realize synchronous measurement of three-phase line voltage error.

[0059] The isolation transformer adopts a three-phase five-limb core structure with physical isolation between the primary and secondary windings. The power frequency withstand voltage between each phase is ≥3kV, and it has passed the type test verification of GB / T 20840.3—2022, Clause 9.3. The five-limb core is a key structure for achieving zero-sequence flux shunting in the three-phase isolation transformer. The middle limb balances the zero-sequence component, the two side limbs carry the main flux, and the other two limbs assist in heat dissipation and shielding. This structure significantly suppresses three-phase coupling interference, making a′–a x b′–b x c′–c x The crosstalk suppression ratio of the three outputs reaches -85dB (@50Hz), and the measured phase-to-phase isolation is >120dB. The winding adopts a foil structure (0.15mm thick aluminum foil), with a 25μm thick polyimide film added between the layers, and cured by vacuum pressure impregnation (VPI) process. This design keeps the temperature rise below 45K (under rated load) and ensures high long-term operational stability. In practical applications, the core structure can be replaced with a three-dimensional wound core or a shell structure.

[0060] The a x b x c x The three terminals are connected to the same low-potential grounding busbar, with a width ≥50mm, thickness ≥5mm, and material of T2 copper. The grounding resistance is ≤0.1Ω. An insulation status monitoring module is installed between the grounding busbar and the housing of the three-phase transformer calibrator to collect the ground leakage current of the grounding busbar in real time and trigger an alarm.

[0061] The three-channel mutual inductor calibrator uses a unified trigger signal to control the synchronous sampling of the three-channel ADC, with sampling jitter ≤1ns; all channels use the same TCXO reference clock (10MHz), which is multiplied to 100MHz by a phase-locked loop to ensure strict alignment of the time axis.

[0062] Additionally, refer to Figure 3 This application provides a synchronous verification system for line voltage error of a Y-connected three-phase voltage transformer, which implements the above-mentioned method for synchronous verification of line voltage error of a Y-connected three-phase voltage transformer, including:

[0063] Three standard voltage transformers are used. The primary windings of these three standard voltage transformers are connected in a delta configuration to the corresponding A, B, and C phases of the three-phase test power supply. The secondary windings of these transformers obtain three sets of line voltages (AB, BC, and CA) as reference signals. The output terminals are defined as high potential a0 / b0 / c0 and low potential a... x / b x / c x ;

[0064] A three-phase isolation transformer is connected to the secondary side of the three-phase voltage transformer in a Y-connection configuration under test. The primary side of the three-phase voltage transformer is connected to the corresponding A, B, and C phase lines of the three-phase test power supply. The input of the three-phase isolation transformer receives the original line voltages a–b, b–c, and c–a from the three-phase voltage transformer in a Y-connection configuration under test, and the output generates three electrically isolated signals a′–a. x b′–b x c′–c x , where a x b x c x It serves as a common ground terminal and is also connected to the unified grounding interface of the three-phase transformer calibrator.

[0065] Three-phase mutual inductor calibrator, used to receive a0–a x b0–b x c0–c x Three sets of reference voltages and a′–a x b′–b x c′–c x Three sets of voltages to be calibrated; all terminals synchronously acquire ratio and phase difference data within a single boost cycle.

[0066] Based on the above description, the solution in this application, in accordance with national standards and metrological specifications, can perform error verification at 20%, 50%, 80%, 100%, and 120% of rated voltage, as well as 25% and 100% of rated load. It has a large number of test points and adopts a three-phase synchronous verification method, which is applicable to all types of three-phase voltage transformers. It does not require repeated adjustments to the wiring and can significantly improve verification efficiency.

[0067] This method compresses the line voltage verification of Y-connected current transformers from three independent operations into a single operation, improving verification efficiency by 73% and reducing the total test time from 45 minutes to 12 minutes. Three-phase joint fitting effectively suppresses common interference terms (such as power fluctuations, temperature drift, and electromagnetic crosstalk), reducing the overall ratio difference uncertainty from ±0.025% to ±0.009% (k=2), which is better than the ±0.01% limit specified in JJG 1021—2023. Through three-phase common grounding and insulation status monitoring, multi-channel grounding consistency is ensured, eliminating false out-of-tolerance errors caused by single wiring defects. The constructed Δ-connection reference source possesses natural phase self-consistency, eliminating the need for external phase-locking and avoiding phase voltage verification distortion caused by neutral point offset. The overall solution is compatible with all current mainstream three-phase current transformer calibrators, has passed on-site comparison verification by provincial metrology institutes, and meets CNAS accreditation requirements.

[0068] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer, characterized in that, include: Three independent, fully insulated standard voltage transformers without neutral points are connected in a delta configuration in a closed loop to the corresponding A, B, and C phase lines of the three-phase test power supply. The three standard voltage transformers measure the inter-phase line voltages of AB, BC, and CA, respectively. Each standard voltage transformer has an independent output terminal on its secondary winding; the secondary output high-potential terminal is defined as... The low potential terminal is The three sets of line voltages AB, BC, and CA are obtained from the secondary winding as reference signals respectively; A three-phase isolation transformer is connected to the secondary side of the three-phase voltage transformer connected in the Y-connection under test. The primary side of the three-phase isolation transformer is the signal input terminal, and the secondary side is the isolation signal output terminal. The primary output terminals of the secondary side of the three-phase voltage transformer connected in the Y-connection under test are a, b, and c, and the primary line voltages a–b, b–c, and c–a are output between each pair. The input terminal of the three-phase isolation transformer receives the primary line voltages a–b, b–c, and c–a, and the isolation signal output terminal generates three sets of electrically isolated signals. , , ,in , , To isolate the high-potential output terminal, , , It serves as a common ground terminal and is also connected to the unified grounding interface of the three-phase transformer calibrator. Will , , The three sets of reference voltages are respectively connected to the standard channels of the three-phase transformer calibrator. , , The three sets of voltages to be calibrated are connected to the calibration channel of the three-phase transformer calibrator; all terminals synchronously collect ratio difference and angle difference data within a single boost cycle to achieve synchronous measurement of three-phase line voltage error.

2. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: The turns ratio of the primary winding to the secondary winding of the three-phase isolation transformer is 1:

1.

3. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: The isolation transformer adopts a three-phase five-column iron core structure, with physical isolation between the primary and secondary windings.

4. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: The a x b x c x All three terminals are connected to the same low-potential grounding busbar, with a busbar width ≥ 50mm, a thickness ≥ 5mm, and a grounding resistance ≤ 0.1Ω.

5. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 4, characterized in that: An insulation status monitoring module is installed between the grounding busbar and the housing of the three-phase transformer calibrator. The insulation status monitoring module collects the ground leakage current of the grounding busbar in real time and alarms accordingly.

6. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: The three-channel mutual inductor calibrator uses a unified trigger signal to control the synchronous sampling of the three-channel ADC.

7. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: During the verification process, a′–a x Three-phase harmonic disturbances are injected into the channel to verify whether the three-phase mutual inductor calibrator has the ability to judge synchronization error under non-sinusoidal voltage conditions.

8. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: The three-phase transformer calibrator constructs a joint least squares error model based on three sets of measured line voltage values ​​for synchronous calculation. , , The comprehensive error index; among which The line voltage between phases A and B of the three-phase system. The line voltage between phases BC in the three phases. This refers to the three-phase CA phase-to-phase line voltage.

9. The method for synchronously verifying the line voltage error of a Y-connected three-phase voltage transformer according to claim 1, characterized in that: To achieve synchronous measurement of three-phase line voltage errors, including: Error verification was performed at 20%, 50%, 80%, 100%, and 120% of the rated voltage, and at 25% and 100% of the rated load.

10. A synchronous verification system for line voltage error of a Y-connected three-phase voltage transformer, implementing the synchronous verification method for line voltage error of a Y-connected three-phase voltage transformer as described in any one of claims 1 to 9, characterized in that, include: Three standard voltage transformers are used. The three standard voltage transformers are independent, fully insulated structures without a neutral point. The primary windings of the three standard voltage transformers are connected in a delta connection to the corresponding A, B, and C phase lines of the three-phase test power supply. The three sets of interphase line voltages AB, BC, and CA are measured respectively. The three sets of line voltages AB, BC, and CA are obtained from the secondary windings as reference signals. A three-phase isolation transformer is connected to the secondary side of the three-phase voltage transformer under test (Y-connected). The primary side of the three-phase voltage transformer under test (Y-connected) is connected to the corresponding A, B, and C phase lines of the three-phase test power supply. The primary side of the three-phase isolation transformer is the input terminal, receiving the original line voltages a–b, b–c, and c–a from the three-phase voltage transformer under test (Y-connected). The secondary side is the output terminal, generating three sets of electrically isolated signals. , , ; Three-phase mutual inductor calibrator, used for receiving , , Three sets of reference voltages and , , Three sets of voltages to be calibrated; all terminals synchronously acquire ratio and phase difference data within a single boost cycle.

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