Broadband standard voltage transformer for harmonic transformer error measurement

Abstract

The invention relates to the technical field of harmonic transformer metering, in particular to a broadband standard voltage transformer for harmonic transformer error measurement, which comprises a capacitive voltage divider body, a frequency detection unit, a measurement control unit, a compensation unit, a shielding shell and insulating oil, the capacitive voltage divider body, the frequency detection unit, the measurement control unit and the compensation unit are arranged in a shielding shell, and transformer oil is further arranged in the shell. And the influence of impedance change under different frequencies, self capacitance drift under different temperature and humidity and stray capacitance under different voltages on the body capacitance is compensated, so that a wide-frequency-domain high-precision standard device is constructed, and the broadband error verification of the power voltage transformer is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of standard transformers, and in particular to a wide-band standard voltage transformer for measuring harmonic transformer errors. Background Art

[0002] Announcement No. 48 of the State Administration for Market Regulation issued the "Announcement of the State Administration for Market Regulation on the Release of the Catalogue of Measuring Instruments Subject to Mandatory Management", which also clarified that measuring instruments with supervision methods of P (type approval) and P+V (type approval + mandatory verification) should apply for type approval or imported measuring instrument type approval.

[0003] In recent years, my country's new energy has developed rapidly. Under the new power system with new energy grid connection and high power electronic load, the electric energy metering device is very easy to produce measurement errors under the influence of wide-frequency domain harmonics such as multi-frequency domain, time-varying, non-sinusoidal voltage and current signals, which affects the fairness of electric energy trading. Therefore, there is a need for corresponding voltage transformer standard devices to carry out the first inspection and weekly inspection of transformers in accordance with the requirements of relevant national regulations. However, the common electromagnetic standard voltage transformer is only suitable for power frequency measurement, and the power frequency accuracy can reach 0.01 level, but the error changes sharply under high harmonics, and it cannot be used as a standard under high harmonics; the harmonic standard voltage transformer based on the capacitor voltage division principle has good linearity under high harmonics after compensation, and the accuracy can reach 0.2 level, but it is difficult to achieve power frequency above 0.02 level and the stability is poor, so it cannot be used as an error standard under power frequency. To this end, it is necessary to build a wide-band voltage transformer standard device to achieve high-accuracy measurement of harmonics and fast time-varying signals of power voltage transformers in the wide frequency domain (50Hz~2.5kHz), and to improve the adaptability and accuracy of the wide-band voltage transformer standard device to the complex operating environment in the new power system. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention is proposed.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a wide-band standard voltage transformer for harmonic transformer error measurement, comprising a capacitor voltage divider body, a frequency detection unit, a measurement control unit, a compensation unit, a shielded shell and insulating oil; the capacitor voltage divider body, the frequency detection unit, the measurement control unit and the compensation unit are built in the shielded shell, and the shell also includes transformer oil.

[0006] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, the capacitive voltage divider body mainly includes an upper bridge arm capacitor and a lower bridge arm capacitor, and the upper bridge arm capacitor and the lower bridge arm capacitor are connected in series.

[0007] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, the frequency detection unit is a high-precision current transformer with a through-type structure and a zero magnetic flux design, including a primary winding, a secondary winding and an iron core, and the iron core is a ring structure.

[0008] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, the secondary winding is evenly and tightly wound on the annular iron core, and the wire connected to the tail end of the lower bridge wall capacitor of the wide-band standard voltage transformer passes through the annular iron core to form the primary winding of the frequency detection unit.

[0009] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, the frequency detection unit is excited by the primary winding and the secondary winding.

[0010] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, a magnetic shielding structure is also arranged inside the frequency detection unit, which wraps the primary winding, secondary winding and iron core, and the output terminal of the secondary winding is led out from the shielding structure.

[0011] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, a magnetic shielding structure is also arranged inside the frequency detection unit, which wraps the primary winding, secondary winding and iron core, and the output terminal of the secondary winding is led out from the shielding structure.

[0012] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, one end of the measurement control unit is connected to the frequency detection unit, and the other end is connected to the compensation unit.

[0013] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, the compensation unit is composed of a multi-position capacitor and a switching switch.

[0014] As a preferred solution of the wide-band standard voltage transformer for harmonic transformer error measurement described in the present invention, wherein: by measuring the frequency and the impedance of the capacitive voltage divider detected by the control unit, and controlling the switching of the capacitor inside the compensation unit, the capacitive voltage divider ratio is changed to achieve a consistent voltage divider ratio at different frequencies.

[0015] Beneficial effects of the present invention: The present invention adjusts the voltage division ratio by adjusting the capacitance of the lower bridge arm through the measurement voltage frequency adjustment compensation unit, and ensures that the voltage division ratio meets the accuracy requirements at different frequencies, thereby constructing a wide-frequency domain high-precision voltage standard as a comparison standard for wide-frequency domain error verification of power voltage transformers. The voltage transformer based on the electromagnetic principle is composed of an iron core coil, and the accuracy cannot be guaranteed due to the influence of frequency; the capacitive voltage divider has the characteristics of wide measurement frequency and good linearity, but it is difficult to achieve high accuracy due to the influence of temperature and humidity, stray capacitance and frequency. The present invention compensates for the change of impedance at different frequencies, the drift of its own capacitance at different temperatures and humidity, and the influence of stray capacitance on the main capacitance at different voltages by automatically compensating the lower bridge arm of the capacitive voltage divider, thereby constructing a wide-frequency domain high-precision standard to achieve wide-frequency error verification of power voltage transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0017] Figure 1 A schematic diagram of a wide-band standard voltage transformer for wide-band power voltage transformer error calibration provided by an embodiment of the present invention.

[0018] Figure 2 An equivalent circuit diagram of a wide-band standard voltage transformer capacitor for wide-band power voltage transformer error calibration provided by an embodiment of the present invention.

[0019] Figure 3 A schematic diagram of the influence of stray capacitance of a wide-band standard voltage transformer body voltage divider for wide-band power voltage transformer error verification provided by an embodiment of the present invention.

[0020] Figure 4 A schematic diagram of a wide-band standard voltage transformer detection unit for wide-band power voltage transformer error verification provided by an embodiment of the present invention.

[0021] Figure 5 A cross-sectional schematic diagram of a wide-band standard voltage transformer detection unit for wide-band power voltage transformer error verification provided by an embodiment of the present invention.

[0022] Figure 6 A schematic diagram of a wide-band standard voltage transformer compensation unit for wide-band power voltage transformer error calibration provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0026] The embodiment of the present invention provides a wide-band standard voltage transformer for wide-band power voltage transformer error calibration, which can solve the comparison standard problem of harmonic error measurement of existing 6kV to 110kV power voltage transformers for metering, reduces the impact on the standard device environment and operating frequency, is simple to operate, and has strong practicality.

[0027] The invention discloses a wide-frequency standard voltage transformer for wide-frequency domain power voltage transformer error verification, comprising a capacitive voltage divider body, a frequency detection unit, a measurement control unit, a compensation unit, a shielding shell and insulating oil.

[0028] The capacitive voltage divider body, the frequency detection unit, the measurement control unit, and the compensation unit are built into a shielded housing, and the housing also includes transformer oil;

[0029] Furthermore, the capacitor voltage divider body is composed of an upper bridge arm capacitor C1 and a lower bridge arm capacitor C2. The capacitor has the characteristics of low temperature drift and small dielectric factor. It is packaged through a shielding structure and insulated with transformer oil. Because the capacitor of the capacitor voltage divider body has its own characteristics, its capacitive reactance is inversely proportional to the frequency, and the capacitive reactance decreases as the frequency increases; and the capacitor voltage divider capacitance also changes with changes in temperature and humidity, so the present invention adopts a medium with consistent structure and material and is manufactured by the same method to reduce the error caused by inconsistent characteristics of the upper and lower bridge arms; the capacitor body is packaged in an oil-filled sealing structure to avoid the influence of external temperature and humidity on the capacitor as much as possible; the sealing structure adopts shielding material to reduce the influence of external stray capacitance on the capacitor voltage divider body capacitance; and the designed capacitor voltage divider upper bridge arm capacitance can be as large as possible (not less than 1000pF), which has reduced the influence of external stray capacitance on the body capacitance.

[0030] Furthermore, the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 are connected in series, and the voltage division ratio of the capacitive voltage divider body is:

[0031]

[0032] Because of the leakage resistance, equivalent series resistance and equivalent series inductance of the capacitor voltage divider, the capacitance will change with frequency. The impedance expression of the capacitor voltage divider is:

[0033]

[0034] ω=2πf

[0035] Furthermore, the frequency detection unit is a high-precision current transformer with a through-type structure. It is designed based on the zero flux ratio standard principle and is packaged with a shielded structure to reduce the influence of external magnetic fields on its errors. The frequency detection unit is through-type and connected in series in the primary circuit of the capacitor divider. By measuring the primary current, the frequency of the voltage, the impedance of the capacitor divider and other parameters are obtained, thereby providing a strategy for compensation at different frequencies.

[0036] Furthermore, the frequency detection unit includes a primary winding, a secondary winding and an iron core. The iron core is a ring-shaped structure. The secondary winding is evenly and tightly wound on the ring-shaped iron core. The wire connected to the tail end of the lower bridge wall capacitor of the wide-band standard voltage transformer passes through the ring-shaped iron core to form the primary winding of the frequency detection unit; the frequency detection unit realizes the operating frequency and primary current sampling of the wide-band standard voltage transformer through the excitation of the primary winding and the secondary winding.

[0037] A magnetic shielding structure is also provided inside the frequency detection unit, which wraps the primary winding, the secondary winding and the iron core, and the output terminal of the secondary winding is led out from the shielding structure.

[0038] Furthermore, the measurement control unit includes an A / D sampling module, a signal processing module, and an MCU, and has the functions of frequency measurement, primary current measurement, and compensation unit control. One end of the measurement control unit is connected to the frequency detection unit, and the other end is connected to the compensation unit.

[0039] Furthermore, the compensation unit is composed of a multi-position capacitor and a switching switch.

[0040] By measuring the frequency detected by the control unit and the impedance of the capacitor voltage divider, and controlling the switching of the capacitor Cx inside the compensation unit, the transformation ratio K of the capacitor voltage divider is changed to achieve a consistent voltage divider ratio at different frequencies.

[0041]

[0042] See also Figure 1 As shown, the capacitive voltage divider body, the frequency detection unit, the measurement control unit and the compensation unit. Figure 2As shown in the figure, the equivalent circuit diagram of the wide-band standard voltage transformer body capacitor used for wide-band power voltage transformer error verification is used to analyze the frequency characteristics of the capacitor itself, and thus it is proposed that the capacitance voltage divider changes with frequency, causing impedance changes, thereby affecting the change of the voltage divider ratio, resulting in reduced accuracy, providing support for subsequent compensation.

[0043] See also Figure 3 As shown, a schematic diagram of the influence of stray capacitance of the voltage divider of the wide-band standard voltage transformer body used for wide-band power voltage transformer error verification is shown, thereby proposing that the capacitor body is affected by external stray capacitance and affects its own voltage divider ratio, resulting in reduced accuracy, providing support for subsequent compensation.

[0044] See also Figure 4-5 As shown in the figure, the schematic diagram of the wide-band standard voltage transformer detection unit for wide-band power voltage transformer error verification ensures high-precision sampling of the current transformer in principle and structure, thereby ensuring the accuracy of the sampling unit within the wide frequency range, providing support for subsequent accurate calculations. In the figure, A is a core made of high magnetic permeability material, W1 is the primary winding, W2 is the secondary winding, I1 is the primary current, and I2 is the secondary current.

[0045] See also Figure 6 As shown, a schematic diagram of a wide-band standard voltage transformer compensation unit for wide-band power voltage transformer error calibration is shown, which characterizes the compensation principle and control method in principle and provides support for the voltage divider ratio compensation of the capacitor divider.

[0046] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0047] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0048] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A wideband standard voltage transformer for harmonic transformer error measurement, characterized in that: include, Capacitive voltage divider body, frequency detection unit, measurement control unit, compensation unit, shielding shell and insulating oil; The capacitive voltage divider body, the frequency detection unit, the measurement control unit and the compensation unit are built in a shielded shell, and the shell also includes transformer oil.

2. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 1, characterized in that: The capacitive voltage divider body mainly includes an upper bridge arm capacitor and a lower bridge arm capacitor, and the upper bridge arm capacitor and the lower bridge arm capacitor are connected in series.

3. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 2, characterized in that: The frequency detection unit is a high-precision current transformer with a through-type structure and a zero-flux design, and comprises a primary winding, a secondary winding and an iron core, and the iron core is a ring structure.

4. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 3, characterized in that: The secondary winding is evenly and tightly wound on the annular core, and the wire connected to the tail end of the lower bridge wall capacitor of the wide-band standard voltage transformer passes through the annular core to form the primary winding of the frequency detection unit.

5. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 4, characterized in that: The frequency detection unit is excited by the primary winding and the secondary winding.

6. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 5, characterized in that: A magnetic shielding structure is also provided inside the frequency detection unit, and the magnetic shielding structure wraps the primary winding, the secondary winding and the iron core, and the output terminal of the secondary winding is led out from the shielding structure.

7. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 6, characterized in that: A magnetic shielding structure is also provided inside the frequency detection unit, and the magnetic shielding structure wraps the primary winding, the secondary winding and the iron core, and the output terminal of the secondary winding is led out from the shielding structure.

8. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 7, characterized in that: One end of the measurement control unit is connected to the frequency detection unit, and the other end is connected to the compensation unit.

9. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 8, characterized in that: The compensation unit is composed of a multi-position capacitor and a switching switch.

10. The wide-band standard voltage transformer for harmonic transformer error measurement according to claim 9, characterized in that: By measuring the frequency detected by the control unit and the impedance of the capacitor voltage divider, and controlling the switching of the capacitor inside the compensation unit, the transformation ratio of the capacitor voltage divider is changed to achieve a consistent voltage divider ratio at different frequencies.

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