CN107424814A - A kind of high-low pressure composite excitation double-stage voltage transformer and its calibration method - Google Patents

Abstract

The present invention provides a high and low voltage hybrid excitation double-stage voltage transformer and its calibration method. The double-stage voltage transformer includes: a main voltage transformer 1, which includes a first-stage iron core I, a second-stage iron core II, The primary winding W1, the secondary winding W2, the high-voltage excitation winding W3 and the low-voltage excitation winding W4, wherein the low-voltage excitation winding W4 and the high-voltage excitation winding W3 are sequentially wound on the first-stage iron core I, and the first-stage iron core I and the second-stage iron core After the secondary iron core II is stacked, the secondary winding W2 and the primary winding W1 are sequentially wound; the auxiliary voltage transformer 2 is used to excite the main voltage transformer, which includes the iron core, the auxiliary primary winding W5, and the auxiliary secondary winding W5. Winding W6 and power supply winding W7, wherein the auxiliary primary winding W5, auxiliary secondary winding W6 and power supply winding W7 are sequentially wound on the iron core, and the auxiliary primary winding W5 is connected to the primary winding W1 of the main voltage transformer and the high voltage excitation winding W3 , the auxiliary secondary winding W6 is connected to the low voltage excitation winding W4 of the main voltage transformer.

Description

A high and low voltage mixed excitation double-stage voltage transformer and its calibration method

technical field

The invention relates to the technical field of voltage ratio precision measurement, and more specifically, to a high-low voltage hybrid excitation double-stage voltage transformer and a calibration method thereof.

Background technique

The power frequency voltage ratio standard is the key equipment for traceability and transmission of the power frequency voltage value, and an important measurement standard device used to reproduce the power frequency voltage ratio. With the improvement of the accuracy of electric energy measurement, higher requirements are put forward for the accuracy of the transformer. Therefore, it is necessary to study the voltage ratio standard device with high accuracy level and good stability. At present, there are mainly three types of power frequency voltage ratio standards commonly used in the world: resistive, capacitive and electromagnetic. Due to the influence of resistance temperature rise and capacitive leakage current under high voltage, the use of resistive type is limited above 110kV. Capacitive type is limited by voltage level, temperature, proximity effect and structure. As the voltage level increases, its manufacturing difficulty increases significantly, and its accuracy and stability are not as high as the electromagnetic proportional standard. The existing electromagnetic voltage ratio standards generally include single-stage voltage transformers and double-stage voltage transformers, and the latter has a higher level of accuracy in theory.

At present, the double-stage voltage transformer generally adopts a high-voltage excitation or low-voltage excitation structure. First, the excitation coil is wound on the annular auxiliary iron core, and then it is combined with the annular main iron core. Coil, the secondary coil is wound at last, both the excitation coil and the proportional coil are excited by the primary voltage, and the magnetic potential generated by the excitation coil on the auxiliary iron core is used to compensate the magnetic potential of the main iron core, so that the excitation current of the proportional coil is close to zero , so the double-stage voltage transformer has a very small excitation error. However, if the high-voltage excitation method is used, the capacitive leakage will be large due to the existence of high potential. If the low-voltage excitation method is used, the error of the auxiliary voltage transformer will be introduced, which will affect the compensation effect.

Contents of the invention

In order to solve the technical problems in the background technology that there will be capacitive errors when only high-voltage excitation is adopted, and the auxiliary voltage transformer will be crossed when only low-voltage excitation is adopted, the present invention provides a high-low voltage hybrid excitation double-stage voltage transformer and its calibration method. Wherein, the double-stage voltage transformer includes:

The main voltage transformer 1 includes a first-level iron core I, a second-level iron core II, a primary winding W1, a secondary winding W2, a high-voltage excitation winding W3 and a low-voltage excitation winding W4, wherein the low-voltage excitation winding W4 and the high-voltage excitation winding The winding W3 is wound on the first-level iron core I in turn, and the first-level iron core I and the second-level iron core II are wound with the low-voltage excitation winding W4 and the high-voltage excitation winding W3, and then the secondary winding W2 is wound in turn. and primary winding W1;

Auxiliary voltage transformer 2, which is a unipolar voltage transformer, is used to excite the main voltage transformer, which includes an iron core, an auxiliary primary winding W5, an auxiliary secondary winding W6 and a power supply winding W7, wherein the auxiliary primary winding W5 , auxiliary secondary winding W6 and power supply winding W7 are sequentially wound on the iron core, and the auxiliary primary winding W5 is connected with the primary winding W1 of the main voltage transformer and the high-voltage excitation winding W3, and the auxiliary secondary winding W6 is connected with the low-voltage excitation of the main voltage transformer Winding W4 is connected.

Preferably, the first-level iron core I and the second-level iron core II of the main voltage transformer are annular iron cores, and the diameter of the second-level iron core II is larger than the first-level iron core I, and the second-level iron core II The center of the circle coincides when the core II and the first-level iron core I are stacked.

Preferably, the second-stage iron core II of the main voltage transformer is four rings, which are installed on the inner, outer, upper, and lower sides of the first-stage iron core I wound with the low-voltage excitation winding W4 and the high-voltage excitation winding W3 respectively, Wherein the ring on the upper side and the first-stage iron core I wound with the low-voltage field winding W4 and the high-voltage field winding W3 are padded with insulating materials to prevent the formation of short-circuit turns.

Preferably, the number of turns of the high voltage excitation winding W3 is equal to that of the primary winding W1 and the auxiliary primary winding W5, and the number of turns of the low voltage excitation winding W4 is equal to that of the auxiliary secondary winding W6.

Preferably, copper foil is covered between the high-voltage excitation winding W3 and the low-voltage excitation winding W4 and between the secondary winding W2 and the primary winding W1, and the copper foil is grounded through welding lead wires.

According to another aspect of the present invention, the present invention provides a method for calibrating the dual-stage voltage transformer of the present invention, the method comprising:

Use the inductive voltage divider T ₀ as the standard voltage transformer, and connect the inductive voltage divider T ₀ , the double-stage voltage transformer T _X to be tested and the calibrator;

Adjust the reading plate of the calibrator to make the zero indicator point to zero;

Turn on the power supply and measure the error of the two-stage voltage transformer T _X to be tested relative to the inductive voltage divider T ₀ , then the error of the two-stage voltage transformer T _X to be tested is, where ε ₀ is the error of the inductive voltage divider T ₀ .

Preferably, when the dual-stage voltage transformer to be tested is the low-accuracy dual-stage voltage transformer described in the present invention, the inductive voltage divider can replace the high-accuracy dual-stage voltage transformer described in the present invention device.

Compared with the prior art, the technical solution provided by the present invention adopts the high and low voltage mixed excitation structure, thereby reducing the capacitive error caused by the capacitive leakage current through electrostatic shielding, and the auxiliary iron core structure shields the miscellaneous The influence of the stray magnetic field and the leakage magnetic field reduces the magnetic error, eliminates the error introduced by the auxiliary voltage transformer, and improves the accuracy level of the double-stage voltage transformer.

Description of drawings

A more complete understanding of the exemplary embodiments of the present invention can be had by referring to the following drawings:

Fig. 1 is the schematic diagram of the high and low voltage mixed excitation two-stage voltage transformer of the specific embodiment of the present invention;

Fig. 2 is a sectional structure diagram of the main voltage transformer of a high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to a specific embodiment of the present invention;

Fig. 3 is a cross-sectional structure diagram of an auxiliary voltage transformer of a high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to a specific embodiment of the present invention;

Fig. 4 is a cross-sectional structure diagram of the main voltage transformer of another high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to a specific embodiment of the present invention;

Fig. 5 is the flow chart of the method for calibrating the high and low voltage hybrid excitation dual-stage voltage transformer of the present invention with an inductive voltage divider according to a specific embodiment of the present invention;

Fig. 6 is a circuit diagram for calibrating the high-voltage and low-voltage hybrid excitation double-stage voltage transformer of the present invention with an inductive voltage divider according to a specific embodiment of the present invention.

detailed description

Exemplary embodiments of the present invention will now be described with reference to the drawings; however, the present invention may be embodied in many different forms and are not limited to the embodiments described herein, which are provided for the purpose of exhaustively and completely disclosing the present invention. invention and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings do not limit the present invention. In the figures, the same units/elements are given the same reference numerals.

Unless otherwise specified, the terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it can be understood that terms defined by commonly used dictionaries should be understood to have consistent meanings in the context of their related fields, and should not be understood as idealized or overly formal meanings.

Fig. 1 is a schematic diagram of a high-voltage and low-voltage hybrid excitation dual-stage voltage transformer according to a specific embodiment of the present invention. As shown in Figure 1, the two-stage voltage transformer includes a main voltage transformer 1 and an auxiliary voltage transformer 2, wherein:

The main voltage transformer 1 includes a first-level iron core I, a second-level iron core II, a primary winding W1, a secondary winding W2, a high-voltage excitation winding W3 and a low-voltage excitation winding W4.

Fig. 2 is a cross-sectional structure diagram of a main voltage transformer of a high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to a specific embodiment of the present invention. As shown in Figure 2, the low-voltage excitation winding W4 and the high-voltage excitation winding W3 are wound on the first-stage iron core I in sequence, and the first-stage iron core I and the second-stage iron core I are wound with the low-voltage excitation winding W4 and the high-voltage excitation winding W3. After the iron core II is stacked, the secondary winding W2 and the primary winding W1 are sequentially wound. The second-stage iron core II shown in Figure 2 is an ordinary annular iron core. As an excitation core, the shielding effect is average, but it can reduce the volume of the double-stage voltage transformer.

Preferably, copper foil 3 is covered between the high-voltage excitation winding W3 and the low-voltage excitation winding W4 and between the secondary winding W2 and the primary winding W1, and the copper foil 3 is grounded by welding the lead wire to reduce the capacitive leakage between the windings .

The auxiliary voltage transformer 2, which is a unipolar voltage transformer, is used to excite the main voltage transformer, and includes an iron core, an auxiliary primary winding W5, an auxiliary secondary winding W6 and a power supply winding W7. Fig. 3 is a cross-sectional structure diagram of the auxiliary voltage transformer of the high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to the specific embodiment of the present invention. As shown in FIG. 3 , the auxiliary primary winding W5 , the auxiliary secondary winding W6 and the power supply winding W7 are sequentially wound on the iron core.

In addition, the auxiliary primary winding W5 of the auxiliary voltage transformer 2 is connected to the primary winding W1 of the main voltage transformer and the high voltage excitation winding W3, and the auxiliary secondary winding W6 is connected to the low voltage excitation winding W4 of the main voltage transformer.

The main voltage transformer of the present invention is wound with high-voltage excitation and low-voltage excitation windings at the same time, and is connected with the auxiliary voltage transformer, which is equivalent to the first-level transformer of the main voltage transformer and the primary winding and secondary winding of the auxiliary voltage transformer. The windings are connected in parallel. For the main voltage transformer, the first-level transformer composed of high-voltage excitation winding, low-voltage excitation winding and first-level iron core I has:

U ₁ ＝-E ₃ +I ₃ Z ₃ ＝-E' ₄ +I ₃ Z ₃ (1)

In the formula, U ₁ is the primary voltage, E ₃ is the induced potential of the high-voltage excitation winding, E' ₄ is the induced potential of the low-voltage excitation winding converted to the primary side, I ₃ is the current in the high-voltage excitation winding, and Z ₃ is the internal impedance of the high-voltage excitation winding .

When the auxiliary voltage transformer is not considered, the first-stage transformer is equivalent to no load without load, E' ₄ = U' ₄ , and U' ₄ is the voltage converted from the output of the low-voltage excitation winding to the primary side.

For auxiliary voltage transformers, there are

U ₁ ＝-E ₅ +I ₅ Z ₅ ＝-E' ₆ +I ₅ Z ₅ (2)

In the formula, _E5 is the induced potential of the auxiliary primary winding, _E'6 is the induced potential of the auxiliary secondary winding converted to the primary side, _I5 is the current in the auxiliary primary winding, and _Z5 is the internal impedance of the auxiliary primary winding.

When the auxiliary voltage transformer is not considered, the first-stage transformer is equivalent to no load and no load, E' ₆ = U' ₆ , and U' ₆ is the voltage converted from the output of the auxiliary secondary winding to the primary side.

Since the number of turns of high-voltage excitation winding W3 and auxiliary primary winding W5 are equal, and other parameters such as iron core materials are also the same, the internal resistance and excitation impedance of the primary winding of the first-stage transformer and auxiliary transformer are the same, then E' ₄ =E ' ₆ deduces U' ₄ = U' ₆ . In the loop formed by the low-voltage excitation winding W4 and the auxiliary secondary winding W6, the current is zero, and I ₄ =0. In this way, the error of the auxiliary transformer is eliminated, namely:

ε ₁ = ε ₃ + ε ₅ = ε ₃ (3)

In the formula, ε1 is the error _of the _first stage transformer, ε3 is the no-load error of the first stage transformer, and _ε5 is the error of the auxiliary transformer.

The second-level voltage transformer composed of the primary winding W1, the secondary winding W2 and the second-level iron core II is excited by the primary voltage drop of the first-level iron core, then:

ε＝ε ₁ ε ₂ ＝ε ₃ ε ₂ (4)

In the formula, ε ₂ is the error of the second stage voltage transformer. Compared with the low-voltage excitation double-stage voltage transformer error (ε ₃ +ε ₅ ), ε ₂ reduces the influence of ε ₅ .

Preferably, the first-level iron core I and the second-level iron core II of the main voltage transformer 1 are annular iron cores, and the diameter of the second-level iron core II is larger than the first-level iron core I, and the second-level iron core II The centers of the circles coincide when the iron core II and the first-level iron core I are stacked.

Fig. 4 is a cross-sectional structure diagram of the main voltage transformer of another high-voltage and low-voltage hybrid excitation double-stage voltage transformer according to a specific embodiment of the present invention. As shown in Figure 4, the second-stage iron core II of the main voltage transformer 1 includes a concave annular groove in section and an annular cover plate arranged at the opening of the annular groove, and an annular cover plate and an annular groove are provided between the annular cover plate and the annular groove There is an insulating liner 4, which prevents the formation of short-circuit turns. The second-stage iron core II is not only an excitation core but also a magnetic shield, which can enhance the shielding effect and reduce magnetic errors.

Preferably, the number of turns of the high voltage excitation winding W3 is equal to that of the primary winding W1 and the auxiliary primary winding W5, and the number of turns of the low voltage excitation winding W4 is equal to that of the auxiliary secondary winding W6.

Fig. 5 is a flow chart of the method for calibrating the high-voltage and low-voltage hybrid excitation double-stage voltage transformer of the present invention by using an inductive voltage divider according to a specific embodiment of the present invention. As shown in FIG. 5 , the method for calibrating the high-voltage and low-voltage hybrid excitation double-stage voltage transformer of the present invention by using an inductive voltage divider begins at step 501 .

In step 501, the inductive voltage divider T ₀ is used as a standard voltage transformer, and the inductive voltage divider T ₀ , the dual-stage voltage transformer T _X to be tested and the calibrator are connected.

Fig. 6 is a circuit diagram for calibrating the high-voltage and low-voltage hybrid excitation double-stage voltage transformer of the present invention with an inductive voltage divider according to a specific embodiment of the present invention. As shown in Figure 6, the polar terminals of W30 and W10 are connected and connected to the power supply; the non-polar terminals of W30, W10 and W2 are connected and connected to the power supply; W3 is connected to the polar end of W5 and connected to the power supply; W1, W3 is connected to the non-polar end of W5 and connected to the power supply; W4 is connected to the polar end of W6; the non-polar end is connected to the ground; W7 is connected to calibrator a and x. Calibrator D is grounded.

In step 502, adjust the reading plate of the calibrator to make the zero indicator point to zero;

In step 503, turn on the power supply, and measure the error of the double-stage voltage transformer T _X to be tested relative to the inductive voltage divider T ₀ , then the error of the two-stage voltage transformer T _X to be tested is, where ε ₀ is the inductive voltage divider T0 error.

Preferably, when the dual-stage voltage transformer to be tested is the low-accuracy dual-stage voltage transformer described in the present invention, the inductive voltage divider can replace the high-accuracy dual-stage voltage transformer described in the present invention device.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a/the/the [means, component, etc.]" are to be construed openly as at least one instance of said means, component, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Claims (7)

1. A high and low voltage hybrid excitation double-stage voltage transformer, characterized in that, said double-stage voltage transformer comprises: The main voltage transformer 1 includes a first-level iron core I, a second-level iron core II, a primary winding W1, a secondary winding W2, a high-voltage excitation winding W3 and a low-voltage excitation winding W4, wherein the low-voltage excitation winding W4 and the high-voltage excitation winding The winding W3 is wound on the first-level iron core I in turn, and the first-level iron core I and the second-level iron core II are wound with the low-voltage excitation winding W4 and the high-voltage excitation winding W3, and then the secondary winding W2 is wound in turn. and primary winding W1; Auxiliary voltage transformer 2, which is a unipolar voltage transformer, is used to excite the main voltage transformer, which includes an iron core, an auxiliary primary winding W5, an auxiliary secondary winding W6 and a power supply winding W7, wherein the auxiliary primary winding W5 , auxiliary secondary winding W6 and power supply winding W7 are sequentially wound on the iron core, and the auxiliary primary winding W5 is connected with the primary winding W1 of the main voltage transformer and the high-voltage excitation winding W3, and the auxiliary secondary winding W6 is connected with the low-voltage excitation of the main voltage transformer Winding W4 is connected. 2. The double-stage voltage transformer according to claim 1, characterized in that, the first-stage iron core I and the second-stage iron core II of the main voltage transformer are annular iron cores, and the second-stage iron core The diameter of the core II is larger than that of the first-level iron core I, and when the second-level iron core II and the first-level iron core I are stacked, the centers of the circles coincide. 3. The double-stage voltage transformer according to claim 1, characterized in that, the second-stage iron core II of the main voltage transformer is four circular rings, which are respectively installed on the low-voltage excitation winding W4 and the high-voltage The first-stage iron core I of the field winding W3 has an inner, an upper, a lower, and four sides, wherein the upper ring and the first-stage iron core I wound with the low-voltage field winding W4 and the high-voltage field winding W3 are padded with insulating materials to prevent the formation of short-circuit turns. . 4. The double-stage voltage transformer according to claim 1, characterized in that, the number of turns of the high-voltage excitation winding W3 is equal to the number of turns of the primary winding W1 and the auxiliary primary winding W5, and the low-voltage excitation winding W4 is connected to the auxiliary secondary winding. The number of turns of winding W6 is equal. 5. The double-stage voltage transformer according to claim 1, characterized in that, copper foil is coated between the high-voltage excitation winding W3 and the low-voltage excitation winding W4 and between the secondary winding W2 and the primary winding W1, and the copper foil passes through Solder lead wire to ground. 6. A method for calibrating any two-stage voltage transformer in claims 1 to 5, characterized in that the method comprises: Use the inductive voltage divider T ₀ as the standard voltage transformer, and connect the inductive voltage divider T ₀ , the double-stage voltage transformer T _X to be tested and the calibrator; Adjust the reading plate of the calibrator to make the zero indicator point to zero; Turn on the power and measure the error ε of the two-stage voltage transformer T _X to be tested relative to the induction voltage divider T ₀ , then the error of the two-stage voltage transformer T _X to be tested is ε _X =ε+ε _O , where is the induction divider Compressor T ₀ error. 7. The method according to claim 6, wherein when the dual-stage voltage transformer to be tested is a dual-stage voltage transformer of any low accuracy level in claims 1 to 5, the inductive voltage divider It can be replaced by any high-accuracy dual-stage voltage transformer in claims 1 to 5.