EP4057302A1

EP4057302A1 - Dual-stage magnetic excitation high-voltage proportional standard apparatus and error compensation method

Info

Publication number: EP4057302A1
Application number: EP19951933.1A
Authority: EP
Inventors: Feng Zhou; Hao Liu; Min LEI; Xiaodong YIN; Chunyang JIANG; Jianping Yuan
Original assignee: State Grid Corp of China SGCC; China Electric Power Research Institute Co Ltd CEPRI
Current assignee: State Grid Corp of China SGCC; China Electric Power Research Institute Co Ltd CEPRI
Priority date: 2019-11-05
Filing date: 2019-12-11
Publication date: 2022-09-14
Also published as: CN110993273B; CN110993273A; EP4057302A4; WO2021088200A1

Abstract

Provided are a dual-stage excitation high-voltage ratio standard apparatus and an error compensation method for the apparatus. The apparatus includes a first-stage iron core (C1), a second-stage iron core (C2), a proportional winding (N ₁), a proportional winding (N ₂), an excitation winding (N _1e), and an excitation winding (N _2e), where both the first-stage iron core (C1) and second-stage iron core (C2) are rectangular rings, and a rectangular ring of the first-stage iron core (C1) has a greater perimeter than a rectangular ring of the second-stage iron core (C2); the second-stage iron core (C2) is disposed outside the first-stage iron core (C1), and one side of the first-stage iron core (C1) is adjacent to one side of the second-stage iron core (C2); and the excitation winding (N _1e) and the excitation winding (N _2e) are wound on a side opposite to the side of the first-stage iron core (C1) adjacent to the second-stage iron core (C2), and the proportional winding (N ₁) and the proportional winding (N ₂) are wound on two adjacent sides of the first-stage iron core (C1) and the second-stage iron core (C2). The apparatus solves the problem that a highest voltage level of an existing dual-stage standard apparatus is low, thereby improving the accuracy of a single-stage standard apparatus at a high voltage.

Description

This application claims priority to Chinese Patent Application No. 201911070684.1 filed with the China National Intellectual Property Administration (CNIPA) on Nov. 05, 2019 , the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present application relates to the technical field of electric power measurement standard equipment, for example, a dual-stage excitation high-voltage ratio standard apparatus and additionally relates to an error compensation method for the dual-stage excitation high-voltage ratio standard apparatus.

BACKGROUND

A power frequency voltage ratio standard is a measurement tool and means for reproducing a power frequency voltage ratio and two conditions of stability and traceability need to be satisfied. With the rapid development of the power industry in the past two centuries in the world, the research and application of the power frequency voltage ratio standard have also experienced a long development process. At present, the power frequency voltage ratio standards commonly used in the world mainly include a resistive type, a capacitive type, and an electromagnetic type.
Resistive and capacitive standard apparatuses are greatly affected by temperature and less stable than an electromagnetic standard apparatus. An electromagnetic power frequency voltage ratio standard has the advantages of a simple principle, convenient use, stability, and reliability. In an electromagnetic structure, a dual-stage ratio standard apparatus with high accuracy and good stability is most widely applied.
Since the highest voltage level of a traditional dual-stage ratio standard apparatus is only 10 kV, a low-voltage excitation structure may be used for developing a dual-stage ratio standard apparatus of more than 10 kV. At present, ratio standard apparatuses of 35 kV and 110 kV have been successfully developed. Though the low-voltage excitation structure makes a breakthrough under the voltage level of $110 / \sqrt{3}$
kV, it still has drawbacks. During an error calibration test, if a rated transformation ratio of a ratio standard apparatus is inconsistent with a rated transformation ratio of an instrument transformer under test, it is usually necessary to cascade a multi-decade inductive voltage divider on a secondary side, so as to obtain a consistent transformation ratio.

SUMMARY

The present application provides a dual-stage excitation high-voltage ratio standard apparatus.
The apparatus includes a first-stage iron core C1, a second-stage iron core C2, a proportional winding N ₁, a proportional winding N ₂ , an excitation winding N _1e, and an excitation winding N _2e.
Each of the first-stage iron core C1 and the second-stage iron core C2 is a rectangular ring, and a rectangular ring of the first-stage iron core C1 has a greater perimeter than a rectangular ring of the second-stage iron core C2.
The second-stage iron core C2 is disposed outside the first-stage iron core C1, and a side of the first-stage iron core C1 is adjacent to a side of the second-stage iron core C2.
The excitation winding N _1e and the excitation winding N _2e are wound on sides opposite to the side of the first-stage iron core C1 adjacent to the second-stage iron core C2 to form a first-stage voltage transformer, the proportional winding N ₁ and the proportional winding N ₂ are wound on two adjacent sides of the first-stage iron core C1 and the second-stage iron core C2 to form a second-stage voltage transformer, the excitation winding N _1e and the excitation winding N _2e have the same winding direction, the proportional winding N ₁ and the proportional winding N ₂ have the same winding direction, and the excitation winding (N _1e) and the excitation winding (N _2e) have a winding direction opposite to a winding direction of the proportional winding (N ₁) and the proportional winding (N ₂).
The two adjacent sides of the first-stage iron core C1 and the second-stage iron core C2 have the same magnetic flux direction.
The first-stage iron core (C1) may have a larger cross-sectional area than the second-stage iron core (C2).
The dual-stage excitation high-voltage ratio standard apparatus may further include features described below.
The number of turns of the excitation winding N _1e is equal to the number of turns of the proportional winding N ₁, and the number of turns of the excitation winding N _2e is equal to the number of turns of the proportional winding N ₂.
A material of the first-stage iron core C1 may include silicon steel, and a material of the second-stage iron core C2 may include permalloy.
The present application provides an error compensation method for a dual-stage excitation high-voltage ratio standard apparatus. The method is applied to the dual-stage excitation high-voltage ratio standard apparatus mentioned in the preceding description and includes steps described below.
The number of turns of a proportional winding of a dual-stage excitation high-voltage ratio standard apparatus to be compensated, the number of turns and a transformation ratio of a compensation winding of a compensation low-voltage transformer, a phase-shift angle of a phase-shift circuit, and an angle compensation amount are obtained, and an error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is calculated, where the error compensation amount includes a ratio difference compensation amount and an angular difference compensation amount.
An error of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is compensated for by using the error compensation amount.
After the error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is calculated, the method may further include steps described below.
The compensation low-voltage transformer is used for performing secondary compensation for a capacitive error and a magnetic error of the dual-stage excitation high-voltage ratio standard apparatus to be compensated.
That the error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is calculated may include a step described below.
The ratio difference compensation amount and the angular difference compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated are respectively calculated with the following formulas: ${Δε}_{ƒ} = \frac{N_{4}}{N_{2}} \times \frac{1}{K_{2}} + \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times cosα;$
and ${Δε}_{δ} = β \approx \tan β \approx \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times sinα;$
where Δε_f denotes the ratio difference compensation amount, Δε_δ denotes the angular difference compensation amount, N ₂ denotes the number of turns of the proportional winding of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, N₄ denotes the number of turns of the compensation winding of the compensation low-voltage transformer, K1 and K2 denote transformation ratios of the compensation low-voltage transformer, α denotes the phase-shift angle of the phase-shift circuit, and β denotes the angle compensation amount.
The error compensation method may further include a step described below.
An accuracy level of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is determined with the following formulas; $ε_{1} = - \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1 e}}{Z_{m 1}};$
$ε_{2} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} = - \frac{Z_{1}}{Z_{m 2}};$
and $ε = - \frac{I_{02} Z_{1}}{U_{1}} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} \cdot \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1}}{Z_{m 2}} \cdot \frac{Z_{1 e}}{Z_{m 1}} = - ε_{2} ε_{1};$
where ε ₁ denotes a first-stage error;

ε ₂ denotes a second-stage error;
ε denotes an overall dual-stage error;
I ₀₁-an exciting current of a first-stage voltage transformer;
I ₀₂-an exciting current of a second-stage voltage transformer;
Z _m1-exciting impedance of the first-stage voltage transformer;
Z _m2-exciting impedance of the second-stage voltage transformer;
Z _1e-internal impedance of a primary winding of the first-stage voltage transformer;
Z ₁-internal impedance of a primary winding of the second-stage voltage transformer;
U ₁-a primary voltage of the dual-stage excitation high-voltage ratio standard apparatus; and
$U_{2_{- a}}^{'}$
secondary voltage of the dual-stage excitation high-voltage ratio standard apparatus converted to a primary side.

In the case where the first-stage error is 0.01% to 0.1% and the second-stage error is 0.1 % to 1%, the overall dual-stage error is 10^-7 to 10^-5.
The present application provides the dual-stage excitation high-voltage ratio standard apparatus. Shapes of iron cores and winding manners of proportional windings are changed and in addition, a high-precision error compensation method is adopted so that a voltage level of a dual-stage excitation structure is improved. This apparatus can be used as a power frequency voltage ratio standard instrument of a high accuracy level, which solves the problem that a highest voltage level of a dual-stage ratio standard apparatus is low at present and improves a voltage of the dual-stage ratio standard apparatus, thereby improving the accuracy of a standard ratio apparatus compared with a single-stage ratio standard apparatus at a high voltage.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram of a dual-stage excitation high-voltage ratio standard apparatus according to an embodiment of the present application;
FIG. 2 is a schematic diagram showing a winding direction of a dual-stage excitation high-voltage ratio standard apparatus according to an embodiment of the present application;
FIG. 3 is a circuit diagram showing a principle of a traditional dual-stage voltage transformer involved in an embodiment of the present application;
FIG. 4 is an equivalent circuit diagram of a traditional dual-stage voltage transformer involved in an embodiment of the present application;
FIG. 5 is a structural diagram of a traditional dual-stage voltage transformer involved in an embodiment of the present application;
FIG. 6 is a flowchart of an error compensation method for a dual-stage excitation high-voltage ratio standard apparatus according to an embodiment of the present application;
FIG. 7 is an error compensation circuit diagram of a dual-stage excitation high-voltage ratio standard apparatus involved in an embodiment of the present application; and
FIG. 8 is an error compensation vector diagram of a dual-stage excitation high-voltage ratio standard apparatus involved in an embodiment of the present application.

DETAILED DESCRIPTION

Details are set forth below to facilitate a thorough understanding of the present application. The present application can be implemented in many other manners which are different from this description.
FIG. 1 is a cross-sectional diagram of a dual-stage excitation high-voltage ratio standard apparatus according to an embodiment of the present application. The standard apparatus provided by the present application is described in detail below in conjunction with FIG. 1.
The dual-stage excitation high-voltage ratio standard apparatus includes a first-stage iron core C1, a second-stage iron core C2, a proportional winding N ₁, a proportional winding N ₂, an excitation winding N _1e, and an excitation winding N _2e. Both the first-stage iron core C1 and the second-stage iron core C2 are rectangular rings. As shown in FIG. 1, a rectangular ring of the first-stage iron core C1 has a greater perimeter than a rectangular ring of the second-stage iron core C2. The first-stage iron core C1 has a larger cross-sectional area than the second-stage iron core C2 as viewed from the A-A direction. In an embodiment, a cross section of the first-stage iron core C1 is a circle and a cross section of the second-stage iron core C2 is a rectangle. The second-stage iron core C2 is disposed outside the first-stage iron core C1, and one side of the first-stage iron core C1 is adjacent to one side of the second-stage iron core C2.
The excitation winding N _1e and the excitation winding N _2e are wound on sides opposite to the side of the first-stage iron core C1 adjacent to the second-stage iron core C2 to form a first-stage voltage transformer. The proportional winding N ₁and the proportional winding N ₂ are wound on two adjacent sides of the first-stage iron core C1 and the second-stage iron core C2 to form a second-stage voltage transformer. In FIG. 1, φ ₁ denotes magnetic flux generated by the excitation winding N _1e and the proportional winding N ₁ on the first-stage iron core C1, and φ ₂ denotes magnetic flux generated by the proportional winding N ₁ on the second-stage iron core C2. The number of turns of the excitation winding N _1e is equal to the number of turns of the proportional winding N ₁, and the number of turns of the excitation winding N _2e is equal to the number of turns of the proportional winding N ₂. The excitation winding N _1e and the excitation winding N _2e have the same winding direction, the proportional winding N ₁ and the proportional winding N ₂ have the same winding direction, and two sets of excitation windings and two sets of proportional windings have opposite winding directions, where a winding manner is shown in FIG. 2. In the preceding winding direction, the two adjacent sides of the first-stage iron core C1 and the second-stage iron core C2 have the same magnetic flux direction.
In an embodiment, silicon steel may be used as a material of the first-stage iron core C1, and permalloy may be used as a material of the second-stage iron core C2.
The dual-stage excitation high-voltage ratio standard apparatus provided by the present application is actually a dual-stage voltage transformer. A circuit diagram showing a principle of a traditional dual-stage voltage transformer is shown in FIG. 3. The traditional dual-stage voltage transformer is a specially-structured voltage transformer formed by two stages of voltage transformers. In FIG. 3, an excitation winding N _1e is a primary excitation winding, and the excitation winding N _2e is a secondary power supply winding. The excitation winding N _1e and the excitation winding N _2e are wound on a first-stage iron core C1 to form a first-stage voltage transformer which is equivalent to a general single-stage voltage transformer. A proportional winding N ₁ and a proportional winding N ₂ are wound on the first-stage iron core C1 and the second-stage iron core C2 so that the proportional winding N ₁, the proportional winding N ₂, the first-stage iron core C1, and the second-stage iron core C2 form a second-stage voltage transformer. Thus, the excitation winding N _1e, the excitation winding N _2e, the proportional winding N ₁, the proportional winding N ₂, the first-stage iron core C1, and the second-stage iron core C2 forms the dual-stage voltage transformer, where the number of turns of the excitation winding N _1e is equal to the number of turns of the proportional winding N ₁. An equivalent circuit diagram of the traditional dual-stage voltage transformer shown in FIG. 3 is shown in FIG. 4. $Z_{2}^{'}$
and $U_{2}^{'}$
in FIG. 4 respectively denote secondary impedance and a secondary induced voltage which are converted to a primary side.
A structural diagram of the traditional dual-stage voltage transformer shown in FIG. 3 is shown in FIG. 5, which may be implemented as follows: the excitation winding N _1e is uniformly wound on the first-stage iron core C1, then the second-stage iron core C2 is embedded therein, and finally, the proportional winding N₁ is wound on both the first-stage iron core C1 and the second-stage iron core C2. The reason why a highest voltage level of the traditional dual-stage voltage transformer is only 10 kV at present is as follows: the second-stage iron core C2 is grounded, the excitation winding N _1e is immediately adjacent to the second-stage iron core C2, and the proportional winding N ₁ is wound outside the excitation winding N _1e, and the insulation between the proportional winding N ₁ and the excitation winding N _1e is poor. It is to be noted that the excitation winding N _2e and the proportional winding N ₂ are not shown in FIG. 5.
Compared with the traditional dual-stage voltage transformer, the dual-stage excitation high-voltage ratio standard apparatus (that is, the dual-stage voltage transformer) provided by the present application has the following changes: the first-stage iron core C1 and the second-stage iron core C2 are changed from circular rings to rectangular rings, a relative position of two iron cores is changed, and the excitation winding and the proportional winding are wound respectively, thereby solving the problem of the structure of the traditional dual-stage voltage transformer shown in FIG. 5. In addition, in the dual-stage excitation high-voltage ratio standard apparatus provided by the present application, the excitation winding and the proportional winding have the opposite winding directions so that the two adjacent sides of the first-stage iron core C1 and the second-stage iron core C2 have the same magnetic flux direction.
A dual-stage excitation high-voltage ratio standard apparatus under the voltage level of $500 / \sqrt{3}$
kV is developed according to a structure design method for the dual-stage voltage transformer and a dual-stage excitation principle.
First, the example is used in which silicon steel sheets are used as the material of the first-stage iron core C1. A working magnetic flux density of the iron core at a rated voltage is generally 1.0 T, and various factors need to be considered for selecting an electric potential of a turn selected such as a cross section of the iron core, error performance, and the number of turns of a secondary winding. On the premise that the working magnetic flux density is fixed, the greater the electric potential of the turn is, the larger a cross-sectional area of the iron core needs to be and thus, exciting admittance increases, thereby increasing an error; and conversely, if the electric potential of the turn is too small, more turns are required, and thus, internal impedance of a primary winding becomes high and the error is also increased. This time, primary windings are selected, where N ₁ = N _1e = 150000, and the electric potential of the turn is obtained, where $e_{t} = U_{N} / N_{1} = \frac{500000}{\sqrt{3}} / 150000 = 1.92 (V)$
. The cross-sectional area of the iron core is calculated according to the formula e_t = 4.44 fBSk × 10^-4 , where k denotes a coefficient of iron core laminations and is set to be 0.99, f denotes a frequency and is set to be 50 Hz, and B denotes the working magnetic flux density and is set to be 1.0 T such that the cross-sectional area is calculated, where S=87.36(cm²).

A method for calculating a size of the second-stage iron core is similarly to that of the first-stage iron core, and relevant parameters are as follows:

	First-stage iron core	Second-stage iron core
Iron Core Material	Silicon steel sheet	Permalloy 1J85
Cross-sectional Shape	Circle	Square
Cross-sectional Area	87.36 cm²	9 cm²
Working Magnetic Flux Density	1.0 T	0.3 T

A simple manufacturing process of the dual-stage excitation high-voltage ratio standard apparatus is as follows: first, the excitation winding N _2e and the excitation winding N _1e are wound on the first-stage iron core C1, then the second-stage iron core C2 is disposed on a lower side of the first-stage iron core C1, and the proportional winding N ₂ and the proportional winding N ₁ are wound on the first-stage iron core C1 and the second-stage iron core C2 at the same time.
In a high voltage condition, the error of the dual-stage excitation high-voltage ratio standard apparatus includes three parts which are an excitation error, a capacitive error, and a magnetic error, respectively. The excitation error is solved with the dual-stage excitation principle while secondary compensation may be performed, with the low-voltage transformer, for the capacitive error caused by a leakage current and the magnetic error caused by leakage inductance.
An embodiment of the present application provides an error compensation method for a dual-stage excitation high-voltage ratio standard apparatus. As shown in FIG. 6, the method includes steps described below.
In step S101, an error compensation amount of a dual-stage excitation high-voltage ratio standard apparatus to be compensated is calculated according to the number of turns of a proportional winding of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, the number of turns and a transformation ratio of a compensation winding of a compensation low-voltage transformer, a phase-shift angle of a phase-shift circuit, and an angle compensation amount, where the error compensation amount includes a ratio difference compensation amount and an angular difference compensation amount.
In step S102, an error of the dual-stage excitation high-voltage ratio standard apparatus to be compensated is compensated for by using the error compensation amount.
In an embodiment, the low-voltage transformer is used for performing the secondary compensation for the dual-stage excitation high-voltage ratio standard apparatus. An error compensation circuit diagram is shown in FIG. 7, where P_f is the compensation low-voltage transformer, and N₄ is a compensation winding (the number of turns is generally 1) of the dual-stage voltage transformer P₀. An error compensation vector diagram is shown in FIG. 8.
In FIG. 8, U ₂₁ denotes an output of the proportional winding N ₂ , U ₂ denotes an output voltage after compensation, ΔU_f denotes a ratio difference compensation voltage, ΔU_δ denotes an angular difference compensation voltage, α denotes the phase-shift angle of the phase-shift circuit, and β denotes a final angle compensation amount. $α = \arctan (\frac{1}{ωRC})$
${ΔU}_{ƒ} = U_{21} \times \frac{N_{4}}{N_{2}} \times \frac{1}{K_{2}}$
and ${ΔU}_{δ} = U_{21} \times \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times \cos α$
It can be seen from the error compensation vector diagram that when quadrature component compensation is performed, an in-phase component error is caused. Thus, the ratio difference compensation amount is formed by two parts: the in-phase component itself and the influence caused when the quadrature component compensation is performed. Therefore, the ratio difference compensation amount and the angular difference compensation amount of the dual-stage excitation high-voltage ratio standard apparatus (that is, the dual-stage voltage transformer) to be compensated are respectively calculated with the following formulas: ${Δε}_{ƒ} = \frac{N_{4}}{N_{2}} \times \frac{1}{K_{2}} + \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times cosα$
and ${Δε}_{δ} = β \approx \tan β \approx \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times sinα$
where Δε_f denotes the ratio difference compensation amount, Δε_δ denotes the angular difference compensation amount, N ₂ denotes the number of turns of the proportional winding of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, N₄ denotes the number of turns of the compensation winding of the compensation low-voltage transformer, K1 and K2 denote transformation ratios of the compensation low-voltage transformer, α denotes the phase-shift angle of the phase-shift circuit, and β denotes the angle compensation amount.
Then, the error compensation method for the dual-stage excitation voltage ratio standard apparatus is used for calculating an error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus under the voltage level of $500 / \sqrt{3}$
kV provided by the present application, where relevant parameters are set as follows: N ₂ = 41, N ₄ = 1, R = 100 Ω , C = 10uf, K ₁=200, and K ₂=500.
The preceding parameters are substituted into formulas (4) and (5) so that the following results are obtained after calculation: ${Δε}_{ƒ} = 1.09 \times 10^{- 4};$
and ${Δε}_{δ} = 6 \times 10^{- 5} .$
The dual-stage excitation high-voltage ratio standard apparatus provided by the present application is actually the dual-stage voltage transformer and can be used as a standard apparatus because one accuracy level is improved over a current national highest standard apparatus.
In an embodiment, the accuracy level of the dual-stage excitation voltage ratio standard apparatus to be compensated may be determined with the following formulas: $ε_{1} = - \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1 e}}{Z_{m 1}};$
$ε_{2} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} = - \frac{Z_{1}}{Z_{m 2}};$
and $ε = - \frac{I_{02} Z_{1}}{U_{1}} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} \cdot \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1}}{Z_{m 2}} \cdot \frac{Z_{1 e}}{Z_{m 1}} = - ε_{2} ε_{1};$
where ε ₁ denotes a first-stage error;

ε ₂ denotes a second-stage error;
ε denotes an overall dual-stage error;
I ₀₁-an exciting current of the first-stage voltage transformer;
I ₀₂-an exciting current of the second-stage voltage transformer;
Z _m1-exciting impedance of the first-stage voltage transformer;
Z _m2-exciting impedance of the second-stage voltage transformer;
Z _1e-internal impedance of a primary winding N _1e of the first-stage voltage transformer;
Z ₁-internal impedance of a primary winding N ₁ of the second-stage voltage transformer;
U ₁-a primary voltage of the dual-stage excitation high-voltage ratio standard apparatus; and
$U_{2_{- a}}^{'}$
secondary voltage of the dual-stage excitation high-voltage ratio standard apparatus converted to a primary side.

With the preceding accuracy level determination method, the accuracy level of the dual-stage excitation high-voltage ratio standard apparatus under the voltage level of $500 / \sqrt{3}$
kV provided by the present application is 0.002, which is one class higher than the accuracy level (0.005) of the current national highest standard apparatus under the voltage level of $500 / \sqrt{3}$
kV.
The overall dual-stage error of the dual-stage excitation high-voltage ratio standard apparatus is a negative value of the product of the first-stage error (an error of the first-stage voltage transformer) and the second-stage error (an error of the second-stage voltage transformer). Internal impedance of the second-stage voltage transformer is equivalent to internal impedance of the first-stage voltage transformer. However, since excitation impedance decreases, if the first-stage error is 0.01 % to 0.1%, the second-stage error is 0.1 % to 1%, and then the overall dual-stage error is 10^-7 to 10^-5. Thus, the dual-stage excitation high-voltage ratio standard apparatus can be used as a power frequency voltage ratio standard instrument of a high accuracy level.
The present application provides the dual-stage excitation high-voltage ratio standard apparatus. Shapes of iron cores and winding manners of proportional windings are changed and in addition, a high-precision error compensation method is adopted so that a voltage level of a dual-stage excitation structure is improved. This apparatus can be used as the power frequency voltage ratio standard instrument, which solves the problem that a highest voltage level of a dual-stage ratio standard apparatus is low at present and improves a voltage of the dual-stage ratio standard apparatus, thereby improving the accuracy of a ratio standard apparatus compared with a single-stage ratio standard apparatus at a high voltage.

Claims

A dual-stage excitation high-voltage ratio standard apparatus, comprising:
a first-stage iron core (C1), a second-stage iron core (C2), a proportional winding (N ₁), a proportional winding (N ₂), an excitation winding (N _1e), and an excitation winding (N _2e);

wherein each of the first-stage iron core (C1) and the second-stage iron core (C2) is a rectangular ring, and a rectangular ring of the first-stage iron core (C1) has a greater perimeter than a rectangular ring of the second-stage iron core (C2);

the second-stage iron core (C2) is disposed outside the first-stage iron core (C1), and a side of the first-stage iron core (C1) is adjacent to a side of the second-stage iron core (C2);

the excitation winding (N _1e) and the excitation winding (N _2e) are wound on sides opposite to the side of the first-stage iron core (C1) adjacent to the second-stage iron core (C2) to form a first-stage voltage transformer, the proportional winding (N ₁) and the proportional winding (N ₂) are wound on two adjacent sides of the first-stage iron core (C1) and the second-stage iron core (C2) to form a second-stage voltage transformer, the excitation winding (N _1e) and the excitation winding (N _2e) have a same winding direction, the proportional winding (N ₁) and the proportional winding (N ₂) have a same winding direction, and the excitation winding (N _1e) and the excitation winding (N _2e) have a winding direction opposite to a winding direction of the proportional winding (N ₁) and the proportional winding (N ₂); and

the two adjacent sides of the first-stage iron core (C1) and the second-stage iron core (C2) have a same magnetic flux direction.
The apparatus according to claim 1, wherein the first-stage iron core (C1) has a larger cross-sectional area than the second-stage iron core (C2).
The apparatus according to claim 1 or 2, wherein the apparatus further comprises:
a number of turns of the excitation winding (N _1e) being equal to a number of turns of the proportional winding (N ₁), and a number of turns of the excitation winding (N _2e) being equal to a number of turns of the proportional winding (N ₂).
The apparatus according to any one of claim 1 to 3, wherein a material of the first-stage iron core (C1) comprises silicon steel, and a material of the second-stage iron core (C2) comprises permalloy.
An error compensation method for a dual-stage excitation high-voltage ratio standard apparatus, wherein the method is applied to the dual-stage excitation high-voltage ratio standard apparatus according to any one of claims 1 to 4 and the method comprises:
calculating an error compensation amount of a dual-stage excitation high-voltage ratio standard apparatus to be compensated according to a number of turns of a proportional winding of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, a number of turns and a transformation ratio of a compensation winding of a compensation low-voltage transformer, a phase-shift angle of a phase-shift circuit, and an angle compensation amount, wherein the error compensation amount comprises a ratio difference compensation amount and an angular difference compensation amount; and

compensating, by using the error compensation amount, for an error of the dual-stage excitation high-voltage ratio standard apparatus to be compensated.
The method according to claim 5, wherein after calculating the error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, the method further comprises:
using the compensation low-voltage transformer for performing secondary compensation for a capacitive error and a magnetic error of the dual-stage excitation high-voltage ratio standard apparatus to be compensated.
The method according to claim 5 or 6, wherein calculating the error compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated comprises:
calculating the ratio difference compensation amount and the angular difference compensation amount of the dual-stage excitation high-voltage ratio standard apparatus to be compensated with the following formulas respectively: ${Δε}_{ƒ} = \frac{N_{4}}{N_{2}} \times \frac{1}{K_{2}} + \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times cosα;$
and ${Δε}_{δ} = β \approx \tan β \approx \frac{N_{4}}{N_{2}} \times \frac{1}{K_{1}} \times cosα \times sinα;$

wherein Δε_f denotes the ratio difference compensation amount, Δε_δ denotes the angular difference compensation amount, N ₂ denotes the number of turns of the proportional winding of the dual-stage excitation high-voltage ratio standard apparatus to be compensated, N₄ denotes the number of turns of the compensation winding of the compensation low-voltage transformer, K1 and K2 denote transformation ratios of the compensation low-voltage transformer, α denotes the phase-shift angle of the phase-shift circuit, and β denotes the angle compensation amount.
The method according to any one of claim 5 to 7, further comprising:
determining an accuracy level of the dual-stage excitation high-voltage ratio standard apparatus to be compensated with the following formulas; $ε_{1} = - \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1 e}}{Z_{m 1}};$
$ε_{2} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} = - \frac{Z_{1}}{Z_{m 2}};$
and $ε = - \frac{I_{02} Z_{1}}{U_{1}} = - \frac{I_{02} Z_{1}}{I_{01} Z_{1 e}} \cdot \frac{I_{01} Z_{1 e}}{U_{1}} = - \frac{Z_{1}}{Z_{m 2}} \cdot \frac{Z_{1 e}}{Z_{m 1}} = - ε_{2} ε_{1};$

wherein ε ₁ denotes a first-stage error;
ε ₂ denotes a second-stage error;

ε denotes an overall dual-stage error;

I ₀₁-an exciting current of a first-stage voltage transformer;

I ₀₂-an exciting current of a second-stage voltage transformer;

Z _m1-exciting impedance of the first-stage voltage transformer;

Z _m2-exciting impedance of the second-stage voltage transformer;

Z _1e-internal impedance of a primary winding of the first-stage voltage transformer;

Z ₁-internal impedance of a primary winding of the second-stage voltage transformer;

U ₁-a primary voltage of the dual-stage excitation high-voltage ratio standard apparatus; and

$U_{2_{- a}}^{'}$
-a secondary voltage of the dual-stage excitation high-voltage ratio standard apparatus converted to a primary side.
The method according to claim 8, wherein in a case where the first-stage error is 0.01% to 0.1% and the second-stage error is 0.1 % to 1%, the overall dual-stage error is 10^-7 to 10^-5.