Transformer anti-short-circuit capability evaluation system of electric power system

Abstract

The invention discloses a transformer anti-short-circuit capability evaluation system of a power system, relates to a transformer anti-short-circuit capability evaluation device, and aims to solve the problem of low reliability of an existing method for evaluating the anti-short-circuit capability of a transformer. According to the invention, the short-circuit current calculation module calculates the short-circuit current when various external short circuits occur; the first evaluation result output module obtains a transformer anti-short-circuit capability evaluation result A based on the short-circuit current; the short-circuit electrodynamic force output module establishes a finite element analysis model according to the short-circuit current calculated by the short-circuit current calculation module, and obtains corresponding short-circuit electrodynamic force; the second evaluation result output module is used for carrying out anti-short-circuit capability analysis on the power transformer according to the short-circuit electrodynamic force obtained by the short-circuit electrodynamic force output module to obtain an evaluation result B; and the comprehensive evaluation result output module is used for obtaining a final evaluation result by utilizing a comprehensive evaluation analysis method according to the evaluation result A and the evaluation result B. The method has the advantage that the reliability of short-circuit capability evaluation is improved.

Description

Technical Field

[0001] The invention relates to a transformer short-circuit resistance evaluation device. Background Art

[0002] Transformer is an important equipment in the power system. The stable and reliable operation of transformer plays a very important role in the safe operation of power system. Transformer is a device that changes voltage by the principle of electromagnetic induction. Its main components are primary coil, secondary coil and iron core (magnetic core). Its main functions include voltage conversion, current conversion, impedance conversion, isolation, voltage stabilization (magnetic saturation transformer), etc. It is widely used. Transformer may short-circuit during use, which will cause transformer failure. Transformer is the core of the whole power system. If it fails, it will affect the operation of power grid and bring serious consequences. The existing method of evaluating the short-circuit resistance of transformer is to conduct short-circuit test on transformer. However, the short-circuit test requires high platform, large economic investment and high destructiveness of the test itself to transformer. It is impossible to judge the short-circuit resistance of transformer by conducting short-circuit test on every transformer product, and the reliability of use is low. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of low reliability of the existing method for evaluating the short-circuit resistance capability of a transformer, and proposes a transformer short-circuit resistance capability evaluation system for a power system.

[0004] The present invention provides a transformer short-circuit resistance evaluation system for a power system, the transformer short-circuit resistance evaluation system comprising a short-circuit current calculation module, a first evaluation result output module, a short-circuit electric power output module, a second evaluation result output module and a comprehensive evaluation result output module;

[0005] A short-circuit current calculation module calculates the short-circuit current when various external short circuits occur according to the relevant parameters of the power transformer and the impedance network analysis method;

[0006] The first evaluation result output module compares the short-circuit current calculated by the short-circuit current calculation module with the maximum short-circuit current value allowed by the power transformer to obtain an evaluation result A of the transformer's short-circuit resistance capability based on the short-circuit current;

[0007] The short-circuit electric force output module is used to establish a finite element analysis model according to the short-circuit current calculated by the short-circuit current calculation module to obtain the corresponding short-circuit electric force;

[0008] The second evaluation result output module is used to analyze the short-circuit resistance capability of the power transformer according to the short-circuit electric force obtained by the short-circuit electric force output module to obtain an evaluation result B;

[0009] The comprehensive evaluation result output module is used to obtain the final evaluation result by using a comprehensive evaluation analysis method according to the evaluation result A output by the first evaluation result output module and the evaluation result B output by the second evaluation result output module.

[0010] Furthermore, the various external short circuit types in the short circuit current calculation module include symmetrical short circuit and asymmetrical short circuit.

[0011] Furthermore, the external short circuit types of the symmetrical short circuit include high voltage symmetrical short circuit, medium voltage symmetrical short circuit and low voltage symmetrical short circuit;

[0012] The high voltage symmetrical short circuit is: the high voltage winding of the transformer is symmetrically short-circuited, and the medium and low voltage windings are fed;

[0013] The medium voltage symmetrical short circuit is: the medium voltage winding of the transformer is symmetrically short-circuited, and the high and low voltage side windings are fed;

[0014] The low-voltage symmetrical short circuit means that the low-voltage winding of the transformer is symmetrically short-circuited, and the high and medium voltage side windings are fed.

[0015] Furthermore, the asymmetric short circuit types include single-phase symmetrical short circuit, two-phase symmetrical short circuit, single-phase short circuit to ground and two-phase short circuit to ground;

[0016] The single-phase symmetrical short circuit is: one winding in the transformer is externally symmetrically short-circuited, and the other two windings are fed;

[0017] The two-phase symmetrical short circuit is: two windings in the transformer are simultaneously externally symmetrically short-circuited, and the other winding is fed;

[0018] The single-phase short circuit to ground is: a winding in the transformer is short-circuited to ground externally, and the other two windings are fed;

[0019] The two-phase short circuit to ground is: two windings in the transformer are short-circuited to ground externally, and the other winding is powered. Further, the calculation formula for the comprehensive evaluation result output module 5 to output the final evaluation result is:

[0020] H=A·K+B·(1-K)

[0021] Among them, H is the final evaluation result output by the comprehensive evaluation result output module; A is the evaluation result output by the first evaluation result output module; B is the evaluation result output by the second evaluation result output module; K is the weight coefficient of the evaluation result A output by the first evaluation result output module in the final evaluation result.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention solves the problem of low reliability in the evaluation of the short-circuit resistance of power transformers in the past. Based on the phenomenon of the mechanical detection method of short-circuit electromotive force obtained by empirical formula, an electromagnetic method based on short-circuit current is incorporated into the original method, making the evaluation method more reasonable, effective and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural block diagram of a transformer short-circuit resistance evaluation system for a power system described in a specific implementation method 1. DETAILED DESCRIPTION

[0025] Specific implementation method 1. Combination Figure 1 The present embodiment is described. The present embodiment is a transformer short-circuit resistance evaluation system for a power system. The transformer short-circuit resistance evaluation system comprises a short-circuit current calculation module 1, a first evaluation result output module 2, a short-circuit electric power output module 3, a second evaluation result output module 4 and a comprehensive evaluation result output module 5;

[0026] The short-circuit current calculation module 1 calculates the short-circuit current when various external short circuits occur according to the relevant parameters of the power transformer and the impedance network analysis method;

[0027] The first evaluation result output module 2 compares the short-circuit current calculated by the short-circuit current calculation module 1 with the maximum short-circuit current value allowed by the power transformer to obtain an evaluation result A of the transformer's short-circuit resistance capability based on the short-circuit current;

[0028] The short-circuit electric force output module 3 is used to establish a finite element analysis model according to the short-circuit current calculated by the short-circuit current calculation module 1 to obtain the corresponding short-circuit electric force;

[0029] The second evaluation result output module 4 is used to analyze the short-circuit resistance capability of the power transformer according to the short-circuit electric force obtained by the short-circuit electric force output module 3 to obtain an evaluation result B;

[0030] The comprehensive evaluation result output module 5 is used to obtain the final evaluation result by using a comprehensive evaluation analysis method according to the evaluation result A output by the first evaluation result output module 2 and the evaluation result B output by the second evaluation result output module 4 .

[0031] In this embodiment, the specific process of the short-circuit electric force output module 3 calculating the corresponding short-circuit electric force is: first calculate the magnetic density distribution of the power transformer winding through the finite element analysis model, and then use the magnetic density distribution of the power transformer winding to calculate the corresponding short-circuit electric force; based on the transformer short-circuit current resistance evaluation result, the maximum allowable value of the short-circuit current is divided by the theoretically calculated short-circuit current to obtain the safety factor K0; the safety threshold is calculated according to the safety factor K0; the safety threshold is applied to the comprehensive evaluation result output module 5 of the comprehensive evaluation analysis method.

[0032] Specific implementation method 2: This implementation method further limits the transformer short-circuit resistance capability evaluation system of a power system described in specific implementation method 1. In this implementation method, various external short-circuit types in the short-circuit current calculation module 1 include symmetrical short-circuit types and asymmetrical short-circuit types.

[0033] In this embodiment, the symmetrical short circuit type refers to a fault in a three-phase system when the three-phase voltage and the impedance of the short-circuit point are completely symmetrical. In this case, the current phase angle of each phase is the same and the magnitude is equal; the short-circuit current of the three-phase symmetrical system can be obtained by calculating the symmetrical positive sequence component, and the symmetrical positive sequence current refers to the part of the three-phase current with equal amplitude and the same phase difference. The asymmetrical short circuit type is the fault current generated when the three-phase voltage or the impedance of the short-circuit point is asymmetrical. The asymmetrical fault current includes three components: positive sequence component, negative sequence component and zero sequence component, among which the negative sequence component and the zero sequence component will produce magnetic field rotation, causing various damages and faults.

[0034] Specific implementation method 3: This implementation method further limits the transformer short-circuit resistance evaluation system of a power system described in specific implementation method 2. In this implementation method, the external short-circuit types of the symmetrical short-circuit include high-voltage symmetrical short-circuit, medium-voltage symmetrical short-circuit and low-voltage symmetrical short-circuit;

[0035] The high voltage symmetrical short circuit is: the high voltage winding of the transformer is symmetrically short-circuited, and the medium and low voltage windings are fed;

[0036] The medium voltage symmetrical short circuit is: the medium voltage winding of the transformer is symmetrically short-circuited, and the high and low voltage side windings are fed;

[0037] The low-voltage symmetrical short circuit means that the low-voltage winding of the transformer is symmetrically short-circuited, and the high and medium voltage side windings are fed.

[0038] Specific implementation method 4. This implementation method further limits the transformer short-circuit resistance evaluation system of a power system described in specific implementation method 2. In this implementation method, the asymmetric short circuit types include single-phase symmetrical short circuit, two-phase symmetrical short circuit, single-phase short circuit to ground and two-phase short circuit to ground;

[0039] The single-phase symmetrical short circuit is: one winding in the transformer is externally symmetrically short-circuited, and the other two windings are fed;

[0040] The two-phase symmetrical short circuit is: two windings in the transformer are simultaneously externally symmetrically short-circuited, and the other winding is fed;

[0041] The single-phase short circuit to ground is: a winding in the transformer is short-circuited to ground externally, and the other two windings are fed;

[0042] The two-phase short circuit to ground is: two windings in the transformer are short-circuited to ground externally, and the other winding is powered.

[0043] Specific implementation method 5: This implementation method further limits the transformer short-circuit resistance evaluation system of a power system described in specific implementation method 1. In this implementation method, the calculation formula for outputting the final evaluation result by the comprehensive evaluation result output module 5 is:

[0044] H=A·K+B·(1-K)

[0045] Among them, H is the final evaluation result output by the comprehensive evaluation result output module 5; A is the evaluation result output by the first evaluation result output module 2; B is the evaluation result output by the second evaluation result output module 4; K is the weight coefficient of the evaluation result A output by the first evaluation result output module 2 in the final evaluation result.

[0046] In this embodiment, the weight coefficient K of the evaluation result A output by the first evaluation result output module 2 in the final evaluation result is determined by the short-circuit electric force output by the short-circuit electric force output module 3. When the short-circuit electric force output by the short-circuit electric force output module 3 is less than or equal to the safety threshold, the weight coefficient K is 0.5; if the short-circuit electric force output by the short-circuit electric force output module 3 is greater than the safety threshold, the weight coefficient K is 0.2.

[0047] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A transformer short-circuit resistance evaluation system for a power system, characterized in that: The transformer short-circuit resistance evaluation system comprises a short-circuit current calculation module (1), a first evaluation result output module (2), a short-circuit electric power output module (3), a second evaluation result output module (4) and a comprehensive evaluation result output module (5); A short-circuit current calculation module (1) calculates the short-circuit current when various external short circuits occur according to relevant parameters of the power transformer and an impedance network analysis method; A first evaluation result output module (2) compares the short-circuit current calculated by the short-circuit current calculation module (1) with the maximum short-circuit current value allowed by the power transformer to obtain an evaluation result A of the transformer's short-circuit resistance capability based on the short-circuit current; A short-circuit electric force output module (3) is used to establish a finite element analysis model according to the short-circuit current calculated by the short-circuit current calculation module (1) to obtain the corresponding short-circuit electric force; A second evaluation result output module (4) is used to analyze the short-circuit resistance capability of the power transformer according to the short-circuit electric force obtained by the short-circuit electric force output module (3) to obtain an evaluation result B; The comprehensive evaluation result output module (5) is used to obtain the final evaluation result by using a comprehensive evaluation analysis method according to the evaluation result A output by the first evaluation result output module (2) and the evaluation result B output by the second evaluation result output module (4).

2. The transformer short-circuit resistance evaluation system of a power system according to claim 1, characterized in that: The various external short circuit types in the short circuit current calculation module (1) include a symmetrical short circuit type and an asymmetrical short circuit type.

3. The transformer short-circuit resistance evaluation system of a power system according to claim 2, characterized in that: The external short circuit types of the symmetrical short circuit include high voltage symmetrical short circuit, medium voltage symmetrical short circuit and low voltage symmetrical short circuit; The high voltage symmetrical short circuit is: the high voltage winding of the transformer is symmetrically short-circuited, and the medium and low voltage windings are fed; The medium voltage symmetrical short circuit is: the medium voltage winding of the transformer is symmetrically short-circuited, and the high and low voltage side windings are fed; The low-voltage symmetrical short circuit means that the low-voltage winding of the transformer is symmetrically short-circuited, and the high and medium voltage side windings are fed.

4. The transformer short-circuit resistance evaluation system of a power system according to claim 2, characterized in that: The asymmetric short circuit types include single-phase symmetrical short circuit, two-phase symmetrical short circuit, single-phase short circuit to ground and two-phase short circuit to ground; The single-phase symmetrical short circuit is: one winding in the transformer is externally symmetrically short-circuited, and the other two windings are fed; The two-phase symmetrical short circuit is: two windings in the transformer are simultaneously externally symmetrically short-circuited, and the other winding is fed; The single-phase short circuit to ground is: a winding in the transformer is short-circuited to ground externally, and the other two windings are fed; The two-phase short circuit to ground is: two windings in the transformer are short-circuited to ground externally, and the other winding is powered.

5. The transformer short-circuit resistance evaluation system of a power system according to claim 1, characterized in that: The calculation formula for outputting the final evaluation result by the comprehensive evaluation result output module (5) is: H=A·K+B·(1-K) Among them, H is the final evaluation result output by the comprehensive evaluation result output module (5); A is the evaluation result output by the first evaluation result output module (2); B is the evaluation result output by the second evaluation result output module (4); K is the weight coefficient of the evaluation result A output by the first evaluation result output module (2) in the final evaluation result.

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