Method for calculating capacity of transformer based on external characteristics

Abstract

The invention relates to a method for calculating the capacity of a transformer based on external characteristics, and the method comprises the following steps: selecting a transformer adjacent to a user or a transformer area as a reference transformer, and obtaining the measurement data of a to-be-judged transformer and the reference transformer, including voltage and current data; deducing high-voltage side data of the to-be-judged transformer and the reference transformer according to the types and the measurement data of the to-be-judged transformer and the reference transformer; constructing an evaluation function according to the corresponding relation between the capacity and the impedance of the transformer and an external characteristic principle; and judging the capacity of the transformer according to the impedance value under the extreme value condition of the evaluation function.

Description

Technical Field

[0001] The present application relates to the technical field of electric energy metering and collection, and more specifically, to a method for calculating transformer capacity based on external characteristics. Background Art

[0002] In the current power system, the judgment of transformer capacity is a vital task. The existing judgment methods have many obvious defects and shortcomings. First, the transformer needs to be shut down to obtain the data required for calculation, which will have a serious impact on the power supply quality in the operating area. In the context of increasingly high requirements for power supply stability and reliability in modern society, this power outage caused by detection is extremely unfavorable and seriously violates the requirements of building a modern excellent power supply service system. Secondly, due to the large number of transformers, the existing method that requires manual verification will consume a lot of manpower and time. The staff needs to operate and process the transformers one by one, which is not only inefficient, but also almost impossible to conduct a comprehensive investigation when facing such a large number of transformers. This situation brings many problems in practical applications, such as inaccurate judgment of the capacity of some transformers, which in turn affects the operation and planning of the entire power system. In addition, the existing methods may also cause errors due to human factors, further reducing the accuracy and reliability of the judgment.

[0003] Prior art, such as the Chinese patent number "CN108303606B", discloses an online evaluation method for the capacity of a distribution transformer. The method uses a correlation coefficient method to realize automatic identification of the connection group of the distribution transformer; then calculates the short-circuit impedance of the Dyn11 distribution transformer and the zero-sequence impedance of the Yyn0 distribution transformer, and compares them with the standard reference value; and finally obtains the evaluation capacity of the distribution transformer. The present invention uses the correlation coefficient method based on the operating voltage data of the distribution transformer to realize the self-identification of the connection group of the distribution transformer; the present invention can accurately evaluate the rated capacity of the distribution transformer through the Dyn11 distribution transformer capacity online evaluation method when the primary side electrical quantity of the distribution transformer cannot be obtained; the present invention takes into account the case where the neutral point of the Yyn0 distribution transformer will be offset, and the rated capacity of the distribution transformer can be accurately evaluated through the Yyn0 distribution transformer capacity online evaluation method.

[0004] The problem with the above-mentioned prior art is that the method is highly dependent on the operating data of the secondary side of the distribution transformer. If these data are erroneous, missing or inaccurate, the accuracy of the evaluation results may be affected. Therefore, in actual application, the method may require the installation of additional monitoring equipment to obtain secondary side operating data, which increases the cost and complexity of the system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for calculating transformer capacity based on external characteristics.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a method for calculating transformer capacity based on external characteristics, comprising the following steps:

[0008] Step S1: Select a transformer near a user or a transformer area as a reference transformer, and obtain measurement data of the transformer to be judged and the reference transformer, including voltage and current data;

[0009] Step S2: deriving high-voltage side data of the transformer to be determined and the reference transformer according to the types and measurement data of the transformer to be determined and the reference transformer;

[0010] Step S3: constructing an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle;

[0011] Step S4: judging the capacity of the transformer according to the impedance value when the evaluation function takes an extreme value.

[0012] As a preferred implementation, the high-voltage side data of the transformer to be determined and the reference transformer are derived according to the types and measurement data of the transformer to be determined and the reference transformer, and the specific steps are as follows:

[0013] For a special transformer with a metering device installed on the low-voltage side of the transformer, the collected measurement values ​​on the low-voltage side of the transformer are converted into the voltage on the high-voltage side of the transformer based on the transformer equivalent circuit;

[0014] The specific steps include:

[0015] The voltage on the low voltage side of the transformer is set to E a 、E b 、E c , based on the transformer equivalent circuit, the three-phase equivalent circuit of the high-supply and low-meter dedicated transformer user is obtained;

[0016] Assume E a ′、E b ′、E c ′ is the voltage amplitude after the offset correction caused by impedance, β1, β2, β3 are the voltage angles after the correction caused by impedance, θ a ,θ b ,θ c is the phase shift, then:

[0017]

[0018] β1=α1+θ a -θ b

[0019] β2=α2+θ b -θ c

[0020] β3=α3+θ c -θ a

[0021] Where: U a , U b , U c is the three-phase voltage at the metering point; I a ,I b ,I c is the three-phase current at the metering point; α1, α2, α3 are the three-phase voltage angles at the metering point; is the three-phase current angle at the metering point; R t , X t is the transformer impedance, obtained by the transformer model and capacity;

[0022] Assume that the high voltage line voltage is E L1 、E L2 、E L3 , according to the triangle cosine theorem, we have:

[0023] E L1 2 =E a ' 2 +E b ' 2 -2E a ′E b ′cosβ1

[0024] E L2 2 =E b ' 2 +E c ' 2 -2E b ′E c ′cosβ2

[0025] E L3 2 =E c ' 2 +E a ' 2 -2E c ′E a ′cosβ3

[0026] Usually the high voltage line is set up with three-phase balance, then E a 、E b 、E c The angle between them is 120°. According to the cosine theorem, we have:

[0027] E L1 2 =E a 2 +E b 2 +E a E b

[0028] E L2 2 =E b 2 +E c 2 +E b E c

[0029] E L3 2 =E c 2 +E a 2 +E c E a

[0030] Through the above steps, the voltage value of the high voltage side is obtained based on the measured value of the low voltage side of the transformer;

[0031] For a special transformer with a metering device installed on the high-voltage side of the transformer, the B-phase line voltage is calculated according to the cosine theorem based on the collected A-phase line voltage, C-phase line voltage and line voltage angle on the high-voltage side of the transformer; the specific formula is:

[0032] E L3 2 =E L1 2 +E L2 2 -2E L1 E L2 cosδ3

[0033] Where δ3 is the line voltage angle between phase A and phase C.

[0034] As a preferred implementation, an evaluation function is constructed based on the corresponding relationship between transformer capacity and impedance and the external characteristic principle. The specific formula of the evaluation function is as follows:

[0035] Assume that the three-phase voltage on the high-voltage side of the transformer to be judged after the transformation is E1, E2, and E3; the three-phase voltage on the high-voltage side of the reference transformer is E ref1 、E ref2 、E ref3 ; The evaluation function is:

[0036] F p (Rt,Xt)=[E1-k r E ref1] 2 +[E2-k r E ref2 ] 2 +[E3-k r E ref3 ] 2 (p=1…24)

[0037] Among them, k r is the reference coefficient of the ratio of the high voltage side voltage of the transformer to be judged to that of the reference transformer; since there are two wiring groups of transformers, Dyn11 and Yyn0, E1, E2, E3, E ref1 、E ref2 、E ref3 It is phase voltage or line voltage, which is determined according to the wiring group type; there are 6 situations according to the wiring phase: ABC, BCA, CAB, ACB, BAC, CBA, determine E1, E2, E3, E ref1 、E ref2 、E ref3 There are 24 values ​​of , p = 1, 2, 3, ..., 24, corresponding to 24 values ​​respectively.

[0038] As a preferred implementation, the capacity of the transformer is judged according to the impedance value when the evaluation function takes an extreme value, and the specific calculation formula is as follows:

[0039] F(Rt,Xt)=min[F1(Rt,Xt),F2(Rt,Xt)…,F 24 (Rt,Xt)]

[0040] Known F(R t ,X t ), when R t , X t When a certain combination is satisfied, F(R t ,X t ) is the smallest; the capacity within this corresponding relationship is the required transformer capacity.

[0041] On the other hand, the present invention also provides a system for calculating transformer capacity based on external characteristics, comprising:

[0042] Data acquisition module: selects the transformer of the neighboring user or substation as the reference transformer, and obtains the measurement data of the transformer to be judged and the reference transformer, including voltage and current data;

[0043] Voltage derivation module: derives the high-voltage side data of the transformer to be judged and the reference transformer according to the types and measurement data of the transformer to be judged and the reference transformer;

[0044] Impedance combination evaluation module: constructs an evaluation function based on the corresponding relationship between transformer capacity and impedance and the principle of external characteristics;

[0045] Capacity determination module: Determine the capacity of the transformer based on the impedance value when the evaluation function takes the extreme value.

[0046] As a preferred implementation, the voltage derivation module derives the high-voltage side data of the transformer to be determined and the reference transformer according to the types and measurement data of the transformer to be determined and the reference transformer, and the specific steps are as follows:

[0047] For a special transformer with a metering device installed on the low-voltage side of the transformer, the collected measurement values ​​on the low-voltage side of the transformer are converted into the voltage on the high-voltage side of the transformer based on the transformer equivalent circuit;

[0048] The specific steps include:

[0049] The voltage on the low voltage side of the transformer is set to E a 、E b 、E c , based on the transformer equivalent circuit, the three-phase equivalent circuit of the high-supply and low-meter dedicated transformer user is obtained;

[0050] Assume E a ′、E b ′、E c ′ is the voltage amplitude after the offset correction caused by impedance, β1, β2, β3 are the voltage angles after the correction caused by impedance, θ a ,θ b ,θ c is the phase shift, then:

[0051]

[0052] β1=α1+θ a -θ b

[0053] β2=α2+θ b -θ c

[0054] β3=α3+θ c -θ a

[0055] Where: U a , U b , U c is the three-phase voltage at the metering point; I a ,I b ,I c is the three-phase current at the metering point; α1, α2, α3 are the three-phase voltage angles at the metering point; is the three-phase current angle at the metering point; R t , X t is the transformer impedance, obtained by the transformer model and capacity;

[0056] Assume that the high voltage line voltage is E L1 、E L2 、E L3 , according to the triangle cosine theorem, we have:

[0057] E L1 2 =E a ' 2 +E b ' 2 -2E a ′E b ′cosβ1

[0058] E L2 2 =E b ' 2 +E c ' 2 -2E b ′E c ′cosβ2

[0059] E L3 2 =E c ' 2 +E a ' 2 -2E c ′E a ′cosβ3

[0060] Usually the high voltage line is set up with three-phase balance, then E a 、E b 、E c The angle between them is 120°. According to the cosine theorem, we have:

[0061] E L1 2 =E a 2 +E b 2 +E a E b

[0062] E L2 2 =E b 2 +E c 2 +E b E c

[0063] E L3 2 =E c 2 +Ea 2 +E c E a

[0064] Through the above steps, the voltage value of the high voltage side is obtained based on the measured value of the low voltage side of the transformer;

[0065] For a special transformer with a metering device installed on the high-voltage side of the transformer, the B-phase line voltage is calculated according to the cosine theorem based on the collected A-phase line voltage, C-phase line voltage and line voltage angle on the high-voltage side of the transformer; the specific formula is:

[0066] E L3 2 =E L1 2 +E L2 2 -2E L1 E L2 cosδ3

[0067] Where δ3 is the line voltage angle between phase A and phase C.

[0068] As a preferred implementation, the impedance combination evaluation module constructs an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle. The specific formula of the evaluation function is as follows:

[0069] Assume that the three-phase voltage on the high-voltage side of the transformer to be judged after the transformation is E1, E2, and E3; the three-phase voltage on the high-voltage side of the reference transformer is E ref1 、E ref2 、E ref3 ; The evaluation function is:

[0070] F p (Rt,Xt)=[E1-k r E ref1 ] 2 +[E2-k r E ref2 ] 2 +[E3-k r E ref3 ] 2 (p=1…24)

[0071] Among them, k r is the reference coefficient of the ratio of the high voltage side voltage of the transformer to be judged to that of the reference transformer; since there are two wiring groups of transformers, Dyn11 and Yyn0, E1, E2, E3, E ref1 、E ref2 、E ref3It is phase voltage or line voltage, which is determined according to the wiring group type; there are 6 situations according to the wiring phase: ABC, BCA, CAB, ACB, BAC, CBA, determine E1, E2, E3, E ref1 、E ref2 、E ref3 There are 24 values ​​of , p = 1, 2, 3, ..., 24, corresponding to 24 values ​​respectively.

[0072] As a preferred implementation, the capacity determination module determines the capacity of the transformer according to the impedance value when the evaluation function takes an extreme value. The specific calculation formula is as follows:

[0073] F(Rt,Xt)=min[F1(Rt,Xt),F2(Rt,Xt)…,F 24 (Rt,Xt)]

[0074] Known F(R t ,X t ), when R t , X t When a certain combination is satisfied, F(R t ,X t ) is the smallest; the capacity within this corresponding relationship is the required transformer capacity.

[0075] On the other hand, the present invention further provides an electronic device having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for calculating transformer capacity based on external characteristics as described in any embodiment of the present invention is implemented.

[0076] On the other hand, the present invention also provides a computer-readable medium for storing one or more programs, which, when executed by the one or more processors, enables the one or more processors to implement a method for calculating transformer capacity based on external characteristics as described in any embodiment of the present invention.

[0077] The present invention has the following beneficial effects:

[0078] The present invention proposes a new solution to the shortcomings of the prior art, such as large workload and low efficiency. Without adding additional hardware and equipment, the accurate judgment of the transformer capacity is achieved by making full use of the measurement data collected by the metering device and combining the data analysis method. This method does not require the transformer to be shut down, thus avoiding the impact on the power supply quality. At the same time, the use of data analysis replaces the cumbersome manual verification, greatly improving work efficiency, and being able to process a large amount of transformer data in a relatively short time. Moreover, this simple and convenient calculation method has strong engineering practicality. It can not only be deployed in the electricity consumption information collection system, but also effectively solve the problem of file errors. Through this improvement, not only the accuracy and efficiency of transformer capacity judgment are improved, but also strong support is provided for the stable operation and optimization planning of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0080] Figure 1 This is a schematic diagram of the method flow of Example 1;

[0081] Figure 2 It is the T-shaped equivalent circuit of the transformer;

[0082] Figure 3 It is the three-phase equivalent circuit of high-supply and low-meter dedicated transformer users;

[0083] Figure 4 It is the vector conversion relationship diagram of the voltage between the high voltage side and the low voltage side of the transformer;

[0084] Figure 5 This is the relationship diagram of the voltage amplitude and phase shift vector caused by impedance. DETAILED DESCRIPTION

[0085] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] It should be understood that the step numbers used in this document are only for convenience of description and are not intended to limit the order in which the steps are executed.

[0087] It should be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0088] The terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0089] The term "and / or" means and includes any and all possible combinations of one or more of the associated listed items.

[0090] Embodiment 1:

[0091] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be combined with the specific embodiments of the present application and refer to the attached Figure 1 , clearly and completely describe the technical solution of the present invention.

[0092] This example collects the three-phase voltage and current data of a 10kV transformer low-voltage side concentrator and derives the transformer high-voltage side data by combining the transformer external characteristics. Assume the objective function of (Rt,,Xt), find the combination corresponding to the minimum value of the evaluation function, and the transformer capacity in the combination is the transformer to be judged.

[0093] A method for calculating transformer capacity based on external characteristics comprises the following steps:

[0094] Step S1: Select a transformer near a user or a transformer area as a reference transformer, and obtain measurement data of the transformer to be judged and the reference transformer, including voltage and current data;

[0095] Step S2: deriving high-voltage side data of the transformer to be determined and the reference transformer according to the types and measurement data of the transformer to be determined and the reference transformer;

[0096] Step S3: constructing an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle;

[0097] Step S4: judging the capacity of the transformer according to the impedance value when the evaluation function takes an extreme value.

[0098] In step S2 of the above method for calculating transformer capacity based on external characteristics, a metering point of a transformer adjacent to a user or a transformer in a substation is selected as a reference metering point. However, the type of the reference transformer is unknown, so the following is discussed in detail:

[0099] For high-supply and low-meter special transformers, based on the transformer equivalent circuit, the collected measurement values ​​on the low-voltage side of the transformer are converted into the voltage on the high-voltage side of the transformer.

[0100] The transformer equivalent circuit is T-shaped, such as Figure 2 As shown, R m , X m is the excitation impedance, R h , X h is the high voltage side leakage impedance, R l , X l is the low voltage side leakage impedance. Generally, the excitation current is much smaller than the user's normal load current and has little effect on the line voltage drop. m , X m Ignore. h , X h , R l , X l It can be uniformly attributed to the high voltage side or the low voltage side. In the following, the impedance is uniformly expressed as R t , X t .

[0101] This is by R t , X t The voltage drop caused by the transformer is greater than the voltage drop caused by the external line. We set the voltage on the low-voltage side of the transformer to E a 、E b 、E c , can be obtained as Figure 2 The three-phase equivalent circuit of a high-supply, low-power dedicated transformer user is shown.

[0102] according to Figure 3 The circuit can be used to derive the transformer high-voltage side source voltage from the transformer low-voltage side measurement value. The vector conversion relationship between the high-voltage side and the low-voltage side voltage is as follows: Figure 4 shown.

[0103] The three-phase voltage, current, voltage angle and current angle of the metering point are defined as U a , U b , U c ,I a ,I b ,I c , α1, α2, α3, φ a ,φ b ,φ c The transformer impedance R can be known from the transformer capacity. t , X t , according to Table 1, list the transformer capacity and impedance R t , X t The corresponding relationship between , we can know:

[0104] (R t,X t )=∈{(0.0557,0.11526),(0.0313,0.07364),(0.0240,0.05933),(0.0184,0.04777),(0.0138,0.03756),(0.0104,0.03026),(0.0078,0.02438),(0.0059,0.01945),(0.0043,0.01541)}

[0105] Table 1 Transformer capacity-impedance correspondence table

[0106]

[0107] The voltage amplitude and phase shift vector relationship caused by impedance is as follows: Figure 5 As shown. Assume E a ′、E b ′、E c ′ is the voltage amplitude after offset correction, β1, β2, β3 are the corrected voltage angles, θ a ,θ b ,θ c is the phase shift, we have:

[0108]

[0109] β1=α1+θ a -θ b (7)

[0110] β2=α2+θ b -θ c (8)

[0111] β3=α3+θ c -θ a (9)

[0112] Assume that the high voltage line voltage is E L1 、E L2 、E L3 , according to the triangle cosine theorem, we have:

[0113] E L1 2 =E a ' 2 +E b ' 2 -2E a ′E b ′cosβ1 (10)

[0114] E L2 2 =E b ' 2+E c ' 2 -2E b ′E c ′cosβ2 (11)

[0115] E L3 2 =E c ' 2 +E a ' 2 -2E c ′E a ′cosβ3 (12)

[0116] Since the zero-sequence impedance R n , X n Not available, U n It cannot be calculated, so the high-voltage side phase voltage E a 、E b 、E c Cannot be directly superimposed by U n Usually the three phases of high voltage lines are relatively balanced, so it can be assumed that E a 、E b 、E c The angle between them is 120°. According to the cosine theorem, we have:

[0117] E L1 2 =E a 2 +E b 2 +E a E b (13)

[0118] E L2 2 =E b 2 +E c 2 +E b E c (14)

[0119] E L3 2 =E c 2 +E a 2 +E c E a (15)

[0120] Through the above formulas (1)-(15), the voltage value on the high voltage side can be inferred from the measured value on the low voltage side.

[0121] For high-voltage power supply and high-voltage metering transformers, based on the collected A-phase line voltage, C-phase line voltage and line voltage angle, the B-phase line voltage is calculated according to the cosine theorem. Specifically:

[0122] E L3 2 =E L1 2 +E L2 2 -2E L1 E L2 cosδ3 (16)

[0123] Where δ3 is the line voltage angle between phase A and phase C.

[0124] Assume that the transformers to be judged in step S3 are E1, E2, and E3; the three-phase voltage on the high-voltage side of the reference transformer is E ref1 、E ref2 、E ref3 Since the transformer has two wiring groups, Dyn11 and Yyn0, E1, E2, E3, E ref1 、E ref2 、E ref3 It can be phase voltage or line voltage. In addition, there are 6 possible connection phases (ABC, BCA, CAB, ACB, BAC, CBA). Therefore, there are 24 possible values ​​after permutation and combination. It is necessary to calculate the voltage under 24 corresponding relationships and define the evaluation function as:

[0125] F p (Rt,Xt)=[E1-k r E ref1 ] 2 +[E2-k r E ref2 ] 2 +[E3-k r E ref3 ] 2 (p=1…24)(17)

[0126] Among them, k r k is the reference coefficient of the ratio of the high voltage side voltage of the transformer to be judged to the reference transformer, r It is the ratio of the high voltage side of the transformer that eliminates noise interference through multiple calculations.

[0127] In the above step S4, the evaluation function is transformed into the following model:

[0128] F(Rt,Xt)=min[F1(Rt,Xt),F2(Rt,Xt)...,F 24 (Rt,Xt)],

[0130] (R t,X t )=∈{(0.0557,0.11526),(0.0313,0.07364),(0.0240,0.05933),(0.0184,0.04777),(0.0138,0.03756),(0.0104,0.03026),(0.0078,0.02438),(0.0059,0.01945),(0.0043,0.01541)}

[0131] Under a corresponding relationship enumerated in the current text, when R t , X t When a certain combination is satisfied, F(R t , X t ) is the smallest; the capacity within this corresponding relationship is the required transformer capacity.

[0132] Embodiment 2:

[0133] This embodiment provides a system for calculating transformer capacity based on external characteristics, including:

[0134] Data acquisition module: selects the transformer of the neighboring user or substation as the reference transformer, obtains the measurement data of the transformer to be judged and the reference transformer, including voltage and current data; this module is used to implement the function of step S1 in embodiment 1, which will not be repeated here.

[0135] Voltage derivation module: derives the high-voltage side data of the transformer to be judged and the reference transformer according to the types and measurement data of the transformer to be judged and the reference transformer; this module is used to implement the function of step S2 in embodiment 1, which will not be repeated here.

[0136] Impedance combination evaluation module: construct an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle; this module is used to implement the function of step S3 in embodiment 1, which will not be repeated here.

[0137] Capacity determination module: judge the capacity of the transformer according to the impedance value when the evaluation function takes the extreme value. This module is used to implement the function of step S4 in the first embodiment, which will not be described in detail here.

[0138] Embodiment three:

[0139] This embodiment provides an electronic device having a computer program stored thereon. When the computer program is executed by a processor, a method for calculating transformer capacity based on external characteristics as described in any embodiment of the present invention is implemented.

[0140] Embodiment 4:

[0141] This embodiment provides a computer-readable medium for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement a method for calculating transformer capacity based on external characteristics as described in any embodiment of the present invention.

[0142] In the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, c can be single or multiple.

[0143] Those of ordinary skill in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented in a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0144] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0145] In several embodiments provided in the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), disk or optical disk, and other media that can store program codes.

[0146] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for calculating transformer capacity based on external characteristics, characterized in that: The following steps are involved: Step S1: Select a transformer near a user or a transformer area as a reference transformer, and obtain measurement data of the transformer to be judged and the reference transformer, including voltage and current data; Step S2: deriving high-voltage side data of the transformer to be determined and the reference transformer according to the types and measurement data of the transformer to be determined and the reference transformer; Step S3: constructing an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle; Step S4: judging the capacity of the transformer according to the impedance value when the evaluation function takes an extreme value.

2. The method for calculating transformer capacity based on external characteristics according to claim 1, characterized in that: The high-voltage side data of the transformer to be determined and the reference transformer are derived according to the types and measurement data of the transformer to be determined and the reference transformer, and the specific steps are as follows: For a special transformer with a metering device installed on the low-voltage side of the transformer, the collected measurement values ​​on the low-voltage side of the transformer are converted into the voltage on the high-voltage side of the transformer based on the transformer equivalent circuit; The specific steps include: The voltage on the low voltage side of the transformer is set to E a 、E b 、e c , based on the transformer equivalent circuit, the three-phase equivalent circuit of the high-supply and low-meter dedicated transformer user is obtained; Assume E a ′、E b ′、E c ′ is the voltage amplitude after the offset correction caused by impedance, β1, β2, β3 are the voltage angles after the correction caused by impedance, θ a ,θ b ,θ c is the phase shift, then: β1=α1+θ a -θ b β2=α2+θ b -θ c β3=α3+θ c -θ a Where: U a , U b , U c is the three-phase voltage at the metering point; I a ,I b ,I c is the three-phase current at the metering point; α1, α2, α3 are the three-phase voltage angles at the metering point; is the three-phase current angle at the metering point; R t , X t is the transformer impedance, obtained by the transformer model and capacity; Assume that the high voltage line voltage is E L1 、E L2 、E L3 , according to the triangle cosine theorem, we have: Usually the high voltage line is set up with three-phase balance, then E a 、E b 、E c The angle between them is 120°. According to the cosine theorem, we have: AND L1 2 =And a 2 +E b 2 +E a AND b AND L2 2 =And b 2 +E c 2 +E b AND c AND L3 2 =And c 2 +E a 2 +E c AND a Through the above steps, the voltage value of the high voltage side is obtained based on the measured value of the low voltage side of the transformer; For a special transformer with a metering device installed on the high-voltage side of the transformer, the B-phase line voltage is calculated according to the cosine theorem based on the collected A-phase line voltage, C-phase line voltage and line voltage angle on the high-voltage side of the transformer; the specific formula is: AND L3 2 =And L1 2 +E L2 2 -2E L1 AND L2 cosδ3 Where δ3 is the line voltage angle between phase A and phase C.

3. The method for calculating transformer capacity based on external characteristics according to claim 1, characterized in that: According to the corresponding relationship between transformer capacity and impedance and the external characteristic principle, an evaluation function is constructed. The specific formula of the evaluation function is as follows: Assume that the three-phase voltage on the high-voltage side of the transformer to be judged after the transformation is E1, E2, and E3; the three-phase voltage on the high-voltage side of the reference transformer is E ref1 、E ref2 、E ref3 ; The evaluation function is: F p (Rt,Xt)=[E1-k r E ref1 ] 2 +[E2-k r E ref2 ] 2 +[E3-k r E ref3 ] 2 (p.1...24) Among them, k r is the reference coefficient of the ratio of the high voltage side voltage of the transformer to be judged to that of the reference transformer; since there are two wiring groups of transformers, Dyn11 and Yyn0, E1, E2, E3, E ref1 、E ref2 、E ref3 It is phase voltage or line voltage, which is determined according to the wiring group type; there are 6 situations according to the wiring phase: ABC, BCA, CAB, ACB, BAC, CBA, determine E1, E2, E3, E ref1 、E ref2 、E ref3 There are 24 values ​​of , p = 1, 2, 3, ..., 24, corresponding to 24 values ​​respectively.

4. The method for calculating transformer capacity based on external characteristics according to claim 1, characterized in that: The impedance value when the evaluation function takes the extreme value is used to determine the capacity of the transformer. The specific calculation formula is as follows: F(Rt,Xt)=min[F1(Rt,Xt),F2(Rt,Xt)...,F 24 (Rt,Xt)] Known F(R t ,X t ), when R t , X t When a certain combination is satisfied, F(R t ,X ct ) is the smallest; the capacity within this corresponding relationship is the required transformer capacity.

5. A system for calculating transformer capacity based on external characteristics, characterized in that: include: Data acquisition module: selects the transformer of the neighboring user or substation as the reference transformer, and obtains the measurement data of the transformer to be judged and the reference transformer, including voltage and current data; Voltage derivation module: derives the high-voltage side data of the transformer to be judged and the reference transformer according to the types and measurement data of the transformer to be judged and the reference transformer; Impedance combination evaluation module: constructs an evaluation function based on the corresponding relationship between transformer capacity and impedance and the principle of external characteristics; Capacity determination module: Determine the capacity of the transformer based on the impedance value when the evaluation function takes the extreme value.

6. A system for calculating transformer capacity based on external characteristics according to claim 5, characterized in that: The voltage derivation module deduces the high-voltage side data of the transformer to be determined and the reference transformer according to the types of the transformer to be determined and the reference transformer and the measurement data. The specific steps are as follows: For a special transformer with a metering device installed on the low-voltage side of the transformer, the collected measurement values ​​on the low-voltage side of the transformer are converted into the voltage on the high-voltage side of the transformer based on the transformer equivalent circuit; The specific steps include: The voltage on the low voltage side of the transformer is set to E a 、E b 、E c Based on the transformer equivalent circuit, the high Three-phase equivalent circuit for low-voltage transformer users; Assume E a ′、E b ′、E c ′ is the voltage amplitude after the offset correction caused by impedance, β1, β2, β3 are the voltage angles after the correction caused by impedance, θ a ,θ b ,θ c is the phase shift, then: β1=α1+θ a -θ b β2=α2+θ b -θ c β3=α3+θ c -θ a Where: U a , U b , U c is the three-phase voltage at the metering point; I a ,I b ,I c is the three-phase current at the metering point; α1, α2, α3 are the three-phase voltage angles at the metering point; is the three-phase current angle at the metering point; R t , X t is the transformer impedance, obtained by the transformer model and capacity; Assume that the line voltage on the high voltage side is E L1 、E L2 、E L3 , according to the triangle cosine theorem, we have: Usually the high voltage line is set up with three-phase balance, then E a 、E b 、E c The angle between them is 120°. According to the cosine theorem, we have: AND L1 2 =And a 2 +E b 2 +E a AND b AND L2 2 =And b 2 +E c 2 +E b AND c AND L3 2 =And c 2 +E a 2 +E c AND a Through the above steps, the voltage value of the high voltage side is obtained based on the measured value of the low voltage side of the transformer; For a special transformer with a metering device installed on the high-voltage side of the transformer, the B-phase line voltage is calculated according to the cosine theorem based on the collected A-phase line voltage, C-phase line voltage and line voltage angle on the high-voltage side of the transformer; the specific formula is: AND L3 2 =And L1 2 +E L2 2 -2E L1 AND L2 cosδ3 Where δ3 is the line voltage angle between phase A and phase C.

7. The system for calculating transformer capacity based on external characteristics according to claim 5, characterized in that: The impedance combination evaluation module constructs an evaluation function according to the corresponding relationship between transformer capacity and impedance and the external characteristic principle. The specific formula of the evaluation function is as follows: Assume that the three-phase voltage on the high-voltage side of the transformer to be judged after the transformation is E1, E2, and E3; the three-phase voltage on the high-voltage side of the reference transformer is E ref1 、E ref2 、E ref3 ; The evaluation function is: F p (Rt,Xt)=[E1-k r E ref1 ] 2 +[E2-k r E ref2 ] 2 +[E3-k r E ref3 ] 2 (p.1...24) Among them, k r is the reference coefficient of the ratio of the high voltage side voltage of the transformer to be judged to that of the reference transformer; since there are two wiring groups of transformers, Dyn11 and Yyn0, E1, E2, E3, E ref1 、E ref2 、E ref3 It is phase voltage or line voltage, which is determined according to the wiring group type; there are 6 situations according to the wiring phase: ABC, BCA, CAB, ACB, BAC, CBA, determine E1, E2, E3, E ref1 、E ref2 、E ref3 There are 24 values ​​of , p = 1, 2, 3, ..., 24, corresponding to 24 values ​​respectively.

8. The method for calculating transformer capacity based on external characteristics according to claim 1, characterized in that: The capacity determination module determines the capacity of the transformer according to the impedance value when the evaluation function takes an extreme value. The specific calculation formula is as follows: F(Rt,Xt)=min[F1(Rt,Xt),F2(Rt,Xt)...,F 24 (Rt,Xt)] Known F(R t ,X t ), when R t , X t When a certain combination is satisfied, F(R t ,X t ) is the smallest; the capacity within this corresponding relationship is the required transformer capacity.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for calculating transformer capacity based on external characteristics as described in any one of claims 1 to 4 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for calculating transformer capacity based on external characteristics as claimed in any one of claims 1 to 4 is implemented.

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