A voltage transformer fault on-line diagnosis method

Abstract

This invention discloses a fault diagnosis method for voltage transformers, aiming to analyze faults in operating voltage transformers without power interruption. Under healthy conditions, a mathematical model of the voltage transformer under test is obtained using the outputs of a standard voltage transformer and the transformer under test. Under operating conditions, the output of the standard voltage transformer is used as the input signal, substituted into the mathematical model to obtain the theoretical output of the voltage transformer under test. This theoretical output is then compared with the actual output of the voltage transformer under test, and a quantitative evaluation index is established to assess the deviation between the actual and theoretical outputs, thereby determining the fault state of the voltage transformer online.

Description

Technical Field

[0001] This invention relates to the field of condition assessment of power transmission and distribution equipment, and more specifically, to an online fault diagnosis method for voltage transformers. Background Technology

[0002] Voltage transformers are the source of voltage information for the protection, control, measurement, metering, and fault recording subsystems of intelligent substations. Their operational reliability and measurement accuracy are closely related to the safety, reliability, and economic operation of the power system. Voltage transformers operating in the field generally include electromagnetic voltage transformers, capacitive voltage transformers, electronic voltage transformers, and photoelectric voltage transformers. Electromagnetic voltage transformers are reliable and stable, but they are bulky, have complex insulation structures, and are prone to ferroresonance. Capacitive voltage transformers are small and lightweight, but are easily affected by both natural and electromagnetic environmental factors, resulting in poor performance stability. Electronic voltage transformers are compact, have no magnetic saturation, and a large dynamic range, but their acquisition units are susceptible to electromagnetic interference, affecting their stability. Photoelectric voltage transformers are not yet technologically mature and are not used in industrial fields. Considering the stability and reliability of voltage transformers, it is necessary to assess and analyze their fault conditions.

[0003] Existing technologies include offline detection methods for voltage transformers during power outages. After a power outage, a standard voltage transformer is connected, and its output is compared with that of the voltage transformer under test to assess whether the transformer is faulty. However, this method involves significant power outage costs, complex on-site wiring and testing processes, and is difficult to implement.

[0004] Existing technologies also include methods for analyzing the decomposition gases in voltage transformers. During the operation of a voltage transformer, the internal SF6 gas undergoes a series of decomposition reactions, generating impurity gases such as SO2. By detecting the decomposition gases inside the voltage transformer and combining fuzzy logic analysis, virtual neural network analysis, and support vector machine analysis, the fault status of the voltage transformer can be analyzed. However, the implementation algorithm of this method is relatively complex and it is only applicable to gas-insulated and oil-insulated voltage transformers.

[0005] Existing technologies also include methods for analyzing vibration signals from voltage transformers. Like transformers, voltage transformers also exhibit slight electromagnetic vibrations and noises during operation. Under abnormal conditions, voltage transformers will show increased noise, which can be used to diagnose fault conditions. However, this method is still immature, its application scenarios are limited, and its engineering applications are limited.

[0006] Existing technologies also include frequency response analysis methods for voltage transformers. These methods involve acquiring the frequency domain input and output signals of the voltage transformer, deriving its frequency response equation, calculating the theoretical output of the voltage transformer's frequency response under operating conditions based on this equation, and determining whether the theoretical output matches the actual output. However, since a voltage transformer is itself a nonlinear system, this method is not widely applicable to voltage transformers. Summary of the Invention

[0007] The purpose of this invention is to provide an online fault diagnosis method for voltage transformers, aiming to analyze faults in operating voltage transformers without power interruption. Under healthy conditions, this invention uses the outputs of a standard voltage transformer and the voltage transformer under test (TD) to obtain a mathematical model of the TD. Under operating conditions, the output of the standard voltage transformer is used as the input signal, substituted into the mathematical model to obtain the theoretical output of the TD. This theoretical output is then compared with the actual output of the TD, and a quantitative evaluation index is established to assess the deviation between the actual and theoretical outputs, thereby determining the fault state of the voltage transformer online.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an online fault diagnosis method for voltage transformers, which involves solving the mathematical model of the voltage transformer under healthy conditions, and assessing whether the voltage transformer is in a fault state by comparing the difference between the theoretical output and the actual output of the voltage transformer without power interruption. The method specifically includes the following steps:

[0009] Step 1: Under healthy conditions, connect a standard voltage transformer and use the least squares method to obtain the input-output mathematical model of the voltage transformer under test;

[0010] Step 2: Under healthy conditions, obtain the voltage transformer deviation index threshold;

[0011] Step 3: In operation, connect a standard voltage transformer and use the output of the standard voltage transformer as the input matrix of the input-output mathematical model of the voltage transformer under test. Substitute the matrix into the mathematical model to solve for the theoretical output value of the voltage transformer under test.

[0012] Step 4: During operation, collect the actual output value of the voltage transformer under test;

[0013] Step 5: Compare the theoretical output value and the actual output value of the voltage transformer under test, and calculate the voltage transformer output deviation index;

[0014] Step 6: Compare the voltage transformer deviation index with the threshold. If the deviation index is less than the threshold, the voltage transformer is considered to be in normal condition; if the deviation index is greater than the threshold, the voltage transformer is considered to be in fault condition.

[0015] Furthermore, in step 1, the output of the standard voltage transformer serves as the output matrix of the input-output mathematical model of the voltage transformer under test:

[0016]

[0017] Among them, Y1, Y2, ..., Y L This indicates the L group output of a standard voltage transformer under healthy conditions.

[0018] The output of the voltage transformer under test serves as the input of the voltage transformer under test—the input matrix of the output mathematical model:

[0019]

[0020] Among them, X1, X2, ..., X L This indicates the output of the L group of the voltage transformer under test in a healthy state, and it has the following properties:

[0021]

[0022] Where x(l) represents the output signal of the voltage transformer under test in a healthy state.

[0023] The mathematical model for the input-output of the voltage transformer under test, solved using the least squares method, is as follows:

[0024] H = X -1 Y = [h1 h2…h L ]

[0025] Furthermore, in step 2, under healthy conditions, the voltage transformer deviation index is calculated, namely:

[0026]

[0027] Among them, Y 理 Y represents the theoretical output obtained from the mathematical model. 实 This indicates the actual output of the voltage transformer under test.

[0028] The 95% confidence level distribution of MAE is used as the deviation index threshold. limint .

[0029] Furthermore, in step 3, during operation, a standard voltage transformer is connected, and the output of the standard voltage transformer is used as the input matrix of the input-output mathematical model of the voltage transformer under test.

[0030]

[0031] Among them, U1, U2, ..., U LThis indicates the output of group L of the standard voltage transformer under operating conditions, and it has the following characteristics:

[0032]

[0033] Where u(l) represents the output signal of the standard voltage transformer under operating conditions.

[0034] Substitute the values ​​into the mathematical model to solve for the theoretical output value of the voltage transformer under test;

[0035] d 理 =UH

[0036] Furthermore, in step 4, during operation, the actual output value d of the voltage transformer under test is acquired. 实 ;

[0037] Furthermore, in step 5, the voltage transformer output deviation index is:

[0038]

[0039] Furthermore, in step 6, the voltage transformer deviation index MAE is... 运 and threshold MAE limint Compare, if MAE 运 <MAE limit If MAE 运 >MAE limit If so, the voltage transformer is determined to be in a fault state.

[0040] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0041] 1. This invention can evaluate the fault status of voltage transformers online based on the solved mathematical model of the voltage transformer, reducing the time required for on-site power outages and tests, and improving the efficiency of on-site work.

[0042] 2. This invention solves the problem of solving nonlinear systems of voltage transformers. By constructing the input and output matrices of the input-output mathematical model of the voltage transformer, the input-output mathematical model of the voltage transformer under test can be solved. This invention is applicable to voltage transformers actually operating in engineering sites. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the online fault diagnosis method for voltage transformers according to the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the invention.

[0045] An online fault diagnosis method for voltage transformers, the process is as follows: Figure 1 As shown, it includes the following steps:

[0046] Step 1: Under healthy conditions, connect a standard voltage transformer and use the output of the standard voltage transformer as the input of the voltage transformer under test—output matrix of the output mathematical model:

[0047]

[0048] Among them, Y1, Y2, ..., Y L This indicates the L group output of a standard voltage transformer under healthy conditions.

[0049] The output of the voltage transformer under test is collected and used as the input matrix of the input-output mathematical model of the voltage transformer under test.

[0050]

[0051] Among them, X1, X2, ..., X L This indicates the output of the L group of the voltage transformer under test in a healthy state, and it has the following properties:

[0052]

[0053] Where x(l) represents the output signal of the voltage transformer under test in a healthy state.

[0054] The mathematical model for the input-output of the voltage transformer under test, solved using the least squares method, is as follows:

[0055] H = X -1 Y = [h1 h2…h L (4)

[0056] Step 2: Under healthy conditions, acquire the actual output value Y of the voltage transformer under test. 实 Simultaneously, the theoretical output value Y of the voltage transformer under test is obtained by using the input-output mathematical model of the voltage transformer under test and the output of the standard voltage transformer. 理 Calculate the threshold value of the voltage transformer deviation index.

[0057]

[0058] Among them, Y 理 Y represents the theoretical output obtained from the mathematical model. 实 This indicates the actual output of the voltage transformer under test.

[0059] The 95% confidence level distribution of MAE is used as the deviation index threshold. limint .

[0060] Step 3: In operation, connect a standard voltage transformer, using the output of the standard voltage transformer as the input matrix of the measured voltage transformer's mathematical model:

[0061]

[0062] Among them, U1, U2, ..., U L This indicates the output of group L of the standard voltage transformer under operating conditions, and it has the following characteristics:

[0063]

[0064] Where u(l) represents the output signal of the standard voltage transformer under operating conditions.

[0065] Substitute the input matrix into the mathematical model to solve for the theoretical output value of the voltage transformer under test.

[0066] d 理 =UH (8)

[0067] Step 4: During operation, acquire the actual output value d of the voltage transformer under test. 实 .

[0068] Step 5: Compare the theoretical output value d of the voltage transformer under test. 理 and the actual output value d of the voltage transformer under test 实 The voltage transformer output deviation index is calculated as follows:

[0069]

[0070] Step 6: Set the voltage transformer deviation index MAE 运 and threshold MAE limint Compare, if MAE 运 <MAE limit If MAE 运 >MAE limit If so, the voltage transformer is determined to be in a fault state.

[0071] The present invention is in accordance with as follows Figure 1 The steps shown are for diagnosing faults in voltage transformers:

[0072] (1) Under healthy conditions, connect a standard voltage transformer and construct the output matrix of the input-output mathematical model of the voltage transformer under test using formula (1). Preferably, L is chosen as 5. Construct the input matrix of the input-output mathematical model of the voltage transformer using formulas (2) and (3). Solve the input-output mathematical model of the voltage transformer under test using formula (4).

[0073] (2) Use formula (5) to calculate the voltage transformer deviation index threshold.

[0074] (3) In operation, use formulas (6) and (7) to construct the input matrix and use formula (8) to solve for the theoretical output value of the voltage transformer.

[0075] (4) During operation, the actual output value of the voltage transformer under test is collected.

[0076] (5) Compare the theoretical output value of the voltage transformer under test with the actual output value of the voltage transformer under test, and calculate the voltage transformer output deviation index MAE using formula (9). 运 .

[0077] (6) The voltage transformer deviation index MAE obtained from formula (9) 运 The threshold MAE obtained from formula (5) limint Compare, if MAE 运 <MAE limit If MAE 运 >MAE limit If so, the voltage transformer is determined to be in a fault state.

[0078] The above examples are only used to illustrate the effects of the present invention, and the described embodiments are only a part of the embodiments of this application, not all of the embodiments. Finally, it should be noted that all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

Claims

1. A voltage transformer fault on-line diagnosis method, characterized in that, The method comprises the following steps: Step 1: in a healthy state, access to a standard voltage transformer, and use the least square method to obtain an input-output mathematical model of the measured voltage transformer; Step 2: in the healthy state, obtain a threshold of a voltage transformer deviation index; Step 3: in a running state, access to a standard voltage transformer, and use the output of the standard voltage transformer as an input matrix of the input-output mathematical model of the measured voltage transformer to solve a theoretical output value of the measured voltage transformer; Step 4: in the running state, collect an actual output value of the measured voltage transformer; Step 5: compare the theoretical output value and the actual output value of the measured voltage transformer to calculate a voltage transformer output deviation index; Step 6: compare the voltage transformer deviation index and the threshold, if the deviation index is less than the threshold, it is judged that the voltage transformer is in a normal state, and if the deviation index is greater than the threshold, it is judged that the voltage transformer is in a fault state; The specific process of calculating the input-output mathematical model of the measured voltage transformer in step 1 is as follows: An output matrix of the mathematical model is constructed: ； wherein, , , represents the L group output of the standard voltage transformer under healthy state; An input matrix of the mathematical model is constructed: ； wherein, , , represents the L group output of the voltage transformer under healthy state, and has: ； wherein, represents the output signal of the voltage transformer under healthy condition; The input-output mathematical model of the measured voltage transformer is solved by using the least square method: ； In step 3, the specific process of solving the theoretical output value of the measured voltage transformer in the running state is as follows: An input matrix of the mathematical model is constructed: ； wherein , , represents the L group output of the standard voltage transformer in the operating state, and has: ； wherein represents the output signal of the standard voltage transformer in the operating state; The theoretical output value of the measured voltage transformer is solved by substituting the mathematical model; 。 2. The on-line fault diagnostic method of a voltage transformer according to claim 1, characterized in that, said step 2 health state, the deviation indicator threshold is a 95% confidence distribution value of the deviation indicator wherein: ； wherein, represents a theoretical output obtained according to a mathematical model, represents an actual output of the voltage transformer under test.

3. The on-line fault diagnostic method of a voltage transformer as claimed in claim 1, wherein, In step 5, the voltage transformer output deviation index is: ； wherein d 实 represents the actual output value of the voltage transformer under the running state.

4. The on-line fault diagnostic method of a voltage transformer as claimed in claim 3, characterized in that, The step 6 compares the voltage transformer deviation degree index with a threshold value and the threshold value , if , it is judged that the voltage transformer is in normal state; if , it is judged that the voltage transformer is in fault state.

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