CN117706299A - A method for identifying transformer winding faults in humid environment - Google Patents

Abstract

The invention discloses a transformer winding fault identification method based on a humid environment, which comprises the steps of firstly testing a transformer, adjusting the ambient humidity of the transformer to obtain the resistance value of the insulation resistance of the transformer winding, and then obtaining the frequency response curves of the transformer under different humidities; calculating an average deviation rate mu through the resistance values of the insulation resistors under different humidity, and calculating an insulation state factor theta of the winding by combining the average deviation rate; and finally, calculating a fault distinguishing factor beta to judge the fault type by calculating fault factors phi and lambda under the phase frequency and amplitude frequency respectively.

Description

A method for identifying transformer winding faults in humid environment

Technical field

The invention belongs to the technical field of transformer fault simulation, and specifically relates to a method for identifying transformer winding faults in a humid environment.

Background technique

As one of the core equipment in the power system and traction power supply system, the stability and reliability of the transformer are related to the normal operation of the entire system. The operating status of the transformer directly determines the safety and stability of the power system. Considering the high cost of transformers, once a fault occurs, it may cause huge economic losses. About 2/3 of transformer faults are winding faults. During the transportation of the transformer, it may be affected by bumps, causing slight deformation of the windings. The main problem is that when the transformer is short-circuited, the strong short-circuit current will generate huge electric force, which will deform the windings. Over time, these deformations will gradually accumulate, eventually leading to severe winding deformation, which will cause transformer failure and pose a threat to the safety and stability of the power system. Therefore, timely monitoring of the operating status of the transformer and accurate assessment of the condition of the windings are crucial to preventing sudden failures of the transformer.

In transformers, insulation resistance testing is critical to assess the health of the windings. Regular insulation resistance testing is a means of preventive maintenance. By monitoring insulation resistance trends, potential problems can be detected early and appropriate maintenance measures can be taken to prevent further development of winding faults. The frequency response method is currently the most widely used transformer winding fault detection method. Through the combined analysis of insulation resistance test and frequency response method, it can be determined whether there is a fault and its type. However, the current evaluation index of the frequency response method requires the staff to have rich knowledge, and the accuracy of the judgment for different transformers is low. In particular, there is no unified judgment standard for different fault types. To address this problem, the patent of the present invention introduces A method based on the identification of transformer winding faults in humid environments. This method has the advantages of accurate detection of transformer faults and easy judgment. At the same time, it can well classify different fault types, which is very important for ensuring the stable operation of transformers and power systems. meaning.

Contents of the invention

This application provides a method for identifying transformer winding faults in humid environments, which can accurately and effectively determine the status of the transformer winding based on the proposed characteristic parameters.

This application provides a method for identifying transformer winding faults in humid environments. The test platform mainly includes: transformer box, core (3), high-voltage winding (5), low-voltage winding (6), wire cake They are connected in series, power supply (9), bushing (2), switch (10), frequency response tester (1), computer (8), humidity sensor (4), humidifier (7), insulation resistance measuring instrument (11), switch (12) is characterized by combining the frequency response curves of different humidity, extracting transformer characteristics based on humidity, amplitude-frequency curve, and phase-frequency curve to determine the winding status. The specific test method includes the following steps:

Step 1: Obtain the insulation resistance value under different humidity

Measure the insulation resistance of the transformer winding. Before making the measurement, disconnect the power supply of the equipment or circuit under test (9), and take necessary safety measures. Use a special insulation resistance measuring instrument (11) to connect the test leads of the test instrument. Go to the winding and set the test voltage of the test instrument. Start the test instrument and apply the selected voltage to the winding. While applying voltage, the test instrument will measure the current under the applied voltage and calculate the resistance value of the insulation resistance, recorded as; ρ ₁ ρ ₂ .....ρ _j ;

Step 2: Obtain frequency response signals under different humidity

Measure the frequency response signal of the transformer under different humidity environments of the transformer. The output end of the frequency response tester is connected to the bottom of the high-voltage winding (5) through the bushing. The test end of the frequency response tester is connected to the top of the high-voltage winding through the bushing. First, close the switch (10 ), close the switch and simultaneously adjust the humidifier (7) to adjust the ambient humidity. Monitor the temperature around the winding through the humidity sensor (4). The humidity sensor is connected to a computer to monitor the humidity in real time. After reaching the target value, open the switch and close the switch (12 ) Obtain the frequency response curve of the transformer winding in this state by turning on the frequency response tester. Repeat the test to obtain the frequency response curve of the transformer winding at [10, 80] with a gradient of 5, and pass the frequency response tester The measured frequency response curve amplitude-frequency data A _i (f), A _i (f) = [a _i1 a _i2 ...a _iN ], the measured phase-frequency data δ _i (f), δ _i (f) = [η _i1 η _i2 ... η _iN ], where a _iN and η _iN respectively represent the amplitude and phase angle of the Nth data point of the i-th group of data;

Step 3: Diagnosis of transformer winding fault

(1) Calculate the average deviation rate μ of the insulation resistance between the winding to be detected and the normal winding under different humidity

ρ _j represents the insulation resistance value when the humidity is j, and ρ ₀ represents the insulation resistance value under normal humidity.

(2) Calculate the insulation state factor θ

If F ₁ ≤ θ ≤ _{F 2} , it can be judged that the winding has not failed; if θ > F ₁ or θ < F ₂ , it can be judged that the winding has failed. F ₁ and F ₂ are related to the transformer model, operating parameters, and windings. constant;

Step 4: Determine the type of transformer winding fault, including:

(1) Calculate the fault factor φ under phase frequency

η _j represents the amplitude of the jth frequency point of the frequency response curve under normal circumstances, and N represents the number of collection points.

(2) Calculate the fault factor Λ under amplitude and frequency

a _j represents the amplitude of the jth frequency point of the frequency response curve under normal circumstances.

(3) Calculate the fault differentiation factor β

If β ≤ F ₃ , the fault is judged to be axial displacement; if β > F ₃ , the fault is judged to be winding deformation. M ₃ is a constant related to the transformer model, operating parameters, and windings.

Description of the drawings

Figure 1 Flowchart of a method for identifying transformer winding faults in humid environments

Figure 2 Test platform for transformer winding fault identification in simulated humid environment

Detailed ways

The following is further detailed in conjunction with the accompanying drawings. The specific method steps are as follows:

Step 1: Obtain the insulation resistance value under different humidity

Measure the insulation resistance of the transformer winding. Before making the measurement, disconnect the power supply of the equipment or circuit under test (9), and take necessary safety measures. Use a special insulation resistance measuring instrument (11) to connect the test leads of the test instrument. Go to the winding and set the test voltage of the test instrument. Start the test instrument and apply the selected voltage to the winding. While applying voltage, the test instrument will measure the current under the applied voltage and calculate the resistance value of the insulation resistance, recorded as; ρ ₁ ρ ₂ .....ρ _j ;

Step 2: Obtain frequency response signals under different humidity

Measure the frequency response signal of the transformer under different humidity environments of the transformer. The output end of the frequency response tester is connected to the bottom of the high-voltage winding (5) through the bushing. The test end of the frequency response tester is connected to the top of the high-voltage winding through the bushing. First, close the switch (10 ), close the switch and simultaneously adjust the humidifier (7) to adjust the ambient humidity. Monitor the temperature around the winding through the humidity sensor (4). The humidity sensor is connected to a computer to monitor the humidity in real time. After reaching the target value, open the switch and close the switch (12 ) Obtain the frequency response curve of the transformer winding in this state by turning on the frequency response tester. Repeat the test to obtain the frequency response curve of the transformer winding at [10, 80] with a gradient of 5, and pass the frequency response tester The measured frequency response curve amplitude-frequency data A _i (f), A _i (f) = [a _i1 a _i2 ...a _iN ], the measured phase-frequency data δ _i (f), δ _i (f) = [η _i1 η _i2 ... η _iN ], where a _iN and η _iN respectively represent the amplitude and phase angle of the Nth data point of the i-th group of data;

Step 3: Diagnosis of transformer winding fault

(1) Calculate the average deviation rate μ of the insulation resistance between the winding to be detected and the normal winding under different humidity

ρ _j represents the insulation resistance value when the humidity is j, and ρ ₀ represents the insulation resistance value under normal humidity.

(2) Calculate the insulation state factor θ

If F ₁ ≤ θ ≤ _{F 2} , it can be judged that the winding has not failed; if θ > F ₁ or θ < F ₂ , it can be judged that the winding has failed. F ₁ and F ₂ are related to the transformer model, operating parameters, and windings. constant;

Step 4: Determine the type of transformer winding fault, including:

(1) Calculate the fault factor φ under phase frequency

η _j represents the amplitude of the jth frequency point of the frequency response curve under normal circumstances, and N represents the number of collection points.

(2) Calculate the fault factor Λ under amplitude and frequency

a _j represents the amplitude of the jth frequency point of the frequency response curve under normal circumstances.

(3) Calculate the fault differentiation factor β

If β ≤ F ₃ , the fault is judged to be axial displacement; if β > F ₃ , the fault is judged to be winding deformation. M ₃ is a constant related to the transformer model, operating parameters, and windings.

Claims (2)

1. The transformer fault identification test platform is built under a humid environment, and is characterized in that a transformer box body, an iron core (3), a high-voltage winding (5) and a low-voltage winding (6) are connected in series, a power supply (9), a sleeve (2), a switch (10), a frequency response tester (1), a computer (8), a humidity sensor (4), a humidifier (7), an insulation resistance measuring instrument (11) and a switch (12) are connected in series, and the transformer fault identification test platform is characterized by combining frequency response curves of different humidities, extracting transformer characteristics according to the humidities, amplitude-frequency curves and phase-frequency curves and judging winding states.

2. A method for identifying faults of a transformer winding in a humid environment, which is tested by using the device of claim 1, and is characterized by comprising the following steps:

step one: obtaining insulation resistance values under different humidity

The insulation resistance of the transformer winding is measured, the power supply (9) of the device or circuit to be tested is disconnected before the measurement is performed, necessary safety measures are performed, a special insulation resistance measuring instrument (11) is used for connecting the test lead of the test instrument to the winding, and the test voltage of the test instrument is set. The test instrument is activated and a selected voltage is applied to the windings. When voltage is applied, the testing instrument measures current under the applied voltage, and the resistance value of the insulation resistor is calculated and recorded as; ρ ₁ ρ ₂ .....ρ _j ；

Step two: obtaining frequency response signals under different humidity

Measuring transformer frequency response signals under different humidity environments of a transformer, connecting an output end of a frequency response tester to the bottom of a high-voltage winding through a sleeve, connecting a test end of the frequency response tester to the top of the high-voltage winding through a sleeve, firstly, opening a switch, closing the switch, simultaneously adjusting a humidifier to adjust the environment humidity, monitoring the temperature around the winding through a humidity sensor, monitoring the humidity in real time through a connecting computer, opening the switch after reaching a target value, closing the switch, acquiring a frequency response curve of the transformer winding in the state through the connection of the frequency response tester, repeating the test, and acquiring the winding of [10, 80 ]]The frequency response curve of the transformer winding under the gradient of 5 is used for measuring amplitude-frequency data A of the frequency response curve by a frequency response tester _i (f)，A _i (f)＝[a _i1 a _i2 …a _iN ]Measured phase frequency data delta _i (f)，δ _i (f)＝[η _i1 η _i2 … η _iN ]Wherein a is _iN And eta _iN Respectively representing the amplitude and phase angle of the nth data point of the ith group of data;

step three: transformer winding fault judgment

(1) Calculating average deviation rate mu of insulation resistance between windings to be detected and normal windings under different humidity

ρ _j Expressed as insulation resistance value at humidity j ρ ₀ The insulation resistance value is expressed as a normal humidity;

(2) Calculating to obtain insulation state factor theta

If F ₁ ≤θ≤F ₂ The winding can be judged to have no fault; if theta is>F ₁ Or theta<F ₂ Then the winding can be judged to be faulty, F ₁ 、F ₂ Is a constant related to the type of transformer, operating parameters, windings;

step four: the transformer winding fault type judgment comprises the following steps:

(1) Calculating fault factor phi under phase frequency

(2) Calculating fault factor lambda under amplitude frequency

a _j The amplitude of the jth frequency point of the frequency response curve under normal conditions is represented;

(3) Calculating a fault discrimination factor beta

If beta is less than or equal to F ₃ Judging the fault as axial displacement; if beta is>F ₃ Judging the fault as winding deformation, M ₃ Is a constant related to the type of transformer, operating parameters and windingsA number.