CN107329065B - A method of tractive transformer casing state of insulation in assessment military service - Google Patents

Abstract

The invention discloses a method for evaluating the insulation state of a traction transformer bushing in service. The evaluation of the insulation state of a traction transformer in service mainly includes the following steps: 1) testing the moisture content in the insulating oil of the traction transformer bushing when it leaves the factory; 2) Conduct insulation material experiments; 3) Test the insulation characteristic parameters of the traction transformer bushing when it leaves the factory; 4) Calculate the insulation characteristic parameters of the traction transformer bushing at the critical time; 5) Test the insulation characteristic parameters of the traction transformer bushing in service; 6) Evaluate the in-service Traction transformer bushing insulation status. The method of the invention applies sinusoidal AC voltages of different frequencies to the bushing to measure its dielectric constant under non-destructive conditions, has the advantages of low applied voltage and rich information, and overcomes the current frequency-domain dielectric problem of the existing technology that can only test the bushing. The electrical spectrum cannot be combined with the relevant information when the bushing leaves the factory, and it is impossible to comprehensively evaluate the shortcomings of the insulation state of the bushing.

Description

A Method for Evaluating the Insulation State of Traction Transformer Bushings in Service

technical field

The invention belongs to the field of transformer bushing insulation state detection, and in particular relates to a method for evaluating the insulation state of traction transformer bushings in service.

Background technique

As the external connection device of the transformer, the traction transformer bushing plays the role of support and connection insulation to realize the connection with the external electrical network. During the operation, the bushing is subjected to multiple effects of external moisture immersion and its own electrical, thermal and mechanical stress , its insulation will age, leading to failure of the traction transformer, which will affect the transmission of electric energy. Therefore, it is very important to evaluate the insulation state of the traction transformer in service. The frequency domain dielectric response method is a non-destructive test method that can effectively evaluate the aging degree and damp state of the bushing. Its principle is to apply sinusoidal AC voltages of different frequencies to the bushing to measure its dielectric constant. It has the advantages of low applied voltage and abundant information. However, at present, when evaluating and diagnosing traction transformer bushings in service based on the frequency domain dielectric response method, only the current frequency domain dielectric spectrum of the bushing can be tested, which cannot be combined with the information of the bushing when it leaves the factory, and cannot be comprehensively integrated. To evaluate the insulation state of bushings, a method for evaluating the insulation state of traction transformer bushings in service is urgently needed.

Contents of the invention

When effectively testing the real part of the relative complex permittivity of the traction variable bushing during the skylight time, in order to avoid the influence of the time-varying temperature on the test results caused by the short skylight time, the invention provides a traction transformer in service Method of bushing insulation state.

A method for assessing the insulation state of traction transformer bushings in service, the method comprising the following steps:

Step 1: Test the moisture content in the insulating oil of the traction transformer bushing when it leaves the factory

Test Test the moisture content in the insulating oil of the traction transformer bushing when it leaves the factory, denoted as C ₀ ;

Step 2: Conduct insulation material experiment

2.1 Immerse the insulating paper in the insulating oil, test the imaginary part of the relative complex permittivity of the insulation at each frequency point (1mHz, 2mHz, 4mHz and 0.01Hz) when the moisture content of the insulating oil is C ₀ , and then extract the insulation characteristic parameters X ₀ ;

2.2 Immerse the insulating paper in the insulating oil, test the imaginary part of the relative complex permittivity of the insulation at the above frequency points when the moisture content of the insulating oil is C _max , and then extract the insulating characteristic parameter X _max ;

2.3 Calculate the insulation characteristic parameter coefficient k by formula (1)

Step 3: Test the insulation characteristic parameters of the traction transformer bushing when it leaves the factory

Test Test the imaginary part of the relative complex permittivity of the insulation at the above frequency points (1mHz, 2mHz, 4mHz, 0.01Hz) when the traction transformer bushing leaves the factory (when the moisture content of the insulating oil is C ₀ ), and then extract the traction transformer bushing The insulation characteristic parameter Y ₀ at the factory;

Step 4: Calculate and obtain the insulation characteristic parameters of the traction transformer bushing when the moisture content C _max in the insulating oil is obtained

Calculating the insulation characteristic parameter Y _max of the traction transformer bushing when the moisture content C _max in the insulating oil is calculated by formula (2)

Y _max = kY ₀ (2)

Step 5: Test the insulation characteristic parameters of traction transformer bushings in service

The frequency-domain dielectric response test is carried out on the bushing insulation of the traction transformer in service, and the imaginary part of the relative complex permittivity of the bushing insulation of the traction transformer in service at the above frequency points (1mHz, 2mHz, 4mHz, 0.01Hz) is obtained, and then extracted Insulation characteristic parameter Y of traction transformer bushings in service

Step 6: Assess the insulation status of traction transformer bushings in service

Set the evaluation warning coefficient a, and calculate the insulation state coefficient H of the traction transformer bushing in service according to formula (3)

The extraction method of the described extraction insulation characteristic parameter is: record the test result of 0.01Hz frequency point as ε ₁ ″, the test result of 4mHz frequency point is recorded as ε ₂ ″, the test result of 2mHz frequency point is recorded as ε ₃ ″, and the test result of 1mHz frequency point The result is recorded as ε ₄ ″, and then the imaginary part of the relative complex permittivity obtained from the test at each frequency point is transformed into a logarithmic coordinate system, and then the test result is fitted based on the straight line expression shown in formula (4), and then obtained The slope s and the intercept b of the straight line expression shown in formula (4);

y=sx+b (4) In formula (4), y is logε", x is logω, ω is the angular frequency value of each test frequency point and is equal to 2πf, then the insulation characteristic parameters can be calculated by formula (5)

Description of drawings

Fig. 1. A flow chart of a method for assessing the insulation status of traction transformer bushings in service.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

Figure 1 shows a flow chart of a method for evaluating the insulation state of traction transformer bushings in service. From Figure 1, it can be seen that a method for evaluating the insulation state of traction transformer bushings in service includes the following steps:

Step 1: Test the moisture content in the insulating oil of the traction transformer bushing when it leaves the factory

Test Test the moisture content in the insulating oil of the traction transformer bushing when it leaves the factory, denoted as C ₀ ;

Step 2: Conduct insulation material experiment

2.1 Immerse the insulating paper in the insulating oil, and test the imaginary part of the relative complex permittivity of the insulation at the frequency point (1mHz, 2mHz, 4mHz, 0.01Hz) when the moisture content of the insulating oil is C ₀ , and then extract the insulation characteristic parameter X ₀ ;

2.2 Immerse the insulating paper in the insulating oil, test the imaginary part of the relative complex permittivity of the insulation at the above frequency points when the moisture content of the insulating oil is C _max , and then extract the insulating characteristic parameter X _max ;

2.3 Calculate the insulation characteristic parameter coefficient k by formula (1)

Step 3: Test the insulation characteristic parameters of the traction transformer bushing when it leaves the factory

Test Test the imaginary part of the relative complex permittivity of the insulation at the above frequency points (1mHz, 2mHz, 4mHz, 0.01Hz) when the traction transformer bushing leaves the factory (when the moisture content of the insulating oil is C ₀ ), and then extract the traction transformer bushing The insulation characteristic parameter Y ₀ at the factory;

Step 4: Calculate and obtain the insulation characteristic parameters of the traction transformer bushing when the moisture content C _max in the insulating oil is obtained

Calculating the insulation characteristic parameter Y _max of the traction transformer bushing when the moisture content C _max in the insulating oil is calculated by formula (2)

Y _max = kY ₀ (2)

Step 5: Test the insulation characteristic parameters of traction transformer bushings in service

The frequency-domain dielectric response test is carried out on the bushing insulation of the traction transformer in service, and the imaginary part of the relative complex permittivity of the bushing insulation of the traction transformer in service at the above frequency points (1mHz, 2mHz, 4mHz, 0.01Hz) is obtained, and then extracted Insulation characteristic parameter Y of traction transformer bushings in service

Step 6: Assess the insulation status of traction transformer bushings in service

Set the evaluation warning coefficient a to 0.8, and calculate the insulation state coefficient H of the traction transformer bushing in service according to formula (3)

The extraction method of the described extraction insulation characteristic parameter is: record the test result of 0.01Hz frequency point as ε ₁ ″, the test result of 4mHz frequency point is recorded as ε ₂ ″, the test result of 2mHz frequency point is recorded as ε ₃ ″, and the test result of 1mHz frequency point is ε 3 ″. The result is recorded as ε ₄ ″, and then the imaginary part of the relative complex permittivity obtained from the test at each frequency point is transformed into a logarithmic coordinate system, and then the test result is fitted based on the straight line expression shown in formula (4), and then obtained The slope s and the intercept b of the straight line expression shown in formula (4);

y=sx+b (4)

In formula (4), y is logε", x is logω, ω is the angular frequency value of each test frequency point and is equal to 2πf, then the insulation characteristic parameters can be calculated by formula (5)

Claims (1)

1. a kind of method of tractive transformer casing state of insulation in assessment military service, which is characterized in that include the following steps：

The first step：Moisture content in insulating oil when testing the factory of tractive transformer casing

Moisture content in insulating oil, is denoted as C when testing the factory of tractive transformer casing₀；

Second step：Carry out insulating materials experiment

2.1 immerse insulating paper in insulating oil, and test is C when insulating oil moisture content₀When insulating paper in Frequency point 1mHz, 2mHz, The opposite complex dielectric permittivity imaginary part of 4mHz and 0.01Hz, and then extract and obtain dielectric features parameter X₀；

2.2 immerse insulating paper in insulating oil, and test is C when insulating oil moisture content_maxWhen insulating paper in above-mentioned each Frequency point Opposite complex dielectric permittivity imaginary part, and then extract and obtain dielectric features parameter X_max；

2.3 calculate dielectric features parameter coefficient k by formula (1)

Third step：Dielectric features parameter when testing the factory of tractive transformer casing

When testing the factory of tractive transformer casing, i.e., insulating oil moisture content is C₀When, tractive transformer casing is in each Frequency point Opposite complex dielectric permittivity imaginary part, so extract the factory of tractive transformer casing when dielectric features parameter Y₀；

4th step：Tractive transformer casing dielectric features parameter when moisture content critical value in insulating oil is calculated

Moisture content C in insulating oil is calculated by formula (2)_maxWhen tractive transformer casing dielectric features parameter Y_max

Y_max=kY₀ (2)

5th step：Tractive transformer casing dielectric features parameter in test military service

To in military service tractive transformer set pipe insulation carry out the test of frequency domain dielectric response, be on active service in tractive transformer casing it is exhausted Edge each Frequency point opposite complex dielectric permittivity imaginary part, and then extract be on active service in tractive transformer casing dielectric features parameter Y

6th step：Tractive transformer casing state of insulation in assessment military service

Setting assessment vigilance parameter a, tractive transformer casing state of insulation coefficient H in being on active service is calculated according to formula (3)

In the second step, third step and the 5th step, the method for extracting dielectric features parameter is：Remember 0.01Hz Frequency point test knot Fruit is denoted as ε₁", 4mHz Frequency point test result is denoted as ε₂", 2mHz Frequency point test result is denoted as ε₃", 1mHz Frequency point test knot Fruit is denoted as ε₄", the opposite complex dielectric permittivity imaginary results for then testing each Frequency point are converted into logarithmic coordinates system, so Test result is fitted based on straight line expression formula shown in formula (4) afterwards, and then obtains the slope s of straight line expression formula shown in formula (4) With intercept b；

Y=sx+b (4)

Y is log ε " in formula (4), and x is log ω, and ω is to test the angular frequency value of each Frequency point and be equal to 2 π f, then dielectric features are joined Number can be calculated by formula (5)