Method for evaluating insulation state of transformer winding based on ultrasonic vibration bimodal

Abstract

The invention discloses a method for evaluating the insulation state of a transformer winding based on ultrasonic vibration bimodal. The method comprises the following steps: establishing a transformer winding insulation state evaluation test platform; testing is carried out based on the transformer winding insulation state evaluation test platform, and ultrasonic signal data of the ultrasonic sensor and oscillation signal data of the vibration sensor are obtained and processed; obtaining transformer winding state evaluation characteristic parameters; calculating a transformer winding insulation state evaluation factor; and evaluating the insulation state of the transformer winding based on the transformer winding insulation state evaluation factor. According to the method, the sensitivity of ultrasonic detection to insulation internal microstructure change and the reflecting capacity of vibration detection to winding overall mechanical state change are combined, signal characteristics in two modes are comprehensively analyzed, the limitation of single-mode detection can be effectively overcome, the insulation defect of the transformer winding is overcome, and the detection accuracy is improved. Especially, the detection capability and the evaluation precision of local tiny defects are improved.

Description

Technical Field

[0001] The present invention relates to the field of transformers, and particularly to a method for evaluating the insulation state of transformer windings based on dual - mode ultrasonic vibration. Background Art

[0002] Transformers play a core role in the power system, undertaking key functions such as voltage transformation and electric energy transmission. Their safe and stable operation is the key to ensuring the reliability of the power network. The insulation performance of windings is one of the important factors affecting the normal operation of transformers. Once problems such as aging and damage occur in the winding insulation, it may lead to faults such as short - circuit and breakdown, and then cause power outages, which have a serious negative impact on social production and life. With the continuous improvement of the reliability requirements of the power system for transformers, there is an urgent need for a method that can more accurately and sensitively evaluate the insulation condition of windings. Summary of the Invention

[0003] To solve the above - mentioned technical problems, the present invention provides a method for evaluating the insulation state of transformer windings based on dual - mode ultrasonic vibration, which has a simple algorithm and high accuracy.

[0004] The technical solution of the present invention to solve the above - mentioned technical problems is: A method for evaluating the insulation state of transformer windings based on dual - mode ultrasonic vibration, comprising the following steps:

[0005] Step 1: Build a test platform for evaluating the insulation state of transformer windings;

[0006] Step 2: Conduct tests based on the test platform for evaluating the insulation state of transformer windings, obtain ultrasonic signal data of ultrasonic sensors and oscillation signal data of vibration sensors, and process the data;

[0007] Step 3: Obtain characteristic parameters for evaluating the state of transformer windings;

[0008] Step 4: Calculate the evaluation factor for the insulation state of transformer windings;

[0009] Step 5: Realize the evaluation of the insulation state of transformer windings based on the evaluation factor for the insulation state of transformer windings.

[0010] The above-mentioned evaluation method for the insulation state of transformer windings based on ultrasonic vibration dual modes. In step 1, the evaluation test platform for the insulation state of transformer windings includes a transformer, a first acceleration sensor, a second acceleration sensor, a first ultrasonic sensor, a second ultrasonic sensor, a third ultrasonic sensor, a fourth ultrasonic sensor, a signal acquisition device, and a computer. The first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, and the fourth ultrasonic sensor are respectively installed at the central positions on the inner sides of the four sides of the transformer box body, and the first acceleration sensor and the second acceleration sensor are respectively installed at the central positions on the top and bottom of the transformer box body. The signal output ends of the first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, the fourth ultrasonic sensor, the first acceleration sensor, and the second acceleration sensor are connected to the input end of the signal acquisition device, and the output end of the signal acquisition device is connected to the computer. The signal acquisition device receives the data collected by the first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, the fourth ultrasonic sensor, the first acceleration sensor, and the second acceleration sensor and sends them to the computer, and the computer records and processes the data.

[0011] The above-mentioned evaluation method for the insulation state of transformer windings based on ultrasonic vibration dual modes. In step 2, the specific process of obtaining the ultrasonic signal data of the ultrasonic sensor and the oscillation signal data of the vibration sensor is as follows:

[0012] First, inject a first DC excitation into the high-voltage winding side of the transformer. The first DC excitation voltage is 20% of the rated voltage of the high-voltage side of the transformer. After the system is stable, remove the first DC excitation, and obtain the signal F of the first acceleration sensor through the signal acquisition device. 1s ;

[0013] Then, inject a second DC excitation into the low-voltage winding side of the transformer. The second DC excitation voltage is 20% of the rated voltage of the low-voltage side of the transformer. After the system is stable, remove the second DC excitation, and obtain the signal F of the second acceleration sensor through the signal acquisition device. 2s ;

[0014] Next, use the ultrasonic sensor to obtain the ultrasonic signal F generated by partial discharge in the transformer winding. 3j , F 3j represents the ultrasonic signal obtained by the j-th ultrasonic sensor, and the data acquisition time of the j-th ultrasonic sensor is T. j .

[0015] The above-mentioned evaluation method for the insulation state of transformer windings based on ultrasonic vibration dual modes. In step 2, the process of processing the data is as follows:

[0016] The signal decomposition formulas for the acceleration sensor and the ultrasonic sensor are as follows:

[0017]

[0018] where \(g(x)\) is the original signal, \(g_1(x)\) is the fundamental wave of the signal, and \(g_2(x),\cdots,g\) n (x) are the 2nd to nth harmonics of the signal;

[0019] Using formula (1) to perform frequency decomposition on F 3j to obtain the fundamental wave \(F\) corresponding to the ultrasonic signal 3j1 and the 2nd to nth harmonics \(F\) 3j2 ,\cdots,F 3jn ;

[0020] Using formula (1) to perform frequency decomposition on F 1s and F 2s to obtain the fundamental wave \(F\) of \(F\) 1s and the 2nd to nth harmonics \(F\) 1s1 ,\cdots,F 1s2 ,\cdots,F 1sn , and obtain the fundamental wave \(F\) of \(F\) 2s and the 2nd to nth harmonics \(F\) 2s1 ,\cdots,F 2s2 ,\cdots,F 1sn .

[0021] The above-mentioned method for evaluating the insulation state of a transformer winding based on ultrasonic vibration dual modes, the specific process of step three is as follows:

[0022] S31, calculate the total acceleration energy \(E\) 12 , and the calculation formula is as follows:

[0023]

[0024] where \(E\) 12 is the sum of the squares of the amplitudes of the first n harmonics of \(F\) 1s and \(F\) 2s ; \(F\) 1sj is the \(j'\)th harmonic of \(F\) 1s , and \(F\) 2sj is the \(j'\)th harmonic of \(F\) 2s ;

[0025] S32, calculate the total ultrasonic energy \(E_3\), and the calculation formula is as follows:

[0026]

[0027] where \(E_3\) is the sum of the squares of the amplitudes of the first n harmonics of \(F\) 3j ; \(F\) 3jk is the \(k\)th harmonic of the \(j\)th ultrasonic signal;

[0028] S33, for the total acceleration energy \(E\) 12Normalize:

[0029]

[0030] where E′ 12 is the total energy of acceleration after normalization; E 12min is the minimum value in the total energy value of acceleration; E 12max is the maximum value in the total energy value of acceleration;

[0031] S34, normalize the total ultrasonic energy E3:

[0032]

[0033] where E′3 is the total ultrasonic energy after normalization; E 3min is the minimum value in the total ultrasonic energy value; E 3maX is the maximum value in the total ultrasonic energy value.

[0034] In the above method for evaluating the insulation state of a transformer winding based on dual ultrasonic vibration modes, in step four, the calculation formula for the evaluation factor λ of the insulation state of the transformer winding is:

[0035] λ = E′ 12 + E′3 (6).

[0036] In the above method for evaluating the insulation state of a transformer winding based on dual ultrasonic vibration modes, in step five, the evaluation method for the insulation state of the transformer winding is as follows:

[0037] When 0 < λ ≤ 0.25, the insulation condition of the transformer winding is good;

[0038] When 0.25 < λ ≤ 0.56, the insulation condition of the transformer winding is average;

[0039] When λ > 0.56, there are problems with the insulation of the transformer winding, and corresponding repair or replacement measures need to be taken.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1. The present invention combines the sensitivity of ultrasonic detection to changes in the internal microscopic structure of insulation and the ability of vibration detection to reflect changes in the overall mechanical state of the winding. By comprehensively analyzing the signal characteristics in two modes, it can effectively overcome the limitations of single-mode detection, improve the detection ability and evaluation accuracy for insulation defects of transformer windings, especially local minor defects, and provide more reliable guarantee for the safe operation of transformers.

[0042] 2. Without affecting the internal core components of the transformer, the present invention can utilize a convenient and efficient technology to evaluate the interlayer insulation of the transformer, which not only provides strong support for the dynamic monitoring of the insulation state of the transformer, but also provides reliable guidance for reasonably arranging the maintenance and repair work of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the overall flowchart of the present invention.

[0044] Figure 2 It is the structural schematic diagram of the test platform for evaluating the insulation state of the transformer winding of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The present invention will be further described below in conjunction with the drawings and embodiments.

[0046] As Figure 1 shown, a method for evaluating the insulation state of a transformer winding based on dual-mode ultrasonic vibration includes the following steps:

[0047] Step 1: Build a test platform for evaluating the insulation state of the transformer winding.

[0048] As Figure 2 shown, the test platform for evaluating the insulation state of the transformer winding includes a transformer 1, a first acceleration sensor 2, a second acceleration sensor 3, a first ultrasonic sensor 4, a second ultrasonic sensor 5, a third ultrasonic sensor 6, a fourth ultrasonic sensor 7, a signal acquisition device 8, and a computer 9; the first ultrasonic sensor 4, the second ultrasonic sensor 5, the third ultrasonic sensor 6, and the fourth ultrasonic sensor 7 are respectively installed at the inner center positions of the four sides of the transformer box body, the first acceleration sensor 2 and the second acceleration sensor 3 are respectively installed at the center positions of the top and bottom of the transformer box body, and the signal output ends of the first ultrasonic sensor 4, the second ultrasonic sensor 5, the third ultrasonic sensor 6, the fourth ultrasonic sensor 7, the first acceleration sensor 2, and the second acceleration sensor 3 are connected to the input end of the signal acquisition device 8, and the output end of the signal acquisition device 8 is connected to the computer 9; the signal acquisition device 8 receives the data collected by the first ultrasonic sensor 4, the second ultrasonic sensor 5, the third ultrasonic sensor 6, the fourth ultrasonic sensor 7, the first acceleration sensor 2, and the second acceleration sensor 3 and sends them to the computer 9, and the computer 9 records and processes the data.

[0049] Step 2: Conduct tests based on the test platform for evaluating the insulation state of the transformer winding, obtain the ultrasonic signal data of the ultrasonic sensor and the oscillation signal data of the vibration sensor, and process the data.

[0050] In the second step, the specific process of obtaining the ultrasonic signal data of the ultrasonic sensor and the oscillation signal data of the vibration sensor is as follows:

[0051] First, inject a first DC excitation into the high-voltage winding side of the transformer. The first DC excitation voltage is 20% of the rated voltage of the high-voltage side of the transformer. After the system stabilizes, remove the first DC excitation, and obtain the signal F of the first acceleration sensor through the signal acquisition device 1s ;

[0052] Then, inject a second DC excitation into the low-voltage winding side of the transformer. The second DC excitation voltage is 20% of the rated voltage of the low-voltage side of the transformer. After the system stabilizes, remove the second DC excitation, and obtain the signal F of the second acceleration sensor through the signal acquisition device 2s ;

[0053] Next, use the ultrasonic sensor to obtain the ultrasonic signal F generated by the partial discharge of the transformer winding 3j , F 3j represents the ultrasonic signal obtained by the j-th ultrasonic sensor, and the data acquisition time of the j-th ultrasonic sensor is T j .

[0054] The process of processing the data is as follows:

[0055] The signal decomposition formulas of the acceleration sensor and the ultrasonic sensor are as follows:

[0056]

[0057] In the formula, g(x) is the original signal, g1(x) is the fundamental wave of the signal, g2(x), …, g n (x) is the 2nd to nth harmonics of the signal, n = 100;

[0058] Use formula (1) to perform frequency decomposition on F 3j to obtain the fundamental wave F 3j1 of the corresponding ultrasonic signal and the 2nd to nth harmonics F 3j2 , …, F 3jn ;

[0059] Use formula (1) to perform frequency decomposition on F 1s and F 2s to obtain the fundamental wave F 1s of F 1s1 and the 2nd to nth harmonics F 1s2 , …, F 1sn , and obtain the fundamental wave F 2s of F 2s1 and the 2nd to nth harmonics F 2s2 , …, F 1sn .

[0060] Step 3: Obtain the characteristic parameters for evaluating the state of the transformer winding.

[0061] The specific process of the said Step 3 is as follows:

[0062] S31, Calculate the total acceleration energy E 12 , and the calculation formula is as follows:

[0063]

[0064] In the formula, E 12 is the sum of the squares of the amplitudes of the first n harmonics of F 1s and F 2s ; F 1sj is the j'-th harmonic of F 1s , and F 2sj is the j'-th harmonic of F 2s .

[0065] S32, Calculate the total ultrasonic energy E3, and the calculation formula is as follows:

[0066]

[0067] In the formula, E3 is the sum of the squares of the amplitudes of the first n harmonics of F 3j ; F 3jk is the k-th harmonic of the j-th ultrasonic signal;

[0068] S33, Normalize the total acceleration energy E 12 :

[0069]

[0070] In the formula, E' 12 is the normalized total acceleration energy; E 12min is the minimum value in the total acceleration energy values; E 12max is the maximum value in the total acceleration energy values;

[0071] S34, Normalize the total ultrasonic energy E3:

[0072]

[0073] In the formula, E'3 is the normalized total ultrasonic energy; E 3min is the minimum value in the total ultrasonic energy values; E 3maX is the maximum value in the total ultrasonic energy values.

[0074] Step 4: Calculate the evaluation factor for the insulation state of the transformer winding.

[0075] The calculation formula for the evaluation factor λ of the insulation state of the transformer winding is:

[0076] λ = E′ 12 + E′3 (6).

[0077] Step Five: Evaluate the insulation status of the transformer winding based on the insulation status evaluation factor of the transformer winding.

[0078] The evaluation method for the insulation status of the transformer winding is as follows:

[0079] When 0 < λ ≤ 0.25, the insulation status of the transformer winding is good;

[0080] When 0.25 < λ ≤ 0.56, the insulation status of the transformer winding is average;

[0081] When λ > 0.56, there are problems with the insulation of the transformer winding, and corresponding repair or replacement measures need to be taken.

Claims

1. A method for evaluating the insulation status of transformer windings based on ultrasonic vibration dual modes, characterized in that: The following steps are involved: Step 1: Build a transformer winding insulation status evaluation test platform; Step 2: Conduct tests based on the transformer winding insulation status evaluation test platform to obtain the ultrasonic signal data of the ultrasonic sensor and the oscillation signal data of the vibration sensor and process the data; Step 3: Obtaining transformer winding state evaluation characteristic parameters; Step 4: Calculate the transformer winding insulation condition assessment factor; Step 5: Evaluate the insulation status of the transformer winding based on the transformer winding insulation status evaluation factor.

2. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual mode according to claim 1, characterized in that: In the step 1, the transformer winding insulation state evaluation test platform includes a transformer, a first acceleration sensor, a second acceleration sensor, a first ultrasonic sensor, a second ultrasonic sensor, a third ultrasonic sensor, a fourth ultrasonic sensor, a signal acquisition device, and a computer; the first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, and the fourth ultrasonic sensor are respectively installed at the inner center positions of the four sides of the transformer box, and the first acceleration sensor and the second acceleration sensor are respectively installed at the center positions of the top and bottom of the transformer box, and the signal output ends of the first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, the fourth ultrasonic sensor, the first acceleration sensor, and the second acceleration sensor are connected to the input end of the signal acquisition device, and the output end of the signal acquisition device is connected to the computer; the signal acquisition device receives the data collected by the first ultrasonic sensor, the second ultrasonic sensor, the third ultrasonic sensor, the fourth ultrasonic sensor, the first acceleration sensor, and the second acceleration sensor and sends them to the computer, and the computer records and processes the data.

3. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual mode according to claim 1, characterized in that: In step 2, the specific process of obtaining the ultrasonic signal data of the ultrasonic sensor and the oscillation signal data of the vibration sensor is as follows: First, a first DC excitation is injected into the high-voltage winding side of the transformer. The first DC excitation voltage is 20% of the rated voltage of the high-voltage side of the transformer. After the system is stable, the first DC excitation is removed and the signal F of the first acceleration sensor is obtained through the signal acquisition device. 1s ; Then, a second DC excitation is injected into the low-voltage winding side of the transformer, and the second DC excitation voltage is 20% of the rated voltage of the low-voltage side of the transformer. After the system is stable, the second DC excitation is removed, and the signal F of the second acceleration sensor is obtained through the signal acquisition device. 2s ; Next, an ultrasonic sensor is used to obtain the ultrasonic signal F generated by partial discharge of the transformer winding. 3j , F 3j represents the ultrasonic signal obtained by the jth ultrasonic sensor. The time of data collection of the jth ultrasonic sensor is T j .

4. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual mode according to claim 3 is characterized in that: In step 2, the process of processing the data is as follows: The decomposition formula of the acceleration sensor signal and the ultrasonic sensor signal is as follows: Where g(x) is the original signal, g1(x) is the fundamental wave of the signal, g2(x),…g n (x) is the 2nd to nth harmonic of the signal; Using formula (1) to calculate F 3j Perform frequency decomposition to obtain the fundamental wave F of the corresponding ultrasonic signal 3j1 and the 2nd to nth harmonics F 3j2 ,…,F 3jn ; Using formula (1) to calculate F 1s and F 2s Perform frequency decomposition and obtain F 1s The fundamental wave F 1s1 and the 2nd to nth harmonics F 1s2 ,…,F 1sn , and get F 2s The fundamental wave F 2s1 and the 2nd to nth harmonics F 2s2 ,…,F 1sn .

5. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual mode according to claim 4 is characterized in that: The specific process of step three is: S31, calculate the total acceleration energy E 12 , the calculation formula is as follows: Where E 12 F 1s With F 2s The sum of the squares of the amplitudes of the first n harmonics; F 1sj F 1s The j′th harmonic, F 2sj F 2s j′th harmonic of S32, calculate the total ultrasonic energy E3, the calculation formula is as follows: Where E3 is F 3j The sum of the squares of the amplitudes of the first n harmonics; F 3jk is the kth harmonic of the jth ultrasonic signal; S33, total energy of acceleration E 12 Normalize: Where E′ 12 is the normalized total acceleration energy; E 12min is the minimum value of the total acceleration energy; E 12max is the maximum value of the total energy value of acceleration; S34, normalize the total ultrasonic energy E3: Where E′3 is the normalized total ultrasonic energy; E 3min It is the minimum value of the total ultrasonic energy value; E 3maX It is the maximum value of the total ultrasonic energy.

6. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual mode according to claim 5, characterized in that: In step 4, the calculation formula of the transformer winding insulation state assessment factor λ is: λ=E′ 12 +E′3 (6)。 7. The method for evaluating transformer winding insulation status based on ultrasonic vibration dual modes according to claim 6, characterized in that: In step 5, the transformer winding insulation status is evaluated as follows: When 0<λ≤0.25, the transformer winding insulation is in good condition; When 0.25<λ≤0.56, the transformer winding insulation condition is general; When λ>0.56, there is a problem with the transformer winding insulation and appropriate maintenance or replacement measures need to be taken.

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