Local defect aging diagnosis and evaluation method for power cable

A technology for local defects and power cables, applied in the direction of measuring resistance/reactance/impedance, measuring electrical variables, instruments, etc., to reduce the amount of calculation, reduce the difficulty of calculation, and improve the probability of successful calculation

Active Publication Date: 2021-08-20

JIANGSU ELECTRIC POWER CO

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AI-Extracted Technical Summary

Problems solved by technology

[0005] The present invention provides a local defect aging diagnosis and evaluation method for power c...

Method used

By calculating the size of the absolute value of the reflection coefficient of different defect positions, the insulation aging degree of local weak defects has been effectively quantitatively judged;

[0104] The optimization algorithm is used to calculate each local ...

Abstract

The invention relates to the technical field of power cables, and particularly discloses a local defect aging diagnosis method for a power cable, and the method comprises the steps: S100, calculating the reflection coefficient of the head end of the power cable; S200, processing the reflection coefficient of the head end of the power cable to obtain a position vector of each local defect of the power cable; S300, calculating each local defect parameter of the power cable according to the position vector of each local defect of the power cable; and S400, diagnosing and evaluating the local defect aging degree of the power cable according to each local defect parameter of the power cable. The local defect aging diagnosis method for the power cable provided by the invention can be used to simply and effectively diagnose local weak defect aging of the power cable.

Application Domain

Resistance/reactance/impedenceFault location

Technology Topic

Control theoryPower cable +1

Image

Examples

Experimental program(2)

Example Embodiment

[0106] Example 1

[0107] The measured power cable for the present embodiment is 1000M Zr-YJV02 8.7 / 15 3 * 95mm2 power cable, and the impedance is 1 kΩ in 300 m locations.

[0108] This embodiment uses the Agilent E5061B vector network analyzer to test the heading input impedance of the test cable.

[0109] This embodiment is provided for a local defective aging diagnosis method for a power cable, such as figure 2 As shown, including the following steps:

[0110] S10, frequency domain parameter test calculation

[0111] Setting the vector network analyzer is [10kHz, 5MHz], set the number of sweep points n to 1001 and input impedance Z in the first end of the power cable. in (f) Test, then calculate the reflection coefficient γ in the first end of the cable in (f):

[0112]

[0113] Calculated cable first end reflection coefficient γ in (f) image 3 Indicated. Where f is the scan frequency point; z 0 In order to use the same model, the same batch of 10M long reference cable measured the obtained characteristic impedance.

[0114] S20, using conversion functions f → t 'will result in (f) Perform a conversion to obtain a T 'domain signal γ in (t '), then γ in (t ') Perform a gamma to the BLACKMAN window fast Fourier transform (FFT) in (t ') spectrum FFT [γ in (t ')] Figure 4 The spectrum absorbing is normalized (the figure is normalized).

[0115] S30, observation Figure 4 Can know FFT [γ in (t ')] There is a position that can be characterized as partial weak defect point, and the local micro defect position is 300m.

[0116] S40, partial weak defect parameters calculation

[0117] S41, order to analyze local weak defect position L c 300M, then utilize formula γ ' in (f) = real (γ in (f)) · EXP (2α (f) L c ) Calculate reflection coefficient parameters γ ' in (f). Among them, REAL (·) is a complex real part; Exp (·) is an exponential function; α (f) is a decay constant measured by using the same model, the same batch of 10m long reference cable measurement.

[0118] S42, using conversion functions f → t 'will result in γ' in (f) Convert to obtain T 'domain signal γ' in (t '), then γ' in (t ') performs γ' for the addition of Blackman window FFT processing in (t ') spectrum FFT [γ' in (t ')] Figure 5 The gray solid line is shown.

[0119] S43, record FFT [γ ' in (t ')] China's weak defect position L c Signal intensity a c , Then use formula γ ' c1 (f) = γ ' in (f) -A c · COS (4πL c F / v (f)) / f w And γ ' c2 (f) = γ ' in (f) + a c · COS (4πL c F / v (f)) / f w Calculate γ ' c1 (f) and γ ' c2 (f). Where cos (·) is a cosine function; V (f) is the phase speed obtained by using the same model, the same number of 10m long reference cable measurements, F w Indicates the DC component size of the corresponding Blackman window function.

[0120] S44, using conversion functions f → t 'will result in γ' c1 (f) and γ ' c2 (f) Convert to obtain T 'domain signal γ' c1 (t ') and γ' c2 (t '), then γ' c1 (t ') and γ' c2 (t ') is performed by adding Blackman window FFT processing to obtain γ' c1 (t ') and γ' c2 (t ') spectrum FFT [γ' c1 (T ')] and FFT [γ' c2 (t ')] Figure 5 The black solid line and gray dotted line are shown.

[0121] S45, record FFT [γ ' c1 (T ')] and FFT [γ' c2 (t ')] Signal intensity A' at 300m in the middle local part c1 A ' c2 , Compare A ' c1 A ' c2 With a c the size of. Depend on Figure 5 Can know min {a ' c1 A ' c2 } = 0.07A c Max {a ' c1 A ' c2 } = 2A c Meet min {a ' c1 A ' c2 } ≤0.3a c And Max {a ' c1 A ' c2 } ≥1.7a c Therefore, the starting point of the defect is 300m, and the length of the defect is not 0m, and due to A ' c1 A ' c2 Therefore, the reflection coefficient of 300M position corresponds to defects ρ c = -A c / F w = -0.011. Where min (·) is the minimum; max (•) is the maximum.

[0122] S50, local micro-defect aging diagnostic assessment

[0123] Using the absolute value of the reflection coefficient to perform the local weak defects of different locations, the insulation aging state is evaluated. Since the partial weak defect reflection coefficient is 0.011, the defective aging state is medium.

[0124] At the same time, due to the partial weak defect reflection coefficient ρ c = -A c / F w = -0.011 less than zero and the defect length is 0m, so the reflection of the local weak defect is negative, at which time the defect is a parallel impedance type defect or Z 0 Reduce type defects are the same as the actual defect type.

[0125] In order to demonstrate the accuracy of the judgment, the cable is tested using the time domain reflection method (TDR) to obtain the test results. Image 6 Indicated. Depend on Image 6 It can be seen that there is a pulse waveform having a negative reflection polar in the 300m position in the TDR test result, whereby the above method can accurately determine the reflection polarity of the local weak defect of the cable.

Example Embodiment

[0126] Example 2

[0127] The measured power cable for this embodiment is a 1000M Zr-YJV02 8.7 / 153 * 95 mm2 power cable, and there is a local weak defect in the 400m position.

[0128] This embodiment uses the Agilent E5061B vector network analyzer to test the heading input impedance of the test cable.

[0129] This embodiment is provided for a local defective aging diagnosis method for a power cable, such as figure 2 As shown, including the following steps:

[0130] S10, frequency domain parameter test calculation

[0131] Set the vector network analyzer's sweep range [10kHz], set the number of sweep points n to 1001 and input impedance Z in the first end of the cable in (f) Test, then calculate the reflection coefficient γ in the first end of the cable in (f):

[0132]

[0133] Where f is the scan frequency point; z 0 In order to use the same model, the same batch of 10M long reference cable measured the obtained characteristic impedance.

[0134] S20, using conversion functions f → t 'will result in (f) Perform a conversion to obtain a T 'domain signal γ in (t '), then γ in (t ') Performing a BLACKMAN window fast Fourier transform (FFT) treatment to get γ in (t ') spectrum FFT [γ in (t ')].

[0135] S30, from γ in (t ') spectrum FFT [γ in (t ')] It can be seen that there is a position that can be characterized as a local micro defect point, and the local weak defect position is 400.4711 m.

[0136] S40, partial weak defect parameters calculation

[0137] S41, order to analyze local weak defect position L c Take 400.4711m, then utilize formula γ ' in (f) = real (γ in (f)) · EXP (2α (f) L c ) Calculate reflection coefficient parameters γ ' in (f). Among them; REAL (·) is a plurality of real part; Exp (·) is an index function; α (f) is the attenuation constant obtained by using the same model, the same batch of 10m long reference cable measurement.

[0138] S42, using conversion functions f → t 'will result in γ' in (f) Convert to obtain T 'domain signal γ' in (t '), then γ' in (t ') performs γ' for the addition of Blackman window FFT processing in (t ') spectrum FFT [γ' in (t ')] Figure 7 The gray solid line is shown.

[0139] S43, record FFT [γ ' in (t ')] China's weak defect position L c Signal intensity a c , Then use formula γ ' c1 (f) = γ ' in (f) -A c · COS (4πL c F / v (f)) / f w And γ ' c2 (f) = γ ' in (f) + a c · COS (4πL c F / v (f)) / f w Calculate γ ' c1 (f) and γ ' c2 (f). Where cos (·) is a cosine function; V (f) is the phase speed obtained by using the same model, the same number of 10m long reference cable measurements, F w Indicates the DC component size of the corresponding window function.

[0140] S44, using conversion functions f → t 'will result in γ' c1 (f) and γ ' c2 (f) Convert to obtain T 'domain signal γ' c1 (t ') and γ' c2 (t '), then γ' c1 (t ') and γ' c2 (t ') is performed by adding Blackman window FFT processing to obtain γ' c1 (t ') and γ' c2 (t ') spectrum FFT [γ' c1 (T ')] and FFT [γ' c2 (t ')] Figure 7 The black solid line and gray dotted line are shown.

[0141] S45, record FFT [γ ' c1 (T ')] and FFT [γ' c2 (t ')] Signal intensity a' at a micro-defect position 400.4711m c1 A ' c2 , Compare A ' c1 A ' c2 With a c the size of. Depend on Figure 7 Can know min {a ' c1 A ' c2 } = 1.43A c Max {a ' c1 A ' c2 } = 1.46A c Not satisfying min {a ' c1 A ' c2 } ≤0.3a c And Max {a ' c1 A ' c2 } ≥1.7a c. Where min (·) is the minimum; max (•) is the maximum.

[0142] S46, assuming that the local weak defect length is 1m, let G x (l x 1M, ρ x ) | f for:

[0143] G x (l x 1M, ρ x ) | f = Γ ' in (f) -ρ x · COS (4πL x F / v (f)) + ρ x · (1-ρ x 2 ) · COS (4π (L) x +1) · f / v (f)))

[0144] Where L x To be optimized, the local weak defect start position, the value range is [384.4711m, 416.4711M]; ρ x For the preferred reflection coefficient, the value range is [-0.5, 0.5].

[0145] S47, using conversion functions f → t 'will get G x (l x 1M, ρ x ) | f Convert to get the T 'domain signal G x (l x 1M, ρ x ) | t′ , Then use intelligent optimization algorithms to L x Ρ x Perform G x (l x 1M, ρ x ) | t′ The global optimization of the signal amplitude at 400.4711m after the BLACKMAN window FFT was added, and the starting position and reflection coefficient of the local micro-defect at 400.4711 m were solved were 399.9974 m and -0.05, respectively.

[0146] S50, local micro-defect aging diagnostic assessment

[0147] Using the absolute value of the reflection coefficient to perform an insulating aging state of the partial weak defects of different locations, since the partial weak defect reflection coefficient is 0.05, the defective aging state is medium.

[0148] At the same time, since the local weak defect reflection coefficient is less than zero and the defect length is 1m, the reflection at the local weak defect is negative, and the defect is Z 0 Reduce type defects.

[0149] In order to prove the accuracy of the judgment result, the cable is tested using TDR to obtain the test results. Figure 8 Indicated. Depend on Figure 8 It can be seen that there is a pulse waveform of the 400m in the TDR test result in the first negative positive pulse waveform, whereby the above method can accurately determine the reflection polarity of the local weak defect of the cable.

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Classification and recommendation of technical efficacy words

small amount of calculation
Reduce computational difficulty

Local defect aging diagnosis and evaluation method for power cable

A technology for local defects and power cables, applied in the direction of measuring resistance/reactance/impedance, measuring electrical variables, instruments, etc., to reduce the amount of calculation, reduce the difficulty of calculation, and improve the probability of successful calculation

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

Image

Examples

Example Embodiment

Example Embodiment

PUM

Description & Claims & Application Information

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