A method for evaluating the aging state of XLPE cable terminals based on ultrasonic response factors

Abstract

The present invention discloses a method for evaluating the aging state of XLPE cable terminals based on ultrasonic response factors, comprising the following steps: inputting an ultrasonic signal to the XLPE cable terminal and collecting the reflected wave at the XLPE cable terminal, recording the waveform amplitude and phase of the frequency-domain curve of the reflected wave at the cable terminal to be measured, calculating the absorption coefficient β of the cable to be measured, calculating the refractive coefficient δ of the cable to be measured, calculating the ultrasonic response factor η of the cable to be measured, and evaluating the insulation aging state of the XLPE cable terminal according to the ultrasonic response factor η. The beneficial effects of the present invention are as follows: by measuring the waveform amplitude and phase of the ultrasonic reflected wave of the XLPE cable terminal, calculating the absorption coefficient and refractive coefficient of the cable, and further calculating the ultrasonic response factor of the cable, the aging degree of the insulation of the XLPE cable terminal can be effectively evaluated. This method is efficient and convenient, and can accurately and online judge the aging condition of the insulation of the XLPE cable terminal operating for a long time. The evaluation result can provide guidance for the maintenance of the cable terminal and reduce power outage accidents.

Description

Technical Field

[0001] The present invention belongs to the field of aging state assessment of XLPE cable terminals, and particularly relates to a method for assessing the aging state of XLPE cable terminals based on ultrasonic response factors. Background Art

[0002] Due to its excellent electrical and physical-chemical properties, cross-linked polyethylene (XLPE) cables have developed rapidly in recent years and are widely used in power transmission and distribution networks, playing a crucial role in the power grid system. However, XLPE cables and their accessories have a closed structure, and it is relatively complex to detect defects. If not discovered, the situation will become increasingly difficult to repair over time. XLPE cables are prone to being affected by various external factors during use. Therefore, it is very necessary to study the insulation of XLPE cables. Therefore, reasonably evaluating the insulation state of XLPE cable terminals has important engineering significance and economic value.

[0003] The application object of the present invention is XLPE cable terminals. At present, some scholars have carried out research on the aging state of XLPE cable terminals. Relevant scholars have proposed cable aging diagnosis and evaluation methods based on partial discharge and signal injection. However, these methods are mainly used for the entire cable system and cannot evaluate the aging state of vulnerable components such as cable terminals. In summary, there is a need to propose an evaluation method based on multiple parameters to improve the accuracy of cable terminal aging state evaluation. This method is a method for assessing the aging state of XLPE cable terminals based on ultrasonic response factors. The operation method of this method is simple. By emitting and receiving the amplitude and phase of the ultrasonic wave waveform reflected by the cable terminal through an ultrasonic probe, the aging state degree of the XLPE cable terminal is evaluated based on the ultrasonic response factor. Summary of the Invention

[0004] The present invention is a method for assessing the aging state of XLPE cable terminals based on ultrasonic response factors, which can correctly evaluate the aging degree of long-term operating XLPE cable terminals.

[0005] The technical solution of the present invention is as follows:

[0006] Step 1: Input an ultrasonic signal to the XLPE cable terminal and collect the reflected wave at the XLPE cable terminal

[0007] Fix an ultrasonic sensor at the XLPE cable terminal to be measured, which is used to send ultrasonic waves to the XLPE cable terminal to be measured and receive the reflected wave at the XLPE cable terminal to be measured;

[0008] Step 2: Record the waveform amplitude and phase of the frequency-domain curve of the reflected wave at the cable terminal to be measured

[0009] Fourier transform the obtained reflected wave to obtain a frequency-domain curve, record the waveform amplitudes V1, V2, V3, V4, V5, V6 and phases A1, A2, A3, A4, A5, A6 at 100KHz, 200KHz, 300KHz, 400KHz, 500KHz, 600KHz within the frequency-domain curve, and denote the frequencies as f1, f2, f3, f4, f5, f6;

[0010] Step 3: Calculate the absorption coefficient of the cable terminal to be measured

[0011]

[0012] where V MAX is the maximum value among the waveform amplitudes, d is the thickness of the insulation layer at the test location of the XLPE cable terminal, unit: cm, is the average value of V1, V2, V3, V4, V5, V6 of the waveform amplitudes;

[0013] Step 4: Calculate the refraction coefficient of the cable to be measured

[0014]

[0015] where V Min is the minimum value among the waveform amplitudes;

[0016] Step 5: Calculate the ultrasonic response factor of the cable terminal to be measured

[0017]

[0018] Step 6: Evaluate the aging state of the cable terminal according to the ultrasonic response factor

[0019] If 0 ≤ η ≤ 0.74, the cable terminal to be measured is slightly aged;

[0020] If 0.74 < η ≤ 1.56, the cable terminal to be measured is moderately aged;

[0021] If η > 1.56, the cable terminal to be measured is severely aged.

[0022] The beneficial effects of the present invention are that by emitting and measuring the amplitudes and absorption ratios of ultrasonic waves with different frequencies after being transmitted through the cable terminal by an ultrasonic probe, calculating the absorption coefficient and refraction coefficient, and extracting the ultrasonic response factor to realize the aging degree evaluation of the XLPE cable terminal. The operation method of this method is simple and efficient, and can accurately evaluate the state of the XLPE cable terminal, which is beneficial to accurately mastering the insulation state of the cable terminal and has important significance for ensuring the safe and reliable operation of power cables. Description of the Drawings

[0023] Figure 1It is a flowchart of a method for evaluating the aging state of XLPE cable terminals based on ultrasonic response factors involved in the present invention; Detailed implementation manners

[0024] The present invention will be further described below in conjunction with the accompanying drawings and the specific implementation process.

[0025] The first step: Input an ultrasonic signal to the XLPE cable terminal and collect the reflected wave at the XLPE cable terminal

[0026] Fix an ultrasonic sensor at the XLPE cable terminal to be measured, which is used to send ultrasonic waves to the XLPE cable terminal to be measured and receive the reflected wave at the XLPE cable terminal to be measured;

[0027] The second step: Record the waveform amplitude and phase of the frequency-domain curve of the reflected wave at the cable terminal to be measured

[0028] Perform Fourier transform on the obtained reflected wave to obtain a frequency-domain curve, and record the waveform amplitudes V1, V2, V3, V4, V5, V6 and phases A1, A2, A3, A4, A5, A6 at 100KHz, 200KHz, 300KHz, 400KHz, 500KHz, 600KHz in the frequency-domain curve. Denote the frequencies as f1, f2, f3, f4, f5, f6;

[0029] The third step: Calculate the absorption coefficient of the cable terminal to be measured

[0030]

[0031] Wherein, V MAX is the maximum value in the waveform amplitudes, d is the thickness of the insulating layer at the test location of the XLPE cable terminal, unit: cm, is the average value of V1, V2, V3, V4, V5, V6 of the waveform amplitudes;

[0032] The fourth step: Calculate the refractive coefficient of the cable to be measured

[0033]

[0034] Wherein, V Min is the minimum value in the waveform amplitudes;

[0035] The fifth step: Calculate the ultrasonic response factor of the cable terminal to be measured

[0036]

[0037] The sixth step: Evaluate the aging state of the cable terminal according to the ultrasonic response factor

[0038] If 0≤η≤0.74, the cable terminal under test is mildly aged;

[0039] If 0.74 < η ≤ 1.56, the cable terminal under test is moderately aged;

[0040] If η > 1.56, the cable terminal under test is severely aged.

Claims

1. An XLPE cable terminal aging state evaluation method based on ultrasonic response factor, comprising the following steps: The first step: Input an ultrasonic signal to the XLPE cable terminal and collect the reflected wave at the XLPE cable terminal Fix an ultrasonic sensor at the XLPE cable terminal to be measured, which is used to send ultrasonic waves to the XLPE cable terminal to be measured and receive the reflected wave at the XLPE cable terminal to be measured; The second step: Record the waveform amplitude and phase of the frequency-domain curve of the reflected wave at the cable terminal to be measured Perform Fourier transform on the obtained reflected wave to obtain a frequency-domain curve, and record the waveform amplitudes V1, V2, V3, V4, V5, V6 and phases A1, A2, A3, A4, A5, A6 at 100KHz, 200KHz, 300KHz, 400KHz, 500KHz, 600KHz in the frequency-domain curve. Denote the frequencies as f1, f2, f3, f4, f5, f6; The third step: Calculate the absorption coefficient of the cable terminal to be measured Among them, V MAX is the maximum value in the waveform amplitude, d is the thickness of the insulation layer at the XLPE cable terminal test point, unit: cm, is the average value of V1, V2, V3, V4, V5, and V6 of the waveform amplitude; The fourth step: Calculate the refractive coefficient of the cable to be measured Among them, V Min is the minimum value in the waveform amplitude; The fifth step: Calculate the ultrasonic response factor of the cable terminal to be measured The sixth step: Evaluate the aging state of the cable terminal according to the ultrasonic response factor.

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