XLPE cable terminal aging state evaluation method based on ultrasonic response factor

Abstract

The invention discloses an XLPE cable terminal aging state evaluation method based on an ultrasonic response factor, and the method comprises the following steps: inputting an ultrasonic signal to an XLPE cable terminal, collecting a reflected wave at the XLPE cable terminal, recording the waveform amplitude and phase of a frequency domain curve of the reflected wave at the cable terminal to be detected, calculating the absorption coefficient beta of the cable to be detected, and calculating the aging state of the XLPE cable terminal. And calculating a refraction coefficient delta of the cable to be detected, calculating an ultrasonic response factor eta of the cable to be detected, and evaluating the insulation aging state of the XLPE cable terminal according to the ultrasonic response factor eta. The method has the advantages that by measuring the waveform amplitude and the phase of the ultrasonic reflected wave of the XLPE cable terminal, calculating the absorption coefficient and the refraction coefficient of the cable and further calculating the ultrasonic response factor of the cable, the insulation aging degree of the XLPE cable terminal can be effectively evaluated, and the method is efficient, convenient and high in practicability. And the aging condition of the XLPE cable terminal insulation in long-term operation can be accurately judged on line. The evaluation result can provide guidance for maintenance of the cable terminal, and power failure accidents are reduced.

Description

Technical Field

[0001] The invention belongs to the field of XLPE cable terminal aging state assessment, and in particular relates to an XLPE cable terminal aging state assessment method based on ultrasonic response factor. Background Art

[0002] Cross-linked polyethylene (XLPE) cables have been rapidly developed in recent years due to their excellent electrical and physical and chemical properties. They are widely used in power transmission and distribution networks and play a vital role in power grid systems. However, cross-linked polyethylene cables and their accessories are closed structures, and it is more complicated to detect defects. If they are not discovered, the situation will become increasingly difficult to repair over time. Cross-linked polyethylene cables are easily affected by various external factors during use, so it is necessary to study the insulation of cross-linked polyethylene cables. Therefore, it is of great engineering significance and economic value to reasonably evaluate the insulation status of XLPE cable terminals.

[0003] The application object of the present invention is XLPE cable terminals. At present, some scholars have carried out research on the aging status of XLPE cable terminals, and relevant scholars have proposed cable aging diagnosis and evaluation methods based on local discharge and signal injection, but these methods are mainly used for the entire cable system, and cannot evaluate the aging status of vulnerable parts such as cable terminals. In summary, it is necessary to propose an evaluation method based on multiple parameters to improve the accuracy of cable terminal aging status evaluation. This method is an XLPE cable terminal aging status evaluation method based on ultrasonic response factor. The method is simple to operate. The ultrasonic probe is used to transmit and receive the amplitude and phase of the ultrasonic waveform after reflection from the cable terminal, and the aging status of the XLPE cable terminal is evaluated based on the ultrasonic response factor. Summary of the invention

[0004] The invention provides an XLPE cable terminal aging state evaluation method based on ultrasonic response factor, which can correctly evaluate the aging degree of XLPE cable terminals in long-term operation.

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

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

[0007] The ultrasonic sensor is fixed at the terminal of the XLPE cable to be tested, so as to send ultrasonic waves to the terminal of the XLPE cable to be tested and receive reflected waves at the terminal of the XLPE cable to be tested;

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

[0009] Perform Fourier transform on the 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, and 600KHz in the frequency domain curve, and record the frequencies as f1, f2, f3, f4, f5, f6;

[0010] Step 3: Calculate the absorption coefficient of the cable terminal under test

[0011]

[0012] Among them, V MAX is the maximum value of the waveform amplitude, d is the thickness of the insulation layer at the terminal test of the XLPE cable, unit: cm, is the mean of the waveform amplitudes V1, V2, V3, V4, V5, and V6;

[0013] Step 4: Calculate the refractive index of the cable under test

[0014]

[0015] Among them, V Min is the minimum value of the waveform amplitude;

[0016] Step 5: Calculate the ultrasonic response factor of the cable terminal under test

[0017]

[0018] Step 6: Evaluate the cable terminal aging status based on the ultrasonic response factor

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

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

[0021] If η>1.56, the cable terminal under test is severely aged.

[0022] The beneficial effects of the present invention are that the ultrasonic probe is used to emit and measure the amplitude and absorption ratio of ultrasonic waveforms of different frequencies after being transmitted through the cable terminal, the absorption coefficient and the refractive coefficient are calculated, and the ultrasonic response factor is extracted to realize the aging degree evaluation of the XLPE cable terminal. The method is simple and efficient to operate, and can accurately evaluate the status of the XLPE cable terminal, which is conducive to accurately grasping the insulation status of the cable terminal, and is of great significance for ensuring the safe and reliable operation of the power cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1The present invention relates to a flow chart of an XLPE cable terminal aging state evaluation method based on ultrasonic response factor; DETAILED DESCRIPTION

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

[0025] Step 1: Input ultrasonic signal to the XLPE cable terminal and collect reflected wave at the XLPE cable terminal

[0026] The ultrasonic sensor is fixed at the terminal of the XLPE cable to be tested, so as to send ultrasonic waves to the terminal of the XLPE cable to be tested and receive reflected waves at the terminal of the XLPE cable to be tested;

[0027] Step 2: Record the waveform amplitude and phase of the frequency domain curve of the reflected wave at the terminal of the cable to be tested

[0028] Perform Fourier transform on the 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, and 600KHz in the frequency domain curve, and record the frequencies as f1, f2, f3, f4, f5, f6;

[0029] Step 3: Calculate the absorption coefficient of the cable terminal under test

[0030]

[0031] Among them, V MAX is the maximum value of the waveform amplitude, d is the thickness of the insulation layer at the terminal test of the XLPE cable, unit: cm, is the mean of the waveform amplitudes V1, V2, V3, V4, V5, and V6;

[0032] Step 4: Calculate the refractive index of the cable under test

[0033]

[0034] Among them, V Min is the minimum value of the waveform amplitude;

[0035] Step 5: Calculate the ultrasonic response factor of the cable terminal under test

[0036]

[0037] Step 6: Evaluate the cable terminal aging status based on the ultrasonic response factor

[0038] If 0≤η≤0.74, the tested cable terminal is slightly aged;

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

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

Claims

1. A method for evaluating the aging state of XLPE cable terminals based on ultrasonic response factor, comprising the following steps: Step 1: Input ultrasonic signal to the XLPE cable terminal and collect reflected wave at the XLPE cable terminal The ultrasonic sensor is fixed at the terminal of the XLPE cable to be tested, so as to send ultrasonic waves to the terminal of the XLPE cable to be tested and receive reflected waves at the terminal of the XLPE cable to be tested; Step 2: Record the waveform amplitude and phase of the frequency domain curve of the reflected wave at the terminal of the cable to be tested Perform Fourier transform on the 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, and 600KHz in the frequency domain curve, and record the frequencies as f1, f2, f3, f4, f5, f6; Step 3: Calculate the absorption coefficient of the cable terminal under test Among them, V MAX is the maximum value of the waveform amplitude, d is the thickness of the insulation layer at the terminal test of the XLPE cable, unit: cm, is the mean of the waveform amplitudes V1, V2, V3, V4, V5, and V6; Step 4: Calculate the refractive index of the cable under test Among them, V Min is the minimum value of the waveform amplitude; Step 5: Calculate the ultrasonic response factor of the cable terminal under test Step 6: Evaluate the cable terminal aging status based on the ultrasonic response factor.

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