Device and method for detecting defect repair effect of buffer layer of high-voltage cable

Abstract

The invention relates to a high-voltage cable buffer layer defect repair effect detection device and method.The detection device comprises a power module, an electrode module, an acquisition module and a control module, the power module and the acquisition module are connected with a buffer layer of a high-voltage cable in series through the electrode module, and the acquisition module transmits obtained information to the control module; the acquisition module comprises an acquisition module 1 and an acquisition module 2. The detection method comprises overall detection and local detection, wherein the electrode module is connected to an insulation shielding layer and a metal sheath of the high-voltage cable according to an actual test position; for overall detection, the power supply module is connected with the acquisition module 1, and the ablation condition of the buffer layer is quantitatively described by defining the change rate of the contact resistance; and for local detection, the power supply module is connected with the acquisition module 2, a comparison signal is processed through integral transformation, a repair rate is further calculated, and detection and evaluation of an ablation defect repair effect are realized by combining results of overall detection and local detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage cable maintenance, and more specifically, relates to a detection device and method for the repair effect of high-voltage cable buffer layer defects. Background Technique

[0002] As an important medium between the metal sheath and the outer semi-conductive layer of high-voltage and extra-high-voltage cross-linked polyethylene power cables, the buffer layer is mainly used to achieve longitudinal water-blocking of the cable and buffer the mechanical stress generated during cable bending and insulation thermal expansion. In recent years, high-voltage cable breakdown accidents have occurred in many places in China. After disassembling the accident cables, it was found that there were defects such as white spots on the buffer layer, and the number of defects at the breakdown positions was relatively large. The existence of defects will affect the conductivity of the buffer layer, and further development may damage the main insulation of the cable, resulting in cable accidents and endangering the safe and stable operation of the power grid.

[0003] At present, although certain progress has been made in cable buffer layer repair technology, there are still key problems: there is a lack of reliable detection and evaluation means for the repair effect of defects. This makes it difficult to accurately measure the gap between the actual performance of the repaired cable and the expected effect, and the quality and reliability of the repair work cannot be fully verified. In view of this, it is urgent to develop a set of accurate and effective detection devices and methods for the repair effect of high-voltage cable buffer layer defects. This not only helps to improve the high-voltage cable repair technology system, but also has crucial significance for ensuring the stable and economic operation of the cable system and enhancing the reliability of power transmission. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to overcome the above technical problems, the present invention provides a detection device and method for the repair effect of high-voltage cable buffer layer defects, so as to realize the evaluation of the repair effect of high-voltage cable buffer layer defects.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a detection device for the repair effect of a high-voltage cable buffer layer, which includes a power supply module, an electrode module, a collection module, and a control module. The power supply module and the collection module are connected in series with the buffer layer of the high-voltage cable through the electrode module, and the collection module transmits the obtained information to the control module; the power supply module includes a DC power supply, a swept-frequency signal transmitter, and a current-limiting resistor. One end of the power supply module is connected to the electrode module, and the other end of the power supply module is connected to the collection module; the electrode module includes two measurement electrodes, electrode 1 and electrode 2. Electrode 1 is connected to the collection module and the insulation shield layer of the high-voltage cable, and electrode 2 is connected to the power supply module and the metal sheath of the high-voltage cable; the collection module includes collection module 1 and collection module 2. Collection module 1 includes a reference resistor and an ammeter connected in series; collection module 2 includes a power splitter, a coupler, and a data comparison module; collection module 1 and collection module 2 are connected to the power supply module through a single-pole double-throw switch.

[0006] The swept-frequency voltage amplitude range of the swept-frequency signal transmitter is 1 - 50V, the frequency is 1 - 100MHz, and the voltage range of the DC power supply is 0 - 500V.

[0007] The electrode module includes a measurement electrode and an electrode fixing fixture. The measurement electrode contacts the measurement position of the high-voltage cable through the electrode fixing fixture. The measurement positions of the high-voltage cable include the intermediate window opening position during cable repair and both ends of the cable.

[0008] The power splitter is used to equally divide the transmitted signal of the swept-frequency signal transmitter. One part is transmitted to the insulation shield layer of the high-voltage cable through the coupler, and the other part is directly transmitted to the data comparison module. The coupler is used to separate the transmitted signal of the swept-frequency signal transmitter and the reflected signal of the insulation shield layer, and transmit the reflected signal of the insulation shield layer to the data comparison module. The data comparison module is used to obtain the ratio of the reflected signal to the transmitted signal.

[0009] The transmitted signal of the swept-frequency signal transmitter is a sine wave signal.

[0010] The range of the reference resistor is 10Ω - 500kΩ.

[0011] The control module is connected to a computer. The control module is used to control the collection module and the power supply module, thereby changing the test parameters, and the control module is used to process the collected signals and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

[0012] A detection method for the repair effect of a high-voltage cable buffer layer defect of the present invention uses the detection device for the repair effect of a high-voltage cable buffer layer defect described above. The detection method includes overall detection and local detection, and includes the following steps:

[0013] Step 1: Cut off the power supply of the high-voltage cable;

[0014] Step 2: Connect the electrode module to the insulating shield layer and the metal sheath of the high-voltage cable according to the actual test position;

[0015] Step 3: For overall detection, first set the magnitude of the DC voltage and the magnitude of the reference resistance in the power supply module, and connect the power supply module to the acquisition module 1. The power supply module starts to measure, and the acquisition module collects data and transmits it to the control module;

[0016] For local detection, first set the magnitude and frequency of the swept-frequency signal voltage in the power supply module, and connect the power supply module to the acquisition module 2. The power supply module emits a sinusoidal swept-frequency signal and starts to measure, and the acquisition module collects data and transmits it to the control module.

[0017] In Step 2, select the electrode fixing fixture and electrode according to the actual test position: When the test position is the middle window position during cable repair, the cable at this position is cut to the insulating shield. Electrode 1 of the electrode module is fixed to the insulating shield layer of the high-voltage cable through a circular fixture or copper foil, and electrode 2 of the electrode module is fixed to the metal sheath through an alligator clip; If the test position is at both ends of the cable, electrode 1 and electrode 2 of the electrode module are respectively fixed to the insulating shield layer and the metal sheath of the high-voltage cable through alligator clips.

[0018] In Step 3, for overall testing, the contact resistances r1 and r2 before and after the buffer layer repair are calculated respectively by formula (1):

[0019]

[0020] In formula (1), r is the contact resistance of the cable buffer layer, I is the measured current, U is the DC power supply, and R 参考 is the resistance value of the reference resistance;

[0021] By comparing the change effect of the buffer layer contact resistance, the ablation defect situation is indirectly reflected, and the ablation situation of the buffer layer is quantitatively described by defining the change rate of the contact resistance:

[0022]

[0023] For local testing, the comparison signal is processed by the method of integral transformation, and the integral change formulas of the comparison signal before and after repair are respectively (3) and (4):

[0024]

[0025] The ratio of the reflected signal to the transmitted signal is denoted as the comparison signal, where Q b (f) and Q a(f) are the comparison signals before and after the repair of the high-voltage cable buffer layer, Z(f, x) is the kernel function of the integral transform, and it is e -2γx , γ is the propagation constant; in the formula, the highest frequency of the swept-frequency signal is f max , and the lowest frequency is f min ; x is any position on the buffer layer of the test section (0 ≤ x ≤ l), and l is the total length of the buffer layer of the test section;

[0026] Further calculation gives the repair rate DT(x) as follows:

[0027]

[0028] The ablation repair effect of the buffer layer is evaluated according to the change rate of contact resistance Δr before and after repair and the repair rate DT(x). The repair effects include the following levels: if the change rate of contact resistance is less than 60%, it is directly determined that the repair effect is poor; if the change rate of contact resistance is greater than or equal to 60% and the repair rate is higher than 85%, it is excellent; if the change rate of contact resistance is greater than or equal to 60% and the repair rate is between 85% and 55%, it is medium; if the change rate of contact resistance is greater than or equal to 60% and the repair rate is less than 55%, it is poor.

[0029] The beneficial effect of the present invention is that a detection device and method for the repair effect of high-voltage cable buffer layer defects of the present invention can detect the whole high-voltage cable buffer layer and can also detect local defect parts of the high-voltage cable buffer layer. On the one hand, through the measurement of resistance, the overall repair situation of the buffer layer is obtained; on the other hand, the repair situation of each position of the buffer layer is obtained, and the positions with poor repair effects can be obtained and repaired in time. Combining the results of overall detection and local detection, the detection and evaluation of the ablation defect repair effect are realized, and the quality and reliability of the repair work are fully verified. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the drawings and embodiments.

[0031] Figure 1 is a schematic diagram of the detection device for the repair effect of high-voltage cable buffer layer defects of the present invention.

[0032] Figure 2 is the integral result diagram of the comparison signal in the embodiment of the present invention.

[0033] Figure 3 is the repair rate result diagram in the embodiment of the present invention.

[0034] Figure 1 In, 1, conductor; 2, conductor shielding layer; 3, insulating layer; 4, insulating shielding layer; 5, buffer layer; 6, metal sheath; 7, outer sheath. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic manner, so they only show the components related to the present invention.

[0036] As Figure 1 shown, a detection device for the repair effect of the buffer layer defect of a high-voltage cable according to the present invention includes a power supply module, an electrode module, a collection module, and a control module. The power supply module and the collection module are connected in series with the buffer layer of the high-voltage cable through the electrode module, and the collection module transmits the obtained information to the control module. The power supply module includes a DC power supply, a sweep signal transmitter, and a current-limiting resistor. One end of the power supply module is connected to the electrode module, and the other end of the power supply module is connected to the collection module. The electrode module includes two measurement electrodes, electrode 1 and electrode 2. Electrode 1 is connected to the collection module and the insulation shield layer of the high-voltage cable, and electrode 2 is connected to the power supply module and the metal sheath of the high-voltage cable. The collection module includes collection module 1 and collection module 2. Collection module 1 includes a reference resistor and an ammeter connected in series, and the ammeter measures the current flowing through the reference resistor. Collection module 2 includes a power divider, a coupler, and a data comparison module. Collection module 1 and collection module 2 are connected to the power supply module through a single-pole double-throw switch.

[0037] The sweep voltage amplitude range of the sweep signal transmitter is 1 - 50V, the frequency is 1 - 100MHz, and the voltage range of the DC power supply is 0 - 500V. The transmitted signal of the sweep signal transmitter is a sine wave signal. The range of the reference resistor is 10Ω - 500kΩ.

[0038] The electrode module includes a measurement electrode and an electrode fixing fixture. The measurement electrode contacts the measurement position of the high-voltage cable through the electrode fixing fixture. The measurement positions of the high-voltage cable include the intermediate window position during cable repair and both ends of the cable. According to different measurement positions, the electrode fixing fixture is different. During the test, the electrode module only plays a connecting role, and the power supply module and the collection module are connected in series with the buffer layer of the high-voltage cable through the electrode module.

[0039] The power divider is used to equally divide the transmitted signal of the sweep signal transmitter. One part is transmitted to the insulation shield layer of the high-voltage cable through the coupler, and the other part is directly transmitted to the data comparison module. The coupler is used to separate the transmitted signal of the sweep signal transmitter and the reflected signal of the insulation shield layer, and transmit the reflected signal of the insulation shield layer to the data comparison module. The data comparison module is used to obtain the ratio of the reflected signal to the transmitted signal.

[0040] The control module is connected to a computer. The control module is used to control the acquisition module and the power supply module, thereby changing the test parameters, including the test voltage type, the connection of the acquisition module, and the size of the reference resistance. In addition, the control module is used to process the acquired signals and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

[0041] A method for detecting the repair effect of a high-voltage cable buffer layer defect of the present invention, using a device for detecting the repair effect of a high-voltage cable buffer layer defect. The detection method includes overall detection and local detection, and includes the following steps:

[0042] Step 1: Cut off the power supply of the high-voltage cable;

[0043] Step 2: Connect the electrode module to the insulating shield layer and the metal sheath of the high-voltage cable according to the actual test position;

[0044] For overall detection, first set the magnitude of the DC voltage and the magnitude of the reference resistance in the power supply module, and connect the power supply module to acquisition module 1. The power supply module starts to measure, and the acquisition module acquires data (the current of the reference resistance) and transmits it to the control module;

[0045] For local detection, first set the magnitude and frequency of the swept-frequency signal voltage in the power supply module, and connect the power supply module to acquisition module 2. The power supply module emits a sine swept-frequency signal and starts to measure, and the acquisition module acquires data (the comparison signal, and the ratio of the reflected signal to the transmitted signal is recorded as the comparison signal) and transmits it to the control module.

[0046] For the measurement positions of the high-voltage cable in overall detection and local detection, the cable head or the intermediate windowing position during the repair of the cable buffer layer can be selected according to actual needs. The overall detection measures the resistivity, understanding the buffer layer as a whole; for local detection, the test results can show the specific conditions of different parts of the buffer layer. Each time of detection, the measurement positions of overall detection and local detection are the same.

[0047] In step 2, select the electrode fixing fixture and the electrode according to the actual test position: when the test position is the intermediate windowing position during cable repair, the cable at this position is cut to the insulating shield. Electrode 1 of the electrode module is fixed to the insulating shield layer of the high-voltage cable through a circular fixture or copper foil, and electrode 2 of the electrode module is fixed to the metal sheath through an alligator clip; if the test position is at both ends of the cable, electrode 1 and electrode 2 of the electrode module are respectively fixed to the insulating shield layer and the metal sheath of the high-voltage cable through alligator clips.

[0048] In step 3, for overall testing, the contact resistances r1 and r2 before and after the repair of the buffer layer are calculated respectively by formula (1):

[0049]

[0050] In formula (1), r is the contact resistance of the cable buffer layer, I is the measured current, U is the DC power supply, and R 参考 is the resistance value of the reference resistor;

[0051] By comparing the change effect of the buffer layer contact resistance, the ablation defect situation is indirectly reflected, and the ablation situation of the buffer layer is quantitatively described by defining the contact resistance change rate:

[0052]

[0053] For local testing, the comparison signal is processed by the method of integral transform. The integral transforms that can be used include Fourier transform, Laplace transform, and Z transform. The integral change formulas of the comparison signal before and after repair are (3) and (4) respectively:

[0054]

[0055] The ratio of the reflected signal to the transmitted signal is denoted as the comparison signal. In the formula, Q b (f) and Q a (f) are the comparison signals before and after the repair of the high-voltage cable buffer layer respectively, Z(f, x) is the kernel function of the integral transform, and is e -2γx , γ is the propagation constant; in the formula, the highest frequency of the swept-frequency signal is f max and the lowest frequency is f min ; x is any position on the buffer layer of the test section (0 ≤ x ≤ l), and l is the total length of the buffer layer of the test section;

[0056] Furthermore, the repair rate DT(x) is calculated as follows, and its formula is as follows:

[0057]

[0058] When evaluating, first draw the curves of T b (x) and T a (x), and then draw the curve of DT(x). The integral results of T b (x) and T a (x) at non-defect positions are the same. After subtracting the two, the value of DT(x) should be approximately 0; while at the ablation defect, the value of DT(x) before and after repair will be significantly greater than 0, which appears as a bulge significantly higher than the x-axis in the positioning map.

[0059] The repair effect of the buffer layer ablation is evaluated according to the change rate Δr of the contact resistance before and after repair and the repair rate DT(x). The repair effect includes the following grades: If the change rate of the contact resistance is less than 60%, the repair effect is directly judged to be poor; if the change rate of the contact resistance is greater than or equal to 60% and the repair rate is higher than 85%, it is excellent; if the change rate of the contact resistance is greater than or equal to 60% and the repair rates are all between 85% and 55%, it is medium; if the change rate of the contact resistance is greater than or equal to 60% and the repair rate is less than 55%, it is poor.

[0060] Embodiment

[0061] In the laboratory, taking a 110 kV retired high-voltage cable as an example, a section of it is taken for analysis, with a length of l = 40 m. As Figure 1 shown, the high-voltage cable from the inside out is successively a conductor 1, a conductor shielding layer 2, an insulating layer 3, an insulating shielding layer 4, a buffer layer 5, a metal sheath 6, and an outer sheath 7.

[0062] Using the detection device of the present invention, electrode 1 is connected to the acquisition module and the insulating shielding layer 4, electrode 2 is connected to the power supply module and the metal sheath 6, and the actual test position of the cable connected by electrode 1 and electrode 2 is the cable head end. According to the detection method of the present invention, during local detection, the voltage of the swept-frequency signal in the power supply module is set to 5 V and the frequency range is 1 - 80 MHz through the control module, and the power supply module is connected to the acquisition module 2. The power supply module emits a sine swept-frequency signal and starts measurement, and the acquisition module acquires the comparison signal and transmits it to the control module. The local test results are as Figure 2 and 3 shown. It can be found through analysis that the minimum repair rate is above 85%.

[0063] During overall detection, the DC voltage in the power supply module is set to 50 V and the reference resistance is 50 Ω through the control module, and the power supply module is connected to the acquisition module 1. The power supply module starts measurement, and the acquisition module acquires the current of the reference resistance and transmits it to the control module. The overall test results are shown in Table 1, and the change rate of the contact resistance is calculated to be 87% after calculation. Thus, the repair effect of the buffer layer ablation can be determined.

[0064] The repair effect includes the following grades: If the change rate of the contact resistance is less than 60%, the repair effect is directly judged to be poor; if the change rate of the contact resistance is greater than or equal to 60% and the repair rate is higher than 85%, it is excellent; if the change rate of the contact resistance is greater than or equal to 60% and the repair rates are all between 85% and 55%, it is medium; if the change rate of the contact resistance is greater than or equal to 60% and the repair rate is less than 55%, it is poor. Therefore, it can be determined that the repair effect grade of the buffer layer ablation in this embodiment is excellent.

[0065] Table 1: Contact resistance test results in the invention embodiment

[0066]

[0067] Inspired by the above-described ideal embodiments of the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A detection device for the repair effect of a high-voltage cable buffer layer defect, characterized in that, It includes a power supply module, an electrode module, a collection module, and a control module. The power supply module and the collection module are connected in series with the buffer layer of the high-voltage cable through the electrode module, and the collection module transmits the obtained information to the control module; The power supply module includes a DC power supply, a sweep signal transmitter, and a current-limiting resistor. One end of the power supply module is connected to the electrode module, and the other end of the power supply module is connected to the collection module; The electrode module includes two measuring electrodes, electrode 1 and electrode 2. Electrode 1 is connected to the insulation shield layer of the high-voltage cable and the collection module, and electrode 2 is connected to the metal sheath of the power supply module and the high-voltage cable; The collection module includes collection module 1 and collection module 2. Collection module 1 includes a reference resistor and an ammeter connected in series; Collection module 2 includes a power divider, a coupler, and a data comparison module; Collection module 1 and collection module 2 are connected to the power supply module through a single-pole double-throw switch.

2. The high-voltage cable buffer layer defect repair effect detection device according to claim 1, characterized in that, The amplitude range of the sweep voltage of the sweep signal transmitter is 1 - 50V, the frequency is 1 - 100MHz, and the voltage range of the DC power supply is 0 - 500V.

3. The high-voltage cable buffer layer defect repair effect detection device according to claim 1, characterized in that The electrode module includes a measuring electrode and an electrode fixing clamp. The measuring electrode contacts the measuring position of the high-voltage cable through the electrode fixing clamp. The measuring positions of the high-voltage cable include the intermediate window position during cable maintenance and both ends of the cable.

4. The detection device for the repair effect of the buffer layer defect of the high-voltage cable according to claim 1, characterized in that, The power divider is used to equally divide the transmitted signal of the sweep signal transmitter. One part is transmitted to the insulation shield layer of the high-voltage cable through the coupler, and the other part is directly transmitted to the data comparison module. The coupler is used to separate the transmitted signal of the sweep signal transmitter and the reflected signal of the insulation shield layer, and transmit the reflected signal of the insulation shield layer to the data comparison module. The data comparison module is used to obtain the ratio of the reflected signal to the transmitted signal.

5. The high-voltage cable buffer layer defect repair effect detection device according to claim 1, characterized in that, The transmitted signal of the sweep signal transmitter is a sine wave signal.

6. The device for detecting the repair effect of the buffer layer defect of a high-voltage cable according to claim 1, characterized in that, The range of the reference resistor is 10Ω - 500kΩ.

7. The high-voltage cable buffer layer defect repair effect detection device according to claim 1, wherein The control module is connected to a computer. The control module is used to control the collection module and the power supply module, thereby changing the test parameters, and the control module is used to process the collected signals and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

8. A method for detecting the repair effect of defects in the buffer layer of a high-voltage cable, characterized in that, Using the detection device for the repair effect of the high-voltage cable buffer layer defect according to any one of claims 1 - 7, the detection method includes overall detection and local detection, and includes the following steps: Step 1: Cut off the power supply of the high-voltage cable; Step 2: Connect the electrode module to the insulation shield layer and the metal sheath of the high-voltage cable according to the actual test position; For overall detection, first set the magnitude of the DC voltage and the magnitude of the reference resistor in the power supply module, and connect the power supply module to collection module 1. The power supply module starts to measure, and the collection module collects data and transmits it to the control module; For local detection, first set the magnitude of the sweep signal voltage and the frequency in the power supply module, and connect the power supply module to collection module 2. The power supply module emits a sine sweep signal and starts to measure, and the collection module collects data and transmits it to the control module.

9. The method for detecting the repair effect of the buffer layer defect of a high-voltage cable according to claim 8, characterized in that, In Step 2, select the electrode fixing fixture and electrodes according to the actual test position: When the test position is the middle window opening position during cable repair, where the cable is cut to the insulation shield, Electrode 1 of the electrode module is fixed to the insulation shield of the high-voltage cable through a circular fixture or copper foil, and Electrode 2 of the electrode module is fixed to the metal sheath through an alligator clip; if the test position is at both ends of the cable, Electrode 1 and Electrode 2 of the electrode module are respectively fixed to the insulation shield and the metal sheath of the high-voltage cable through alligator clips.

10. The method for detecting the repair effect of the buffer layer defect of a high-voltage cable according to claim 8, wherein, In Step 3, for the overall test, the contact resistances r1 and r2 before and after the buffer layer repair are calculated respectively by formula (1): In Equation (1), r is the contact resistance of the cable buffer layer, I is the measured current, U is the DC power supply, and R 参考 is the resistance value of the reference resistance; By comparing the change effect of the buffer layer contact resistance, the ablation defect situation is indirectly reflected, and the ablation situation of the buffer layer is quantitatively described by defining the change rate of the contact resistance: For the local test, the comparison signals are processed by the method of integral transformation, and the integral change formulas of the comparison signals before and after repair are respectively formulas (3) and (4): The ratio of the reflected signal to the transmitted signal is denoted as the contrast signal, where Q b (f) and Q a (f) are the contrast signals before and after the repair of the buffer layer of the high-voltage cable respectively, Z(f, x) is the kernel function of the integral transform, and is e -2γx , γ is the propagation constant; in the formula, the highest frequency of the swept-frequency signal is f max , the lowest frequency is f min ; x is any position on the buffer layer of the test section (0 ≤ x ≤ l), and l is the total length of the buffer layer of the test section; Further calculate to obtain the repair rate DT(x) as follows: Evaluate the ablation repair effect of the buffer layer according to the change rate Δr of the contact resistance before and after repair and the repair rate DT(x).

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