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

Abstract

The invention belongs to the technical field of high-voltage cable overhaul and maintenance, and particularly relates to a high-voltage cable buffer layer ablation repair effect detection device and method.The detection device comprises a power module, an electrode module, an acquisition module and a control module, and the power module and the acquisition module are connected with a buffer layer of a high-voltage cable in series through the electrode module; the acquisition module transmits obtained information to the control module, and the acquisition module comprises a reference capacitor and a voltmeter test module. The detection method is based on a capacitance integration method, accurate and nondestructive detection is carried out on the cable buffer layer ablation defect repair effect, important technical support is provided for state evaluation of the cable buffer layer, and the method has wide application prospects in the field of electric power engineering.

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 ablation repair effect of a high-voltage cable buffer layer. Background Technique

[0002] In recent years, a new type of cable fault has occurred in 110 kV and above XLPE-insulated high-voltage cables in many places at home and abroad. The location of this fault does not occur in the accessories or XLPE insulation of the high-voltage cable, but in the buffer layer between the insulation shielding layer and the metal aluminum sheath of the high-voltage cable. After disassembling the faulty high-voltage cable, white powder and ablation marks are found on the outer surface of its insulation shielding layer, buffer layer, and the inner surface of the metal shielding layer. Such high-voltage cable faults have high latency. If problems are not detected and discovered in time, the faults may continue to deteriorate, causing the main insulation to break down and explode, and then leading to power outages in the urban power grid, resulting in huge economic and social impacts.

[0003] Studying the repair mechanism and finding a suitable buffer layer repair medium are of extremely important significance for carrying out research on buffer layer repair technology and have become a hot issue in the industry. At present, there are few state evaluation methods for the ablation repair effect of the cable buffer layer, and the existing evaluation methods cannot fully provide a good evaluation of the electrical performance repair effect of the buffer layer. Therefore, there is an urgent need to propose a detection device and method for the ablation repair effect of a high-voltage cable buffer layer to accurately and non-destructively detect the repair effect of cable buffer layer ablation defects. 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 ablation repair effect of a high-voltage cable buffer layer to provide a reference for the safe operation of high-voltage cables.

[0005] The technical solution adopted by the present invention to solve its technical problems is: A detection device for the ablation repair effect of a high-voltage cable buffer layer 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 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 shielding 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 a reference capacitor and a voltmeter test module. The voltmeter test module includes a voltmeter, and the voltmeter is connected in parallel with the reference capacitor. One end of the collection module is connected to the electrode module, and the other end of the collection module is connected to the power supply module.

[0006] The voltage range of the DC power supply is 0 to 5 kV.

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

[0008] The reference capacitance ranges from 1 uF to 10 uF.

[0009] 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. And the control module is used to calculate the acquired signals and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

[0010] A method for detecting the repair effect of the ablation of the high-voltage cable buffer layer according to the present invention uses the above-mentioned device for detecting the repair effect of the ablation of the high-voltage cable buffer layer. The detection method includes the following steps:

[0011] Step 1: Cut off the power supply of the high-voltage cable;

[0012] 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;

[0013] Step 3: After setting the voltage amplitude and the size of the reference capacitance in the power supply module, the power supply module starts to measure. The acquisition module acquires data and transmits it to the control module.

[0014] 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 insulation shield. Electrode 1 of the electrode module is fixed on the insulation shield layer of the high-voltage cable through a circular fixture or copper foil, and electrode 2 of the electrode module is fixed on 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 on the insulation shield layer and the metal sheath of the high-voltage cable through alligator clips.

[0015] In Step 3, the test time is 5 min - 10 min. Considering the construction site, if the measurement time is too long, it will become complicated and inefficient.

[0016] Preferably, in Step 3, the test time is 5 min.

[0017] In Step 3, the acquisition module acquires the reference capacitance voltage U(t). Through the following steps, the repair effect of the cable buffer layer ablation is evaluated:

[0018] 1) Test the ablated cables of the buffer layer before and after repair, and obtain the functions U1(t) and U2(t) of the reference capacitance voltage varying with time respectively;

[0019] 2) Since the capacitance value C of the reference capacitor is determined and known, calculate the functions Q1(t) and Q2(t) of the charge varying with time before and after repair respectively according to formula (1);

[0020] Q(t) = CU(t) (1)

[0021] 3) Based on the function Q(t) of the charge varying with time, calculate the current functions I1(t) and I2(t) before and after repair according to formula (2);

[0022]

[0023] 4) Take the average value of the current results over a period of time, and calculate the average currents I 1-ave (t) and I 2-ave (t) before and after repair according to formula (3); The period of time mentioned above is the first 120 s before the test end time t e ;

[0024]

[0025] 5) Calculate the current change rate ΔI through the average currents I 1-ave (t) and I 2-ave (t) before and after repair, and judge the repair effect of the buffer layer ablation according to the current change rate ΔI;

[0026]

[0027] The repair effect levels include three levels, namely excellent, medium and poor. Among them, the current change rate higher than 95% is excellent, the current change rate between 95% and 65% is medium, and the current change rate less than 65% is poor.

[0028] The beneficial effect of the present invention is that a detection device and method for the repair effect of the buffer layer ablation of a high-voltage cable according to the present invention are based on the capacitance integration method, with simple equipment, accurate and reliable implementation method, easy to implement, accurately and non-destructively detect the repair effect of the cable buffer layer ablation defect, provide important technical support for the cable buffer layer state evaluation, and have a wide application prospect in the field of power engineering. Description of the Drawings

[0029] The present invention will be further described below in conjunction with the drawings and embodiments.

[0030] Figure 1 It is a schematic diagram of the detection device for the repair effect of the buffer layer ablation of the high-voltage cable of the present invention.

[0031] Figure 2 This is the test equivalent circuit diagram of the detection device for the ablation repair effect of the buffer layer of the high-voltage cable of the present invention.

[0032] Figure 3 This is the test result diagram of the embodiment of the present invention.

[0033] Figure 1 In Figure 1, 1 is the cable core, 2 is the inner semiconductor layer, 3 is the cross-linked polyethylene main insulation layer, 4 is the insulation shielding layer, 5 is the buffer layer, 6 is the metal sheath, 100 is the equivalent circuit of the buffer layer, C is the reference capacitor, U DC , is the DC power supply, R is the current-limiting resistor, and V is the voltmeter. Specific Embodiments

[0034] Now, the present invention will be further described in 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.

[0035] As Figure 1-2 shown, a detection device for the ablation repair effect of the buffer layer of a high-voltage cable according to the present invention includes a power supply module, an electrode module, an acquisition module, and a control module. The power supply module and the acquisition module are connected in series with the buffer layer of the high-voltage cable through the electrode module. The acquisition module transmits the obtained information (voltage information) to the control module; the power supply module includes a DC power supply 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 acquisition module; the electrode module includes two measurement electrodes, electrode 1 and electrode 2. Electrode 1 is connected to the acquisition module and the insulation shielding 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; during the test, the electrode module only plays a connecting role, and the power supply module, the acquisition module, and the buffer layer of the high-voltage cable are connected in series. The acquisition module includes a reference capacitor and a voltmeter test module. The voltmeter test module includes a voltmeter, and the voltmeter is connected in parallel with the reference capacitor to measure the voltage on the reference capacitor during the test pressure application process. One end of the acquisition module is connected to the electrode module, and the other end of the acquisition module is connected to the power supply module.

[0036] The voltage range of the DC power supply is 0 - 5 kV.

[0037] 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.

[0038] The range of the reference capacitor is 1 μF - 10 μF.

[0039] 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 (test voltage, reference capacitance value), and the control module is used to calculate the acquired signal (voltage) and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

[0040] A detection method for the repair effect of the ablation of the high-voltage cable buffer layer according to the present invention uses the detection device for the repair effect of the ablation of the high-voltage cable buffer layer. The detection method includes the following steps:

[0041] Step 1: Cut off the power supply of the high-voltage cable;

[0042] 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;

[0043] Step 3: After setting the voltage amplitude and the reference capacitance value in the power supply module, the power supply module starts to measure. The acquisition module acquires data (voltage of the reference capacitance) and transmits it to the control module.

[0044] In Step 2, select the electrode fixing fixture and the electrode according to the actual test position: When the test position is the middle windowing position during cable repair, the cable at this position is cut to the insulation shield. Electrode 1 of the electrode module is fixed to the insulation 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 insulation shield layer and the metal sheath of the high-voltage cable through alligator clips.

[0045] In Step 3, the test time is 5 min - 10 min. Considering the construction site, a too long measurement time will become complicated and inefficient. Preferably, in Step 3, the test time is 5 min.

[0046] In Step 3, after the acquisition module acquires the reference capacitance voltage U(t), the following steps are used to evaluate the repair effect of the cable buffer layer ablation:

[0047] 1) Test the buffer layer ablated cables before and after repair, and respectively obtain the functions U1(t) and U2(t) of the reference capacitance voltage changing with time;

[0048] 2) Since the capacitance value C of the reference capacitance is determined and known, respectively calculate the functions Q1(t) and Q2(t) of the charge changing with time before and after repair according to formula (1);

[0049] Q(t) = CU(t) (1)

[0050] 3) Based on the function Q(t) of the charge varying with time, calculate the current functions I1(t) and I2(t) before and after repair according to formula (2);

[0051]

[0052] 4) Take the average value of the current results over a period of time, and calculate the average currents I 1-ave (t) and I 2-ave (t) before and after repair according to formula (3); The aforementioned period of time is taken as the 120 s before the test end time t e According to the test results, this period of time has been able to reach stability.

[0053]

[0054] 5) Calculate the current change rate ΔI through the average currents I 1-ave (t) and I 2-ave (t) before and after repair, and judge the repair effect of the buffer layer ablation;

[0055]

[0056] The repair effect levels include three levels: excellent, medium, and poor. Among them, the current change rate higher than 95% is excellent, the current change rate between 95% and 65% is medium, and the current change rate less than 65% is poor.

[0057] Embodiment

[0058] Taking a 220 kV retired high-voltage cable as an example in the laboratory, a section of it with a length of l = 2 m is taken for analysis. As Figure 1 shown, the high-voltage cable from the inside out is the cable core 1, the inner semiconductor layer 2, the cross-linked polyethylene main insulation layer 3, the insulation shielding layer 4, the buffer layer 5, and the metal sheath 6 in sequence.

[0059] Using the detection device of the present invention, electrode 1 is connected to the acquisition module and the insulation shielding layer 4, electrode 2 is connected to the power supply module and the metal sheath 6. The actual test position of the cable connected by electrode 1 and electrode 2 is the cable head end. According to the method of the present invention, the voltage amplitude in the power supply module is set to 100 V and the reference capacitance is 2 uF through the control module. The power supply module starts to measure. The acquisition module acquires the voltage of the reference capacitance and transmits it to the control module, and the control module evaluates the repair effect of the buffer layer ablation. The test results are shown in Figure 3 After calculation, the current change rate ΔI is 80%, then it can be determined the repair effect of the buffer layer ablation.

[0060] 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 ablation repair effect of a high-voltage cable buffer layer, 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 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 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 a reference capacitor and a voltmeter test module. The voltmeter test module includes a voltmeter, and the voltmeter is connected in parallel with the reference capacitor. One end of the collection module is connected to the electrode module, and the other end of the collection module is connected to the power supply module.

2. The high-voltage cable buffer layer ablation repair effect detection device according to claim 1, characterized in that, The voltage range of the DC power supply is 0 to 5 kV.

3. The detection device for the ablation repair effect of the high-voltage cable buffer layer according to claim 1, wherein, The electrode module includes a measuring electrode and an electrode fixing fixture. The measuring electrode contacts the measuring position of the high-voltage cable through the electrode fixing fixture. 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 ablation repair effect of the high-voltage cable buffer layer according to claim 1, wherein The range of the reference capacitor is 1 μF to 10 μF.

5. The detection device for the ablation repair effect of the high-voltage cable buffer layer 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 calculate the collected signals and evaluate the repair effect of the ablation defect of the high-voltage cable buffer layer.

6. A method for detecting the ablation repair effect of a high-voltage cable buffer layer, characterized in that, Using the detection device for the repair effect of the ablation of the high-voltage cable buffer layer according to any one of claims 1-7, the detection method 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 and the metal sheath of the high-voltage cable according to the actual test position; Step 3: After setting the voltage amplitude and the size of the reference capacitor in the power supply module, the power supply module starts to measure, and the collection module collects data and transmits it to the control module.

7. The method for detecting the ablation repair effect of the buffer layer of a high-voltage cable according to claim 6, wherein, In step 2, select the electrode fixing fixture and the electrode according to the actual test position: When the test position is the intermediate window position during cable maintenance, the cable at this position is cut to the insulation shield. Electrode 1 of the electrode module is fixed on the insulation shield of the high-voltage cable through a circular fixture or copper foil, and electrode 2 of the electrode module is fixed on 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 on the insulation shield and the metal sheath of the high-voltage cable through alligator clips.

8. The method for detecting the ablation repair effect of the buffer layer of a high-voltage cable according to claim 6, characterized in that, In step 3, the test time is 5 min - 10 min.

9. The method for detecting the ablation repair effect of the buffer layer of a high-voltage cable according to claim 8, wherein, In step 3, the test time is 5 min.

10. The method for detecting the ablation repair effect of the buffer layer of a high-voltage cable according to claim 6, wherein, In step 3, the collection module collects the reference capacitor voltage U(t). Through the following steps, evaluate the repair effect of the cable buffer layer ablation: 1) Test the ablated cable of the buffer layer before and after repair, and obtain the functions U1(t) and U2(t) of the reference capacitor voltage changing with time respectively; 2) Since the capacitance value C of the reference capacitor is determined and known, calculate the functions Q1(t) and Q2(t) of the charge changing with time before and after repair respectively according to formula (1); Q(t) = CU(t) (1) 3) Based on the function Q(t) of the charge varying with time, the current functions I1(t) and I2(t) before and after repair are calculated according to formula (2); 4) Take the average value of the current results over a period of time, and calculate the average currents I 1-ave (t) and I 2-ave (t) before and after repair according to formula (3); the period of time mentioned above is taken as the 120 s before the end time t of the test. 1-ave (t) and I 2-ave (t); the period of time mentioned above is taken as the 120 s before the end time t of the test. e The first 120 s; 5) By the average current I before and after repair 1-ave (t) and I 2-ave (t), calculate the current change rate ΔI, and judge the repair effect of the buffer layer ablation according to the current change rate ΔI;

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