Device and method for detecting volume resistivity of flat sheath buffer layer

Abstract

The present application relates to flat sheath buffer volume resistivity detection device and method, through setting short circuit threshold, passage threshold, passage current threshold and charging current time, the distance between the upper and lower electrodes of the test standard buffer sample and the measured buffer sample and the reading of the ammeter are compared and tested, and the volume resistivity of the measured buffer is calculated according to the reading. The method designed by the present application can detect the volume resistivity of the buffer of the flat sheath high-voltage power cable. Unlike existing detection methods and devices, this method can simulate the covering, moisture and pressure of the buffer tape in the cable, and the detection result is closer to the working condition. It is mainly used for quality supervision and inspection of the buffer of new production into the network cable, and can provide important reference for operation and maintenance of in-service high-voltage power cable.

Description

Technical Field

[0001] This invention belongs to the field of high voltage and insulation technology, and in particular to a device and method for detecting the volume resistivity of a flat sheath buffer layer. Background Technology

[0002] In recent years, high-voltage power cables have experienced frequent failures nationwide due to buffer layer erosion leading to cable breakdown. Increased volume resistivity of the buffer layer after moisture absorption is considered a necessary condition for these failures. Therefore, there is an urgent need for a method to detect the volume resistivity of the buffer layer in high-voltage power cables. To prevent the continued occurrence of such failures, cable suppliers have developed high-voltage power cables with flat metal sheaths. Compared to existing corrugated metal sheath cables, flat metal sheathed high-voltage cables have a tighter fit between the buffer layer and the metal sheath, resulting in better electrical connection performance. However, moisture absorption during the production process can still cause flat metal sheathed cables to have excessive buffer layer volume resistivity. Therefore, developing a method for detecting the volume resistivity of the buffer layer in flat metal sheathed high-voltage power cables is essential to prevent defective cables from being put into operation. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and propose a device and method for detecting the volume resistivity of the flat sheath buffer layer. This device and method can simulate the overlapping, moisture, and pressure conditions of the inner buffer layer wrapping tape of the cable. The test results are closer to the working conditions. It is mainly used for quality supervision and inspection of the buffer layer of newly produced cables entering the network, and can also provide important reference for the operation and maintenance of high-voltage power cables in operation.

[0004] The technical problem solved by this invention is achieved through the following technical solution:

[0005] A flat sheath buffer layer volume resistivity detection device includes a detector and electrode packaging. The detector includes a user input terminal, a display screen, a processing and computing unit, a memory, a base, a bracket, an upper electrode, a lower electrode, a transmission mechanism, a position sensor, a DC voltage source, and a switch. The bracket is installed above the base. The transmission mechanism is installed at the protruding end of the bracket and moves vertically up and down along the protruding end of the bracket. The upper electrode is installed below the transmission mechanism. The lower electrode is installed above the bracket corresponding to the installation position of the upper electrode. The position sensor is installed next to the lower electrode. The input terminal is located on the upper surface of the bracket, and the display screen and switch are located on the lower surface of the bracket. The processing and computing unit, memory, DC voltage source, voltmeter, ammeter, and protective resistor are located inside the bracket.

[0006] Furthermore, the electrode packaging has a sealing opening at the top and a vacuum extraction port at the bottom, and a buffer layer is installed inside the electrode packaging.

[0007] Furthermore, the memory is connected to the processing and computing unit for storing data, and the processing and computing unit is connected to the ammeter and voltmeter respectively.

[0008] Furthermore, the upper electrode is connected in series with a protective resistor and a switch to the positive terminal of a DC voltage source. The negative terminal of the DC voltage source is connected in series with a galvanometer and the lower electrode. The upper electrode and the lower electrode are connected through an electrode package. A voltmeter is connected in parallel across the two ends of the upper electrode and the lower electrode.

[0009] Moreover, the base is an insulated base.

[0010] A method for detecting the volume resistivity of a flat sheath buffer layer includes the following steps:

[0011] Step 1: Obtain the cable parameters based on the cable factory test report or actual measurement results;

[0012] Step 2: Disassemble the cable outer sheath and flat metal sheath, quickly cut the wrapped and covered buffer layer, put it into the electrode packaging and seal it to make a standard buffer layer sample and a test buffer layer sample.

[0013] Step 3: Turn on the switch, input the cable parameters, short circuit threshold, continuity threshold, continuity current threshold, and charging current and time into the user input terminal, and store the parameters into the memory.

[0014] Step 4: Place the standard buffer layer sample between the upper and lower electrodes, apply a low DC voltage through a DC voltage source, and control the upper electrode to slowly descend through a transmission mechanism.

[0015] Step 5: When the ammeter reading exceeds the short-circuit threshold, read the ammeter measurement value I1. Ensure that the upper and lower electrodes and the standard buffer layer sample are in full contact and read the distance d1 between the upper and lower electrodes of the position sensor.

[0016] Step 6: Stop applying low-voltage DC voltage, and control the upper electrode to slowly rise to the initial position through the transmission mechanism;

[0017] Step 7: Place the test buffer layer sample between the upper and lower electrodes and apply a low DC voltage through a DC voltage source. Control the upper electrode to slowly descend through the transmission mechanism and obtain the ammeter measurement value I2. When the relative error between the ammeter measurement value I1 and the ammeter measurement value I2 is less than the path threshold, the upper and lower electrodes and the test buffer layer sample are in full contact. Read the distance d2 between the upper and lower electrodes of the position sensor.

[0018] Step 8: Control the upper electrode of the transmission mechanism to descend slowly at a slower speed, and the sensor continuously reads the distance d between the two electrodes. c When satisfied At this time, the transmission mechanism keeps the upper electrode stationary. At this time, the elastic deformation amplitude of the buffer layer is the same as the deformation amplitude inside the cable, and the upper electrode remains stationary.

[0019] Step 9: Gradually increase the DC voltage between the upper and lower electrodes until the current I detected by the ammeter reaches the path current threshold, satisfying I > I0. valid The DC voltage is kept constant for a time t seconds to eliminate the influence of the charging current.

[0020] Step 10: Read the readings of voltmeter U and ammeter I, and calculate the volume resistivity of the buffer layer under test based on the electrode area S. Where d Al The nominal value of the inner radius of the flat metal sheath, d OB The nominal value of the outer radius of the cable including the insulated and shielded cable, t hc It is the nominal value of the product of the thickness of a single buffer layer and the number of wrapping layers;

[0021] Step 11: Display the calculated volume resistivity of the buffer layer on the screen and give a conclusion on whether the volume resistivity of the buffer layer is qualified according to the corresponding standard.

[0022] Furthermore, the cable parameters in step 1 include: the inner radius d of the flat metal sheath. Al Nominal value, including the outer radius d of the insulated and shielded cable. OB Nominal value, the product of the thickness of a single buffer layer and the number of wrapping layers, t hc Nominal value.

[0023] Moreover, the specific implementation method of step 2 is as follows: disassemble the cable outer sheath and flat metal sheath, keep the buffer layer in the initial state of the cable wrapping and covering, and the surface can cover the conductor electrodes on both sides of the electrode packaging. After sealing the electrode packaging, extract the air from the packaging and seal it for preservation as a sample of the encapsulated buffer layer.

[0024] The advantages and positive effects of this invention are:

[0025] This invention calculates the volume resistivity of the buffer layer by setting short-circuit threshold, continuity threshold, continuity current threshold, and charging current-time, comparing the distance between the upper and lower electrodes of the standard buffer layer sample and the test buffer layer sample with the ammeter reading, and then calculating the volume resistivity of the test buffer layer based on the readings. Using the method designed in this invention, the volume resistivity of the buffer layer in flat-sheathed high-voltage power cables can be detected. Unlike existing detection methods and devices, this method can simulate the overlapping, moisture absorption, and pressure conditions of the buffer layer wrapping tape inside the cable, resulting in test results that more closely resemble actual operating conditions. It is mainly used for quality supervision and inspection of the buffer layer in newly manufactured cables entering the network and can also provide important reference for the operation and maintenance of high-voltage power cables in operation. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the device of the present invention;

[0027] Figure 2 This is an internal circuit diagram of the device of the present invention;

[0028] Figure 3 This is a schematic diagram of the electrode packaging of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings.

[0030] The flat sheath buffer layer volume resistivity testing device can simulate the overlapping, moisture absorption, and pressure conditions of the inner buffer layer wrapping tape of the cable, providing test results that more closely resemble actual operating conditions. The device includes a detector and electrode packaging, such as... Figure 1 The detector includes a user input terminal, a display screen, a processing and computing unit, a memory, a base, a bracket, an upper electrode, a lower electrode, a transmission mechanism, a position sensor, a DC voltage source, and a switch. The base is an insulated base for protective grounding. The bracket is installed above the base. The transmission mechanism is installed at the outlet end of the bracket and moves up and down vertically along the outlet end of the bracket. The upper electrode is installed below the transmission mechanism. The lower electrode is installed above the bracket corresponding to the installation position of the upper electrode. The position sensor is installed next to the lower electrode. The input terminal is located on the upper surface of the bracket, and the display screen and switch are located on the lower surface of the bracket. The processing and computing unit, memory, DC voltage source, voltmeter, ammeter, and protective resistor are located inside the bracket.

[0031] The memory-connected processing unit is used to store data, and the processing unit is connected to the ammeter and voltmeter respectively.

[0032] like Figure 2 As shown, the upper electrode is connected in series with a protective resistor and a switch to the positive terminal of a DC voltage source. The negative terminal of the DC voltage source is connected in series with a galvanometer and the lower electrode. The upper and lower electrodes are connected through an electrode package. A voltmeter is connected in parallel across the two ends of the upper and lower electrodes.

[0033] like Figure 3 As shown, the electrode packaging has a sealing opening at the top and a vacuum extraction port at the bottom, and a buffer layer is installed inside the electrode packaging.

[0034] A detection method for a flat sheath buffer layer volume resistivity detection device, ignoring the deviation of the insulated core from the center of the flat metal sheath under gravity, includes the following steps:

[0035] Step 1: Obtain the cable parameters based on the cable factory test report or actual measurement results.

[0036] The cable parameters for this step include: inner radius d of the flat metal sheath. AlNominal value, including the outer radius d of the insulated and shielded cable. OB Nominal value, the product of the thickness of a single buffer layer and the number of wrapping layers, t hc Nominal value.

[0037] Step 2: Disassemble the cable outer sheath and flat metal sheath, quickly cut the wrapped and overlapping buffer layer, put it into the electrode packaging and seal it to make a standard buffer layer sample and a test buffer layer sample.

[0038] The specific implementation method of this step is as follows: disassemble the cable outer sheath and flat metal sheath, keep the buffer layer in the initial state of the cable wrapping and covering, and the surface can cover the conductor electrodes on both sides of the electrode packaging. After sealing the electrode packaging, extract the air from the packaging and seal it for preservation as a sample of the encapsulated buffer layer.

[0039] Step 3: Turn on the switch, input the cable parameters, short-circuit threshold, path threshold, path current threshold, and charging current and time into the user input terminal, and store the parameters in the memory.

[0040] Step 4: Place the standard buffer layer sample between the upper and lower electrodes, apply a low DC voltage through a DC voltage source, and control the upper electrode to slowly descend through a transmission mechanism.

[0041] Step 5: When the ammeter reading exceeds the short-circuit threshold, read the ammeter measurement value I1. Ensure that the upper and lower electrodes and the standard buffer layer sample are in full contact, and read the distance d1 between the upper and lower electrodes of the position sensor.

[0042] Step 6: Stop applying low-voltage DC voltage and control the upper electrode to slowly rise to the initial position through the transmission mechanism.

[0043] Step 7: Place the test buffer layer sample between the upper and lower electrodes and apply a low DC voltage through a DC voltage source. Control the upper electrode to slowly descend through the transmission mechanism and obtain the ammeter measurement value I2. When the relative error between the ammeter measurement value I1 and the ammeter measurement value I2 is less than the path threshold, the upper and lower electrodes and the test buffer layer sample are in full contact. Read the distance d2 between the upper and lower electrodes of the position sensor.

[0044] Step 8: Control the upper electrode of the transmission mechanism to descend slowly at a slower speed, and the sensor continuously reads the distance d between the two electrodes. c When satisfied At this time, the transmission mechanism keeps the upper electrode stationary. At this time, the elastic deformation amplitude of the buffer layer is the same as the deformation amplitude inside the cable, and the upper electrode remains stationary.

[0045] Step 9: Gradually increase the DC voltage between the upper and lower electrodes until the current I detected by the ammeter reaches the path current threshold, satisfying I > I0.valid The DC voltage is kept constant for a time t seconds to eliminate the influence of the charging current.

[0046] Step 10: Read the readings of voltmeter U and ammeter I, and calculate the volume resistivity of the buffer layer under test based on the electrode area S.

[0047] Step 11: Display the calculated volume resistivity of the buffer layer on the screen and give a conclusion on whether the volume resistivity of the buffer layer is qualified according to the corresponding standard.

[0048] The effectiveness of the present invention is verified by detecting the volume resistivity of the buffer layer of a 220kV high-voltage power cable, according to the above-mentioned device and method for detecting the volume resistivity of the buffer layer.

[0049] The testing process includes the following steps:

[0050] Step 1: Based on the cable factory test report or actual measurement results, compile the following data: inner radius d of the flat metal sheath. Al Nominal value, including the outer radius d of the insulated and shielded cable. OB Nominal value, the product of the thickness of a single buffer layer and the number of wrapping layers, t hc The nominal values ​​are shown in Table 1.

[0051] Table 1

[0052]

[0053] Step 2 involves disassembling the cable's outer sheath and flat metal sheath, quickly cutting the wrapped buffer layer to the appropriate size, and placing it inside... Figure 3 The electrode packaging shown. The buffer layer needs to maintain the initial state of the cable wrapping and overlap, and its surface should be able to cover the conductor electrodes on both sides of the electrode packaging. After sealing the electrode packaging, the air inside the packaging is extracted and sealed for storage, serving as a sample of the encapsulated buffer layer. Due to the vacuum state, the encapsulated buffer layer can maintain the wrapping and overlap state, preventing it from loosening and falling off; on the other hand, it can prevent the buffer layer from getting damp during storage.

[0054] Step 3: Turn on the switch. The detection device interacts with the user through the user input terminal and display screen. The user inputs the corresponding parameters. (e.g., inner radius d of the flat metal sheath) Al Nominal value, including the outer radius d of the insulated and shielded cable. OB Nominal value, the product of the thickness of a single buffer layer and the number of wrapping layers, t hc Nominal value, short-circuit threshold ε sc Path threshold ε loop Path current threshold I validThe parameters, including charging current and time t, are shown in Table 2. After user confirmation, the data will be saved to memory.

[0055] Table 2

[0056] parameter <![CDATA[ε sc (A)]]> <![CDATA[ε loop (%)]]> <![CDATA[I valid (A)]]> t(s) numerical values 1 5 0.005 60

[0057] Step 4: The user places the evacuated electrode package (without a buffer layer) between the upper and lower electrodes of the volume resistivity detector and selects the "zero" function. The display shows the message: "Electrode voltage applied, do not touch, safety precautions." A low-voltage DC voltage is then applied between the upper and lower electrodes. The detector slowly lowers the upper electrode via a transmission mechanism.

[0058] Step 5: When the ammeter reading exceeds the short-circuit threshold ε sc At that time, it is assumed that the upper and lower electrodes have made full contact with the electrode packaging, and the position sensor reads the distance d1 between the two electrodes.

[0059] Step 6: Stop applying voltage between the upper and lower electrodes. The transmission mechanism controls the upper electrode of the volume resistivity detection device to slowly rise to the starting position. The display screen will show: "Electrode packaging thickness measurement completed".

[0060] Step 7: The user places the encapsulated buffer layer sample to be tested between the two electrodes and selects the "Measure" function of the volume resistivity detection device. The display shows the message: "Electrodes are under voltage, do not touch, be careful." A low DC voltage is applied between the upper and lower electrodes, and the transmission mechanism controls the upper electrode to slowly descend. When the relative error of the two current measurements I1 and I2 taken at a near-term time is less than the path threshold, i.e. At this point, it can be assumed that the electrode and the encapsulated buffer layer sample are in good contact, and the position sensor reads the distance d2 between the two electrodes.

[0061] Step 8: The transmission mechanism controls the upper electrode to descend slowly at a slower speed, and the sensor continuously reads the distance d between the two electrodes. c When satisfied Right now At this time, the transmission mechanism keeps the upper electrode stationary. At this time, the elastic deformation amplitude of the buffer layer is the same as the deformation amplitude inside the cable, and the upper electrode remains stationary.

[0062] Step 9: Gradually increase the DC voltage between the upper and lower electrodes until the current I detected by the ammeter reaches the path current threshold, i.e., I > I0. valid The DC voltage is kept constant for a time t seconds to eliminate the influence of the charging current.

[0063] Step 10: Read the voltmeter U, the ammeter I, and calculate the volume resistivity of the buffer layer based on information such as the electrode area S.

[0064] Step 11: Display the calculated volume resistivity results on the screen, as shown in Table 3, and provide a conclusion on whether the volume resistivity is qualified according to the relevant standards. The volume resistivity test of the buffer layer is now complete.

[0065] Table 3

[0066] result U(V) I(A) <![CDATA[S(m 2 )]]> <![CDATA[d2(m)]]> <![CDATA[d1(m)]]> σ(Ω·m) numerical values 4.5 0.0118 0.001963 0.00599 0.00031 130.60

[0067] The current requirement for volume resistivity in JB / T 10259-2014 "Water-blocking tape for cables and optical fibers" is no more than 1000 Ω·m, so the volume resistivity of the buffer layer of this cable is qualified.

[0068] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A detection method for the volume resistivity detection device of a flat sheath buffer layer, characterized in that: The device used includes a detector and electrode packaging, wherein the detector includes a user input terminal, a display screen, a processing unit, a memory, a base, a bracket, an upper electrode, a lower electrode, a transmission mechanism, a position sensor, a DC voltage source, and a switch; The detection method includes the following steps: Step 1: Obtain the cable parameters based on the cable factory test report or actual measurement results; Step 2: Disassemble the cable outer sheath and flat metal sheath, quickly cut the wrapped and covered buffer layer, put it into the electrode packaging and seal it to make a standard buffer layer sample and a test buffer layer sample. Step 3: Turn on the switch, input the cable parameters, short circuit threshold, continuity threshold, continuity current threshold, and charging current and time into the user input terminal, and store the parameters into the memory. Step 4: Place the standard buffer layer sample between the upper and lower electrodes, apply a low DC voltage through a DC voltage source, and control the upper electrode to slowly descend through a transmission mechanism. Step 5: When the ammeter reading exceeds the short-circuit threshold, read the ammeter measurement value I1. Ensure that the upper and lower electrodes and the standard buffer layer sample are in full contact and read the distance d1 between the upper and lower electrodes of the position sensor. Step 6: Stop applying low-voltage DC voltage, and control the upper electrode to slowly rise to the initial position through the transmission mechanism; Step 7: Place the test buffer layer sample between the upper and lower electrodes and apply a low DC voltage through a DC voltage source. Control the upper electrode to slowly descend through the transmission mechanism and obtain the ammeter measurement value I2. When the relative error between the ammeter measurement value I1 and the ammeter measurement value I2 is less than the path threshold, the upper and lower electrodes and the test buffer layer sample are in full contact. Read the distance d2 between the upper and lower electrodes of the position sensor. Step 8: Control the upper electrode of the transmission mechanism to descend slowly at a slower speed, and the sensor continuously reads the distance d between the two electrodes. c When satisfied and At this time, the transmission mechanism keeps the upper electrode stationary. At this time, the elastic deformation amplitude of the buffer layer is the same as the deformation amplitude inside the cable, and the upper electrode remains stationary. Step 9: Gradually increase the DC voltage between the upper and lower electrodes until the current I detected by the ammeter reaches the path current threshold, satisfying I > I0. valid The DC voltage is kept constant for a time t seconds to eliminate the influence of the charging current. Step 10: Read the readings of voltmeter U and ammeter I, and calculate the volume resistivity of the buffer layer under test based on the electrode area S. Where d Al The nominal value of the inner radius of the flat metal sheath, d OB The nominal value of the outer radius of the cable including the insulated and shielded cable, t hc It is the nominal value of the product of the thickness of a single buffer layer and the number of wrapping layers; Step 11: Display the calculated volume resistivity of the buffer layer on the screen, and give a conclusion on whether the volume resistivity of the buffer layer is qualified according to the corresponding standard.

2. The detection method of the flat sheath buffer layer volume resistivity detection device according to claim 1, characterized in that: The bracket is installed above the base. A transmission mechanism is installed at the protruding end of the bracket. The transmission mechanism moves up and down vertically along the protruding end of the bracket. An upper electrode is installed below the transmission mechanism. A lower electrode is installed above the bracket corresponding to the installation position of the upper electrode. A position sensor is installed next to the lower electrode. An input terminal is provided above the surface of the bracket. A display screen and a switch are provided below the surface of the bracket. The bracket contains a processing and computing unit, a memory, a DC voltage source, a voltmeter, an ammeter, and a protective resistor. The electrode packaging has a sealing opening at the top and a vacuum extraction port at the bottom, and a buffer layer is installed inside the electrode packaging. The memory is connected to the processing and computing unit for storing data, and the processing and computing unit is connected to the ammeter and voltmeter respectively. The upper electrode is connected in series with a protective resistor and a switch to the positive terminal of a DC voltage source. The negative terminal of the DC voltage source is connected in series with a galvanometer and the lower electrode. The upper electrode and the lower electrode are connected through an electrode package. A voltmeter is connected in parallel across the two ends of the upper electrode and the lower electrode. The base is an insulated base; The cable parameters in step 1 include: the inner radius d of the flat metal sheath. Al Nominal value, including the outer radius d of the insulated and shielded cable. OB Nominal value, the product of the thickness of a single buffer layer and the number of wrapping layers, t hc Nominal value.

3. The detection method of the flat sheath buffer layer volume resistivity detection device according to claim 1, characterized in that: The specific implementation method of step 2 is as follows: disassemble the cable outer sheath and flat metal sheath, keep the buffer layer in the initial state of the cable wrapping and covering, and the surface can cover the conductor electrodes on both sides of the electrode packaging. After sealing the electrode packaging, extract the air from the packaging and seal it for preservation as a sample of the encapsulated buffer layer.

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