CN116400137A - Device and method for detecting volume resistivity of flat sheath buffer layer - Google Patents

Abstract

The invention relates to a device and a method for detecting volume resistivity of a buffer layer of a flat sheath. By adopting the method designed by the invention, the volume resistivity of the buffer layer of the high-voltage power cable with the flat sheath can be detected. Different from the existing detection method and device, the method can simulate the conditions of covering, wetting and pressing of the buffer layer around the tape in the cable, the detection result is closer to the working condition, and the method is mainly used for quality supervision and inspection of the buffer layer of the newly produced network cable and can provide important reference for operation, maintenance and overhaul of the high-voltage power cable.

Description

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

technical field

The invention belongs to the technical field of high voltage and insulation, in particular to a volume resistivity detection device and method for a buffer layer of a flat sheath.

Background technique

In recent years, faults of high-voltage power cables due to buffer layer ablation caused by breakdown of the cable body have occurred frequently throughout the country. An increase in the volume resistivity of the damped buffer layer has been identified as a necessary condition for initiating failure. Therefore, there is an urgent need for a method that can detect the volume resistivity of the buffer layer of a high-voltage power cable. To prevent such failures from continuing to occur, cable suppliers have developed high voltage power cables with flat metal sheaths. Compared with the existing corrugated metal sheathed cables, in the flat metal sheathed high-voltage cables, the buffer layer and the metal sheath part fit more closely, and the electrical connection performance is better. However, the problem of moisture in the production process may still cause the defect that the volume resistivity of the buffer layer exceeds the standard in flat metal sheathed cables. Therefore, it is necessary to develop a volume resistivity detection method for the buffer layer of flat metal sheathed high-voltage power cables, which will prevent defective cables from entering the network.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and propose a volume resistivity detection device and method for the buffer layer of a flat sheath, which can simulate the covering, damp, and pressure conditions of the buffer layer wrapping tape in the cable, and the detection results are closer to the working conditions. It is mainly used for the quality supervision and inspection of the buffer layer of newly produced network cables, and can provide an important reference for the operation and maintenance of high-voltage power cables in operation.

The present invention solves its technical problem and realizes by taking the following technical solutions:

The volume resistivity detection device of the flat sheath buffer layer includes a detector and an electrode package, wherein the detector includes a user input terminal, a display screen, a processing calculation unit, a memory, a base, a bracket, an upper electrode, a lower electrode, a transmission mechanism, and a position sensor , DC voltage source and switch; wherein the bracket is installed above the base, and the transmission mechanism is installed at the output end of the bracket. The lower electrode is installed above the corresponding bracket, and the position sensor is installed next to the lower electrode. An input terminal is arranged above the surface of the bracket, a display screen and a switch are installed under the surface of the bracket, and a processing calculation unit, a memory, a DC voltage source, and a voltage source are arranged inside the bracket. meter, ammeter and protective resistor.

Moreover, a sealing port is provided on the top of the electrode package, a vacuum port is provided on the bottom, and a buffer layer is placed inside the electrode package.

Moreover, the memory is connected to the processing and computing unit for storing data, and the processing and computing unit is respectively connected to the ammeter and the voltmeter.

Moreover, the upper electrode is connected in series with the protective resistor and the switch to connect the positive pole of the DC voltage source, the negative pole of the DC voltage source is connected in series with the ammeter and the lower electrode, and the upper electrode and the lower electrode are connected through an electrode package. terminal parallel voltmeter.

Moreover, the base is an insulating base.

A detection method of a flat sheath buffer layer volume resistivity detection device, comprising the following steps:

Step 1. Obtain the cable parameters according to the cable factory test report or actual measurement results;

Step 2. Disassemble the cable outer sheath and the flat metal sheath, quickly cut the wrapped and covered buffer layer, put it into the electrode package for sealing, and make a standard buffer layer sample and a tested buffer layer sample ;

Step 3, turn on the switch, input the cable parameters and the short circuit threshold, the access threshold, the access current threshold and the charging current time at the user input terminal, and store the parameters in the memory;

Step 4. Place the standard buffer layer sample between the upper electrode and the lower electrode, apply a low-voltage DC voltage through a DC voltage source, and control the upper electrode to slowly drop through the transmission mechanism;

Step 5. When the reading of the ammeter exceeds the short-circuit threshold, read the measured value I ₁ of the ammeter, the upper electrode and the lower electrode are fully in contact with the standard buffer layer sample, and read the distance d ₁ between the upper electrode and the lower electrode of the position sensor;

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

Step 7. Place the sample of the buffer layer to be tested between the upper electrode and the lower electrode, apply a low-voltage DC voltage through a DC voltage source, and control the upper electrode to drop slowly through the transmission mechanism, and obtain the measured value I ₂ of the galvanometer. When the galvanometer When the relative error between the measured value _I1 and the ammeter measured value _I2 is less than the access threshold, the upper electrode and the lower electrode are in full contact with the buffer layer sample to be tested, and the distance _d2 between the upper electrode and the lower electrode of the position sensor is read;

时，传动机构使上电极保持静止，此时缓冲层弹性形变幅度与在电缆内部时形变幅度一致，上电极保持静止；Step 8. Control the upper electrode of the transmission mechanism to drop slowly at a slower speed, and the sensor continuously reads the distance d _c between the two electrodes.

, the transmission mechanism keeps the upper electrode still, at this time, the elastic deformation range of the buffer layer is consistent with the deformation range when it is inside the cable, and the upper electrode remains static;

Step 9. Gradually increase the DC voltage between the upper electrode and the lower electrode until the current I detected by the ammeter reaches the channel current threshold. When I>I _valid , keep the DC voltage constant for t seconds, and exclude the charging current Influence;

其中d_Al为平金属护套内侧半径标称值，d_OB为含绝缘屏蔽电缆外侧半径标称值，t_hc为缓冲层单层厚度与绕包层数的乘积标称值；Step 10, read the voltmeter U, the ammeter indication I, and calculate the volume resistivity of the measured buffer layer according to the electrode area S

Where d _Al is the nominal value of the inner radius of the flat metal sheath, d _OB is the nominal value of the outer radius of the cable with insulation and shielding, and t _hc is the nominal value of the product of the single-layer thickness of the buffer layer and the number of wrapping layers;

In step 11, display the calculation result of the volume resistivity of the buffer layer under test on the display screen, and give a conclusion whether the volume resistivity of the buffer layer under test is qualified according to the corresponding standards.

Moreover, the cable parameters in step 1 include: the nominal value of the inner radius d _Al of the flat metal sheath, the nominal value of the outer radius d _OB of the insulating shielded cable, and the product t _hc of the single-layer thickness of the buffer layer and the number of wrapping layers value.

Moreover, the specific implementation method of step 2 is: disassemble the cable outer sheath and the flat metal sheath, the buffer layer maintains the initial state of the wrapping and covering in the cable, and the surface can cover the conductor electrodes on both sides of the electrode package , after sealing the electrode package, extract the air in the package for sealed storage, and use it as a sample of the buffer layer after packaging.

Advantage and positive effect of the present invention are:

The present invention compares and tests the distance between the standard buffer layer sample and the buffer layer test upper and lower electrodes and the readings of the ammeter by setting the short-circuit threshold, the access threshold, the access current threshold and the charging current time, and calculates the measured value according to the readings. Buffer layer volume resistivity. By adopting the method designed by the invention, the volume resistivity of the buffer layer of the flat-sheath high-voltage power cable can be detected. Different from the existing detection methods and devices, this method can simulate the cover, moisture and pressure of the inner buffer layer of the cable, and the detection results are closer to the working conditions. It is mainly used for the quality supervision and inspection of the buffer layer of newly produced cables , and can provide an important reference for the operation and maintenance of high-voltage power cables in transit.

Description of drawings

Fig. 1 is the structural diagram of device of the present invention;

Fig. 2 is the internal circuit diagram of device of the present invention;

Fig. 3 is a schematic diagram of an electrode package of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The volume resistivity detection device of the buffer layer of the flat sheath can simulate the covering, moisture and pressure of the inner buffer layer of the cable, and the detection results are closer to the working conditions. The device includes a detector and an electrode package. As shown in Figure 1, the detector includes a user input terminal, a display screen, a processing calculation unit, a memory, a base, a bracket, an upper electrode, a lower electrode, a transmission mechanism, a position sensor, a DC voltage source and switch; the base is an insulating base to achieve protective grounding, the bracket is installed above the base, and the transmission mechanism is installed at the output end of the bracket. The transmission mechanism moves up and down along the vertical direction of the output end of the bracket. The lower electrode is installed above the bracket corresponding to the electrode installation position, and the position sensor is installed next to the lower electrode. An input terminal is arranged above the surface of the bracket, a display screen and a switch are installed below the surface of the bracket, and a processing calculation unit, a memory, and a DC voltage are installed inside the bracket. source, voltmeter, ammeter, and protection resistors.

The memory is connected to the processing and computing unit for storing data, and the processing and computing unit is respectively connected to the ammeter and the voltmeter.

As shown in Figure 2, the upper electrode is connected in series with the protective resistor, the switch is connected to the positive pole of the DC voltage source, the negative pole of the DC voltage source is connected in series with the ammeter and the lower electrode, the upper electrode and the lower electrode are connected through the electrode package, and the upper electrode and the lower electrode A voltmeter is connected in parallel across both terminals.

As shown in Figure 3, there is a sealing port on the top of the electrode package, a vacuum port on the bottom, and a buffer layer inside the electrode package.

A detection method for a volume resistivity detection device of a buffer layer of a flat sheath, ignoring the deviation of the insulated wire core from the center of the circle of the flat metal sheath under the action of gravity, comprising the following steps:

Step 1. Obtain the cable parameters according to the cable factory test report or actual measurement results.

The cable parameters in this step include: the nominal value of the inner radius d _Al of the flat metal sheath, the nominal value of the outer radius d _OB of the cable with insulation shielding, and the nominal value t _hc of the product of the single-layer thickness of the buffer layer and the number of wrapping layers.

Step 2. Disassemble the cable outer sheath and the flat metal sheath, quickly cut the wrapped and covered buffer layer, put it into the electrode package for sealing, and make a standard buffer layer sample and a tested buffer layer sample .

The specific implementation method of this step is: disassemble the cable outer sheath and the flat metal sheath, the buffer layer maintains the initial state of the wrapping and covering in the cable, and the surface can cover the conductor electrodes on both sides of the electrode package, and the electrode package After sealing, the air in the packaging is taken out and stored in a sealed environment as a buffer layer sample after packaging.

Step 3. Turn on the switch, input cable parameters, short circuit threshold, pass threshold, pass current threshold and charging current time at the user input terminal, and store the parameters in the memory.

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

Step 5. When the reading of the ammeter exceeds the short circuit threshold, read the measured value I ₁ of the ammeter, the upper electrode and the lower electrode are in full contact with the standard buffer layer sample, and read the distance d ₁ between the upper electrode and the lower electrode of the position sensor.

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

Step 7. Place the sample of the buffer layer to be tested between the upper electrode and the lower electrode, apply a low-voltage DC voltage through a DC voltage source, and control the upper electrode to drop slowly through the transmission mechanism, and obtain the measured value I ₂ of the galvanometer. When the galvanometer When the relative error between the measured value I ₁ and the ammeter measured value I ₂ is less than the access threshold, the upper electrode and the lower electrode are in full contact with the buffer layer sample to be tested, and the distance d ₂ between the upper electrode and the lower electrode of the position sensor is read.

时，传动机构使上电极保持静止，此时缓冲层弹性形变幅度与在电缆内部时形变幅度一致，上电极保持静止。Step 8. Control the upper electrode of the transmission mechanism to drop slowly at a slower speed, and the sensor continuously reads the distance d _c between the two electrodes.

, the transmission mechanism keeps the upper electrode still. At this time, the elastic deformation range of the buffer layer is consistent with the deformation range when it is inside the cable, and the upper electrode remains static.

Step 9. Gradually increase the DC voltage between the upper electrode and the lower electrode until the current I detected by the ammeter reaches the channel current threshold. When I>I _valid , keep the DC voltage constant for t seconds, and exclude the charging current Influence.

Step 10, read the voltmeter U, the ammeter indication I, and calculate the volume resistivity of the measured buffer layer according to the electrode area S

In step 11, display the calculation result of the volume resistivity of the buffer layer under test on the display screen, and give a conclusion whether the volume resistivity of the buffer layer under test is qualified according to the corresponding standards.

According to the above-mentioned device and method for detecting the volume resistivity of the buffer layer of a flat sheath, the effect of the present invention is verified by detecting the volume resistivity of the buffer layer of a 220kV high-voltage power cable.

The detection step includes the following steps:

Step 1. According to the cable factory test report or actual measurement results, the following data are sorted out: the nominal value of the inner radius d _Al of the flat metal sheath, the nominal value d _OB of the outer radius of the cable with insulation shielding, the single-layer thickness of the buffer layer and the wrapping The product t _hc nominal value of the number of layers, the data are shown in Table 1.

Table 1

Step 2: Disassemble the cable outer sheath and flat metal sheath, quickly cut the buffer layer wrapped and covered to a suitable size, and put it into the electrode package as shown in Figure 3. The buffer layer needs to maintain the original state of the wrapping in the cable, and the surface can cover the conductor electrodes on both sides of the electrode wrapping. After the electrode package is sealed, the air in the package is taken out for sealed storage, which is used as a sample of the buffer layer after packaging. Due to the vacuum state of the packaged buffer layer, on the one hand, it can maintain the state of wrapping and covering, and will not loosen and fall off; on the other hand, it can prevent the buffer layer from getting damp during storage.

In the third step, the switch is turned on, and the detection device interacts with the user through the user input terminal and the display screen. The corresponding parameters are input by the user. The nominal value of the inner radius d _Al of the flat metal sheath, the nominal value of the outer radius d _OB of the insulating shielded cable, the nominal value of the product of the single layer thickness of the buffer layer and the number of wrapping layers t _hc , the short circuit threshold ε _sc , the passage threshold ε _loop , the channel current threshold I _valid and the charging current time t and other parameters, the parameters are shown in Table 2. After the user confirms, save it to the memory.

Table 2

parameter ε _sc (A) ε _loop (%) I _valid (A) t(s) value 1 5 0.005 60

Step 4: The user puts an electrode package that has drawn out air but does not contain a buffer layer between the upper and lower electrodes of the volume resistivity detection device, and selects the "return to zero" function of the volume resistivity detection device. The display screen gave a prompt: "The voltage has been applied to the electrodes, please do not touch, pay attention to safety", and a low-voltage direct current voltage was applied between the upper and lower electrodes of the device. The detection device controls the upper electrode to descend slowly through the transmission mechanism.

Step 5, when the reading of the ammeter exceeds the short-circuit threshold ε _sc , it is considered that the upper and lower electrodes are in full contact with the electrode package, and the position sensor reads the distance d ₁ between the two electrodes.

Step 6: Stop applying the 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 initial position, and the display screen gives a prompt: "The measurement of the thickness of the electrode package is completed".

时，可认为电极与封装后的缓冲层试样已良好接触，位置传感器读取两电极之间距离d₂。Step 7: The user puts the packaged buffer layer sample to be tested between the two electrodes, and selects the "Measurement" function of the volume resistivity detection device. Touch, pay attention to safety", apply a low-voltage DC voltage between the upper and lower electrodes, and the transmission mechanism controls the upper electrode to drop slowly. When the relative error of the two current measurement values I ₁ and I ₂ sampled at the approaching moment is less than the threshold of the channel, that is

, it can be considered that the electrode is in good contact with the packaged buffer layer sample, and the position sensor reads the distance d ₂ between the two electrodes.

即/>

时，传动机构使上电极保持静止，此时缓冲层弹性形变幅度与在电缆内部时形变幅度一致，上电极保持静止。Step 8, the transmission mechanism controls the upper electrode to drop slowly at a slower speed, and the sensor continuously reads the distance d _c between the two electrodes, when the

i.e. />

, the transmission mechanism keeps the upper electrode still. At this time, the elastic deformation range of the buffer layer is consistent with the deformation range when it is inside the cable, and the upper electrode remains static.

Step 9: Gradually increase the DC voltage between the upper and lower electrodes until the current I detected by the ammeter reaches the threshold of the channel current, that is, keep the DC voltage constant for t seconds when I>I _valid , so as to eliminate charging Current influence.

Step 10, read the voltmeter U, the ammeter reading I, and calculate the volume resistivity of the buffer layer based on the electrode area S and other information

In step 11, the calculation result of the volume resistivity is displayed on the display screen, as shown in Table 3, and the conclusion whether the volume resistivity is qualified or not is given according to the corresponding standard. The volume resistivity detection of the buffer layer is completed.

table 3

result U(V) I(A) S(m ² ) d ₂ (m) d ₁ (m) σ(Ω·m) value 4.5 0.0118 0.001963 0.00599 0.00031 130.60

At present, the volume resistivity requirement in JB/T 10259-2014 "Water-blocking tape for cables and optical cables" is no more than 1000Ω·m, so the volume resistivity of the cable buffer layer is qualified.

It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive, so the present invention includes and is not limited to the embodiments described in the specific implementation, and those skilled in the art according to the technology of the present invention Other implementations derived from the scheme also belong to the protection scope of the present invention.

Claims (8)

1. The volume resistivity detection device of the flat sheath buffer layer is characterized in that: it includes a detector and an electrode package, wherein the detector includes a user input terminal, a display screen, a processing calculation unit, a memory, a base, a bracket, an upper electrode, and a lower electrode , a transmission mechanism, a position sensor, a DC voltage source and a switch; the bracket is installed above the base, and the transmission mechanism is installed on the out-of-the-box end, and the transmission mechanism moves up and down along the vertical direction of the out-of-the-box end, and the upper electrode is installed on the bottom of the transmission mechanism The lower electrode is installed above the bracket corresponding to the installation position of the upper electrode, and a position sensor is installed next to the lower electrode. An input terminal is arranged above the surface of the bracket, a display screen and a switch are arranged below the surface of the bracket, and a processing calculation unit and a memory are arranged inside the bracket. , DC voltage source, voltmeter, ammeter and protective resistor. 2. The volume resistivity detection device of the flat sheath buffer layer according to claim 1, characterized in that: the electrode package is provided with a sealing port above, and a vacuum port is provided below, and the electrode package is filled with a buffer layer. 3. The volume resistivity detection device of the flat sheath buffer layer according to claim 1, characterized in that: the memory is connected to a processing and computing unit for storing data, and the processing and computing unit is respectively connected to an ammeter and a voltmeter. 4. The flat sheath buffer layer volume resistivity detection device according to claim 1, characterized in that: the upper electrode is connected in series with the protective resistor, the switch is connected to the positive pole of the DC voltage source, the negative pole of the DC voltage source is connected in series with the ammeter and The lower electrode, the upper electrode and the lower electrode are connected through the electrode package, and the two ends of the upper electrode and the lower electrode are connected in parallel with a voltmeter. 5. The device for detecting volume resistivity of buffer layer of flat sheath according to claim 1, characterized in that: the base is an insulating base. 6. a detection method of the flat sheath buffer layer volume resistivity detection device as described in any one of claims 1 to 5, is characterized in that, comprises the following steps: Step 1. Obtain the cable parameters according to the cable factory test report or actual measurement results; Step 2. Disassemble the cable outer sheath and the flat metal sheath, quickly cut the wrapped and covered buffer layer, put it into the electrode package for sealing, and make a standard buffer layer sample and a tested buffer layer sample ; Step 3, turn on the switch, input the cable parameters and the short circuit threshold, the access threshold, the access current threshold and the charging current time at the user input terminal, and store the parameters in the memory; Step 4. Place the standard buffer layer sample between the upper electrode and the lower electrode, apply a low-voltage DC voltage through a DC voltage source, and control the upper electrode to slowly drop through the transmission mechanism; Step 5. When the reading of the ammeter exceeds the short-circuit threshold, read the measured value I ₁ of the ammeter, the upper electrode and the lower electrode are fully in contact with the standard buffer layer sample, and read the distance d ₁ between the upper electrode and the lower electrode of the position sensor; Step 6. Stop applying the low-voltage DC voltage, and control the upper electrode to slowly rise to the initial position through the transmission mechanism; Step 7. Place the sample of the buffer layer to be tested between the upper electrode and the lower electrode, apply a low-voltage DC voltage through a DC voltage source, and control the upper electrode to drop slowly through the transmission mechanism, and obtain the measured value I ₂ of the galvanometer. When the galvanometer When the relative error between the measured value _I1 and the ammeter measured value _I2 is less than the access threshold, the upper electrode and the lower electrode are in full contact with the buffer layer sample to be tested, and the distance _d2 between the upper electrode and the lower electrode of the position sensor is read; Step 8. Control the upper electrode of the transmission mechanism to drop slowly at a slower speed, and the sensor continuously reads the distance d _c between the two electrodes.

and />

, the transmission mechanism keeps the upper electrode still, at this time, the elastic deformation range of the buffer layer is consistent with the deformation range when it is inside the cable, and the upper electrode remains static; Step 9. Gradually increase the DC voltage between the upper electrode and the lower electrode until the current I detected by the ammeter reaches the channel current threshold. When I>I _valid , keep the DC voltage constant for t seconds, and exclude the charging current Influence; Step 10, read the voltmeter U, the ammeter indication I, and calculate the volume resistivity of the measured buffer layer according to the electrode area S

Where d _Al is the nominal value of the inner radius of the flat metal sheath, d _OB is the nominal value of the outer radius of the cable with insulation and shielding, and t _hc is the nominal value of the product of the single-layer thickness of the buffer layer and the number of wrapping layers; In step 11, display the calculation result of the volume resistivity of the buffer layer under test on the display screen, and give a conclusion whether the volume resistivity of the buffer layer under test is qualified according to the corresponding standards. 7. The detection method of the flat sheath buffer layer volume resistivity detection device according to claim 6, characterized in that: the cable parameters in the step 1 include: flat metal sheath inner radius _dAl nominal value, including insulation The nominal value of the outer radius d _OB of the shielded cable, the product of the single-layer thickness of the buffer layer and the number of wrapping layers t _hc the nominal value. 8. The detection method of the flat sheath buffer layer volume resistivity detection device according to claim 6, characterized in that: the specific implementation method of the step 2 is: dismantling the cable outer sheath and the flat metal sheath , the buffer layer maintains the initial state of the wrapping and covering in the cable, and the surface can cover the conductor electrodes on both sides of the electrode package. After sealing the electrode package, extract the air in the package for sealed storage, and use it as a sample of the buffer layer after packaging .

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