CN112097982A - Method for measuring interface pressure of cable intermediate joint under action of electric field and temperature difference - Google Patents
Method for measuring interface pressure of cable intermediate joint under action of electric field and temperature difference Download PDFInfo
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- CN112097982A CN112097982A CN202010968073.5A CN202010968073A CN112097982A CN 112097982 A CN112097982 A CN 112097982A CN 202010968073 A CN202010968073 A CN 202010968073A CN 112097982 A CN112097982 A CN 112097982A
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- electric field
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G7/00—Overhead installations of electric lines or cables
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Abstract
The invention discloses a method for measuring interface pressure of a cable intermediate joint under the action of an electric field and temperature difference, which comprises a current source connected in series with a copper conductor bar, a voltage source connected in series between copper nets, two layers of copper nets wound on the outer surfaces of an expanded silicone rubber tube and a polyethylene bar respectively, a layer of silicone grease coated between the expanded silicone rubber tube and the polyethylene bar interface, a plurality of micro stress piece sensors, a pressure reading module connected in series on a micro stress piece and a constant temperature drying box. The invention has reasonable design, and simulates the real situation that the temperature of the copper shield does not have load current when the cable joint actually runs, and the temperature of the copper shield is close to the room temperature due to the fact that only the copper core conductor has ohmic heat at the joint, thereby causing the internal and external temperature difference of the expanded silicone rubber tube. Meanwhile, the stress sheet for measuring the pressure is not influenced by an electric field, and the phenomena of interface discharge and breakdown are not caused, so that the measurement of the interface pressure under the action of the electric field is more accurate.
Description
Technical Field
The invention belongs to the technical field of explosion-proof early warning of electrical equipment, and particularly relates to a method for measuring interface pressure of a cable intermediate joint under the action of an electric field and temperature difference.
Background
Compared with overhead transmission lines, the power cable has the advantages of light weight, small occupied area, convenience in maintenance, small environmental influence and the like, so that the power cable is widely applied to a power system, and the operation reliability of the power cable is directly related to the stability and safety of the operation of a power grid system. Due to the restriction of factors such as manufacturing level, construction conditions, environmental conditions and the like, a cable joint is easy to become a weak link of a cable, and partial discharge or insulation aging and other conditions occur during operation, so that the interface pressure between a silicon rubber/polyethylene interface of the cable joint is reduced, and finally, the interface pressure is reduced to be out of an allowable range, so that local temperature rise is too high, explosion is caused in severe cases, and serious economic loss and casualties are caused. Therefore, the real-time monitoring device for the interface pressure of the power cable has important application value.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for measuring the interface pressure of the cable intermediate joint under the action of an electric field and temperature difference aiming at the defects of the prior art.
The technical scheme adopted by the invention is as follows: a method for measuring the interface pressure of cable intermediate joint under the action of electric field and temp difference includes a current source serially connected to copper conductor rod, a voltage source serially connected between copper nets, two copper nets wound around the external surfaces of silicon rubber tube and polyethylene rod in expanded state, a layer of silicone grease coated between the silicon rubber tube and polyethylene rod interface in expanded state, multiple miniature stress sheet sensors, a pressure reading module serially connected to miniature stress sheet, and a constant-temp drying box.
The current source is connected in series with the copper conductor bar and is used for supplying current to the copper conductor bar, and the copper conductor bar generates heat under the action of alternating current, so that when heat is transferred outwards through the polyethylene bar and the insulation medium of the expanded silicone rubber tube, temperature differences are generated at different positions in the radial direction of the expanded silicone rubber tube; the voltage source connected in series between the copper nets is used for generating alternating voltage; the copper net only has alternating voltage provided by a voltage source and does not have circulating current, so that the real condition that no load current flows on the outer layer of the cable in actual cable operation is simulated; the two layers of copper nets are respectively wound between the expanded silicone rubber tube and the polyethylene rod and are used for forming a uniform electric field between the expanded silicone rubber tube and the polyethylene rod under the action of voltage; the layer of silicone grease coated between the interfaces of the expanded silicone rubber tube/polyethylene rod is used for filling gaps at uneven positions of the interfaces so as to enable the interfaces to be flat. The micro stress sheet sensors are used for measuring the stress between the interfaces of the expanded silicone rubber tube and the polyethylene rod and transmitting the measured stress between the interfaces to the pressure reading module; the pressure reading module connected in series on the micro stress sheet is used for collecting and reading a stress value transmitted by the stress sensor, and has the functions of stress value display and low threshold alarm; the constant-temperature drying box is used for simulating an environment in which the temperature of the cable accessory is difficult to change during actual operation;
preferably, the copper mesh has a uniform texture and a smooth surface, and no burrs are left on the surface after being wound on the polyethylene rod and the expanded silicone rubber tube.
Preferably, only the alternating voltage provided by the voltage source exists on the copper net without flowing current, so that the real situation that no load current flows in the outer layer of the cable in actual cable operation is simulated, and the outer side of the expanded silicone rubber tube is close to the room temperature and is only influenced by the temperature difference formed by the current thermal effect generated by the alternating current flowing in the inner copper conductor bar.
Preferably, the silicone grease has good fluidity and can flow to the gap of the interface and fill the gap.
Preferably, the thickness of the micro stress sheet sensor sleeved on the cable joint is extremely small.
Preferably, the micro stress sheet sensor sleeved on the cable joint can be bent and attached to the surface of the polyethylene rod in a proper amount.
Preferably, the micro-strain gage sensor looped over the cable connector can be secured in a designated installation monitoring position.
Preferably, the micro stress sheet sensor sleeved on the cable joint is reset to zero after the installation is finished.
Preferably, the stress sheet reading module sleeved on the cable joint in the ring sets an alarm threshold value after the installation is finished.
Preferably, the series connection is arranged outside the copper mesh (namely, the uniform electric field) of the micro stress sheet sensor, so that the stress sheet sensor is prevented from being influenced by the electric field to cause reading errors, interface discharge and breakdown phenomena are avoided, and the measurement of the interface pressure under the action of the electric field is more accurate.
The method has reasonable design, can know the interface pressure state of the expansion-state silicon rubber/polyethylene interface of the cable intermediate joint in time, reduces unnecessary maintenance tests, also reduces the occurrence of fire and explosion accidents of the cable, further obviously improves the reliability and safety of power supply, and provides conditions for converting planned maintenance or post-accident rush repair into state maintenance.
Drawings
Fig. 1 is a schematic diagram of the principle of the present invention.
Detailed Description
The invention will be described in further detail with reference to the following drawings and specific embodiments.
Examples
As shown in fig. 1, the present embodiment provides a method for measuring interface pressure of cable intermediate joint under the action of electric field and temperature difference, which includes a current source connected in series to a copper conductor bar, a voltage source connected in series between copper nets, a layer of silicone grease coated between the interface of expanded silicone rubber tube/polyethylene bar, two layers of copper nets respectively wound around the outer surfaces of the expanded silicone rubber tube and the polyethylene bar, a plurality of micro stress sheet sensors, a pressure reading module connected in series to the micro stress sheets, and a thermostat with temperature slightly higher than room temperature.
The current source is used for electrifying the copper conductor rod, the electrified copper conductor can generate heat, and the heat can be transferred layer by layer in the radial direction, so that the temperature difference exists inside and outside the expansion-state silicone rubber tube, and the condition that the temperature difference exists inside and outside the expansion-state silicone rubber tube when the actual cable joint operates is simulated. The voltage source is used for electrifying the copper mesh, so that a uniform electric field is generated between the two layers of copper meshes, and the condition that the expanded silicone rubber is in the electric field when the actual cable joint operates is simulated. The copper net only has alternating voltage provided by the voltage source and does not have circulating current, so that the real situation that no load current flows on the outer layer of the cable in actual cable operation is simulated. Therefore, the outer side of the expanded silicone rubber tube is close to the room temperature and is only influenced by the temperature difference formed by the current heat effect generated by the circulation of alternating current in the inner copper conductor bar. And a layer of silicone grease coated between the interfaces of the expanded silicone rubber tube/polyethylene rod is used for filling gaps at the interfaces and simulating the silicone grease environment of the expanded silicone rubber when the actual cable joint operates. The micro sensor is arranged outside a copper mesh (namely an even electric field), so that reading errors caused by extrusion due to the fact that the stress sheet sensor is not influenced by the electric field are avoided, interface discharge and breakdown phenomena cannot be caused, and therefore real-time measurement of interface pressure between the expansion-state silicon rubber tube/polyethylene rod interfaces under the action of the electric field is accurate. The pressure measured by the stress sheet sensor transmits data to the pressure reading module through the transmission line, the pressure reading module displays the interface pressure value measured in real time, and when the interface pressure is monitored to be smaller than the critical pressure value, an alarm is sent out to remind a maintainer to replace a cable connector.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification and replacement based on the technical solution and inventive concept provided by the present invention should be covered within the scope of the present invention.
Claims (10)
1. A method for measuring the interface pressure of a cable intermediate joint under the action of an electric field and temperature difference comprises a current source (1) connected in series on a copper conductor bar, a voltage source (2) connected in series between copper nets, two layers of copper nets (3) respectively wound on the outer surfaces of an expanded silicone rubber tube and a polyethylene bar, a layer of silicone grease (4) coated between the expanded silicone rubber tube and the polyethylene bar interface, a plurality of miniature pressure sheet sensors (5), a pressure reading module (6) connected in series on a miniature stress sheet and a constant temperature drying box (7);
the method is characterized in that: the current source (1) connected in series with the copper conductor bar is used for introducing alternating current into the copper conductor bar, and the copper conductor bar generates heat under the action of the current, so that when heat is transferred outwards through the polyethylene bar and the insulation medium of the expanded silicone rubber tube, temperature differences are generated at different positions in the radial direction of the expanded silicone rubber tube; the voltage source (2) connected in series between the copper networks is used for generating alternating voltage; the copper net (3) only has alternating voltage provided by the voltage source (2) but does not have circulating current, so that the real situation that no load current flows on the outer layer of the cable in actual cable operation is simulated; the two layers of copper nets (3) are respectively wound between the expanded silicone rubber tube and the polyethylene rod and are used for forming a uniform electric field between the expanded silicone rubber tube and the polyethylene rod under the action of voltage; the layer of silicone grease (4) coated between the interfaces of the expanded silicone rubber tube/polyethylene rod is used for filling gaps at the interfaces; the plurality of micro pressure sheet sensors (5) are used for measuring the stress between the interfaces of the expanded silicone rubber tube and the polyethylene rod and transmitting the measured stress between the interfaces to the pressure reading module (6); the pressure reading module (6) connected in series on the micro stress sheet is used for collecting and reading a stress value transmitted by the pressure sensor (5), and has the functions of stress value display and low threshold alarm; the constant-temperature drying box (7) is used for simulating an environment in which the temperature is difficult to change when the cable accessory is actually operated.
2. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the copper net only has alternating voltage provided by the voltage source and does not have circulating current, so that the real condition that no load current flows on the outer layer of the cable in actual cable operation is simulated, the outer side of the expansion-state silicone rubber tube is close to room temperature and is only influenced by temperature difference formed by current heat effect generated by the circulation of the alternating current in the inner copper conductor bar.
3. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the two layers of copper nets (3) respectively wound between the expanded silicone rubber tube and the polyethylene rod are uniform in texture, smooth in surface and free of protrusions or depressions.
4. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the thickness of the plurality of micro stress patch sensors (5) is extremely small.
5. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the plurality of micro stress sheet sensors (5) can be bent in a proper amount.
6. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the plurality of micro stress patch sensors (5) are pressure calibrated in advance.
7. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the values of the micro stress sheet sensors (5) return to zero after the installation is finished.
8. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: and the pressure reading module (6) connected in series on the micro stress sheet sensor (5) sets an alarm threshold value after the installation is finished.
9. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the series connection is arranged outside the copper mesh (namely, the uniform electric field) of the micro stress sheet sensor (5), so that the stress sheet sensor (5) is prevented from being influenced by the electric field to cause reading errors, interface discharge and breakdown phenomena are avoided, and the measurement of the interface pressure under the action of the electric field is more accurate.
10. The method for measuring the interface pressure of the cable intermediate joint under the action of the electric field and the temperature difference as claimed in claim 1, wherein: the whole interface pressure real-time monitoring device is arranged in a constant-temperature drying box (7).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113237587A (en) * | 2021-02-02 | 2021-08-10 | 国网电力科学研究院武汉南瑞有限责任公司 | Cable joint interface pressure measurement system |
| CN113740676A (en) * | 2021-07-27 | 2021-12-03 | 中国电力科学研究院有限公司 | Cable joint double-layer medium interface flashover voltage test device |
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