Test method for temperature measurement sensitivity of temperature measurement optical fiber with built-in cable

Abstract

The application discloses a test method for temperature measurement sensitivity of a built-in temperature measurement optical fiber in a cable, which comprises the following steps: S1, providing a cable; S2, placing the cable; S3, passing the cable through a through-type step-up transformer and short-circuiting both ends of the cable through a conductor; S4, connecting an optical fiber in the cable to a temperature measurement system and setting an alarm temperature; S5, selecting a monitoring point on the cable and placing a thermal couple in the cable at the monitoring point; S6, applying a current to the cable through the transformer, making the conductor heat up and keeping the temperature, recording the temperature value of the thermal couple and a temperature measurement curve of the temperature measurement system; S7, placing an external heat source on one side of the thermal couple, setting a running temperature of the external heat source and keeping the temperature, recording the temperature value of the thermal couple and a temperature measurement curve; S8, comparing whether the temperature value of the thermal couple in S6 and the cable temperature value measured by the optical fiber in the temperature measurement system are consistent; comparing whether the temperature value measured by the optical fiber in the temperature measurement system and the temperature value of the thermal couple after the external heat source is applied in S7 are consistent; and comparing whether the position of a curve mutation in the temperature measurement curve and the position of the heat source are consistent.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, and specifically to a test method for the temperature sensitivity of an optical fiber for temperature measurement embedded in a cable. Background Technology

[0002] Investigations revealed that when cables in power grids experience faults, the internal temperature of most cable conductors rises prematurely. To achieve early warning of faults throughout the cable's lifecycle, temperature-sensing optical fibers could be placed inside the cable to monitor temperature changes in the corresponding structures in real time. When a sudden temperature change occurs within the cable, the location of the change point could be simultaneously determined. However, the sensitivity of this method of monitoring cable temperature changes using internal temperature-sensing optical fibers needs to be verified, and currently, there is no satisfactory method to verify the sensitivity of embedded temperature-sensing optical fibers in cables. Summary of the Invention

[0003] The purpose of this invention is to address the current lack of a suitable method for verifying the temperature sensitivity of fiber optic cables. This invention provides a simple and easy-to-operate test method for verifying the temperature sensitivity of fiber optic cables embedded in cables. The test method provided by this invention can achieve temperature monitoring while accurately locating temperature change points. This method can be widely used for testing and verifying the temperature sensitivity of fiber optic cables embedded in high, medium, and low voltage cables.

[0004] This invention is achieved through the following technical solution:

[0005] A test method for the temperature sensitivity of an optical fiber for temperature measurement embedded in a cable, characterized by the following steps:

[0006] S1. Provide a cable to be tested; the cable includes: a conductor, an insulation layer, a metal shielding layer and an outer sheath wrapped from the inside out, wherein the conductor contains a conductor optical fiber and the metal shielding layer contains a shielding layer optical fiber.

[0007] S2. Let the cable stand still, ready for use;

[0008] S3. Pass the cable through the through-type current-boosting transformer, and then short-circuit the two ends of the cable through the conductor and fix it.

[0009] S4. Connect the conductor optical fiber and the shielding layer optical fiber to the distributed optical fiber temperature measurement system and set the alarm temperature of the distributed optical fiber temperature measurement system.

[0010] S5. Select several monitoring points on the cable, and place thermocouples on the conductor surface and the metal shielding layer surface at the corresponding monitoring point locations to measure the temperature.

[0011] S6. Apply current to the cable through the through-core current-raising transformer to raise the conductor to the rated operating temperature and maintain it, and record the temperature value of the thermocouple and the temperature measurement curve of the distributed optical fiber temperature measurement system.

[0012] S7. Based on the monitoring point location selected in step S5, place an external heat source on one side of each thermocouple, set and maintain the operating temperature of the external heat source, and then record the temperature value of the thermocouple and the temperature measurement curve of the distributed optical fiber temperature measurement system again.

[0013] S8. Compare whether the temperature value of the thermocouple in step S6 is consistent with the cable temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system; compare whether the temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system is consistent with the temperature value of the thermocouple after an external heat source is applied in step S7; compare whether the position of the curve abrupt change in the temperature measurement curve is consistent with the position of the heat source.

[0014] Specifically, the method provided by this invention for verifying the temperature sensing sensitivity of a cable's built-in temperature-sensing optical fiber is as follows: the internal temperature of the cable is monitored by connecting the internal optical fiber to a distributed optical fiber temperature measurement system; a feedthrough current-boosting transformer is used to provide the cable with rated current to ensure that the cable reaches its rated operating temperature; and an external heat source is used to introduce a temperature surge to verify the sensitivity of the optical fiber temperature sensing.

[0015] When thermocouple temperature monitoring is performed on the corresponding cable structure, the results of fiber optic monitoring at the corresponding location are compared. The method of introducing an external heat source via cable is used to verify the temperature measurement sensitivity.

[0016] When the test sample is short, it can be extended by externally connecting the same optical fiber as the built-in optical fiber of the cable to achieve temperature sensitivity verification.

[0017] Furthermore, the test method for the temperature sensing sensitivity of the built-in temperature-sensing optical fiber in the cable: the voltage rating of the cable in step S1 is 21 / 35kV, and the specification is 1×300mm. 2 The length shall be no less than 100 meters.

[0018] Further, the test method for the temperature measurement sensitivity of the built-in temperature measuring fiber in the cable: Step S2, place the cable in an environment with a temperature of 20±2℃ and a relative humidity of 40-60% for 12-24 hours, and wait for use.

[0019] Further, the test method for the temperature sensitivity of the built-in temperature measuring fiber in the cable is as follows: Step S5: Select two monitoring points on the cable, with a distance of not less than 50 meters between the two monitoring points and a distance of not less than 20 meters from both ends of the cable. Place thermocouples on the conductor surface and the surface of the metal shielding layer at the corresponding monitoring point locations to measure the temperature.

[0020] Further, the test method for the temperature sensitivity of the built-in temperature measuring fiber in the cable: Step S5, if it is necessary to monitor the temperature of the surface of other cable structures besides the conductor and metal shielding layer, place the corresponding number of thermocouples on their surfaces.

[0021] If it is necessary to monitor the temperature of the cable surface other than the conductor and metal shielding layer, an appropriate number of thermocouples should be placed on the surface. The number of monitoring points selected for the cable can be increased appropriately.

[0022] Furthermore, the test method for the temperature measurement sensitivity of the built-in temperature measuring fiber in the cable is as follows: in step S6, the rated operating temperature is 90℃±3℃, and the holding time is 2-4 hours.

[0023] Furthermore, the test method for the temperature measurement sensitivity of the built-in temperature measuring fiber in the cable is as follows: the operating temperature of the external heat source set in step S7 is 150℃±3℃, and the holding time is 1-3 hours.

[0024] This invention provides a test method for the temperature measurement sensitivity of cables with built-in optical fiber temperature sensing, used to verify cables with built-in optical fiber, realize the monitoring of temperature changes in the internal conductor and insulation layer of the cable, and verify the sensitivity of optical fiber temperature measurement. The method of this invention simulates the temperature changes of the conductor and insulation under conditions such as the rated operating temperature of the cable and an external heating source, and observes the changes in the cable temperature monitoring curve and the corresponding relationship between the position and the temperature and position of the external heating source in the distributed optical fiber temperature measurement system, so as to verify the sensitivity of optical fiber temperature measurement.

[0025] The beneficial effects of this invention are:

[0026] (1) The method for verifying the temperature sensitivity of the built-in temperature measuring fiber in the cable designed in this invention can achieve temperature monitoring and precise location of temperature change points at the same time. The method of this invention can be widely used in the test verification of the temperature sensitivity of the built-in temperature measuring fiber in high, medium and low voltage cables.

[0027] (2) The method of the present invention simulates the actual operation of the cable and designs a test method for the temperature sensitivity of the cable built-in optical fiber, thereby verifying the accuracy of the optical fiber in monitoring the temperature change of the cable; ensuring that the cable with built-in temperature measuring optical fiber meets the customer's needs and provides strong support for the customer's cable application in the future.

[0028] (3) The method for verifying the temperature sensitivity of the built-in temperature measuring fiber in the cable provided by the present invention is easy to operate, has low test cost, and has good application prospects in the field of cable manufacturing. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This invention provides a schematic diagram illustrating the principle of temperature sensitivity testing using a built-in fiber optic cable for temperature measurement.

[0031] The diagram is labeled as follows: 1. Cable, 2. Through-core current-boosting transformer, 3. Distributed fiber optic temperature measurement system, 4. Thermocouple, 5. External heat source, 1-1. Conductor, 1-2. Insulation layer, 1-3. Metal shielding layer, 1-4. Outer sheath, 1-1-1. Conductor fiber optic cable, 1-3-1. Shielding layer fiber optic cable. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicating orientation or positional relationships, are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0034] Example 1

[0035] Test method for the temperature sensing sensitivity of the built-in temperature-sensing optical fiber in a cable: Select a cable with one optical fiber placed in the conductor and one in the metal shielding layer, and conduct a temperature sensing sensitivity verification test on the internal optical fiber. The specific verification method includes the following steps, combined with... Figure 1 A detailed description of the methods and steps is provided below:

[0036] S1. A cable 1 to be tested is provided; the cable 1 includes: a conductor 1-1, an insulation layer 1-2, a metal shielding layer 1-3, and an outer sheath 1-4, which are sequentially wrapped from the inside out. The conductor 1-1 contains a conductor optical fiber 1-1-1, and the metal shielding layer 1-3 contains a shielding optical fiber 1-3-1; wherein the voltage rating of the cable 1 is 21 / 35kV, and the specification is 1×300mm. 2 It is 100 meters long;

[0037] S2. Place the above-mentioned cable 1 in an environment with a room temperature of 20°C and a relative humidity of about 50% for 24 hours, and wait for use;

[0038] S3. Pass the cable 1 through the through-type current-boosting transformer 2, then short-circuit the two ends of the cable 1 through the conductor 1-1 and fix it.

[0039] S4. Connect the conductor fiber 1-1-1 and the shielding fiber 1-3-1 in the cable 1 to the distributed fiber optic temperature measurement system 3, and set the alarm temperature of the distributed fiber optic temperature measurement system 3.

[0040] S5. Select two monitoring points on the cable 1, ensuring that the distance between the two monitoring points is not less than 50 meters and the distance between the monitoring points and both ends of the cable 1 is not less than 20 meters. Then, place thermocouples 4 on the surface of conductor 1-1 and metal shielding layer 1-3 at the corresponding monitoring point locations to measure the temperature. If it is necessary to monitor the temperature of other cable structure surfaces besides conductor 1-1 and metal shielding layer 1-3, a corresponding number of thermocouples 4 should be placed on their surfaces. The number of monitoring points selected for the cable can be increased appropriately.

[0041] S6. Apply current to the cable 1 through the through-core current-boosting transformer 2 to raise the temperature of the conductor 1-1 to the rated operating temperature (90℃±3℃) and maintain it for 4 hours. Then record the temperature value of the thermocouple 4 and the temperature measurement curve of the distributed optical fiber temperature measurement system 3.

[0042] S7. According to the monitoring point location selected in step S5, place an external heat source 5 on one side of each thermocouple 4, set the operating temperature of the external heat source 5 (about 150℃±3℃) and keep it for 2 hours, and then record the temperature value of the thermocouple 4 and the temperature measurement curve of the distributed optical fiber temperature measurement system 3 again.

[0043] S8. Compare whether the temperature value of thermocouple 4 in step S6 is consistent with the cable temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system 3; compare whether the temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system 3 is consistent with the temperature value of thermocouple 4 after the external heat source 5 is applied in step S7; compare whether the position of the curve change in the temperature measurement curve is consistent with the position of the heat source.

[0044] The experimental conclusions of Example 1 above are as follows:

[0045] (1) In the first stage, when the temperature of conductor 1-1 rises to the rated operating temperature of 90℃±3℃, it stabilizes for 4 hours. The temperature value of the thermocouple and the temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system are consistent.

[0046] (2) In the second stage, the fiber optic temperature measurement system can identify the simulated high-temperature fault point. The error range is within the accuracy range of the temperature measurement system. The temperature measurement system alarm can identify that the conductor temperature exceeds the standard.

[0047] If the above requirements are met, it means that the temperature measurement sensitivity achieved by the optical fiber meets the requirements.

[0048] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A test method for temperature sensing sensitivity of a temperature sensing optical fiber embedded in a cable, characterized by, The method comprises the following steps: S1, providing a cable (1) to be tested; the cable (1) comprises a conductor (1-1), an insulation layer (1-2), a metal shielding layer (1-3) and an outer sheath (1-4) arranged in sequence from inside to outside, the conductor (1-1) is internally provided with a conductor optical fiber (1-1-1), and the metal shielding layer (1-3) is internally provided with a shielding layer optical fiber (1-3-1); S2, placing the cable (1) and waiting; S3, passing the cable (1) through a through-type current increasing transformer (2), then short-circuiting and fixing the two ends of the cable (1) through the conductor (1-1); S4, connecting the conductor optical fiber (1-1-1) and the shielding layer optical fiber (1-3-1) to a distributed optical fiber temperature measurement system (3) and setting an alarm temperature of the distributed optical fiber temperature measurement system (3); S5, selecting a plurality of monitoring points on the cable (1), and placing thermocouples (4) on the surfaces of the conductor (1-1) and the metal shielding layer (1-3) at the corresponding monitoring point positions to measure the temperature; S6, applying a current to the cable (1) through the through-type current increasing transformer (2), so that the conductor (1-1) is heated to a rated operating temperature and kept, and the temperature value of the thermocouple (4) and the temperature measurement curve of the distributed optical fiber temperature measurement system (3) are recorded; S7, according to the monitoring point positions selected in step S5, placing an external heat source (5) on one side of each thermocouple (4), setting an operating temperature of the external heat source (5) and keeping, then recording the temperature value of the thermocouple (4) and the temperature measurement curve of the distributed optical fiber temperature measurement system (3) again; S8, comparing whether the temperature value of the thermocouple (4) in step S6 and the cable temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system (3) are consistent; comparing whether the temperature value measured by the optical fiber in the distributed optical fiber temperature measurement system (3) and the temperature value of the thermocouple (4) are consistent after the external heat source (5) is applied in step S7; comparing whether the position of the curve mutation in the temperature measurement curve and the position of the heat source are consistent.

2. The test method for temperature sensing sensitivity of the cable-embedded temperature sensing optical fiber according to claim 1, characterized by, Voltage class 21 / 35 kV, size 1 x 300 mm for the cable (1) in step S1 2 with a length of not less than 100 meters.

3. The test method for temperature sensing sensitivity of the cable-embedded temperature sensing optical fiber according to claim 1, characterized by, In step S2, the cable (1) is placed in an environment with a temperature of 20±2℃ and an air relative humidity of 40-60% for 12-24 hours and is ready for use.

4. The test method for temperature sensing sensitivity of the cable-embedded temperature sensing optical fiber according to claim 2, characterized by, In step S5, two monitoring points are selected on the cable (1), the distance between the two monitoring points is not less than 50 meters, and the distance from the two ends of the cable (1) is not less than 20 meters, thermocouples (4) are placed on the surfaces of the conductor (1-1) and the metal shielding layer (1-3) at the corresponding monitoring point positions, and the temperature is measured.

5. The test method for temperature sensing sensitivity of the cable-included temperature sensing optical fiber according to claim 1, characterized by, In step S5, if it is necessary to monitor the temperature of the surface of other structures of the cable (1) except the conductor (1-1) and the metal shielding layer (1-3), a corresponding number of thermocouples (4) are correspondingly placed on the surfaces thereof.

6. The test method for temperature sensing sensitivity of the cable-included temperature sensing optical fiber according to claim 1, characterized by, In step S6, the rated operating temperature is 90℃±3℃, and the keeping time is 2-4 hours.

7. The test method for temperature sensing sensitivity of the cable-included temperature sensing optical fiber according to claim 1, characterized by, In step S7, the operating temperature of the external heat source (5) is set to 150℃±3℃, and the keeping time is 1-3 hours.

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