XLPE cable insulation multi-stress coupling accelerated aging device, method and application

Abstract

The invention relates to an XLPE cable insulation multi-stress coupling accelerated aging device and method and application, and the method comprises the following steps: taking thermal aging stress, electrical aging stress and mechanical aging stress as aging stress forms which can be applied by the device according to aging factor characteristics of an XLPE cable under actual application conditions; the applied magnitude of three aging stresses can be adjusted, and an orthogonal test group of thermal, electrical and mechanical aging stresses is set, so that the influence degree of different aging stress application conditions on the insulation aging of the XLPE cable can be analyzed; two kinds of aging electrodes are arranged for subsequent different aging degree verification tests, and the two kinds of aging electrodes are a dumbbell-shaped sample target electrode customized for a mechanical tensile test and a square sample target electrode designed for general physicochemical electrical properties; by means of the equipment and the matched method, multi-stress accelerated aging treatment can be conducted on XLPE cable insulation, and the effect of providing a basic material for follow-up cable insulation life analysis is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of XLPE cable insulation aging, and in particular to a multi-stress coupling aging device, method and application for XLPE cable insulation. Background Art

[0002] Cross-linked polyethylene insulated power transmission cables (XLPE cables) are important hub devices in the power system and are widely used in various fields of power transmission. However, due to various reasons such as complex operating environments, increased service life, and delayed maintenance cycles, the insulation layer of XLPE cables will inevitably age. Common insulation aging stresses include: thermal stress, electrical stress, chemical stress, etc. If there are problems such as overload, overvoltage, and unreasonable cable assembly during operation, the aging degree will further increase. The aging degree of the insulation is directly related to the reliability and remaining life of the cable. It will have an impact on the operation of electrical equipment at least, and may even cause fires and a series of other consequences at worst. Therefore, the cable operation safety problems caused by insulation aging cannot be ignored.

[0003] Accelerated aging test is a common and effective method to test the insulation life of XLPE cables. According to the common stresses of insulation aging, the aging test can be subdivided into thermal aging test, electrical aging test, mechanical aging test, etc. Most of these aging tests test various aging stresses separately. However, in the actual environment, the aging stresses suffered by cable insulation mostly exist simultaneously. In order to simulate the real aging situation, the present invention mainly provides a multi-factor XLPE cable accelerated aging test system that can simultaneously simulate any combination of the coupling effects of thermal aging, electrical aging and mechanical aging, and can also set orthogonal test groups to simulate different aging stress degrees, so as to improve the accuracy and flexibility of the aging test.

[0004] Liang Yun of Chongqing University proposed a XLPE insulation aging test device that can study the aging under the action of temperature, water content and AC electric field in his master's thesis "Research on Aging Evaluation Method of Cross-linked Polyethylene Insulation under the Synergistic Action of Multiple Factors". The device designed a set of electrothermal aging test system and obtained different thermal stresses, electrical stresses and humidity by soaking the insulation specimens before the test. However, the test system used a column-type electric voltage regulator, which could only provide power frequency voltage and did not well reflect the electrical aging effect of harmonics, frequency-doubling components, etc. generated during the actual operation of the cable. Moreover, the designed aging tank was too heavy, which would cause the problem that the internal transformer oil temperature did not reach the aging standard while the external temperature had reached the aging standard to a certain extent. Zhong Wenxin et al. from Xi'an Jiaotong University applied for an invention patent "Multi-factor Aging Platform and Experimental Method for Cable Silicone Rubber Insulation Material", which proposed an electro-thermal-mechanical multi-factor combined aging device that met the actual operating conditions. By setting the elongation displacement of the insulation specimen under different elongation rate tensile states, different aging stresses were set for the AC high-voltage electrode and the blast drying aging oven. Although this device considered the mechanical stress acting during the actual operation of the cable, only tensile stress was set, and no detailed test was set to simulate other forms of mechanical stress borne by the cable insulation during use. Fan Xinghui of South China University of Technology proposed an electrothermal combined aging device in his master's thesis "Research on the Characteristics and State Evaluation of Electrothermal Combined Aging of High-voltage Cable Insulation". By coiling the cable into an 8-shaped to offset the magnetic flux and directly applying high voltage to the cable to form a large current to apply electrical stress and thermal stress at the same time, this method was efficient and simple, but it was difficult to decouple the electrical stress and thermal stress, thus it was difficult to ensure the coupling independence of various stresses. Summary of the Invention

[0005] In order to solve the problem in the prior art that it is difficult to simultaneously apply thermal, electrical and mechanical stresses to the XLPE cable insulation for accelerated aging tests, in the first aspect of the present invention, a multi-stress aging test device for cable insulation layers is provided, including a variable-frequency series-resonant AC withstand voltage device and a thermal aging oven, and is characterized in that:

[0006] The variable-frequency series-resonant AC withstand voltage device is composed of a power frequency AC power supply, a variable-frequency power supply, an exciting transformer, a resonant reactor and a capacitive voltage divider connected in sequence, and provides an adjustable AC voltage as the electrical aging stress;

[0007] The thermal aging oven includes: hook weights, a telescopic spring clamp for providing mechanical tension parallel to the surface of the specimen; an adjusting nut for providing mechanical pressure perpendicular to the surface of the specimen; a three-dimensional variable-frequency vibration platform for applying mechanical vibration stress to the whole, and these three types of mechanical forces together serve as the mechanical aging stress for the XLPE insulation.

[0008] In the second aspect of the present invention, a multi-stress aging test method for cable insulation layers is provided. This method is based on the multi-stress aging test device for cable insulation layers described in claim 3, and is characterized in that: the mechanical aging stresses include extrusion stress, tensile stress, and vibration stress;

[0009] For the extrusion stress, the extrusion stress is adjusted by adjusting the external distance-adjusting nuts of the XLPE insulation aging cavity. The FSR thin-film pressure sensor attached near the grounding-side motor on the internal specimen is used to measure the extrusion pressure, and the measured extrusion pressure value is transmitted to the pressure sensor transmitter inside the high-temperature chamber above the encapsulation cup cover through a transmission line. The Bluetooth module equipped inside the transmitter can transmit the pressure data to an external device, thereby completing the control and monitoring of the extrusion force;

[0010] For the tensile stress, weights and a retractable spring clamp fixed at the bottom of the aging cavity are used for operation. When setting the tensile stress, first fix the specimen between the fixed insulation clamp of the aging cavity and the retractable spring insulation clamp without hanging weights, and fix the cavity on the plane with holes of the three-dimensional vibration platform. Then hang weights from below the vibration platform to the cavity. According to the formula that the pressure of the tensile force on the specimen should be the ratio of the gravity of the weights to the front area of the specimen, the front area of the dumbbell-shaped specimen is 1565.818 square millimeters, and the front area of the square specimen is 2500 square millimeters. (If the mass of the weights is m, in g, and the acceleration due to gravity is taken as 9.8 m / s 2 , S 试样 is the area of the selected specimen, then the tensile pressure on the specimen should follow:

[0011]

[0012] According to the above formula, the pressure of the tensile force on different specimens can be obtained by the mass of the weights, and the pressure of the tensile force on the specimen can be adjusted by adjusting the number of weights in each cavity;

[0013] For the vibration stress, a three-dimensional variable-frequency vibration platform is used. There are holes on the upper part of the platform to fix the XLPE insulation aging cavity and facilitate the installation of tensile weights. The vibration platform has a total of six motors and rubber springs, and the vibration effects in the up-down, left-right, and front-back directions are set to simulate the mechanical stresses suffered by the cable insulation during transportation, loading and unloading, and laying.

[0014] In the third aspect of the present invention, a cross-linked polyethylene insulated power transmission cable is provided, which is characterized in that: the cable is obtained through the above-mentioned multi-stress aging test device for cable insulation layers.

[0015] The fourth aspect of the present invention provides a cross-linked polyethylene insulated power transmission cable, characterized in that: the cable is obtained by the above-mentioned multi-stress aging test method for cable insulation layer.

[0016] The fifth aspect of the present invention provides a hub equipment for power system, which is applied to the field of power transmission and includes the above-mentioned cross-linked polyethylene insulated power transmission cable.

[0017] Beneficial effects

[0018] According to the aging stress conditions of XLPE cables under actual working conditions, the present invention simultaneously applies thermal stress, electrical aging stress, and mechanical aging stress to XLPE insulation specimens for accelerated aging tests, and sets up orthogonal test groups to arbitrarily combine the magnitudes of different aging stresses. The application of each stress factor is uniform throughout the aging process, effectively improving the accuracy and flexibility of the aging test, and solving the problem in the prior art that it is difficult to simultaneously apply thermal, electrical, and mechanical stresses to XLPE cable insulation for accelerated aging tests. Description of the drawings

[0019] Figure 1 It is a schematic diagram of the overall multi-stress coupling aging device for XLPE cable insulation specimens;

[0020] Figure 2 It is a schematic diagram of the multi-stress coupling aging cavity;

[0021] Figure 3 It is a schematic diagram of the SPWM waveform;

[0022] Figure 4 It is a schematic diagram of the principle of the variable-frequency resonant power supply;

[0023] Figure 5 It is a schematic diagram of the spherical electrode and the flat electrode;

[0024] Figure 6 It is a schematic diagram of the dumbbell-shaped specimen and the square specimen;

[0025] Figure 7 It is a schematic diagram of the FSR thin-film pressure sensor;

[0026] Figure 8 It is a schematic diagram of the placement groove of the aging cavity on the surface of the three-dimensional vibration platform. Detailed implementation manners

[0027] In the present invention, Figure 1 It is a schematic diagram of the overall multi-stress coupling aging device for XLPE cable insulation specimens. The whole device is composed of an AC high-voltage generating device, a thermal aging box, a multi-stress coupling aging cavity, and a three-dimensional mechanical vibration platform. Among them, the multi-stress coupling of the insulation specimens acts on the position as Figure 2At the insulating specimen in the multi-stress coupling aging cavity shown, the outer shell of the aging cavity is made of high-boron glass with excellent temperature resistance and insulation performance. Wiring electrodes are installed on both sides of the cavity, namely the high-voltage wiring terminal and the grounding wiring terminal. According to the different shapes of the insulating specimens used, spherical electrodes and flat electrodes are designed respectively; the bottom of the cavity is a telescopic spring insulating fixture; the top is a sealed cup cover with holes, connected to the pressure sensor transmitter encapsulated at the upper end. The bottom of the cup cover is a fixed insulating fixture. When conducting the multi-factor coupling aging test, first clamp the insulating specimen with the insulating fixtures at the upper and lower ends. Next, attach the FSR pressure sensor to the side of the specimen close to the grounding terminal. After installation, adjust the distance adjusting nuts on both sides of the electrodes to change the distance between the electrodes and clamp the specimen. The hook at the lower end of the cavity is used to hang the tensile hook weights.

[0028] Figure 3 As shown in the schematic diagram of the SPWM waveform, the electrical aging part of this device uses a variable-frequency series resonance AC high-voltage generating device. Through the IGBT of the variable-frequency resonance power supply and sine pulse width modulation (SPWM), the duty cycle of the output square wave is changed to obtain a sine wave voltage output.

[0029] Figure 4 As shown in the schematic diagram of the variable-frequency resonance power supply, the AC power supply becomes pulsating DC after passing through the bridge rectifier circuit, becomes smooth DC after capacitor filtering, and finally outputs AC with adjustable voltage and frequency through the inverter circuit. The adjustable frequency can ensure that the specimen can not only be electrically aged at power frequency, but also simulate the aging effects of non-power frequency components such as double frequency and harmonics on the specimen.

[0030] Figure 5 Schematic diagrams of the spherical electrode and the flat electrode Figure 6 Schematic diagrams of the dumbbell-shaped specimen and the square specimen; According to the aging characteristic analysis required after the aging test, this test device designs spherical electrodes and flat electrodes respectively for mechanical aging characteristic analysis and other aging characteristic analysis. The specimens are designed as dumbbell-shaped specimens and square specimens. Since the middle part of the dumbbell-shaped specimen is narrow, it is difficult for general flat electrodes to clamp it, so spherical electrodes with a smaller contact surface are used for the experiment.

[0031] Figure 7 As shown in the schematic diagram of the FSR thin-film pressure sensor, place the FSR thin-film pressure sensor at the end of the specimen close to the grounding terminal, which can measure the pressure on the specimen when tightening the distance adjusting nut and transmit it to the outside through the Bluetooth module in the pressure transmitter at the upper end of the cavity. It is not placed at the high-voltage end to prevent the sensor from directly contacting the high potential and causing breakdown.

[0032] Figure 8Schematic diagram of the placement groove for the aging cavity on the surface of the three-dimensional vibration platform. In order to prevent the aging cavity from falling off during the operation of the three-dimensional vibration platform and to provide space for hanging weights on the cavity, the three-dimensional vibration platform is hollowed out into 6 cavity placement grooves. Among them, the 100-mm square empty groove is used to place the aging cavity to prevent it from falling off, and the circular empty groove with an inner diameter of 70 mm is used to provide sufficient space for the weights below.

[0033] Next, we will further elaborate on the multi-stress coupling accelerated aging device and method for XLPE cable insulation.

[0034] According to the aging stress conditions of XLPE cables under actual working conditions, the present invention simultaneously applies thermal stress, electrical aging stress, and mechanical aging stress to the XLPE insulation specimen for an accelerated aging test, and sets up an orthogonal test group to arbitrarily combine the magnitudes of different aging stresses. During the entire aging process, each stress factor is applied evenly, effectively improving the accuracy and flexibility of the aging test, and being able to solve the problem in the prior art that it is difficult to simultaneously apply thermal, electrical, and mechanical stresses to the XLPE cable insulation for an accelerated aging test.

[0035] See Figures 1-8 As shown, to achieve the above object, the present invention provides a multi-stress coupling accelerated aging device for XLPE cable insulation layer materials:

[0036] A multi-stress aging test device for cable insulation layers includes an adjustable high temperature provided by a thermal aging chamber as thermal aging stress; a variable-frequency series-resonant AC withstand voltage device composed of a power frequency AC power supply, a variable-frequency power supply, an excitation transformer, a resonant reactor, and a voltage divider provides an adjustable AC voltage as electrical aging stress; weights, a telescopic spring clamp provide a mechanical tensile force parallel to the surface of the specimen, an adjusting nut provides a mechanical pressure perpendicular to the surface of the specimen, and a three-dimensional variable-frequency vibration platform provides an overall mechanical vibration stress. These three types of mechanical forces together serve as the mechanical aging stress for XLPE insulation.

[0037] In terms of the overall structure, a thermal aging chamber is used as the main test equipment. A through groove is opened at the top of the thermal aging chamber, and an insulator is installed in the through groove to isolate the electrical connection between the casing of the thermal aging chamber and the external high-voltage input, ensuring the safety of the equipment. The AC high voltage generated by the frequency conversion series resonance AC device enters the interior of the thermal aging chamber through the high-voltage bushing and is distributed to each XLPE insulation aging cavity through the insulated high-voltage distribution box. Each XLPE insulation aging cavity is fixed in the square hole of the three-dimensional frequency conversion vibration platform, and a round groove is opened downward for placing the lower end hook weights. The high-voltage wires branched from the insulated high-voltage distribution box are respectively connected to the high-voltage terminal of the aging cavity, and the other end of the aging cavity is the ground wire terminal. The ground wire of the cavity also passes through the hole of the three-dimensional frequency conversion vibration platform and is led out from the lower end of the platform, and after converging, it is led out of the box through the grounding insulator on the casing from the interior of the thermal aging chamber. The whole set of equipment ensures that the thermal aging stress, electrical aging stress, and mechanical aging stress are mutually orthogonal and do not interfere with each other when applied, effectively meeting the requirements for applying aging stress.

[0038] In terms of thermal aging stress, a thermal aging chamber is used to provide a controllable high temperature and reserve sufficient space for placing mechanical stress components such as a three-dimensional frequency conversion vibration platform and hook weights inside. According to national standards: the operating temperature of XLPE cable insulation material is 90°C, and in case of overload or short-circuit fault, the maximum temperature can reach 250°C in a short time. Based on this regulation, the temperature setting range of the thermal aging chamber of the present invention is within the range of 90°C to 200°C. And according to the ventilation standard of the national standard, the air change rate in the oven is not less than 8 times per hour and not more than 20 times per hour.

[0039] In terms of electrical aging stress, a frequency conversion series resonance AC high-voltage generating device is adopted. The IGBT of the frequency conversion resonance power supply obtains a sine wave voltage output by changing the duty cycle of the output square wave through sine pulse width modulation (SPWM). The AC power supply is first rectified by a diode bridge rectifier circuit and then outputs an AC voltage with adjustable voltage and frequency through an inverter circuit; the excitation transformer is used to boost the output voltage of the frequency conversion resonance power supply to the required test voltage to meet the voltage requirements of the reactor and the specimen at the quality factor; the resonance reactor, the capacitance of the specimen itself, and the resistance in the circuit together form a series resonance circuit. When the series resonance condition is met, a test voltage several times higher than the power supply input voltage can be applied to the capacitor. Under this condition, by adjusting the output voltage value of the frequency conversion resonance power supply, it can be ensured that the voltage at both ends of the specimen is adjustable and meets the test requirements; the capacitance voltage divider is the test voltage sampling part of the equipment, and the sampling signal line led out from the low-voltage arm is used as the measurement and protection signal of the test voltage and is led back to the frequency conversion power supply to form a negative feedback system, see Figures 3-4 shown.

[0040] For subsequent aging degree inspection tests, due to different inspection mechanisms, the specimens used in the present invention are divided into two types: the national standard GB / T528 dumbbell-shaped specimens designed for mechanical property tests and square specimens designed for other physical and chemical property tests. Flat electrodes with d = 25 mm and spherical electrodes with d = 12.5 mm are designed for the electrical aging test according to the different surface characteristics of the two specimens. The entire electrical aging equipment is placed in a transformer oil medium (25#) for the test to prevent the generation of electric arcs.

[0041] See Figure 5 In terms of the mechanical stress shown, the present invention can provide three types of compressive stress, tensile stress and vibration stress. For compressive stress, the compressive stress is adjusted by adjusting the external distance adjusting nut of the XLPE insulation aging cavity. The FSR thin film pressure sensor attached near the grounding side motor on the internal specimen is used to measure the compressive pressure, and the measured compressive pressure value is transmitted to the pressure sensor transmitter inside the high-temperature chamber above the packaging cup cover through a transmission line. The Bluetooth module equipped inside the transmitter can transmit the pressure data to an external device. Thus, the control and monitoring of the compressive force are completed. Considering that the high temperature in the aging chamber will cause the electrodes to expand slightly and increase the degree of compressive force, a certain margin should be left below the specified value when setting the compressive force.

[0042] In terms of tensile stress, weights and a retractable spring clamp fixed at the bottom of the aging cavity are used for the operation. When setting the tensile stress, first fix the specimen between the fixed insulation clamp of the aging cavity and the retractable spring insulation clamp without hanging weights, and fix the cavity on the plane with holes of the three-dimensional vibration platform. Then hang weights from below the vibration platform to the cavity. According to the formula it can be known that the pressure of the specimen under tension should be the ratio of the gravity of the weights to the front area of the specimen. The front area of the dumbbell-shaped specimen is 1565.818 mm 2 , and the front area of the square specimen is 2500 mm 2 . If the mass of the weights is m, in grams, and the acceleration due to gravity is taken as 9.8 m / s 2 , then the tensile pressure of the specimen should follow:

[0043]

[0044] According to the above formula, the pressure of the tensile force on different specimens can be obtained from the mass of the hanging weights. By adjusting the number of hanging weights in each cavity, the tensile force pressure on the specimen can be adjusted. In terms of vibration stress, a three-dimensional variable-frequency vibration platform is adopted. There are holes on the upper part of the platform, which can fix the XLPE insulation aging cavity and facilitate the installation of the tensile hanging weights. The vibration platform has a total of six motors and rubber springs, and the vibration effects in the up-and-down, left-and-right, and front-and-back directions can be set to simulate the mechanical stress suffered by the cable insulation during transportation, loading and unloading, and laying. The three methods of extrusion stress, tensile stress, and vibration stress do not interfere with each other and can be orthogonal to each other.

[0045] Through the cooperation of the above-mentioned various modules of the device of the present invention, the mutual independence and orthogonality of the three stress application methods are realized, the difficulties in the multi-stress coupling aging test of XLPE cable insulation are solved, the insulation aging test can be effectively carried out, and basic materials are provided for subsequent insulation aging degree tests and the like.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A cable insulation layer multi-stress aging test device, comprising a variable frequency series resonant AC withstand voltage device and a thermal aging box, characterized by: The variable frequency series resonant AC withstand voltage device comprises an industrial frequency AC power supply, a variable frequency power supply, an excitation transformer, a resonant reactor and a capacitive voltage divider which are electrically connected in this way, and provides an adjustable AC voltage as an electrical aging stress; The thermal aging box includes: hooks and retractable spring clamps for providing mechanical tension parallel to the sample surface; adjustable nuts for providing mechanical pressure perpendicular to the sample surface; and a three-dimensional variable frequency vibration platform for overall mechanical vibration stress. These three types of mechanical forces together serve as mechanical aging stress for XLPE insulation.

2. The cable insulation layer multi-stress aging test device according to claim 1 is characterized in that: the thermal aging box further includes the following contents: the thermal aging box serves as the main test equipment, and a through groove is opened on the top thereof, and insulators are installed in the through groove to isolate the electrical connection between the thermal aging box casing and the external high voltage input.

3. The cable insulation layer multi-stress aging test device according to claim 1 is characterized by: The AC high voltage generated by the variable frequency series resonant AC withstand voltage device enters the interior of the thermal aging box through the high voltage bushing, and is distributed to each XLPE insulation aging cavity through the insulating high voltage junction box. Each XLPE insulation aging cavity is fixed in the square hole of the three-dimensional variable frequency vibration platform, and a circular groove is further opened downward for the placement of the lower end hook. The high voltage lines separated from the insulating high voltage junction box are respectively connected to the high voltage terminals of the aging cavity. The other end of the aging cavity is the ground terminal. The ground wire of the cavity is also led out from the lower end of the platform through the hole of the three-dimensional variable frequency vibration platform. After being gathered together, the ground wire is led out of the box from the thermal aging box cavity through the grounding insulator on the casing. The whole set of equipment ensures that the thermal aging stress, the electrical aging stress and the mechanical aging stress are mutually orthogonal and do not interfere with each other when applied, and can effectively meet the application requirements of the aging stress.

4. The cable insulation layer multi-stress aging test device according to claim 3 is characterized by: In terms of the thermal aging stress, a thermal aging box is used to provide controllable high temperature, and sufficient space is reserved for placing a three-dimensional variable frequency vibration platform and hook code mechanical stress components inside. The temperature setting range of the thermal aging box is within the range of 90°C to 200°C; the air in the oven is changed no less than 8 times and no more than 20 times per hour.

5. The cable insulation layer multi-stress aging test device according to claim 3 is characterized by: In terms of the electrical aging stress, a variable frequency series resonant AC high voltage generator is used to obtain a sinusoidal voltage output by changing the output square wave duty cycle through the IGBT of the variable frequency resonant power supply through sinusoidal pulse width modulation SPWM; the industrial frequency AC power supply is first rectified by a diode bridge rectifier circuit, and then outputs an AC voltage with adjustable voltage and frequency through an inverter circuit; the excitation transformer is used to boost the output voltage of the variable frequency resonant power supply to the required test voltage to meet the voltage requirements of the reactor and the test product under the quality factor; the resonant reactor, the test product's own capacitance and the resistance in the circuit together constitute a series resonant circuit. When the series resonance condition is met, a test voltage several times higher than the power supply input voltage is applied to the capacitor. Under this condition, the output voltage value of the variable frequency resonant power supply is adjusted to ensure that the voltage at both ends of the sample is adjustable and meets the test requirements; the capacitor voltage divider is the test voltage sampling part of the equipment, and the sampling signal line led out through the low voltage arm is used as the test voltage measurement and protection signal to lead back to the variable frequency power supply to form a negative feedback system.

6. A cable insulation layer multi-stress aging test method, the method is based on the cable insulation layer multi-stress aging test device according to claim 3, and is characterized by: Mechanical aging stress includes extrusion stress, tensile stress and vibration stress; Regarding the extrusion stress, the extrusion stress is adjusted by adjusting the external spacing nut of the XLPE insulation aging cavity. The FSR film pressure sensor attached to the internal sample near the grounding measuring motor is used to measure the extrusion pressure. The measured extrusion pressure value is transmitted to the pressure sensor transmitter inside the high-temperature resistant chamber above the packaging cup cover through the transmission line. The Bluetooth module inside the transmitter transmits the pressure data to the external device, thereby completing the control and monitoring of the extrusion pressure. For tensile stress, a hook weight and a retractable spring clamp fixed at the bottom of the aging chamber are used for operation. When setting the tensile stress, the sample is first fixed between the fixed insulating clamp of the aging chamber and the retractable spring insulating clamp without the hook weight, and the chamber is fixed on the plane with holes on the three-dimensional vibration platform. Then, the hook weight is hung from the bottom of the vibration platform to the cavity. According to the tensile pressure on the sample, it should be the ratio of the gravity of the hook weight to the front area of ​​the sample. If the mass of the hook weight is m, the unit is g, and the gravity acceleration is taken as 9.8m / s 2 , S 试样 For the area of ​​the selected specimen, the tensile force and pressure on the specimen should follow: According to the above formula, the tensile pressure of different samples can be obtained by the mass of the hook weight, and the tensile pressure of the sample can be adjusted by adjusting the number of hook weights in each cavity; In terms of vibration stress, a three-dimensional variable frequency vibration platform is used. There are holes on the upper part of the platform to fix the XLPE insulation aging cavity and facilitate the installation of tension hooks. The vibration platform has a total of six motors and rubber springs, and is set to have up and down, left and right, and front and back vibration effects to simulate the mechanical stress that the cable insulation is subjected to during transportation, loading and unloading, and laying.

7. Cross-linked polyethylene insulated transmission cable, characterized by: The cable is obtained by using the cable insulation layer multi-stress aging test device described in any one of claims 1-5.

8. Cross-linked polyethylene insulated transmission cable, characterized by: The cable is obtained by the cable insulation layer multi-stress aging test method described in claim 6.

9. Power system hub equipment, used in the field of power transmission, comprising the cross-linked polyethylene insulated transmission cable according to claim 8.

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