Aging experiment method for interface coating agent of direct-current cable accessory

Abstract

The invention discloses a direct-current cable accessory interface coating agent aging experiment method, which is characterized in that the direction of an applied electric field is consistent with the direction of an electric field in actual operation by designing the shape of a high-voltage electrode, each electrode is provided with different voltage levels, and a conveyor belt is placed below the electrode; the speed of the conveyor belt is controlled to realize corona aging of the interface coating agent under different voltages and different time, and the condition of the interface coating agent of the cable accessory in the actual operation process is simulated. The high-voltage electrode and the ground electrode are respectively designed into a single needle shape and a flat plate shape, the distance between the needle tip of the high-voltage electrode and the ground electrode is controlled to be 8 + / -0.1 mm, and the curvature radius of the needle tip of the needle electrode is 300 microns; an interface coating agent aging experiment sample is prepared, and the prepared sample is placed below the first needle electrode and on the conveyor belt; the three high-voltage needle electrodes and the ground electrode are connected to a high-voltage power source and a ground wire respectively, different voltage grades are set respectively, and the speed of the conveying belt is set.

Description

Technical Field

[0001] The invention belongs to the technical field of high voltage and insulation, and in particular relates to an aging test method for a DC cable accessory interface coating agent. Background Art

[0002] As an important part of the DC transmission system, the safety and reliability of the operation of power cable lines directly affect the entire transmission network. The high-voltage DC cable system includes DC cables and cable accessories. Due to the insulation structure of multiple layers of solid media and the complex installation of cable accessories, it has always been the weakest and most frequently faulty part of the cable line. Since the insulation of cable accessories and the main insulation of the cable have obvious physical interfaces and differences in electrical and mechanical properties, space charges are generated and accumulated at the interface, causing interface insulation breakdown. The interface coating agent generally uses dimethyl silicone oil. Applying it at the interface between cable accessories and cables can not only make the interface lubricated and easy to install, but also fill the damage during the installation process and improve the insulation performance of the interface. With the further improvement of the voltage level and transmission capacity of power cable transmission, the reliability of cable accessories has been greatly challenged.

[0003] The interface coating agent will also age during the operation of the cable accessories, and the insulation performance will decrease, thus causing interface breakdown. During the operation of the system, due to the influence of external factors such as high temperature, moisture, gas and impurities, the electrical performance of the coating agent at the interface of the cable accessories gradually deteriorates. As the operation time of the cable accessories increases, the aging degree of the coating agent gradually increases, causing the insulation performance at the interface of the cable accessories to be greatly reduced, and local discharge will be generated under the action of strong electric fields, which will then extend to the entire cable accessories, eventually causing insulation breakdown of the cable accessories, thus limiting the further development of the DC transmission system.

[0004] During the operation of the power system, the interface coating agent of DC cable accessories is affected by external factors such as high temperature, moisture, gas and impurities, and its electrical performance gradually deteriorates. With the increase of operating time and the gradual increase of the electric field, local discharge will occur at the interface, which will eventually cause insulation breakdown of the cable accessories and cause power transmission system failure. By designing the high-voltage electrode used for aging of the interface coating agent of DC cable accessories as a single needle electrode, the direction of the applied electric field can be consistent with the direction of the electric field in actual operation. Each electrode is set with a different voltage level, and a conveyor belt is placed underneath. By controlling the speed of the conveyor belt, the corona aging of the interface coating agent at different voltages and different times can be achieved, simulating the situation of the interface coating agent of cable accessories during actual operation. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an aging test method for a DC cable accessory interface coating agent.

[0006] The present invention provides an aging experimental method for an interface coating agent of a DC cable accessory. By designing the shape of a high-voltage electrode for corona aging and setting different voltage levels, the direction of an applied electric field can be made consistent with the direction of an electric field in actual operation. Different voltage levels are set for each electrode, and a conveyor belt is placed underneath. By controlling the speed of the conveyor belt, corona aging of the interface coating agent can be achieved at different voltages and at different times, thereby simulating the situation of the interface coating agent of a cable accessory during actual operation.

[0007] The technical solution of the present invention is a DC cable accessory interface coating agent aging test method, comprising the following steps:

[0008] The high-voltage electrode used for corona aging of the interface coating agent of cable accessories under DC is designed as a single needle electrode, so that the direction of the applied electric field is consistent with the direction of the electric field in actual operation;

[0009] A plurality of high-voltage electrodes are provided, and each high-voltage electrode is provided with a different voltage level;

[0010] A conveyor belt is placed under the high-voltage electrode, and an interface coating agent aging test sample is placed above the conveyor belt. By setting the conveyor belt speed, the interface coating agent is subjected to corona aging at different voltages and different times, simulating the interface coating agent of the cable accessories during actual operation.

[0011] A grounding electrode is provided under the conveyor belt.

[0012] Furthermore, the sample used for the interface of the DC cable accessories is selected from any one of cross-linked polyethylene, silicone rubber, and EPDM rubber.

[0013] Furthermore, the interface coating agent is selected from any one of dimethyl silicone oil, methylphenyl silicone oil, long-chain alkyl modified silicone oil, and fluorinated silicone grease.

[0014] Furthermore, three needle-shaped high-voltage electrodes are provided.

[0015] Furthermore, the power supply system provides: DC voltage with an amplitude within 0-70kV, repetitive pulse voltage, operating overvoltage, simulating the voltage conditions that the cable accessory interface is subjected to during operation.

[0016] Furthermore, the distance between the needle tip of the high voltage electrode and the ground electrode is controlled to be 8±0.1 mm, and the curvature radius of the needle tip of the high voltage electrode is 300 μm.

[0017] Furthermore, the conveyor belt speed is 0.015 mm / min, and the aging time of the sample at each voltage level is controlled to be 48 h.

[0018] Further, the coating agent preparation process is as follows:

[0019] (1) Pour an appropriate amount of the selected interface coating agent into a clean beaker, place it in a vacuum drying oven, and continuously evacuate the mixture to fully remove the air in the mixture;

[0020] (2) The treated coating agent is evenly applied to the sample used for the DC cable accessory interface to obtain the DC cable terminal interface coating agent aging test sample.

[0021] Connect the three high-voltage needle electrodes and the ground electrode to the high-voltage power supply and the ground wire respectively, and set different voltage levels. Since the interface coating agent is a viscous liquid with fluidity, the highest voltage level is less likely to exceed 30kV after practical operation. This experiment is set to 10kV-20kV-30kV.

[0022] Sample preparation:

[0023] (1) Take 5 g of pellets and put them into a mold, move them into a flat vulcanizer at 110 °C for pre-pressing for 2 min, then heat them to 180 °C and continue hot pressing at 20 MPa for 15 min;

[0024] (2) After heating, the pressure was maintained and the sample was naturally cooled to room temperature. The sample was placed in a vacuum oven for heat treatment at 80°C for 8 hours to remove cross-linked byproducts. A square sample with a thickness of 300 μm and a size of 40*40 mm was prepared.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The high-voltage electrode adopts a single-needle electrode, and the ground electrode adopts a flat plate shape. The material is the same as that of the high-voltage electrode. The shape of the high-voltage electrode is designed to ensure that the direction of the applied electric field is consistent with the direction of the electric field in actual operation.

[0027] 2. The sample contains 1 flat ground electrode and 3 single-needle high-voltage electrodes. The electrodes are set at different voltage levels and a conveyor belt is placed underneath. By controlling the conveyor belt speed, the interface coating agent can be corona aged at different voltages and different times, simulating the actual operation of the interface coating agent of the cable accessories.

[0028] 3. The field strength application method is authentic and reliable.

[0029] 4. The power supply system can provide DC voltage, repetitive pulse voltage, operating overvoltage, etc. with an amplitude within 0-70kV to simulate the voltage conditions that the cable accessory interface is subjected to during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the corona aging experimental platform of the present invention.

[0031] Figure 2 It is a schematic diagram of the interface breakdown test results. DETAILED DESCRIPTION

[0032] The following further illustrates how the DC cable accessory interface coating agent aging test method of the present invention is implemented in conjunction with the accompanying drawings and specific embodiments.

[0033] The purpose of the present invention is to provide an aging test method for the interface coating agent of a DC cable accessory, by designing the shape of the high-voltage electrode to achieve the consistency between the direction of the applied electric field and the direction of the electric field in actual operation, setting different voltage levels for the electrode, and placing a conveyor belt underneath, so as to achieve corona aging of the interface coating agent at different voltages and different times, and simulate the situation of the interface coating agent of the cable accessory in the actual operation process. The specific implementation steps are as follows:

[0034] 1. The high-voltage electrode and the ground electrode are designed to be single-needle and flat-plate shaped, respectively. A flat-plate ground electrode, three single-needle high-voltage electrodes and a conveyor belt are pre-placed in the designed test platform. The distance between the high-voltage electrode tip and the ground electrode is controlled to be 8±0.1mm, and the curvature radius of the needle electrode tip is 300μm.

[0035] 2. Prepare the interface coating agent aging test sample, place the prepared sample under the first needle electrode and on the conveyor belt, set the voltage level of each electrode and the conveyor belt speed, such as Figure 1 The DC cable accessory interface coating agent aging experiment shown in the figure has the following preparation process:

[0036] Cross-linked polyethylene specimen:

[0037] (1) Take 5 g of pellets and put them into a mold, move them into a flat vulcanizer at 110 °C for pre-pressing for 2 min, then heat them to 180 °C and continue hot pressing at 20 MPa for 15 min;

[0038] (2) After heating, the pressure was maintained and the sample was naturally cooled to room temperature. The sample was placed in a vacuum oven and heat treated at 80°C for 8 h to remove cross-linked byproducts to produce a square sample with a thickness of 300 μm and a size of 40*40 mm.

[0039] Coating agent:

[0040] (1) Pour an appropriate amount of the selected interface coating agent into a clean beaker, place it in a vacuum drying oven, and continuously evacuate for 10 minutes to fully remove the air in the mixture;

[0041] (2) The treated coating agent is evenly applied to the cross-linked polyethylene to obtain a DC cable terminal interface coating agent aging test sample.

[0042] 3. Connect the high voltage electrode and ground electrode to the high voltage power supply and ground wire respectively. Since the interface coating agent is a viscous liquid with fluidity, the highest voltage level should not exceed 30kV after practical operation. This experiment is set to 10kV-20kV-30kV.

[0043] 4. Set the conveyor belt speed to 0.015mm / min. At this time, the aging time of the sample at each voltage level is about 48h. Set the conveyor belt speed according to the required aging time.

[0044] Taking this as an example, the interface breakdown test was performed after corona aging for 24h and 48h at 20kV DC voltage. The test results are shown in Table 1:

[0045] Table 1

[0046] Interface breakdown test conditions 0h 24h 48h Room temperature, 0.05MPa -36.38kV -25.05kV -20.8kV 90℃,0.05MPa -20.283kV -13.6kV -11.87kV Room temperature, 0.3MPa -46.48kV -37.1kV -32.2kV 90℃,0.3MPa -35.43kV -19.13kV -15.67kV

[0047] The schematic diagram of the interface breakdown test results is shown in the figure. Figure 2 shown.

Claims

1. A DC cable accessory interface coating agent aging test method, characterized in that: The shape of the high-voltage electrode is designed to ensure that the direction of the applied electric field is consistent with the direction of the electric field in actual operation. Different voltage levels are set for each electrode, and a conveyor belt is placed underneath to control the speed of the conveyor belt to achieve corona aging of the interface coating agent at different voltages and different times, simulating the actual operation of the interface coating agent of the cable accessories. The specific steps include: The high-voltage electrode used for corona aging of the interface coating agent of cable accessories under DC is designed as a single needle electrode, so that the direction of the applied electric field is consistent with the direction of the electric field in actual operation; A plurality of high-voltage electrodes are provided, and each high-voltage electrode is provided with a different voltage level; A conveyor belt is placed under the high-voltage electrode, and an interface coating agent aging test sample is placed above the conveyor belt. By setting the conveyor belt speed, the interface coating agent is subjected to corona aging at different voltages and different times, simulating the actual operation of the interface coating agent of the cable accessories. A grounding electrode is provided under the conveyor belt.

2. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The sample used for the interface of DC cable accessories can be any one of cross-linked polyethylene, silicone rubber, and EPDM rubber.

3. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The interface coating agent is selected from any one of dimethyl silicone oil, methylphenyl silicone oil, long-chain alkyl modified silicone oil, and fluorinated silicone grease.

4. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: Three needle-shaped high-voltage electrodes are provided.

5. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The power supply system provides: DC voltage with an amplitude of 0-70kV, repetitive pulse voltage, operating overvoltage, and simulates the voltage conditions that the cable accessory interface is subjected to during operation.

6. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The distance between the needle tip of the high voltage electrode and the ground electrode is controlled to be 8±0.1 mm, and the curvature radius of the needle tip of the high voltage electrode is 300 μm.

7. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The conveyor belt speed is 0.015 mm / min, and the aging time of the sample at each voltage level is controlled to be 48 h.

8. A DC cable accessory interface coating agent aging test method according to claim 1, characterized in that: The coating preparation process is as follows: (1) Pour an appropriate amount of the selected interface coating agent into a clean beaker, place it in a vacuum drying oven, and continuously evacuate the mixture to fully remove the air in the mixture; (2) The treated coating agent is evenly applied to the sample used for the DC cable accessory interface to obtain the DC cable terminal interface coating agent aging test sample.

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