Aging test method for direct current cable accessory interface coating

Abstract

The application discloses a kind of direct current cable accessory interface coating agent aging experiment method, by designing high voltage electrode shape to realize the direction of electric field applied and the direction of electric field in actual operation consistent, different voltage levels are set to each electrode, and transmission belt is placed below, control transmission belt speed realizes interface coating agent corona aging under different voltage and different time, simulates the situation of cable accessory interface coating agent in actual operation process.High voltage electrode and ground electrode are designed into single needle shape and flat plate shape respectively, wherein the distance between high voltage electrode needle tip and ground electrode is controlled to 8±0.1mm, and the needle tip curvature radius of needle electrode is 300 μm;Preparation interface coating agent aging experiment sample, place the prepared sample under the first needle electrode on the transmission belt;Three high voltage needle electrodes and ground electrodes are connected to high voltage power supply and ground wire respectively, and different voltage levels are set respectively, and transmission belt speed is set.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high voltage and insulation technology, and particularly relates to a DC cable accessory interface coating agent aging experiment method. BACKGROUND

[0002] As an important part of the DC transmission system, the safety and reliability of the power cable line directly affect the entire transmission network. The HVDC cable system includes DC cables and cable accessories. Due to the multi-layer solid dielectric insulation structure inside the cable accessories and the complex installation, the cable accessories are the weakest and most frequent failure part in the cable line. Due to the obvious physical interface between the cable accessory insulation and the cable main insulation and the differences in electrical and mechanical properties, the space charge is generated and accumulated at the interface, causing the interface insulation breakdown. The interface coating agent generally uses dimethyl silicone oil, which is coated at the interface between the cable accessory and the cable, not only lubricating the interface for easy installation, but also filling the damage during installation and improving the insulation performance of the interface. With the further improvement of the voltage level and transmission capacity of the power cable, the reliability of the cable accessories is a huge challenge.

[0003] The interface coating agent will also age during the operation of the cable accessories, and the insulation performance will decrease, thereby causing the interface breakdown. During the system operation, due to the influence of high temperature, moisture, gas and impurities and other external factors, the electrical properties of the coating agent at the interface of the cable accessories gradually deteriorate, and the aging degree of the coating agent gradually increases with the increase of the operation time of the cable accessories, which greatly reduces the insulation performance at the interface of the cable accessories, generates partial discharge under the action of strong electric field, and then extends to the entire cable accessories, and finally causes the insulation breakdown of the cable accessories, thereby limiting the further development of the DC transmission system.

[0004] The interface coating agent of the DC cable accessory is affected by high temperature, moisture, gas and impurities and other external factors during the operation of the power system, and its electrical properties gradually deteriorate. With the increase of the operation time and the gradual increase of the electric field, partial discharge will occur at the interface, and finally cause the insulation breakdown of the cable accessories, causing the failure of the transmission system. By designing the high-voltage electrode for the aging of the DC cable accessory interface coating agent as a single needle electrode, the direction of the applied electric field can be consistent with the direction of the electric field in the actual operation. Different voltage levels are set for each electrode, and a conveyor belt is placed below. By controlling the speed of the conveyor belt, the corona aging of the interface coating agent under different voltages and different times can be realized, simulating the situation of the interface coating agent of the cable accessory in the actual operation process. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a DC cable accessory interface coating agent aging experiment method.

[0006] The application provides a DC cable accessory interface coating agent aging experiment method, by designing a high-voltage electrode shape of corona aging and setting different voltage levels, 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 below, and the speed of the conveyor belt can realize corona aging of the interface coating agent under different voltages and different times, simulating the situation of the cable accessory interface coating agent in the actual operation process.

[0007] The technical scheme of the application is a DC cable accessory interface coating agent aging experiment method, comprising the following steps:

[0008] The high-voltage electrode for corona aging of the cable accessory interface coating agent under DC is designed as a single needle-shaped 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 arranged, and different voltage levels are set for each high-voltage electrode;

[0010] A conveyor belt is placed below the high-voltage electrode, and an interface coating agent aging experiment sample is placed above the conveyor belt, and the speed of the conveyor belt is set to realize corona aging of the interface coating agent under different voltages and different times, simulating the situation of the cable accessory interface coating agent in the actual operation process;

[0011] A grounding electrode is arranged below the conveyor belt.

[0012] Further, any one of cross-linked polyethylene, silicone rubber and ethylene-propylene-diene rubber is selected as the sample for the DC cable accessory interface.

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

[0014] Further, three needle-shaped high-voltage electrodes are arranged.

[0015] Further, the power supply system comprises: a DC voltage with an amplitude of 0-70kV, a repetitive pulse voltage and an operating overvoltage, simulating the voltage working condition borne by the cable accessory interface during operation.

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

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

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

[0019] (1) Take the appropriate amount of selected interface coating agent into a clean beaker, put it into a vacuum drying oven, continuously vacuumize, and remove the air in the mixture body sufficiently;

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

[0021] Three high-voltage needle electrodes and a ground electrode are connected to a high-voltage power supply and a ground wire respectively, and different voltage levels are set. Since the interface coating agent is a viscous liquid with fluidity, the highest voltage level is not easy to exceed 30kV through practical operation, and the experiment is set to 10kV-20kV-30kV.

[0022] Sample preparation:

[0023] (1) 5g of particles are placed in a mold, moved into a flat curing machine with a temperature of 110℃ for 2min, then heated to 180℃, and hot-pressed at a pressure of 20MPa for 15min.

[0024] (2) After heating, the pressure is maintained and the sample is naturally cooled to room temperature, then the sample is placed in a vacuum oven for 8h at 80℃ for heat treatment to remove crosslinking by-products. The square sample with a thickness of 300μm and a size of 40*40mm is prepared.

[0025] Compared with the prior art, the beneficial effects brought by the present application are:

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

[0027] 2. The sample contains one flat plate ground electrode and three single needle high-voltage electrodes, the electrodes are set at different voltage levels, and a conveyor belt is placed below, and by controlling the speed of the conveyor belt, the interface coating agent can be subjected to corona aging under different voltages and different times, simulating the actual running process of the cable accessory interface coating agent.

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

[0029] 4. The power supply system can provide DC voltage, repetitive pulse voltage, operating overvoltage, etc. within the range of 0-70kV, simulating the voltage working condition of the cable accessory interface in operation. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of the corona aging test platform of the present application.

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

[0032] The DC cable accessory interface coating agent aging test method of the present application is further illustrated below in combination with the drawings and specific examples.

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

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

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

[0036] Crosslinked polyethylene sample:

[0037] (1) Take 5g of particles into the mold, move into the flat plate vulcanizing machine with a temperature of 110℃ for pre-pressing for 2min, then heat to 180℃, and continue hot pressing at a pressure of 20MPa for 15min;

[0038] (2) After heating, keep the pressure and naturally cool to room temperature, then take out the sample, place the sample in a vacuum oven for 8h of heat treatment at 80℃ to remove the crosslinking by-products, to make a square sample with a thickness of 300μm and a size of 40*40mm;

[0039] Coating agent:

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

[0041] (2) Uniformly apply the treated coating agent to the crosslinked polyethylene to obtain the DC cable terminal interface coating agent aging test sample.

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

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

[0044] For example, under a 20 kV direct current voltage, the interface breakdown test is carried out after corona aging for 24 h and 48 h respectively, and the test results are as shown in Table 1:

[0045] Table 1

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

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

Claims

1. A method for aging test of a direct current cable accessory interface coating agent, characterized by, By designing the shape of the high-voltage electrode to achieve the consistency of the applied electric field direction with the actual operation electric field direction, each electrode is provided with different voltage levels, and a conveyor belt is placed below, and the speed of the conveyor belt is controlled to realize the corona aging of the interface coating agent under different voltages and different times, simulating the situation of the cable accessory interface coating agent in the actual operation process; Specifically includes the following steps: The high-voltage electrode for corona aging of the interface coating agent of the DC cable accessory is designed as a single needle-shaped electrode, so as to achieve the consistency of the applied electric field direction with the actual operation electric field direction; A plurality of high-voltage electrodes are provided, and each high-voltage electrode is provided with different voltage levels; A conveyor belt is placed below the high-voltage electrode, and the interface coating agent aging test sample is placed above the conveyor belt, and the speed of the conveyor belt is set to realize the corona aging of the interface coating agent under different voltages and different times, simulating the situation of the cable accessory interface coating agent in the actual operation process; A grounding electrode is arranged below the conveyor belt, and the grounding electrode is in the form of a flat plate; The test sample for the interface of the DC cable accessory is selected from any one of cross-linked polyethylene, silicone rubber and ethylene-propylene-diene rubber; 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; The preparation process of the coating agent is as follows: (1) A proper amount of selected interface coating agent is poured into a clean beaker, and a vacuum drying box is used to continuously extract vacuum and fully remove air in the mixture; (2) The treated coating agent is evenly applied to the test sample for the interface of the DC cable accessory, to obtain the interface coating agent aging test sample of the DC cable accessory.

2. The method of claim 1, wherein the DC cable accessory interface coating is aged by, Three needle-shaped high-voltage electrodes are provided.

3. The method of claim 1, wherein the DC cable accessory interface coating is aged by, The power supply system provides DC voltage with an amplitude of 0-70kV, repetitive pulse voltage and operating overvoltage, simulating the voltage conditions that the cable accessory interface bears during operation.

4. The method of claim 1, wherein the DC cable accessory interface coating is aged by, The distance between the needle tip of the high-voltage electrode and the grounding electrode is controlled to be 8±0.1mm, and the needle tip curvature radius of the high-voltage electrode is 300μm.

5. The method of claim 1, wherein the DC cable accessory interface coating is aged by, The speed of the conveyor belt is 0.015mm / min, and the aging time of the test sample under each voltage level is controlled to be 48h.

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