阅读说明：本技术 一种高压电缆用半导电屏蔽料 (Semiconductive shielding material for high-voltage cable ) 是由 李文鹏 张翀 李维康 闫轰达 陈新 田书然 林德源 于 2019-03-01 设计创作，主要内容包括：本发明提出了一种高压电缆用半导电屏蔽料,所述半导电屏蔽料按照质量分数计包括：非极性基料60-80％、炭黑10-40％、交联剂1.5-2％和抗氧化剂0.1-0.5％,本发明有效抑制了高压直流电缆中空间电荷的聚集,同时大大提高了电缆长期运行的可靠性和稳定性,可广泛应用于高压电缆系统。(The invention provides a semiconductive shielding material for a high-voltage cable, which comprises the following components in percentage by mass: 60-80% of non-polar base material, 10-40% of carbon black, 1.5-2% of cross-linking agent and 0.1-0.5% of antioxidant, the invention effectively inhibits the aggregation of space charge in the high-voltage direct-current cable, greatly improves the reliability and stability of the cable in long-term operation, and can be widely applied to high-voltage cable systems.)

1. A semiconductive shielding material for a high-voltage cable is characterized by comprising the following components in percentage by mass: 60-80% of non-polar base material, 10-40% of carbon black, 1.5-2% of cross-linking agent and 0.1-0.5% of antioxidant.

2. The semiconducting shield of claim 1, wherein the semiconducting shield comprises: 65-75% of non-polar base material, 10-35% of carbon black, 1.8-2% of cross-linking agent and 0.1-0.2% of antioxidant.

3. The semiconductive shield material of claim 1, wherein the non-polar binder is low density polyethylene or a mixture of low density polyethylene and ultra-low density polyethylene having a mass fraction of 10% or more, a melt flow rate of 0.15-0.25g/min, and a density of 900-910g/m³。

4. The semiconductive shield material of claim 1, wherein the carbon black has a particle size of 20 to 40nm and a specific surface area of 50 to 65m²Per g, ash and sulfide content less than or equal to 100 ppm.

5. The semiconductive shield material of claim 1, wherein the crosslinking agent is a peroxide-based compound and the antioxidant is a thiobis-phenolic compound.

6. The semiconducting shield of claim 5, wherein the crosslinking agent is dicumyl peroxide and the antioxidant is a bis-sulfide.

7. The semiconducting shield of claim 1, wherein the semiconducting shield is prepared by the steps of:

(1) heating the base material and the antioxidant to 140 ℃ for melting and mixing;

(2) adding carbon black into the product obtained in the step (1) and uniformly stirring;

(3) cooling the product obtained in the step (2) to 115 ℃, adding a cross-linking agent, and uniformly stirring;

(4) and cooling to room temperature to obtain the semiconductive shielding material.

Technical Field

The invention relates to a material of a semiconductive shielding material, in particular to a semiconductive shielding material for a high-voltage cable.

Background

The polyethylene insulated cable has the advantages of small volume, light weight, high working temperature, low maintenance cost and environmental protection, and has more advantages compared with other insulated material cables in the aspects of production, transportation, installation, recovery and the like. The existing polyethylene cable can only be used for transmitting direct current electric energy in a low-voltage distribution system, but cannot be directly applied to a high-voltage direct current system, and the main reason is that a large amount of space charges can be accumulated in a high-voltage direct current electric field by the polyethylene insulated cable, so that the electric field distribution in the insulated system is seriously distorted, and if the local electric field strength is far higher than the running strength of the cable, the accelerated aging of the cable material can be caused, and even the cable material can be directly punctured in a serious electric field distortion area. Ionization and polarization of additives and crosslinking byproducts under a direct current electric field can cause a space charge phenomenon in a polyethylene insulated cable, and accumulation of the space charge can seriously threaten long-term operation and the final service life of the high-voltage direct current cable, so that the accumulation of the space charge in the high-voltage direct current cable needs to be inhibited.

6,924,435B 2, and CN 101585943 and CN 105131419, respectively, additives, space charge inhibitors or other nano-doping methods are used to improve the space charge phenomenon in the semiconductive shielding material. However, the addition of the additive into the semiconductive shielding material is complex in production and high in cost, and a new polar molecule source may be introduced into the semiconductive shielding layer and further diffused to the cable insulating layer to form charge accumulation, so that the safe and stable operation of the high-voltage direct-current cable is threatened.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a semiconductive shielding material for inhibiting space charge accumulation in a high-voltage direct-current cable, which is realized by adopting the following technical scheme:

a semiconductive shielding material for a high-voltage cable, comprising the following components in percentage by mass: 60-80% of non-polar base material, 10-40% of carbon black, 1.5-2% of cross-linking agent and 0.1-0.5% of antioxidant.

Further, the semiconductive shield includes: 65-75% of non-polar base material, 10-35% of carbon black, 1.8-2% of cross-linking agent and 0.1-0.2% of antioxidant.

Further, the non-polar base material is low-density polyethylene or a mixture of low-density polyethylene with the mass fraction being more than or equal to 10% and ultra-low-density polyethylene, the melt flow rate of the non-polar base material is 0.15-0.25g/min, and the density of the non-polar base material is 900-910g/m³。

Further, the carbon black has a particle size of 20-40nm and a specific surface area of 50-65m²Per g, ash and sulfide content less than or equal to 100 ppm.

Further, the cross-linking agent is a peroxide compound, and the antioxidant is a thiobisphenol compound.

Further, the crosslinking agent is dicumyl peroxide, and the antioxidant is dithioether.

Further, the preparation steps of the semiconductive shielding material are as follows:

(1) heating the base material and the antioxidant to 140 ℃ for melting and mixing;

(2) adding carbon black into the product obtained in the step (1) and uniformly stirring;

(3) cooling the product obtained in the step (2) to 115 ℃, adding a cross-linking agent, and uniformly stirring;

(4) and cooling to room temperature to obtain the semiconductive shielding material.

Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:

(1) the semiconductive shielding material for inhibiting the space charge aggregation in the high-voltage direct-current cable modifies the traditional insulating material by introducing the material without impurities and polar molecules, is matched with the main insulating material of the cable, and has the charge density fluctuation of 60C/m along with the increase of the thickness of the electric shielding material³The range is more uniform, and the generation and the migration of space charges under a direct current electric field are effectively inhibited.

(2) The semi-conductive shielding material provided by the invention has low electric field enhancement amount, effectively inhibits the influence of space charge on electric field distribution, and has the electric field enhancement amount lower than 3% after the ultra-low density polyethylene is mixed.

(3) The insulating layer and the semi-conductive shielding layer of the cable in the semi-conductive shielding material provided by the invention both adopt the same ultra-clean polyethylene material, the main thermal properties of the semi-conductive shielding material are close to each other, the good thermal bonding property of the semi-conductive shielding layer and the insulating layer is effectively ensured, the impurity content is low, the concentration is similar, and the impurities are limited from diffusing from the semi-conductive shielding layer to enter the insulating layer.

(4) The ultra-clean conductive carbon black is selected as the semi-conductive shielding material, so that the amount of impurities and foreign group elements in the semi-conductive shielding material is lower, the impurities are prevented from diffusing into an insulation system, and the risk of space charge accumulation is greatly reduced.

Drawings

FIG. 1: at room temperature, the space charge distribution result of the embodiment provided by the invention in an electric field with the strength of 40kV/mm for 1 hour;

FIG. 2: at room temperature, the electric field distribution result of the embodiment provided by the invention in an electric field with the strength of 40kV/mm for 1 hour;

FIG. 3: the result of the transient residual space charge distribution after removing the applied voltage.

Detailed Description

The technical solutions provided by the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the present invention, and not all of it.

The test method comprises the following steps:

respectively melting and pre-pressing the insulating material and the semi-conductive shielding material into a film sample by a hot vulcanizing machine at 120 ℃, cooling, tightly clamping the insulating film between two layers of semi-conductive shielding layer films, simulating an insulating system structure in an actual high-voltage cable, putting the sample into the hot vulcanizing machine, heating until the sample is melted, and quickly heating to 180-200 ℃ for cross-linking reaction. Because the three layers of materials are melted and crosslinked simultaneously, the semiconductive shielding layer and the insulating layer are completely thermally bonded together, and no bubbles, splitting or other defects occur.

The space charge characteristics of the samples were measured and evaluated using the electro-acoustic pulse method (PEA). The measurement system, the measurement principle and the measurement procedure of the method can be seen in IEC standard IEC 62758:2012 calibration of space charge measurement devices based on the pulsed electro-acoustic (PEA) measurement principle. The measurement conditions were that a high voltage DC electric field of 40kV/mm was applied at room temperature (22 ℃ C.), and the space charge distribution was measured after the electric field was continuously applied for 1 hour. The rate of increase of the local electric field due to space charge accumulation in the insulation system is described by the field enhancement Factor (FE), which can be calculated by the following equation:

where Emax is the maximum value of the electric field strength in the insulation system; ea is the average electric field strength (40kV/mm) applied to the sample. Based on the requirement of safe and stable operation of the high-voltage direct-current cable, the smaller the FE is, the more uniform the electric field distribution in the cable insulation is, and the smaller the influence of space charge is.