550 kV HGIS接地线电流分布特性及其对地网的电腐蚀研究

Current Distribution Characteristics of the Earth Wires on 550 kV HGIS Enclosure and the Current-induced Electric Corrosion to Grounding System

土壤中的碳钢接地材料在电流的作用下会发生腐蚀,从而改变地网的状态,影响主设备的安全运行。为了研究超高压组合电器(hybrid gas insulated substation,HGIS)外壳接地线电流的分布特性,分析其对接地体的腐蚀影响,文中建立了管母线外壳接地线电流分布数学模型,通过对接地线电流的大量实测和统计分析,验证了模型的有效性和正确性。最后,结合试验研究了不同电流密度对碳钢材料的腐蚀作用,提出了电流密度与腐蚀速率关系函数。研究表明:外壳接地线电流大小呈振荡波形分布,并无统一的分布规律。每串单相首末端接地线上电流大小与本相负荷电流的大小呈正相关关系,其它位置接地线上电流大小与该间隔负荷电流的大小关系不明显。负荷电流与该间隔外壳地线电流具有一比例系数k,该值大部分在10~30,再根据负荷电流大小可估算出碳钢接地网腐蚀速率的范围。电流密度越大,腐蚀越强烈,随着电流密度的增大,腐蚀速率趋于饱和。

Corrosion of carbon steel in soft would occur under the action of ahernate current, which changes the condition of grounding system and harms safe operation of the electrical appliances. To reveal the current distribution characteristics of earth wires on extra-high voltage HGIS （hybrid gas insulated substation） enclosure and analyze the current effect on corrosion of the grounding body, a current distribution model of the earth wire is built in this paper. And the effectiveness and correctness of the model are verified by a large number of test data and statistical analysis. Ultimately, the effects of different current density on the carbon steel corrosion are obtained through tests, and the relationship between the current density and corrosion rate is fitted. This research demonstrates that： （1）The distribution shape of the current in the earth wire is similar to the oscillation waveform without unique distribution law; （2）There exists positive correlation between the current in first earth wire and last earth wire and the load current at the same phase, while the distribution law of the currents in the earth wires at other places is not obvious; （3）There is a proportional factor k between load current and earth wire current with the value in the range of 10 to 30 for most cases, and the corrosion rate range of carbon steel grounding system can be calculated with k and load current; （4）The larger the current density is, the heavier the carbon steel corrodes, and the corrosion rate is close to saturation with current density increasing.