A grounding grid plays the role of discharging current and balancing voltage to ensure the safety of the power system. However, soil corrosion can damage the grounding grid, which then can endanger the safe operation of power system. This paper reviewed recent research advances of soil corrosion of grounding grid. The cause, mechanism, types, and influencing factors of soil corrosion of grounding grids were summarized, and the corresponding detection technology and protective measures were also introduced. The paper pointed out that soil corrosion is a serious threat to the grounding grid system. Moreover, the impact mechanism of AC stray current, new corrosion detection technology, and better protective measures still need in-depth research.

Research Advances of Soil Corrosion of Grounding Grids.

Purpose – The purpose of the paper was to design an anti-corrosion system that combined conductive coatings with cathodic protection for a 500-kV substation ground grid, and provide a basis for the anti-corrosion construction of the installation. Design/methodology/approach – The study took the Shaoguan 500-kV substation grounding grid as the research object. The anti-corrosion performance of KV conductive coatings on grounding metal was researched. In parallel, the alkalinity of substation soil was evaluated according to the German DIN50929 Standard, and the combined protection system comprising conductive coatings and impressed current cathodic protection was designed. Findings – KV conductive coatings, that have resistance to acids, alkalis and salts, can effectively slow down the corrosion rate of the grounding grid. The investigation also provided the outline design, installation, construction requirements and monitoring methods for the 500-kV substation grounding grid. Originality/value – This repor...

The protection of 500kV substation grounding grids with combined conductive coating and cathodic protection

Epoxy based conductive anti-corrosion coatings were prepared on the surface of grounding grid Q235 carbon steel with graphite, carbon fiber andaluminum tripolyphosphateas pigments. The influence of the pigment/binder ratio (PBR) on the properties of the coatings was investigated such as the morphology and the electric conductivity of the coatings as well the corrosion behavior of Q235 carbon steel coated by coatings with an optimal PBR by immersion in salt solutions and burying in a selected soil from Shenyang test site. The results indicated that after buried in the soil, the bare Q235 steel suffered from serious corrosion and bubbles occurred on the E44 lacquer coating on the steel, in the contrast, the coatings with the optimal PBR showed excellent protectiveness for the steel even after buried for up to 1000 h in the soil. The volume resistivity and surface contact resistivity of the coatings are 0.65 Ω·cm and 8.72 Ω/cm respectively. The coatings exhibited excellent with standing capacity to high current impulse, such as their electrical resistance decreased by 5.95% and 11.09% for the ones suffered from a high current impulse of 1 kA for 20 times and a power frequency current of 10 A for 5 times respectively, while the surface of the coatings maintained unchanged without any destruction. 定稿日期:2015-03-26 作者简介:刘世念,男,1972年生,高级工程师 通讯作者:王成,E-mail:wangcheng@imr.ac.cn,研究方向为金属腐蚀与防护 DOI:10.11902/1005.4537.2014.273

Epoxy Based Conductive Anti-corrosion Coatings for Grounding Grid

For the online detection of the corrosion of ground grids, the relationship between the corrosion rate of Q235 steel and electric resistance was studied by the method of accelerated corrosion in the soil taken from the site of construction of a 750 kV high-voltage transformer station. The corrosion products and morphology are characterized by the SEM (scanning electron microscopy) and XRD (X-ray diffraction) methods. The results show that the rusty layer obtained by the accelerated corrosion has the same structure as the layer obtained by the natural corrosion and the corrosion products mainly consist of γ - Fe2O3 and FeO4. The one-year monitoring was realized and the relationship between the corrosion rate (V ) and resistivity ( R) was established. The deviation of the natural corrosion rate from the computed corrosion rate does not exceed 3%.

Feng Lajund

Papers

Study of the soil corrosion of Q235 steel ground grid in Weinan Shaanxi