Electric Field Distribution of Soluble Salt Deposition on the Surface of Insulators in Railway Overhead Lines

Different constituents of soluble salts have different effects on the insulation performance of insulators.To study the electric field distribution of soluble salt deposition on the surface of high-speed railway insulators,a two-dimensional model of the cantilever insulator electrostatic field and constant-current field with soluble salt deposition is constructed.The simulation results indicate that the relative dielectric constant of dry pollution is the main factor that affects the electric field distribution on the surface of the insulator.The electric field intensity is arranged in the following order:CaSO_(4)>KNO_(3)>NaNO_(3)>K_(2)SO_(4)>NaCl>MgSO_(4),and the conductivity of each dirty liquid in the wet state becomes a key factor affecting the electric field distribution,which is specifically shown as sodium chloride>nitrate>sulfate.The simulation results are compared with existing test results to verify that they were correct.It is also found that the electric field intensity of the insulator with good hydrophobicity is slightly greater than that of the insulator without hydrophobicity.The results provide a theoretical basis for the classification of regional pollution levels and the testing of insulator contamination in the laboratory.

Remediation of saline–sodic soil with flue gas desulfurization gypsum in a reclaimed tidal flat of southeast China

Salinization and sodicity are obstacles for vegetation reconstruction of coastal tidal flat soils. A study was conducted with flue gas desulfurization（FGD）-gypsum applied at rates of 0, 15, 30, 45 and 60 Mg/ha to remediate tidal flat soils of the Yangtze River estuary.Exchangeable sodium percentage（ESP）, exchangeable sodium（ExNa）, p H, soluble salt concentration, and composition of soluble salts were measured in 10 cm increments from the surface to 30 cm depth after 6 and 18 months. The results indicated that the effect of FGD-gypsum is greatest in the 0–10 cm mixing soil layer and 60 Mg/ha was the optimal rate that can reduce the ESP to below 6% and decrease soil p H to neutral（7.0）. The improvement effect was reached after 6 months, and remained after 18 months. The composition of soluble salts was transformed from sodic salt ions mainly containing Na~＋, HCO_3^-＋ CO_3^（2-）and Cl-to neutral salt ions mainly containing Ca^（2＋）and SO_4^（2-）. Non-halophyte plants were survived at 90%. The study demonstrates that the use of FGD-gypsum for remediating tidal flat soils is promising.