The degree of influence of AC interference depends on the duration of the interference process, which can be distinguished into instantaneous interference and long-term continuous interference. Transient disturbance is caused by the failure of a high-voltage alternating current and the occurrence of very high interference currents. The duration of the fault current is usually 05s, capable of causing interference voltages of several thousand volts. Long-term interference has a persistent effect, but the voltage involved is lower than that of transient interference. The operating current in a high-voltage alternating current can cause such an interference, but in a ground-compensated high-voltage grid, such an interference can also occur during the effective time if a fault occurs. The interference voltage can reach tens of volts in the case of long-term continuous interference.
Metal corrosion in the electrolyte is essentially the result of the action of electrochemical galvanic cells. The corrosion electrochemistry developed on this basis mainly describes the role, process, influencing factors and mechanism of galvanic cells under the action of direct current. There are few studies on the influence of alternating current on DC galvanic batteries, and there are few studies on the corrosion mechanism under the action of alternating current alone. So far, the research results of alternating current corrosion show that alternating current accelerates the dissolution process of metal anodes, and the metal corrosion damage caused by alternating current is much lighter than that caused by direct current, and the intensity decreases with the increase of AC frequency.
The pipeline itself has an anti-corrosion insulation layer, so that the pipeline has a capacitance both on the ground during construction and after it is buried in the ground, which is connected between the phase conductor and the pipeline of the transmission system and between the pipeline and the adjacent ground.
This effect occurs mainly during pipeline construction, when the pipe rack is placed on a well-insulated pad block with good soil insulation and if the pipe is parallel to the strong current line, capacitive coupling voltages may be generated. If the welded pipe section is buried or placed on the ground and in the pipe trench, this capacitance effect is negligible.
Due to the current flow on the grounding body, the rise of the earth potential, when the pipeline passes through this range, the pipeline itself is equivalent to the distant zero potential, so that the voltage difference between the pipeline and the adjacent ground potential is generated on the pipeline, and the closest to the grounding body is the highest.