AC transmission lines or electrical trains and pipelines running parallel or crossing at non-90-degree angles will inevitably cause AC stray current interference to nearby buried pipelines. Due to AC interference, the affected object may generate high interference potentials, which can harm personnel working in contact with the affected object and damage equipment electrically connected to it. Moreover, when AC and DC stray currents act together, the AC component can cause depolarization on the electrode surface, accelerate insulation aging, promote coating detachment, and lead to perforation. Sometimes, it can also prevent cathodic protection from functioning normally within the controlled potential range, cause sacrificial anodes to undergo polarity reversal, and result in cathodic protection failure.

For pipelines with cathodic protection, an ideal method to mitigate AC interference is to use solid-state decouplers combined with grounding drainage. This approach helps prevent the loss of cathodic protection current while effectively alleviating AC interference on the pipeline.

Solid-state decouplers are AC interference protection products with the function of "blocking DC and passing AC." They offer high steady-state AC interference current, fault current, and lightning surge conduction capabilities, along with extremely low DC leakage levels. These products can be installed at locations where pipelines run parallel to or cross high-voltage transmission lines and electrified railways, as well as at centralized grounding points in stations and valve chambers. They provide protection against AC interference, fault currents, and lightning surges for metal pipelines while avoiding the loss of cathodic protection current. As DC isolation and AC conduction devices, solid-state decouplers block DC current conduction within a certain voltage range, such as -2V to +2V or -3V to +1V, while providing a low-impedance path for AC current. When the voltage between the two terminals of the solid-state decoupler exceeds the DC conduction threshold, it enters a low-impedance DC conduction mode. When the voltage drops below the DC conduction threshold, the solid-state decoupler returns to a high-impedance state for DC current, cutting off the DC flow. In the event of fault currents or lightning surge currents, the internal modules of the solid-state decoupler instantly conduct, discharging the interference current into the ground through grounding, thereby protecting pipeline facilities and personnel.

Application scope of solid-state decouplers: In cathodic protection systems, AC grounding and DC isolation of electrical equipment. Mitigation of AC-induced voltages. The main performance parameters of general solid-state decouplers are shown in the table.