Gas pipeline electromagnetic protection solid-state decoupler

In existing technology, when testing solid-state decouplers, the common practice is to visually observe or use a multimeter to measure the continuity of the solid-state decoupler. When it is determined that the solid-state decoupler is in an open state, it is considered damaged. This testing method is inaccurate and inefficient.

The location of the drainage point largely determines the effectiveness of drainage. Preliminary research in practice on the effective distance of solid-state decouplers has found that while a single solid-state decoupler can reduce the AC interference voltage near the drainage point, it can increase the AC interference voltage at points farther away from the drainage point, with some pipeline segments experiencing significant increases. Therefore, in AC drainage for pipelines, the use of solid-state decouplers should be based on the on-site interference conditions and applied with principles to meet the requirements of AC mitigation.
Currently, both domestically and internationally, there is a lack of corresponding testing methods and standards for solid-state decouplers, including clamp-type drainage devices. The quality of products varies widely, and there is a lack of long-term tracking, testing, and evaluation of the performance of related products, making it difficult or impossible to judge product quality. When failures occur, timely repairs are also challenging. Therefore, relevant standards for the testing and inspection of drainage equipment should be established and implemented as soon as possible.
It is recommended that, when conditions permit, drainage implementation should adopt a step-by-step design and construction approach, supplemented by synchronous testing methods, to determine the placement of the next drainage point based on post-drainage results. Solid-state decouplers have lower requirements for grounding materials, as long as the grounding resistance meets relevant standards. However, international experience indicates that decoupler failures often result in a short-circuit state, so the selection of grounding electrode materials must be considered. It is important to note that during the construction of grounding electrodes, they must not come into contact with high-voltage transmission line towers, substations, communication towers, or the grounding systems of large buildings, as this could divert fault currents to the pipeline during lightning strikes or high-voltage transmission failures.

Solid-state decouplers utilize the fast response characteristics of varistor-type surge protectors, the high current tolerance, and low residual voltage characteristics of spark gap-type surge protectors to drain and limit voltage from direct lightning strikes and induced lightning.

① Energy coordination between spark gaps and surge protectors. When there is a short-term high current, the surge protector acts first, followed by the spark gap after 25ns. The conduction voltage is 45V, and the spark gap's rated discharge current is 50kA (10/350μs waveform for direct lightning strikes), effectively reducing the impact of strong current surges such as direct and induced lightning on the pipeline.

② When there is long-term DC or AC interference, diodes and capacitors activate, limiting the pipeline potential between -1.4V and +0.7V, ensuring that the cathodic protection effect is not affected by drainage grounding.

③ By coordinating the energy handling of diodes, spark gaps, and surge protectors, the impact of DC and AC interference on the pipeline's cathodic protection system can be eliminated.