When separating the protective object and nonprotective object electrically as seen in below figure, insulating joint or insulating flange is installed. The insulating material is non-metal and may be damaged when high voltage like lightning flows in the pipe, so this device prevents the damage of insulating facility by establishing electrically safe paths on both ends of insulated facility (constant AC passage, DC protection current blockage, and DC passage of abnormal high-volage).

When grounding the underground pipelines subject to protection, massive protection current flows in and does not reach the pipe that needs protection, resulting in decreased protection efficiency and corrosion as seen in Figure 2.
If it is grounded using this DC decoupling device, AC always flows through, while DC is blocked at protection current level (-6~+1VDC) and high-volage DC passes through, which maintains the grounding function and blocks the inflow of protection current to nonprotective object for increased protection efficiency as seen in Figure 3.

• 

  [Figure 2_ Piping without DC decoupling device :
  Protection current flows into the ground and causes pipe corrosion]

• 

  [Figure 3_ Piping with DC decoupling device :
  Blocks protection current inflow to the ground, and protection AC passes through constantly]

• 

  [Figure 4_J Protective DC decoupling device (JP)]

• 

  [Figure 5_DC decoupling device on the ground in electric motor valve of pipeline (PCR)]

1) Protection measures
DC decoupling device is a device that prevents damage of insulation structure, improves protection efficiency, and prevent electric shock accidents by allowing lightning stroke surge, AC, and high-voltage DC within the range that does not affect insulation structure or in cathodic protection system authorization. As relevant technology does not exist in Korea, local development of the product is needed through benchmarking of foreign products and supplementation of problems seen in field application in Korea.

2) Lightning stroke surge measures
DC decoupling device plays a significant role in preventing damage of insulation joint in pipeline due to lightning. If high-voltage lightning causes insulation damage in insulation joint, massive lightning current flows through insulated joint, damaging this area. In order to solve this problem, the path to discharge (pass through) potential difference (voltage) needs to be formed at both ends of insulated joint.

1) Economic aspect
This product or technology has not been developed in Korea, so the entire quantity is imported at high cost. Localizing the developing the product in Korea and applying it to relevant facilities such as KOGAS can contribute to the development of this technology and cost reduction of infrastructure management at the national level, as well as satisfying demands in protective grounding of similar pipeline, plants, vessels, and bridges.

2) Industrial aspect
Electric corrosion prevention device and DC decoupling device field is relatively underdeveloped worldwide, its technology level is not high, and the price is high /Therefore, developing the product with better technology and price competitiveness can contribute to the development of national industry through export.

1) Development of localized product that replace costly foreign protection product accumulates technology and field know-how, and can develop the market in similar industries such as pipeline, plant, vessel, and bridges and solve the conflict between method and grounding, expand the technology in lightning protection measures, which will secure the technology that can develop competitive lightning protection grounding device in growing lightning protection market.

2) Localized product can be sold to the Asian region (Thailand, Malaysia, India, Indonesia, and Taiwan) and Germany (customer), and the relevant technology can be led through the export of localized product to the relevant companies in the U.S. and Canada.

Development of price-competitive product can replace the imported foreign products, generating national benefits, and pioneering the new export market for the relevant product can generate continuous income.