Corrosion protection for gas-insulated transmission lines

For buried gas insulated transmission lines (GILs), a coating against corrosion is absolutely necessary and similar to most other directly buried metallic installations. Active corrosion protection, also called catholic protection, may be added to take care about possible failures of the coating as an additional quality insurance system to the passive corrosion protection. Failures in the passive corrosion protection may occur over the lifetime of the system by outer damage through other earth works or by cracks or voids in the material. Then the active corrosion protection system protects such cracks and voids in the passive corrosion system against corrosion. This article proposes some solutions able to protect the GIL against the corrosion by using both the passive and the active corrosion protection.