DC Decoupling from Utility Grounding Systems
Pipeline facilities and tank farms, among other similar cathodically protected sites, need to have manageable CP current requirements to achieve acceptable industry CP potentials for compliance. However, the facility bond to the power company grounding system can make this difficult. An unknown, and large, amount of buried metallic area exists on the power utility system, in the form of copper ground rods and other grounding electrodes. This excessive bare area becomes part of the cathodically protected structure from a current-requirement perspective, overwhelming the facility CP design goals.
The common tie between cathodically protected facilities and power utility grounding systems is the bond that exists at the electrical service. Specifically, the primary-to-secondary neutral bonding system facilitates cathodic protection current flow between the two facilities. However, this bond exists to meet safety requirements and cannot be simply separated for convenience.
Solid-state decouplers provide an acceptable method to address cathodic protection issues along with safety bonding. These devices block direct current from active or passive sources, while simultaneously appearing continuous for ac power frequency signals. A suitably rated decoupler can be installed as the bond between the two grounding systems. This results in a great reduction of CP current required, limits interference with other structures, and allows CP potentials to achieve industry compliance.
This paper provides specific information on decoupler installation to solve facility CP problems, including connections, possible bypasses, practices, and codes.
Download this white paper from Dairyland Electrical Industries today to find out more.