FERC Account 358: Underground Conductors and Devices (Transmission)

FERC Account 358 records the cost of underground cables, conductors, and devices used in electric transmission systems.

Definition

Record in this account the cost of underground cables, conductors, and associated devices used in electric transmission operations.

Account 358 captures the cost of high-voltage underground transmission cables, including the cable itself, splices, terminations, and associated devices. The conduit system that houses these cables is recorded separately in Account 357. Underground transmission cables are typically used in urban areas, under waterways, or where overhead construction is not feasible.

What is typically included

• High-voltage underground transmission cables (XLPE, PILC, or other types)
• Cable splices, joints, and terminations
• Cable pulling and installation labor and materials
• Surge arresters and protective devices associated with underground cables
• Oil pressure systems and monitoring equipment for pipe-type cables

What is generally not included

• Underground conduit, duct banks, and manholes housing the cables (Account 357)
• Underground distribution cables (Account 367)
• Substation cable connections within the substation fence (Account 353)
• Cable replacements treated as maintenance expense
• Temporary cables used during construction (charged to CWIP)

Why this account matters

• Separates cable investment from conduit infrastructure for depreciation purposes
• Enables proper retirement accounting when cables are replaced in existing conduit
• Required for FERC Form 1 underground transmission plant reporting
• Supports cost-of-service studies for underground transmission facilities
• Provides asset management data for cable condition monitoring and replacement planning