Ferc Account 357

FERC Account 357 records the cost of conduit systems installed for underground electric transmission cables.

Definition

Record in this account the cost of conduit, duct banks, manholes, and related structures used to house underground transmission cables.

Account 357 captures the civil infrastructure that houses underground transmission cables — the conduit, duct banks, manholes, handholes, and vaults. The cables installed inside the conduit are recorded separately in Account 358. This separation is important because conduit systems have much longer useful lives than the cables they contain, and cables may be replaced multiple times over the life of the conduit.

What is typically included

• Conduit, ducts, and duct banks for underground transmission cables
• Manholes, handholes, and cable vaults on transmission cable routes
• Concrete encasement and backfill costs for conduit systems
• Trenching and excavation costs for conduit installation
• End bells, seals, and conduit fittings

What is generally not included

• Underground cables installed within the conduit (Account 358)
• Underground distribution conduit (Account 367)
• Conduit within substation yards (included in Account 352 structures)
• Temporary excavation support not added to the permanent conduit system
• Road restoration costs beyond the minimum required by permit

Why this account matters

• Separates long-lived conduit infrastructure from shorter-lived cables for depreciation
• Enables proper retirement accounting when cables are replaced without replacing conduit
• Required for FERC Form 1 underground transmission plant detail
• Supports transmission rate base calculations for underground facilities
• Facilitates asset management by tracking conduit capacity and condition separately