The National Electrical Safety Code, powerline clearances, and wildfires

Abstract

The provisions of the National Electrical Safety Code (NESC) have a long, but undocumented history. They are the primary means by which Public Utilities Commission agencies in various States in the United States enforce requirements for electrical clearances pertinent to high‐voltage powerlines. Examination of the NESC provisions for clearances between grounded guy wires and distribution phase conductors in the context of the Woolsey Fire indicates a comprehensive lack of realism in the Code provisions. While they may be entirely sufficient to prevent sparkover under normal operating conditions, they are wholly insufficient to cope with even modest adverse events. The profession should consider explicitly assessing factors beyond sparkover that affect the adequacy of clearance requirements. The provisions of the NESC (and California's parallel General Order No. 95) should be systematically reexamined in order to ensure that safety regulations can cope with adverse events that are serious, but not extreme. Since the vast majority of the electrical power network is aging and not new construction, a scheme should be developed to establish priorities for upgrading existing facilities at the highest risk of failure.