Results of BIL Testing on Steel Poles Conducted for AISI at NEETRAC Test Facility

Executive Summary

During the week of April 8th, 2002 a series of BIL (Basic Impulse Insulation Level) tests were successfully conducted on steel poles at the NEETRAC High Voltage Laboratory in Forest Park, GA at the request of AISI (American Iron and Steel Institute). The test configurations consisted of various combinations of wood and fiberglass components, complete with 15 kV and 25 kV porcelain and polymer insulators, mounted as required on a steel pole.

The certified independent test results clearly demonstrate that numerous solutions exist to achieve a 300 kV BIL level (if desired) with steel poles. Detailed below are several options for meeting a 300 kV BIL level for both single phase and three phase construction.

Options to Achieve 300 kV BIL Level (If Desired) With Steel Poles

1) Single Phase
Use 13 inch or 14 inch fiberglass pole top pin


  • 114 kV BIL level achieved with steel pin and 15 kV insulator
  • 141 kV BIL level achieved with steel pin and 25 kV insulator

2) Three Phase

2.1) Horizontal Crossarm Construction

  • 8 foot wood or fiberglass tangent crossarm, in conjunction with 13 inch or 14 inch fiberglass pole top pin on center phase
  • 8 foot fiberglass deadend crossarm
  • 10 foot wood tangent crossarm with all phases located on the crossarm, in accordance with the following criteria:
  • center phase located at minimum 31" from pole center
  • adjacent phase located on same side of arm and at minimum 27" from center phase
  • outside phase located on opposite side of arm at minimum 37" from pole center
  • wood crossbraces required

2.2) Vertical Construction

  • 12 inch fiberglass links and polymer insulators

PowerPoint Presentation:
Steel Distribution Poles - The Material of the Future (pdf - very large) by Brian Lacoursiere, P.Eng., V.P. Engineering, Utility Products, IUSI (International Utility Structures Inc.)

Downloadable PDF files:
Final report: AISI Overhead Distribution BIL Testing Addendum to Final Report: AISI Overhead Distribution BIL Testing