Forensic Investigation Techniques for Inspecting Electrical Conductors Involved in Fire

• NCJ Number: 239052
• Author(s): Richard J. Roby, Ph.D.; Jamie McAllister, Ph.D.
• Date Published: July 2012
• Length: 259 pages
• Grant Number(s): 2010-DN-BX-K246
• Sponsoring Agency: National Institute of Justice (NIJ)
• Sale Source: National Institute of Justice/NCJRS; NCJRS Photocopy Services
• Publication Format: Document; Document (Online)
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This research determined whether there are distinguishing characteristics for energized and non-energized wires subjected to various types of fire exposures, so as to gain an understanding of the various electrical and thermal conditions that can produce beads on electrical wires.

Abstract

Based on preliminary studies conducted by the authors, they hypothesized that characteristic "arc-beads" could form on non-energized wires as well as energized wires. In addition, they hypothesized that the formation of a bead on a wire is not a function of its "energized state," but rather a function of its "thermal state." These proposed hypotheses are different from the current state-of-the art in the field, which holds that beads can only be formed on energized wire. Although another review of all the test samples is still being conducted, the proposed hypotheses are supported by the current research findings and sample analyses results. No trends or distinguishing visual or microscopic characteristics between energized and non-energized wires were found in the samples reviewed to-date. Just over 190 wires were tested under various fire conditions. Wire types included 12-gauge and 14-gauge solid conductors and 16-gauge and 18-gauge stranded conductors. The tests were conducted with a bench-scale, pre-mixed flame-impingement apparatus, a bench-scale 125 kW/m squared radiant tunnel apparatus, a 2/5-scale flashover compartment, and a full-scale flashover compartment. The use of various types of exposure conditions ensured that the characteristics on the wires (or lack thereof) were not caused by one specific type of thermal assault. Wires were tested in both an energized and non-energized state. Energized wires were tested under "load" and "no load" conditions. Under load conditions, the energized wires were plugged into a 119-120 volt power source with 9 to 113 amps of current. Under "no load" conditions, the wires were plugged into the power supply, but no current was flowing in the circuit. Extensive photos of test results and figures and 36 references