Forensic Engineers and Consultants

Blog Posts by: Tom Kelly

Author Tom Kelly

Expertise Includes:

  • Electrical Equipment Failures
  • Electrocution & Electric Shock Accidents
  • Fires & Explosions
  • High Energy Laser Design
  • Industrial Electrical Accidents
  • Lightning Strike Analysis
  • Robotics & Automation
  • Scope of Damage - Estimate of Repair
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T is for Temporary – Issues with Extension Cords and Other Temporary Wiring Applications

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Temporary wiring is just that….temporary, and is typically used for repair and maintenance projects.  In this blog I am going to discuss guidance offered by Article 590 of the National Electric Code (NEC), as well as some points to consider when using temporary wiring, including extension cords and holiday lighting.

Before each use, extension cords need to be inspected for visual damage.  Cords with cuts or splits to the insulation need to be discarded.  Cords with damage to the connectors, including those that feel loose when connected, need to be taken out of service.   Failure to properly select and use extension cords can have a catastrophic result.  Read More

TVSS or SPD … Can I Buy a Vowel? Understanding Surge Protection and the Changing Requirements

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Surge Protective Devices (SPD), formerly known as Transient Voltage Surge Suppressors (TVSS) have been around for a long time.   The most recognized version is integrated into outlet strips and used to protect sensitive electronics from surges, or higher than expected voltages on the power line.  Early versions of these surge strips were known to have problems where internal components could overheat and cause a fire.  Thermal protection was added to the designs to greatly reduce the potential for a fire hazard.  Such an implementation in an outlet strip is considered a Type 3 SPD. Read More

In a Flash – The Transfer of Energies in Our Global Electrical System

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According to published weather data for the year 2019, 2.35 billion lightning strikes were recorded across the world, with 223 million of these in the United States.  The movement of atmosphere causes electrical charges to build up between clouds.  A tipping point is reached where the insulating properties of the air cannot withstand the level of energy and a discharge occurs.

Image Credit: Charleston Post and Courier. A lightning strike over Charleston, SC on July 3, 2019.

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The Demise of Insulation on Electrical Wiring

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Unlike fine wines and some types of cheeses, not everything ages well.  Such is the case with the materials used as insulation of electrical wiring.  While the copper metal used as the conductor in many wire types will last virtually forever, the cladding used to protect and insulate the wire allowing electrons to flow to their final destination does not. Read More

Hidden Heat: The Unseen Hazard of a High Resistance Connection

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A typical residence can have upwards of 10,000 feet of electrical conductors installed, most of which are buried in the walls, attics and crawlspaces.  A commercial building can have 100,000 to upwards of 1 million feet of electrical conductors.  At each device such as a switch or a receptacle are at least three, and typically six or more connections of these conductors within a junction box.  The connections can be in the form of twisted connectors, screw terminals, push in terminals and crimped connectors.

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Hazards Can Lurk Anywhere … Watch Your Step …

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While on a lunch stop during a recent vacation trip through Tennessee, I happened across a safety hazard that required immediate attention.  The establishment had a raised concrete patio at the front with a steel railing around the perimeter.  At one edge of the patio was a set of stairs with a continuation of the steel railing used as a handrail.  The top edge of the patio had light strings wrapping the top metal bar as accent lighting for the perimeter.  The light string continued down the stair handrail wrapped in the same manner as the rest of the patio. Read More

Testing…testing… Is this thing on?

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Many people just take for granted that something is just going to work, and in many cases assume that it will work forever.  One such device that does not get enough attention is the Ground Fault Circuit Interrupter (GFCI).   Simply put, a GFCI is a protective device that compares the current flowing on the hot and neutral wires of the circuit and will “trip” to disconnect power to the circuit if a small imbalance of current is detected.  The imbalance of current is an indication of a dangerous alternate path for the current to flow from a damaged line cord or a fault inside an appliance and constitutes a shock hazard to a person. Read More

Ready, Set, Fly! – Understanding Another Technology for Forensic Investigations

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This is the first blog in a series on integrating new technologies into the process of forensic investigations.  Documenting the scene of an incident accurately, efficiently, and safely is a key step in every investigation.  Busy roadways and unstable structures present hazards to the investigator during the investigation process. The use of remote sensors can reduce these risks and provide data that otherwise could not safely be obtained. Read More

Grounding versus Bonding – Understanding the Difference in Building Electrical Systems

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While a teenager might be very familiar with being “grounded”, there is confusion over the meaning of the word in the electrical sense. In building electrical systems, “grounding” and “bonding” are two terms that are often misunderstood. Improper application of the concepts of grounding and bonding may create lethal shock and fire hazards. “Earthing” is a term which comes from the European International Electrotechnical Committee (IEC). Earthing is synonymous with grounding but often thought to have a different meaning. Read More

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