Forensic Electrical Power Engineering

ELECTRICAL SAFETY FOUNDATION INTERNATIONAL RAISES AWARENESS OF NEW UL AND CSA REQUIREMENTS FOR GFCIs

A GFCI is a device that interrupts current before it reaches a level that would cause injury. The National Electrical Code(NEC) requires GFCIs to be used in bathrooms, kitchens, garages, basements, crawlspaces, and outdoors. Before the introduction of GFCIs in the 1970s, more than 700 people died from household electrocutions each year. As of 2001, that number had been reduced to 400 cases annually. A 2001 UL and NEMA field study determined that a small but significant percent of GFCIs, particularly older ones, did not work after several years. This created a demand for more stringent safety features that can alert users when a GFCI malfunction. The new UL and CSA requirements include

End of Life Provision: when a GFCI receptacle can no longer provide ground fault protection it will either render itself incapable of delivering power, or indicate by visual or audible means that the device must be replaced.

Reverse Line-Load Miss-wire: a GFCI will deny power to the receptacle face if it is miss-wired.

In 2000 a very large industrial facility in the Chicagoland area was experiencing process interruptions. It believed that low voltage from the utility serving the facility was causing electronic controls to malfunction and interrupt the processes. Discussions with the utility did not yield a solution to the problem.

The Electric Detective analysed the voltage records maintained by the facility and performed a number of computer scenario studies. The conclusion was that the low voltage from the utility was indeed the culprit in the process interruptions.

The proposed solution was to replace the four existing electric utility transformers feeding the facility with four transformers that were equiped with voltage regulaors. The utility did not agree with this solution despite the fact that the industrial customer would bear the total cost of the transformer replacement. The customer pressed its case in a meeting with the utility in which the Electric Detective presented the results of his studies and rebutted all of the utility’s objections. The customer prevailed. The transformers were installed.
Since the installation of the new transformers there have been no voltage related process interruptions.

Let the Electric Detective help you solve your voltage related problems.

A cable TV technician had climbed up an electric utility pole to which the cable equipment was attached. He reached out from the ladder that he had placed against the pole to adjust the cable equipment and put one hand around the pole to steady himself. He received a fatal shock and was thrown to the ground where he was declared dead.

What happened? The cable equipment was grounded at the pole and at every other pole on the line. How did he get the fatal shock? A review of the scene of the accident revealed that on the opposite side of the pole from the ladder there was a wire running up and down the pole. This is supposed to be grounded and is normally used to ground the lightning protection wire attached to the top of the pole. At some time prior to this the electric utility had eliminated the lightning protective wire to make room for another electrical circuit at the top of the pole. As part of that work it had cut the ground wire at the top and at another point lower down on the pole but had not secured it properly at the top of the pole. The ground wire had become loose and contacted one of he hot wires at the top of the pole. Because of this the ground wire was not grounded and was in fact a hot wire. When the technician reached around the pole to steady himself he contacted the hot ground wire while he was touching the grounded cable TV equipment causing his body to conduct current to ground. The current magnitude was large enough to cause a fatal shock.

The Electric Detective reviewed the facts and the depositions of witnesses to the accident and provided a written report to the attorney representing the technician and the case was settled out of court in favor of the family of the deceased.

The moral of the case? Never assume that electrical wires are safely grounded. Check with a voltage detector.

Proper grounding of electrical equipment is very importnat for the safety of people that may come in contact with the equipment. The sketch below shows what happens if the ground wire in the cord to the appliance is not connected. The neutral (the white wire) is grounded at the source of power but not connected to the body of the appliance. The ground wire (bare copper wire) is connected to the body of the appliance and to ground. Make sure the ground wire is intact and connected.

Tom has over thirty years of experience in the technical and managerial aspects of elctrical power design, analysis and trouble shooting.  He has published over a dozen techincal papers in industry journals one of which received an IEEE paper award.

He is a Registered Professional Engineer (PE) in the States of Florida, Illinois, Michigan and Wisconsin.

He is also a certified fire and explosion investigator - certified by the National Association of Fire Investigators (NAFI)

Welcome to the Forensic Electrical Power Engineering blog. What is forensic engineering?

Forensic engineering is the application of engineering principles and experience to determine the cause of equipment/structure failures, accidents and mis-operations. In the electrical power field it involves determing the cause of electrical mal-functions, poor power quality, poor power system performance (low voltage, transients, interruptions) and accidents in which property or people are injured by electrical equipment or systems.