Low and High Voltage
For the purposes of the National Electrical Code (NEC), voltages under 600 Volts A.C. are considered Low Voltage, and voltages over 600 Volts A.C. are considered High Voltages. Donan Engineering provides a variety of services regarding Electrical Engineering support. These include, but are not limited to: evaluation of house wiring resulting from fires, lightning damage, and code issues; fires or damage to appliances such as air conditioners, well pumps, and sump pumps related to alleged lightning damage.
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| Photo 1: Failure due to corroded connections on an air conditioner compressor, not the result of lightning damage. The closest lightning strike in this case was about 2.5 miles away. |
Other tasks include the evaluation of fires caused by ice or storm damage to power lines. The Utility primary voltage distribution is typically 7,200 Volts A.C. line-to-neutral voltage. The neutral on a residential and many business transformers carries through from the primary side to the secondary voltage side, typically 120/240 Volts A.C. single phase. Because of this, if the high voltage line breaks and comes in contact with the neutral, then the neutral of the house is energized at the 7,200 Volt level. The following photographs show where ice damage caused fires in several adjacent houses which were powered by the same transformer distribution lines.
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| Photo 2: The neutral line was on the ground and melted the surrounding ice and snow. |
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| Photo 3: An energized neutral in the house wiring. |
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| Photo 4: When a gas line is steel and grounded, even the flexible connecting lines to the furnace and gas appliances can overheat, potentially causing a fire. |
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| Photo 5: A storm-damaged and downed 7,200 Volt A.C. line that energized the secondary went into a residential electrical panel, causing a fire. The fire progressed up the wall and into the attic space, causing considerable damage to the roof and attic area. The fire would not have occurred if the Utility Company had walked the line and confirmed that it was clear behind a group of residences. The Utility Company linemen re-energized the substation breaker three separate times instead of determining what was tripping out the breaker. |
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| Photo 6: A piece of metal blew off of an adjacent building during a storm, shorting out the 12,470-volt side of high voltage switchgear, melting down the glass insulators, and burning holes in the top of the cabinet. When arcing occurs, the air surrounding the arcing area becomes ionized, and a “corona effect” is established. This corona, like a lightning discharge, will continue either until the system fusing is blown or until the utility company opens up the distribution line that serves the area of damage. Many times the arcing or corona will continue until the distribution is manually shut down at some distribution point. |
Donan Engineering can support your project needs, including storm-related damage, an electrical fire, or evaluation of electrical systems for potential subrogation purposes. Equipment inspections can also be done on either high-voltage items such as the one above, or on low-voltage items such as house wiring, appliance wiring, motors, controls, automobile fires, alarm systems, etc. Donan Engineering can also support your claims for arc-flash injuries to employees.