{"id":48801,"date":"2026-04-13T11:19:15","date_gmt":"2026-04-13T18:19:15","guid":{"rendered":"https:\/\/brainfiller.com\/?p=48801"},"modified":"2026-04-13T12:09:19","modified_gmt":"2026-04-13T19:09:19","slug":"absence-of-current-nfpa-70e","status":"publish","type":"post","link":"https:\/\/brainfiller.com\/es\/technical-articles\/absence-of-current-nfpa-70e\/","title":{"rendered":"2027 NFPA 70E – Absence of CURRENT"},"content":{"rendered":"
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NFPA 70E Hazard Elimination - Absence of Current<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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NFPA 70E emphasizes hazard elimination as the first priority in the implementation of safety-related work practices. This requirement is normally met by establishing and verifying an electrically safe work condition (ESWC) in accordance with NFPA 70E 120.6. Step seven of this process requires determining the absence of voltage<\/strong> to confirm that a circuit is deenergized and safe to work on.\u00a0 However, the 2027 edition recognizes absence of voltage may not be enough.\u00a0\u00a0

From the NFPA 70E perspective, when a person is within the limited approach boundary or is interacting with equipment in a way that increases the likelihood of an arc-flash injury, circuits operating at 50 volts or greater<\/strong> must be placed into an electrically safe work condition before work is performed (a few exceptions exist). Equipment operating below 50 volts is normally considered a minimal risk. However, this assumption can be misleading.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Low Voltage May Not Mean No Hazard<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Some circuits operate at voltages well below 50 volts and yet can still present a potentially serious hazard. This seems counterintuitive.<\/p>

We typically think of electrical systems as having a fixed voltage \u2014 for example, 480V \u2014 with current varying based on the load. Under the fixed voltage model, no voltage means no current, and therefore no hazard.<\/p>

In most cases, that\u2019s true – but not all circuits behave that way.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Current-Driven Circuits<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Some types of circuits function as a constant current source. In these cases, the current remains relatively steady while the voltage varies. For some current-driven circuits, the voltage can be quite low under normal conditions.\u00a0 This can challenge the traditional assumption that absence (or almost absence) of voltage equals safety. In other words, low voltage does not necessarily mean low risk.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Airfield Lighting Circuits<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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One example of a current driven circuit is airfield lighting. These series circuits are current regulated performing like a constant current source.\u00a0 Airfield lights work on low voltage from the secondary of an isolation transformer. \u00a0A potentially significant hazard is created when the secondary of the isolation transformer is open circuited.\u00a0 This can occur when a light is removed or burns out, causing the transformer to produce a hazardous voltage to the lamp connection point. To determine that the circuit is de-energized a true RMS ammeter<\/strong> is used to test for absence of current<\/strong>. (See Federal Aviation Administration (FAA) Advisory Circular 150\/5340-26C, Maintenance of Airport Visual Aid Facilities).<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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2027 NFPA 70E and Absence of Current<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The 2027 NFPA 70E will now address this issue. While still in the final stages and not yet published as of this writing, the intent is clear: voltage alone may not always be sufficient to verify that a circuit is safe.<\/p>

The 2024 Edition of NFPA 70E 120.6 Proceso para establecer y verificar una condici\u00f3n de trabajo el\u00e9ctricamente segura<\/em><\/strong> contains eight steps, with step seven<\/strong> being the test for absence of voltage.<\/p>

El 2027 Edition<\/strong> will add a new exception to this step:<\/p>

Exception No. 3 to 7:<\/strong> If testing for absence of voltage alone does not indicate that electrical conductors and equipment are deenergized, then additional methods of testing<\/strong> shall be required.<\/em><\/p>

This new exception also has a new Informational Note to provide further guidance.<\/p>

Informational Note to Exception No. 3:<\/strong> An example of additional methods include testing for the absence of current<\/strong> in current-driven circuits.<\/em><\/p>

This language acknowledges that there are circuits where voltage alone may not be the best indicator of electrical hazards. Recognizing those situations \u2014 and verifying both voltage and current where appropriate \u2014 is a necessary step to eliminate the risk.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Acerca de Jim Phillips<\/h2>

With a career beginning in 1981 and Brainfiller launching in 1987, Jim has built a global reputation as a trusted leader in electrical safety.<\/p>

He currently:<\/p>