One of the many new additions to the 2018 edition of NFPA 70E is the term “priority,” which states, “105.4, Priority: Hazard elimination shall be the first priority in the implementation of safety-related work practices.”
Hazard elimination also happens to be the first step in the risk control hierarchy that is listed in 110.1(H)(3). By now, the concept of hazard elimination and the electrically safe work condition should be firmly drilled into the brains of everyone who works on or near electrical power systems. If not, start drilling!
To eliminate the hazard, NFPA 70E 120.5 provides detailed steps to establish and verify an electrically safe working condition. One of the last and most important steps of this process is to verify the absence of voltage—i.e., the hazard has been eliminated.
As 120.5(7) states: “Use an adequately rated portable test instrument to test each phase conductor or circuit part to verify it is de-energized. Test each phase conductor or circuit part both phase-to phase and phase-to-ground. Before and after each test, determine that the test instrument is operating satisfactorily through verification on any known voltage source.”
The last sentence is commonly referred to as “live-dead-live” testing.
Two new exceptions in 120.5(7)
The words “adequately rated” cannot be overemphasized because even checking for the absence of voltage has its own risk. Many years ago, I wrote a column about a colleague named Henry who had been performing voltage testing and mistakenly contacted 4,160-volt (V) equipment. The meter exploded, causing a massive arc flash. Sadly, he did not survive.
Many things went wrong, including lack of training and not wearing arc-rated-protective equipment. However, way back then, it was not required.
120.5(7) Exception No. 1 was added to reduce the likelihood of this type of incident. It states: “An adequately rated permanently mounted test device shall be permitted to be used to verify the absence of voltage of the conductors or circuit parts at the work location, provided it meets all of the following requirements. The requirements include (1) It is permanently mounted and installed in accordance with the manufacturer’s instructions and tests the conductors and circuit parts at the point of work; (2) It is listed and labeled for the purpose of verifying the absence of voltage; (3) It tests each phase conductor or circuit part both phase-to-phase and phase-to-ground; (4) The test device is verified as operating satisfactorily on any known voltage source before and after verifying the absence of voltage.”
Henry’s very unfortunate incident is just one example that supports the addition of the new exception in the 2018 edition of NFPA 70E.
The following text was provided as a Statement of Problem and Substantiation for Public Input: “The process of verifying the absence of voltage is usually performed with a handheld test instrument and relies primarily on PPE and administrative controls to mitigate the risk of exposure to electrical hazards. When using a handheld tester, the person performing the voltage verification test is exposed to electrical hazards. …it is susceptible to mistakes, errors and interruptions.”
Absence-of-voltage testers (AVTs) are permanently-mounted testers used to determine if a circuit part is de-energized before opening doors or covers to access electrical equipment. AVTs are a new product listing category that was recently added to UL 1436, Standard for Outlet Circuit Testers and Similar Indicating Devices. AVTs are designed to run internal diagnostics to perform the live-dead-live type of verification with a secondary test source and actively indicate the absence of voltage for fixed installations.
For systems over 1,000V, 120.5(7) Exception No. 2 was added: “On electrical systems over 1,000 volts, noncontact test instruments shall be permitted to be used to test each phase conductor.”
A new Informational Note 2 was added to provide additional information on the rating and design requirements for voltage detectors. This includes referencing three standards from the International Electrical Code (IEC) 61243 series. These are from the IEC Live Working Technical Committee 78, which I chair:
- IEC 61243-1, Live Working—Voltage Detectors—Part 1: Capacitive type to be used for voltage exceeding 1 kilovolt (kV) AC
- IEC 61243-2, Live Working—Voltage Detectors—Part 2: Resistive type to be used for voltages of 1 kV to 36 kV AC
- IEC 61243-3, Live Working—Voltage Detectors—Part 3: Two-pole low voltage type
A new normal?
Like any new concept that deviates from the norm, there will always be resistance to change. Will the industry embrace the new exception for AVTs? Only time will tell, but one thing that won’t change is the need to eliminate the hazard.