Verifying the absence of voltage
New technology improves how tests are conducted
We work in remarkable times. To stand for safety means to stand for innovation in a more connected and efficient world. In today’s market, where skilled workers are in high demand, and tenured workers are harder to find, it’s incumbent on the purchasers of electrical equipment to demand, and manufacturers of electrical equipment to create, new products that make it safer to work with electrical systems.
Workers depend on the right tools to get the job done. And workers depend on their employers to ensure they’re equipped with the right tools, the right conditions, and the right processes to get the job done safely. It’s those conditions and processes that can — and are — being improved. For electrical work, this includes de-energizing equipment, following lockout and tagout procedures, and verifying the absence of voltage.
As facilities today attempt to make the process of establishing an electrically safe work condition an easily standardized practice, they’re faced with the critically important and frequently performed task of verifying absence of voltage. When working on or maintaining electrical equipment, the electrical worker must comply with safety regulations that require a voltage verification test to validate the absence of voltage.
This process includes several stages that can be complex and time-consuming when using hand-held portable test instruments. Each step in the process needs to be carried out, thoroughly and in order, every time the process is performed, which makes experience and training critical. When electricians and technical personnel at a large chemical company were asked, “How do you test for the absence of voltage?” more than 90 percent did not know how to perform a thorough test.1 Without question, electrical worker training is critical, but it’s never the sole solution.
A new approach to an old problem
The Absence of Voltage Tester (AVT) is a relatively new innovation. Unlike traditional voltage testers, the AVT is not portable and is installed in the equipment it is testing. Thoroughly different in its application, and more comprehensive than a permanently-mounted voltage indicator, an AVT is used to determine if and when a circuit part is de-energized before opening doors and removing covers from electrical equipment.
While voltage indicators merely provide a visual representation when voltage is present, they are not capable of testing for, nor indicating that a de-energized condition exists. For instance, if a voltage indicator is not illuminated, it may be because the system is de-energized, but it could also be due to a device failure, an installation failure (if the device becomes disconnected from the wiring, it will not detect voltage), or an indicator (e.g., LED) failure. These are some of the reasons permanently installed voltage indicators were never recognized by OSHA as an alternative to the voltmeter test.2
AVTs are defined in a new product listing category that was added to UL 1436, the Standard for Outlet Circuit Testers and Similar Indicating Devices, in September 2016. With the addition of these new requirements, products can now be listed and labeled as an absence of voltage tester.
The AVT’s listing requirements were brought about by research presented at the 2016 IEEE Electrical Safety Workshop on electrical injuries that occurred while voltage testing. Because there were no installed devices designed specifically to test for the absence of voltage, unique listing requirements for such a product were not addressed by standards for other product categories. Recognizing this, UL set out to define requirements and identify the best place to publish them. Ultimately, UL 1436 was selected because its scope included other installed testers and it could be revised in a timeframe that coincided with the NFPA 70E 2018 revision cycle.
The procedure for verifying the absence of voltage gets an upgrade
When NFPA 70E released its 2018 update, a new exception was included that allows AVTs listed to UL 1436 to be used to verify the absence of voltage instead of a handheld voltmeter. The process used by AVTs today is based on the steps described in NFPA 70E. AVTs listed to UL 1436 are required to “test the tester” before and after checking for AC and DC voltage. The requirements also include an additional step to verify that the tester is in contact with the circuit parts being tested. This is a critical feature for installed testers and one that is not satisfied by products such as voltage indicators and test portals. In addition, AVTs are required to be designed in such a way to ensure that hazardous voltage is not present on the outside of the door, a feature that is not incorporated into voltage indicators and test portals. AVTs rely on active indicators that meet SIL 3 functional safety requirements to confirm that the absence of voltage has been verified, something that voltage indicators lack.
In the electrical industry today, it’s encouraging that NFPA 70E is taking a clear path to embrace prevention through design. The design of equipment, components, and systems with safety in mind is exactly what we need for a safer and more productive workplace. We need to be able to take advantage of new technologies and to innovate, in every way we can, to incorporate inherent safety features that undoubtedly protect workers from serious risk. An important note needs to be made: that a portable voltage tester is one of the best tools an electrical worker has, and the AVT is not meant to replace its troubleshooting functionality. The AVT is simply another tool with listing requirements developed specifically for the purpose of making one frequently performed task safer.
There are no limits to safety by design. In the consumer product marketplace, safety is not a feature or a benefit, it’s a clear expectation. That same expectation doesn’t always exist in industrial facilities, equipment and electrical system design, but prevention through design is taking a hold and AVTs are one example of electrical safety innovation.