First and foremost, this report is not a comprehensive safety guide. It is an overview that contains information and suggestions for safely using test instruments. Always comply with industry and company safety procedures, product manuals and applicable standards.
There is a wide range of instruments designed to test the performance of electrical systems, identify problems and discover potential issues that could prevent a system from operating safely and efficiently. While safety is a primary reason for testing, the use of testers involves serious safety risks.
“The most obvious, of course, is electrocution from incidental contact with live circuits,” said Jeff Jowett, senior application engineer at Megger, Dallas. “Also, there can be arc flash/arc blast if an instrument accidentally becomes energized at high voltage or if an ‘event’ occurs on the line, such as a lightning strike. And a hidden danger that can catch users unaware is static voltage stored on the test item at the conclusion of a test.”
A safety measure available today is moving the user away from the point of measurement, said Sean Silvey, product specialist at Fluke, Everett, Wash.
“Today, many test tools have the ability to send measured data to a remote location linked to a smartphone by Bluetooth, and then on to the cloud for storage,” Silvey said. “In practice, this means the user can de-energize a piece of equipment, connect the test tool, close the cabinet and then read and record the measurements from a safe distance.”
Jowett said advanced testers available today have warning functions that let the operator know if the circuit has become live. Lockout/tagout and safe working practices including the use of personal protective equipment are critically important for all workers. Many companies and standards agencies have written procedures.
“Of paramount importance for arc flash/blast protection, instruments should have a IEC 61010 rating, which defines how an instrument must be constructed with safe creepage and clearance distances between internal circuits so that arcing does not occur inside the instrument. [It] includes maximum rated operating voltage for the circuit and equipment that is being worked on,” Jowett said.
“Always use only test instruments that are properly rated for both the environment and operating voltage of what is being tested, and be careful of instruments that are not properly rated for all test circuits—some cut price by only designing the principle test circuits to comply with IEC while a less utilized function goes unprotected and possibly unadvertised, as well,” he said.
Jowett said testers that apply a DC current for a period of time, such as insulation testers and instruments that test large motors, generators and transformer windings and long runs of cable can store enough static energy to be lethal.
“Not to worry,” Jowett said. “Quality instruments today have a built-in discharge and warning circuit. Lights blink, a tone sounds and the item is automatically discharged with the voltage decay shown on the display. All the operator needs do is stand back and watch. Make sure that instruments have this discharge circuit and educate employees on its use.”
Refinements in electronic circuitry have vastly improved the safety of instrumentation by reducing the level of voltage and current required to make accurate measurements, Jowett said. Old instruments are often operated by balancing the load (the test result) against on-board resistors. Modern microprocessors often enable precise measurements that exceed the accuracy of older instruments while keeping test voltages and currents below injurious levels.
New safety features and improvements come at a record pace, so it’s extremely important to train personnel to familiarize themselves with features, make them aware of what to look for, what various indicators mean and either enhance or break old habits.
“To summarize, quality modern testers do it all—discharge automatically, warn the operator immediately and monitor the discharge on the display for full operator safety,” Jowett said.
Test leads also pose serious dangers.
“Many people have been electrocuted by faulty test leads. Leads seem so generic and simple and often are taken for granted and not regarded as a security risk. Leads may be carrying lethal voltage and current. In addition, they take a bigger physical beating than the instrument,” Jowett said. “Good quality leads may be multilayered, depending on intended use, and if so, the layers should be of different colors spot wear before dangerous bare copper is exposed. Always perform visual inspection of leads before starting a job.”
Finally, don’t lose sight of the importance of redundancy.
“Redundant safety provides more thorough safety. A single layer of protection might fail by human error, equipment failure, misapplication or totally unforeseen circumstances,” Jowett said. “In our industry, something can possibly occur that has never happened before. It is best to have a fallback safety net. A single accident will cost far more than all the relevant safety features together.”
Silvey said most common risks of using testers are taking shortcuts and not following established procedures.
“This usually is based on poor assumptions such assuming the power is off without confirming, or assuming gloves won’t be needed because no contact with anything will occur,” he said. “Wear personal protective equipment and test for the absence of voltage. Use tools described in NPFA 70E and the company safety manual.”
Any test that has the potential to create an arc flash should be viewed as extremely dangerous and only undertaken using the strictest safety procedures, Silvey said.
An arc flash is an electrical short circuit that originates from an exposed live conductor, and then travels through the air until it reaches another conductor or the ground, Silvey said. Arc flash happens when there is a breakdown of electrical resistance (or impedance) in the air surrounding a conductor.
“When a short circuit occurs, it can often cause an arc blast, a type of highly dangerous electrical explosion,” Silvey said. “Pressure waves generated by an arc flash explosion can carry a force of thousands of pounds per square inch, enough to knock down the technician and anyone nearby, and it can injure eardrums, lungs, the brain and other organs. An arc blast can reach temperatures of 35,000°F, create blindingly bright light and turn nearby equipment into dangerous projectiles
“Using test equipment improperly may result in nothing but a tripped circuit breaker, or maybe a blown fuse in the test tool. But the consequences can be more severe, [such as] damaging critical equipment connected to the electrical circuit,” Silvey said. “The severity of injury from an electrical shock depends on the path current takes through the body, the amount of current flowing, and the length of time of exposure. Depending on all these factors, the impact of electrical shock can include moderate to extreme injury and death.”
Silvey believes that in addition to new standard safety features such as fully fused inputs and warning signals to tell the user if the test leads and the dial positions don’t match, one of the biggest advances has been defining the CAT ratings for test tools, which helps to match the proper test equipment to the type of work being done.
Robust internal circuitry is one way to protect the user, and another is to move the user away from the point of measurement, Silvey said.
Many of today’s test tools have the ability to send measured data to a remote location, linked smatphone and then to the cloud using Bluetooth.
“In practice, this means the user can de-energize a piece of equipment, connect the test tool, close the cabinet and then read and record the measurements from a safe distance,” Silvey said. “Advantages [of] remote testing includes minimizing the time the user needs to wear full PPE when opening the cabinet to verify the unit is de-energized. It makes connecting the tool to test points less worrisome and allows readings to be taken over a very long period of time.”
“Several regulatory bodies publish rules and guidelines related to electrical safety training. OSHA, CSA and NFPA all have documents available concerning what kind of training is required for what type of work situation. Many companies also have extensive amounts of safety training material available,” Silvey said.
Inspection tools typically aren’t considered to be in the tester category, but they can be a valuable accessory product when examining wiring and connections in hard-to-access places.
Cable Ferret is the first compact, wireless closed-circuit inspection camera that also has cable-pulling capabilities, said Therese McNaughten, vice president of marketing and brand strategy at the Auckland, New Zealand, company. The free app for IOS and Android shows and records what the camera sees in real time with high-definition images, and the video is sent to a smart phone or device.
The wireless camera can be attached to any fish stick or glow rod and is equipped with an interchangeable hook and magnet for pulling and retrieving cables and metallic tools or other items such as a lost tool.
“Electricians now can effectively and efficiently locate and inspect, fault find, report with photo and video, and also retrieve metal tools and objects in dark difficult places such as behind drywall, beneath floorboards, or above drop ceiling tiles,” McNaughten said.
Test tools have more built-in safety features than ever before, Silvey said, but those are all useless unless the user knows, understands and follows the right safety practices when using the tools.