Working within stringent safety standards is essential, especially when measuring an electrical power system. National statistics indicate that electrician fatalities account for nearly one-tenth of all occupational deaths each year. Of those, nearly 50 are due to electrocution. Knowing what test or measurement tools to use can mean the difference between life and death. In light of these shocking statistics, you’ll find it interesting to know that many electricians are using equipment that does not comply with any standard at all.

Instruments that meet the requirements of International Electrotechnical Commission (IEC) standard 61010-1, and national standards based on it such as UL 61010B-1 and C22.2 No. 1010.1, provide transient protection levels that are far above the instrument’s maximum rated input.   This type of protection was not required in instruments designed to older standards such as IEC 348 and UL 1244.   Without this additional protection against transient overvoltages, which are becoming increasingly more common, serious injury or death can result.

Category IV covers the highest, most dangerous, level of transient overvoltage that electricians are likely to encounter in utility service to a facility.   For the electrician who works in Category IV locations, having appropriately rated test instruments is mandatory.   Electricians who do not presently require Category IV instruments should still consider them when purchasing new equipment.   The extra level of protection is extremely affordable.   There’s no need to compromise on equipment that limits future work opportunities.

Category Ratings Defined

As the category rating increases, the chances for and the severity of a transient voltage event increases. Tools are rated on their ability to withstand a voltage spike, which is applied through a specified level of resistance. (See table.)

Category IV-rated tools are designed to be used for testing on the primary supply source but also include 120- or 240-volt lines that power detached buildings or underground lines that power well pumps.

Category III-rated tools can withstand the transient voltage range that can be found on distribution circuits. These tools are used on fixed primary feeders or branch circuits. They are separated from Category IV utility service or other high-voltage source by at least one level or transformer isolation.

Category II-rated tools cover the local level of circuits for fixed or non-fixed powered devices. This includes most lighting, appliances, and 120- or 240-volt equipment inside a building.

Category I-rated tools are signal-level tools for telecommunications and electronic equipment. Transient voltage risk is limited, but exists, because of the distance and other equipment located between it and the primary electrical supply.   (IEC no longer specifies protection levels for Category I equipment.   Instead, the transient withstand capability of the equipment must be made known to the user.)

Latest UL standards

The latest UL standard, UL 61010B-1, specifies the general safety requirements for electrical test instruments.   It specifies material, design and testing requirements and the environmental conditions in which the standard applies.   Other important UL standards that apply to test instruments are UL 3111-2-031 for test probes and UL 3111-2-032 for hand-held current clamps.   This includes the current measuring portion of clamp meters.   UL is in the process of harmonizing the numbering of their standards so they match the IEC publications.   UL 61010B-1 is basically a re-issue of UL 3111-1, originally released in 1994.   It is expected that the standards for test leads and current clamps will be renamed in the near future.   UL is also expected to adopt Cat IV requirements for voltage-measuring instruments in 2003.   Its standards already cover Cat IV for probes and current clamps.

Making Safe Measurements

Before making a measurement, review the basics.   Has the proper instrument been selected, having the necessary features and providing overvoltage protection appropriate for the application?   The voltage and current ratings will be marked on the meter.   Review the meter’s instruction manual, and set the selector for the proper function.   This helps to avoid incorrect results and damage to the meter – or the user.   Always test the instrument on a known live circuit before performing their test on the unknown circuit.

Look for the mark of a nationally recognized testing lab on the meter, such as UL or CSA.   This assures that a third party has tested the product.   A CE rating does not guarantee that an independent lab evaluated the instrument for compliance to safety standards.

Don’t forget about the test leads or other accessories.   Their Category and voltage rating are just as important to user safety. Remember, wherever you need overvoltage protection, look for independent certification UL or cUL, and choose the category appropriate to the type of work you expect to accomplish. According to statistics, electrician fatalities rank tenth among all private industry occupations. To avoid becoming a statistic, you must remain knowledgeable about the test equipment you use on the job.

Cherea M. Ellis is senior product manager for Greenlee, a Textron company. She can be reached at (815) 397-7070 or cellis@greenlee.textron.com.

Striving for Safety through Education

by Tim Kopp As the electrical industry continues its quest to keep electricians safe, new standards and test instruments are continuing to be developed with safety and convenience in mind. Over the next 12 months, there will be a greater emphasis on safety and ergonomics. Measurement category ratings will exceed the minimum requirements. The tester housing will be shaped to fit comfortably in the electrician’s hand. Below are some safety tips to consider: Use recommended personal protective equipment such as a hard hat, safety glasses, earplugs, safety shoes, and fire-resistant clothing. Ensure that there are no atmospheric hazards. Ensure that the test leads are in good condition. Cracked, broken or worn test leads should be replaced. Make sure that the tester’s fuse is in good operating condition. Read and understand the instruction manual for the test equipment being used. If the instruction manual has been lost, contact the test equipment manufacturer to get another copy. Use the three-point test method. 1) take a measurement on a known live or operating circuit to make sure the meter is operating correctly. 2) Take the measurement on the unknown circuit being diagnosed. 3) retest the first known live circuit to make sure that the tester is still operating correctly after the test circuit. Ensure that the digital multimeter function switch setting and test lead connections to the meter are correct for the type of measurement to be taken. Ensure that the measurement to be taken is within limits of the digital multimeter. If the measurement to be taken is unknown, the digital multimeter should be set to its highest range. Finally, education is a very important component. Organizations like UL and the National Electrical Contractors Association offer seminars or software on safety. Some manufacturers offer training classes that are designed to help end-users and distributors become familiar with test instrument products by using them. Look for classes that are hands-on, not textbook classes, to get the best results. q Tim Kopp is a technical applications specialist for Greenlee - A Textron Company. He can be reached at 800-435-0786, ext. 2333.