Measurement and Test Instrument Selection Promotes Safer Jobs

Safety is always a concern for electrical contractors-especially considering the statistics. These statistics indicate that, of the 1,000 construction workers that are killed on the job each year, nearly one-tenth are electricians. Of those 98 needless deaths, half are due to electrocution. 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. Those standards are issued by Underwriters Laboratory (UL), Canadian UL (cUL), the German product certification organization (GS/TUV), and the International Electrotechnical Commission (IEC). These agencies work hard to keep their standards up-to-date. For example, the IEC currently has a proposed Category IV standard awaiting approval that will cover the highest and most dangerous level of transient overvoltage contractors are likely to encounter in working with utility service to a facility. Without safe and accurate electrical measurement and test equipment, contractors won't be able to comply with the proposed Category IV standard. What you should know about IEC Category ratings While IEC Category IV standards may be revised before being formally adopted, some manufacturers of electrical measurement and test equipment have tested instruments to the proposed IEC Category IV standard. This ensures the highest level of testing currently available for the end-user. In addition to the proposed Category IV standard, the IEC has previously established standards (in IEC 1010-1) for Categories I, II, and III. These standards are the basis for such national standards as ANSI.ISA-S82.01-94 and UL 3111-1 in the United States, CAN C22.2 No.1010.1-92 in Canada, and other countries that adopt the IEC standards. They're applicable to all devices or facilities using power, residential, commercial, and industrial electrical measurement and test equipment. The IEC Category standards specify protection from currents at levels well above a system's rated capacity. Without this additional protection, transient overvoltages, which are becoming increasingly common, can lead to equipment failure and serious injury or death. Minimizing such risks requires that everyone working in electrical environments has safety equipment as required. They need properly rated gloves, eye protection, and electrical measurement test instruments that provide appropriate protection. Having the correct electrical testing and measurement instruments and using the correct procedures can improve job safety. To do this, a quick review of the four IEC category ratings is in order. § Category I is the signal level for telecommunications, electronic equipment, and low-energy equipment with transient-limiting protection. The peak impulse transient range is from 600 to 4,000 volts with a 30-ohm source. § Category II is the local level for fixed or nonfixed powered devices-everything from lighting to appliances to office equipment. Also, all outlets at more than 10m (30 feet) from Category III sources and all outlets at more that 20m (60 feet) from Category IV sources. The peak impulse transient range is from 600 to 6,000 volts with a 12-ohm source. § Category III is the distribution level-fixed primary feeders or branch circuits. These circuits are usually separated from Category IV (whether utility service or other high-voltage source) by a minimum of one level of transformer isolation; for example, feeders and short branch circuits, distribution branch panels and heavy appliance outlets with "short" connections to service entrance. The peak impulse transient range is from 600 to 8,000 volts with a 2-ohm source. § Category IV is the primary supply level. It will cover the highest and most dangerous level of transient overvoltage you are likely to encounter-in utility service to a facility both outside and at the service entrance, as well as the service drop from the pole to the building, the overhead line to a detached building, and the underground line to a well pump. The peak impulse transient range is from 600 to 12,000 volts with a less than 1-ohm source. Latest UL Standards To further increase the critical importance of electrical measurement and test equipment, Underwriters Laboratory Incorporated (UL) has issued two recent safety standards specifically for electrical measurement and test equipment instruments. UL Standard 3111-1 is Part One of the general requirements for electrical measuring and test equipment, and UL Standard 3111-2-032 is for hand-held current clamps for electrical measurement and test equipment. UL Standard 3111-1 specifies general safety requirements for electrical equipment intended for professional use, industrial process and educational use, including equipment and computing devices for measurement and test, control, laboratory use, and accessories intended for use with the above (e.g., sample handling equipment). Part One of the standards applies to the equipment defined for electrical measurement and test equipment when used under certain environmental conditions as defined in UL 3111-1 Section 1.4. Let's look at just the electrical measurement and test equipment section. Electrical measurement and test equipment is equipment that by electrical means measures, indicates, or records one or more electrical or non-electrical quantities and also includes non-measuring equipment such as signal generators, measurement standards, power supplies, transducers, transmitters, etc. This Part One of the standard does not cover reliable function, performance or other properties of the equipment; servicing (repair); or protection of servicing (repair) personnel. It should be noted that servicing personnel are expected to be reasonably careful in dealing with obvious hazards, but the design should protect against mishap by the use of warning labels, shields for hazardous voltage terminals, segregation of low-voltage circuits from hazardous voltages, etc. More importantly, servicing personnel should be trained for unexpected hazards. UL Standard 3111-2-032 for safety in hand-held current clamps for electrical measurement and test equipment was recently adopted by the UL standards committee. The international standard applies to hand-held and hand-manipulated current clamps. These current clamps are for use in the measurement of current without interruption of the current paths of the circuit in which it is measured. They may be stand-alone current clamps, which are themselves within the scope of Part One, or accessories to other equipment within the scope of Part One. This standard does not apply to current transformers or current transducers intended for fixed installations. New technology and safety concerns Noncontact measurement is the method by which voltage, temperature, or other variables are measured without actually contacting the current-carrying conductor. This technique is quickly becoming a reality in the electrical measurement and test equipment field. As the technology and development of these instruments continues to grow, so too does the need for proper safety requirements and education. Previous UL standards, such as UL-1244, have not incorporated overvoltage category ratings and testing requirements. Equipment designed to the previous standards may not meet the requirements of the current standard at the same operating voltage. In these cases, the maximum voltage ratings are reduced, sometimes significantly. Some manufacturers have assigned overvoltage category ratings for their products. While there is no requirement in the IEC for this type of independent verification, end-users are likely to have greater confidence in the protection provided by their test equipment when they know it has been evaluated by an independent agency. Education is a critical component that should not be overlooked. Organizations like UL and the National Electrical Contractors Association offer seminars or software on safety that can assist in keeping the end-user abreast of safety issues. Remember: Wherever you need overvoltage protection, look for independent certification UL, cUL or GS/TUV, and choose the category appropriate to the type of work you expect to accomplish. According to statistics, electrician fatalities rank 10th among all private industry occupations. To avoid becoming a statistic, become more safety minded. GREEN is electrical construction and maintenance market manager for Greenlee Textron. He can be e-mailed at

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