Tutorial: Hazard and risk categories for electrical workplace safety

As the electrical work environment becomes more hazardous, the need for arc flash, electrical transient, and electrical shock protection increases. Standards are cited and advice follows for ways to lower risk.

04/19/2011


Fluke iFlex can lower risk by increasing distance to the hazard.For U.S. electrical workplace safety, the key standard is National Fire Protection Association (NFPA) 70E, Standard for Electrical Safety in the Workplace. The U.S. Occupational Safety and Health Administration (OSHA) refers to NFPA 70E for electrical safety. The preferred way to work on hazardous electrical circuits is with the power off. Equipment that could be turned on must be locked out and tagged. But some tests, such as the current tests that clamp meters perform, aren’t possible unless circuits are live.

As the electrical work environment becomes more hazardous, the need for arc flash, electrical transient, and electrical shock protection increases. For situations when a location-specific arc flash hazard analysis is not available, NFPA 70E defines the arc flash protection boundary for equipment with voltage levels between 50 V and 600 V at four feet. (See NFPA 70E section 130.3 (A)(1) for full details.) The standard names a wide variety of electrical maintenance tasks and assigns each a hazard/risk category of 0 to 4. The standard also details the kind of personal protective equipment (PPE) that must be worn when working in the various hazard/risk categories.  

The NFPA standard categorizes test equipment as PPE and requires that test equipment be rated and designed for the circuits and environments where it will be used. To clarify what this means, the 2009 Edition of NFPA 70E cites American National Standards Institute (ANSI)/ISA- 61010-1 (82.02.01)/UL 61010-1, the standard first established as International Electrotechnical Commission (IEC) 61010.

These measurement categories (CAT) listed in the standards cover systems of 1000 volts or less, including 480-volt and 600-volt, three-phase circuits. They define the danger of transient voltage spikes and electrical arc flash and differentiate the severity by location, voltage level, and potential for harm. ANSI, the Canadian Standards Association (CSA) and IEC define four measurement categories.

• CAT IV is applicable to test and measuring circuits connected at the source of  the  building’s low-voltage MAINS installation.

• CAT III is applicable to test and measuring circuits connected to the distribution part of the building’s low-voltage MAINS installation.

• CAT II is applicable to test and measuring circuits connected directly to utilization points (socket outlets and similar points) of the low-voltage MAINS installation.

• CAT I defines non-CAT rated products that are not intended to be directly connected to the MAINS supply.

Some installed equipment may include multiple categories. A motor drive panel, for example, may be CAT III on the 480-volt power side, and CAT I on the control side.

A higher CAT number refers to an electrical environment with higher power available and the potential for higher-energy transients. A test tool designed to a CAT III standard can resist higher energy transients than one designed to CAT II standards. Within a category, a higher voltage rating denotes a higher transient withstand rating. For instance, a CAT III-1000 V test tool has superior protection compared to a CAT III-600 V rated tool.

Product designs can lower risk

Fluke iFlex clamp meter familyIndustrial and commercial electricians often work in 480 volt electrical environments that pack enormous transient surge potential—and pose a significant threat of arc flash and shock. New Fluke test tools exceed international standards for safe use in such environments, the company said. Some tools enable technicians who must test live circuits to do their jobs at a distance from electrically hazardous installations.

For example, new Fluke 381, 376, 375 and 374 current clamps and Fluke iFlex current probes are rated for use in measurement category IV environments (CAT IV 600V, CAT III 1000 V) as defined by safety standards in the U.S., Canada and Europe.  The detachable display of the new Fluke 381 Clamp Meter enables technicians to see measurements remotely—up to 33 feet from the equipment being tested. Those conducting the test can see readings when the test circuit is enclosed in an equipment cabinet.

The new Fluke ScopeMeter 190 Series II handheld portable oscilloscopes are the first four-channel scopes designed for harsh industrial environments. They are rated as dust and drip-proof and are said to be the first hand held oscilloscopes safety rated for CAT III 1000 V / CAT IV 600 V environments.

- Hazard / risk categories information provided by Fluke. See also

Product Exclusive: Advanced clamp meter family from Fluke Corp.
http://www.fluke.com/safety

www.fluke.com/safety 

www.fluke.com/ReadyForAnything.

www.iec.ch

For more on machine safety, see Cover story: Machine Safety Integration.

See the Plant Safety and Security Channel at http://www.controleng.com/channels/plant-safety-and-security.html.

- Edited by Mark T. Hoske, CFE Media, Control Engineering, www.controleng.com



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Learn how to create value with re-use; gain productivity with lean automation and connectivity, and optimize panel design and construction.
Go deep: Automation tackles offshore oil challenges; Ethernet advice; Wireless robotics; Product exclusives; Digital edition exclusives
Lost in the gray scale? How to get effective HMIs; Best practices: Integrate old and new wireless systems; Smart software, networks; Service provider certifications
Fixing PID: Part 2: Tweaking controller strategy; Machine safety networks; Salary survey and career advice; Smart I/O architecture; Product exclusives
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Look at the basics of industrial wireless technologies, wireless concepts, wireless standards, and wireless best practices with Daniel E. Capano of Diversified Technical Services Inc.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.