How Multi-Function Numerical Protection Relays Use Symmetrical Components

Steve Turner Columns, Relay Column, Summer 2019 Columns

Multi-function protection relays calculate and use symmetrical components to enhance their performance during system faults. This can be illustrated in two specific examples: (1) zero-sequence current elimination for transformer differential protection and (2) negative-sequence current detection to inhibit out-of-step blocking. Zigzag Transformer Inside Transformer Differential Zone A shunt-connected zigzag transformer provides a zero-sequence current sink for ungrounded systems such as …

Arc Rated Clothing and Electrical Hazard Footwear

Paul Chamberlain Columns, Safety Corner, Summer 2019 Columns

Everyone wears clothes, at least when out in public. However, not everyone needs to wear clothes specially designed and tested to protect them from hazards they could find in their workplace. If your employees work on or near electric power, generation, transmission, and distribution equipment, specialized clothing is necessary for certain tasks.  OSHA 29 CFR 1910.269 states that employers must …

Using NFPA 70E to Stay Alive

James R. White Columns, Summer 2019 Columns, Tech Quiz

This month’s Tech Quiz takes a bit different look at NFPA 70E requirements. What is involved in electrical testing? As with most things, it’s not as simple as it may seem. 1. If you are a crew leader, what is the first thing you would do to test a transformer? a. De-energize it b. Isolate it by lockout/tagout (LOTO) c. …

10 Design Features for Electrical Safety

Jeffrey R. Jowett Columns, Summer 2019 Columns, Tech Tips

The National Fire Protection Association (NFPA®) revised its NFPA 70E, Standard for Electrical Safety in the Workplace in 2018 “to assist OSHA in preparing an electrical safety standard that would serve OSHA’s needs and that could be expeditiously promulgated through the provisions of…the Occupational Safety and Health Act.” Responsible electrical test instrumentation manufacturers accept 70E as a valuable guideline as …

A Guide to NFPA 70E

Ron Widup and James (Jim) R. White Columns, NFPA 70E and NETA, Summer 2019 Columns

Many companies and people rely on NFPA 70E to guide them as they develop and implement electrical safe work practices. They look at a line or possibly a paragraph or two and believe they have the gist of the issue. Maybe, but they often misinterpret what they read or implement it incorrectly. Unfortunately, there’s a plethora of misleading or incorrect …