1. Describe the function of polarity marks on current transformers. 2. Transformer differential relays protecting a 50 MVA, 138 kV – 13.09 Y/7.56 kV transformer have been operating normally during the construction phase of a project. When the transformer is being brought up to full load it trips. There is no indication of a fault, as all tests on the transformer and cable …
The National Fire Protection Association (NFPA) is best known for the 70 standard, which is a consensus standard reviewed and updated every three years. The NFPA produces many additional standards covering topics such as Aircraft Rescue and Fire Fighting, Finishing Processes, and Wastewater Treatment Plants. There are three standards that pertain directly to electrical workers and equipment: • NFPA 70 …
The Tech Quiz questions for this issue concern medium-voltage power system components. FREE QUESTION! What is medium-voltage? Great question, as there are varying answers from NETA, NEMA, NFPA, and IEEE. NETA’s Standards Review Council has defined and classified medium-voltage within the NETA standards as “a class of nominal system voltages greater than 1,000 volts and less than 100,000 volts,” which …
This edition of the Tech Quiz discusses one thing we all deal with, either at home or at work: low-voltage circuit breakers. Typically, they can last for years without causing problems, but they do require some maintenance and care. Continue on to find out what’s in store for you! 1. When the topic of low-voltage circuit breakers comes up, what …
Circuit breakers come in several types of operating styles differentiated by what they use to safely extinguish an arc in a circuit, including air, air-magnetic, vacuum, and SF6. While most older circuit breakers were manufactured in the United States, mostly by companies such as Westinghouse Electric, General Electric, and Federal Pacific, today many circuit breakers are imported. Older companies merged …
NEC CMP-13 NEC CMP-13 covers Articles 700 Emergency Systems, 701 Legally Required Standby Systems, 702 Optional Standby Systems and 708 Critical Operations Power Systems (COPS). The Task Group’s sessions on October 22-21 ran five hours due to the high workload. Earlier, the Correlating Committee asked Jim Dollard (CMP-13 Vice Chair) to develop a “Safety by Design” annex with a Task …
This edition of Tech Quiz covers protective relays. Many years ago, as I was teaching a protective relay class, a student asked, “What are these things?” I replied, “Relays,” to which he answered, “No, relays are those little black plastic things that go click-click.” I made sure to call them protective relays from then on. Things in the protective relaying …
Cable testing is one of the oldest forms of testing in the industry. At first, cables were tested using DC voltages, but this was found to damage newer cable types, so additional cable testing methods were developed. This issue’s Tech Quiz takes a look at cable testing. 1. During the early years of cable testing, which two primary types of …
The semi-annual ASTM-F18 Committee Meeting on May 28, 2020, was hosted on the WebEx app. This takes the place of the April meeting that was scheduled in Boston and cancelled due to the COVID-19 crisis. There were 74 participants. F1506 Antitrust laws were read first. The first and only subject was F1506 arc-rated face masks, which are similar to a …
Everyone says they want to be safe, but when you get right down to it, some are more serious — or possibly they understand the consequences of incorrect decisions more accurately — than others. Whoever performed the repair in this photo did not have a clue what they were doing or the possible consequences of such shoddy work. Thankfully, we …