Power Factoring Medium-Voltage Breakers

Rick Youngblood Features, Summer 2021 Features

A test technician’s toolbox can never have too many options. The more ways we can detect or confirm a problem in a piece of equipment, the better. Early in my career at Duke Energy, I was never satisfied with just one test result indicating a problem, and I often second-guessed myself as to whether the equipment was bad or if …

Primary Injection Testing on Low-Voltage Circuit Breakers

Sanket Bolar Features, Spring 2021 Features

Circuit breakers used in low-voltage applications include air circuit breakers, insulated-case and molded-case circuit breakers, and miniature circuit breakers. Air circuit breakers or low-voltage power circuit breakers typically function as the incoming device on a low-voltage switchboard. In the event of an overload condition or short circuit, current sensors in low-voltage power circuit breakers measure high currents and send the …

Low-Voltage Air Circuit Breakers—A Maintenance Must!

Kerry Heid Features, Spring 2021 Features

Low-voltage circuit breakers are predominant in virtually every electrical power system. A 2008 NETA survey and associated IEEE paper showed that 22% of these breakers did not follow their time-current characteristics, and 10.5% did not operate at all when service-aged maintenance was undertaken. The majority of failures were mechanical in nature; this indicates regular maintenance must be a priority. Low-voltage …

Investigating an Electromechanical Differential Relay Misoperation

Alex Rangel Features, Winter 2020 Features

Transformer differential protection based on ANSI 87 is one of the most common protection methods for large power transformers due to its outstanding speed and accuracy. However, given the complexity of this method when applied on delta-wye grounded transformers, mistakes made during the design and/or installation phases might not be detected promptly and can eventually cause an undesired operation — …

Testing Techniques for Protection-Class Current Transformers

Dinesh Chhajer and Sughosh Kuber Features, Winter 2020 Features

Relaying current transformers serve as critical components in the design of a protection scheme. CT performance under fault conditions should be within its operating characteristics for a true representation of fault magnitudes and reliable operation of the protection scheme. To ensure proper installation and operation, CTs are often subjected to one or more tests performed in accordance with standards including …

Testing and Commissioning a Distribution Recloser in Grid-Tie Solar Farms

Mohit Sharma and Luis Montoya Features, Winter 2020 Features

Rapid photovoltaic (PV) penetration into the electric grid has mandated deeper operational and technical understanding of protection schemes in PV farms. An effective protection scheme ensures a grid-connected system functions reliably and securely, and testing and commissioning the entire protection scheme to prove its operational success is of paramount importance. This article presents a standard grid-tie photovoltaic farm architecture and …

Partial Discharge Secrets, Tips, and Tricks

William G. Higinbotham Fall 2020 Features, Features

Most of us started our electrical careers with fairly good knowledge about the practical aspects of our jobs. We understood voltage, current, power, resistance, etc. We mastered the more esoteric areas such as electrical fields and stress control and only revisited these topics if our day-to-day job required it. Partial discharge (PD) is one of those areas where we might …

Acceptance and Maintenance Testing Medium-Voltage Electrical Power Cables

Thomas D. Sandri Fall 2020 Features, Features

As time progresses and a cable system ages, the system’s bulk dielectric strength degrades. During this aging process, artifacts such as water trees, delamination, voids, and shield corrosion raise the local stress placed on the cable during normal operation. The exact way in which the strength of a device degrades depends upon many factors including voltage, thermal stresses, maintenance practices, …

Using VLF And PD Testing to Improve Commissioning Reliability

Javier Ruiz Fall 2020 Features, Features

Methods to check medium voltage cable integrity have evolved drastically in the last 30 to 40 years. The DC hipot test has largely been replaced by the 0.1 Hz very-low-frequency (VLF) test, and North American (IEEE) and European (IEC, CE, CIGRE) standards specify the VLF test method for solid dielectric medium-voltage cables. Throughout these years, the 0.1 Hz VLF test …

Beliefs Drive Behaviors

Daryld Ray Crow and Danny P. Liggett Features, Summer 2020 Features

The behavioral components of incidents, injuries, and fatalities must be studied and understood to change the safety culture. This element of study has been missing from the data available to assist in improving workplace safety. Often, this type of information has never been compiled and reviewed. Figure 1 shows the relationship between incidents, injuries, and fatalities. As shown in Figure …