Best Practices for Ratio Verification of Power Transformer CTs

Thomas Bischof and Fabiana Cirino, OMICRON electronics Corp.Features, Summer 2024 Features

Current transformers (CTs) are essential for reliable and safe operation of electrical power networks. They function as the link between the primary system, which includes the assets directly involved in the energy flow, and the secondary system consisting of the protection, control, and metering devices. CTs do this by transforming high primary currents into the more measurable quantities used by …

Electrical Signature Analysis of Oil- and Dry-Type Transformers

Howard W. Penrose, PhD, MotorDoc LLCCover Story, Summer 2024 Cover Story

Periodic and continuous electrical signature analysis can be used to evaluate the general condition and power quality that affects oil- and dry-type transformers. This article discusses how conditions such as loose connections, resonance, component looseness, and failing electrical components can be detected. Case studies from several applications including wind power, solar, and industrial dry- and oil-type transformers are presented. ELECTRICAL …

Advancements in Industry: Shorted-Winding Technique for Single-Phase Exciting Current and Loss Testing

Mike Anderson, Doble Engineering CompanyCorporate Alliance Corner, Summer 2024 Corporate Alliance Corner

The conventional exciting current and loss test is an open-circuit measurement of current and loss, typically performed from the high-voltage side of the transformer, using low voltage (up to 10 kV), single-phase, power frequency (50/60 Hz) excitation. For this test, the well-known approach to data analysis, first introduced in 1968, relies on comparison and evaluation of the per-phase readings against …

Ground-Grid Integrity Revisited

Jeffrey R. Jowett, MeggerColumns, Summer 2024 Columns, Tech Tips

Utility substations are undergirded by large — sometimes massive — grounding grids. These are made up of electrodes, much like the familiar ground rod, but with extended responsibilities. The grid must provide a means to carry electrical currents into the earth under normal and fault conditions without exceeding operating and equipment limits. The grid must also assure the safety of …

Transformers

Morgan Gieni, Magna IV EngineeringColumns, Tech Quiz

Transformers are critical power system components, allowing transmission and distribution of power throughout the industry. As NETA Certified Technicians, we should be familiar with the various sizes, configurations, and types of transformers.  1. Which type of transformer is usually connected to a utility generator?a. Step-down transformerb. Isolation transformerc. Step-up transformer d. Three winding transformer 2. What does the DY1 designation on …

Power Transformer Hazard Awareness

Paul Chamberlain, Asplundh Engineering Services, LLCColumns, Safety Corner, Summer 2024 Columns

Performing condition analysis or maintenance on a power transformer and ancillary devices is a potentially hazardous task that requires well-trained test personnel to identify and mitigate risks. Products and equipment that are designed to test and diagnose equipment while in operation, such as infrared cameras, partial-discharge detection equipment, and online oil analysis can be used to determine a power transformer’s …

Optimizing 50/27 Inadvertent Energization Protection

Steve Turner, Arizona Public Service CompanyColumns, Relay Column, Summer 2024 Columns

The 50/27 inadvertent energization protection function (Figure 1) is an overcurrent function supervised by generator terminal bus voltage derived from system-side voltage transformers (VTs). Inadvertent or accidental energizing of off-line generators has occurred frequently enough to warrant using dedicated protection logic to detect this condition. Operating errors, breaker flashovers, control circuit malfunctions, or a combination of these causes have resulted …

Medium-Voltage Cable Testing and the Importance of Processes

Mose Ramieh, CBS Field ServicesColumns, In the Field, Summer 2024 Columns

In a previous article, I discussed the challenges and the importance of proper cable installation. Here, we turn our attention to the challenges of obtaining accurate test results. These best practices and processes come with a field technician’s ability to be efficient and confident in their test results. I have been around the industry long enough to be present for …

NETA Engages Approved Military Organizations

NETA World StaffNETA News, Spring 2024 NETA News

The NETA Approved Military Organization (NAMO) classification was born out of the recognition that the United States military is a strong proponent of the NETA philosophy and shares the ideology that adhering to voluntary standards, certification of technicians, and continuing education is paramount to the successful completion of their mission. Military members can obtain certification through NETA’s unique NAMO Program. …

New NETA Electrical Power Innovations Conference

NETA World StaffNETA News, Spring 2024 NETA News

SAVE THE DATE!October 14–15, 2024 This industry-leading educational conference will bring industry experts together to discuss which emerging technology will shape tomorrow’s electrical power industry. Join your colleagues! For a gathering of thought leaders and innovators, equipment manufacturers, engineers, utilities, investment groups, and service providers who are defining the next generation of electrical power advancements, innovations, reliability and safety. INTERESTED IN …