Challenges in Transformer Protection Testing

Scott Cooper Cover Story, Winter 2020 Cover Story

While the basic premise of transformer differential protection is straightforward, numerous features are employed in modern relay algorithms to compensate for challenges presented by the transformer differential application. As a result, developing appropriate test quantities and properly quantifying results can be challenging with traditional functional differential testing. Challenges in Traditional Functional Testing A traditional functional test assures that all measurements …

Partial Discharge Tests for Medium-Voltage Power Cable Systems

Dr. Jim (Jun) Guo and Zhong Zheng Cover Story, Fall 2020 Cover Story

Medium-voltage (MV) power cables are the backbone of the power distribution systems developed over two hundred years. Currently, 2.3 million miles of MV cables are installed in the USA, most with extruded insulation. Diagnostic testing technologies can differentiate MV cables by their operational condition and aging process prior to faults, thereby providing guidance for proactive maintenance and asset management. This …

Troubleshooting a Circuit Breaker

Steve Skinner Cover Story, Spring 2020 Cover Story

Circuit breakers are like the offensive line on a football team. Unless you have some knowledge of the game, you know they are there, but you have very little idea of what they do, how they do it, or why they do it. Circuit breakers are electromechanical devices required to control high-voltage (HV) electrical power networks. Circuit breakers switch circuits …

Using Communications to Monitor Power Distribution Systems

Ryan McClarnon Cover Story, Winter 2019 Cover Story

An increasing number of facilities are exploring and appreciating the communications capabilities of electrical power equipment. Modern electrical system protection and metering devices measure and calculate a significant amount of digital data, and most of this data can be retrieved via communications. Due to the availability of these devices and data, systems can monitor multiple devices in a system-wide manner …

Unlocking the Mysteries of Narrow Band DFR

Robert Breazeal Cover Story, Fall 2019 Cover Story

Southern California Edison (SCE) began using primary to secondary winding (CHL) narrow band dielectric frequency response (NBDFR) measurements for condition assessment of used distribution class transformers in 2015; 1800 units are evaluated annually. NBDFR is a series of insulation power factor measurements taken from 1–400 hertz, usually at a low voltage. The data derived from the series of CHL measurements …

High-Voltage Arc Flash Assessment and Applications, Part 1

Albert Marroquin, Abdur Rehman, and Ali Madani Cover Story, Summer 2019 Cover Story

Protecting utility workers and other working personnel who are exposed to line-to-line voltages above 15kV at live electricity installations is critical. For this reason and to ensure compliance with OSHA regulations, arc flash hazards must be evaluated and studied for every facility with an electrical installation. An arc flash produces extremely high temperatures, intense heat flux and radiation, high sound …

Circuit Breaker and Transducer: Where Do I Connect?

Robert Foster Cover Story, Spring 2019 Cover Story

Many types of equipment in the electrical transmission and distribution network perform a specific and necessary operation, and the circuit breaker is no exception, as it serves to protect the substation’s valuable assets. The circuit breaker — defined as a mechanical switching device — is unique: At one time, it must function as a nearly perfect conductor; at another time, …