This edition of NETA World features articles on electrical power system protection. Protection schemes covering feeder, generation, transmission, and transformers may have many similarities, but they often contain specific functions or schemes unique to that type of equipment. Be sure you check out this edition’s four feature articles: “Challenges in Transformer Protection Testing,” by Scott Cooper of OMICRON electronics “Testing …
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 …
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 …
First, let’s look at some industry-accepted definitions to establish context. Low voltage is anything below 1 kV. The common building-wiring voltages are 120, 240, 480, and 600 V. To the uninitiated, this can seem confusing and even ridiculous. Get across 600 V, and it can fry you like bacon, but in industry parlance, it is still low voltage. Put into …
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 …
Many regulatory agencies direct which documents are required to perform a company’s tasks. In some cases, federal and state requirements must be adhered to for the same task or hazard. For example, the United States Environmental Protection Agency (US EPA) and state environmental agencies, such as the Massachusetts Department of Environmental Protection (MA DEP), regulate potential environmental impacts that may …
May 2020 was a difficult month for our nation, and 2020 is certainly shaping up to be a difficult year. As essential service providers, many in our industry were called upon to maintain or continue building the nation’s infrastructure. We all understand and appreciate that hospitals, emergency services, government facilities, manufacturing, and even residences could not function without power, and …
This article demonstrates how CT saturation can adversely affect transformer differential protection and how to easily mitigate its effects via inbuilt relay functions. The solution is to provide calculations and simulation for a three-phase fault on the low side of the transformer just external to the CTs. Application The application is for a three-phase delta-wye connected transformer serving station load …
In September 2020, the newest (2021) edition of NFPA 70E, Standard for Electrical Safety in the Workplace® will be available to the industry. So how is it that such an important safety standard, put forth as a national consensus document, is reviewed, revised, and improved every three years? We’ll look at the process a little later in this article. But …
Welcome to the fall edition of NETA World. In this issue, our authors cover the various methods for performing testing on medium-voltage cables. I recommend you start with the article by Tom Sandri of Shermco Industries, which lays out the current test methods for acceptance and maintenance testing of medium-voltage cables. Next, dive into the articles on specific testing methods …