Electrical faults cause enormous damage due to fires and loss of equipment. But of far greater importance is the danger to human life through electrocution. Ground faults in particular pose the risk of death because a human is generally at ground potential, thereby providing an alternate current path. It takes only about 5 mA to cause a shock, and as …
This issue of NETA World covers troubleshooting. A big part of that is being able to interpret a schematic, and some of the most difficult are those for circuit breakers (unless you work in the circuit breaker shop, I suppose). Give these questions a try. Here’s a big call-out to retired Instructor Craig Nelson, who got tired of my hand …
As I drove toward the office one morning, it occurred to me that we were due for an emergency call. I was about to text a colleague (hands-free voice recognition) when the phone rang. Soon I rerouted the navigation system and I was off to the races! Along the way, I notified the office and called a technician to assist …
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 …
Differential relays operate on three or more sets of three-phase current inputs. These relays can be older electromechanical relays with current transformers (CTs) connected in parallel to the three-phase current inputs or newer numerical relays that have more than two sets of three-phase current inputs. Note that it is poor practice to connect CTs in parallel to a single three-phase …
The NFPA Committee met in Boston in September. The meeting began with confirmation that the 70B maintenance guide would be rewritten into a maintenance standard. There had been previous discussion regarding whether to make it a recommended practice, using the word “should” in the verbiage, or to make it a standard, using the word “shall.” There are differences between a recommended practice …
As we leave winter and advance into spring, our industry is preparing for the spring outage season. This time of year, the return of daylight leads to longer work days and more deadlines to meet the expectations of our customers. Be sure to follow the safety policies of your company as well as those required by the facility where the …
This issue’s theme brings up a question frequently asked by NETA technicians: “When does troubleshooting end and when does repair begin?” This question is often paired with “What does 70E say about troubleshooting and repair?” We hope to make things clear for everyone in the field. To begin, look at the definition of “working on” (energized electrical conductors and circuit …
To explain VLF tan delta, we must first explain the reason it was developed and how the concept and equipment used to perform this test came about. Tan delta is still a form of high-potential (hipot) testing but utilizes the advantages of both AC and DC testing while eliminating many, but not all, of the disadvantages. The very-low-frequency (VLF) portion …
While the chemistry behind dissolved gas analysis (DGA) is complex and important for industry chemists to understand, the typical DGA review need not be as complex. Thermal or hot metal gasses are commonly known in DGA, and they are widely understood by industry experts, chemists, and many asset owners. The carbon oxide gasses — carbon dioxide and carbon monoxide — …