Recently, I challenged a proprietary AI platform to solve a simple protection problem: Use a CO-9 overcurrent relay to provide backup protection for a 150 MVA transformer; the high-side voltage is 230 kV. Plot the characteristic of the CO-9 versus the transformer damage curve. This was not an especially difficult problem to solve. I wanted to see if it would …
Voltage dividers are simple devices consisting of series circuits that produce two or more lower voltages from a single source voltage via resistances. This is possible because of this mathematical fact: Given a series circuit with multiple resistances, the sum of the absolute values of all voltage drops across each resistance will equal the source voltage. This fact is illustrated …
OK, let’s be honest. When you pull NFPA 70E off the shelf, it’s not exactly something you look forward to reading for entertainment. Yes, it matters. (It matters a lot!) But it’s not built to grab your attention or stick with you. And that’s not a knock on the standard. Consensus standards like NFPA 70E serve a clear purpose: to …
This Summer edition of NETA World arrives at a pivotal moment for our industry. Demand for electrical testing and commissioning has never been higher, expectations have never been greater, and the pace of change continues to accelerate. Across every segment, from data centers to grid modernization, we are being asked to do more, move faster, and deliver with absolute precision. …
Substation design typically calls for two to six inches of aggregate (crushed rock) as a top layer upon completion of construction. This layer serves several purposes, including improved vehicle access, reduced erosion, and suppression of vegetation. Another significant function of this layer is to provide personnel safety by increasing the allowed (maximum permissible) touch and step potential values versus native …
Electrical equipment is selected by a design engineer for a specific purpose. This includes operating within the manufacturer’s specifications, as well as how it functions within the system. For newly installed equipment, it is important for NETA Certified Technicians to critically verify that all aspects of the equipment work as intended to ensure proper and reliable operation of the electrical …
Breaker testing and maintenance can expose personnel to many types of hazards. Mitigating them can be achieved in various ways. First, it must be verified that the personnel are qualified to perform the required tasks. The person doing the work must recognize and understand the hazards that may be encountered while performing the tasks. To better understand the many hazards …
Typically, multi-function numerical generator protection relays are now used to provide out-of-step tripping (OST) for large unit-connected generators. However, some users prefer to maintain older existing infrastructure, such as electromechanical relays. 78 OST protection must meet PRC-026-2 Criterion A of Attachment B requirements as follows: PRC-026 Criterion A of Attachment B indicates that a 78 impedance-based out-of-step protection function should …
If you’ve worked on transformers in renewable energy circuits, as I have for the past six months, you’ve likely seen many—perhaps most—equipped with electrostatic shields, grounded copper or aluminum sheets wedged between the high- and low-side windings. The existence of these shields inside transformers is normally (but not always) readily identifiable via the unit data plates (Figure 1). Some affirm …
We work around electricity every day. We are exposed to hazards every day. But what’s the most dangerous task YOU do every day? DANGEROUS TASKS The Starting Point: Turn It Off! My guess is you treat switching operations like surgery—plan the task, determine the proper shutdown sequence, see which loads are affected, check the one-line diagrams, verify the labels, double-check …