Logistics
When: 1/3/2025 @ 12:00PM Eastern
Where: YouTube LIVE
This is the first Q&A Friday of the year and I’m going to take the opportunity to address some questions that I have recently fielded including. a comment on one of my past videos. Selective coordination doesn’t have to be difficult to understand and we’re going to add some clarity.
Join me for a LIVE session on a technical topic.
Selective Coordination Tables
This video is the stimulus for questions from one of our viewers.
Glad someone else other than me is introducing these charts to engineers.
That said, the first part of the lecture implies that you cannot use TCC plots to determine misscoordination down in the .01 sec range other than charts.
(A) Plots get truncated:
As plotted the 20A and 150A breakers were coordinated for the situation shown. That is because the plot truncated the right most portion of the 20A breaker at a “desired level” for analysis. If you truncated the 20A curve at 1500A or 3000A you would have seen the same result as the charts show.
(B) Many manufacturers have tables:
I have been covering this in my courses since 2006 at which time G.E. engineers attending the course decided to start making up the coordination charts that thankfully most of the other manufacturers now provide.
(C) Engineers don’t understand curves:
The biggest problem I see is that engineers really don’t understand the equipment and what the plotted curves are telling them.
(D) TCC Plots can confuse you.
Later a TCC with a current limiting fuse is plotted downstream of a breaker. That coordination will work but that is another place where TCC plots can fool you. Just because there is what I call “white space” between the CL fuse and the breaker does not guarantee coordination between them.
(E) Charts guarantee coordination.
That is where again mfr. charts with fuses and breakers can guarantee coordination.
Selective Coordination & Transformers
When you selectively coordinate a system do you stop at the primary of a transformer an then continue separately on the secondary? If so, we need to talk.
This educational video delves into the crucial yet often overlooked concept of selective coordination in electrical systems, particularly as it applies through a transformer. Many engineers design systems with clear separation between the primary and secondary sides of a transformer, assuming coordination is limited to each side independently. However, this approach can leave gaps in reliability and safety for certain applications.
The video begins by explaining the fundamentals of selective coordination and why it is essential for ensuring that electrical faults are isolated to the smallest possible section of the system, preventing widespread outages. It highlights common misconceptions, such as treating the primary and secondary sides of a transformer as independent systems, and emphasizes the importance of viewing them as interconnected.
Using diagrams and animations, the video illustrates:
1. The principles of selective coordination through a transformer.
2. Key scenarios where secondary devices must be selectively coordinated with upstream primary devices, such as in healthcare facilities, critical infrastructure, or industrial applications.
3. Practical steps and calculations to achieve coordination across the transformer.
By the end of this session, engineers and designers will gain a deeper understanding of how to evaluate fault currents, breaker trip curves, and coordination studies to ensure a seamless and reliable system.