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Aren't all industry CTs rated up to x20 secondary current before they start loosing accuracy? Going by this typical 5A secondary CT has current of 100A (5Ax20). So solution would be simple V=IR=100x1.1=110V. The fact that this CT is industry standard is kind of given by 8000A/400A=20 in the...

Been working on this problem and I got the answer correct the first time, but mainly due to rather large difference between answers. I used a bit different approach, actually two and was wondering if it's just plain luck or correct thinking: 1) Find voltage drop in line Vd = IaA/sqrt(3) x Z =...

To answer my own question. IEEE 141 states that values below 1.5 of pick up setting cannot be accurately predicted and are not plotted as a result, but can be requested from individual manufacturers. Looks like I'll have to expand my reference materials to understand each question in details.

It does. I am a young engineer and haven't had much exposure to Time-Current Curves. My assumption was that relay would not be able to pick up anything once the curve ends. Did not realize that I could "extend" them all the way to top. My assumption was that area on left was the "operating...

Hi, It's a problem with time dial setting on 50/51 relay. The problem states that a minimum pick up for 50/51 relay is 420A. Looking at the graph, curves originate at roughly 1.5 of pick-up setting. Shouldn't 1.5 (on x axis) correspond to 420 A, since that's where curves originate, hence lowest...