Recent content by YIGO

If the meter is the only device on CT secondary, the CT secondary will be open. Thanks Yigo

I found what I was looking for. The pick up is 74.75 V at 115 V. For 120 V, PU is 62.29%. Thanks to you all. Yigo

I was given a coil that picks at 65% of rated voltage which is 115 V. If I want to perform calculation on 120 V basis, how would I correct the pick up voltage. Thanks Yigo

I am trying to find out if there are tests data that show the impact of grounding conductors as determined per NEC Table 250.122 on zero sequence impedances of cables. Thanks Yigo

In my understanding, TCC are given for RMS values. In a short circuit, RMS current will be the result for both the symmetrical AC current and the DC current.

All, I am trying to use Eaton breakers type HFD in a 125 VDC system ungrounded. The breakers have an Interrupting Capacity Rating listed for 250 VDC but not for 125 VDC. I would like to know potential risks for the application. Thanks Yigo.

All, Breaker TCC and damage curves are plotted for one line diagram section that has a transformer 480V Delta/208V Wye-Grounded, a breaker at the transformer primary and cables. The plot time axis current is referenced to 208V,and short circuit current for 3 phase fault and phase to ground have...

Thanks DTR2011. With the explanation you provided, I am no longer confused. Thanks to you all. Yigo

Thanks ScottyUk. That's also my understanding of >>. However the left hand numbers are equal to the right hand ones per my enclosed markup. That's what confused me.

I was reviewing IEEE C37.91 when I found the enclosed coordination steps. I am wondering what is the meaning of the symbol >>? Is this a typo? Thanks for your consideration. Yigo...

Thank you for your responses. You are all saying the same thing. Moving the pick up 15% to the left or right would cause the curve to shift to the left or right. From my previous post, the right current is (I-85 x 0.85/I-trip). Thanks again. Yigo

Jraef, To make sure I understand you, please let me state the issue in a different way. I have TCC curves defined as time = f(I/I-trip). During a test,the OL relay is set at 100%, the relay trips for a current named I-100. Using TCC curves, the time is the point where TCC intersects the current...

All, Please explain to me the impact of the thermal overload relay current setting range. I have a relay with the following current settings: 85%, 100%, 115%. If at 100% setting, the relay trip at t100, what would be the trip time at 85% by just adjusting the current dial. Likewise, what would...

All, I have a 208/120V, 3Ph, 4W lighting panel. I want to list a 1Ph 208V, 1000W connected between phases 1 and 2. I think the right way is to list 1000w for each phase 1 and 2. Please advise if this is right. Thanks for your input. Yigo

I just want to share what I know about GSU transformer sizing. One case I dealt with, the sizing was based on the generator rating , auxiliary loads, and estimated losses. Power flows scenarios are analyzed with different PFs (e.g. 0.8, -0.8,1). GSU size is selected based on worst scenario...