Recent content by mparenteau

Programs like SKM, ETAP, etc.

That information certainly helps to model your capability curve. Mike

Mutual coupling... Mike

Maybe this will help: IEEE Std C62.22TM-2009 Mike PS Found this paper as well: https://www.sciencedirect.com/science/article/pii/S0378779621005642#:~:text=Line%20surge%20arresters%20are%20installed,to%20a%20poor%20soil%20conductivity.

Assuming you have a MV or HV circuit breaker w/ no "brains", the relay is the brains. So, there will be a slight delay between relay sensing, and the relay issuing a trip command. So it would actually be longer than 2 sec, unless you included the opening time of the breaker. Mike

Who knows? Did you look at how the fuse performs at 12x @ .1 sec and 20x @ .01 sec (I have seen 25x @ .01 sec as well)? Mike

An ID run is a procedure whereby the VFD "learns" the motor(s) characteristics via an algorithm. I'll defer to jraef on the rest... Mike

There are usually interlocks between a VFD, load side disconnect and the VFD itself (I've never used a starter on the load side of a VFD, but have installed disconnects on the load side of a VFD for local isolation). Drives don't like switching actions on the load side of their terminals while a...

Solid state OLs will give you some flexibility on setting based on FLA. Some have phase loss settings for motor protection as well. Mike

Thanks to dpc for clarifying. Yes...400A resistor on a 480V system is no bueno. My suggestion is for a MV system.

Consider the withstand time of the resistor. A 400A resistor is pretty common, having a 10 second withstand. Extended time ratings means more $$$. Mike

I use this: https://www.mitchellinstrument.com/hd-electric-hva-2000-high-voltage-digital-ammeter-up-to-500kv.html?gad_source=1&gclid=EAIaIQobChMI5ZvQ8uesigMVuiytBh3zcxGFEAQYASABEgJz0fD_BwE Mike

I would just add to dpc's commentary: close-coupled switchgear, i.e. perhaps a power style transformer that is a few feet away from a switchgear lineup, will likely have a SLG fault current (3*Io) greater than the 3PH fault current. As dpc addresses above, this is cause for concern. Mike

Right or wrong...I used the following: <5% VTHD <33% ITHD Anything above those #'s, I would look into filtering if operational/equipment issues were noticed, etc. I hadn't experienced any operational down-sides to those #'s, but your mileage may vary depending on your installation. Mike

If I'm not mistaken, if a UPS fails, it will want to transfer from the inverter/rectifier to its static bypass. Maybe this is why the time delay on your UV release didn't work. Mike