In a perfect world yesThat is typically specified by the design engineer.
Those tools would be the manufacturer's Time Current Curves for that breaker and any other breakers or fuses it needs to coordinate with. Many design professionals use the curves found in software packages, but coordination can be done manually using printed curves.What I am asking is what tools does the design engineer use? I know the connections and all other pertinent information.
I have the curves for the breaker. I have also reached out to the manufacturer.Those tools would be the manufacturer's Time Current Curves for that breaker and any other breakers or fuses it needs to coordinate with. Many design professionals use the curves found in software packages, but coordination can be done manually using printed curves.
Most importantly, someone also needs to make the decision on what level of selective coordination is required and at what current levels.
It depends where in the system this breaker is. Going with what Ron said, one of my text books was called The Art and Science of Protective Relaying.I have the curves for the breaker. I have also reached out to the manufacturer.
What is the thought process regarding how to set? I know all the connected loads, FLA, etc... I also know all the wire sizes, and lengths.
There has to be a rational behind where to set the times. Like augie47 wrote, my experience is to set until it quits tripping. I have also reached out to the specific designers and others I have worked with in the past. There does not seem to be a solid method.
With two protective devices in series, without other information, I would make their setting as similar as I could.in the swgr there is a 100a breaker that feeds this panel.
You would normally do a discrimination study using electrical software to see if the curves are overlapping. If they are overlapping it means that the upstream breaker may trip before the downstream one. Also normally thermomagentic breakers can only be wound down to 0.8 of their nominal rating and electronic to 0.4 so you might have some problems getting to the current levels you are looking for here. At 65kA all the breakers will need to be MCCBs so the switchboard will be very heavy duty for a 250A board. Check out this article here: Discrimination StudiesI have an ETU 350 LSI, 100A breaker that has four dial settings. It is located in an enclosure and serves as the panel disconnect as well. Is there a definitive guide as to how to set these? There must be an accredited way to set these dials.
thank you, this is a good read.You would normally do a discrimination study using electrical software to see if the curves are overlapping. If they are overlapping it means that the upstream breaker may trip before the downstream one. Also normally thermomagentic breakers can only be wound down to 0.8 of their nominal rating and electronic to 0.4 so you might have some problems getting to the current levels you are looking for here. At 65kA all the breakers will need to be MCCBs so the switchboard will be very heavy duty for a 250A board. Check out this article here: Discrimination Studies
Steve