Digitrip OPTIM Long Time Setting
Digitrip OPTIM Long Time Setting
(OP)
I am working on a coordination study, and I am having trouble understanding the TCC for Digitrip OPTIM 510 with 480V, 2000A frame and plug. The issue is that the TCC's X-axis is in multiples of long time pickup setting, but the curve starts at a value greater than 1—shouldn't be at 1. Note 7 in the TCC documents states that the longtime delay nominally occurs at 116% of the Long time pick setting. I am concern that if I have a 2000A plug, I cannot protect it with a long time setting of 1 because it will actually pick up 2320A. Is this the correct setting, or should I choose a lesser setting? I have attached the Manufacture's TCC curve






RE: Digitrip OPTIM Long Time Setting
This will depend on what you are trying to protect and what codes you have to comply with.
David Castor
www.cvoes.com
RE: Digitrip OPTIM Long Time Setting
Breaker trip units have wide tolerances as seen in their curve width. It can trip at any current within that tolerance. If you want precise tripping you will need to use relays, not LV breaker trip units. "Why" is a different story.
Rafiq Bulsara
http://www.srengineersct.com
RE: Digitrip OPTIM Long Time Setting
RE: Digitrip OPTIM Long Time Setting
Rafiq Bulsara
http://www.srengineersct.com
RE: Digitrip OPTIM Long Time Setting
RE: Digitrip OPTIM Long Time Setting
The tolerance is true for any other type of protective device using or emulating thermal overload, which a digital trip unit for breaker does.
A 2000A bus will not start to melt at 2300A. Thermal protection is not an exact science. But history of acceptable practices is the proof.
You may also want to compare your TCC with that of a 2000A Class L fuse and draw conclusions.
Rafiq Bulsara
http://www.srengineersct.com
RE: Digitrip OPTIM Long Time Setting
Rafiq Bulsara
http://www.srengineersct.com
RE: Digitrip OPTIM Long Time Setting