Relay-Fuse coordination CTI/Grading Time
Relay-Fuse coordination CTI/Grading Time
(OP)
IEEE 242-2001, p605, suggest a coordination interval of 0.12 between fuse and upstream static relay. Others, suggest similar values such as 0.10, for example, http://sie mens.sipro tec.de/dow nload_neu/ applicatio ns/SIPROTE C/english/ Appl_03_Co ordination _of_Overcu rrent_Rela is_with_Fu ses_en.pdf
I assume these are referring to the total clearing curve. Although some manufacturers, for example Siba and others, mostly present the one average curve.
I believed the fuse total clearing curve was already the maximum including all tolerances (at the stated temperature). So, I am wondering what these time intervals are accounting for, and if it is actually needed at all. Could it simply be from a previous era when the starting point was only average curves. My consideration is indoor, so cold weather is not a factor.
Does someone have some insights on this item? Thanks
I assume these are referring to the total clearing curve. Although some manufacturers, for example Siba and others, mostly present the one average curve.
I believed the fuse total clearing curve was already the maximum including all tolerances (at the stated temperature). So, I am wondering what these time intervals are accounting for, and if it is actually needed at all. Could it simply be from a previous era when the starting point was only average curves. My consideration is indoor, so cold weather is not a factor.
Does someone have some insights on this item? Thanks






RE: Relay-Fuse coordination CTI/Grading Time
RE: Relay-Fuse coordination CTI/Grading Time
Some allowance is required for:
CT Error
Relay error
RE: Relay-Fuse coordination CTI/Grading Time
If the above makes sense, I would conclude that Ieee 242-2001 is conservative, and is a broad brush. Further, we can have tighter intervals in the Inst/DT region. I'll probably stay with 100 ms for now (fear is my valuable assistant!). However, perhaps 50 ms is not so unreasonable, also.
RE: Relay-Fuse coordination CTI/Grading Time