CO2 Overcurrent Formula
CO2 Overcurrent Formula
(OP)
Hello,
I am looking for the formula that describes a Westinghouse CO2 (Short Time Inverse). I have the manual that shows the pictures of the curves and it accurately describes the time per my test of 5 times the min. pu.
I searched these boards and found the .pdf attached below that gives a CO2 formula, but this does not synch with what the graph in the CO2 manual shows.
My settings are a min. pu of 4A, a TD of 3.5, and I am applying a 5X min pu. I should be getting 14 cycles (.233s)
Per the formula in the attached document, it says I should be getting about 0.202
Thoughts?
I am looking for the formula that describes a Westinghouse CO2 (Short Time Inverse). I have the manual that shows the pictures of the curves and it accurately describes the time per my test of 5 times the min. pu.
I searched these boards and found the .pdf attached below that gives a CO2 formula, but this does not synch with what the graph in the CO2 manual shows.
My settings are a min. pu of 4A, a TD of 3.5, and I am applying a 5X min pu. I should be getting 14 cycles (.233s)
Per the formula in the attached document, it says I should be getting about 0.202
Thoughts?






RE: CO2 Overcurrent Formula
RE: CO2 Overcurrent Formula
I'll look it up later and post it.
The Basler best fit is also quite accurate.
RE: CO2 Overcurrent Formula
I found this formula:
t(s) = 105.2ms * Td / (M^0.8 - 1) + 26.2ms * Td
with M = multiples of PU.
With your values (Td = 3.5 and M = 5) I get 232ms, so it seems to fit to the values from your manual.
OMICRON customers are supported in testing this relay by using the PTL (free library of test templates) which also makes use of this formula.
Hope I could help a little,
Oliver Janke
OMICRON Project engineer