Multiples of tap value current in IDMT Curves
Multiples of tap value current in IDMT Curves
(OP)
Dear All,
When the relay current equals the pickup current, the relay should start picking up,i.e (when the psm is equal to or greater than 1) but why does all the curves begin at 1.5 x tap setting or 2 x tap setting in the reference curves provided by the relay manufacturer; why not at 1 (or) 1.1?
When the relay current equals the pickup current, the relay should start picking up,i.e (when the psm is equal to or greater than 1) but why does all the curves begin at 1.5 x tap setting or 2 x tap setting in the reference curves provided by the relay manufacturer; why not at 1 (or) 1.1?






RE: Multiples of tap value current in IDMT Curves
RE: Multiples of tap value current in IDMT Curves
t(I)=A/(M^p-1)+B where M is the multiple of pickup, T(I) is the trip time, and the other constants are determined by the curve shape. You can see you have a division by zero problem at M=1, so t(I) is undefined.