GE P24DM - North American Standards

Curve Description
b
constant a constant
L constant
IEC Very Inverse Operate 13.5 1 0
IEC Very Inverse Reset 50.92 2.4 0
IEC Extremely Inverse Operate 80 2 0
IEC Extremely Inverse Reset 44.1 3.03 0
UK Long Time Inverse Operate* 120 1 0
UK Rectifier Operate* 45900 5.6 0
Rapid Inverse (RI) characteristic
The RI operate cur
ve is represented by the following equation:
t K
M
op
=
−










1
0 339
0 236
.
.
where:
● t
op
is the operating time
● K is the Time Multiplier setting
● M is the ratio of the measur
ed current divided by the threshold current (I/I
s
)
Note:
* When using UK Long Time Inverse, UK Rectifier or RI for the Operate characteristic, DT (Definite Time) is always used for the
Reset characteristic.
3.1.3 NORTH AMERICAN STANDARDS
The IEEE IDMT Operate equation is:
t TD
M
L C
op
=
−
+






+
β
α
1
and the IEEE IDMT Reset equation is:
t TD
M
r
=
−






β
α
1
where:
● t
op
is the operating time
● t
r
is the reset time
● TD is the Time Dial setting
● M is the ratio of the measured current divided by the threshold current (I/I
s
)
●
b is a constant, which can be chosen to satisfy the required curve characteristic
●
a is a constant, which can be chosen to satisfy the required curve characteristic
● C is a constant for adding Definite Time (Definite Time adder)
● L is a constant (usually only used for ANSI/IEEE curves)
The constant values for the IEEE curves are as follows:
Chapter 6 - Current Protection Functions P24xM
88 P24xM-TM-EN-2.1