European Standards; Figure 29: Iec 60255 Idmt Curves - GE MiCOM P40 Agile Technical Manual

P14x

Figure 29: IEC 60255 IDMT curves

2.1.2

EUROPEAN STANDARDS

The IEC 60255 IDMT Operate equation is:
β

=
t T 
α
−
op

M 1
and the IEC 60255 IDMT Reset equation is:
β
 
=
t T  
α
r −
 
1 M
where:
t is the operating time
●
op
t is the reset time
●
r
T is the Time Multiplier setting
●
M is the ratio of the measured current divided by the threshold current (I/Is)
●
β is a constant, which can be chosen to satisfy the required curve characteristic
●
α 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 IEC IDMT curves are as follows:
Curve Description
IEC Standard Inverse Operate
IEC Standard Inverse Reset
P14xEd1-TM-EN-1
1000.00
100.00
10.00
1.00
0.10
1
E00600

+  +
L C

b constant
0.14
8.2
Chapter 6 - Current Protection Functions
Long Time Inverse (
Standard Inverse (SI)
Very Inverse (VI)
Extremely Inverse (EI)
100
10
Current (multiples of I )
S
a constant
0.02
6.45
LTI )
L constant
0
0
91