ABB RELION 620 Series Technical Manual page 877

1MAC504801-IB E
12.3.2
12.3.2.1
620 series ANSI
Technical Manual
IDMT curves for undervoltage protection
In the inverse-time modes, the trip time depends on the momentary value of the voltage,
the lower the voltage, the faster the trip time. The trip time calculation or integration starts
immediately when the voltage goes below the set value of the Pickup value setting and the
PICKUP output is activated.
The TRIP output of the component is activated when the cumulative sum of the integrator
calculating the undervoltage situation exceeds the value set by the inverse-time mode. The
set value depends on the selected curve type and the setting values used. The user
determines the curve scaling with the Time multiplier setting.
The Minimum trip time setting defines the minimum trip time possible for the IDMT
mode. For setting a value for this parameter, the user should carefully study the particular
IDMT curve.
Standard inverse-time characteristics for undervoltage protection
The trip times for the standard undervoltage IDMT curves are defined with the
coefficients A, B, C, D and E.
The inverse trip time can be calculated with the formula:
k A ⋅
 
t s
=
   
E
V < − V
 
B × − C
 
V <
 
GUID-4A433D56-D7FB-412E-B1AB-7FD43051EE79-ANSI V1 EN
t [s] trip time in seconds
V measured voltage
Pickup value setting
V< the set value of the
Time multiplier setting
k the set value of the
Table 616: Curve coefficients for standard undervoltage IDMT curves
Curve name A
(21) Inverse 1
Curve A
(22) Inverse 480
Curve B
General function block features
+ D
B C
1 0
32 0.5
Section 12
(Equation 114)
D E
0 1
0.055 2
871