ABB 615 Series - Page 655

GUID-BD1205DC-1794-4F64-A950-6199C54DB7B1 V1 EN
Figure 322: Trip time curves for the overexcitation IDMT curve ("OvExt IDMT Crv1")
for parameters a = 2.5, b = 115.0 and c = 4.886
Overexcitation IDMT curve 4
The base equation for the IDMT curve “OvExt IDMT Crv4” is:
t s d
k
M
( )
.
( )
= +
−
0 18
1
2
GUID-361FE32F-D157-402D-BC70-D568AB809339 V1 EN (Equation 123)
t(s)
Trip time in seconds
d Constant delay setting in milliseconds
M Excitation value (V/f ratio or volts/hertz) in pu
k Time multiplier setting
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 649
Technical Manual