ABB RELION 620 Series Technical Manual page 310

Section 4
Protection functions
304
d 0 18 . k
t s ( ) = +
2
1000
( M − 1 )
GUID-E9F10438-C3F2-4440-AB4B-32C2EB17CF72 V1 EN
t(s) the trip time in seconds
Constant delay setting in seconds
d the
M the excitation value (V/f ratio or volts/hertz) in pu
k the Time multiplier setting
GUID-6FC7624E-7E13-4645-8943-0FDFBAA1D184 V1 EN
Figure 138: Trip time curves for the overexcitation IDMT curve 4 ("OvExt IDMT Crv4")
for different values of the Time multiplier setting when the Constant delay
is 800 milliseconds
The activation of the TRIP output activates the BLK_RESTART output.
For the IDMT characteristic "OvExt IDMT Crv4", the deactivation of the TRIP output
activates the cooling timer. The timer is set to the value entered in the Cooling time setting.
The COOL_ACTIVE output is kept active until the cooling timer is reset, whereas the
BLK_RESTART output remains active until the timer exceeds the value to enable the
1MAC504801-IB E
(Equation 11)
620 series ANSI
Technical Manual