ABB RELION 620 Series Technical Manual page 684

Section 4
Protection functions
678
GUID-6FC7624E-7E13-4645-8943-0FDFBAA1D184 V1 EN
Figure 343: Operating 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 OPERATE output activates the BLK_RESTART output.
For the IDMT characteristic "OvExt IDMT Crv4", the deactivation of the OPERATE
output activates the cooling timer. The Timer is set to the value entered in the Cooling
time setting. The Restart Ena level setting determines the level when BLK_RESTART
should be released.
100

enable restart time
=


GUID-8C676DA9-F90A-46B6-9A24-9D74C52DE442 V1 EN
If the excitation level increases above the set value when BLK_RESTART is active,
the OPERATE output is activated immediately.
If the excitation level increases above the set value when BLK_RESTART is not active
but COOL_ACTIVE is active, the OPERATE output is not activated instantly. In this
case, the remaining part of the cooling timer affects the calculation of the operate timer
as shown in Figure 344. This compensates for the heating effect and makes the overall
operate time shorter.
Ena restart level
−

Cooling time
 ⋅
100

1MRS757644 F
(Equation 136)
620 series
Technical Manual