Application - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.2.6.6
620 series ANSI
Technical Manual
restart time, given in Equation
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
TRIP 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 TRIP output is not activated instantly. In this case, the
remaining part of the cooling timer affects the calculation of the trip timer as shown in
Figure 139. This compensates for the heating effect and makes the overall trip time
shorter.
GUID-E62B7A83-72F7-4489-B7BC-DE30D26BF6C7 V1 EN
Figure 139: Example of an inverse time counter operation if TRIP occurs when
BLK_RESTART
Ena level setting is considered to be 40 percent)

Application

If the laminated core of a power transformer or generator is subjected to a magnetic flux
density beyond its designed limits, the leakage flux increases. This results in a heavy
hysteresis and eddy current losses in the non-laminated parts. These losses can cause
12. The Restart Ena level setting determines the level when
− Ena restart level

 ⋅ Cooling time
100

is not active but COOL_ACTIVE is active. (The Restart
Section 4
Protection functions
(Equation 12)
305