ABB RELION REF615R, Technical Manual

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enable restart time
Ena restart level
Cooling time
=
−





 ⋅
100
100
GUID-8C676DA9-F90A-46B6-9A24-9D74C52DE442 V1 EN
(Equation 7)
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 operation timer as shown
in
Figure 122 . This compensates for the heating effect and makes the overall trip time
shorter.
GUID-E62B7A83-72F7-4489-B7BC-DE30D26BF6C7 V1 EN
Figure 122: Example of an inverse time counter operation if
TRIP
occurs when
BLK_RESTART
is inactive while
COOL_ACTIVE
is active. The Restart
Ena level setting is considered to be 40 percent.
4.2.5.6 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
excessive heating and severe damage to the insulation and adjacent parts in a relatively
short time.
1MRS240050-IB C
Section 4
Protection functions
REF615R 255
Technical Manual