ABB Relion Technical Manual page 245

1MRK 502 048-UUS A
Technical manual
æ
Q
t
= - × ç final
t ln
ç
operate Q
è
final
EQUATION1176 V1 EN
The calculated time to trip can be monitored as it is exported from the function as a real
figure TTRIP.
After a trip, caused by the thermal overload protection, there can be a lockout to reconnect
the tripped circuit. The output lockout signal LOCKOUT is activated when the
temperature of the object is above the set lockout release temperature setting ResLo.
The time to lockout release is calculated, That is, a calculation of the cooling time to a set
value.
æ
Q
t
= - × ç
t ln
ç
lockout release _
è
EQUATION1177 V1 EN
In the above equation, the final temperature is calculated according to equation 56. Since
the transformer normally is disconnected, the current I is zero and thereby the Θ
zero. The calculated component temperature can be monitored as it is exported from the
function as a real figure, TRESLO.
When the current is so high that it has given a pickup signal PICKUP, the estimated time
to trip is continuously calculated and given as analog output TTRIP. If this calculated time
get less than the setting time Warning, set in minutes, the output WARNING is activated.
ö
- Q
operate
÷
÷
- Q
ø
n
ö
- Q
final lockout release _
÷
÷
Q - Q
ø
final n
Section 8
Current protection
(Equation 61)
(Equation 62)
is also
final
239