ABB Relion 670 Series Applications Manual page 186

Section 8
Current protection
As the cooling system is
the time constant.
For example, the largest phase load current is taken as 1800 A, then:


final


operate
Here
At t=0
At next execution, θ
Therefore,
After the trip, a lockout is released to inhibit reconnecting the tripped circuit. The output lockout
signal LOCKOUT is activated when the temperature of the object is greater than the set lockout
release temperature setting
t
lockout release _
EQUATION1177 V1 EN-US
where:
t
lockout_release
Q
lockout_release
Consider that the current heat content θ

lockout release _
t
lockout release _
8.9 Breaker failure protection CCRBRF(50BF)
180
ON , IBase2 is selected as the base current and Tau2 setting is selected as
2
 
1800

 
2677685.95
 
1. 1
  
(1.2 1000 1.1 1.2)
Q > Q
final n
 
 
ThetaInit
n init
=1254528 and θ
n-1
  
t 90 ln((2677685.95 2509056) / (2677685.95 1254555.04)) 192 min
operate
ResLo .
æ
Q - Q
t
= - × ç final
ln
ç
Q
è
final
  
0.6 2509056 1505433.6
  
90 ln((2677685.95 1505433.6) / (2677685.95 2700000)) 244 min
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
2
2509056

  
0.5 2509056 1254528
operate
=1254555.04.
n

ö
lockout release _
÷
÷
- Q
ø
n
is the time to lockout release
is the lockout release level heat content =
is 2700000 and the cooling system is still
n


 
ResLo × θ
operate
ON , then:
 
Bay control REC670
Application manual
1MRK 511 401-UUS F
(Equation 66)
IP14514-1 v6