ABB REB650 - Page 128

2
final
ref
I
I
is the steady state heat content
I
is the largest phase load current
I
ref
is the given reference load current


2
operate Bx ref Trip
III  
is the operate level heat content
I
Bx
is the selected base current based cooling
system ON / OFF
I
Trip
is the operate level load current
θ
n
is the current heat content
Consider that the given system has IBase of 1000 A and the cooling system is ON.
The following settings are used to calculate the operate time:
IRef 110%
IBase1 110% of IB
IBase2 120% of IB
Tau1 150 min
Tau2 90 min
IHighTau1 110% of IB1
Tau1High 125% of tC1
ILowTau1 90% of IB1
Tau1Low 75% of tC1
IHighTau2 110% of IB2
Tau2High 115% of tC2
ILowTau2 90% of IB2
Tau2Low 85% of tC2
ITrip 120% of IBx
ThetaInit 50%
ResLo 60% of Itr
As the cooling system is ON, IBase2 is selected as the base current and Tau2
setting is selected as the time constant.
For example, the largest phase load current is taken as 1800 A, then:
2
1800
1.
2677685.95
1
final





2
(1.2 1000 1.1 1.2) 2509056
operate
   
Section 7 1MRK 505 388-UEN B
Current protection
122 Busbar protection REB650 2.2 IEC
Application manual