Siemens Siprotec 7UM611 Manual page 67

If the temperature input is used, the trip times change if the coolant temperature devi-
ates from the internal reference temperature of 104.00 °F or 40 °C. The following
formula can be used to calculate the trip time:
with
τ
k
I
I
I
Θ
Θ
Example:
Machine:
I
I
τ
Current transformer: 500 A/1 A
7UM61 Manual
C53000-G1176-C127-3
TIME CONSTANT (address 1603)
K-FACTOR (address 1602)
Nominal Device Current
N
Actually Flowing Secondary Current
Previous Load Current
Pre
Temperature with Nominal Current I
N
Coolant Temperature Input (Scaling with Address 1608 or 1609)
K
= 483 A
NMach
= 1.15 I
maxMach N
= 600 s (thermal time constant of the machine)
th
2.9 Thermal Overload Protection (ANSI 49)
at Θ = 40 °C
K
(Address 1605)
N
67