Siemens SIPROTEC 4 7SJ61 Manual page 118

Functions
2.7 Thermal Overload Protection 49
used instead of the thermal warning element by setting the thermal warning element to 100 % thus virtually
disabling it.
Extension of Time Constants
TIME CONSTANT set in address 4203 is valid for a running motor. When a motor without external cooling is
running down or at standstill, the motor cools down more slowly. This behavior can be modeled by increasing
the time constant by factor Kτ-FACTOR, set at address 4207. Motor stop is detected if the current falls below
the threshold value BkrClosed I MIN of the current flow monitoring (see side title "Current Flow Moni-
toring" in Subsection
threshold. The pickup threshold BkrClosed I MIN affects also the following protection functions: voltage
protection and restart inhibit for motors.
If no differentiation of the time constants is necessary (e.g. externally-cooled motors, cables, lines, etc.) the
Kτ-FACTOR is set at 1 (default setting value).
Dropout Time after Emergency Starting
The dropout time to be entered at address 4208 T EMERGENCY must ensure that after an emergency startup
and after dropout of the binary input
replica is below the dropout threshold again.
Ambient or Coolant Temperature
The specifications made up to now are sufficient to model the overtemperature. The ambient or coolant
temperature, however, can also be processed. This has to be communicated to the device as digitalized meas-
ured value via the interface. During configuration, parameter 142 49 must be set to With amb. temp..
If the ambient temperature detection is used, the user must be aware that the 49 K-FACTOR to be set refers
to an ambient temperature of 104° F or 40° C, i.e. it corresponds to the maximum permissible current at a
temperature of 104° F or 40° C.
Since all calculations are performed with standardized quantities, the ambient temperature must also be
standardized. The temperature at nominal current is used as standardized quantity. If the nominal current
deviates from the nominal CT current, the temperature must be adapted according to the formula following.
In address 4209 or 4210 49 TEMP. RISE I the temperature adapted to the nominal transformer current is
set. This setting value is used as standardization quantity for the ambient temperature input.
[formel-maschinentemperatur-260602-kn, 1, en_US]
with
Θ
Nom sec
Θ
Nom Mach
Ι
NomCT prim
Ι
Nom Mach
If the temperature input is used, the tripping times change if the coolant temperature deviates from the
internal reference temperature of 104° F or 40° C. The following formula can be used to calculate the tripping
time:
[fo_tripping-time-overload, 1, en_US]
with
118
2.1.3.2 Setting Notes). This understands that the motor idle current is greater than this
>EmergencyStart the trip command is blocked until the thermal
Machine temperatur at secondary nominal current = setting at the protection
device (address 4209 or 4210)
Machine temperature at nominal machine current
Nominal primary CT current
Nominal current of the machine
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016