Siemens SIPROTEC 7SK80 User Manual

Functions
2.9 Thermal Overload Protection 49
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
153
Ambient or Coolant Temperature
The specifications made up to now are sufficient to model the overtemperature. The ambient or coolant tem-
perature, however, can also be processed. This has to be communicated to the device as digitalized measured
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 tem-
perature of 104° F or 40° C.
Since all calculations are performed with standardized quantities, the ambient temperature must also be stan-
dardized. 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.
with
Θ
Nomsec
Machine temperatur at secondary nominal current = setting at the protection device (address
4209 or 4210)
Θ
Nom Mach
Machine temperature at nominal machine current
I
Nom CT prim
Nominal primary CT current
I
Nom Mach
Nominal current of the machine
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:
with
τ
th
TIME CONSTANT (address 4203)
k 49 K-FACTOR (address 4202)
I
Nom
Nominal device current in A
I Actually Flowing Secondary Current
I
Pre
Previous Load Current
Θ
Nom
Temperature at nominal current I
Nom
(address 4209 49 TEMP. RISE I)
Θ
v
Coolant temperature input (scaling with address 4209 or 4210)

Siemens SIPROTEC 7SK80 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SK80
Category	Protection Device
Language	English