Siemens siprotec SJ62 User Manual page 183

2 Functions
Warning Tempera-
ture Level
Extension of Time
Constants
Dropout Time after
Emergency Starting
181
Example: Cable and current transformer with the following data:
Permissible Continuous Current I
Maximum current for 1 s
Current Transformer
Example: Cable and current transformer with the following data:
Thus results:
The settings are: 49 K-FACTOR = 0.83; TIME CONSTANT = 33.7 min
By setting the thermal warning level 49 Θ ALARM at address 4204, a warning
message can be issued prior to tripping, thus allowing time for load curtailment proce-
dures to be implemented. This warning level simultaneously represents the dropout
level for the tripping signal. Only when this threshold is undershot, the tripping
command is reset and the protected equipment may be returned to service.
The thermal warning level is given in % of the tripping temperature level.
A current warning level is also available (address 4205 I ALARM). The setting corre-
sponds to secondary amperes, and should be set equal to, or slightly less than, per-
missible continuous current (k · I
level by setting the thermal warning level to 100 % and thereby practically disabling it.
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 margin
heading "Current Flow Monitoring" in Section 2.1.3.2). This assumes that the motor
idle current is greater than this threshold. The pickup threshold BkrClosed I MIN
affects also the following protection functions: breaker failure 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).
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 „>EmergencyStart" the
trip command is blocked until the thermal replica is below the dropout threshold again.
= 500 A at Θ = 104 °F or 40 °C
max u
= 45 · I = 22.5 kA
I
1s max
600 A / 1 A
). It may be used in lieu of the thermal warning
Nom sec
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015