Protection Functions
PRS-7367 75
3.8.1.2 Signals
Table 3.8-1 Input Signals
The current magnitude in all the three phases
The input signal of clearing thermal
Table 3.8-2 Output Signals
This is the integrated start signal
This is the integrated operation signal.
This is the integrated Alarm signal
3.8.2 49F Protection Principle
The thermal overload protection function has two operation types: one for alarm and one for
tripping, which can be enabled or disabled by respectively setting the corresponding
49F_Alm_Ena and 49F_Trp_Ena parameter values as "1" or "0".
The operation of three-phase thermal protection can be described by using a module diagram. All
the modules in the diagram are explained in the next sections.
The functional module diagram is shown as below:
2
1
( ) (1 )
tt
tt
B
I
ee
kI
&
En_Alm_Thrm=1
En_Tr_Therm=1
Figure 3.8-2 Functional module diagram
The function continuously checks the highest measured phase current value and reports the
highest value to the temperature calculator.
If
is more than the set value of 49F_K_Tr, the 49F_Str output is activated. Whereas,
if
is smaller than the set value of 49F_K_Tr, the 49F_Str output is deactivated.
The final temperature rise is calculated from the highest of the three-phase currents according to
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