!PPENDIX
3*
6
# ' #
#
#ALCULATION %XAMPLES
#
#ABLE 4HERMAL OVERLOAD PROTECTION
ST EXAMPLE
'IVEN
PERMISSIBLE CONTINUOUS CURRENT
)
MAX
! AT
^
# AMBIENT TEMPERATURE
MAXIMUM PERMISSIBLE CURRENT FOR S
)
S
|
)
MAX
K!
CURRENT TRANSFORMERS
! !
4HIS RESULTS IN
SELECTED SETTING VALUE K
SELECTED SETTING VALUE MINUTES
K
)
MAX
)
.
!
!
Ç
MIN
)
S
I
MAX
MINUTES
4HE CABLE WIRES SHOULD BE THERMALLY INDEPENDENT FROM ONE ANOTHER 4HE MODE OF MEASURED VALUE FORMATION IS
SET IN ADDRESS /, #!,#5,
-!8
4HE EXPECTED TRIPPING TIME CAN BE DERIVED FROM THE TEMPERATURE EQUATION FOR A CONSTANT CURRENT JUMP
4HE RESULTING TRIPPING TIME 4
TRIP
T
PRE
E
TÇ
PRE
WITH
)
K )
.
4
TRIP
Ç
LN
)
)
MAX
)
PRE
)
MAX
)
)
MAX
)F FOR EXAMPLE THE PRELOAD IS )
PRE
! AND THE CURRENT JUMPS TO ) ! THE TRIPPING TIME 4
TRIP
WOULD BE
4
TRIP
MINUTES LN
MINUTES
4
TRIP
MINUTES S
ND EXAMPLE
'IVEN
0ERMISSIBLE CONTINUOUS CURRENT
)
MAX
! AT
^
# AMBIENT TEMPERATURE
4HE CABLE SHOULD BE CAPABLE TO CARRY TWICE THE PERMISSIBLE CONTINUOUS CURRENT FOR MINUTES
IE
4
4RIP
MIN AT )
|
)
MAX
!
0RELOAD NOT CONSIDERED IE )
PRE
4HE FOLLOWING TIME CONSTANT
Ç
RESULTS
Ç
4
4RIP
LN
))MAX
)PRE)MAX
))MAX
MIN
LN
Ç
MINUTES
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