Siemens SIPROTEC 7UM62, Manual

Page: 78 / 602

Functions
62
7UM62 Manual
C53000-G1176-C149-3
If the temperature input is used, the trip times change if the coolant temperature
deviates from the internal reference temperature of 40 °C. The following formula can
be used to calculate the trip time:
where
τ
–
TIME CONSTANT
(address
1603
)
k –
K-FACTOR
(address
1602
)
I
N
– Nominal device current
I – Actually flowing secondary current
I
pre
– Previous load current
Θ
N
– Temperature with nominal current I
N
(address
1605 TEMP. RISE I
)
Θ
K
– Coolant temperature input(scaling with address
1608
or
1609
)
Example:
Machine: I
NMach
= 483 A
I
maxMach
= 1.15 I
N
at
Θ
K
= 40 °C
Θ
NMach
= 93° C Temperature at I
NMach
τ
= 600 s (thermal machine time constant)
Current transformer: 500 A / 1 A
t
τ
I
k I
N
⋅
------------
è ø
æ ö
2
Θ
K
40 °C –
k
2
Θ
N
⋅
----------------------------
I
pre
k I
N
⋅
------------
è ø
æ ö
2
– +
I
k I
N
⋅
------------
è ø
æ ö
2
Θ
K
40 °C –
k
2
Θ
N
⋅
----------------------------
1 – +
------------------------------------------------------------------------------------ ln
⋅
=
1 15
,
483 A
500 A
---------------
⋅
1 11 ,
≈
(to be set at address
1602
)
K-FACTOR
=
Θ
Nsec
93° C
500
483
----------
è ø
æ ö
2
⋅
100° C
≈
=
(to be set at address
1605
or
1606
TEMP. RISE I)