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6 - 14
Siemens AG ⋅ January 1999
A current threshold can be set for blocking by the difĆ
ferential current monitoring function ("Spill current")
(addr. 10 I-Spc) with the settable delay (addr. 10
T-Spc).
Due to the capacitance of the pilot wires, the protecĆ
tion detects a differential current which is dependent
on the line length and the load current. A reference
value for this differential current can be calculated
with the following equation:
diff
(%) = 0.025
operation
(%) x L (km) forf=50Hz,
diff
(%) = 0.033
operation
(%) x L (km) forf=60Hz.
The parameter 10 -Spc must be set greater than this
value.
A
1 0 I – S p c
0 . 4
Y
B
[1550]
Current threshold for differential current monitoring
(Spill Current)
smallest setting value: 0.1 I
N line
.......
largest setting value: 1.0 I
N line
.........
A
1 0 T – S p c
5 s
Y
[1551]
Delay for differential current monitoring
smallest setting value: 5 s............
largest setting value: 60 s.............
6.3.5 Settings for the pilot wire monitoring
The device can be equipped with a pilot wire monitoĆ
ring to monitor the healthy state of the pilot wires.
This is available in the versions 7SD600K-KKKKK-2
and 7SD600K-KKKKK-3. A further precondition for this
function (see Section 5.4.2) is that addr. 00PW.MON
= was set when configuring the device
functions. The pilot wire monitoring can also be switĆ
ched and under addr. 11PW.MON.
The pilot wire monitoring operates with a pulse code
which is modulated onto an AF signal (2000 Hz). The
signals can only be transmitted in one direction at a
time. The direction alternates in order to be able to
create defined start conditions when switching on the
devices or after an auxiliary supply failure, one of the
two connected devices must be appointed "Master"
and the other as "Slave". The "Master" device alĆ
ways starts the signal traffic, the "Slave" device simĆ
ply replies. The appropriate ID is set under addr.
11STATN.
If a fault in the pilot wire connection is detected, this
can either be reported only or the differential protecĆ
tion is blocked additionally (addr. 11DIF.BL). If the pilot
wire is interrupted, the differential protection cannot
trip anyway; in the event of a pilot wire short-circuit,
on the other hand, the device would also trip in the
event of an external short-circuit. Reporting of the
wire fault and blocking if necessary are delayed by
the time (addr. 11T-DiBl).
The pilot wire monitoring does not operate as long as
there is a fault or a transfer trip or remote trip comĆ
mand being transmitted.
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