Functions
2.9 Backup Time Overcurrent Protection
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
105
Directional, Definite Time Overcurrent Stage I>
The directional overcurrent stages follow the same principle as the non-directional stages. However, triggering
is not dependent on the result of the direction determination. Direction determination occurs via the measuring
values and the respective directional characteristics.
The pickup of the phase current stages is non-directional, if address 2680 Direction Iph> is parameterised
to Non-Directional. The pickup of the earth stage is non-directional, if address 2683 Direction 3I0> is
parameterized to Non-Directional.
Iph> Dir. is used as setting values for the phase current, 3I0> Dir. for the earth current. After pickup of
a stage and expiry of the associated time delays T Iph> Dir. or T 3I0> Dir., a trip command is issued.
The dropout value is approximately 7 % of the pickup value, but at least 1.8 % of the nominal current, below
the pickup value.
Figure 2-41 shows the logic diagram of the I>ger stages. The stages can be blocked via the binary input
„>BLOCK Dir. I>“. Additionally, the earth current can be blocked separately via a binary input „>BLOCK
Dir. Iep“.
During fuse failure or pickup of the Fuse Failure Monitor all stages which are parameterized as Forward or
Reverse are blocked. During the single-pole pause, the earth current stage is always blocked to avoid a fault
trigger.
The binary input „>O/C InstTRIP“ and the evaluation of the indication „switch“ (onto fault) can separately
affect the phase and/or earth current stages. This can be achieved with two parameters:
• I>Dir.Telep/BI (address 2686), determines whether a non-delayed trip of this stage via binary input
„>O/C InstTRIP“ is possible (YES) or impossible (NO). This parameter is also used for instantaneous trip-
ping before automatic reclosure.
• I> Dir. SOTF (address 2687), determines whether this stage shall issue non-delayed tripping (YES) or
not (NO) in case of switching-onto-fault conditions.
From the individual phase or earth current specific direction determination (7240 to7247) the indications „O/C
Dir.forward“ or.. „O/C Dir.reverse“ are created, if there is a valid result of the direction determination
for a phase or earth current (forward or backward). These indications can then be transferred to a different
device and there cause an immediate trip if an overcurrent stage of the receiving device has picked up. The
indications must then be combined via CFC (OR function).
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