Siemens SIPROTEC 7SD610, Руководство пользователя

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Functions
2.9 Backup Time Overcurrent Protection
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
102
Directional Characteristic
The directional characteristic of the directional overcurrent stages is preset. From the voltage and current
vectors used for direction determination, the angle difference
ϕ
(U) -
ϕ
(I) is calculated via the impedance
Z = U/I and the direction determined based on the directional characteristic displayed.
Figure 2-38 Directional characteristic of the time overcurrent protection
Definite Time High-set Current Stage
I
>>
Each phase current is compared with the setting value Iph>> after numerical filtering; the earth current is com-
pared with 3I0>> PICKUP . After pickup of a stage and expiry of the associated delay times T Iph>> or T
3I0>> a trip command is issued. The dropout value is approximately 7% below the pickup value, but at least
1.8% of the nominal current.
Figure 2-39 shows the logic diagram of the
I
>> stages. The stages can be blocked via the binary input „>BLOCK
O/C I>>“ . Additionally, the earth current can be blocked separately via a binary input „>BLOCK O/C Ie>>“ .
During the single-pole pause, the earth current stage is always blocked to avoid a fault pickup.
The binary input „>O/C InstTRIP“ and the evaluation of the indication „switch“ (onto fault) are common to
all stages and described below. They may, however, separately affect the phase and/or earth current stages.
This can be achieved with two parameters:
•
I>> Telep/BI
(address
2614
), 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 tripping
before automatic reclosure.
• I>> SOTF (address 2615 ), determines whether this stage shall issue non-delayed tripping ( YES ) or not ( NO )
in case of switching-onto-fault conditions.