2 Functions
152
7SA522 Manual
C53000-G1176-C155-3
derived from a set of three star connected current transformers must be available and
connected to the device.
The zero-sequence voltage is determined by its definition formula
3 U
0
= U
L1-E
+ U
L2-E
+ U
L3-E
. Depending on the application for the fourth voltage input
U
4
of the device, the zero-sequence voltage can be measured or calculated. If the
fourth voltage input is connected to the open delta winding U
delta
of a voltage trans-
former and if it is configured accordingly (address 8WUDQVIRUPHU = 8GHOWD
WUDQVI, see Subsection 2.1.3.1 ), this voltage is used — considering the factor 8SK
8GHOWD (address , see Subsection 2.1.3.1). If not, the device calculates the
zero-sequence voltage from the phase voltages. Naturally, all three phase-to-earth
voltages obtained from a set of three star-connected voltage transformers must be
available and connected to the device.
Definite Time Very
High Set Current
Stage 3I
0
>>>
The triple zero-sequence current 3 I
0
is passed through a numerical filter and then
compared with the set value ,!!!. If this value is exceeded an alarm is issued.
After the corresponding delay time 7,!!! have expired, a trip command is issued
which is also alarmed. The reset threshold is approximately 95 % of the pick-up
threshold.
Figure 2-63 shows the logic diagram of the 3I
0
>>>-stage. The function modules “di-
rection determination”, “permissive teleprotection”, “switch onto fault”, and “inrush sta-
bilization” are common to all stages and described below. They may however affect
each stage individually. This is accomplished with the following setting parameters:
• 2SPRGH,!!!, determines the operating direction of the stage: )RUZDUG,
5HYHUVH, 1RQ'LUHFWLRQDO or ,QDFWLYH,
• ,!!!7HOHS%,, determines whether a non-delayed trip with the teleprotection
scheme or binary input 1310 is possible (<(6) or not possible (12),
• ,!!!627)7ULS, determines whether during energization of the feeder onto a
fault tripping with this stage shall be non-delayed (<(6) or not (12) and
• ,!!!,QUXVK%ON, which is used to switch the inrush stabilization (rush blocking)
on (<(6) or off (12).
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