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Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
Stabilization Counter
To determine a reliable direction result, the function uses a stabilization counter. For indicating a direction
result, the determined direction must be stable for 4 successive measuring cycles. The cycle time is 10 ms.
Direction-Result Extension
With the timer Dir.-result extension, you can extend the last determined direction result if the condi-
tions for a further direction determination are no longer met. The last direction result is held until the condi-
tions for a further direction determination are met again (timer is reset) or until the timer expires. The
behavior of the direction-result extension varies according to the setting of the Directional mode param-
eter:
•
Directional mode = forward or reverse
As soon as the zero-sequence harmonic current 3I0harm. or the zero-sequence harmonic voltage
V0harm. falls below its respective dropout value, the timer Dir.-result extension starts. If the
direction result equals the setting of the Directional mode parameter, the last
extended.
If both 3I0harm. and V0harm. exceed their thresholds again, the timer Dir.-result extension is
reset immediately and the direction determination is carried out again.
•
Directional mode = non-directional
As soon as the zero-sequence harmonic current 3I0harm. falls below its dropout value, the timer Dir.-
result extension starts.
In this directional mode, the
of the actual direction that is indicated via the
the
unknown information is extended.
If 3I0harm. exceeds its threshold again, the timer Dir.-result extension is reset immediately and
the direction determination is carried out again.
Measured Value Display
After the timer Dir. determination delay expires and the V0 fundamental-component value keeps
exceeding the V0> threshold value, the following measured values are issued:
•
V0 harm.
•
3I0 harm.
•
Phi(I,V) harm.
These measured values are displayed as --- if 3I0harm. or V0harm. is smaller than 0.005 % of the rated secon-
dary current or voltage.
Blocking the Stage via Binary Input Signal
You can block the stage externally or internally via the binary input signal
blocking, the picked up stage will be reset.
Blocking the Stage in Case of Measuring-Voltage Failure
The stage can be blocked if a measuring-voltage failure occurs. In the event of blocking, the picked up stage
will be reset.
The following blocking options are available for the stage:
•
From inside on pickup of the Measuring-voltage failure detection function
•
From an external source via the binary input signal
circuit breaker, which links in the tripping of the voltage-transformer circuit breaker
The Blk. by meas.-volt. failure parameter can be set so that the Measuring-voltage failure detec-
tion blocks the stage or not.
604
Pickup is signaled only with the direction information unknown regardless
Ground fault signal. Therefore, the Pickup signal with
>Open of the function block Voltage-transformer
Pickup signal is also
>Block stage . In the event of
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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