Measured Value, Method of Measurement
The device can measure the residual voltage at the broken-delta winding. The measured voltage VN is
converted to a value with reference to the zero-sequence voltage V0. If the residual voltage is not available to
the device as a measurand, the zero-sequence voltage V0 is calculated from the measured phase-to-ground
voltages V
A
, V
B
, and V
C
using the defining equation.
Use the Method of measurement parameter to select the relevant method of measurement, depending on
the application:
•
Measurement of the fundamental component (standard filter):
This method of measurement processes the sampled voltage values and filters out the fundamental
component numerically.
•
Measurement of the RMS value (true RMS):
This method of measurement determines the voltage amplitude from the sampled values according to
the defining equation of the RMS value.
•
Measurement of the fundamental component over 2 cycle filters with triangular window:
This method of measurement processes the sampled voltage values and filters out the fundamental
component numerically. The extended filter length compared to the standard filter and the use of the
triangular window results in a particularly strong attenuation of harmonics and transient faults. The
extended filter length causes the pickup time to increase slightly compared to the standard filter (see
12.18.7 Non-Directional V0 Stage with Zero-Sequence Voltage/Residual Voltage).
Pickup, Dropout
The stage compares the Threshold with the zero-sequence voltage V0. The Pickup delay parameter
allows you to delay the pickup of the stage depending on the residual voltage.
With the Dropout ratio parameter, you can define the ratio of the dropout value to the Threshold.
Determination of the Faulty Phase
With the Detection of faulty phase parameter, you can enable or disable the determination of the
ground-fault phase. Determining is released when the stage picks up. If 2 phases exceed the threshold value
V> healthy ph-to-gnd volt. and one phase falls below the threshold value V< faulty ph-to-gnd
volt., the last phase is determined to be faulty and is signaled as such.
Blocking the Stage
In the event of blocking, the picked up stage will be reset. The following blocking options are available for the
stage:
•
Via the binary input signal >Block stage from an external or internal source
•
From inside on pickup of the measuring-voltage failure detection function. The Blk. by meas.-
volt. failure parameter can be set so that measuring-voltage failure detection blocks the stage or
does not block it.
•
From an external source via the binary input signal
>open
of the function block Voltage-transformer
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 measuring-voltage failure detection blocks the
stage or not.
Application and Setting Notes
Parameter: Method of measurement
•
Recommended setting value (_:12391:8) Method of measurement = fundamental comp.
The Method of measurement parameter allows you to define whether the function works with the funda-
mental component or the calculated RMS value.
6.15.10.2
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
SIPROTEC 5, Overcurrent Protection, Manual 609
C53000-G5040-C017-8, Edition 07.2017
To Next Page
Loading...
