Current-Jump Detection
Overview of Functions
The Current jump detection function has the following tasks:
•
Detection of jumps in the phase or zero-sequence current (ΔI)
•
Generation of an indication when the measurands change by more than a configured threshold value
from one system period to the next.
The function for detecting jumps in the phase or zero-sequence current is an additional function used for indi-
cation purposes or for further processing in user-specific CFC logics. Pick up of the function therefore neither
opens a separate fault in the fault log nor generates an operate indication.
Structure of the Function
The Current-jump detection function is used in protection function groups based on current measurement. It
can be instantiated multiple times.
[dwstruki-111026-01.tif, 1, en_US]
Figure 6-330 Structure/Embedding of the Function
Function Description
Current-jump detection operates directly with the sampled values without numeric filtering. This provides very
short response times to sudden changes in the current. The method used is not sensitive to slow changes of
amplitude or frequency.
Using a configurable selection of measured values, you can select from 3 line currents or the residual current.
Current-jump detection is phase-selective for the line current A, B and C.
The difference from the previous sampled value of the first system cycle is calculated for each sampled value.
The rectified average is then determined for a ½ system cycle from this differential signal Δi(t). The rectified
average for sinusoidal measurands is then converted to a RMS value ΔI by subsequent multiplication by 1.11.
The resultant measurand ΔI is then compared with the threshold value.
If the parameter (_:101) Threshold is exceeded, the output indication
Jump
is generated. If you have
selected the phase currents for measurement, the output indication data type used includes the separate
phase information. If you have selected the residual current for measurement, the output indication data type
used includes the NI information. If the current-jump detection responds (ΔI
Limit
), the general information is
generated in the output indication in all cases.
Dropout occurs with a dynamically increased threshold value (ΔI
Limit
) in accordance with the logic in
Figure 6-331. Dynamic increase of the dropout threshold value achieves optimally short dropout times.
The output indication
Pulse
is formed with the configurable timer (_:102) Minimum pulse length. As
a consequence this output indication has a consistent minimum size. If you activate the binary input
>Pulse
extension
, you can prolong the pulse duration even further. If the binary input
>Pulse extension
has
been activated, the indication
Pulse
drops off when the configured time has elapsed and the falling edge of
the binary input is detected.
6.49
6.49.1
6.49.2
6.49.3
Protection and Automation Functions
6.49 Current-Jump Detection
SIPROTEC 5, Overcurrent Protection, Manual 957
C53000-G5040-C017-8, Edition 07.2017
To Next Page
Loading...
