The method of measurement processes the sampled current values and filters out the fundamental compo-
nent numerically.
Depending on the connection type of the measuring point as well as the current terminal blocks used,
different linearity and setting ranges result. You can find more information in section Measured Value 3I0,
Method of Measurement , Page 569.
Pulse Detection, Pulse Counter
For this stage, voltage routing is optional and current routing is mandatory.
•
If VN or V0 is available, the voltage is the only criterion for starting the pulse-detection logic. When the
fundamental-component value of V0 exceeds the V0> threshold value, the pulse-detection logic is
started.
•
If VN or V0 is not available, the current is the only criterion for starting the pulse-detection logic. When
the fundamental-component value of the zero-sequence current 3I0 exceeds the 3I0> threshold
value, the pulse-detection logic is started.
If the measured current pulse-off duration equals to the value of the Pulse-on duration parameter and
the measured current pulse-on duration equals to the value of the Pulse-off duration parameter, a valid
pulse is detected.
After the first valid pulse is detected, the pulse counter is started to count the number of pulses continuously
until the stage resets.
Pickup, Operate
After the first valid pulse is detected, the stage picks up.
If the number of detected pulses within the pulse monitoring time reaches the setting of the No. of
pulses for operate parameter, the stage operates. The pulse monitoring time is calculated via the
following formula:
Pulse monitoring time = Value Monitoring time(in pulses) ⋅ (Value Pulse-on duration + Value
Pulse-off duration)
For example, the value of the No. of pulses for operate parameter is 3, and the value of the Moni-
toring time(in pulses) is 5. Then the pickup and operate time diagram is as follows:
[dw_pulse pickup and operate, 1, en_US]
Figure 6-149 Pickup and Operate Time
•
After the 3rd valid pulse is detected, the stage does not operate because the time between the 1st and
the 3rd valid pulses is greater than the pulse monitoring time which is 5 clocking pulses.
•
After the 4th valid pulse is detected, the stage operates because the time between the 2nd and the 4th
valid pulses is within the pulse monitoring time which is 5 clocking pulses.
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
SIPROTEC 5, Overcurrent Protection, Manual 623
C53000-G5040-C017-8, Edition 07.2017
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