Dropout Delay
Switching on the capacitor usually causes 3I0 to decrease in the faulty feeder. This must not cause the stage to
drop out. For that reason, a dropout delay is active for the sum of the Pulse-on duration and Pulse-off
duration values.
Detected Pulses of the Ground Fault
The stage records the total number of detected pulses during the permanent ground fault. If the function
resets or the operate condition is met, this number is issued via the signal
Detected pulses
.
Blocking the Stage via Binary Input Signal
You can block the stage externally or internally via the binary input signal
>Block stage
. In the event of
blocking, the picked up stage will be reset.
Application and Setting Notes
Parameter: V0> threshold value
•
Default setting (_:102) V0> threshold value = 30.000 V
The V0> threshold value parameter allows you to set the zero-sequence (fundamental) voltage sensi-
tivity of the stage. Set the threshold value smaller than the minimum absolute value of the zero-sequence
voltage V0 that must still be detected.
If VN or V0 is not available, the V0> threshold value parameter is hidden and the 3I0> threshold
value parameter is visible and used.
Parameter: 3I0> threshold value
•
Default setting (_:101) 3I0> threshold value = 0.200 A
If VN or V0 is not available, the 3I0> threshold value parameter is visible and used.
The 3I0> threshold value parameter allows you to set the zero-sequence (fundamental) current sensi-
tivity of the stage. Set the threshold value smaller than the minimum absolute value of the zero-sequence
current 3I0 that must still be detected.
Parameter: Pulse-on duration, Pulse-off duration
•
Default setting (_:104) Pulse-on duration = 1.00 s
•
Default setting (_:105) Pulse-off duration = 1.50 s
With the Pulse-on duration and Pulse-off duration parameters, you define the switch-on and
switch-off duration of the capacitor.
These values must be set according to the operation of the clocking device that determines the switch-on and
switch-off duration of the capacitor. If you set these 2 parameters to the same or similar values, there is a risk
of failure because the stage cannot distinguish the healthy and faulty feeders by only evaluating the ground
current during a high-impedance ground fault.
Parameter: Max.tolera.pulse-on or off
•
Default setting (_:109) Max.tolera.pulse-on or off = 0.15 s
With the Max.tolera.pulse-on or off parameter, you define the tolerance for the measured pulse-on/
pulse-off duration. The tolerance is the maximum deviation from the set values for the Pulse-on duration
and Pulse-off duration parameters.
The recommended setting for this parameter is the maximum tolerance of the clocking device plus 40 ms
(tolerance of the SIPROTEC 5 device). For the tolerance of the clocking device, you have to consider the toler-
ances of the pulse-on and pulse-off durations individually and select the larger tolerance of both.
6.15.13.2
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
624 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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