[dw_sfcm-pulse_pattern-overcomp, 1, en_US]
Figure 4-16
Ground-Current Pulse Pattern in an Overcompensated System
For the faulty feeder, the ground-current pulse pattern is as follows:
•
When the clocking pulse is on, the capacitor is switched on, the ground current in the faulty feeder is
reduced, and the corresponding current pulse pattern is off.
•
When the clocking pulse is off, the capacitor is switched off, the ground current in the faulty feeder is
increased, and the current pulse pattern is on.
Table 4-10
Current Pulse Pattern in a Faulty Feeder
Clocking Pulse
Capacitor
Ground Current in the
Faulty Feeder
Current Pulse Pattern of the Faulty
Feeder
On
On
Reduced
Off
Off
Off
Increased
On
With the
Pulse-on duration
and
Pulse-off duration
parameters, you can 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 value or to similar values, there is a risk of failure. This is the case because the stage cannot distin-
guish the healthy and faulty feeders by only evaluating the ground current during a high-impedance ground
fault.
Number of Pulses for Operate (PulseTh Op.)
is defined as the number of pulses to be detected
within the pulse monitoring time.
Number of Pulses for Monitoring (PulseTh Mon.)
is defined as the number of pulses to be
considered for calculating the pulse monitoring time.
The pulse monitoring time is calculated via the following formula:
Pulse monitoring time =
Number of Pulses for Monitoring (PulseTh Mon.)
⋅ (
TPulse ON
+
TPulse OFF
)
If the measured
Pulse-on duration
and
Pulse-off duration
is equal to the configured
TPulse ON
and
TPulse OFF
, then a valid pulse is detected. If the number of detected pulses within the pulse monitoring
time reaches the setting of the
Number of Pulses for Operate (PulseTh Op.)
, then the ground
fault is detected.
Device Functions
4.1 Description
48
SICAM, Feeder Condition Monitor, Manual
E50417-H8940-C580-A4, Edition 03.2019