The 1S20 is designed to monitor remote optical sensors that to
respond to the flash of light emitted during the incidence of an
arcing fault. Onset of the light flash & detection by the sensors
occurs in a few ms.
The 1S30 is an electrically wired point sensor suitable for
application in discrete compartments in metal clad switchgear
and cable ducts. When an arc is detected, the resistance
presented by the 1S30 drops to a level where the current flow
increases to approximately 20mA. This increased current flow is
instantaneously detected by the 1S20 & its trip output contacts
closed. Refer to the 1S30 Technical Bulletin for further details.
Figure 2: 1S30 Point Sensors
Low Current Arcing Faults
an occur at low current levels and
it is possible for
the over
-
current starter element to be set above this level. To
avoid this problem & obtain very fast clearance (<10ms),
of an arc
fault, the 1S20 arc fault trip contact may be wired directly to the
breaker operate coil. It should be noted that this method may
lead to reduced system security.
Independent Trip Output Contacts
The 1S20 may be set using configuration switch 3 for both trip
output contacts to pick up when an arc is detected by any sensor
input. Alternatively arc sensor 1 can be linked to trip contact 1 &
arc sensor 2 (& 3 if fitted), to trip contact 2. This function may be
applied where an arc fault detected in the cable box is directed to
trip the feeder circuit breaker while an arc fault in the BUS
chamber is
to be directed to trip the BUS.
Arc Fault Tripping Using Current Check
operation of a tripping scheme usually results in reduced
system security. The arc detection method can however,
combine the 1S20 optical detection technique with a traditional
overcurrent method to maximize system security particularly for
BUS bar protection schemes. Both conditions must coexist for
the trip condition to be met as depicted in figure 3.
Figure 3:
Key components required to implement an Arc Fault Protection
scheme with an overcurrent check stage to enhance system
security.
The applicati
on examples in figures 4 to 8
utilize this concept for
enhanced system security in
that both the 1S20 AND
the OC 50
starter contact must be picked up for a CB trip signal to be
initiated.
As the arc fault trip contact picks up considerably faster
than the overcurrent relay starter element, the CB trip time will
be dictated by the overcurrent relay performance.
Arc Sensor Continuously Picked Up
High ambient light levels may cause a 1S30 to be continuously
picked up. This condition could occur for example if the CB cable
box cover was left open in very high ambient light level
conditions.
To avoid possible mal operation due to this condition, the 1S20
is designed to automatically disable the arc fault tripping function
if any sensor input is picked up for >10s. The 1S20 alarm contact
will be set & the front LED flash alternate orange & red until the
ambient light level problem is corrected. The 1S20 will then
perform an arc sensor test function & automatically reset.
arc trips)
A delay of 2s is required to reset the 1S20 after an initial arc
sensor trip. Subsequent arc detection will cause the trip output
contacts to re
-operate.
Type:1S20K1 [C] Vx: 48V DC
Serial No: 126578
1S20 Arc Fault Monitor
ARC FAULT TRIP INITIATE
CB ARC FAULT
MONITORSENSOR
VER-
URRENT RELA
3 Pole OC + EF
RESET / TEST
System Functi oning
Arc Fault Trip
System Service
DC Fail
GREEN:
RED:
ORANGE:
DARK:
