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Due to RMS continuous product improvement policy this information is subject to change without notice. 1S25/Issue F/07/03/2011 - 1/9
Features
Four independent arc fault
tripping zones
1 or 2 arc fault sensors per
zone allowing up to 8 arc fault
sensors per 1S25 module
Trip indication LED for each arc
fault monitoring zone
Non volatile memory ensures
last recorded alarm states are
restored on power up
Nine (9) high speed arc fault
tripping duty output contacts
(Set for latching or self reset)
Zone segregated or common
tripping output configuration
Continuous arc sensor
supervision with sensor fail
LED for each zone
Wide range status input to
block arc fault monitoring
Front panel reset button &
status input
Self supervision watchdog with
healthy LED & alarm contact
Built in test sequence
Wide range auxiliary supply
Introduction
Medium voltage switchgear is a key
element in the power supply chain.
Existing protection systems operate
effectively under most circumstances, but
they are too slow to handle arcing short
circuits.
Arcing faults can occur as a result of
insulation breakdown due to equipment
age & / or poor maintenance.
The degree of damage caused by arcing
depends principally on the duration of the
arc. If an arc lasts only 100ms, the
switchgear needs to be checked & the
insulation resistance measured before
power can be re-established. With a
200ms arc, the power supply will be
interrupted; the switchgear must be
checked; power is re-established only
after minor repairs. In the event of a
500ms arc the supply is interrupted, metal
parts of the switchgear are destroyed &
poisonous gases are emitted. A 1s arc
destroys most of the switchgear & may
cause a fire, injury to personnel & damage
to property.
Technical Bulletin
1S25
Arc Fault Monitor – 4 Zones, 8 Sensors
1S25 depicted in a 2M28-S draw out case
with custom alarm text engraving
ARC Fault Protection
Made in Australia
Arc fault protection is a relatively new technique employed for the fast clearance of arcing
faults on low voltage panels, MCC’s, BUS bars & within metal clad switchgear &
associated cable boxes. The arc is detected using an optical sensor & the signal input to a
protection device which also monitors the load current on the system. A trip signal can be
achieved in less than 10ms using arc detection only or within 15ms when using
overcurrent check. This is considerably faster than a traditional IDMT overcurrent relay &
provides additional protection from the onset of arcing faults with relatively low fault
currents.
Arguably the greatest risk of arc fault damage exists at the CB cable termination & in the
CB chamber itself due to the slow clearance times of the IDMT feeder protection. The CB
cable termination is particularly at risk to ingress of moisture & rodent damage.
The problem of arc faults is most prevalent in older metal clad switchgear which already
has operational protection systems. The 1S25 Arc Fault Monitor has therefore been
designed for the following applications:
EXISTING SWITCHGEAR
Where a requirement exists to retrofit arc fault protection to metal clad switchgear utilizing
the existing overcurrent protection relay;
NEW SWITCHGEAR
Where a requirement exists to install arc fault protection to new switchgear for integration
with the customer preferred overcurrent feeder protection relay;
LOW VOLTAGE PANELS
Arc fault protection may also be applied on low voltage panel control boards & motor
control centers (MCC’s).
