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Earth Leakage Monitor is one
important device used in DC power
systems like battery chargers AC-DC
converter systems, DC-DC converter
systems and DCDBs. Where an
independent DC power source is used,
the connections between transducers,
control units and DC power source
are very important. Monitoring and
signaling of earth faults is
essential in these situations. HBL
ELM enables quick detection of earth
faults so prompt corrective action
can be taken.
Features
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Earth leakage current
monitoring and protection of
DC power supply systems and
wiring with local and remote
alarm / annunciation |
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Every outgoing feeder can be
monitored individually |
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Reliable and rugged as any
short circuit at load end
will not affect the system
configuration |
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Low power consumption |
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Compact |
Principle of Operation
HBL make ELM (Earth Leakage Monitor)
works on the residual or
differential magnetising current
induced in a current transformer.
The two current carrying conductors
(positive and negative) are passed
through a ring type current
transformer. Under normal conditions
there is no residual current in the
CT as the current flow in the two
conductors is in opposite direction.
In the event of earth-fault the
current flowing through the
conductors will be different and
this difference gives rise to a
residual / magnetizing current in
the CT. The CT forms a part of
magnetic oscillator which would
oscillate symmetrically when there
is no magnetizing current in core.
The magnetizing current which is
proportional to the fault leakage
current is sensed and used to drive
an LED and a relay through a
comparator for local and remote
(potential free contacts)
annunciation.
The ELM is provided with a test
button which can be used to check
the correct functioning of the
device during operation.
Applications
HBL’s Earth Leakage Monitors can be
widely used in Petro-chemical
industries, Process industries and
Substations.
Installation Requirements
Systems with floating power supply
or centre of power supply grounded /
earthed are compatible
with these ELMs. Systems with either
positive and negative earthing are
not compatible.
In accordance with its policy of
continuous improvement the company
reserves the right to change
specifications and designs without
notice. Illustrations, data,
dimensions and weights given in this
brochure are for guidance only and
cannot be held binding on the
company. |
