User`s guide

Volume 3—Power Distribution and Control Assemblies CA08100004E—November 2013 www.eaton.com V3-T9-227
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9.4
Metering Devices, Protective Relays, Software and Connectivity
Protective Relays
Overcurrent Protection
The EDR-3000 provides
complete three-phase and
ground protection with
separate elements and
settings. The relay can be
used with CTs from 1 to
50,000A of primary current
and 1 or 5A of secondary
current. The CT ratio can be
set independently for phase
and ground, allowing the
ground element to be
connected in either the
residual or the separate
ground CT configuration,
shown on below.
Separate Zero Sequence
Ground CT Connection
Zone Selective Interlocking
(Phase and Ground)
Note: Refer to the Ordering
Information and (Catalog Ordering
Information) for optional features,
see Page V3-T9-229.
Zone Selective interlocking
is a protection function to
minimize equipment damage
resulting from a phase or a
ground fault in an area where
long time and/or short time
delay is in use.
When the “Ground Zone
Interlocking” feature is
utilized, an immediate trip is
initiated when the fault is in
the breaker’s zone of
protection, regardless of its
preset time delay. When the
“Phase Zone Interlocking”
feature is utilized, the time
overcurrent elements work
as follows. The instantaneous
phase element will initiate an
immediate trip when the fault
is in the breaker's zone of
protection, regardless of its
preset time delay. For the
time overcurrent phase
element, the current sensed
by the EDR-3000 must
exceed 1.5 times the pickup
setting for the zone selective
interlocking to initiate an
immediate trip signal when
the fault is in the breaker’s
zone of protection.
Upstream EDR-3000
protected breakers are
restrained from tripping
immediately by an
interlocking signal from the
downstream EDR-3000 relay.
This interlocking signal
requires only a pair of
wires from the downstream
breaker to the upstream
breaker. It provides standard
coordinated tripping when
the fault is located outside
the zone of protection.
In the sample zone
interlocking system shown
below, circuit breakers A,
B and C are equipped with
EDR-3000 overcurrent relays.
Fault Location Zone 3
Note: For the time overcurrent
phase element, the current
sensed by the EDR-3000 must
exceed 1.5 times the pickup
setting for the zone selective
interlocking to initiate an
immediate trip signal when
the fault is in the breaker's zone
of protection.
If a fault occurs at a point
in Zone 3, the EDR-3000
of downstream breaker C
senses the fault and sends
a restraining signal to the
upstream EDR-3000 of
feeder breaker B. Having
received this signal, the
EDR-3000 of feeder breaker
B withholds its trip command.
As a result, only downstream
breaker C is tripped.
Fault Location Zone 2
Note: For the time overcurrent
phase element, the current
sensed by the EDR-3000 must
exceed 1.5 times the pickup
setting for the zone selective
interlocking to initiate an
immediate trip signal when the
fault is in the breaker’s zone
of protection.
If a fault occurs at a point in
Zone 2, the EDR-3000 of
feeder breaker B senses the
fault and sends a restraining
signal to the upstream EDR-
3000 of main breaker A. The
EDR-3000 of the downstream
breaker C does not see this
fault since it is situated on the
downstream side of the fault.
As a result, the EDR-3000 of
downstream breaker C does
not send a restraining signal
to the EDR-3000 of feeder
breaker B. Since it did not
receive a restraining signal
from the EDR-3000 of
downstream breaker C, the
EDR-3000 of feeder breaker
B identifies that the fault is in
Zone 2 and immediately trips
feeder breaker B, regardless
of its time setting.
Fault Location Zone 1
Note: For the time overcurrent
phase element, the current
sensed by the EDR-3000 must
exceed 1.5 times the pickup
setting for the zone selective
interlocking to initiate an
immediate trip signal when the
fault is in the breaker's zone of
protection.
If a fault occurs in Zone 1,
no restraining signal is
received by the Digitrip
of main breaker A. As a
result, main breaker A is
immediately tripped by its
EDR-3000 overcurrent relay,
regardless of its time setting.
Sample Zone Selective Interlocking System
CB-52
a
b
c
GND
EDR-3000
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50G/51G