Long Delay Time Setting; Short Delay Current Setting; Short Delay Time Setting - Eaton Digitrip 520 Instructional Leaflet

Digitrip models 520, 520i; and 520M, 520Mi,
520MC, 520MCi trip units for use only in
Magnum and Magnum DS circuit breakers
LNng dtlay oimt stooing
There are eight available long delay time settings, as illustrated in
Figurt 31, ranging from 2–24 seconds. These settings are the total
clearing times when the current value equals six times (I
Long Delay Time
2 Seconds at 6 x l
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Figurt 31. LNng Dtlay Timt Stooings
N Notse: In addition to the standard long delay protection element, trip units
also have a Long Time Memory (LTM) function, which protects load circuits
from the effects of repeated overload conditions. If a breaker is reclosed soon
after a long delay trip, and the current again exceeds the long delay setting,
(I ), the LTM automatically reduces the time to trip to allow for the fact that
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the load circuit temperature is already higher than normal because of the
prior overload condition. Each time the overload condition is repeated, the
LTM causes the breaker to trip in a progressively shorter time. When the load
current returns to normal, the LTM begins to reset; after about 10 minutes
it will have reset fully, so the next long delay trip time will again correspond
to the setting value. In certain applications, it may be desirable to disable
the LTM function. Open the test port located at the lower left-hand front of
the trip unit and use small, long nose pliers to move the LTM jumper inside
the test port (see Figurt 32) to its inactive position. (The LTM function can
be enabled again at any time by moving the LTM jumper back to its original
active position.)
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Available
Settings
2, 4, 7, 10,
12, 15, 20, 24
Seconds at
6 Times
Long Delay
Setting (l )
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6 x l
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Instructional Leaflet IL70C1037H05
Test Kit
Notch
LTM Active
Figurt 32. LNng Timt MtmNry (LTM) Jumptr
The action of the LTM must be considered when performing
multiple long delay time tests (see Section 5).
ShNro dtlay currtno stooing
There are eight available short delay current settings, as illustrated
in Figurt 31. Seven settings are in the range from 2–10 times (I
(Remember: (I ) is the long delay current setting.) The maximum
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value M1 is based on the ampere rating of the circuit breaker and is
listed in Note 4 of Tablt 1.
2.0, 2.5, 3.0. 4.0, 5.0, 6.0, 8.0, 10.0, M1
Short Delay Setting
2 x l
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M1 Value is Specified on Rating Plug
Figurt 33. ShNro Dtlay Currtno Stooings
ShNro dtlay oimt stooing
As illustrated in Figurt 34, there are two different short delay
response curve shapes: fixed time (FLAT) and I
The shape selected depends on the type of selective coordination
chosen. The I 2 t response curve will provide a longer time delay for
current below 8 x I than will the FLAT response curve.
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eaton corporation www.eaton.com
Effective October 2009
Digiorip Ttso Kio PNro
Test Kit
Connector
(Bridging)
LTM Inactive
Connector
(Storage)
(Also Recommended
Position for Field Testing)
Available Settings
In Multiples of
Long Delay Setting (l
t.
2
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)
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