Trip And Operation Indicators; Test Provisions; Discriminator (Making Current Release) - Eaton Cutler-Hammer Digitrip RMS 510 Trip Unit Instructions Manual

I.L. 29-8858
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Fig. 3 Digitrip RMS 510 Block Diagram with Breaker In terface
The microcomputer, in cyclic fashion, repeatedly scans
the voltage values across each calibrating resistor and
enters these values into its Random Access Memory
(RAM). These data are used to calculate true RMS cur­
rent values, which are then repeatedly compared with the
protection function settings and other operating data
stored in the Read Only Memory (ROM). The software
program then determines whether to initiate protection
functions, including tripping the breaker through the low
energy trip device (Flux Transfer Shunt Trip or Direct Trip
Actuator) in the circuit breaker.

3.2 Trip and Operation Indicators

The LEOs, shown in Figs.
the trip unit, light "RED" to indicate the reason for any
automatic trip operation. As indicated in Figs. 2.1-2. 6,
each LED is strategically located in the related segment
of the time-current curve depicted on the face of the trip
unit. The reason for trip is identified by the segment of the
time-current curve where the LED is lighted "RED". Fol­
lowing an automatic trip operation, the back-up battery,
continues to supply power to the LEOs as indicated in
Figs. 3 and 6. To check the status of the battery, see Sec­
tion 6.
Push the "Trip Reset" button shown in Fig. 1, to turn "Off'
the LEOs following a trip operation.
A green colored LED, as shown in Fig. 1, indicates the
operational status of the trip unit. Once the load current
through the circuit breaker exceeds approximately 10%
of the frame/current sensor rating, the green LED will
flash "On" and "Off" once each second, to indicate the trip
unit is energized and operating properly.
Note: If the LED is steadily "GR EEN", i.e. n ot flash­
ing, the trip u n it is n ot ready.
Effective
May 1997
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and 2.1-2. 6, on the face of
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3.3 Test Provisions (See Section 5.0)

3.4 DIScriminator (Making Current Release)

(For Types LS and LSG trip units only.)
When the Digitrip RMS 510 Trip Unit is not equipped with
an adjustable instantaneous protection setting, i.e., types
LS or LSG, a making current release (or DIScriminator)
circuit is provided. This circuit will prevent the circuit
breaker from being closed and latched-in on a faulted cir­
cuit. The non-adjustable release is pre-set at eleven (11)
times the installed rating plug current (In)·
The making current release is enabled only for the first
( 1
ten 0) cycles following an initial circuit breaker closing
operation, provided the load current exceeds approxi­
mately 10% of the circuit breaker frame (or current sen­
sor) rating. Should the load current through the circuit
breaker drop to less than the 10% value, the release will
reset. The release, once reset, will remain enabled until
the load current passing through the circuit breaker has
exceeded the 10% value for 10 cycles. The making cur­
rent release will trip the circuit breaker instantaneously.
In the event the breaker is intended to close (but not to
trip out again) into a circuit whose current could initially
be higher than 11 x In, it is possible to make the DIScrim­
inator inactive. If the breaker does close onto a fully rated
fault current, when the DIScriminator is inactive, the
breaker will wait for the full short-time delay setting before
it trips. The DIScriminator (making current release) can
be made inactive by turning the "OVERRIDE/" setting
switch (nearest the bottom edge of the trip unit) from the
"DIS" position, to the "[BLANK]" position. (See Figs. 2. 2
and 2.5.)
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