Westinghouse Digitrip RMS 500 Instructions Manual Download Page 17

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3.3 Test Provisions

An i ntegral test panel, i ncluding a test selector switch and test

and reset pushbuttons, is provided to test the circuit breaker
i n either a TRIP or NO-TRI P test mode u nder qualified condi

tions. See Section 5.

For bench testing of the trip unit alone or of the trip unit whi l e
it is insta l led i n  t h e  circuit breaker, a n  optional Auxi l iary Power
Module  (Cat.  No.  PRTAAPM)  as  shown  in  Fig.  7  is  available.

This Auxiliary Power Module, which operates from a separate

1 20 Vac supply, may also be used when a drawout type circuit
breaker is i n any of its fou r cell positions, i .e., "Connected",

"Test", "Disconnected" and "Withdrawn" (or "Removed.")

3.4 Making Current Release (Discriminator)

When the DIGITRIP RMS 500 Trip Unit is not equipped with an
adjustable i n stantaneous protection setti ng, i .e., types LS or

LSG, a making current release (or d i scrim inator) circuit is pro

vided. This circu it wi l l prevent the circuit breaker from being

closed and latched-in on a faulted circu it. The non-adjustable

release is pre-set at eleven ( 1 1 ) times the i n stalled rating plug
a mpere rating On l·

The making current release is a rmed only for the first ten ( 1 0)

cycles fol lowing an i n itial ci rcuit breaker closing operation with
a load current exceeding approximately 20% ofthe circuit breaker
frame or sensor rati ng. Should the load cu rrent through the
circuit breaker drop to a value less than this, the release will

re-arm. The release, once armed, will  remain armed u ntil the
load  current  passing  through  the  circuit  breaker  exceeds
approximately 20% for  1 0  cycles. Any trip operation  i nitiated
by  the  making  current  release  will  trip  the  circuit  breaker
i n stantaneously.

3.5 Instantaneous Override

In addition, when the Digitrip RMS 500 Trip Unit is not equipped

with a n adjustable i n stantaneous setting, i.e., types LS o r LSG,
a high-set non-adjustable instantaneous override trip circuit is
provided. This h i g h level tripping action is pre-set to a specific
value that reflects the short time withstand rating of the circuit

breaker i n which the trip unit is i n stalled. Specific values vary

between ci rcuit breaker types and ratings. For specific i nfor
mation, refer to the supplementary leaflets and/or time-current

curves referenced in Sections 9 . 1 and 9.2.

3.6 Zone Interlocking

As  indicated  in  the  block diagram  in  Fig. 3, zone interlock sig
nals are  provided.  For Digitrip  R M S  500  Trip  U n its equ i pped
with  either  ground  fau lt  or short time  protection functions or
both, separate  zone  i nterlocking  circuits  are  provided.  When
util ized, these i nput/output signals  must  be connected  i n  the
ulti mate equipment assembly in l i ne with detai l s  provided with
the specific circuit breaker connection d iagrams supplied with
the circuit breaker and referenced in Sections 9.1  and 9.2. Sim
i larly, if the zone i nterlocking function is chosen not to be used,
defeater  connections  on  each  circu it  must  be  added  as i l lus

trated in the same referenced diag rams.

4.0 Protection Settings

4.1 General

Prior to  placing  any  circu it  breaker  in  operation,  a l l  ava i lable
protection  settings  shou l d   be  set  using  values  as  recom
mended  by the specifying eng ineer responsible for the i n stal
lation.  The  n u m ber of  settings that  must  be  made wi l l   be  a

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Typical Cause of Trip LEOs

Located on Front Panel

Multiplexer

(MUX)

Unit

Operating Status

Indicator