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C.2
Breaker Monitoring Featl.l'es
When the circuit breaker is comected to a DC control
source (Figure C. 1 ), it is possible to moritor the control
soorce impedance and the trip
co~
contint.ity as described
in the following sections. These moritorng features are not
applicable when the relay
is
used with an AC
control
source
(Figure C.2).
C.2.1
Trip Coil Continuity Monitoring
Trip
co~
conthlity is checked by moritoring the voltage
drop across the 52a contacts and the trip
co~
as shown n
Rgure C.1
.
This voltage drop is caused by the current
(awroximately 30
mA -
50
mA)
flowing through the red
"Breaker Closed" lamp. The position of the breaker
is
deter-
mi1ed by sensing the voltage drop across the 52b contacts
in series with the green "Breaker Open" lamp.
Note:
If
very low current LEOs are used as indicators,
adjustment
of
the resistances in
parallel
with the LEOs may
be
necessary to prevent them
beng
turned on by the cur-
rent nto the binary input (81)
of
the relay.
If trip
co~
monitoring
is
enabled
(TrpCoil
Cont at address
8303) and trip
coil
failure detection is set to "Yes"
(TrpCoiFail
at address 8304), a contnuity faiure
will
close the "Relay
disabled" contact
Siemens Energy & Automation, Inc.
Appendices
C.2.2
Trip Source Impedance Monitoring
The source impedance of the
control
voltage supply is mon-
itored by perbdcally drawing a fixed amount of current from
the supply and checking for excessive drop in the supply
voltage (see the Till Source Impedance sense crct.it in Fig-
ure C.1). This sense circuit
will
also pickup
if
the supply volt-
age drops below the ANSI lower lmit for trip voltage.
If
trip source impedance monitoring is enabled (TrpSrclmp
Cont at address 8301) and trip source failure detection
is
set
to "Yes"
(TrpSrciFail
at address 8302), a trp power sour03
failure
will
close the "Relay disabled" contact
45
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