HKB SINGLE POLE
The back-up relays either phase or ground
trip all three poles of the breaker for all
types of faults within their range.
These
relays energize the type MG relay (designated
MGT
)
which in turn trips the three phase
poles.
The instantaneous elements of
the
back-up
relays are connected
thru the type
TG-1 Time Delay relay.
This relay has a time
setting of 5 to 15 cycles after which it
energized
MGT
coil to trip
all
1:hree poles.
This time delay prcrvldes an opportunity for
the carrier relays to trip one pole if the
fault is single line to ground.
When carrier
single pole relaying is out of service, a con
tact on the type W carrier switch shorts out
this time delay relay.
A
telephone type relay designated X3 in the
type H�S relay is used to prevent the unfault
ed trip circuits from being energized moment
arily by the transient response of the type
H�S element,
when the fault current disap
pears.
The break
contact of
X3
is connected
in each of the three phase-�elector trip
paths.
The X3 contact opens in about 3-4
c�cles and closes instantaneously.
This con
tact does not open up the trip coil current on
the faulted phase since this has been sealed
in previously.
The X3 relay as well as the types
JD
and
SGG
relays are energized either by the type
HKB
relay trip circuit thru the contactor switch
or when any one or two poles only are open.
The SGG relay shorts out the coils of the
ground back-up relay type CWC or CWP.
This is
necessary only
if the relay is set sensitively
with a short time and might operate before the
opened pha�e
is
reclosed.
The type
JD
timing
relay
limits the time which the line can
oe
operated with one or two phases open and thus
serves a back-up ground relay.
The operatim1 of the carrier control cir
cuits are the same as in the standard carrier
scheme.
Automatic immediate reclosing is provided
thru high speed breaker switches after one
pole of the breaker is opened, but if all
three poles open immediate reclosure may or
may not be
conditions.
in figure
permitted depending upon system
The reclosing scheme is shown on
5, and operates as follows:
For
I.L. 41-600.7
a phasc;
pole, the
A-to-ground fault which trips phase
A
high speed breaker switch
52bb,
will close to
immediately reclose this pole.
The breaker auxiliary closing relay closes its
contact
52X to energize 79X-0 coil.
This is
the operating coil of the toggle element in
the type SGR-12 reclosing relay.
Contact 79X
in the closing circuit is thus opened to pre
vent further reclosing of pole A.
Another
contact on the toggle element, 79X, is closed
to en�gize the reset motor (79M) of the type
SGR-12 relay when the breaker pole closes as
indicated by the closing
of 52a.
If
the
breaker
stays closed the motor contact 79M
closes after a suitablA delay to energize the
toggle relay reset coil 79X-O.
This coil re
sets the two 79X contacts which in turn de
energizes
the timing motor and resets the
closing circuit for a subsequent trip.
A similar
sequence
of operations will take
place for the
are opened by
relays.
It is
other breaker poles when they
operation of the protected
to be noted that the manual
control
switch and the back-up relays all
energize a master tripping relay MGT.
Make
contacts on MGT operate the toggle element
79X-O of the type SGR-12 recloser to lock out
and block reclosure until after the breaker
poles are manually reclosed.
Reclosing is
also blocked when carrier is out of service by
the type
W carrier switch.
If instantaneous
reclosing is to be prevented for internal
phase faults tripped by carrier, then another
type MG relay is required.
This relay is
energized by CSl contactor switch of the t�e
HZM-3 relay.
This type MG �elay will trip all
three breaker poles and energize 7�X to lock
out and block recloser of all thrAe breaker
poles.
The manual closing switch, 101-C, operates
a master closing relay designated MG-Cl.
The
contacts of this relay energize the closing
circuit of each of the three poles.
In the above
the breaker
discussion it was assumed that
poles remained closed after the
first reclosure indicating that the fault was
not permanent.
If the arc restrikes or the
fault is
solid, then the protective relays
will operate to retrip the breaker poles
again.
This time one or more of the 79X re
closing contacts of the type SGR-12 recloser
3
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