INSTALLATION
INSTRUCTIONS
TYPE HZ.HZ-4 OR HZM PLATE-KEYED
INTRODUCTION
The
high-speed clearing of faults on trans
mission lines
is
recognized as necessary for
good
system operation.
tection
is
provided
differential
relaying
the two
ends
of
the llne are compared to de-
termine
whether
the
section
or
external
This
assures
simultaneous
breakers,
which
is
desirable from the stand
points
of stability,
quick
reclosing,
and miniffium damage to equip
ment.
For many lines,
r.J J st praC'tico.l and reliable medium for compaY'-
ing
the
conditions
at
line.
This system of protection uses relays opera
ting on current and voltage at each end ::,f
line
to detect and determine the direction
faults.
Carrier is started by fault detectors
when
a fault occurs.
of
a line section indicates that the fault is
external
and
the
breakers
tripped.
At
the same
will be flowing into
the other end of the line
as
though
the
fault
Under this
condition,
at
the
end where
power is flowing out of the
section
will
operate
mtssion of
a
carrier signal which is received
at
both
ends and prevents the relays at both
ends
from
tripping
for all external faults.
For internal faults,
power will not be flowing
cut
at either end and carrier will be stopped
by
operation
of
the directional elements at
both
ends
to permit simultaneous tripping of
both breakers.
The
carrier
scheme
SUPERSEDES I. L. 41-904
*Denotes change from superseded issue.
•
CARRIER RELAYING
The best overall pro
by
the method known as
in which conditions at
fault
in the line
is
to
the protected zone.
tripping
of the
continuity
of service,
carrier relaying is t�e
tJF
two ends
of
Uw
of
Fault power flowing out
not
be
should
instant,
however,
powPr
were
in
the section.
the directional relays
to continue the trans
the time-
utilizes
OPERATION
•
distance
characteristics
HZM
:Jr
relay to provide hi,;h speed simultane
ous tripping with carrier
type
distance
protection
in
or
out
of service.
HZ, HZ-4
HZM
the type
or
pendently
of carrier.
The second element trips
at high speed for faults in the section bec ause
the carrier tripping contacts short around the
synchronous
timer.
These
close
immediately
if the fault is within the
se�tic,n,
but are held open by carrier to block
tripping
if
the
fault is beyond the section
being
protected.
This
vides
sim"",ltanec�us
tripping
line
section.
The
synchronous timer is
with
in
conr:ection
the second impedance ele
ment
tn
provide
back-up protection for
second
zone section.
the
third
element
is independent of carrier
and operates with time delay for
up
pr0tection.
The
supervised
by
the
second impedance element,
together
with
the
third impedance element,
control
the
transmission
ditional interlocks can be included to prevent
tripping
of
any
of the elements
back-up
protection)
due to out-of-synchronism
surges.
Thus,
besides
protection,
this
system
high
speed and time delay back-up protection.
COMPONENTS OF
COMPLETE EQUIPMENT
An
outline
of
the
terminal of
transmission line is as follows:
a
l.
A
set
of
relays,
rent
and
voltage
of the line,
determine the direction of faults,
breaker
if the fault falls within the
protection,
and to control the transmission
carrier
for external faults.
EFFECTIVE AUGUST 19 55
I. L. 41-904 A
MAINTENANCE
HZ, HZ-4
of the type
in service,
and step
with carrier either
The first element of
relay operated
inde
tripping contacts
arrangement thus pre-
over the entire
�sed
the
The tripping circuit of
overall back-
directional
element,
of
carrier.
Ad-
(
carrier or
the
carrier
pilot
inherently provides
equipment used at each
operating
0n the cur
to detect
and
to
trip the
zone of
cf
One
terminal of
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