Westinghouse
I.L.
41-911A
INSTALLATION
•
OPERATION
•
MAINTENANCE
INSTRUCT IONS
K-DAR DIRECTIONAL COMPARISON
BLOCKING SYSTEMS
IN TRODU CTION
This leaflet describes the overall functioning
of K--nar relays when used in conjunction with a
blocking channel (power line carrier, microwave or
pilot wire).
Detailed description of operation,
as well as setting and maintenance recommendations
for individual relays of the K-Dar directional com
parison blocking system are covered in the individual
relay instruction leaflets; the description here is
intended to supplement these relay instructions.
APPLICATION
Directional comparison blocking is employed to
eliminate delayed clearing of end-zone line faults;
thus, high speed, simultaneous clearing of all line
faults is accomplished. Protective relays energized
with current and potential from the protected line
are unable to trip both selectively and at high speed
for line faults near the remote station. By transmitting
a signal from the remote station when the fault is
external to the protected line, the l�cal relays are
blocked from tripping.
Without this additional
means of intelligence, local relay tripping must be
delayed for internal faults near the remote station,
to insure against undesired tripping when the fault
is on an adjacent circuit near the remote sta
t
io
n
.
This system can be utilized with minor differ
ences with either on-off or frequency shift type of
operation over pilot wire tones, microwave or power
line carrier channels.
Blocking of tripping is ef
fected by either keying on or shifting the transmitter
frequency.
*
These
instructions
contemplate
the
use of
separate primary and back-up relays, in line with
local back-up philosophies. Fig.
4
shows the details
of this arrangement. This contrasts to the previous
3-zone system where the zone
2
phase-distance units
provided carrier tripping as well as back-up. Never-
SUPERSEDES I.L.
41-911
*Denotes change from superseded issue.
theless,
the underlying principles described here
apply whether or not the back-up protection is inde
pendent or common with the primary protection. Of
course, the relaying complement will vary.
EQUIPMEN T COMPLEMEN T
K-Dar is the designation for a group of relays,
which are itemized below:
Directional Fault Detecting Relays
1 -Type KD Directional phase tripping unit,
consisting of:
1-Phase-to-phase
unit (ZP-#). which
operates for all three combinations of
phase-to-phase faults anywhere on the
protected line.
1-Three-phase unit (ZP-3¢),which operates
for 3 phase faults anywhere on the pro
tected line.
1 -Indicating contactor switch (ICS).
1 -Type KD-1 Directional Phase start unit, con
sisting of:
1
-Phase-to-phase unit (Z&-¢¢), set to
reach in the reversed direction to that
of ZP-cfxP.
1 -Three phase unit (
zs-
3 ¢), set to reach
in the reversed direction to that of ZP-3 ¢.
1 -Indicating contactor switch (ICS).
1 -Type KRD (or KRC, or KRP, or KRQ) Di
rectional ground
unit, consisting of:
1 -Directional unit, current polarized (D0c)
1 -Directional unit, voltage polarized (D0P)
1 -Instantaneous overcurrent unit (10)
1 -Indicating contactor switch (ICS)
EF F ECTIVE OCTOBER
1961
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