ABB IRP Manual

ABB Automation Inc.
Substation Automation and Protection Division
Coral Springs, FL 33065
Instruction Leaflet
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is desired
by purchaser regarding this particular installation, operation or maintenance of this equipment, the local ABB
Power T&D Company Inc. representative should be contacted.
Printed in U.S.A.
Directional Overcurrent
41-133S
Ground Relays
Types IRP, IRC and IRD
Supersedes I.L. 41-133R, Dated August 1998
()Denotes Changed Since Previous Issue
Effective: October 1999
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely,
inspect the contacts to see that they are clean
and close properly, and operate the relay to
check the settings and electrical connections.
1.0 APPLICATION
These relays are ground directional overcurrent
relays which are used for the protection of transmis-
sion lines and feeder circuits. Both the time overcur-
rent and instantaneous overcurrent units are
directionally controlled.
The type IRP relay is potential polarized. The type
IRC relay is current polarized. The type IRD relay is a
dual polarized relay which can be polarized from a
potential source, from a local ground source or from
both simultaneously.
2.0 CONSTRUCTION AND OPERATION
The various types of relays consist of a directional
unit or units (D), an auxiliary switch (CS-1 or a tele-
phone relay TR-1), a time-overcurrent unit (CO), an
instantaneous overcurrent unit (I), an instantaneous
overcurrent unit transformer, and two indicating con-
tactor switches (ICS/I) and (ICS/T). The principle
component parts of the relays and their locations are
shown in Figures 1 through 6, starting on page 19.
2.1 TIME-OVERCURRENT UNIT (CO)
The electromagnets for the types IR-5, IR-6, IR-7,
IR-8 and IR-9 relays have a main tapped coil located
on the center leg of an “E” type laminated structure
that produces a flux which divides and returns
through the outer legs. A shading coil causes the flux
through the left leg to lag the main pole flux. The
out-of-phase fluxes thus produced in the air gap
cause a contact closing torque.
The electromagnet for the type IR-2 and IR-11 relays
has a main coil consisting of a tapped primary wind-
ing and a secondary winding. Two identical coils on
the outer legs of the lamination structure are con-
nected to the main coil secondary in a manner so that
the combination of all the fluxes produced by the
electromagnet result in out-of-phase fluxes in the air
gap. The out-of-phase air gap fluxes produced cause
a contact closing torque.
The dc indicating contactor switch is a small clapper
type device. A magnetic armature, to which
leaf-spring mounted contacts are attached, is
attracted to the magnetic core upon energization of
the switch. When the switch closes the moving con-
tacts bridge two stationary contacts, completing the
trip circuit. Also during this operation two fingers on
the armature deflect a spring located on the front of
the switch, which allows the operation indicator target
to drop.
The front spring, in addition to holding the target, pro-
vides restraint for the armature and thus controls the
pickup value of the switch.
2.2 DIRECTIONAL UNIT (D)
The directional unit is a product induction cylinder
type unit operating on the interaction between the
polarizing circuit flux and the operating circuit flux.
Mechanically, the directional unit is composed of four
basic components: A die-cast aluminum frame; an
!CAUTION

41-133S
2
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
electromagnet; a moving assembly; and a molded
bridge.
The frame serves as the mounting structure for the
magnetic core. The magnetic core which houses the
lower pin bearing is secured to the frame by a locking
nut. The bearing can be replaced, if necessary, with-
out having to remove the magnetic core from the
frame.
The electromagnet has two series-connected polariz-
ing coils mounted diametrically opposite one another;
two series-connected operating coils mounted dia-
metrically opposite one another; two magnetic
adjusting plugs; upper and lower adjusting plug clips,
and two locating pins. The locating pins are used to
accurately position the lower pin bearing, which is
mounted on the frame, with respect to the upper pin
bearing, which is threaded into the bridge. The elec-
tromagnet is secured to the frame by four mounting
screws.
The moving element assembly consists of a spiral
spring, contact carrying member, and an aluminum
cylinder assembled to a molded hub which holds the
shaft. The shaft has removable top and bottom jewel
bearings. The shaft rides between the bottom pin
bearing and the upper pin bearing with the cylinder
rotating in an air gap formed by the electromagnet
and the magnetic core.
The bridge is secured to the electromagnet and
frame by two mounting screws. In addition to holding
the upper pin bearing, the bridge is used for mount-
ing the adjustable stationary contact housing. The
stationary contact housing is held in position by a
spring type clamp. The spring adjuster is located on
the underside of the bridge and is attached to the
moving contact arm by a spiral spring. The spring
adjuster is also held in place by a spring type clamp.
With the contacts closed, the electrical connection is
made through the stationary contact housing clamp,
to the moving contact, through the spiral spring out to
the spring adjuster clamp.
2.3 AUXILIARY SWITCH (CS-1 OR TR-1)
The CS-1 switch is a small solenoid type dc switch. A
cylindrical plunger, with a silver disc mounted on its
lower end, moves in the core of the solenoid. As the
plunger travels upward, the disc bridges the silver
stationary contacts.
The TR-1 switch is a telephone relay. A tapped resis-
tor is used to enable one to use the auxiliary switch
on a 24, 48, 125 or 250 volt dc system connected per
Figure 26, page 40. The operation of the CS-1 or
TR-1 switch is controlled by the directional unit (D)
which in turn directionally controls the time-overcur-
rent unit (CO). When sufficient power flows in the
tripping direction, the auxiliary switch operates and
bridges the lag coil of the time-overcurrent unit (CO)
permitting this unit to operate.
2.4 INSTANTANEOUS OVERCURRENT UNIT (I)
The instantaneous overcurrent unit is similar in con-
struction to the directional unit. The time phase rela-
tionship of the two air gap fluxes necessary for the
development of torque, is achieved by means of a
capacitor connected in series with one pair of pole
windings.
The normally-closed contact of the directional unit is
connected across one pair of pole windings of the
instantaneous overcurrent unit as shown in the inter-
nal schematics. This arrangement short-circuits the
operating current around the pole windings, prevent-
ing the instantaneous overcurrent unit from develop-
ing torque. If the directional unit should pick up for a
fault, this short-circuit is removed, allowing the
instantaneous overcurrent contact to commence
closing almost simultaneously with the directional
contact for high speed operation. Total operating
time is shown in Figures 23 (page 38) and 24 (page
38).
2.5 INSTANTANEOUS OVERCURRENT UNIT
TRANSFORMER
This transformer is of the saturating type for limiting
the energy to the instantaneous overcurrent unit at
higher values of fault current and to reduce ct bur-
den. The primary winding is tapped and these taps
are brought out to a tap block for ease in changing
the pick-up of the instantaneous overcurrent unit.
The use of a tapped transformer provides approxi-
mately the same energy level at a given multiple of
pickup current for any tap setting, resulting in one
time curve throughout the range of the relay.
Across the secondary is connected a non-linear
resistor known as a varistor. The effect of the varistor
is to reduce the voltage peaks applied to the overcur-
rent unit and phase shifting capacitor.

41-133S
3
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
3.0 CHARACTERISTICS
The time characteristics of the directional overcurrent
relays are designated by specific numbers as indi-
cated below (e.g., IRD-8).
Time Characteristics Designation
Short Time . . . . . . . . . . . . . . . . . . . . 2
Long Time . . . . . . . . . . . . . . . . . . . . 5
Definite Time. . . . . . . . . . . . . . . . . . . 6
Moderately Inverse Time . . . . . . . . . . . 7
Inverse Time . . . . . . . . . . . . . . . . . . . 8
Very Inverse Time . . . . . . . . . . . . . . . 9
Extremely Inverse Time . . . . . . . . . . . 11
The relays are available in the following current
ranges:
Instantaneous Overcurrent Unit
Time Overcurrent Unit
The tap value is the minimum current required to just
close relay contacts.
The time vs. current characteristics for the time-over-
current unit are shown in Figures 16 to 22 (page 31
to page 37). These characteristics give the contact
closing time for the various time dial settings when
the indicated multiples of tap value current are
applied the relay.
4.0 TIME CURVES
The times curves for the IRD relay are shown in Fig-
ures 23 (page 38) and 24 (page 38). Figure 23 con-
sists of three curves which are:
1. Directional Unit opening times for current
and voltage polarized.
2. Directional Unit closing time for current and
voltage polarized.
3. Directional Unit closing time for 1 volt, volt-
age polarized.
Figure 24 shows the instantaneous overcurrent unit
closing time.
The voltage polarized curve B begins to deviate from
curve A for less than 5 volts.
Both the directional unit and the overcurrent unit
must operate before the trip circuit can be completed.
Hence, the unit which takes the longer time to oper-
ate determines when the breaker will be tripped. The
overcurrent unit contacts cannot operate until the
back contacts of directional unit open; therefore, the
total time for overcurrent unit to operate is its closing
time given in Figure 24 (page 38) plus the directional
unit opening time given in Figure 23. The total clos-
ing time for the directional unit is given in Figure 23.
The two examples below will serve to illustrate the
use of the curves.
Example 1: Using the formulas and definition of sym-
bols on Figure 23,
Let: Ipol = 2 amps.
Iop = 2.31 amps.
TapValue(T) = 0.5 amp.
φ-40°= 0°
(For timing unit, assume CO-9 with 1/2 time
dial setting)
For current polarized relay:
Referring to Figure 23 at multiples of product pickup
of 18.5, the directional unit operating time is about 11
ms, and the closing time for this unit is 56 ms.
Range Taps
0.5-2 Amps 0.5 0.75 1.0 1.25 1.5 2
1-4 1.0 1.5 2.0 2.5 3.0 4.0
2-8 234568
4-16 4 6 8 9 12 16
10-40 10 15 20 24 30 40
20-80 20 30 40 48 60 80
Range Taps
.5-2.5 0.5 0.6 0.8 1.0 1.5 2.0 2.5
2-6 2 2.5 3 3.5 4 5 6
4-12456781012
MPP lop lpol φ40°–()cos
0.25
--------------------------------------------------
=
MPP 2.31()2()
0.25
----------------------- 18.5==

41-133S
4
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
For overcurrent unit:
Entering the curve in Figure 24 at multiples of pickup
equal to 4.6, the closing time for instantaneous over-
current is 16 ms. However, the total operating time
for the overcurrent unit is 16 plus 11, which is the
opening time of back contacts of the directional unit,
or 27 ms total operating time for overcurrent unit. The
total time for directional unit is 56 ms, and, since this
is the longest time, 56 ms is the total operating time
of the instantaneous overcurrent circuit.
Entering the curve in Figure 21(page 36) at 4.6, the
1/2 time dial setting gives 140 ms. The total time for
the time-overcurrent circuit is 56 ms directional unit
time plus 16 ms time Aux plus 140 ms = 212 ms.
Example 2:
Let: Ipol = 20 amps
Iop = 23.1 amps
T(tap) = 1 amp
φ -40°= 0°
Entering Figure 23, (page 38) the directional unit
closing time is 12 ms, and the opening time of its
back contacts is 1 ms. The total operating time for
the directional unit is 12 ms.
For overcurrent unit:
Referring to Figure 24, (page 38) the overcurrent unit
contact closing time is about 14 ms. Therefore, the
total operating time for this unit is 14 plus 1 = 15 ms.
In this case the total operating time of relay is 15 ms.
Figure 21 (page 36) gives an operating time of about
50 ms. The time-overcurrent circuit is 12 plus16 plus
50 ms = 78 ms.
4.1 TRIP CIRCUIT
The relay contacts will safely close 30 amperes at
250 volts dc and the seal-in contacts of the indicating
contactor switches will safely carry this current long
enough to trip a circuit breaker.
The indicating contactor switch has two taps that pro-
vide a pickup setting of 0.2 or 2 amperes. To change
taps requires connecting the lead located in front of
the tap block to the desired setting by means of a
screw connection.
4.2 CONTACTS
The moving contact assembly has been factory
adjusted for low contact bounce performance and
should not be changed.
The set screw in each stationary contact has been
factory adjusted for optimum follow and this adjust-
ment should not be disturbed.
4.3 TRIP CIRCUIT CONSTANTS
Indicating Contactor Switch
0.2 ampere tap - 6.5 ohms dc resistance
2.0 ampere tap - 0.15 ohms dc resistance
4.4 AUXILIARY SWITCH (CS-1 OR TR-1)
The CS-1 switch has a dc resistance of 1165 ohms.
The TR-1 telephone relay has a dc resistance of
1500 ohms.
4.5 TYPE IRP RELAY
The IRP relay is designed for potential polarization
and has its maximum torque when the current lags
the voltage by approximately 60 degrees. The shift-
ing of the maximum torque angle is accomplished by
the use of an internally mounted phase shifter as
shown in the internal schematic.
The directional unit minimum pick-up is approxi-
mately 1 volt and 2 amperes at its maximum torque
angle for the directional units used with the 0.5 to 2.5
and 2 to 6 ampere range time overcurrent units. For
the directional units used with the 4-12 ampere range
time overcurrent units the minimum pick-up is 1 volt
and 4 amperes.
4.6 TYPE IRC RELAY
The IRC relay is designed for current polarization
and has its maximum torque when the operating cur-
rent leads the polarizing current by approximately
40°.
The directional unit minimum pick-up is 0.5 ampere
Multiples of pickup lop
T
-------- 2.31
0.5
---------- 4.6== =
MPP lop lpol φ40°–()cos
0.25
-----------------------------------------------------
=
MPP 20()23.1()
0.25
-------------------------- 1850==
Multiples of pickup lop
T
-------- 23.1
1
---------- 23.1== =

41-133S
5
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
in each winding at the maximum torque angle for the
directional units used with the 0.5 to 2.5 and 2 to 6
ampere range time overcurrent units. For the direc-
tional units used with the 4-12 ampere range time
overcurrent units the minimum pickup is 1 ampere.
4.7 TYPE IRD RELAY
The IRD relay utilizes a directional unit similar to the
IRC relay and a directional unit and phase-shifting
circuit similar to those in the IRP relay.
The current-polarized directional unit of the IRD relay
operates on residual currents while the poten-
tial-polarized directional unit of the IRD relay oper-
ates on residual voltage and residual current.
For the directional units used with the 0.5 to 2 and 2
to 6 ampere time overcurrent units, the minimum
pick-up of the current polarized unit is 0.5 ampere in
each winding at the maximum torque angle. The min-
imum pick-up for the voltage polarized unit is 1 volt
and 2 amperes with the current lagging voltage by
60°.
For the directional units used with the 4 to 12 ampere
range time overcurrent units, the minimum pick-up is
1 ampere for the current-polarized directional unit
and 1 volt and 4 amperes for the voltage-polarized
directional unit.
5.0 SETTINGS
5.1 TIME OVERCURRENT UNIT (CO)
The time overcurrent unit settings can be defined
either by tap setting and dial position or by tap setting
and a specific time of operation at some current mul-
tiple of the tap setting (e.g. 4 tap setting, 2 time dial
position or 4 tap setting, 0.6 seconds at 6 times tap
value current).
To provide selective circuit breaker operation, a mini-
mum coordinating time of 0.3 seconds plus circuit
breaker time is recommended between the relay
being set and the relays with which coordination is to
be effected.
The connector screws on the tap plate above the
time dial makes connections to various turns on the
operating coil. By placing this screw in the various
tap plate holes, the relay will just close its contacts at
the corresponding current 4-5-6-7-8-10-12 amperes,
or as marked on the tap plate.
Since the tap block connector screw carries
operating current, be sure that the screw is
turned tight.
5.2 INSTANTANEOUS RECLOSING
The factory adjustment of the CO unit contacts
provides a contact follow. Where circuit breaker
reclosing will be initiated immediately after a trip by
the CO contact, the time of the opening of the con-
tacts should be a minimum. This condition is
obtained by loosening the stationary contact mount-
ing screw, removing the contact plate and then
replacing the plate with the bent end resting against
the contact spring. With this change and the contact
mounting screw tightened, the stationary contact will
rest solidly against its backstop.
5.3 INSTANTANEOUS OVERCURRENT UNIT (I)
The only setting required is the pickup current setting
which is made by means of the connector screw
located on the tap plate. By placing the connector
screw in the desired tap, the relay will just close its
contacts at the tap value current.
Since the tap block connector screw carries
operating currents, be sure that the screw is
turned tight.
5.4 DIRECTIONAL UNITS (D)
No setting is required.
5.5 INDICATING CONTACTOR SWITCH
(ICS/I AND ICS/T)
The setting required on the ICS units is the selection
of the 0.2 or 2.0 ampere tap setting. This selection is
made by connecting the lead located in front of the
tap block to the desired setting by means of the con-
necting screw.
5.6 AUXILIARY SWITCH (CS-1 OR TR-1)
No setting required on the auxiliary switch except for
the selection of the required 24, 48, 125 or 250 volt-
age on the tapped resistor. This connection can be
made by referring to Figure 26 (page 40).
!CAUTION
!CAUTION

41-133S
6
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
6.0 INSTALLATION
The relays should be mounted on switchboard pan-
els or their equivalent in a location free from dirt,
moisture, excessive vibration and heat. Mount the
relay vertically by means of the rear mounting stud or
studs for the type FT projection case or by means of
the four mounting holes on the flange for the
semi-flush type FT case. Either the stud or the
mounting screws may be utilized for grounding the
relay. External toothed washers are provided for use
in the locations shown on the outline and drilling plan
to facilitate making a good electrical connection
between the relay case, its mounting screws or
studs, and the relay panel. Ground Wires should be
affixed to the mounting screws or studs as required
for poorly grounded or insulating panels. Other elec-
trical connections may be made directly to the termi-
nals by means of screws for steel panel mounting or
to the terminal stud furnished with the relay for thick
panel mounting. The terminal stud may be easily
removed or inserted by locking two nuts on the stud
and then turning the proper nut with a wrench.
For detail information on the FT case refer to I.L.
41-076.
The external ac connections of the directional over-
current relays are shown in Figures 13, 14, and 15
(on page 28, page 29, and page 30). If no voltage
polarizing source is to be connected to the IRD relay,
short-circuit the voltage polarizing circuit at the termi-
nals of the relay.
6.1 REVERSED CONTACTS
In installations where the relay could be exposed to
unusual shock or jarring, the possibility of inadvertent
contact closure can be reduced by reversing the ori-
entation of the directional unit contacts. Contact
arrangement and wiring would be reversed on the
directional unit. Its contact would then mechanically
close in a direction opposite to that of the instanta-
neous unit contact. Electrical characteristics and
external connections to the relay would not be
affected. Field modifications can be made per the
following procedures.
1. Reverse the leads on the stationary contacts
of the directional unit. For the IRD, reverse
the leads on both directional units.
2. Reverse the leads to switch jaw terminals 6
and 7. For the IRD, also reverse leads to
switch jaw terminals 4 and 5.
3. Move the spring adjuster on each directional
unit such that the left hand contacts are
normally closed.
4. Remove, then reverse the right hand and left
hand stationary contacts on each directional
unit. Adjust the left hand contact until it just
makes with the moving contact, then
advance it an additional 1/2 turn in. Now
adjust the right hand stationary contact until
it just makes with the moving contact, then
screw it out 3/4 turn for a contact gap of
.020”to .024”.
5. Calibrate each directional unit per proce-
dures beginning at section 7.4.1.c.
For relays whose contacts have been
reversed, it is recommended that a sub letter
“R”be added to the nameplate at the end of
the style number to designate that the relay
has reversed contacts. The new schematics
for modified relays are 9654A56, 9654A57,
9654A58.
7.0 ADJUSTMENTS AND
MAINTENANCE
The proper adjustments to insure correct operation of
this relay have been made at the factory. Upon
receipt of the relay, no customer adjustments, other
than those covered under “SETTINGS”(page 5),
should be required.
7.1 ACCEPTANCE CHECK
The following check is recommended to insure that
the relay is in proper working order.
7.1.1 Instantaneous Overcurrent Unit (I)
a. Contact Gap: The gap between the stationary
and moving contacts with the relay in the
de-energized position should be approximately
.020”.
b. Minimum Trip Current: The normally-closed con-
tact of the directional unit should be blocked
open when checking the pick-up of the overcur-
rent unit.
The pick-up of the overcurrent unit can be

41-133S
7
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
checked by inserting the tap screw in the desired
tap hole and applying rated tap value current.
The contact should close within 5% of tap value
current.
7.1.2 Directional Unit (D)
a. Contact Gap: The gap between the stationary
contact and moving contact with the relay in the
deenergized position should be approximately
.020”.
b. Sensitivity: The respective directional units
should trip with value of energization and phase
angle relationship as indicated in Table 1 (page
10).
c. Spurious Torque Adjustments: There should be
no spurious closing torques when the operating
circuits are energized per Table 2 (page 11) with
the polarizing circuits short circuited for the volt-
age polarized units and open-circuited for the
current polarized units.
7.1.3 Time Overcurrent Unit (CO)
Contacts
The index mark on the movement frame will coincide
with the “0”mark on the time dial when the stationary
contact has moved through approximately one-half of
its normal deflection. Therefore, with the stationary
contact resting against the backstop, the index mark
is offset to the right of the “0”mark by approximately
.020”. The placement of the various time dial posi-
tions in line with the index mark will give operating
times as shown on the respective time-current
curves.
Minimum Trip Current
Set the time dial to position 6 with the auxiliary switch
contacts blocked closed, alternately apply tap value
current plus 3% and tap value current minus 3%. The
moving contact should leave the backstop at tap
value current plus 3% and should return to the back-
stop at tap value current minus 3%.
Time Curve
Table 3 (page 11) shows the time curve calibration
points for the various types of relays. With the time
dial set to the indicated position, apply the currents
specified by Table 3 (e.g. for the CO-2, 3 and 20
times tap value current) and measure the operating
time of the relay. The operating times should equal
those of Table 3 plus or minus 5 percent.
7.1.4 Indicating Contactor Switches
(ICS/I) and (ICS/T)
a. Close the contacts of the CO and pass sufficient
dc current through the trip circuit to close the
contact of (ICS/T). This value of current should
not be greater than the particular (ICS/T) tap set-
ting being used. The operation indicator target
should drop freely, bring the letter “T”into view.
b. Close the contacts of the instantaneous overcur-
rent unit (I) and the directional unit (D). Pass suf-
ficient dc current through the trip circuit to close
the contacts of (ICS/I). This value of current
should not be greater than the particular (ICS/I)
tap setting being used. The operation indicator
target should drop freely, bringing the letter “I”
into view.
7.2 ROUTINE MAINTENANCE
All relays should be inspected periodically and the
time of operation should be checked at least once
every year or at such other time intervals as may be
dictated by experience to be suitable to the particular
application. The use of phantom loads, in testing
induction-type relays, should be avoided, since the
resulting distorted current waveform will produce
error in timing.
All contacts should be periodically cleaned. A contact
burnisher #182A836H01 is recommended for this
purpose. The use of abrasive material for cleaning
contacts is not recommended, because of the danger
of embedding small particles in the face of the soft
silver and thus impairing the contact.
7.3 CALIBRATION
Use the following procedure for calibrating the relay if
the relay has been taken apart for repairs or the
adjustments have been disturbed. This procedure
should not be used unless it is apparent that the relay
is not in proper working order. (See Acceptance
Check, page 6.)
7.4 INSTANTANEOUS OVERCURRENT UNIT (I)
a. The upper pin bearing should be screwed down
until there is approximately .025 clearance
between it and the top of shaft bearing. The
upper pin bearing should then be securely
locked in position with the lock nut. The lower
bearing position is fixed and cannot be adjusted!

41-133S
8
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
b. The contact gap adjustment for the overcurrent
unit is made with the moving contact in the reset
position i.e., against the right side of the bridge.
Move in the left-hand stationary contact until it
just touches the moving contact then back off the
stationary contact 2/3 of one turn for a gap of
approximately .020”. The clamp holding the sta-
tionary contact housing need not be loosened for
the adjustment since the clamp utilizes a
spring-type action in holding the stationary con-
tact in position.
c. The sensitivity adjustment is made by varying
the tension of the spiral spring attached to the
moving element assembly. The spring is
adjusted by placing a screwdriver or similar tool
into one of the notches located on the periphery
of the of the spring adjuster and rotating it. The
spring adjuster is located on the underside of the
bridge and is held in place by a spring type
clamp that does not have to be loosened prior to
making the necessary adjustments.
Before applying current, block open the nor-
mally-closed contact of the directional unit insert
the tap screw in the minimum value tap setting
and adjust the spring such that the contacts will
close as indicated by a neon lamp in the contact
circuit when energized with the required current.
The pick up of the overcurrent unit with the tap
screw in any other tap should be within 5% of tap
value.
If adjustment of pick-up current in-between tap
settings is desired insert the tap screw in the next
lowest tap setting and adjust the spring as
described. It should be noted that this adjustment
results in a slightly different time characteristic
curve and burden.
7.4.1 Directional Unit (D)
In the type IRP and IRC relays the directional unit is
the lower cylinder unit. In the type IRD the directional
units are the lower and middle cylinder units.
a. The upper bearing screw should be screwed
down until there is approximately .025 clearance
between it and the top of the shaft bearing. The
upper pin bearing should then be securely
locked in position with the lock nut.
b. Contact gap adjustment for the directional unit is
made with the moving contact in the reset posi-
tion, i.e., against the right side of the bridge.
Advance the right hand stationary contact until
the contacts just close. Then advance the sta-
tionary contact an additional one-half turn.
Now move in the left-hand stationary contact
until it just touches the moving contact. Then
back off the stationary contact 3/4 of one turn for
a contact gap of .020”to .024”. The clamp hold-
ing the stationary contact housing need not be
loosened for the adjustment since the clamp uti-
lizes a spring-type action in holding the station-
ary contact in position.
c. Insert tap screw of overcurrent unit in highest
tap. The sensitivity adjustment is made by vary-
ing the tension of the spiral attached to the mov-
ing element assembly. The spring is adjusted by
placing a screwdriver or similar tool into one of
the notches located on the periphery of the
spring adjuster and rotating it. The spring
adjuster is located on the underside of the bridge
and is held in place by a spring type clamp that
does not have to be loosened prior to making the
necessary adjustments. Set red mark on core to
left side of cylinder unit and adjust spring to just
reset.
The spring is to be adjusted such that the con-
tacts will close as indicated by a neon lamp in the
contact circuit when energized with the required
current and voltage as shown in Table 1 (page
10). This table indicates that the spring can be
adjusted when the phase angle relationship
between the operating circuit and the polarizing
circuit is at the maximum torque angle or when
the circuit relationship has the operating and
polarizing circuits in phase.
d. The magnetic plugs are used to reverse any
unwanted spurious torques that may be present
when the relay is energized on current or voltage
alone.
The reversing of the spurious torques is accom-
plished by using the adjusting plugs in the follow-
ing manner:
1. Voltage circuit terminals on the voltage
polarized relays (IRP and IRD voltage polar-
ized unit) are short-circuited.
2. The polarizing circuits of the current polar-
ized relays (IRC and IRD current polarized
unit) are open-circuited.

41-133S
9
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Upon completion of steps 1 or 2 above, apply 5
amps and gradually increase to 80 amps. Note,
high current to be applied only momentarily.
Plug adjustment is then made per Table 2 (page
11) such that the spurious torques are reversed.
The plugs are held in position by upper and lower
plug clips. These clips need not be disturbed in
any manner when making the necessary adjust-
ment.
The magnetic plug adjustment may be utilized to
positively close the contacts on current alone.
This may be desired on some installations in
order to insure that the relay will always trip the
breaker on zero potential.
e. The core adjustment is used to eliminate any
unwanted spurious torques that may be present
when the relay is energized with voltage alone.
Apply 120V AC to terminals 4 (+) and 5 for IRD
and terminals 6 (+) and 7 for IRP and adjust core
so that contacts just open.
7.4.2 Time Overcurrent Unit (CO)
Contacts
The index mark on the movement frame will coincide
with the “0”mark on the time dial when the stationary
contact has moved through approximately one-half of
its normal deflection. Therefore, with the stationary
contact resting against the backstop, the index mark
is offset to the right of the “0”mark by approximately
.020”. The placement of the various time dial posi-
tions in line with the index mark will give operating
times as shown on the respective time-current
curves.
Minimum trip Current
The adjustment of the spring tension in setting the
minimum trip current value of the relay is most con-
veniently made with the damping magnet removed.
With the time dial set on “0”, wind up the spiral spring
by means of the spring adjuster until approximately
6-3/4 convolutions show.
Set the relay on the minimum tap setting, the time
dial to position 6.
With auxiliary switch (Aux) contacts blocked closed,
adjust the control spring tension so that the moving
contact will leave the backstop at tap value current
+1.0% and will return to the backstop at tap value
current -1.0%.
Time Curve Calibration
Install the permanent magnet.
Apply the indicated current per Table 3 (page 11) for
permanent magnet adjustment (e.g. IRP-8, 2 times
tap value) and measure the operating time. Adjust
the permanent magnet keeper until the operating
time corresponds to the value of Table 3.
Apply the indicated current per Table 3 for the elec-
tromagnet plug adjustment (e.g. IRP-8, 20 times tap
value) and measure the operating time. Adjust the
proper plug until the operating time corresponds to
the value in Table 3. (Withdrawing the left hand plug,
front view increases the operating time and with-
drawing the right hand plug, front view, decreases
the time.) In adjusting the plugs, one plug should be
screwed in completely and the other plug run in or
out until the proper operating time has been
obtained.
Recheck the permanent magnet adjustment. If the
operating time for this calibration point has changed,
readjust the permanent magnet and then recheck the
electromagnet plug adjustment.
7.5 INDICATING CONTACTOR SWITCHES (ICS/I)
AND (ICS/T)
For proper contact adjustment, insert a .030”feeler
gauge between the core pin and the armature. Hold
the armature closed against the core pin and gauge
and adjust the stationary contacts such that they just
make with the moving contact. Both stationary con-
tacts should make at approximately the same time.
The contact follow will be approximately 1/64”to
3/64”.
Close the contacts of the CO and pass sufficient dc
current through the trip circuit to close the contacts of
the (ICS/T). This value of current should not be
greater than the particular (ICS/T) tap setting being
used. The operation indicator target should drop
freely bringing the letter “T”into view.
Close contacts of instantaneous overcurrent unit (I)
and directional unit (D). Pass sufficient dc current
through the trip circuit to close contacts of the (ICS/I).
This value of current should not be greater than the
particular (ICS/I) tap setting being used. The opera-

41-133S
10
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
tion indicator target should drop freely bringing the
letter “I”into view.
7.5.1 Auxiliary Switch (CS-1 or TR-1)
Adjust the stationary core of the CS-1 switch for a
clearance between the stationary core and the mov-
ing core when the switch is picked up. This can be
done by turning the relay upside-down. Then screw
up the core screw until the moving core starts rotat-
ing. Now back off the core screw until the moving
core stops rotating. This indicates the points where
the play in the assembly is taken up, and where the
moving core just separates from the stationary core
screw. Back off the core screw approximately one
turn and lock in place. This prevents the moving core
from striking and sticking to the stationary core
because of residual magnetism. Adjust the contact
clearance for 3/64”by means of the two small nuts
on either side of the Micarta disc. The TR-1 switch
does not require adjustment.
Connect lead (A) to proper terminal per Figure 26
(page 40). Block directional unit (D) contacts close
and energize trip circuit with rated voltage. Contacts
of auxiliary switch (CS-1 or TR-1) should make as
indicated by a neon lamp in the contact circuit.
8.0 RENEWAL PARTS
Repair work can be done most satisfactorily at the
factory. However, interchangeable parts can be fur-
nished to the customers who are equipped for doing
repair work. When ordering parts, always give the
complete nameplate data.
RELAY TYPE TIME-OVERCURRENT AMPERE RATING OF
UNIT
VALUES FOR†
MIN. PICKUP PHASE ANGLE RELATIONSHIP
VOLTS AMPERES
IRP (Voltage
IRD Unit)
IRC (Current
IRD Unit
)
∆
.5-2.5
2-6
4-12
.5-2.5
2-6
4-12
1
1
1
1
2.0
4.0
4.0
8.0
0.5
.57
1.0
1.3
l lagging V by 60°††
l in-phase with V
l lagging V by 60°††
l in-phase with V
lo leading lp by 40°††
In-phase
lo leading lp by 40°††
In-phase
†The energization quantities are input quantities at the relay terminals.
†† Maximum torque angle.
∆When normal system conditions limit the current to less twice pickup, performance may be
by selecting a higher current ct tap to energize the polarizing circuit.
TABLE 1
DIRECTIONAL UNIT SENSITIVITY
9.0 LIST OF FIGURES

41-133S
11
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
RELAY
RATING CURRENT AMPERES BOTH PLUGS IN CONDITION ADJUSTMENT
0.5-2.5 Amps
2-6 Amps
0.5-2.5 Amps
2-6 Amps
4-12 Amps
4-12 Amps
5 - 80
5 - 80
5 - 80
5 - 80
Spurious Torque in contact
closing direction (left front view).
Spurious Torque in contact
opening direction (right front
view, contacts remain open).
Right (front-view) plug
screwed out until
Spurious Torque is
Left (front view) plug
screwed out until
Spurious Torque is in
contact closing direction.
Then the plug is screwed
in until Spurious Torque
is reversed.
reversed.
†Short circuit the voltage polarizing at the relay terminals before making the above adjustment.
TABLE 2
DIRECTIONAL UNIT CALIBRATION †
PERMANENT MAGNET ADJUSTMENT ELECTROMAGNET PLUGS
TIME
OVERCURRENT
UNIT TYPE
TIME
DIAL
POSITION
CURRENT
(MULTIPLES OF
TAP VALUE)
OPERATING
TIME
SECONDS
CURRENT
(MULTIPLES OF
TAP VALUE)
OPERATING
TIME
SECONDS
2
5
6
7
8
9
11
6
6
6
6
6
6
6
3
2
2
2
2
2
2
0.57
37.80
2.46
4.27
13.35
8.87
11.27
20
10
20
20
20
20
20
0.22
14.30
1.19
1.11
1.11
0.65
0.24
TABLE 3
TIME CURVE CALIBRATION DATA –60 HERTZ

41-133S
12
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
INSTANTANEOUS OVERCURRENT UNIT OPERATING CIRCUIT- 60 HERTZ
AMPERE RANGE TAP VA AT TAP VALUE P.F. ANGLE VA AT 5 AMPS P.F. ANGLE
φφ
.5−2
1−4
2−8
4−16
10−40
20−80
.5
.75
1.
1.25
1.5
2.
1.
1.5
2.
2.5
3.
4.
2.
3.
4.
5.
6.
8.
4.
6.
8.
9.
12.
16.
10.
15.
20.
24.
30.
40.
20.
30.
40.
48.
60.
80.
.37
.38
.39
.41
.43
.45
.41
.44
.47
.50
.53
.59
1.1
1.2
1.3
1.4
1.5
1.8
1.5
1.7
1.8
1.9
2.2
2.5
1.7
2.4
3.1
3.6
4.2
4.9
6.6
9.3
12.0
13.5
15.9
19.2
39
36
35
34
32
30
36
32
30
28
26
24
49
43
38
35
33
29
51
45
40
38
34
30
28
21
16
15
12
11
31
24
20
18
16
15
24.
13.
8.5
6.0
4.6
2.9
9.0
5.0
3.0
2.1
1.5
0.93
6.5
3.3
2.1
1.4
1.1
0.7
2.4
1.2
0.7
0.6
0.37
0.24
0.43
0.27
0.20
0.15
0.11
0.08
0.40
0.25
0.18
0.14
0.10
0.07
46
37
34
32
31
28
36
32
29
27
26
24
48
42
37
35
33
29
51
45
40
38
34
31
28
21
17
15
13
12
31
24
20
18
16
15
Thermal capacities for short times other than one second may be calculated on the basis of time being
inversely proportional to the square of the current.
Degrees current lags voltages.
†
φ
RANGE CONTINUOUS RATING ONE SECONDRATING
(AMPERES) (AMPERES)
†
.5-2
1-4
2-8
4-16
10-40
20-80
5
8
8
10
10
10
100
140
140
200
200
200
RATINGS OF OVERCURRENT UNIT

41-133S
13
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS –60 HERTZ
DIRECTIONAL UNIT OPERATING CIRCUIT BURDEN
VOLT AMPERES
Relay
Type Range AMPS
Continuous
Rating
(Amperes)
One Second
Rating†
(Amperes)
Power
Factor
Angle φ
At
Minimum
Tap Value
Current
At 3 Times
Minimum
Tap Value
Current
At 10 Times
Minimum
Tap Value
Current
At 20 Times
Minimum
Tap Value
Current
0.5-2.5
2-6
4-12
0.5-2.5
2-6
4-12
0.5-2.5
2-6
4-12
--
--
12
10
10
12
10
10
12
230
230
280
230
230
280
230
230
280
44.0
42.5
31.8
34.5
34.5
25.0
45.0
45.0
32.4
0.033
0.58
0.64
0.03
0.44
0.48
0.07
1.04
1.16
0.30
5.28
6.12
0.23
4.08
4.62
0.59
9.9
10.8
3.3
58.0
70.0
2.8
48.0
53.6
6.6
106.0
121.2
14.2
240.0
272.0
11.5
182.0
216.0
26.0
420.0
472.0
IRC
IRP
IRD
Degrees current lags voltages at tap value current.
Thermal capacities for short times other than one second may be calculated on the basis of time
being inversely proportional to the square of the current.
φ
†
ENERGY REQUIREMENTS –60 HERTZ
DIRECTIONAL UNIT POLARIZING CIRCUIT BURDEN
RELAY TYPE RATING VOLT AMPERES ∆POWER FACTOR ANGLE φ
IRC
IRP
IRD Current Unit
IRD Current Unit
230 Amperes †
208 Volts††
230 Amperes †
208 Volts ††
1.45
11.2
1.45
11.2
8° Lag
28° Lag
8° Lag
28° Lag
Degrees current leads or lags voltage at 120 volts on voltage polarized units and 5 amperes on current polarized units.
Burden of voltage polarized units taken at 120 volts. Burden of current polarized units taken at 5 amperes.
30 second rating. The 10 second rating is 345 volts. The continuous rating is 120 volts.
φ
∆
†† One second rating.†

41-133S
14
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
TIME OVERCURRENT UNITS: TYPE IRD-2, IRC-2, IRP-2,
VOLT AMPERES ‡
Ampere
Range TAP
Continuous
Rating
(Amperes)
One Second
Rating†
(Amperes)
Power
Factor
Angle φ
At
Minimum
Tap Value
Current
At 3 Times
Minimum
Tap Value
Current
At 10 Times
Minimum
Tap Value
Current
At 20 Times
Minimum
Tap Value
Current
0.5
0.6
0.8
1.0
1.5
2.0
2.5
2.0
2.5
3.0
3.5
4.0
5.0
6.0
4.0
5.0
6.0
7.0
8.0
10.0
12.0
.91
0.96
1.18
1.37
1.95
2.24
2.50
3.01
4.0
4.4
4.8
5.2
5.6
6.0
7.3
8.0
8.8
9.6
10.4
11.2
12.0
28
28
28
28
28
28
28
110
110
110
110
110
110
110
230
230
230
230
230
230
230
58
57
53
50
40
36
29
59
55
51
47
45
41
37
65
50
47
46
43
37
34
4.8
4.9
5.0
5.3
6.2
7.2
7.9
5.04
5.13
5.37
5.53
5.72
5.90
6.54
4.92
5.20
5.34
5.53
5.86
6.6
7.00
39.6
39.8
42.7
45.4
54.4
65.4
73.6
38.7
39.8
42.2
44.0
46.0
50.3
54.9
39.1
42.0
44.1
45.8
49.9
55.5
62.3
256
270
308
348
435
580
700
262
280
312
329
360
420
474
268
305
330
364
400
470
528
790
815
1024
1220
1740
2280
2850
800
920
1008
1120
1216
1500
1800
848
1020
1128
1260
1408
1720
2064
0.5/2.5
2/6
4/12
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely proportional
Degrees current lags voltage at tap value current.
†
φto the square of the current.
Voltages taken with high impedance type voltmeter
‡

41-133S
15
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
TIME OVERCURRENT UNITS: IRD-5, IRC-5, IRP-5
IRD-6, IRC-6, IRP-6
VOLT AMPERES ‡
Ampere
Tap Value TAP
Continuous
Rating
(Amperes)
One Second
Rating †
(Amperes)
Power
Angle φ
At
Current
At
Tap Value
Current
At
Tap Value
Current
At
Tap Value
Current
0.5
0.6
0.8
1.0
1.5
2.0
2.5
2
2.5
3
3.5
4
5
6
4
5
6
7
8
10
12
2.7
3.1
3.7
4.1
5.7
6.8
7.7
8
8.8
9.7
10.4
11.2
12.5
13.7
16
18.8
19.3
20.8
22.5
25
28
88
88
88
88
88
88
88
230
230
230
230
230
230
230
460
460
460
460
460
460
460
69
68
67
66
62
60
58
67
66
64
63
62
59
57
65
63
61
59
56
53
47
3.92
3.96
3.96
4.07
4.19
4.30
4.37
3.88
3.90
3.93
4.09
4.12
4.20
4.38
4.00
4.15
4.32
4.35
4.40
4.60
4.92
20.6
20.7
21.0
21.4
23.2
24.9
26.2
21.0
21.6
22.1
23.1
23.5
24.8
26.5
22.4
23.7
25.3
26.4
27.8
30.1
35.6
103
106
114
122
147
168
180
110
118
126
136
144
162
183
126
143
162
183
204
247
288
270
288
325
360
462
548
630
308
342
381
417
448
540
624
376
450
531
611
699
880
1056
0.5/2.5
2/6
4/12
Range Tap Value
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely
proportional to the square of the current.
Degrees current lags voltage at tap value current.
†
φ
Factor 3 Times 10 Times 20 Times
Voltages taken with high impedance type voltmeter
‡

41-133S
16
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
TIME OVERCURRENT UNITS: IRD-7, IRC-7, IRP-7
VOLT AMPERES ‡
Ampere
Tap Value TAP
Continuous
Rating
(Amperes)
One Second
Rating †
(Amperes)
Power
Angle φ
At
Current
At
Tap Value
Current
At
Tap Value
Current
At
Tap Value
Current
0.5
0.6
0.8
1.0
1.5
2.0
2.5
2
2.5
3
3.5
4
5
6
4
5
6
7
8
10
12
2.7
3.1
3.7
4.1
5.7
6.8
7.7
8
8.8
9.7
10.4
11.2
12.5
13.7
16
18.8
19.3
20.8
22.5
25
28
88
88
88
88
88
88
88
230
230
230
230
230
230
230
460
460
460
460
460
460
460
68
67
66
64
61
58
56
66
63
63
62
61
59
58
64
61
60
58
55
51
46
3.88
3.93
3.93
4.00
4.08
4.24
4.38
4.06
4.07
4.14
4.34
4.34
4.40
4.62
4.24
4.30
4.62
4.69
4.80
5.20
5.40
20.7
20.9
21.1
21.6
22.9
24.8
25.9
21.3
21.8
22.5
23.4
23.8
23.2
27.0
22.8
24.2
25.9
27.3
29.8
33.0
37.5
103
107
114
122
148
174
185
111
120
129
141
149
163
183
129
149
168
187
211
260
308
278
288
320
356
459
552
640
306
342
366
413
448
530
624
392
460
540
626
688
860
1032
0.5/2.5
2/6
4/12
Range Tap Value
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely
proportional to the square of the current.
Degrees current lags voltage at tap value current.
†
φ
Factor 3 Times 10 Times 20 Times
Voltages taken with high impedance type voltmeter
‡

41-133S
17
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
IRD-8, IRC-8, IRP-8
TIME OVERCURRENT UNITS: IRD-9, IRC-9, IRP-9
VOLT AMPERES ‡
Ampere
Tap Value TAP
Continuous
Rating
(Amperes)
One Second
Rating †
(Amperes)
Power
Angle φ
At
Current
At
Tap Value
Current
At
Tap Value
Current
At
Tap Value
Current
0.5
0.6
0.8
1.0
1.5
2.0
2.5
2
2.5
3
3.5
4
5
6
4
5
6
7
8
10
12
2.7
3.1
3.7
4.1
5.7
6.8
7.7
8
8.8
9.7
10.4
11.2
12.5
13.7
16
18.8
19.3
20.8
22.5
25
28
88
88
88
88
88
88
88
230
230
230
230
230
230
230
460
460
460
460
460
460
460
72
71
69
67
62
57
53
70
66
64
62
60
58
56
68
63
60
57
54
48
45
2.38
2.38
2.40
2.42
2.51
2.65
2.74
2.38
2.40
2.42
2.48
2.53
2.64
2.75
2.38
2.46
2.54
2.62
2.73
3.00
3.46
21.0
21.0
21.1
21.2
22.0
23.5
24.8
21.0
21.1
21.5
22.0
22.7
24.0
25.2
21.3
21.8
22.6
23.6
24.8
27.8
31.4
132
134
142
150
170
200
228
136
142
149
157
164
180
198
146
158
172
190
207
248
292
350
365
400
440
530
675
800
360
395
430
470
500
580
660
420
480
550
620
700
850
1020
0.5/2.5
2/6
4/12
Range Factor Tap Value 3 Times 10 Times 20 Times
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely
proportional to the square of the current.
Degrees current lags voltage at tap value current.
†
φ
Voltages taken with high impedance type voltmeter
‡

41-133S
18
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
ENERGY REQUIREMENTS
TIME OVERCURRENT UNITS: IRD-11, IRC-11, IRP-11
VOLT AMPERES ‡
Ampere
Tap Value TAP
Continuous
Rating
(Amperes)
One Second
Rating †
(Amperes)
Power
Angle φ
At
Current
At
Tap Value
Current
At
Tap Value
Current
At
Tap Value
Current
0.5
0.6
0.8
1.0
1.5
2.0
2.5
2
2.5
3
3.5
4
5
6
4
5
6
7
8
10
12
1.7
1.9
2.2
2.5
3.0
3.5
3.8
7.0
7.8
8.3
9.0
10.0
11.0
12.0
14
16
17
18
20
22
26
56
56
56
56
56
56
56
230
230
230
230
230
230
230
460
460
460
460
460
460
460
36
34
30
27
22
17
16
32
30
27
24
23
20
20
29
25
22
20
18
17
16
0.72
0.75
0.81
1.89
1.13
1.30
1.48
0.73
0.78
0.83
0.88
0.96
1.07
1.23
0.79
0.89
1.02
1.10
1.23
1.32
1.8
6.54
6.80
7.46
8.30
10.04
11.95
13.95
6.30
7.00
7.74
8.20
9.12
9.80
11.34
7.08
8.00
9.18
10.00
11.1
14.9
16.3
71.8
75.0
84.0
93.1
115.5
136.3
160.0
74.0
78.5
84.0
89.0
102.0
109.0
129.0
78.4
90.0
101.4
110.0
124.8
131.6
180.0
250
267
298
30
411
502
610
264
285
309
340
372
430
504
296
340
378
454
480
600
720
0.5/2.5
2/6
4/12
Range Factor Tap Value 3 Times 10 Times 20 Times
IRD TIME OVERCURRENT UNIT BURDEN DATA AT HIGH CURRENTS
AMPERE RANGE
TAP VALUE CURRENT
MULTIPLES OF TAP VALUE CURRENT
VA ††
P.F. ANGLE φ
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely
proportional to the square of the current.
Degrees current lags voltage at tap value current.
†
φ
.5 - 2.5
.5 1.0 2.5
40
790
46.7°
80
2600
42°
20
380
37°
40 8 16
1280 60 280
26.5°4.8°4.3°
Voltages taken with high impedance type voltmeter
‡

41-133S
19
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Figure 1: Type IRD Relay Without Case (Front View)
1) Instantaneous Overcurrent Unit and Saturating
Transformer
2) Current Polarized Directional Unit
3) Voltage Polarized Directional Unit.
4) Time Overcurrent Unit
5) Indicating Contactor Switches
6) Auxiliary Switch
Figure 2: Type IRD Relay without Case (Rear View)
1) Varistor
2) Saturating Transformer
3) “E” type Electromagnet
Sub 1
9664A15
Photo
Sub 1
9664A16
Photo
6
1
2
3
4
5
1
2
3

41-133S
20
Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Figure 3: Directional Unit.
Figure 4: Time Overcurrent Unit.
Photo
1) Stationary Contacts
2) Stationary Contact Pressure
Spring
3) Magnetic Adjusting Plugs
4) Upper Bearing Screw
5) Moving Contact
6) Spring Adjuster Clamp
7) Current Bias Vane
Photo
1) Tap Block
2) Time Dial
3) Control Spring Assembly
4) Disc
5) Stationary Contact Assembly
6) Magnetic Plugs
7) Permanent Magnet
#4
#7
#2
#1 #1
#5
#3
#6
#1
#6
#2
#5
#3 #4
#7