ABB KLF Instruction Leaflet

ABB Power T&D Company Inc.

Power Automation and Protection Division
Coral Springs, FL 33065

Type KLF

Instruction Leaflet

41-748.21C

Effective: January 1997
Supersedes I.L. 41-748.21B, Dated December 1993

( | ) Denotes Changed Since Previous Issue

CAUTION

!

Before putting protective relays into ser­vice, 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. APPLICATION

These relays have been specially designed and
tested to establish their suitability for Class 1E
applications in accordance with the ABB Power
T&D Company program for Class 1E Qulification
Testing ad detailed in bulletin STR-1. Materials
have been selected and tested to insure that the
relays will perform their intended functions for their
design life when operated in a normal environment
as defined by ANSI standards when exposed to

radiation levels up to 104 rads, and when subjected
to seismic events producing a Shock Response
Spectrum within the limits of the relay rating.

“Class 1E” is the safety classification of the elec­tronic equipment and systems in nuclear power
generating stations that are essential to emergency
shutdown of the reactor, containment isolation,
cooling the reactor, and heat removal from the con­tainment and reactor, or otherwise are essential in
preventing significant release of radioactive mate­rial to the environment.

The KLF relay is a single-phase relay connected to
the ac side of a synchronous machine and contains
three units connected so that the operation of two
units sounds an alarm warning the operator of a
low excitation condition, and the additional opera-

Loss-of-Field Relay

(For Class 1E Application)

tion of the third unit sets up the trip circuit. The
relay can be applied without modification to all
types of synchronous machines, such as turbo gen­erators, water wheel generators or motors.

The KLF relay is designed for use with 3-phase 3­wire voltage supply and may use wye or delta-con­nected voltage transformers. The type KLF-1 relay
may be used to increase security during inadvert­ent loss-of-potential (such as due to a blown poten­tial fuse).

2. CONSTRUCTION

The relay consists of two (2) air-gap transformers
(compensators), two tapped auto-transformers,
one reactor, one cylinder-type distance IT, direc­tional unit with adjustable reactor, an under-voltage
unit with adjustable resistor, telephone relay with
solid state time delay circuit, and an ICS indicating
contactor switch.

2.1 Compensator

The compensators, which are designated TA and
TC, are two (2) winding air-gap transformers (Fig-

ure 2). The primary or current winding of the

long-reach compensator TA has seven taps which
terminate at the tap block. They are marked 2.4,

3.16, 4.35, 5.93, 8.3, 11.5, 15.8. The primary wind­ing of the short-reach compensator TC also has

seven taps which terminate at this tap block. They
are marked 0.0, 0.91, 1.27, 1.82, 2.55, 3.64, 5.1.
Voltage is induced in the secondary which is pro­portional to the primary tap and current magnitude.
This proportionality is established by the cross sec­tional area of the laminated steel core, the length of
an air gap which is located in the center of the coil,
and the tightness of the laminations. All of these
factors which influence the secondary voltage pro­portionality have been precisely set at the factory.

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.

41-748.21C

Front View Rear View

Figure 1. Type KLF Relay

The clamps which hold the laminations should not
be disturbed by either tightening or loosening the
clamp screws.

The secondary winding is connected in series with
the relay terminal voltage. Thus voltage, which is
proportional to the line current, is added vectorially
to the relay terminal voltage.

2.2Auto-Transformer

The auto-transformer has three taps on its main
winding, S, which are numbered 1, 2, and 3 on the
tap block. A tertiary winding M has four taps which
may be connected additively or subtractively to
inversely modify the setting by any value from -15
to +15 percent in steps of 3 percent.

2

The sign of M is negative when the R lead is above
the L lead. M is positive when L is in a tap location
which is above the tap location of the R lead. The
M setting is determined by the sum of per unit val­ues between the R and L lead. The actual per unit
values which appear on the tap plate between taps
are 0,.03,.06, and.06.

The auto-transformer makes it possible to expand
the basic ranges of the long and the short reach

compensators by a multiplier of . Any relay

S

-------------­1 M±

ohm setting can be made within±1.5 percent from

2.08 ohms to 56 ohms for the long-reach and
from.79 ohms to 18 ohms for the short-reach.

Sub 1
185A181

Figure 2. Compensator Construction

2.3 Impedance Tripping Unit

The distance unit is a four pole induction cylinder
type unit. The operating torque of the unit is pro­portional to the product of the voltage quantities
applied to the unit and the sine of the phase angle
between the applied voltages. The direction of the
torque depends on the impedance phasor seen by
the relay with respect to its characteristic circle.

Mechanically, the cylinder unit is composed of four
basic components: A die-cast aluminum frame,
and electromagnet, a moving element assembly,
and a molded bridge. The frame serves as a
mounting structure for the magnetic core. The
magnetic core which houses the lower pin bearing
is secured by the frame by a locking nut. The bear­ing can be replaced, if necessary, without having
to remove the magnetic core from the frame.

The electromagnet has two sets of two series con­nected coils mounted diametrically opposite one
another to excite each set of poles. Locating pins
on the electromagnet 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 electromagnet is
secured to the frame by four mounting screws.

The moving element assembly consists of a spiral
spring, contact carrying number, and an aluminum
cylinder assembled to a molded hub which holds
the shaft. The hub to which the moving-contact

41-748.21C

arm is clamped has a wedge and cam construc­tion, to provide low-bounce contact action. A
casual inspection of the assembly might lead one
to think that the contact arm bracket does not
clamp on the hub as tightly as it should. However,
this adjustment is accurately made at the factory
and is locked in place with a lock nut and should
not be changed. Optimum contact action is
obtained when a force of 4 to 10 grams pressure
applied to the face of the moving contact will make
the arm slip from the condition of reset to the point
where the clamp projection begins to ride up on
the wedge. The free travel can vary between 15° to

20°.
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 stops are an integral
part of the bridge.

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
mounting the adjustable stationary contact hous­ing. This stationary contact has .002 to .006 inch
follow which is set at the factory by means of the
adjusting screw. After the adjustment is made the
screw is sealed in position with a material which
flows around the threads and then solidifies. 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.

When contacts close, the electrical connection is
made through the stationary contact housing
clamp, to the moving contact, through the spiral
spring and out to the spring adjuster clamp.

2.4 Directional Unit

The directional unit is an induction cylinder unit
operating on the interaction between the polarizing
circuit flux and the operating circuit flux.

Mechanically, the directional unit is composed of
the same basic components as the distance unit: a
die-cast aluminum frame, an electromagnet, a
moving element assembly, and a molded bridge.

The electromagnet has two series-connected
polarizing coils mounted diametrically opposite
one another; two series-connected operating coils

3

41-748.21C

* Sub 4
3531A58

Figure 3. Internal Schematic of Type KLF Relay in FT-41 Case

*Denotes Change

mounted diametrically 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 threaded into the
bridge. The electromagnet 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 mounting 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.

2.5 Undervoltage Unit

The voltage unit is an induction-cylinder
unit.

Mechanically, the voltage unit is com­posed, like the directional unit, of four
components: A die-cast aluminum frame,
and electromagnet, a moving element
assembly, and a molded bridge.

The electromagnet has two pairs of volt­age coils. Each pair of diametrically
opposed coils is connected in series. In
addition one pair is in series with an
adjustable resistor. These sets are in

Sub 4
3533A29

parallel as shown in Figure 3. The
adjustable resistor serves not only to
shift the phase angle of the one flux with

Figure 4. KLF Time Delay Schematic

respect to the other to produce torque,
but it also provides a pickup adjustment.

4

41-748.21C

Sub 3
1487B21

Figure 5. External Schematic of Type KLF Relay

Otherwise the undervoltage unit is similar in its
construction to the directional unit.

2.6 Solid State Time Delay Circuit

The telephone relay (x) is energized through a
solid state time delay circuit (TD) as shown in Fig-

ure 3. The solid state time delay circuit shown in
Figure 4 consists basically of an adjustable inte-

grating RC circuit with quick reset. The RC circuit
is adjusted to provide the voltage level to trigger
the SCR through a multi-layer silicon switch. The
SCR in turn energizes the relay.

2.7 Indicating Contactor Switch Unit (ICS)

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
contacts 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 target is reset from the
outside of the case by a push rod located at the
bottom of the cover. The front spring, in addition to
holding the target, provides restraint for the arma­ture and thus controls the pickup of the switch.

3. OPERATION

The relay is connected and applied to the system
as shown if Figure 5. The directional unit closes its
contacts for lagging VAR flow into the machine. Its
zero torque line has been set at -13° from the

R-axis. Its primary function is to prevent operation
of the relay during external faults. The impedance
unit closes its contacts when, as a result of reduc­tion in excitation, the impedance of the machine as
viewed from its terminals is less than a predeter­mined value. The operation of both impedance and
directional units energize the time delay circuit
which operates the X unit after .4 ±.05 seconds.

The operation of impedance, directional and X unit
sounds an alarm, and the additional operation of
the under voltage unit trips the machine. This time
delay is to insure positive contact coordination
under all possible operating conditions. During a
seismic event which exposes the relay to a ZPA
level of 5.7g, the operate time of the X unit may
vary from .25 second to 1.25 seconds due to
bounce induced in the Z and the D contacts. Dur­ing normal conditions, all contacts are open.

3.1 Principle of Distance Unit Operation

The distance unit is an induction cylinder unit hav­ing directional characteristics. Operation depends
on the phase relationship between magnetic fluxes
in the poles of the electromagnet.

5

41-748.21C

Sub 2
185A331

Figure 7. Effect of Compensator Voltages

(ZC is positive)

One set of opposite poles, designated as the oper­ating poles are energized by voltage V1Tmodified

by a voltage derived from the long reach compen­sator TA. The other set of poles (polarizing) are

energized by the same voltage V1T except modi­fied by a voltage derived from the short reach com-

pensator TC. The flux in the polarizing pole is so
adjusted that the unit closes its contacts whenever

flux in the operating set of poles leads the flux in
the polarizing set.

The voltage V1T is equal to:

V120.5 V

+ 1.5 V

==

1T

23

1N

(1)V

As shown in Figure 5, one-half of V23, voltage is
physically derived in the relay at midtap of a reac-

tor connected across voltage V23.
Reach of the distance unit is determined by com-

pensators TA and TC as modified by auto-trans­former settings. Compensators TA and TC are
designed so the their mutual impedances ZA and
ZC have known and adjustable values as
described below under “CHARACTERISTICS” and

“SETTING CALCULATIONS”. The mutual imped-
ance of a compensator is defined here as the ratio
of secondary induced voltage to primary current
and is equal to T. Each secondary compensator
voltage is in series with the voltage V1T. Compen-

sator voltages are equal to 1.5 I1 ZAfor long reach
compensator and 1.5 I1 ZC for short reach com­pensator, where I, is the relay current.

Figure 6 shows how the compensation voltages

1.5 I1 ZA and 1.5 I1 ZC influence the R-X circle.
Notice that ZA independently determines the “long
reach”, while ZC independently determines the
“short reach”. With the reversing links in the nor-

mal position (+ZC) the circle includes the origin;
with the opposite link position (-ZC) the circle
misses the origin. The following paragraphs

explain this compensator action.
Referring to Figure 5 notice that resistor RB and

capacitor CB cause the polarizing voltage to be
shifted 90° in the leading direction. Thus, when the
current is zero, polarizing voltage V

leads the

POL

operating voltage VOP by 90° and of sufficient
magnitude to operate the relay. This means the

apparent impedance is along the X axis. Notice in
Figure 7(b) that the ZA compensation reverses the

operating voltage phase position. The relay bal­ances when this voltage is zero. Note also this bal­ance is unaffected by the ZC compensation, since

this compensation merely increases the size of
V

.

POL

Sub 2

185A182

Figure 6. R-X Diagram Characteristics with various

ZC - Compensator Settings.

6

For lagging current conditions notice Figure 7(c)
illustrates how V

is reversed by the ZC com-

POL

pensation. In this case the ZA compensation has
no effect of the balance point. This explains why

the reach point is fixed independently by ZC.
Figure 7 assumes that ZC is positive (circle

includes origin). If the current coil link is reversed,

41-748.21C

the compensation becomes +1.5 IZC. In Figure
7(b) this change would result in V

POL

being

reduced rather than increased by the compensa­tion. As the current increases V

will finally be

POL

reversed establishing restraining torque. Thus, the
current need not reverse in order to obtain a “short
reach” balance point. Instead the apparent imped­ance need only move towards the origin in the - X
circle region to find the balance point. Therefore
the circle does not include the origin with a
reversed link position.

4. CHARACTERISTICS

The type KLF relay is available in one range.

4.1 Distance Unit

The distance unit can be set to have characteristic
circles that pass through origin, include it, or
exclude it, as shown in Figure 6.

The ZAand ZC values are determined by compen­sator settings and modified by auto-transformer

settings, S, L, and R. The impedance settings in
ohms reach can be made for any value from 2.08
to 56 ohms for ZA, and from 0.79 ohm to 18 ohms

for ZC in steps of 3 percent.
The taps are marked as follows:

T

-------------------------------------------------------------------------------------

2.4 3.16 4.35 5.93 8.3 11.5 15.8,,,,,,

-------------------------------------------------------------------------------------

0.0 0.91 1.27 1.82 2.55 3.64 5.1,,,,,,
,()

S

ASC

----------------------

123,,

---------------------------------------------------------------------------------

values between taps .03, .06, .06±

A

T

C

MAMC,()

age. This voltage is equal to 1.5 V1N voltage. The
contacts can be adjusted to close over the range of

65 to 85 percent of normal system voltage. The
dropout ratio of the unit is 98 percent or higher.

4.4 Trip Circuit

The main contacts will safely close 30 amperes at
250 volts dc and the seal-in contacts of the indicat­ing contactor switch will safely carry this current
long enough to trip a circuit breaker.

4.5 Trip Circuit Constant

Indicating Contactor Switch (ICS)

0.2 ampere rating

1.0 ampere rating

2.0 ampere rating

8.5 ohm dc resistance
.37 ohms dc resistance
.1 ohm dc resistance

4.6 Burden

Current

5 amps, 60 Hz

T

& T

A

C

Settings VA

MAX.

MIN.

Phase AB

S

= SC VA

A

1
2
3

18.0

14.4

13.9

Rating Watts + Rated

125
250

18.6

3.8

POTENTIAL

120 VOLTS, 60 Hz

Angle

of LAG

°

2

31°
39°

dc Circuit

Angle

of LAG

°

77
51°

Phase BC

Angle VA of LAG

2.6

5.9

6.6

12°
38°
42°

3.9

7.8

4.2 Directional Unit

The KLF relay is designed for potential polarization
with an internal phase shifter, so that maximum
torque occurs when the operating current leads the
polarizing voltage by approximately 13 degrees.
The minimum pickup has been set by the spring
tension to be approximately 1 volt and 5 amperes
at maximum torque angle.

4.3 Undervoltage Unit

The undervoltage unit is designed to close its con­tacts when the voltage is lower than the set value.
The undervoltage unit is energized with V1T-volt-

4.7 Thermal Ratings

Potential: 132 volts (L-L) continuous
Current: 8 amperes continuous

200 amperes for 1 second

5. SETTING CALCULATIONS

5.1 General Setting Recommendations

The KLF relay may be applied as a single-zone
device, or two relays may be used to provide
two-zone protection. The single-zone setting may
be fully offset (Zone 1) or may include the origin
(Zone 2). The two-zone application would require a

7