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
.
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.
1.0
APPLICATION
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 operation of
the third sets up the trip circuit. The relay can be
applied without modification to all types of synchro-
nous machines, such as turbo-generators, water
wheel generators or synchronous condensers.
The KLF relay is designed for use with 3-phase 3 wire
voltage supply and may use wye or open delta-con-
nected voltage transformers. On circuits with 4 wire
wye-connected voltage transformers, the type KLF-1
relay may be used to increase security during inad-
vertent loss-of-potential (such as due to a blown
potential fuse).
2.0
CONSTRUCTION
The relay consists of two air-gap transformers (com-
pensators), two tapped autotransformers, one reac-
tor, one cylinder-type distance unit, directional unit
with adjustable reactor, an under-voltage unit with
adjustable resistor, telephone relay, and an ICS indi-
cating contactor switch.
2.1 COMPENSATOR
The compensators which are designated T
A
and T
C
are two-winding air-gap transformers (Figure 10,
page 21). The primary or current winding of the lon-
greach compensator T
A
has seven taps which termi-
nate at the tap block. They are taps which terminate
at the tap block. They are marked 2.3, 3.16, 4.35,
5.93, 8.3, 11.5, 15.8. The primary winding of the
short-reach compensator T
C
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. A voltage is
induced in the secondary which is proportional to the
primary tap and current magnitude. This proportional-
ity 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 pre-
cisely set at the factory. The clamps which hold the
laminations should not be disturbed by either tighten-
ing or loosening the clamp screws.
The secondary winding is connected in series with
the relay terminal voltage. Thus a voltage which is
proportional to the line current is added vectorialy to
the relay terminal voltage.
2.2 AUTO TRANSFORMER
The auto transformer has three taps on its main wind-
ing, 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 per-
cent in steps of 3 percent.
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
41-748P
Effective:
November 1999
Supersedes I.L. 41-748N, Dated February 1984
( )
Denotes change from superseded issue
Type KLF
Loss-of-Field Relay
50/60 Hertz
