41-748P
KLF Loss-of-Field Relay
8
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.
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.
4.5 TRIP CIRCUIT CONSTANT
Indicating Contactor Switch (ICS)
0.2 ampere tap - 6.5 ohm dc resistance
2.0 ampere tap - 0.15 ohm dc resistance
4.6 BURDEN
4.7 DRAINS
DC Rating
Watts @ Rated
125
3.9
250
7.8
4.8 THERMAL RATINGS
Potential:
132 volts (L-L) continuous
Current:
8 amperes continuous
200 amperes for 1 second
5.0
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 Zone-1
KLF and a Zone-2 KLF, approximately equivalent to
two-zone step-distance line protection. A generalized
external schematic, which is applicable to either
Zone-1 or Zone-2 relays is shown in Figure 3, page
6. The recommended settings and relative advan-
tages of these various configurations are summa-
rized in Table 1 (page 9).
The single-zone and two-zone setting recommenda-
tions are modified when two or more machines are
bussed at the machine terminals. The voltage and
time delay considerations are treated in detail in
other sections of this leaflet. The recommended set-
tings are outlined in Table 2 (page 9).
5.2 ZONE-2 SETTING CALCULATIONS
(IMPEDANCE UNIT)
Set the impedance unit to operate before the steady-
state stability limit is exceeded. Also, to allow maxi-
mum output without an alarm, set the distance unit to
allow the machine to operate at maximum hydrogen
pressure and 0.95 per unit voltage (lowest voltage for
which the capability curve machine cannot be real-
ized without exceeding the steady-state stability
limit). Set the distance unit to operate before the
steady-state limit is exceeded. Capability curves sim-
ilar to Figure 8, page 15 are obtained from the gener-
ator manufacturer.
To determine the desired setting convert the capabil-
ity curve of Figure 8 to the impedance curve of Figure
9, page 20 by calculating
, where V
T
is the
per-unit terminal voltage and (kVA)
c
is the per-unit
output. The angle from the horizontal of each point
on the impedance curve is the same angle as the
corresponding point on the capability curve.
Current at 5 Amps
T
A
& T
C
Settings
60 Hz
50 Hz
60 Hz
50 Hz
Max.
Min.
18.6
3.8
15.7
3.4
77
°
51
°
74
°
46
°
Potential at 120 Volts
Phase AB
VA
Angle of Lag
S
A
= S
C
60 Hz
50 Hz
60 Hz
50 Hz
1
2
3
18.0
14.4
13.9
18.0
13.8
13.0
2
°
31
°
39
°
2
°
26
°
34
°
Phase BC
VA
Angle of Lag
S
A
= S
C
60 Hz
50 Hz
60 Hz
50 Hz
1
2
3
2.6
5.9
6.6
2.6
5.5
6.1
12
°
38
°
42
°
10
°
33
°
37
°
V
T
2
kVA
(
)
C
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