41-748.31B
5
KLF-1 Loss-of-Field Relay
The taps are marked as follows:
4.2
DIRECTIONAL UNIT
This unit is designed for potential polarization with an
internal phase shifter, so that maximum torque
occurs when the operating current leads the polariz-
ing voltage by 43 degrees. The minimum pickup has
been set by the spring tension to be approximately 1
volt and 5 ampere at maximum torque angle.
4.3
UNDERVOLTAGE UNIT
The undervoltage unit is designed to close its con-
tacts when the voltage is lower than the set value.
The undervoltage unit is energized with V
PH-N
. The
contacts can be adjusted to close over the range of
60 to 100 percent of normal system voltage. The
actual range of adjustment is 40 to 70 V
L-N
for relays
rated 69 Vac and 70-120 V
L-N
for relays rated 120
Vac. 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) Coil
4.6
BURDEN
4.7
THERMAL RATINGS
Potential: 75 volts (L-N) continuous (for relays rated
69 Vac)
132 volts (L-N) continuous (for relays rated
120 Vac)
Current: 8 amperes continuous
200 amperes for 1 second
5.0
SETTING CALCULATIONS
5.1
GENERAL SETTING RECOMMENDATIONS
The KLF-1 relay may be applied as a single-zone
device, or two rela ys may b e use d 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-1 and a Zone-2 KLF-1, approximately
equivalent to two-zone step-distance line protection.
A generalized external schematic, which is applica-
ble to either Zone-1 or Zone-2 relays is shown in Fig-
ure 10 (page 25). The recommended settings and
relative advantages of these various configurations
are summarized in Table 1.
T
A
2.4
3.16
4.35
5.93
8.3
11.5
15.8
T
C
0.0
0.91
1.27
1.82
2.55
3.64
5.1
(S
A
, S
C
)
1
2
3
Ampere Pickup
Ohms dc Resistance
0.2
1.0
2.0
8.5
0.37
0.10
M
A
M
C
,
(
)
values between taps .03, .06, .06
±
---------------------------------------------------------------------------------------------
Current at 5 Amps
T
A
& T
C
Settings
VA
Angle of lag
60 Hz
50 Hz
60 Hz
50 Hz
Max.
12.05
10.6
58°
53°
Min.
4.17
3.94
36°
31°
Potential at 69 Volts
(Phase-to-Ground)
Phase 1
VA
Angle of lag
60 Hz
50 Hz
60 Hz
50 Hz
S = 1
S = 2
S = 3
6.1
1.5
0.7
6.1
1.5
0.7
9°
9°
9°
7.5°
7.5°
7.5°
Phase 2
3.18
2.9
48°
43°
Phase 3
2.76
2.55
43°
38°
DC Circuit
Rating
Watts @ Rated
125
250
3.9
7.8
