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I.L. 41-496.52D
Z 1 0
,
Z 1 0
=
---------------------------------- -
Cos 75° θ
(
)
,
–
Here
Z 1 0
Tap Plate Setting
–
,
Z 1 0
Desired Ohmic Reach
–
,
4.2.3. Phase-to-Phase Desensitizer
When it is necessary to disconnect this circuit unsol-
der or cut terminal 8 to the 2Ø-G board (see Figure
24) for SDG-2T or open 2Ø-G switch for SDGT-1T.
5.
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 by means of the mounting stud 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 made
directly to the terminals 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 outline and drilling panel see Figure
12.
For detailed information on the FT case refer to IL 41-
076.
5.1.
External Connections
Figure 11 shows typical connection for single zone
protection using and SDG relay. SPP capacitors are
not required unless surge voltage may exceed 2500
volts.
5.2.
Acceptance Test
Acceptance tests consist of:
1. A visual inspection
2. "Push-button" check (for SDG-2T only).
3. An electrical test to make certain that the relay
measures the balance point impedance accu-
rately.
Step 1. Visual Inspection
Give a visual check to the relay to make sure that
there are no loose connections, broken resistors or
broken wires.
16
.2-4.25 Ohm Relay
All T = 1.23
All T
= 3.69
0
All S = 1
All M = +.18
Step 2. Push-button Check
For SDG-2T only open relay terminal 10 and 11.
Using the test connections of Figure 9. Connect the
ac voltages as per test No. 1. No current connections
are required. Connect the rated dc voltages as
shown. Open circuit connections to terminal No. 7.
Set V
= V
= 70 volts. Depress the white push-
BN
CN
button. The push-button should light. If the push-but-
ton does not light, observe contact operation. If there
is an operation but the lamp does not light this indi-
cates a fault in the push-button circuit. If there is no
fault indication proceed with the electrical test to iso-
late the fault in the push-button circuit or the relay.
Step 3. Electrical Tests
Distance Unit
Tripping is indicated by contact operation. Refer to
Figure 9 for all test connections.
For .2-4.35 Ohm Relay
A. Use connections for Test No. 5 and set V
age = 20 volts. V
BN
phase shifter for 75˚ current lagging voltage.
The relay current required to make the trip should
be between 8.0 - 8.6 amp.
B. Use connections for Test No. 6 and set V
age = 20 volts. V
AN
phase shifter as above. The relay trip current
should be 8.0-8.6 amps.
C. Use connections for Test No. 7 and set V
volts V
= V
= 70 volts. Set the phase shifter
AN
BN
as above. The SDG relay trip current should be
8.0-8.6 amps.
For 1.0 - 31.0 Ohm Relay
A. Use connections for Test No. 5 and set V
volts and V
= V
BN
CN
sequence. Set the phase shifter for 75˚ current
lagging voltage. The relay trip current should be
3.35 - 3.65 amperes.
1.0-31.0 Ohm Relay
All T = 8.7
T
= 26.1
0
All S = 1
All M = +.18
volt-
AN
= V
= 70 volts. Set the
CN
volt-
BN
= V
= 70 volts. Set the
CN
= 20
CN
= 60
AN
= 70 volts in proper phase
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