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B. Use connections for Test No. 6 and set V
volts and V
= V
AN
CN
shifter as above. The relay trip current should be
3.35 - 3.65 amperes.
C. Use connections for Test No. 7 and set V
volts and V
= V
AN
BN
shifter as above. The relay trip current should be
3.35 - 3.65 amperes.
If the electrical response is outside the limits a more
complete series of tests outlined in the section titled
"Calibration" may be performed to determine which
component is faulty or out of calibration.
If you desire to check relay response at some other
settings use following equation for the trip value of
current.
3 V LN
I
=
------------------------- - where p
,
(
) Z 1
p
2
+
Z 0
=
Zero sequence reach
Z 1
=
Positive sequence reach (in above cases p = 3)
V LN
=
desired fault voltage
WARNING
If testing requires trip current over 15
amps. over prolonged periods, it is recom-
mended that a heavy short lead be connect-
ed from terminal 19 to the center tap of T
socket. Also connect a jumper lead from
terminal 17 to terminal 1 on the large print-
ed circuit board for SDG-1T relay. (Lower
set of terminals rear view).
5.3. Maximum Torque Angle
Maximum torque angle check is optional. In general,
this check is complicated for SDG-1T and SDG-2T
relays by the presence of transient blocking circuit,
and the two-phase-to-ground fault desensitizer cir-
cuit.
The presence of transient blocking circuit requires
that check for maximum torque angle should be
made going from non-tripping to tripping condition at
each end of the tripping range of the relay under test.
= 60
BN
= 70 volts. Set the phase
= 60
CN
= 70 volts. Set the phase
Z 0
=
------- -
Z 1
Since the lab method of testing as used here pre-
sents artificial voltage conditions, under certain volt-
age and phase angle conditions two-phase-to-
ground desensitizer will distor t phase angle
response; hence, it is required to disable the 2φ-G
circuit for SDG-1T by opening the front switch OR
connect a 10K resistor from the cathode of Z6 on the
2φ to Gnd to module to relay terminal 2 for SDG2-T
relays.
To disable transient blocking circuit short out resistor
R48 on large printed circuit board for SDG-1T and
SDG-2T.
5.3.1. Phase A Check
Use connection No. 5. Relay tap settings should be
the same as before. For all ranges set V
V
-V
= 70 volts.
BN
CN
Set current for 1-30 ohm relay or 1.54 amp, and for
.2-4.35 ohm relay for 11 amp. Set phase-shifter for
75° current lagging V
toward 0°. After relays have dropped out, reverse
phase-shifter rotation and note the angle (φ1) at
which relay is fully tripped. Rotate the phase-shifter
past the 75° until relay resets again. Then rotate
phase-shifter back toward 75° until relay is fully
tripped. Note the angle again (φ2).
Maximum torque angle is equal then to
φ1
φ2
+
± (
------------------- -
=
75° 5°
2
Any other T setting may be used, except use 130%
0
current of the trip current at 75° angle.
5.3.2. Phase B Check
Use connection No. 6 Set V
= 70 volts. Otherwise follow the same procedure as
for Phase A.
5.3.3. Phase C Check
Use connection No. 7. Set V
= 70 volts. Otherwise follow the same procedure as
for Phase A. When completed remove jumper from
R48 resistor.
5.4. Two-phase-to-ground Desensitizer Check
Use connection No. 5 except no current connection is
required for this test.
I.L. 41-496.52D
= 20 volts,
AN
voltage. Turn phase-shifter
AN
)
= 20 volts. V
BN
= 20 volts, V
CN
= V
AN
CN
= V
AN
BN
17
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