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Frequency Verifier Adjustment (For SDG-1T-2T)
Use oscilloscope to observe wave shape at test point
TP11. Use test connection No. 5. Set V
V
= 70 volts. Set current for 2.5 amps current lag-
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ging voltage by 75°. Adjust R76 until less than 1 volt
signal of 5.0 to 5.3 ms duration is followed by a posi-
tive pulse (17-23 volts) of approximately 3 ms dura-
tion. See Test Point Wave Shape, Figure 15a.
Impedance Check
Start with 2.5 volts test. Use voltmeter for monitoring
the relay output. The first short deflection is positive
indication of meeting current limits. Then increase
current slightly to see if full 18 volt dc output is
obtained. There should be no drop in output to zero
volts while current is increased. If the currents are
outside the limits for 2.5 volt-test as outlined, proceed
as follows:
Set V
= V
= V
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other as possible. Use connection No. 5. No current
is applied. Measure dc voltage across R9, R10, R11
resistors. Readjust potentiometers R5, R6, R7 until
the voltages across R9, R10, R11 are as close to
each other as possible. These voltages should be in
20-25 volts range. In most cases only slight adjust-
ment of R5, R6, or R7 will be required. Then recheck
pickup current for 2.5 volt test again. If the pickup
currents are close together but outside the specified
limits readjust R18 or R8 to move all pickup values
up or down. Note that R5, R6, R7 are interacting.
Therefore, recheck all three voltages after each
adjustment. If difficulties in balancing at 2.5 volts per-
sist, use 5 volts and double the limits. If it is desired
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
2
+
p
Z
= Zero sequence reach
0
Z
= Positive sequence reach (in above cases p = 3)
1
V
= Faulted Phase Voltage
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7.1. 1 – 30 Ohm Relay
7.1.1. SDG-1T, SDG-2T, and SDG-4T Relays
Using previous relay tap settings, apply rated dc volt-
age and proceed as follows:
= 0 V
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= 70 volts as close to each
Z 0
------- -
Z 1
Part A: 2.5 VOLT TEST
Phase A
=
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Use test connection No. 5. Set V
V
= 70 volts. Disable overcurrent unit by jumping
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terminals 1 & 17 on magnitude comparator module.
Adjust R18 for proper pickup level. Pickup current I
should be .140 - .155 amps, current lagging voltage
V
by 75˚.
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Phase B
Use test connection No. 6. Set V
V
= 70 volts. Pickup current I
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.155 amps, current lagging voltage V
Phase C
Use test connection No. 7. Set V
V
= 70 volts. Pickup current I
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.155 amps, current lagging voltage V
Remove jumper from overcurrent unit and return all
"S" connections to S=1.
Part B: 70 VOLTS TEST
Phase A
Use connections for Test No. 5 and set V
V
= 70 volts. Set phase-shifter for 75° current lag-
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ging voltage. The relay trip current should be 3.95 -
4.20 amperes, current lagging voltage V
Phase B
Use connections for Test No. 6 and set V
V
= 70 volts, and set the phase-shifter as above.
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The relay trip current should be 3.95 - 4.20 amperes,
lagging 75° V
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Phase C
Use test connections for Test No. 7 and set V
V
= V
= 70 volts. Set the phase-shifter as above.
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The relay trip current should be 3.95 - 4.20 amperes,
current lagging 75° voltage V
Part C: S = 3 TEST
Set S
, S
, S
A
B
C
10 volts. Disable overcurrent unit again as for 2.5 volt
test.
I.L. 41-496.52D
= 2.5 volts. V
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= 2.5 volts. V
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should be .140 -
B
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= 10 volts. V
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should be .140 -
C
voltage.
by 75˚
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= 3. Set V
= V
= 70 volts. V
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=
BN
A
=
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by 75˚.
=
AN
by 75˚.
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= V
=
AN
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by 75˚.
AN
= V
=
AN
BN
=
AN
=
AN
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