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41-347.12C
4. Differential Characteristic
a. Close SPDT switch to position 1. Close
SPST switch and set I
30 amps. Then adjust I
Lower I
and the relay should operate
SR
between the following limits:
I
=
20 amperes
ac
I
=
45 to 50 amperes
LR
30% Sensitivity Relay Only
b. Close SPDT switch to position 1 with SPST
switch closed. Set I
to 10 amperes. Increase I
If the lower polar unit does not operate with
I
= 2.8 amperes and I
ac
lower I
current. The lower polar unit
SR
should operate between the following limits:
I
=
2.8 to 2.95 amperes
ac
I
=
11.8 to 12.8 amperes
LR
c. Reverse leads to restraint transformers and
repeat differential test outlined in paragraph
4b. Results should be approximately the
same as obtained under paragraph 4b.
35% Sensitivity Relay Only
d. Close SPDT switch to position 1 with SPST
switch closed. Set I
to 9 amperes. Increase I
the lower polar unit does not operate with I
= 2.8 amperes and I
lower I
current. The lower polar unit
SR
should operate between the following limits:
I
=
2.8 amperes
ac
I
=
10.8 to 11.8 amperes
LR
e. Reverse leads to restraint transformers and
repeat differential test outlined in paragraph
4d. Results should be approximately the
same as obtained under paragraph 4d.
5. Harmonic Restraint Characteristic
Close SPDT switch to position 2 with SPST switch
closed. Short out I
ammeter. Set I
LR
and adjust I
until upper polar unit operates. I
ac
should read between 6.5 and 9 amperes.
16
to zero and I
to
ac
SR
to 20 amperes.
ac
to zero and adjust I
ac
SR
to 2.8 amperes.
ac
= 12.8 amperes,
LR
to zero and adjust I
ac
SR
to 2.8 amperes. If
ac
ac
= 11.8 amperes,
LR
to 4 amperes
dc
ac
As shown in figure 17, these values of alternating
current corresponding to 17 percent and 14 percent
second harmonic.
In-Service Test
Table 2 is to be used as an in-service check of the
HU or HU-1 relay using any tap combination. This
test also checks against reversed tap connections.
The relay should be connected as shown in figure 16
with the SPDT switch in position 1. The ammeter I
measures the smaller restraint current and should be
connected to the terminal associated with the tap
block of the smaller setting. The ammeter I
sures the larger restraint current, and should be con-
nected to the terminal associated with the larger tap
block setting. Terminal 5 supplies the upper tap
block; terminal 7 supplies the second tap block; and
terminal 9 (HU-1 only) supplies the lower tap block
(refer to figures 3 and 4).
Table 2 gives the values of I
the relay when using a value of I
tap value for all taps except the 8.7 tap. A value of
I
equal to 2 times tap value was given for the 8.7
SR
tap setting in order to keep the current at a conve-
nient value of testing. Table 2 refers to a 30% relay.
For a 35% relay, values of I
higher.
Example (HU Relay):
Upper Tap Block Tap 3.5
Lower Tap Block Tap 5.0
Since the upper tap block has the smaller tap setting
I
should be connected to the upper tap block (Ter-
SR
minal 5), and I
should be connected to Terminal 7.
LR
From table 1 under "Restraint Transformer Tap:
Larger" = 5.0 "Smaller" = 3.5, set I
The value of I
to operate the relay should be
ac
between 8.3 and 9.2 amps.
To check the third restraint winding on the HU-1
repeat the above procedure using terminal 9 and
either terminal 5 or 7.
ROUTINE MAINTENANCE
All relays should be checked at least once every year
or at such other time intervals as may be dictated by
experience to be suitable to the particular applica-
tion.
SR
mea-
LR
necessary to operate
ac
equal to 3 times
SR
will be .1 to .2 amperes
ac
= 10.5 amps.
SR
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