8
Testing Static Trip III Devices
NOTE
The illumination of the “PICK-UP” light indicates that the
timed delay has started. If the current drops slightly, the light
will go out, the timing circuit may reset instantly and timing will
start over upon the next appearance of triggering.
The static trip device level sensing circuits have a slight
amount of hysteresis. That is the pick-up and drop-out points
of the circuit are very nearly but not exactly the same value.
If the input current is modulated in amplitude the pick-up will
flash ON and OFF, and the timing circuit can never time out.
Short Time Pick-Up Test
1.
Set ammeter to peak responding (All Other Testing),
select desired phase.
2.
Set LONG TIME CURRENT SETTING on .5, INSTANTA-
NEOUS 1 5X, LONG TIME BAND on 30 and SHORT
TIME PICK-UP on 2X.
3.
Press the START button.
4.
Slowly increase the current until the SHORT TIME PICK-
UP light comes ON. This should occur at 0.5 amperes
± 10%. This is the 2X long time current setting.
5.
Repeat for other SHORT TIME PICK-UP settings as
desired. The RANGE switch must be set on HIGH for
currents above 1 ampere. To avoid overheating, do not
maintain the higher currents any longer than necessary.
Ground Pick Up-Test
1.
Select ground with power boost.
2.
Set GROUND PICK-UP on 0.2.
3.
Press the START button and raise the current gradually
until the GROUND PICK-UP light turns ON. This should
occur at .10 15%, repeat for the 0.3 and other
settings. See Table 1 for the settings in amperes.
NOTE
If the output of the trip device is connected to the tripping
actuator of the circuit breaker, the additional current drawn
during tripping may cause confusion. Either disconnect the
actuator or set the ground time delay to its MAXIMUM to allow
time to read the meter before actual tripping occurs.
Instantaneous Pick-Up Test
There is no pick-up LED output for INSTANTANEOUS TRIP,
but tripping of the circuit breaker and/or operation of the test
set relay will indicate instantaneous trip operation.
1.
Select the desired phase with the phase selector switch.
2.
Set LONG TIME CURRENT SETTING on .5, LONG TIME
BAND on 30, SHORT TIME PICK-UP 12X and INSTAN-
TANEOUS PICK-UP ON 2X, ammeter on “All Other
Tests.”
3.
Press the START button.
4.
Raise the current slowly until the relay in the test set
operates. This can be determined audibly and should
occur at 1.0 a 10%. This is 2 times breaker
rating.
5. Repeat for the other settings as desired. Avoid maintain-
ing high currents longer than necessary to obtain the
readings. On some static trips the relay can be heard to
“buzz” when the current is held exactly at the PICK-UP
value. This is due to the output transistor turning ON and
OFF as the current varies. Operation of the relay should
be positive if the current is increased by 2 or 3% above
the pick-up value.
Long Time Delay Test
If the time delay is tested at an input current 6 times the pickup
setting, the nominal time delays will be as marked on the trip
device. Maximum and minimum limits can be determined by
references to the time current characteristic curves Figure 5.
1.
Select the desired phase to be tested.
2.
Set LONG TIME CURRENT SETTING on .5, LONG TIME
BAND on 3.5, SHORT TIME and INSTANTANEOUS
PICKUPS on 12X and SHORT TIME BAND on MAXI-
MUM .40.
3.
Press the START button and adjust the current to 1.5
amperes (6X .5 pick-up).
4.
In turn, press the STOP and the RESET buttons. Allow
time for the ammeter reading to reach zero.
5.
Press the START button. (It is not necessary to hold this
button. Power will be maintained until the Static Trip
times out.)
6.
When the trip device operates, check the reading of the
stop clock against the curves in Figure 5. The reading
should be approximately the same as shown on the
faceplate of the device, but must be within the limits
shown on the curves. If not, recheck all settings and
repeat the test.
7.
Repeat steps 5 and 6 one or more times to verify the test
results .
8.
Repeat for the other phases (by changing the phase
selector switch) time delay bands and other values of
current, as desired. All test points should fall within the
bands of Figure 5.
