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GEK- 90636
DISPLAYS
jp The trip indicators are red LED's which are supervised by the passage of trip
current. One is provided for each tripping element.
Table HI
Model
Target
Description
201
Fl
Frequency 1 output contact operated
202
Fl
Frequency I output contact operated
ROC
Rate of change caused Fl contact to operate
F2
Frequency 2 output contact operated
204
Fl
Frequency 1 output contact operated
ROC
Rate of change caused Fl contact to operate
F2
Frequency 2 output contact operated
ROC
Rate of change caused F2 contact to operate
F3
Frequency 3 output contact operated
ROC
Rate of change caused F3 contact to operate
F4
Frequency 4 output contact operated
Test Amber LED's light to indicate when the frequency detection circuit has an
output and if an output relay is energized (TB).
In Service A normally lit green LED indicates the regulated DC and start-up circuity
are operational.
FUNCTIONAL DESCRIPTION
The potential source connected to studs 5 and 6 is stepped down to 6.9 VRMS
filtered and converted to a square wave. It is this square wave that is measured by
the frequency element. The frequency measuring circuit compares the period of the
incoming square wave against a crystal reference. If the source frequency differs
from the setpoint for more than three consecutive periods or cycles the circuit gives
an output. If the under voltage supervision has not operated this output starts a time
delay (which can be set to 0) which in turn drives the output contact. The rate of
change feature if selected will bypass the time delay if the next lower frequency
element has operated.
The rate of change path is F4 to F3, F3 to F2, and F2 to Fl. Therefore when the
frequency settings are made, F4 should be less than F3, etc. This does not preclude
setting one element for restore, another for over, and the remaining two for under in a
four frequency relay. It is only important that the under frequency elements be
adjacent (F1-F2, F2-F3, F3-F4) if rate of change is desired. Block diagrams of each
model can be found in Figures 4, 5 and 6. Internal connection diagrams for each
model can be found in Figures 10, 11 and 12.
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