ABB CWC, Instruction Leaflet

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Type CWC and CWP Directional Ground Relay 41-242.2F
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relay were obtained using time dial setting
With the selection of a satisfactory tap value, the
curves of Fig. 10 will quickly show if the combination
of tap and current values provide relay operating
times as indicated by the curve. The value of Column
10 multiplied by N 4.0 for tap 36 gives the R values of
Column 13. These are within the curve of Figure 10.
The same process is allowed in setting the type CWP
relay at Station B on breaker F. Here tap 300 was
selected with dial to provide relay operating times of
0.13 and 0.53 seconds respectively for close-in and
remote faults. The operating limits using this tap are
fulfilled since neither multiples of tap product value
(Column 12) is greater than the polarizing voltage
(Column 8).
After individual relay settings are made, it is neces-
sary to check to see if the relays select properly with
associated relays. In the example the coordinating
time interval was 0.4 second. Therefore, for fault 2,
the relay at D should not operate before the relay at
F plus the coordinating time interval. In other words,
the operating time of D should not be less than 0.13
second plus 0.4 = 0.53 second.
Similarly, the time of the relay at breaker H should
not be greater than 0.13 second in order to select
with relay F for fault 3. If the time of relay H is
greater, then the time of relay at F must be increased
to provide proper selection. This change may be
accomplished by a change in the time lever setting
only, although often a new tap and lever setting may
provide a more satisfactory setting. Changing the
setting of relays at B probably will require a change in
the setting of the relay at Station A.
After the setting are made for all the relays under
minimum generating conditions, then it is necessary
to check the relay operating time and coordination
under the maximum generating conditions. Often
additional changes in tap and dial settings are
required, particularly if the maximum and minimum
fault values are quite different.
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