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are shown in Figure 2.10-30(b).
Figure 2.10-30 Load encroachment characteristic
The load encroachment element can operate for the command protection functions (ZCS
and ZCG elements) when the user sets Block for the scheme switches [ZCS-LEBlk] and [ZCG-
LEBlk]. We shall see the ZCS and ZCG functions later.
(iii) Fail safe function
Both ZS and ZG provide overcurrent elements, which can be used for fail-safe operation.
For example, an overcurrent element is provided in Z*S, termed Z*S-OCFS-EN. The
option of Z*S-OCFS-EN operation can be included when On is set for the scheme switch [Z*S-
OCFS-EN], the overcurrent element is subject to the setting of [OCF*S] in Z*S. The setting
value is chosen between 0.02–5.00 A (1 A rating) or 0.10–25.00 A (5 A rating).
Similarly, ZG is also provided with overcurrent elements for fail-safe operation. If On is
set for the scheme switch [Z*G-OCFS-EN], the overcurrent element is subject to the setting of
[OCF*G] in Z*G.
(iv) Definite time delay operation
In accordance with the location of the fault, the timing of trip signals can be adjusted with
delayed timers. For instance, a delay timer in Z*S tripping can be set by applying a time delay
setting using [TZ*S] whose value can be chosen between 0.00–100.00s. Similarly, for ZG
delayed timers can be applied using [TZ*G].
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