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(iv) Under-voltage element for phase-to-phase (UVS-DIFL)
For UVS-DIFL relay element the user can set the sensitivity using setting [UVS-DIFL]. The
setting value is selected from 5.0 to 130.0V.
(v) Under-voltage change detection element (UVD-DIFL)
Suppose there is a difference between the voltage vector at present (V
M
) and the pre-voltage
vector measured one sampling cycle ago (V
N
). When the magnitude of the difference between
is larger than setting [DUV-DIFL], the UVD-DIFL element† is operated. The setting value is
chosen among 1 to 20V.
†Note: UVD-DIFL element (shown in Figure 2.2-4) is programmed with setting [DUV-
DIFL] as described above. Similarly, signals for monitoring and PLC output signals
are referred ‘UVD-DIFL-AT’ etc., as shown in Figure 2.2-4 and Figure 2.2-6.
(vi) Check relays activation
The user can set On for respective scheme switches [DIFLFS-OCD-EN], [DIFLFS-OC-EN],
[DIFL-UV-EN], [DIFL-UVS-EN], and [DIFL-DUV-EN] so that the user can select the operation of
the respective check relays.
2.2.3 CT circuit-failure detection (DIFL-CTF)
The CT circuit-failure-detection function (DIFL-CTF) is to detection of the breaking wire in
the CT circuit. Signals of the check relays are injected into the below logic so that a trip signal
is not issued upon occurrence of CT failure.
From CT failure detection
Figure 2.2-6 CT failure detection logic
The user can select the detection type for the CT circuit-failure using setting [DIFL-CTF].
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