to trip "instantaneously" during a fault condition when one or two of the phase currents
will become low due to a three-phase trip at the opposite IED, see figure 244. The current
measurement is performed internally and the internal STILL signal becomes logical one
under the described conditions. The load current in a healthy phase is in this way used to
indicate the tripping at the opposite IED. Note that this function will not operate in case of
three-phase faults, because none of the phase currents will be low when the opposite IED
is tripped.
BLOCK
BC
LLACC
STILL
TRLL
ANSI05000158-1-en.vsd
AND
OR
0
0-tLoadOn
ANSI05000158 V1 EN
Figure 244: Loss-of-load acceleration - simplified logic diagram
Breaker closing signals can if decided be connected to block the function during normal
closing.
12.4.7 Technical data
Table 351: ZCLCPLAL technical data
Function
Range or value Accuracy
Operate load current, LoadCurr (1–100)% of IBase ± 1.0% of I
n
Operate current, MinCurr (1–100)% of IBase ± 1.0% of I
n
Timers (0.000–60.000) s ± 0.5% ± 10 ms
12.5 Scheme communication logic for residual overcurrent
protection ECPSCH (85)
12.5.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Scheme communication logic for
residual overcurrent protection
ECPSCH - 85
Section 12 1MRK 506 335-UUS A
Scheme communication
516
Technical manual
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