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86
Time delayed phase and residual
overcurrent protection (TOC1)
The duration of each output signal is at least 15 ms. This enables continuous output sig-
nals for current, which go just a little above the set operating value.
The timer tP is activated if the current in any of the phases exceeds the set operate value
I>. The output signal TOC1-TRIP is activated if the current exceeds the set operate val-
ue for a period longer than the set time-delay tP.
The timer tN is activated if the residual current exceeds the set operate value IN> for
the earth-fault protection function. The output signal TOC1-TRIP is activated if the cur-
rent exceeds the set operate value for a period longer than the set time-delay tN.
The simplified logic diagram of the time delayed phase overcurrent functions is shown
in figure 43.
The function is disabled (blocked) if:
•
The terminal is in TEST mode (TEST-ACTIVE is high) and the function has been
blocked from the HMI (BlockTOC1=Yes).
•
The input signal TOC1-BLOCK is high.
The TOC1-BLOCK blocking signal can be connected to a binary input of the terminal
in order to receive a block command from external devices or can be software connect-
ed to other internal functions of the terminal itself in order to receive a block command
from internal functions. Through an OR gate it can be connected to both binary inputs
and internal function outputs. The TOC1-BLOCK signal blocks also the time delayed
residual overcurrent function (IN>).
With the setting Operation=Independ (independent function) the protection function is
constantly active. With the setting Operation=Backup the binary input signal TOC1-
RELEASE must be activated to receive a logical one to the AND-gate and thereby en-
able the protection function.
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