4.4.2.2 Function block
Figure 467: Function block
4.4.2.3 Functionality
The directional negative-sequence overcurrent protection function DNSPDOC is
used as directional overcurrent and short-circuit protection.
DNSPDOC starts up when the fundamental value of the operating quantity
(negative-sequence or residual current) exceeds the set limit and the directional
criterion is fulfilled. The operate time characteristic is according to definite time
(DT).
The function contains a blocking functionality. It is possible to block function
outputs, timers or the function itself.
4.4.2.4 Analog channel configuration
DNSPDOC has three analog group inputs which must be properly configured.
Table 743: Analog inputs
Input Description
I3P Three-phase currents
IRES
3
Residual current (measured or calculated)
Necessary when
Operating quantity
is "Re-
sidual" or "Residual (calc)"
U3P Three-phase voltages
See the preprocessing function blocks in this document for the possible
signal sources. The GRPOFF signal is available in the function block called
Protection.
There are a few special conditions which must be noted with the configuration.
Table 744: Special conditions
Condition Description
U3P connected real measurements The function requires that at least two volt-
age channels are connected.
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
3
Can be connected to GRPOFF if
Operating quantity
is set to "Negative seq"
Protection functions 1MRS759142 F
826 REX640
Technical Manual
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