Micom P631, Technical Manual

Page: 210 / 638

transient event. On the other hand, instantaneous signals are used to block or
restrain the differential protection functions as fast as possible:
●
As soon as a CTS condition is detected (CTS: Idiff>(CTS)active is
present), the function will raise the differential protection low set threshold
to the DIFF: Idiff>(CTS) PSx setting; see
Fig. 3-120, (p. 3-154) .
The setting for this value determines the CTS operating mode:
■
Signaling only:
DIFF: Idiff>(CTS) PSx = DIFF: Idiff> PSx. Differential protection
remains unrestricted, but there is a risk of unwanted tripping occurring
under load current.
■
Restricted operation:
DIFF: Idiff>(CTS) PSx = maximum load current. This will permit the
safe differential protection behavior, even during CT failure. There will be
no unwanted trip under any load condition, but protection will remain
operational for internal faults with currents exceeding the load current.
■
Blocking:
DIFF: Idiff>(CTS) PSx = DIFF: Idiff>> PSx. In practice differential
protection is blocked for all currents under normal operating conditions.
1 2 3
1
0
I
diff
I
R
Load line
for single side infeed
I
diff
>
I
R,m2
m
1
m
2
I
diff
>(CTS)
64Z6030A_EN
Fig. 3-120: Modification of the differential protection triggering characteristic with CTS active
3.25.6 Reset
Latched CTS signals can be reset using control parameters or through an
appropriately configured binary signal input as well as by a general reset
command.
3.25.7 Multiple Signaling from the CTS Function
The signals issued by the CTS function (and/or measuring circuit monitoring, see
Section 3.26, (p. 3-156) ) are combined into the MAIN: Meas. circ.I faulty
signal. A signal is simultaneously issued by the self-monitoring function.
P631 3 Operation
3-154 P631/EN M/R-11-C // P631-310-650