Power Data Holding And Delay - ABB RELION 630 Series Technical Manual

1MRS757256 F
7.2.5
PML630/Compact Load-Shedding Solution
Technical Manual
circuit breaker, the load-shedding is blocked in both associated
subnetworks.
Load-shedding can also be blocked in all the subnetworks by an external input if
configured in LSCACLS.
The manual load-shedding action can be performed even though load-shedding is
blocked in subnetworks.
Load-shedding blocking calculated due to various conditions for power source or
network circuit breaker can be overridden with the Block override setting in PSCSWI
and NCBDCSWI respectively.
See PSCSWI, NCBDCSWI and LSCACLS for details regarding load-
shedding blocking calculation.

Power data holding and delay

PML630 holds the power data at every measurement cycle. This data is used in load-
shedding calculation after the delay of one to two measurement cycles. Here, for
example, T, 2T and 3T represent the measurement cycle. This deliberate delay is to
ensure that the load-shedding core function LSCACLS always works on the power
system data that is not influenced by a transient or a disturbance situation.
GUID-54C025E0-3CE7-4074-9B14-8929BCD54F25 V1 EN
Figure 129: Hold and delay of power data
Power management functions
Section 7
209