Contingency Based Load-Shedding Function Lscacls - ABB RELION 630 Series Technical Manual

1MRS757256 F
7.3.5
PML630/Compact Load-Shedding Solution
Technical Manual
• NPMMXU controls the modes by which the load-shedding data (that is, spin
reserve or extended load-shedding power) can be shared to two adjacent
PML630s.
• NPMMXU configures the phase overcurrent-based slow load-shedding trigger
from continuous to periodic based on the setting.
• NPMMXU calculates slow load trigger, load-shedding blocking and overload
amount for slow load-shedding and island/parallel status for each busbar.
NPMMXU also calculates the fast load-shedding trigger common for all
subnetworks due to fast load-shedding trigger generation from any power source
or the opening of the circuit breaker of external connections at either end.

Contingency based load-shedding function LSCACLS

• LSCACLS receives the load-shedding data from NPMMXU, NCBDCSWI and
LDMMXU.
• LSCACLS identifies the network configuration of the system through the
compensated circuit breaker status of the network circuit breakers. At any
instance of time, a maximum of four active subnetworks can be formed.
• LSCACLS calculates the available power of generator based on its governor
mode and island/parallel status of the busbar to which it is connected.
• LSCACLS also calculates the total available power, total active power, total
overload amount in each subnetwork based on available powers, active powers of
each source and spin reserve received from adjacent PML630s in corresponding
subnetworks. The total active power represents the total loads connected in the
subnetwork.
• The power shortfall calculation module is common for fast load-shedding trigger,
slow load-shedding trigger and external trigger.
• LSCACLS calculates the load-shedding blocking status, fast load-shedding
trigger and slow load-shedding trigger in each subnetwork.
• LSCACLS calculates the cumulative shedding power corresponding to each
priority (from 1...19), total sheddable power, total shedding power inhibited by
system and the total shedding power inhibited by operator.
• The cumulative shedding power at each priority determines that all the loads
having priority setting less than or equal to the load-shedding priority are
dropped, provided that the load-shedding triggers are active.
• LSCACLS calculates the load-shedding priority based on various conditions, for
example, power shortfall, overloading amount, load-shedding power of adjacent
electrical networks or manual load-shedding action and associated load-shedding
trigger(s). Table 262
with respect to load-shedding initiation.
Power management functions
shows the load-shedding priority (p1, p2...) calculation
Section 7
211