Section 7 Power Management Functions; Load-Shedding - ABB RELION 630 Series Technical Manual

1MRS757256 F
Section 7
7.1
PML630/Compact Load-Shedding Solution
Technical Manual
Power management functions

Load-shedding

Load-shedding functionality ensures the power availability to critical process loads in
an industrial network by dropping the less critical loads. Contingency based load-
shedding is used as the primary load-shedding function in industrial systems as it is
fast and selective in operation.
PML630 provides system level disturbance management for small and medium-sized
industrial power systems. The IED supports three types of load-shedding functions.
• Fast load-shedding based on network contingencies.
• Slow load-shedding based on overloading the grid transformer or violating the
maximum demand at the grid connection.
• Manual load-shedding based on operator-initiated actions like priority definition
or load-shedding in terms of power to be shed.
The fast or slow load-shedding functions depend on the type of the load-shedding
trigger generation. While the fast load-shedding mode is triggered based on
contingencies like the opening of power source circuit breaker(s), opening of bus
coupler(s), opening of tie circuit breaker(s) or due to the protection operation of any
of the above equipment, the slow load-shedding mode is activated due to the
overloading of power sources. In both cases, the same power shortfall is used for fast
and slow load-shedding actions. The slow load-shedding action is also possible with
the absolute value of overloading for power source(s). Hence, the slow load-shedding
mode considers the maximum of power shortfall and the absolute value of
overloading amount for power source(s).
Table 256: Power network configuration limits for PML630 in cPMS - LS Configuration A
Network element
Sources
External connections to adjacent electrical network areas (with PML630-based
load-shedding)
Busbars/bus sections
Busbars/bus sections with connected power sources
Busbars/bus sections with sheddable loads connected
Bus couplers/tie circuit breaker
Sheddable loads per bus bar
Shedding priority number assigned to sheddable loads
Power management functions
Section 7
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