ABB RELION 630 Series Product Manual page 14

Power Management
PML630/Compact Load-Shedding Solution
Product version: 1.2.1
can be allocated to realize more underfrequency stages.
While Stage 1's activation can be assigned to activate
fast-load shedding based on power balance calculations,
Stage 2 can be assigned to activate manual load-shedding
based on priority or power definitions. The Stage 1 and
Stage 2 activation outputs will act as the external triggers
to the fast and manual load shedding functions
respectively.
• The df/dt activation output from the REU615 can be
connected as an external input trigger (GOOSE input or
hardwired) to activate the fast load-shedding function. The
load-shedding action will be in accordance to the power
deficit situation.
Since the manual load-shedding is not affected by the blocked
status of fast and slow load-shedding functions, the Stage 2
based activation can be considered as an independent backup
to the fast-load shedding function.
If the critical signal for fast-load shedding is for some reason not
received, Stage 1 detects the consequent frequency fall (due to
inadequate power from generators or grid) and initiates load-
shedding. Therefore, Stage 1 is also a backup for fast-load
shedding.
If the detection of overload condition is not adequate enough
for the power sources' slow load shed mechanism, the
consequent frequency drop will be picked by the MAPGAPC
function instances. In this manner, the underfrequency function
is a backup to slow load-shedding as well.
Load-shedding priority assignment
All the loads or load-shedding groups participating in the load-
shedding functionality are assigned a priority in the range of
1...19. The priority assignment is a part of the parametrization
process.
The loads or load-shedding groups with the same priority
assignment are combined automatically. The priority definition
is common for all the load-shedding modes. The higher the
priority number, the higher is the importance of the load feeder
compared to any other load with a lower priority number. Load
with priority 1 has the lowest assigned priority and the load with
priority 19 has the highest assigned priority. The dedicated
internal load priorities are reserved for the inhibited or non-
sheddable loads due to operator or system conditions and for
managing the measurement inaccuracies.
In case there are more than ten sheddable loads connected to a
busbar, it is possible to combine the loads (maximum of three)
in a load-shedding group and assign a common priority to the
group. This implies that the load-shedding application
considers the load-shedding group a single feeder, and the
shedding commands are also sent to all the constituent feeders
concurrently. The load-shed group handling application logic
can be realized in 630 series relays and PML630, subject to
logic block instances.
14
Load-shedding command handling in load feeder devices
Handling in 630, 620 and 615 series protection relays
The load-shedding command from the PML630 device is
validated for the IEC 61850 data quality, communication status
and test mode activation of PML630. The command is only
passed through to activate the circuit breaker opening
command channel when all the conditions are met.
Handling in RIO600 IO unit
The load-shedding command from the PML630 device is
validated only for the IEC 61850 data quality. The command is
extended to the binary output channel only when the IEC 61850
data quality is good (communication healthy, PML630 is not in
test mode).
Load-shedding blocking
The load-shedding blocking feature can be used to block the
load-shedding functionality. This is to prevent the fast and slow
load-shedding modes from using incorrect system data for the
load-shedding calculations. The load-shedding blocking can be
effected automatically or manually.
Automatic blocking
The fast and slow load-shedding functions are blocked
automatically in a subnetwork during certain system conditions.
• Communication failure between PML630 and the device
associated with a power source circuit breaker
• Bad IEC 61850 data quality from the device associated with a
power source circuit breaker
• Device associated with a power source circuit breaker is in
the test mode
• Power source circuit breaker is in the intermediate position
for longer than 200 ms or in an undefined state
The load-shedding functionality is blocked in all the
subnetworks if any of the conditions is true for a network circuit
breaker and its associated 630, 620 or 615 series protection
relay. There is a provision through parametrization to override
the blocking conditions. This is applied only when the cause of
the blocking is known and ensures the availability of the fast and
slow load-shedding functions.
Manual load-shedding can still be activated in any of the
subnetworks when the fast or slow load-shedding functionality
is blocked.
Manual blocking
The fast and slow load-shedding modes in a subnetwork can be
blocked from the device's local or Web HMI or COM600S or
COM600F.
The fast and slow load-shedding functions in all four
subnetworks can be blocked from the local HMI of PML630. In
such situation, the manual load-shedding action execution is
still possible but only from LHMI or WHMI (and not from
COM600S or COM600F).
1MRS757334 E
ABB