ABB RELION 630 Series Product Manual page 13

Power Management
PML630/Compact Load-Shedding Solution
Product version: 1.2.1
line to an acceptable level based on the parameter settings. It is
termed as slow load-shedding because the overload detection
is a slow process compared to a contingency like a power
source protection operation followed by circuit breaker trip.
The overload detection is available for all eight power sources
based on the three phase low stage overcurrent protection
(PHLPTOC) function (identical to the function that is
implemented in 630 series), with flexibility in curve selection and
parameter selection. The 3-phase currents are acquired over
IEC 61850 GOOSE from the respective power source devices.
For the grid 1 and grid 2 feeders (when configured for external
grid connectivity), there is an option to acquire the currents
locally to the slow load-shedding function by extending CT
wiring to PML630.
The 8CT/2VT connections can be used for two power sources.
PML630 requires adequate coordination with the power source
feeder device's PHLPTOC function for early overload detection
and effective activation of the slow load-shedding functionality.
It is also possible to get an external overload signal (for
example, thermal overcurrent start) to trigger the slow load-
shedding function for any power source. The external overload
signal should be configured to be sent from the power source
device to PML630 over IEC 61850 GOOSE.
The overload detection based on a maximum demand
exceeding beyond a certain time limit and is available for all the
power sources even though it is more applicable for two power
sources (grid connectivity feeder).
The method for reduction or elimination of the overload
condition on the power source can be parametrized and should
be decided based on the project requirements.
The actual permitted overload can be defined for each power
source, and load can be shed accordingly. This results in load
reduction on that specific power source based on the set
parameter.
Alternatively, based on the actual permitted overload and the
subsequent power balance calculation activation, the load-
shedding can be initiated in the associated subnetwork.
The overload trigger for a power source is generated
periodically as long as the overload conditions prevail, implying
that loads can be shed in multiple shedding actions.
The slow load-shedding mode is only effective within one power
network area (under a PML630 device) and cannot be extended
across the power network areas (other PML630 devices) like
fast load-shedding in Configuration B.
An overload condition in a subnetwork causes a negative power
balance situation. This event can be used to trigger the fast
load-shedding using its external trigger feature. The result of
the power balance calculation leads to load-shedding in that
subnetwork.
ABB
Manual load-shedding
The function can be used to obtain any preemptive power relief
in any of the active subnetworks in a PML630 device's own
power network area.
The needed power relief can be defined in the form of the load
priority up to which loads have to be shed or alternatively in
terms of the actual power.
The shedding priority or a power and a manual trigger can be
set as parameters or acquired from an external device or
system or from COM600S or COM600F to PML630 over IEC
61850 GOOSE. When entered as a priority, load-shedding
commands are issued to load feeders with a priority lower than
and equal to the priority entered by the operator. When entered
as a power value, an equivalent load-shedding priority is
calculated in such a way that the actual amount of load-
shedding at least equals or is higher than the defined value.
The manual load-shedding feature can also be used in new
ways using the external manual load-shedding trigger feature.
For instance, a time-based load-shedding can be achieved by
connecting an external timer output to PML630 device as a
hardwired input or through RIO600. On activation of the timer,
load-shedding can be activated simultaneously in all the
subnetworks based on the priority or the power definition.
When a load-shedding priority is identified for load-shedding, all
the constituent load feeders associated with that priority will
receive load-shedding commands.
The manual load-shedding mode is only effective within one
power network area (under a PML630 device) and cannot be
extended across the power network areas (other PML630
devices) like fast load-shedding in Configuration B.
An overload condition in a subnetwork causes a negative power
balance situation. This event can be used to trigger the fast
load-shedding using its external trigger feature. The power
balance calculation will result in load-shedding in that
subnetwork.
Frequency-based load-shedding
The system frequency can experience a sharp drop when a
power source trips or a gradual drop when there is a gradual
overload. The frequency-based load-shedding function is
independent of the other load-shedding functions.
PML630 has provisions to support and perform load-shedding
action during such conditions, based on the externally provided
process data.
• The generic analog protection function (MAPGAPC)
instances can be used to detect underfrequency
conditions based on frequency data, subscribed over
GOOSE from a device such as REU615. Since eight
instances of the function are available, two instances can
be assigned to each subnetwork as Stage 1 and Stage 2.
In case of lower number of subnetworks, more instances
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