Description; Power Management Systems; Load-Shedding; Application - ABB RELION 630 Series Product Manual

Power Management
PML630/Compact Load-Shedding Solution
Product version: 1.2.1

1. Description

PML630 is a power management device that provides
comprehensive load-shedding solution for the power network
in an industrial plant. It protects the plant against blackouts and
power source outages due to system disturbances. PML630 is
a member of ABB's Relion
series characterized by their functional scalability and flexible
configurability.
PML630 complies to IEC 61850 and offers seamless
connectivity with Relion 630, 620 and 615 series protection
relays, RIO600 IO units and COM600 to realize the load-
shedding functionality. The device uses GOOSE and MMS
communication profiles for I/O data exchange with other Relion
product family protection relays and COM600 series products.

2. Power management systems

Power Management Systems (PMS) is essential for a safe,
efficient and reliable operation of a power system within an
industrial complex. The PMS functionality suite includes load-
shedding, generator control, power sharing, network
synchronization and power restoration.
PMS solutions protect and optimize the stability of industrial
systems against disturbances by ensuring power sharing
between generators when the industrial power system is
islanded from the grid. These solutions also ensure that the
generators meet the required power demand when the network
is grid-connected. By ensuring fast acting load-shedding
action, generator tripping can be avoided and thereby
facilitating possible islanding of the network.
PMS solutions are suitable for industrial power networks.
• With captive power generation - islanded or grid-
connected
• With substantial and critical loads
• With unstable grid connectivity
• Without grid connectivity
The PMS functionality suite is applicable in various industrial
segments. Some of the industrial segments are Oil and Gas,
Marine, Pulp and Paper, Metals, Minerals, Building automation,
Infrastructure, Food and Beverage. In power utilities, load-
shedding application is particularly relevant.

3. Load-shedding

Load-shedding is required when the electrical load demand
exceeds the capacity of available power sources subsequent to
the loss of power sources or network disintegration. The load-
shedding system has to ensure the availability of electrical
power to all essential and, most importantly, critical loads in the
plant. This is achieved by switching off the non-essential loads
in case of a lack of power in the electrical network or parts of the
electrical network (subnetwork or island).
[1] A frequency-based load-shedding scheme, at the feeder level, acts based on the frequency drop caused by a power deficit. It triggers the shedding of loads based on the preset rate of
change of the frequency or the discreet frequency value settings in their respective devices. It can sometimes result in excessive load-shedding.
ABB
®
product family and a part of its 630
The load-shedding functionality can also be deployed in
industrial power networks with sole dependency on the utility
networks.
The lack of electrical power can be caused by a loss of
generation capacity or power grid connectivity or the tie line
feeding power to the plant.
Based on the shortfall of available power in the power network,
the load-shedding action initiated by the system ensures that
only identified loads are shed, system is stable after load-
shedding and impact on the associated plant operation is
minimal. The system allows flexibility to select or deselect the
load feeders to be load-shed at any point in time during plant
operation.
Furthermore, the load-shedding function should not operate if
the situation in the power network does not necessitate such an
action. Thus, it has to be accurate and selective.

4. Application

PML630 provides system level protection to small or medium-
sized industrial systems from the system disturbances. The
device supports different modes of load-shedding functions.
• Fast load-shedding
• Slow (overload or maximum demand violation-based)
load-shedding
• Manual load-shedding
• Underfrequency load-shedding as a backup to fast and
slow load-shedding
A network power deficit occurs when a power source such as a
generator or a grid transformer trips. There could also be a
power shortage when a network becomes isolated due to trip of
a bus coupler or a bus tie breaker. The fast load-shedding
function protects the power network during a power deficit.
The fast load-shedding function takes corrective action before
[1]
the system frequency drop and provides faster and accurate
load-shedding action based on the power balance calculations
and defined priorities. Thus, the function also contributes
towards faster improvement of the frequency profile of the
system.
The slow load-shedding function prevents the tripping of a
power source during an overload condition. The slow (overload)
load-shedding function triggers the load-shedding and resets
the overload condition by acting faster than the dedicated
overload protection function for the power sources. The
overload situation can arise due to the overcurrent detection in
a generator or grid transformer, or maximum demand violation
at the power grid incomer for a specified period of time. Based
on the amount of the overload, the slow load-shedding function
determines the required load to be shed and uses the power
1MRS757334 E
Issued: 2019-08-27
Revision: E
3