Page 143 - SACE Tmax XT - Catalogue

SOLUTIONS 6/9

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Load Shedding

The Tmax XT has many load shedding algorithms to avoid power
unbalance in low voltage plants and to reduce stress for all the components.

Purpose Load Shedding is available on the Tmax XT platform
The Tmax XT embeds patented functions based sharing some information about the loads under
on load shedding which reduce the microgrid control in the plant.
stress in all situations. Typically, it is the main
protection relay of the low voltage microgrid lo- Application examples
cated at the interface point with the medium volt- • Grid-connected plants with running GenSets
age grid, that is able to control the plant in all cir- These contribute to self-consumption together
cumstances. with potential renewable sources and support
the load power supply in emergency conditions.
A microgrid under islanding conditions This is the case for hybrid photovoltaic diesel
After the the Tmax XT circuit-breaker opens, due remote communities connected to weak distri-
to the interface protection system intervention or bution grids where there are a lot of daily faults,
external command, the microgrid should seem- or facilities located in geographical areas where
lessly transition from an on-grid to off-grid state. there are frequent environmental events, for ex-
When it operates in a stand-alone capacity, the ample hurricanes or earthquakes.
power absorption from the main grid ceases, so • Grid-connected plants with back-up GenSets
that the microgrid loads remains supplied by local These are started up after main generator trans-
generation, such as from a diesel GenSet or an fer switching logics and require high reliability.
energy storage system. This microgrid genera- For example, hospitals, banks or data centers. 06
tion can be always active or started up by Auto-
matic Transfer Switching (ATS) logic after the dis- Benefits
connection from the main grid, depending on the Thanks to Tmax XT with the embedded Load
plant configuration. During the islanding transi- Shedding innovations, the following benefits are
tion, it is very important to avoid a frequency guaranteed:
drop, otherwise the generation protections could Service continuity
trip and jeopardize the microgrid stability with a • When a plant remains disconnected from the
consequently long downtime. The Tmax XT em- main grid, even if local generation is present,
ploys current and voltage measurements, and in- there is a significant stress that may mean the
tegrates two different fast load shedding types generators fail with a consequent blackout.
of logic to reduce this blackout risk. This protects Load Shedding logic embedded in the Tmax XT
the microgrid during intentional or unintentional reduces the frequency drop that usually makes
islanding operations: the local generation protection trip, maintaining
• The Basic Load Shedding algorithm is a simple a live plant.
form of logic able to recognize the microgrid
disconnection event and shed a group of not
priority loads thus ensuring a fast time re-
sponse and power balance.
• The Adaptive Load Shedding algorithm is an ad-
vanced algorithm available with the Tmax XT as
an enhancement of the basic version. The intelli-
gent software embedded in the unit sheds the
non-priority loads very quickly according to the
microgrid power consumption and frequency
measurements. Moreover, the software has a
dedicated configuration for backup generation
related to Automatic Transfer Switching (ATS)
and the software itself is even able to estimate
the energy produced by a solar plant based on
the plant geography settings.