Page 68 - Sace Emax 2 Catalogue

4/4 SACE EMA X 2 LOW VOLTAGE AIR CIRCUIT-BRE AKERS

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Adaptive Protections

Emax 2 adds dual setting capability to switching device to
ensure continuous coordination

Purpose Application example
User’s plants can work as a LV Microgrid thanks We have a plant connected to the MV Utility by
to the energy produced by renewable and local means of a MV/LV transformer. If the Utility shuts
power sources, in particular as a consequence of down, the plant will become a Microgrid supplied
lacking of the Utility power supply, e.g. due to a by the local generator G, which will feed the prior-
fault on the MV voltage side. In order to still guar- ity loads by using the loads shedding feature of
antee a high level of selectivity and continuity of Emax 2.
service, it is important to take into account the In grid-connected condition, the generator G is
variation of the short circuit power when moving disconnected. With reference to fig.1:
from. Indeed, during grid connected condition • Circuit breaker A is closed
the fault current on a microgrid feeder is supplied • Circuit breaker B is open
by the Utility, so it is higher than the one supplied • Circuit breakers C are closed. The protections of
only by the local generation during islanded con- the one that supplies loads D are upgraded us-
dition. ing "Set A" of Emax 2 unit.
As a result, it is desirable that the several protec- • Circuit breakers D are closed
tion thresholds of the units can be automatically • Circuit breaker E is closed
changed during the transition to the islanding • Circuit breaker QS1 is closed
condition. • All loads supplied.
The circuit breakers C are selectively coordinated
with the upstream main circuit breaker A, sup-
plied by the Utility, and the downstream load cir-
cuit breakers D (fig. 2).
U

G

A B

E C C C

non priority loads
QS1

D D D

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Fig. 1