Page 227 - Decision Making Applications in Modern Power Systems

Role of microphasor measurement unit Chapter | 7 191

Transformer
Main grid
Circuit breaker
Load
distributed
DG
generator
1

4

DG4
DG5 2 3 Islanded microgrid
area 4

DG3
Islanded microgrid
DG2 area 3
Islanded microgrid Islanded microgrid
area 2
area 1
FIGURE 7.7 Island concept.

changes quickly, hydro generators have inertia and therefore react to
changes slowly. Therefore the outputs of different generators need to
be coordinated [20].As µPMU measures frequency quickly and pre-
cisely, control measures such as power injections from generators or
shedding of noncritical loads can be easily and accurately implemen-
ted in the islanded area to maintain power balance [19].
c. Resynchronization: For resynchronizing the islanded grid with the
main grid at the point of common coupling, frequency and phase
angle need to be matched. The frequency and phase angle information
of the µPMU eliminate the need of resynchronizing devices colocated
with the breakers [21].
d. Safety: In islanded condition the utility maintenance workers are
unaware of the fact that the downed lines are still energized in the
islanded area. This can prove detrimental to the utility workers. The
decision of the µPMU whether island has occurred or not and its sub-
sequent decision result to the utility can prevent such casualty
[19,22].