IEEE Power & Energy Magazine - January/February 2014 - 61

with iteration input from the user); and advisory mode,
in which, as in iterative mode, the restoration sequence is
calculated step by step. the enhancement offered by this
last mode is that srn will provide an optional set of nbs
units and critical loads. the components in this set can
be restored successfully in the next step. this helps the
user filter out infeasible restoration actions in the coming
step. For all these modes, srn checks the steady-state
constraints and the electromechanical transient stability
constraints for each step.

Updating Decision Support Tool
for System Operators
once restoration tools are available for planning, the next
stage is to bring the decision support system for the planner
closer to real-time online application. with a sufficiently
detailed physical power grid model including breakers,
switches, busbars, and so on, the established restoration
strategies can be used by system operators after an outage.
in this stage, more realistic system models and more constraints are to be taken into account in the dispatchers' point
of view.
epri has a two-phase effort to integrate the srn algorithms
with an operator training simulator (ots). in the first phase,
the minimum path search algorithm has been implemented to
find feasible and direct paths between black-start units and
secondary units and to find the nearest load to bring generating units up to their minimum operating limits. the srn
algorithm can be used with the ots in an operator advisory
mode for training purposes. it can also be used with the ots
in automatic restoration mode-for example, to develop and
verify restoration plans and build partially energized islands
for training scenarios. in the automatic restoration mode, srn
can reduce the labor needed to verify restoration plans and create training scenarios by a factor of ten. in the second phase,
the srn optimal power flow algorithm will be used to mitigate
overloads and voltage stability issues that may tend to occur in
the later phases of a system restoration plan, where the loads
are higher but all the transmission is not yet in service. the
effort is shown in Figure 5.
the power and light company test system is used as an
example. table 1 shows a part of the sequence generated by
srn and the mapping to the simulator actions.
Following the instructions in table 1, the dispatchers can
execute dispatch actions via the one-line diagram in ots and
observe the consequence of each action (see Figures 6 and 7).

following each restoration action, and so on. in other words,
this navigator would serve as a core application: a closedloop control in the system restoration process.

Benefits and Challenges
What Are the Costs and the Cost Savings?
the decision support system for power system restoration
serves as the essential component for the future self-healing
smart grid. as an extension of traditional power monitoring and control, it will integrate more advanced theory and
technology. part of the cost of the self-healing grid will be
incurred in modernizing the grid infrastructure to support

table 1. The sequence generated by SRN and OTS.
SRN Step Outline

Substation

Operation Action

At 0.00 min, restart
the generator on
bus 94.

CRWFRD

On bus 4, set Crawford
generator to MAN.

......

At 100.00 min,
crank the generator
on bus 93.

CRWFRD

On bus 3, set Crawford
generator to MAN.

Energize
transformer 94-91.

CRWFRD

Close breakers to
energize transformer
between buses 4 and 1.

Energize
transformer 91-93.

CRWFRD

Close breakers to
energize transformer
between buses 3 and 1.

......

Developing a Real-Time System
Restoration Navigator
the final stage is to develop a real-time system restoration navigator for online dispatch in response to extreme
events. such a navigator would have the ability to identify
system status, efficiently compute the restoration action
sequence, execute restoration actions automatically or under
the instruction from dispatchers, acquire the system's state
january/february 2014

figure 6. Operation actions in OTS.
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2014