where J is the set of benefit attributes and J
0 is the set of cost
attributes.
The evaluation values of attributes can be obtained as follows:
(1) Safety margin of switching overvoltage
Aso ¼ ðUallows UactualsÞ=Uallows ð2Þ
where Uallows is the maximum allowable switching overvoltage;
Uactuals is the actual maximum switching overvoltage.
(2) Safety margin of sustained power frequency overvoltage
Aspfo ¼ ðUallowpf UactualpfÞ=Uallowpf ð3Þ
where Uallowpf is the maximum allowable sustained power
frequency overvoltage; Uactualpf is the actual maximum sustained
power frequency overvoltage in restoration.
(3) Frequency fluctuation caused by load pick-up
Aff ¼ ðf f minÞ=Df max ð4Þ
where f is the actual frequency of power system; fmin is the
minimum allowable frequency; Dfmax is the maximum allowable
frequency fluctuation.
(4) Characteristics and importance of load/unit.
It can be obtained by the experience of decision makers,
analytic hierarchy process (AHP) or expert rules [21]. The importance
is defined according to the priority of the load/unit and the
network structure.
(5) Restoration duration
As stated in Section ‘Determination of restoration schemes’,
restoration path is obtained by the two-layer path searching
method. And the restoration duration is estimated according to
T