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copulas, and correlated multivariate random vectors from f 1 (x) are generated. The
generated samples are for real power values only, and the reactive power at the
corresponding individual load buses are obtained by maintaining the power factor
constant.
5.2.3 Results and Discussions
The training database generated within the boundary region contains 2,852 oper-
ating conditions. The test database includes 1,976 independent instances unseen by
training set, covering a wide range of operating conditions. The candidate attributes
available for rule formation consists of 46 and 102 node voltages at 400 and 225 kV
voltage levels respectively, reactive power
fl
ows (Q
fl
flow) in 16 tie lines, real power
reserve (P res) in SEO from 10 generator group
'
s, and reactive power reserve (Q
res) in SEO from 10 generator group
s and 2 SVCs.
Table 4 shows the effectiveness of various combinations of attribute sets in terms
of classi
'
cation accuracy and error rates. Accuracy is de
ned as the percentage of
points correctly classi
ed, false alarm rate is de
ned as the ratio of total misclas-
si
ed unacceptable instances among all unacceptable classi
cations, and risk rate is
de
ed acceptable instances among all acceptable
classifications. The attribute set 400 kV + Q res proves to be a good set with
lowest risk and high classi
ned as the ratio of total misclassi
cation accuracy. It has to be noted that the accuracy
listed in the Table 4 are for trees that are pruned by restricting the minimum number
of instances per leaf node.
Effect of Bias Factor
P
This section sheds light on the quantitative impact of biasing the sampling process
towards the boundary region by presenting results for various values of bias factor
Table 4 Attribute set selection
Attribute Set
Accuracy
False alarm
Risk
Tree size
400 kV + Q res
87.9079
0.193
0.073
15
Q res
87.7159
0.183
0.083
15
225 kV
82.8215
0.243
0.124
15
400 kV + 225 kV
82.7255
0.253
0.12
15
400 kV + 225 kV + Q res
82.6296
0.236
0.132
13
All
82.6296
0.236
0.132
13
225 kV + Q res
82.4376
0.231
0.139
13
400 kV
80.8061
0.231
0.166
17
Q flow
75.5278
0.325
0.191
23
P res
73.8004
0.402
0.169
13
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