C
o
p
yr
ig
h
t
©
2
0
0
8
X
i’
a
n
J
ia
o
to
n
g
U
n
iv
e
rs
it
y
C
o
p
yr
ig
h
t
©
2
0
0
8
X
i’
a
n
J
ia
o
to
n
g
U
n
iv
e
rs
it
y
电力系统过电压
Power System Overvoltage