Element Technologies
for All-solid Insulated Substation
Background
Electric power equipment which has been introduced in large quantities during period high
economic growth must be replaced in the near future, due to exceeding their designed lifetime,
30 years generally. For the power equipment introduced in the future, more exquisite
consideration of the environmental aspect than that for the conventional equipment is required.
Insulating oils and SF6 gas are used as an effective insulation medium broadly, but rigorous
management is necessary from the aspect of the fire disaster prevention and global warming. In
contrast, for a solid insulation medium, there is no environmental load by leakage and no fear of
fire accident.
We aim at the development of the next-generation substation which makes the best use of
solid insulation medium. We mainly investigate the element technologies in order to realize its
maintenance-freeness, intelligence, unitization as well as improvement of environmental
influence..
Principal results
(1) Proposal of an all-solid insulated transformer
We have proposed the following items for realization prospect of an all-solid insulated
transformer with large capacity.
(a) Improvement of heat dispersion radiation characteristics by adoption of the vertical
windings.
(b) Adoption of an electrical insulating materials with fillers with high thermal conductivity.
(2) Proposal of a compact all-solid insulated connection system
A flexible connection system is required to connect each power equipment in order to make
high flexibility in a layout of power equipment and minimize total setting space. We have
proposed a all-solid insulated connection system which has compact connection system,
"Hyper Connector" and a cable section with high flexibility.
Future Developments
We will improve the design and evaluation methods of the all-solid insulated substation, and
promote the investigations in extending the developed designing techniques to the ultra-highvoltage class substation as well as the distribution substation.
Transformer
Transformer
Winding
insulation Windings
巻線絶縁
巻線
・・・
Shape
Shape effect
effect of
of coil
coil windings
windings (conventional
(conventional and
and proposing
proposing
vertical
type)
vertical type)
Compared
Compared to
to the
the conventional
conventional windings
windings (left
(left side),
side), the
the
vertical
windings
(right
side),
which
we
have
vertical windings (right side), which we have been
been
proposing,
proposing, have
have aa flat
flat inner
inner thermal
thermal gradient
gradient due
due to
to
elimination
of
the
electrical
insulation
layer
between
elimination of the electrical insulation layer between
windings
windings that
that would
would be
be aa large
large heat
heat resistance.
resistance. This
This
lowers
the
maximum
inner
temperature.
lowers the maximum inner temperature.
・・・
・・・
・・・
Main主絶縁
insulation層間絶縁
Layer insulation
Windings
巻線 巻線絶縁
Winding insulation
Main insulation
主絶縁
・・・
Temperature
温度
Temperature
温度
Temperature
difference
温度差
位置
Position
位置
Position
(a) 従来型コイル
(a) Conventional
coil windings
(b)縦型コイル
(b) Vertical
type coil windings
半径方向の大きな熱絶縁となる
Having no electrical insulation
巻線間の電気絶縁層が無い
layer between windings
Design temperature : 135 °C at windings
Heat conductivity [W/m/K]
This area shows the possible
condition to design the allsolid insulated transformer.
×
▲
■
●
Filling material in a epoxy resin
Filling rate
Kind
(vol. %)
No filler
0
(Epoxy resin itself)
fructured particle
42.5
(Commercial base)
Spheroidized particle
35
(Commercial base)
Composite particles
40
Effect
Effect of
of filler
filler
We
We confirmed
confirmed that
that adequate
adequate filling
filling materials
materials with
with
high
high thermal
thermal conductivity
conductivity such
such as
as Aluminum
Aluminum Nitride
Nitride
(AlN)
(AlN) improves
improves the
the heat
heat dispersion
dispersion characteristics
characteristics of
of
an
an epoxy
epoxy resin.
resin. We
We confirmed
confirmed that
that obtained
obtained results
results
fulfill
fulfill the
the required
required specification
specification for
for the
the all-solid
all-solid
insulated
insulated transformer.
transformer.
Note: Plots show each estimated values at 135 ℃.
AC breakdown stress
for 0.5mmt specimen [kV/mm]
300
４５mm
４５mm
Imp. breakdown voltage [kV]
Connection system (Hyper Connector)
250
200
150
Mountain shape
Wavy shape
100
※Plots with allow show that the
breakdown occur at the bulk part of
50
0
(a) Mountain shape
(b) Wavy shape
Outer
Outer view
view of
of the
the Hyper
Hyper Connector
Connector (prototype)
(prototype)
0
1
2
3
4
5
Specimen number
6
7
Impulse breakdown voltage of the prototype Hyper Connector
Connection
Connection interface
interface shape
shape of
of Hyper
Hyper Connector
Connector
We
made
prototype
Hyper
Connectors
having
two
interface
shapes,
We made prototype Hyper Connectors having two interface shapes, (a)
(a) mountain
mountain shape
shape and
and (b)
(b) wavy
wavy shape,
shape,
which
were
subjected
to
impulse
breakdown
test.
As
a
result,
mountain
shape
could
withstand
higher
which were subjected to impulse breakdown test. As a result, mountain shape could withstand higher voltage
voltage
which
which was
was confirmed
confirmed from
from the
the electric
electric field
field calculation
calculation along
along the
the interface
interface which
which showed
showed that
that the
the maximum
maximum
stress
of
the
mountain
shape
was
lower
than
that
of
the
wavy
shape.
stress of the mountain shape was lower than that of the wavy shape.
Trial
Trial design
design of
of the
the Hyper
Hyper Connector
Connector
400
φ350
Trial design of 275 kV class Hyper Connector
The
The Hyper
Hyper Connector
Connector has
has following
following features;
features;
(a)
(a) Shrinkage
Shrinkage of
of longitudinal
longitudinal length
length by
by bent
bent interface.
interface.
(b)
(b) Prevention
Prevention of
of local
local stress
stress enhancement
enhancement by
by rounding
rounding
bent
bent interface.
interface.
We
We carried
carried out
out the
the trial
trial design
design of
of 275
275 kV
kV class
class Hyper
Hyper
Connector,
Connector, and
and we
we confirmed
confirmed that
that itit could
could be
be realized
realized
with
with aa size
size of
of 135
135 mm
mm in
in electrical
electrical insulation
insulation thickness,
thickness,
400
400 mm
mm in
in length,
length, and
and 0.04m
0.04m33 in
in volume.
volume.