INSULATING SPACER WITH BUILT-IN OPTICAL FIBER
[Teclmical Field]
[0001]
The present invention relates to an insulating spacer with built-in optical fiber particularly
to such an insulating spacer with built-in optical fiber as includes an optical fiber for use in an
optical current transformer for measuring electrical current.
[Background Art]
[0002] .,
A gas insulated switchgear (hereinafter referred to as "GIS") has such a construction that,
in coupling a plurality of cylindrical containers in which high-voltage electric conductors or
various high-voltage apparatuses are accommodated, sealed compartments are formed using
disk -shaped insulating spacers formed from insulating material such as epoxy resin and each of
the sealed compartments of the cylindrical container is filled with insulating gas.
[0003]
For the measuring of current flowing through the electric conductors in the cylindrical
container, a GIS uses a wound-type current transformer or an optical current transformer that
uses an optical fiber having Faraday-effect. Since small sizing and weight reducing is a
requirement of a GIS, use of the current transformer particularly considers employing an optical
current transformer, which offers size reduction to a larger degree compared with a wound-type
current transfonner. As a current transformer for GIS use, an optical current transformer that
Japanese Patent Laid-open Application No. Hei 10-142265 (Patent literature I) describes is
known.
[0004]
The optical current transformer described in Patent literature 1 is installed in a mrumer as
follows: In coupling a plurality of cylindrical tanks having flanges for connection, a three-phase
insulating spacer of insulating material that has electric conductors for three phases is disposed
between the flanges in a sandwiched mrumer. In this three-phase insulating spacer, optical fibers
of Faraday-effect element to form optical paths for light transmission and light reception are
embedded severally surrounding each of the three-phase electric conductors.
[0005]
On the optical fiber for light transmission, a setup of devices for the light transmission
side, comprised of a light source, a polru·izer, ru1d other related elements, is ruTanged outside the
tank; and likewise on the optical fiber for light reception, a setup of devices for the light
reception side (detector side), comprised of an analyzer, a measuring instrument, and other
related elements, is mTanged outside the tank. Thereby, an optical current transformer is formed.
In the optical current transformer, a linearly polarized light is injected into the optical path from
the light emission side for transmission, and at the detector side, the transmitted light is detected
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and measured for its Faraday rotation angle, magnitude of which is dependeht on the intensity of
action of magnetic field generated by current flowing through the electric conductor, and thereby
the magnitude of the current in the electric conductor is determined.
[0006]
On the other hand, a zero-phase current transformer for gas insulated electrical
apparatuses has been disclosed in Japanese Laid-open Patent Application No. Hei 8-178987
(Patent literature 2). The configuration of this zero-phase current transformer is as follows: An
optical fiber of Faraday-effect element is embedded in a three-phase insulating spacer having
electric conductors for three-phase, encircling all the electric conductors of three-phase in one
lump over the zero-phase current detection section of such electric conductors. On each end of
the optical fiber, a setup of devices for the light transmission side and a setup of devices for the
light reception side are severally arranged. Thereby, the zero-phase current is determined based
on the polarization signal outputted through the optical fiber.
[0007]
The optical cmrent transformer described in Patent literature 1 stated above uses such an
insulating spacer that optical fibers are embedded therein severally surrounding the electric
conductor of each phase; and the zero-phase current transformer described in Patent literature 2
uses an insulating spacer that an optical fiber is embedded therein surrotmding all the electric
conductors of three-phase in one lump. These insulating spacers are manufactured using, in
general, insulating material such as epoxy resin.
[0008]
Usually, an insulating spacer of insulating material may sometimes involve a tiny gap,
which is commonly referred to as a void, during molding process of embedding electric
conductors. This tiny gap causes corona discharge because of electric field formed by electric
conductor energizing and possibly brings about electrically adverse effect. Further, there is a
problem. Securing the insulating spacer on the flange of the cylindrical tank needs use of a
plurality of through bolts; the through bolts disturb the uniformity of electric field around the
outer periphery of the insulating spacer. To avoid this kind of harmful influence, a configmation
has been employed in which a grounding shield that sunounds electric conductors as a whole is
molded in the insulated spacer in one lump, and thereby, the electrical adverse effect attributable
to tiny voids is prevented by the grounding shield.
[0009]
It may be practicable to add a grounding shield in manufacturing the insulating spacer of
Patent literatures 1 and 2. However, the simultaneous molding of electric conductors together
with an optical fiber and further with a grounding shield integrally into one body does not
sufficiently eliminate the electrical adverse effect attributable to tiny voids; this is a problem
against an eased manufactW'ing.
[0010]
An object of the present invention is to provide an insulating spacer with built-in optical
fiber, which includes an optical fiber for current transformer use, having features such that
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manufacturing is easy and economical, such that corona discharges attributable to electric field
concentration in tiny gaps will not be generated, and such that the properties of the current
transformer will not be affected.
[Disclosure of Invention]
[0011]
The present invention is characterized in that, in constituting an insulating spacer with
built-in optical fiber by embedding in an insulating molded member molded as a single body
with insulating material; at least one electric conductor; a grounding shield surrounding the
electric conductor; an optical fiber of Faraday-effect element; the electric conductor, the
grounding shield and the optical fiber, being embedded in the insulating molded member, and
further the grounding shield is formed of a cylindrical shielding member, and the optical fiber is
put in a certain place in the cylindrical shielding member.
[0012]
Preferably, the cylindrical shielding member is characterized by being formed of a metal
wire cylindrical member made of a helically wound metal wire.
[0013]
Or, preferably, the cylindrical shielding member is characterized by being formed of a
strip-metal cylindrical member made of strip-shaped metallic material, a metal-net cylindrical
member made of metal wires, or a cylindrical metal member having a plurality of small holes
perforated thereon.
[Advantageous Effects oflnvention]
[0014]
Since an optical-fiber-contained insulating spacer of the present invention is structured in
a manner as stated above, the optical fiber of Faraday-effect element, which forms a current
transformer, and the cylindrical shielding member can be molded being embedded in the
insulating molded member; therefore, the invention has an advantage that manufacturing is easy
and economical.
[00 15]
Further, the optical fiber of Faraday-effect element itself is arranged in the certain place in
the cylindrical shielding member to be grounded. Therefore, even if a tiny void comes to exist in
proximity to the optical fiber at the time of resin molding process of the insulating spacer, this
configuration offers an advantage in that voltage applied to the electric conductor does not cause
corona discharge, which is attributable to the concentration of electric field, near the cylindrical
shielding member and does not affect the properties of the current transformer, because the
cylindrical shielding member is being grounded.
[Brief Description of Drawings]
[0016]
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Fig. 1 is a partly sectioned schematic side view of an insulating spacer with built-in
optical fiber that is an embodiment of the present invention.
[00 17]
Fig. 2 is a sectional schematic view of the insulating spacer with built-in ?Plical fiber
illustrated in Fig. 1 when viewed from the line A-A in Fig. 1.
[00 18]
Fig. 3(a) is a sectional view of a part of the insulating spacer with built-in optical fiber
illustrated in Fig.!. Fig. 3(b) is a sectional view of a part of the insulating spacer with built-in
optical fiber illustrated in Fig. 2.
[00 19]
Fig. 4 is a schematic illustration of an example of the grounding shield to be used in the
insulating spacer with built-in optical fiber illustrated in Fig. 1 and Fig. 2. .,
(0020]
Fig. 5 is a sectional schematic view of another example of embodiment of the present
invention when viewed the insulating spacer with built-in optical fiber illustrated in Fig. 1 from
the line A-A in Fig.!.
[0021]
Figs. 6(a) to 6(c) are schematic illustration of grounding shields each of which is to be
used in the insulating spacer with built-in optical fiber illustrated in Fig. 5.
[Best Mode of Can-ying Out the Invention]
[0022]
The optical-fiber-contained insulating spacer of the present invention is formed by
embedding in an insulating molded member molded as a single body by molding with using an
insulating material at least one electric conductor, a grounding shield surrounding the electric
conductor, and an optical fiber of Faraday-effect element. The grounding shield uses a
cylindrical shielding member, and an optical fiber is arranged in approximate center thereof. The
optical fiber to be build-in is used as a component of a current transfonner for current measuring.
[Embodiment 1]
(0023]
The following provides a detailed explanation of an insulating spacer with built-in optical
fiber of the present invention (hereinafter may be referred to as an insulating spacer, as the case
may be) referring to Fig. 1 to Fig. 4. An insulating spacer 1 illustrated in Fig. 1 is for singlephase
use. The insulating spacer 1 has an electric conductor 2 that provides electrical connection
between center electric conductors in a cylindrical tank and an insulating molded member 3 that
secures the electric conductor in position.
[0024]
On a flange 11 formed on the outer periphery of the insulating molded member 3, a
plurality of connection fitting 12 is disposed at regular intervals. The connection fittings 12 are
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embedded by molding insulating material such as epoxy resin to form the insulating molded
member 3 of integrated one body having a disklike shape or a conical shape. The flange 11 of the
insulating spacer 1 is sandwiched between flanges of the cylindrical tanks. \he inside of each of
the cylindrical tanks is partitioned by the insulating spacer 1.
(0025]
In the example illustrated in Fig. I to Fig. 3, an optical fiber 14 of the Faraday-effect
element for use in a current transformer is disposed in proximity to the flange 11 of the
insulating spacer 1 surrounding the electric conductor 2 and embedded in the insulating molded
member 3. In this configuration, a grounding shield is formed of a cylindrical shielding member
15 and the optical fiber 14 is disposed at a certain place in the cylindrical shielding member 15,
preferably in the proximity to the center thereof, in order that the distance be\Ween the optical
fiber 14 and the electric conductor 2 will be maintained within a prescribed range. Thus, the
insulating spacer 1 having such a constmction as does not cause any adverse effect on the use in
an optical current transformer, is provided.
(0026]
The mrumer of fabricating the insulating spacer 1 by molding the cylindrical shielding
member 15 and the optical fiber 14, which is to be disposed inside thereof, in the insulating
molded member 3 embedding them is as follows: The optical fiber 14 is put in a state being
supported in the certain place in the cylindrical shielding member 15 with a supporting member.
The optical fiber 14 is easily supported in the certain place with a supporting member, because
the cylindrical shielding member 15 is used.
[0027]
The cylindrical shielding member 15 is connected to the connection fitting 12 tlu·ough a
grotmding wire 13, which also works as a fixing wire, as illustrated in Fig. 1 to Fig. 3. Thereby,
the cylindrical shielding member 15 establishes its electrical connection with the connection
fitting 12 and is mechanically retained in the certain place; and such setup is placed within a
molding tool. Thereafter, molding process is applied using insulating material such as epoxy
resin to obtain the insulating spacer 1.
(0028]
The cylindrical shielding member 15 uses a metal wire cylindrical member 15A formed
of helically wound metal wire, as illustrated in Fig. 4 for example, having good workability such
as copper wire or aluminum wire. As a matter of course, the metal wire to be used therefor
should have such a thickness as is capable of maintaining a cylindrical shape as the cylindrical
shielding member when formed in a helically wound shape.
[0029]
The metal wire cylindrical member !SA formed by helically winding metal wire is
stmctured in order to have a characteristics as a grounding shield and molded with insulating
material with the optical fiber 14 being positioned inside thereof to complete forming the
insulating molding member 3. Thereby, both the optical fiber 14 and the metal wire cylindrical
member 1 5A are embedded in a certain place in the insulating molded member 3 and configured
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in order that the optical fiber 14 will be positioned at the distance within a p:escribed range from
the electric conductor 2.
[0030]
In the example of arrangement of the optical fiber 14 illustrated in Fig. 2 and Fig. 3(b),
the optical fiber 14 is installed being led out in order that both ends thereof will protrude from
the insulating molded member 3 and the cylindrical shielding member 15, which works as the
grounding shield, is provided on both of the led-out ends of the optical fiber 14.
[0031]
Where the optical fiber 14 is used as a component of a reflection type.,current transformer,
a mirror portion 17 is formed on one end of the optical fiber 14, and a light transmission side
device and a light reception side device are an·anged on the other end. Thereby, an optical
current transformer is constituted. The optical fiber 14 is usable as a component of a
transmission type device. In this usage, a light transmission side device is installed on one end of
the optical fiber 14 and a light reception side device for current detection is arranged on the other
end. Thereby, an optical current transformer is constituted.
[0032]
By constituting the insulating spacer with built-in optical fiber in a manner as stated
above, the insulating spacer I can be mold-formed with the optical fiber 14 for use in the optical
cmTent transformer arranged inside the cylindrical shielding member 15 that works as the
grounding shield and with such arrangement embedded inside the insulating molded member 3;
thereby, an insulating spacer can be manufactured easily and economically. Further, no adverse
electrical effect will appear attributable to generation of corona discharge due to concentration of
electric field at a tiny void caused by voltage applied on the electric conductor 2, since the
optical fiber 14 itself is arranged in the certain place in the cylindrical shielding member 15 that
is to be grounded. Accordingly, the properties of the optical cll!Tent transformer will be given no
damages.
[Embodiment 2]
[0033]
Next, an insulating spacer with built-in optical fiber I as another example of the present
invention will be explained referring to Fig. 5 and Fig.6. The insulating spacer I in this
explanation is for single-phase use similarly to the example illustrated in Fig. 1 to Fig. 3 and has
an electric conductor 2 and an insulating molded member 3 like the example stated previously.
As Fig. 6(a) to Fig. 6(c) illustrate, a cylindrical shielding member 15 having a mechanically stout
construction is used and an optical fiber 14 is arranged in the center thereof.
[0034]
As the cylindrical shielding member 15, a strip-metal cylindrical member 15B made of
strip-shaped metallic material is used in the example illustrated in Fig. 6(a), a metal-net
cylindrical member 15C made of metal wires is used in the example illustrated in Fig. 6(b ), and a
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cylindrical metal member 15D having a perforation 16 of a plurality of small holes thereon is
used in the example illustrated in Fig.6 (c).
[0035]
This insulating spacer with built-in optical fiber thus formed is capable of attaining a
similar effect to that of the above-stated embodiment and does not incur large deformation in
mold-forming the insulating molded member 3 using insulating material such as epoxy resin
since the cylindrical shielding member 15 has a mechanically stout construction; this offers more
eased manufacturing.
[0036]
Explanation of each of the embodiments mentioned above has described on a singlephase
insulating spacer as an example. The present invention is also applicable to a three-phase
insulating spacer having such a configuration that tlu·ee munbers of electric conductor 2 are
arrayed in a parallel-flat style or in such an arrangement that lines linking the vertices thereof
form an equilateral triangle or an isosceles triangle and are integrally molded into a single body
of the insulating molded member 3. In this case, the optical fiber 14 and the cylindrical shielding
member 15 are installed in order that the electric conductor 2 of each phase will be severally
surrounded thereby and an overall shielding is provided in order that all the electric conductors 2
for three-phase are surrounded thereby in one lump, and they are molded using insulating
material to form the insulating molded member 3.
[0037]
The explanation stated above has described on an example in which the optical fiber 14 to
be built-in the insulating molded member 3 is applied to an optical current transformer. It is
obvious that the construction, in which the optical fiber 14 is arranged inside the cylindrical
shielding member 15 followed by resin-molding to form the insulating spacer I, is applicable to
a zero-phase em-rent transformer attaining a similar advantageous effect.
[Industrial Applicability]
[0038]
The invented insulating spacer with built-in optical fiber is suitable for a gas insulated
switchgear of single-phase and three-phase, without any problems in use.

Claims
1. An insulating spacer with built-in optical fiber comprising:
an insulating molded member molded as a single body with insulating material;
at least one electric conductor;
a grounding sHield surrounding the electric conductor;
an optical fiber of Faraday-effect element;
the electric conductor, the grounding shield and the optical fiber, being embedded in the
insulating molded member,
wherein the grounding shield is formed of a cylindrical shielding member, and the optical fiber is
put in a certain place in the cylindrical shielding member.
2. The insulating spacer with built-in optical fiber according to claim 1, wherein the
cylindrical shielding member is fmmed of a metal wire cylindrical member made of a helically
wound metal wire.
3. The insulating spacer with built-in optical fiber according to claim I, wherein the
cylindrical shielding member is formed of a strip-metal cylindrical member made of strip-shaped
metallic material.
4. The insulating spacer with built-in optical fiber according to claim l, wherein said
cylindrical shielding member is formed of a metal-net cylindrical member made ofmeta1 wires.
5. The insulating spacer with built-in optical fiber according to claim l, wherein the
cylindrical shielding member is formed of a cylindrical metal member having a plurality of small
holes perforated thereon.