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To all whom it may concern: Be
it known that I, LLOYD C. NICHOLSON,
a citizen of the United States, and a resident of Buffalo, county of
Erie, State of New York, have invented certain new and useful
Improvements in Insulator-Protecting Apparatus, of which the following
is a specification. My
invention relates to improvements in protecting apparatus for insulators
and is more especially designed to prevent injury to high potential
insulators due to punctures and the arcs of the power current which
follow flash-overs. In
ordinary high potential electric systems when the voltage on the line
conductor rises abnormally due to lightning or other causes a flash-over
current is apt to take place over the surface of the insulator to the
pin beneath it and thence to the earth. If
this discharge current is of sufficient value to overcome the dielectric
strength of the medium and break it down an arc will follow, which arc
is due to the power current or voltage of the line. That is, the actual
discharge due to the high voltage of the lightning is of very short
duration but the heavy discharge which follows is due to the flow of the
power current which follows the flash-over when the dielectric strength
of the air has been broken down. The
insulators used in such high potential electric systems are usually of
glass or porcelain, which materials are very refractory and easily
injured by heat. Therefore, when such power arcs occur over the skirts
of the insulator the heat is apt to injure or wholly destroy it. To
prevent such destruction I place an electrode connected with the earth
so that when a flash-over and power arc occur thereon the whole arc is
diverted away from the insulator to the electrode so that it will not
injure the insulator. In
such high potential insulators there is also liability of the insulator
puncturing directly from the tie wire to the pin carrying the insulator,
or else only one or two of the skirts of the insulator may be punctured,
the discharge taking place over the surface of the remaining skirts. It
is another object of my invention to prevent or eliminate such punctures
and to do this without increasing the flash-over liability of the
insulator. Further objects features and advantages will
more clearly appear from the detailed description given below taken in
connection with the accompanying drawings which form a part of this
application. In
the drawings, Figure 1 is a vertical view of an insulator with
protecting apparatus embodying one form of my invention. Fig. 2 is a
similar view showing a modification in which a protecting covering is
applied to the main line conductor. Fig. 3 is a plan view of the
insulator and apparatus shown in Fig. 1. Fig. 4 is a vertical section of
the insulator and apparatus shown in Referring
to Figs. 1, 2, 3 and 4, 1 represents a main line high potential
conductor secured to the insulator 2 by means of a tie wire 3 passing
around the neck of the insulator. In Fig. 2 the tie-wire 3 is shown
wound about the main line wire 1 for a considerable space on each side
of the insulator, thus forming a metallic covering 4 for the conductor
1, giving body thereto to prevent the main line conductor from burning
apart when a heavy discharge takes place there from at the insulator.
This last feature, however, is not necessary to the attainment of
the principal objects of my invention. The
insulator 2 in the present instance is made up of three skirts 5, 6 and
7 and is secured to a pole or other base 8 by means of an iron pin 9.
The various skirts 5, 6 and 7 may be secured together and to the pin 9
by means of Portland cement 10. Bolted to the base of the iron pin 9 are metallic members 11
projecting upwardly and outwardly and carrying at their outer ends a
guard ring 12. The guard ring 12 is below or on the same side of the
horizontal plane of the conductor 1 as the insulator 2 and extends in
the form of a circle, about the insulator 2, at a height between the
skirts 6 and 7 and is somewhat larger in diameter than any of the
skirts, so that it is spaced therefrom and from the insulator 2.
The conducting member or pin 9 is thereby electrically connected
with the guard ring 12 by means of the metallic members 11 and the whole
is connected with the ground or earth by means of a conductor 13. Referring more especially to Fig. 4 the operation
of the guard ring 12 is as follows. When an abnormal voltage exists upon
the main line conductor 1 the same voltage exists upon the tie-wire 3.
This tends to increase the leakage current over the surface of the
insulator and if the voltage becomes large enough the dielectric
strength of the intervening medium will be broken down and a heavy
discharge will take place along the lines a, b, c, d, e, f and g to the
pin 9 and to earth. This heavy discharge which follows, however, is due
to the power current which will now flow from the conductor to the
ground over the path which has been broken down because of the initially
high voltage to which it has been subjected. The discharge immediately
forms into an arc which takes the path a—b, b—d, d--f, and f—g.
This arc passing directly over the skirts of the insulator and flaring
in all directions causes heating of the insulator and thereby often
injures or wholly destroys the same. In
order that the presence of the guard ring 12 may not cut down the
resistance offered by the insulator or increase the flash-over liability
thereof the initial resistance along the path a, h, k, is greater than
the initial resistance over the surface of the insulator along the path
a, b, c, d, e, f and g to the pin 9. By the term initial resistance I
intend to comprehend the tendency of the air gaps to resist the
discharge of current and not break down as well the tendency of the
conductors to resist the passage of current. The guard ring or electrode
12 is thus so situated that the initial resistance through the air or
surrounding medium between it and the conductor or tie-wire 3 is so
great that the initial discharge will not pass directly thereto along
the path a, h, k, but will take place over the surface of the insulator
to the pin 9 and thence to earth. However, immediately the arc has been
formed it takes the path a, b, d, f, g, and then because of its flaring
in various directions, it shifts to the point k at the guard ring 12 so
that the arc is drawn away from the skirts of the insulators and thus
prevented from doing damage thereto. In insulators constructed as shown in the figures it is a necessary
condition that the electrostatic capacity of a shell or part be less
than that of the shell or part into which it
fits. This is true because
the active dielectric area of the inner shell is smaller than the active
area of the outer shell into which it engages.
This condition causes more voltage to act upon the inner shell
per unit thickness, than upon the outer shell or shells when two or more
shells are assembled as shown. For
this reason when an abnormally high potential exists on an insulator the
inner part will have to resist more voltage per unit thickness than any
of the other parts. Thus,
when a high voltage acts the inner part is more liable to puncture than
the others. Also, if the inner part punctures the other parts may
puncture also because of the ineffectiveness of the inner part when
punctured. In
Fig 4 I have represented by line 1 the path of a puncture when taking
piece directly through all of the parts of the insulator.
However, if the dielectric strength of the skirt 5 is great
enough and its electrostatic capacity is large enough the discharge will
take piece over its surface along the dotted line m, but may puncture
skirts 6 and 7 along the dotted line n on account of the lower
electrostatic capacity of these parts. In a like manner if skirts 5 and
6 have sufficient dielectric strength and sufficient electrostatic
capacity the discharge will take place along the dotted line m o and
will puncture skirt 7 on account of its relatively low electrostatic
capacity. Since the
electrostatic capacity of the inner skirt is necessarily less on account
of the size of its top, than that of 6, and the capacity of 6 is for the
same reason less than 5, it is evident that skirt 7 is more liable to
puncture than skirt 6 and that skirt 6 is more liable to puncture than
skirt 5. Hence it is
apparent that if the skirt can be prevented from puncturing the puncture
of the outer skirts is likewise prevented.
The puncture of skirt 7 is prevented by means of the electrode or
guard ring 12 being placed at a position such that the dielectric
strength of the surrounding medium will be broken down between the
points d and k, before the surrounding medium will be broken down
between d and the pin 9 along the path d, e, f, g.
This result is accomplished therefore by causing the ring 12 to
slightly lower the flash-over value of the insulator below the point d. An additional advantage arising is that when a discharge occurs from d to
k it must come over the surface of the part of the insulator above d
along the path a, b, c, d. The
resistance of this path will tend to prevent a flash-over of the
insulator by power current. Such
resistance would not be effective if the entire insulator were relieved
by an initial discharge from cable 1 or tie-wire 3 directly to an
electrode placed for this purpose. It is of course desirable to prevent insulators from flashing
over by power
arcs since such action interferes with the continuous operation of the
electrical machinery and I attain this advantage and at the same time
prevent the various skirts 5 from puncturing in the efficient manner
above described. In
order that the heavy discharge taking place from the tie-wire 3 may not
burn the same apart because of its taking place at approximately a
single point I prefer to place around the neck of the insulator, in
contact with the tie-wire 3 a conducting ring or band 14. However, if the tie-wire is sufficient to withstand the
discharge the conductor or ring 14 may be omitted. Referring
to Figs. 5 and 6 I show a modified form of insulator much shorter than
that of Figs. 1, 2 and 4. The
insulator of Fig. 5 is provided with three skirts 15, 16 and 17 secured
to the metallic conducting pin 18 in the usual manner.
In such short insulators in order that the electrode or guard
ring 12 may not cut down the flash-over value of the insulator it may be
found desirable to place the same at a lower level than that of the
lowest skirt 17 of the insulator. In order that the operation of
preventing flash-over arcs from injuring the insulator may take place as
above described I provide a porcelain tube 19 surrounding pin 18 and
resting upon a flange 20 thereupon.
This causes the arc due to a flash-over immediately it has once
started to shift to the electrode or guard ring 12 rather than keep to
the longer path to the metallic pin 18.
In the arrangement shown in Figs. 5 and 6 the guard ring or
electrode 12 is secured directly to the pin 18 by means of metallic
braces 21 secured to the pin 18 by means of bolts 22.
In some arrangements it may not be necessary to use the porcelain
tube 19, since, although the ring 12 is placed below the lowest skirt of
the insulator yet the arc will readily shift to the guard ring because
of its flaring qualities. Although I have described my improved arrangements in great |
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detail I do not desire to be limited to such details but Having fully and clearly explained my invention what I claim as new and desire to secure by Letters; Patent is: 1.
In an arrangement of the class described, an electrical conductor, an
insulator therefor and an electrode on the same side of the horizontal
plane of the conductor as the insulator and so arranged that the
resistance from the conductor through the surrounding medium directly to
the electrode is greater than the resistance from the conductor to earth
when the discharge occurs over the surface of the insulator. 2. In an arrangement of the class described, an electrical conductor, an insulator therefor and an electrode in proximity to the insulator and connected with the earth and so
arranged that the initial resistance offered to a discharge between the
conductor and earth is greater when the path of the discharge is
directly through the surrounding medium than when it is over the surface
of the insulator. 3.
In an arrangement of the class described, an electrical conductor, an
insulator therefor and an electrode connected with the earth, arranged
on the same side of the horizontal plane of the conductor as the
insulator and so adjusted that the initial resistance offered to a
discharge from the conductor through the surrounding medium directly to
the electrode is greater than the 4.
In an arrangement of the class described, an electrical conductor, an
insulator therefor and an electrode connected with the ground and placed
on the same side of the horizontal plane of the conductor as the
insulator and lying outside of the insulator parts and arranged to
divert the arc away from the insulator parts when a flash-over and arc
occur thereon. 5.
In an arrangement of the class described, a conductor, an insulator
therefor, and means for diverting the arc from the insulator when a
flash-over and arc occur there on. 6.
In an arrangement of the class described, a power conductor, an
insulator therefor, and an electrode arranged to divert the power arc
from the insulator when a flash-over occurs over the surface of the
insulator. 7.
In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode connected with the ground and arranged to
divert the arc a way from the insulator when a flash-over occurs
thereon. 8.
In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode connected with the ground and spaced around
the insulator in a position to divert the arc thereto away from the
insulator when a flash-over and arc occur on the insulator. 9.
In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode placed at one side of the insulator and below
the top thereof for attracting the arc thereto away from the insulator
when a flash-over and power arc occur thereon. 10. In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode for diverting the arc thereto, away from the
insulator, when a flash-over and arc occur thereon, said electrode being
so arranged that the resistance through the surrounding medium directly
to the electrode is greater than the resistance from the conductor to
earth when the discharge
occurs over the surface of the insulator. 11.
In an arrangement of the class described, a conductor, an insulator
therefor, and a metallic electrode outside of the insulator parts and
connected with the earth, for diverting the arc away from the insulator
when a flash-over and arc occur thereon, said electrode being so
arranged that the initial resistance offered a discharge between the
conductor and the earth is greater when the path of discharge is
directly through the surrounding medium to the electrode than when it is
over the surface of the insulator. 12.
In an arrangement of the class described, a conductor, an insulator
therefor, a metallic pin for the insulator and an electrode connected
with the pin and with earth for diverting the arc away from the
insulator when a flash-over and arc occur over the surface of the
insulator. 13.
In an arrangement of the class, described, a conductor, an insulator
therefor, a conducting member extending beneath the insulator, and an
electrode electrically connected therewith and with earth for diverting
the arc away from the insulator when a flash-over arc occurs on the
surface, said electrode being placed on the same side of the conductor
as the insulator and outside thereof. 14.
In an arrangement of the class described, a conductor, an insulator
therefor having a plurality of skirts, and an electrode electrically
connected with earth for diverting the arc away from said skirts when a
flash-over and arc occur over the surface of the insulator. 15.
In an arrangement of the class described, a conductor, an insulator
therefor having a plurality of skirts, and an electrode electrically
connected with earth for diverting the arc away from said skirts when a
flash-over and arc occur over the insulator, said electrode being placed
outside of said skirts and below said conductor. 16.
In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode arranged to divert the arc from the insulator
when a flash-over and arc occurs over the insulator, said electrode
being in the form of a metallic ring extending substantially around the
insulator. 17.
In an arrangement of the class described, a conductor, an insulator
therefor, and an electrode electrically connected with earth for
diverting the arc away from the insulator when a flash-over and arc
occur on the surface thereof, said electrode being in the form of a
conducting ring extending substantially around the insulator below the
top thereof end spaced therefrom. 18. In an arrangement of the class described, a conductor, an insulator
therefor having a plurality of skirts, and an electrode electrically
connected with earth for diverting the arc away from said skirts when a
flash-over and arc occurs on the insulator, said electrode being in the
form of a conducting ring extending substantially around the insulator
between its top and bottom and spaced therefrom. 19.
In an arrangement of the class described, a conductor, an insulator
therefor having two skirts, the lower of said skirts having less
electrostatic capacity than the one above it, and an electrode arranged
so that the initial resistance from the upper skirt to the electrode
directly through the surrounding medium is less than the initial
resistance to said electrode when the path is over the surface of said
lower skirt and the initial resistance from the conductor to said
electrode is greater than either of the above mentioned resistances. 20.
In an arrangement of the class described, a conductor, an insulator
therefor having two skirts, the lower of said skirts having less
electrostatic capacity than the one above it, and an electrode arranged
on the same side of the conductor as the skirts and so that the initial
resistance from the upper skirt to the electrode directly through the
surrounding medium is less than the initial resistance of the path over
the surface of said lower skirt to earth, for preventing the lower skirt
from being punctured from abnormally high voltages. 21.
In an arrangement of the class described, a conductor, an insulator
therefor having two skirts, the lower of said skirts having less
electrostatic capacity than the one above it, and an electrode connected
with earth and arranged so that the initial resistance from the upper
skirt to the electrode directly through the surrounding medium is less
than the initial resistance to earth when the path is over the surface
of said lower skirt, said electrode being situated outside of the
insulator and between said skirts. 22.
In an arrangement of the class described, a conductor, an insulator
therefor having two skirts, the lower of said skirts having less
capacity than the one above it, and an electrode arranged to divert arcs
away from the skirts and also arranged so that the initial resistance
from the upper skirt to the electrode directly through the surrounding
medium is less than the initial resistance to earth when the path is
over the surface of said lower skirt, said electrode being connected
with the earth and in the form of a conducting ring extending around the
insulator and spaced therefrom. 23. In an arrangement of the class described, a conductor, an insulator
therefor having a plurality of skirts, one of said skirts being arranged
to have less electrostatic capacity than the others, and an electrode
arranged so that a discharge to it will pass over one skirt without
passing over another to prevent said skirt of low capacity puncturing
from abnormally high voltages, said electrode being connected to earth
and situated outside of said skirts below the top of the insulator. 24.
In an arrangement of the class described, a conductor, an insulator
therefor having a plurality of skirts, one of said skirts having the
smallest capacity, and an electrode so situated that a discharge to it
from the conductor will take place over one of said skirts and will take
place to it before puncturing said skirt of smallest capacity. 25.
In combination, a conductor, an insulator therefor having a plurality of
skirts, a conducting pin for the insulator, a guard ring extending
around the insulator outside thereof, and means for electrically
connecting said ring to said pin and to earth. 26.
In combination, a conductor, an insulator therefor having a plurality of
skirts, a pin for the insulator, a guard ring extending around the
insulator outside thereof and between the two lowermost of said skirts
and conducting members for connecting said ring to earth. 27. In an arrangement of the class described, a conductor, an insulator
therefor, an electrode electrically connected therewith and with earth
for diverting the arc away from the insulator when a flash-over and arc
occur on the surface thereof and a metallic covering on the conductor
near the insulator to prevent the conductor from burning
apart when such a flash-over takes place. 28.
In an arrangement of the class described a main line conductor, an
insulator therefor, a tie-wire for securing the conductor to the
insulator, an electrode for diverting the arc away from the insulator
when a flash-over and arc occur over the surface thereof and a
conducting ring about the neck of the insulator adjacent the tie-wire
for preventing injury to the tie-wire. 29.
The combination of a conductor, an insulator therefor having a plurality
of skirts, an electrode outside of said skirts and arranged so that a
discharge to it from the conductor will take place over one of said
skirts without passing over another of said skirts. 30.
The combination of a conductor, an insulator therefor having a plurality
of skirts, one of said skirts being arranged to have less electrostatic
capacity than another, and the electrode arranged so that the discharge
to it from the conductor will pass over the surfaces of the skirt having
the larger electrostatic capacity without passing over the surfaces of
he skirt having the lesser electrostatic capacity to prevent said last
mentioned skirt from puncturing from abnormal high voltages. In
testimony whereof, I have signed my name to this specification, in the
presence of two subscribing witnesses. LLOYD
C. NICHOLSON. Witnesses: F.
C. AVERILL, C. M. SEALY. |