Electrical power transmission line

An electrical power transmission line is particularly adapted for the transmission of electrical power from relatively small and remotely located hydroelectric sites and over rugged terrain. The line has a plurality of conducting elements, preferably assembled from copper tubing or pipe with loosely fitting slip joints to allow for thermal expansion, with concentric outer insulating elements of polyvinyl chloride pipe or tubing, which insulating elements are hermetically sealed together. The conducting element is spaced apart from the inner walls of the insulating element by plural spacers installed therebetween, to provide an air gap between conductor and insulator. The use of a combination of standard, off the shelf components provides a relatively economical construction, with the relatively light weight of the components providing for shipment by air to remote sites and the standardization of the components providing for ease of assembly in remote areas by relatively unskilled labor using minimal hand tools and equipment, without need for the construction of a right of way for a conventional electrical power line. A method of constructing such a line is also disclosed.

FIELD OF THE INVENTION 
The present invention relates generally to electrical power lines, and more 
specifically to a line particularly adapted to be constructed from readily 
available, off the shelf components for carriage by relatively small 
aircraft to assembly sites in relatively rugged and inaccessible terrains. 
The present power transmission line is particularly adapted for use with 
smaller hydroelectric generating systems, which do riot require large dams 
and other labor and material intensive systems or plants. 
BACKGROUND OF THE INVENTION 
Hydroelectric power, where electrical power is generated by means of 
generators or dynamos powered by the force of falling water turning a 
turbine wheel, is used to generate a relatively small percentage of the 
electrical power used in North America. A major reason for this is that by 
their very nature, the best sites for such hydroelectric power plants are 
in relatively rugged terrain with relatively large elevation changes, in 
order to provide the fall necessary to produce sufficient water force to 
spin the turbine(s) efficiently. 
Such terrain floes not generally provide for ease of travel thereover 
Almost by definition, such country is generally relatively remote, thus 
making it technically difficult not only to construct dams and associated 
hydroelectric power generating plants, but also to construct the required 
electrical transmission lines from the remote power generation site. 
Most hydroelectric power systems are located in the western part of the U. 
S. and Canada, where the terrain is favorable for large scale 
hydroelectric generating systems. However, many other areas are suitable 
for such hydroelectric power generation, but are precluded from 
consideration for major dams and plants either due to the remoteness of 
the site, or the relatively small elevation changes of the terrain. Many 
such sites are easily adaptable to smaller, relatively easily 
transportable generators, turbines, and penstocks, which apparatus may be 
transported by air to remote sites, thus eliminating any need for roads 
and associated support facilities to be constructed for a major 
hydroelectric project. 
However, the problem still exists to transmit economically the electrical 
power generated by such smaller and remote sites, to other areas where it 
is needed. Conventional overhead electrical power lines are generally 
unsatisfactory, due to the need to clear a right of way through possibly 
heavily forested and rugged terrain. While such construction may be 
economically feasible for the transmission of larger amounts of power from 
larger generation sites, clearly the erection of such power line 
technology adapted for the transmission of massive amounts of power is 
unsuitable for use with smaller, low head generators capable of providing 
only relatively small amounts of power. 
Accordingly, the need arises for an electrical power transmission line 
which may be easily assembled from readily available, off the shelf 
components and is particularly adapted for use in remote and rugged 
terrain. The components must be readily transportable by air, and capable 
of assembly without need to construct graded or otherwise formed rights of 
way, and without need for sophisticated technology or tools, by workers in 
the field. 
DESCRIPTION OF THE PRIOR ART 
U.S. Pat. No. 2,410,802 issued to John C. Bain on Nov. 12, 1946 discloses a 
Concentric Conductor Transmission Line wherein both concentric portions 
are conductors, rather than the inner electrically conductive portion and 
surrounding outer electrically insulating portion of the present 
transmission line. Bain also provides passages through the outer conductor 
to access the inner conductor, whereas the outer insulating portion of the 
present invention is preferably completely sealed. Bain is particularly 
adapted for use as a relatively high frequency wave guide, rather than as 
an electrical power line, as in the present invention. 
U.S. Pat. No. 3,356,785 issued to Yasuhisa Yoshida et al. on Dec. 5, 1967 
discloses Electric Transmission Coaxial Cables generally along the lines 
of the Bain apparatus discussed above, i.e., having concentric inner and 
outer conductors, rather than an inner conductor and outer insulating tube 
or pipe, as in the present invention. The spacers between inner and outer 
conductors are specially configured, and are not "off the shelf" 
components as used in the present invention. 
U.S. Pat. No. 3,639,864 issued to Bernt Klostermark on Feb. 1, 1972 
discloses Transportable Coaxial Cable comprising alternating lengths of 
relatively flexible and rigid coaxial conductors. Again, the present 
invention has no external conductor, but comprises an internal conducting 
element and a substantially coaxial electrically insulating element. The 
present external insulator is relatively flexible and pliable throughout 
its length, while the internal electrical conductor is relatively rigid; 
these characteristics are substantially uniform throughout the conductor 
length, unlike the Klostermark coaxial conductor. 
U.S. Pat. No. 4,047,166 issued to G. Kirby Miller on Sep. 6, 1977 discloses 
an Electrostatically Charged Cable Transducer comprising two flexible 
coaxial conductors loosely contained in an outer insulating tube. The two 
flexible conductors are unlike the single relatively rigid conductor of 
the present invention, and moreover the Miller coaxial conductors rest 
against the inner wall of the outer insulating tube, rather than being 
held substantially coaxially therein. The relative flexibility of the 
various elements is opposite that of the present invention, where the 
central conductor is relatively rigid and is housed in a relatively 
flexible insulating pipe or tube 
U.S. Pat. No. 5,094,735 issued to Donald C. Lang, Jr. on Mar. 10, 1992 
discloses a Plating Workstation Support providing for the electrochemical 
insulation of a central conductor, while still providing for radial 
electrical connection to a plurality of plating clamps or hangars. The 
only similarity of the Lang, Jr. apparatus to the present invention is the 
use of polyvinyl chloride (pvc) tube for the outer insulator. The present 
conductor is devoid of any passages therethrough, and is preferably 
hermetically sealed to protect the inner conductor. The inner conductor is 
suspended by insulators in the present invention, rather than radially 
disposed conductors as in Lang, Jr. The central elongate conductor of 
Lang, Jr. is a solid bar with a dissimilar chemically relatively inert 
coating thereon, unlike the plurality of members in movable mechanical and 
electrical contact with one another, provided by the present invention. 
Almost none of the Lang, Jr. components are "off the shelf," as provided 
by the present invention. 
U.S. Pat. No. 5,203,378 issued to David A. Williams on Apr. 20, 1993 
discloses a High-Flexibility, Noncollapsing Lightweight Hose adapted for 
the transport of fluids; no electrical conductivity is disclosed. The hose 
is considerably more flexible than any component of the present invention, 
particularly the relatively rigid internal conducting member. Williams 
further discloses vent holes within inner coupling sleeves; the present 
invention provides continuous, unbroken walls in both the inner conducting 
element land the outer insulating element. None of the Williams elements 
may be considered a standard, "off the shelf" article, as used by the 
present invention. 
Finally, U.S. Pat. No. 5,345,520 issued to Mark E. Grile on Sep. 6, 1994 
discloses an Electrical Connector With An Optical Fiber Connection 
Detector. An optical fiber passes through the side of each electrical 
connector, to be matched up when the connectors are properly connected. 
The present invention does not provide for any other elements to enter the 
side wall of the conductor and extend through the interior of the 
conductor in any way. Moreover, the Grile device discloses only a solid 
insulator in direct physical contact with the interior conductor, and a 
passage through the side of the conductor for the optical fiber, unlike 
the unbroken walls of the elements of the present invention. Again, Grile 
uses a specially formed connector, rather than a combination of standard 
components as disclosed in the present invention. 
None of the above noted patents, taken either singly or in combination, are 
seen to disclose the specific arrangement of concepts disclosed by the 
present invention. 
SUMMARY OF THE INVENTION 
By the present invention, an improved electrical power transmission line 
ills disclosed. 
Accordingly, one of the objects of the present invention is to provide an 
improved electrical power transmission line which is particularly adapted 
to assembly and use in relatively remote and rugged terrain, and which 
utilizes standard components. 
Another of the objects of the present invention is to provide an improved 
electrical power transmission line which comprises an inner conducting 
element and an outer insulating element, with the conducting and 
insulating elements being concentric and spaced apart from one another by 
a plurality of insulating spacers. 
Yet another of the objects of the present invention is to provide an 
improved electrical power transmission line which inner conducting and 
outer insulating elements each are formed to have continuous and unbroken 
walls, with the outer insulating element being formed of a plurality of 
individual elongate tubular components hermetically sealed together and 
the inner conducting element being formed of a plurality of elongate 
components loosely jointed together to allow for thermal expansion and for 
the transmission of electrical current. 
Still another of the objects of the present invention is to provide an 
improved electrical power transmission line which utilizes relatively 
flexible polyvinyl chloride pipe for the outer insulator and relatively 
rigid copper pipe for the inner conductor. 
A further object of the present invention is to provide a method of 
constructing an improved electrical power transmission line according to 
the present invention. 
A final object of the present invention is to provide an improved 
electrical power transmission lane for the purposes described which is 
inexpensive, dependable and fully effective in accomplishing its intended 
purpose. 
With these and other objects in view which will more readily appear as the 
nature of the invention is better understood, the invention consists in 
the novel combination and arrangement of parts hereinafter more fully 
described, illustrated and claimed with reference being made to the 
attached drawings.

Similar reference characters denote corresponding features consistently 
throughout the several figures of the attached drawings. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now particularly to FIG. 1 of the drawings, the present invention 
will be seen to relate to an electrical power transmission line 10, which 
is particularly adapted for installation and use across relatively rugged, 
remote and inaccessible terrain. (While only a relatively short length of 
the present transmission line 10 is shown in FIG. 1, it will be understood 
that the line 10 is of indeterminate length and may be made to any 
practicable length as required. The portion of the line 10 shown in FIG. 1 
is sufficient Co display the various features of the outer insulating 
portion of the line 10.) 
The outer portion 12 of the electrical power transmission line 10 is formed 
of electrically insulating pipe or tube components 14, which are joined 
together by mating connecting components, such as sleeves 16, 45 and 90 
degree elbows 18 and 20, etc; it will be understood that other standard, 
off the shelf fittings and components may be used as required. Where it is 
necessary to elevate a portion of the line 10, one or more braces or 
compression struts 22 may be used to support that portion of the line 10. 
The same type of material, preferably a polyvinyl chloride plastic pipe, 
may be used for the bracing struts 22, as well as for the remainder of the 
outer electrically insulating components 12 through 18 of the transmission 
line 10. While other materials may be used for the outer electrical 
insulating portion, it has been found that the ease of assembly (using 
suitable solvent), the relative flexibility, light weight, ready 
availability, and resistance to temperature extremes often found in remote 
areas, makes such polyvinyl chloride pipe an extremely suitable material 
for the outer insulating portion 12 of the electrical line 10. 
FIG. 2 discloses a partial cross sectional view of a typical portion of the 
present electrical power transmission line 10, in which half of the outer 
electrically insulating portion 12 is removed to show the inner, 
electrically conducting portion 24 and other features. The internal 
conducting portion 24 is formed similarly to the outer insulating portion 
12, with a plurality of elongate conducting sections 26 and connecting 
components comprising sleeves 28 and 45 and 90 degree elbows 30 and 32, as 
well as other connecting components as required. 
A conducting material with good electrical conductivity properties is 
preferred, as well as a material which components are readily available in 
relatively economical standard "off the shelf" configuration without need 
to manufacture components specially. While the electrical conductor may be 
formed of solid elongate components, such components as the connecting 
sleeves and elbows 28 through 32 are readily available for the assembly of 
copper pipe; hence, the use of mating hollow copper pipe for the elongate 
sections is desirable, to provide for ease of assembly with the connecting 
components. The copper pipe may be provided in a diameter to provide 
sufficient wall thickness to be equivalent to the desired cross sectional 
area of a standard solid wire conductor as required for the length of the 
transmission line 10 and other factors. 
Preferably, the various electrically conductive components are assembled 
without, tightly securing the various joints, so that the elongate 
sections 26 may move within the connectors 28 through 32. This provision 
for movement allows for thermal expansion and contraction, as shown in 
FIG. 3 of the drawings and discussed in detail further below. 
The outer insulating portion is preferably hermetically sealed at the 
various joint fittings, as at joints 34, by using a solvent compound 
therebetween to fuse and chemically weld the fittings together. This type 
of assembly results in an impermeable outer insulating portion 12 when 
properly accomplished, thus hermetically sealing the inner conductor 
portion 24 within the hollow outer insulator portion. This has the 
advantage of sealing out moisture and other contaminants land thus 
substantially reducing any corrosion, and resulting higher electrical 
resistance, which might occur at the various slip joints of the internal 
conductor portion 24 within the outer insulating portion 12. 
Preferably, the inner conducting portion 24 of the present transmission 
line 10 is held in place substantially concentrically within the outer 
electrically insulating portion 12, in order to allow an equal amount of 
space surrounding the conductor 24 for thermal expansion and contraction 
relative to the outer insulator portion 12, as required. The use of a 
plurality of separated spacers 36 preferably formed of an electrically 
insulating material (e.g., flat polyvinyl chloride or other plastic sheet 
material) serves this function. The spacers 36 may be easily and quickly 
formed by cutting the sheet material into squares having a diagonal 
dimension slightly larger than the internal diameter of the outer 
insulating portion 12, and punching or otherwise forming a center hole in 
each sized to closely fit the outer diameter of the electrical conductor 
portion. These spacers 36 may then be slipped over the outside of the 
inner conductor 26, and pushed into the outer insulator 12 as required; 
the corners 58 will bend or fold to provide a tight fit within the outer 
insulator 12, as shown FIGS. 4 and 5, or may be trimmed as needed for a 
good fit. 
The spacers 36 are shown in an assembled state in the partially sectioned 
views of FIGS. 2 and 3, and individually in detail in the sectioned views 
of FIGS. 4 and 5. It will be noted particularly in FIG. 4, that the 
spacers 36 are sized so that their corners 38 interfere with the internal 
wall of the outer insulating portion 12, as noted above, for a tight fit 
within the outer portion 12. However, these spacers 36 are nevertheless 
preferably sufficiently small so that their side dimensions are smaller 
than the internal diameter of the outer portion 12. Thus, a gap or air 
space 40 will remain between each side of each spacer 36, and the adjacent 
inner wall of the outer insulator 12, as shown in FIG. 4. This provision 
allows any air trapped within the outer insulator 12 to flow throughout 
the insulator tube 12, thus precluding any pressure buildup or 
differential between sections due to temperature changes or other reasons, 
which might otherwise distort or damage the outer insulator 12 or any of 
the spacers 36 therein. 
Preferably, the spacers 36 are positioned sufficiently far from any major 
angular joints in the transmission line, to allow for some movement of the 
internal conductor portion 24 relative to the outer insulator 12, as shown 
in FIG. 3. The thermal coefficient of expansion of the conductor portion 
24 will likely be greater than that of the surrounding insulating portion 
12, as will be the case with a copper tube or pipe conductor and a 
polyvinyl chloride plastic insulator. The provision of movable or slip 
joint assemblies allows the inner conductor sections 26 to expand in 
length, as shown by the contracted ends 42a and expanded ends 42b within 
the sectioned conductor sleeve 28 in FIG. 3. 
Additionally, the space around the conductor portion 24 within the 
surrounding insulator tube or pipe 12, allows movement at any elbow or 
other directional change of the assembly, as shown within the 90 degree 
insulator elbow 20 of FIG. 3. The two conductor sections 26 to either side 
of the 90 degree conductor elbow 32 are free to flex or bead to 
accommodate thermal expansion, and displace the 90 degree conductor elbow 
32 within the outer insulator elbow 20, as shown by the broken lines 
indicating the displacement of the assembly due to thermal expansion. (It 
will be understood that the effect has been exaggerated in the drawings 
for clarity.) Thermal contraction will of course tend to flex or bend the 
conductor sections 26 in the opposite direction, hence the need to place 
the conductor portion 24 substantially concentrically within the outer 
insulator pipe or tube portion 12, to allow movement in any direction. 
These allowances for the movement of the internal conductor portion 24 not 
only allow for differential thermal expansion and contraction between the 
conductor 24 and insulator 12, but also accommodate the relative 
flexibility of the plastic outer insulator portion 12 relative to the 
metal pipe preferably used for the inner conductor portion 24. 
In summary, the above described electrical power transmission line 10 will 
be seen to provide for an economically and easily assembled transmission 
line which may be readily constructed over relatively rugged and remote 
terrain. The use of readily available copper pipe sections and connectors 
for the internal conductor portion 24 and of readily available polyvinyl 
chloride or other plastic pipe sections and connectors for the outer 
insulator, provides for relatively easy transportation of such components 
to the back country and wilderness areas. 
As such pipe and tube sections are readily available in relatively short 
lengths (e.g., 8, 10, 12 feet, etc.), such materials may be transported 
readily by air in larger single engine aircraft, as are commonly used for 
such back country transport. Float plane transport is viable means of 
transport, assuming the presence of a nearby lake or other body of water 
sufficiently large for takeoffs and landings; such geography is likely in 
the environment of the present invention. The assembly of the present 
electrical transmission line may be readily accomplished by a relatively 
unskilled crew with minimal tools; only appropriately sized pipe and 
tubing cutters and plastic solvent would be required for the construction 
of the present electrical transmission line. As both the inner conduct and 
the outer insulator are devoid of any holes or passages therethrough, the 
internal components are particularly well protected from corrosion or 
other adverse environmental effects. Accordingly, the use of the present 
electrical transmission line could accomplish much in the provision of 
electrical power from remote hydroelectric sites, which were uneconomical 
to develop prior to the present invention 
It is to be understood that the present invention is not limited to the 
sole embodiment described above, but encompasses any and all embodiments 
within the scope of the following claims.