When was the power cable invented?

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The development of electrical wiring has been essential for the transmission of electricity and communication throughout history.. From the earliest discoveries in electricity generation to the latest innovations in cable technology, this article will explore the fascinating history of electrical wiring. From the first signs of static electricity to advances in fiber optic cables and superconductors, each stage has been crucial to our modern world. Accompany us on this journey through the history of the electric cable.

Discovery of Electricity and the First Conducting Cables

ago more than 2.000 years, The Greek philosopher Thales of Miletus discovered that electricity was generated through friction. Nevertheless, It was in the 18th century that significant advances were made in the field of electrical wiring..

In , The Englishman Gray discovered that electricity could be transmitted along metal cables, which led to the concept of &#;conductor&#;. In , The Frenchman Dezaguillier defined the concepts of conductor and insulator. Posteriorly, in , The German Winkler used electrical wires to transmit sparks over long distances, marking the birth of the electric cable.

Discharges generate sparks

In , The American Franklin invented the lightning rod and connected it to the ground using a cable, which represented the first practical application of electricity cable. Finally, in , The Italian Volta invented the battery and managed to obtain direct current, laying the foundation for future advances in electricity transmission.

The emergence of the telegraph and the expansion of telegraph cables

At the beginning of the 19th century, several European and American physicists such as Oersted in Denmark, Faraday in Great Britain, Ohm in Germany and Henry in the United States, discovered and created fundamental theories about electricity and electromagnetism. These discoveries laid the foundation for the future transmission of electricity and information..

In , Gauss and Weber created the first electromagnetic telegraph with a pointer, which was used in a line of 1 km during 6 years. In , Morse invented the cable telegraph in the United States, what prompted the development of communication cables.

After, in , Cook and Wheatstone built the first telegraph line 21 km in London, and in rubber-insulated submarine telegraph cables were laid in New York Harbor. In , Britain laid the first submarine telegraph cable across the English Channel. From that moment, Europe and the United States experienced accelerated development, and in a few decades almost all the main cities of each country had telegraph cables. In , The United Kingdom completed a telegraph network of submarine communications cables that connected the entire British empire.

The Emergence of Electricity in Industry and Home

As the 19th century progressed, Electricity began to play a crucial role in industry and in homes. The invention of the electric motor by Michael Faraday in allowed the use of electricity as a source of energy for industrial machinery.

In the decade of , Thomas Edison and Nikola Tesla carried out key research on direct current and alternating current, respectively. Edison founded the first electric utility company in New York and developed the direct current distribution system, while Tesla proposed the use of alternating current and developed the polyphase system that allowed the transmission of electricity over long distances..

Miscellaneous wires and cables

The invention of the automatic switch in and the development of more efficient electrical generators drove the widespread adoption of electricity in homes and businesses. Electrical distribution networks began to be laid in cities, and the copper cables became the standard for electricity transmission.

Advances in Submarine Cables and Information Transmission

At the end of the 19th century and the beginning of the 20th, There were significant advances in submarine cable technology. Traditional telegraph cables were improved with the incorporation of more efficient insulators, such as gutta percha and rubber, which allowed the transmission of signals over long distances underwater.

In , The first transatlantic telegraph cable was laid connecting Europe with North America, although it had a limited duration. Nevertheless, in , A new transatlantic cable was successfully installed, providing stable and fast telegraphic communication between the two continents..

Cables lying on the seabed

With the advent of telephony at the end of the 19th century, cables began to gradually replace telegraph cables. Advances in cable technology enabled greater voice and data transmission capacity, and extensive networks were established throughout the world.

The Era of Fiber Optic and Superconductors

In the second half of the 20th century, revolutionary advances occurred in electrical cable technology. The invention of fiber optics in the s marked an important milestone in the transmission of information.

The Optical fiber uses glass or plastic threads extremely thin to transmit light signals that carry data through pulses of light. This advancement allowed for faster and more efficient transmission of information compared to conventional metallic cables..

Optical fibers for signal transmission

Besides, in the decade of , Significant advances were made in superconducting research, materials that have almost zero electrical resistance at extremely low temperatures. Superconductors promise lossless electricity transmission and the possibility of creating highly efficient distribution networks.

Although superconducting technology is still in the research and development stages, A future is envisioned in which superconducting cables can radically transform the transmission and distribution of electricity.

conclusions

Along the history, The evolution of cables has played a fundamental role in the advancement of communication and energy transmission. From the underwater cables that connected continents to the electric cables that carried electricity to our homes, These technological advances have transformed society and brought the world closer together into an interconnected network..

With each advancement in cable technology, Higher transmission speeds have been achieved, load capacities and energy transmission efficiency. As technology continues to advance, It's exciting to imagine the future possibilities that could arise with even more innovative and efficient cables..

As a last resort, cables have been the threads that have woven our global society, allowing us to communicate, share information and energy quickly and efficiently. In an increasingly connected world, The importance of electrical wiring as the backbone of our technological and energy infrastructure will continue to be fundamental in the future.

Bundle of wires for transmitting electricity

This article is about electric power conductors. For portable equipment, see power cord

A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Power cables that are bundled inside thermoplastic sheathing and that are intended to be run inside a building are known as NM-B (nonmetallic sheathed building cable).

Flexible power cables are used for portable devices, mobile tools, and machinery.

History

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The first power distribution system developed by Thomas Edison in in New York City used copper rods, wrapped in jute and placed in rigid pipes filled with a bituminous compound.[1] Although vulcanized rubber had been patented by Charles Goodyear in , it was not applied to cable insulation until the s, when it was used for lighting circuits.[2] Rubber-insulated cable was used for 11,000-volt circuits in installed for the Niagara Falls power project.

Mass-impregnated paper-insulated medium voltage cables were commercially practical by . During World War II several varieties of synthetic rubber and polyethylene insulation were applied to cables.[3]

Typical residential and office construction in North America has gone through several technologies:

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Additional reading:
What Factors Influence Your Aluminum Alloy Cable Purchase Decisions?

Construction

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Modern power cables come in a variety of sizes, materials, and types, each particularly adapted to its uses.[8] Large single insulated conductors are also sometimes called power cables in the industry.[9]

Cables consist of three major components: conductors, insulation, protective jacket. The makeup of individual cables varies according to application. The construction and material are determined by three main factors:

• Working voltage, determining the thickness of the insulation;
• Current-carrying capacity, determining the cross-sectional size of the conductor(s);
• Environmental conditions such as temperature, water, chemical or sunlight exposure, and mechanical impact, determining the form and composition of the outer cable jacket.

Cables for direct burial or for exposed installations may also include metal armor in the form of wires spiraled around the cable, or a corrugated tape wrapped around it. The armor may be made of steel or aluminum, and although connected to earth ground is not intended to carry current during normal operation. Electrical power cables are sometimes installed in raceways, including electrical conduit and cable trays, which may contain one or more conductors. When it is intended to be used inside a building, nonmetallic sheathed building cable (NM-B) consists of two or more wire conductors (plus a grounding conductor) enclosed inside a thermoplastic insulation sheath that is heat-resistant. It has advantages over armored building cable because it is lighter, easier to handle, and its sheathing is easier to work with.[10]

Power cables use stranded copper or aluminum conductors, although small power cables may use solid conductors in sizes of up to 1/0. (For a detailed discussion on copper cables, see: Copper wire and cable.). The cable may include uninsulated conductors used for the circuit neutral or for ground (earth) connection. The grounding conductor connects the equipment's enclosure/chassis to ground for protection from electric shock. These uninsulated versions are known are bare conductors or tinned bare conductors. The overall assembly may be round or flat. Non-conducting filler strands may be added to the assembly to maintain its shape. Filler materials can be made in non-hydroscopic versions if required for the application.

Special purpose power cables for overhead applications are often bound to a high strength alloy, ACSR, or alumoweld messenger. This cable is called aerial cable or pre-assembled aerial cable (PAC). PAC can be ordered unjacketed, however, this is less common in recent years due to the low added cost of supplying a polymeric jacket. For vertical applications the cable may include armor wires on top of the jacket, steel or Kevlar. The armor wires are attached to supporting plates periodically to help support the weight of the cable. A supporting plate may be included on each floor of the building, tower, or structure. This cable would be called an armored riser cable. For shorter vertical transitions (perhaps 30&#;150 feet) an unarmored cable can be used in conjunction with basket (Kellum) grips or even specially designed duct plugs.

Material specification for the cable's jacket will often consider resistance to water, oil, sunlight, underground conditions, chemical vapors, impact, fire, or high temperatures. In nuclear industry applications the cable may have special requirements for ionizing radiation resistance. Cable materials for a transit application may be specified not to produce large amounts of smoke if burned (low smoke zero halogen). Cables intended for direct burial must consider damage from backfill or dig-ins. HDPE or polypropylene jackets are common for this use. Cables intended for subway (underground vaults) may consider oil, fire resistance, or low smoke as a priority. Few cables these days still employ an overall lead sheath. However, some utilities may still install paper insulated lead covered cable in distribution circuits. Transmission or submarine cables are more likely to use lead sheaths. However, lead is in decline and few manufacturers exist today to produce such items. When cables must run where exposed to mechanical damage (industrial sites), they may be protected with flexible steel tape or wire armor, which may also be covered by a water-resistant jacket.

A hybrid cable can include conductors for control signals or may also include optical fibers for data.

Higher voltages

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For circuits operating at or above 2,000 volts between conductors, a conductive shield should surround the conductor's insulation. This equalizes electrical stress on the cable insulation. This technique was patented by Martin Hochstadter in ;[2] the shield is sometimes called a Hochstadter shield. Aside from the semi conductive ("semicon") insulation shield, there will also be a conductor shield. The conductor shield may be semi conductive (usually) or non conducting. The purpose of the conductor shield is similar to the insulation shield: it is a void filler and voltage stress equalizer.

To drain off stray voltage, a metallic shield will be placed over the "semicon." This shield is intended to "make safe" the cable by pulling the voltage on the outside of the insulation down to zero (or at least under the OSHA limit of 50 volts). This metallic shield can consist of a thin copper tape, concentric drain wires, flat straps, lead sheath, or other designs. The metallic shields of a cable are connected to earth ground at the ends of the cable, and possibly locations along the length if voltage rise during faults would be dangerous. Multi-point grounding is the most common way to ground the cable's shield. Some special applications require shield breaks to limit circulating currents during the normal operations of the circuit. Circuits with shield breaks could be single or multi point grounded. Special engineering situations may require cross bonding.

Liquid or gas filled cables are still employed in distribution and transmission systems today. Cables of 10 kV or higher may be insulated with oil and paper, and are run in a rigid steel pipe, semi-rigid aluminum or lead sheath. For higher voltages the oil may be kept under pressure to prevent formation of voids that would allow partial discharges within the cable insulation.

A high-voltage cable designed for 400 kV. The large conductor in the center carries the current, smaller conductors on the outside act as a shield to equalize the voltage stress in the thick polyethylene insulation layer.

Liquid filled cables are known for extremely long service lives with little to no outages. Unfortunately, oil leaks into soil and bodies of water are of grave concern and maintaining a fleet of the needed pumping stations is a drain on the O+M budget of most power utilities. Pipe type cables are often converted to solid insulation circuit at the end of their service life despite a shorter expected service life.

Modern high-voltage cables use polyethylene or other polymers, including XLPE for insulation. They require special techniques for jointing and terminating, see High-voltage cable.

Flexibility of cables (stranding class)

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All electrical cables are somewhat flexible, allowing them to be shipped to installation sites wound on reels, drums or hand coils. Flexibility is an important factor in determining the appropriate stranding class of the cable as it directly affects the minimum bending radius. Power cables are generally stranding class A, B, or C. These classes allow for the cable to be trained into a final installed position where the cable will generally not be disturbed. Class A, B, and C offer more durability, especially when pulling cable, and are generally cheaper. Power utilities generally order Class B stranded wire for primary and secondary voltage applications. At times, a solid conductor medium voltage cable can be used when flexibility is not a concern but low cost and water blocking are prioritized.

Applications requiring a cable to be moved repeatedly, such as for portable equipment, more flexible cables called "cords" or "flex" are used (stranding class G-M). Flexible cords contain fine stranded conductors, rope lay or bunch stranded. They feature overall jackets with appropriate amounts of filler materials to improve their flexibility, trainability, and durability. Heavy duty flexible power cords such as those feeding a mine face cutting machine are carefully engineered &#; their life is measured in weeks. Very flexible power cables are used in automated machinery, robotics, and machine tools. See power cord and extension cable for further description of flexible power cables. Other types of flexible cable include twisted pair, extensible, coaxial, shielded, and communication cable.

An X-ray cable is a special type of flexible high-voltage cable.

See also

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References

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