ACHIEVER'S CHOICE

Pharmacy (from the Greek φάρμακον 'pharmakos' = drug) is the health profession that links the health sciences with the chemical sciences, and it is charged with ensuring the safe and effective use of medication. The scope of pharmacy practice includes more traditional roles such as compounding and dispensing medications, and it also includes more modern services related to patient care, including clinical services, reviewing medications for safety and efficacy, and providing drug information. Pharmacists, therefore, are the experts on drug therapy and are the primary health professionals who optimize medication use to provide patients with positive health outcomes. The term is also applied to an establishment used for such purposes.

Disciplines

Pharmacy, tacuinum sanitatis casanatensis (XIV century)

The field of Pharmacy can generally be divided into three primary disciplines:

• Pharmaceutics
• Medicinal chemistry and Pharmacognosy
• Pharmacy practice

The boundaries between these disciplines and with other sciences, such as biochemistry, are not always clear-cut; and often, collaborative teams from various disciplines research together.

Pharmacology is sometimes considered a fourth discipline of pharmacy. Although pharmacology is essential to the study of pharmacy, it is not specific to pharmacy. Therefore it is usually considered to be a field of the broader sciences.

There are various specialties of pharmacy practice. Specialization in pharmacy practice is typically based on the place of practice or practice roles including: community, hospital, consultant, locum, drug information, regulatory affairs, industry, and academia.

Other specializations in pharmacy practice recognized by the Board of Pharmaceutical Specialties include: cardiovascular, infectious disease, oncology, pharmacotherapy, nuclear, nutrition, and psychiatry.^[1] The Commission for Certification in Geriatric Pharmacy certifies pharmacists in geriatric pharmacy practice. The American Board of Applied Toxicology certifies pharmacists and other medical professionals in applied toxicology.

Pharmacists

Main article: Pharmacist

Pharmacists are highly-trained and skilled healthcare professionals who perform various roles to ensure optimal health outcomes for their patients. Many pharmacists are also small-business owners, owning the pharmacy in which they practice.

Pharmacists are represented internationally by the International Pharmaceutical Federation (FIP). They are represented at the national level by professional organisations such as the Royal Pharmaceutical Society of Great Britain (RPSGB), the Pharmacy Guild of Australia (PGA), the Pakistan Pharmacists Society(PPS) and the American Pharmacists Association (APhA). See also: List of pharmacy associations.

In some cases, the representative body is also the registering body, which is responsible for the ethics of the profession. Since the Shipman Inquiry, there has been a move in the UK to separate the two roles.

History of pharmacy

Muslim pharmacy

In the field of pharmacy, the first drugstores were opened by Muslim pharmacists in Baghdad in 754,^[2] while the first apothecary shops were also founded by Muslim practitioners.^[3]

The advances made in the Middle East by Muslim chemists in botany and chemistry led Muslim physicians to substantially develop pharmacology. Muhammad ibn Zakarīya Rāzi (Rhazes) (865-915), for instance, acted to promote the medical uses of chemical compounds. Abu al-Qasim al-Zahrawi (Abulcasis) (936-1013) pioneered the preparation of medicines by sublimation and distillation. His Liber servitoris is of particular interest, as it provides the reader with recipes and explains how to prepare the `simples’ from which were compounded the complex drugs then generally used. Sabur Ibn Sahl (d 869), was, however, the first physician to initiate pharmacopoedia, describing a large variety of drugs and remedies for ailments. Al-Biruni (973-1050) wrote one of the most valuable Islamic works on pharmacology entitled Kitab al-Saydalah (The Book of Drugs), where he gave detailed knowledge of the properties of drugs and outlined the role of pharmacy and the functions and duties of the pharmacist. Ibn Sina (Avicenna), too, described no less than 700 preparations, their properties, mode of action and their indications. He devoted in fact a whole volume to simple drugs in The Canon of Medicine. Of great impact were also the works by al-Maridini of Baghdad and Cairo, and Ibn al-Wafid (1008-1074), both of which were printed in Latin more than fifty times, appearing as De Medicinis universalibus et particularibus by `Mesue' the younger, and the Medicamentis simplicibus by `Abenguefit'. Peter of Abano (1250-1316) translated and added a supplement to the work of al-Maridini under the title De Veneris. Al-Muwaffaq’s contributions in the field are also pioneering. Living in the 10th century, he wrote The foundations of the true properties of Remedies, amongst others describing arsenious oxide, and being acquainted with silicic acid. He made clear distinction between sodium carbonate and potassium carbonate, and drew attention to the poisonous nature of copper compounds, especially copper vitriol, and also lead compounds. For the story, he also mentions the distillation of sea-water for drinking.^[4]

Chinese Pharmacy

Main article: Pharmacy in China

The beginnings of pharmacy in China are ancient. It stemmed from Chinese alchemy. Shennong is said to have tasted hundreds of herbs to test their medical value. The most well-known work attributed to Shennong is The Divine Farmer's Herb-Root Classic. This work is considered to be the earliest Chinese pharmacopoeia. It includes 365 medicines derived from minerals, plants, and animals. Shennong is credited with identifying hundreds of medical (and poisonous) herbs by personally testing their properties, which was crucial to the development of Traditional Chinese medicine.

Japanese pharmacy

In ancient Japan, the men who fulfilled roles similar to those of modern pharamacists were highly respected. The place of pharmacists in society was expressly defined in the Taihō Code (701) and re-stated in the Yōrō Code (718). Ranked positions in the pre-Heian Imperial court were established; and this organizational structure remained largely intact until the Meiji Restoration (1868). In this highly stable hierarchy, the pharmacists -- and even pharmacist assistants -- were assigned status superior to all others in health-related fields such as physicians and acupuncturists. In the Imperial household, the pharmacist was even ranked above the two personal physicians of the Emperor.^[5]

Types of pharmacy practice areas

Pharmacists practice in a variety of areas including retail, hospitals, clinics, nursing homes, drug industry, and regulatory agencies. Pharmacists can specialize in various areas of practice including but not limited to: hematology/oncology, infectious diseases, ambulatory care, nutrition support, drug information, critical care, pediatrics, etc.

Community pharmacy

19th century Italian pharmacy

Modern pharmacy in Norway

A pharmacy (commonly the chemist in Australia, New Zealand and the UK; or drugstore in North America; retail pharmacy in industry terminology; or Apothecary, historically) is the place where most pharmacists practice the profession of pharmacy. It is the community pharmacy where the dichotomy of the profession exists—health professionals who are also retailers.

Community pharmacies usually consist of a retail storefront with a dispensary where medications are stored and dispensed. The dispensary is subject to pharmacy legislation; with requirements for storage conditions, compulsory texts, equipment, etc., specified in legislation. Where it was once the case that pharmacists stayed within the dispensary compounding/dispensing medications; there has been an increasing trend towards the use of trained pharmacy technicians while the pharmacist spends more time communicating with patients.

All pharmacies are required to have a pharmacist on-duty at all times when open. In many jurisdictions, it is also a requirement that the owner of a pharmacy must be a registered pharmacist (R.Ph.). This latter requirement has been revoked in many jurisdictions, such that many retailers (including supermarkets and mass merchandisers) now include a pharmacy as a department of their store.

Likewise, many pharmacies are now rather grocery store-like in their design. In addition to medicines and prescriptions, many now sell a diverse arrangement of additional household items such as cosmetics, shampoo, bandages, office supplies, confectionary, and snack foods.

Hospital pharmacy

Main article: Hospital pharmacy

Pharmacies within hospitals differ considerably from community pharmacies. Some pharmacists in hospital pharmacies may have more complex clinical medication management issues whereas pharmacists in community pharmacies often have more complex business and customer relations issues.

Because of the complexity of medications including specific indications, effectiveness of treatment regimens, safety of medications (i.e., drug interactions) and patient compliance issues ( in the hospital and at home) many pharmacists practicing in hospitals gain more education and training after pharmacy school through a pharmacy practice residency and sometimes followed by another residency in a specific area. Those pharmacists are often referred to as clinical pharmacists and they often specialize in various disciplines of pharmacy. For example, there are pharmacists who specialize in haematology/oncology, HIV/AIDS, infectious disease, critical care, emergency medicine, toxicology, nuclear pharmacy, pain management, psychiatry, anticoagulation clinics, herbal medicine, neurology/epilepsy management, paediatrics, neonatal pharmacists and more.

Hospital pharmacies can usually be found within the premises of the hospital. Hospital pharmacies usually stock a larger range of medications, including more specialized medications, than would be feasible in the community setting. Most hospital medications are unit-dose, or a single dose of medicine. Hospital pharmacists and trained pharmacy technicians compound sterile products for patients including total parenteral nutrition (TPN), and other medications given intravenously. This is a complex process that requires adequate training of personnel, quality assurance of products, and adequate facilities. Several hospital pharmacies have decided to outsource high risk preparations and some other compounding functions to companies who specialize in compounding.

Clinical pharmacy

Main article: Clinical pharmacy

Clinical pharmacists provide direct patient care services that optimizes the use of medication and promotes health, wellness, and disease prevention.^[6] Clinical pharmacists care for patients in all health care settings but the clinical pharmacy movement initially began inside Hospitals and clinics. Clinical pharmacists often collaborate with Physicians and other healthcare professionals. Clinical pharmacists are now an integral part of the interdisciplinary approach to patient care. They work collaboratively with physicians, nurses and other healthcare personnel in various medical and surgical areas.

Compounding pharmacy

Main article: Compounding

Compounding is the practice of preparing drugs in new forms. For example, if a drug manufacturer only provides a drug as a tablet, a compounding pharmacist might make a medicated lollipop that contains the drug. Patients who have difficulty swallowing the tablet may prefer to suck the medicated lollipop instead.

Compounding pharmacies specialize in compounding, although many also dispense the same non-compounded drugs that patients can obtain from community pharmacies.

Consultant pharmacy

Main article: Consultant pharmacist

Consultant pharmacy practice focuses more on medication regimen review (i.e. "cognitive services") than on actual dispensing of drugs. Consultant pharmacists most typically work in nursing homes, but are increasingly branching into other institutions and non-institutional settings.^[7] Traditionally consultant pharmacists were usually independent business owners, though in the United States many now work for several large pharmacy management companies (primarily Omnicare, Kindred Healthcare and PharMerica). This trend may be gradually reversing as consultant pharmacists begin to work directly with patients, primarily because many elderly people are now taking numerous medications but continue to live outside of institutional settings. Some community pharmacies employ consultant pharmacists and/or provide consulting services.

Internet pharmacy

Main article: Online pharmacy

Since about the year 2000, a growing number of Internet pharmacies have been established worldwide. Many of these pharmacies are similar to community pharmacies, and in fact, many of them are actually operated by brick-and-mortar community pharmacies that serve consumers online and those that walk in their door. The primary difference is the method by which the medications are requested and received. Some customers consider this to be more convenient and private method rather than traveling to a community drugstore where another customer might overhear about the drugs that they take. Internet pharmacies (also known as Online Pharmacies) are also recommended to some patients by their physicians if they are homebound.

While most Internet pharmacies sell prescription drugs and require a valid prescription, some Internet pharmacies sell prescription drugs without requiring a prescription. Many customers order drugs from such pharmacies to avoid the "inconvenience" of visiting a doctor or to obtain medications which their doctors were unwilling to prescribe. However, this practice has been criticized as potentially dangerous, especially by those who feel that only doctors can reliably assess contraindications, risk/benefit ratios, and an individual's overall suitability for use of a medication. There also have been reports of such pharmacies dispensing substandard products. Of course as history has shown, substandard products can be dispensed by both Internet and Community pharmacies, so it is best that the buyer beware.

Of particular concern with internet pharmacies is the ease with which people, youth in particular, can obtain controlled substances (e.g., Vicodin, generically known as hydrocodone) via the internet without a prescription issued by a doctor/practioner who has an established doctor-patient relationship. There are many instances where a practioner issues a prescription, brokered by an internet server, for a controlled substance to a "patient" s/he has never met. In the United States, in order for a prescription for a controlled substance to be valid, it must be issued for a legitimate medical purpose by a licensed practitioner acting in the course of legitimate doctor-patient relationship. The filling pharmacy has a corresponding responsibility to ensure that the prescription is valid. Often, individual state laws outline what defines a valid patient-doctor relationship.

Canada is home to dozens of licensed Internet pharmacies, many which sell their lower-cost prescription drugs to U.S. consumers, who pay the world's highest drug prices.^{[citation needed]} However, there are Internet pharmacies in many other countries including India, Israel, and the UK that serve customers worldwide.

In the United States, there has been a push to legalize importation of medications from Canada and other countries, in order to reduce consumer costs. While in most cases importation of prescription medications violates Food and Drug Administration (FDA) regulations and federal laws, enforcement is generally targeted at international drug suppliers, rather than consumers. There is no known case of any U.S. citizens buying Canadian drugs for personal use with a prescription, who has ever been charged by authorities.

Veterinary pharmacy

Veterinary pharmacies, sometimes called animal pharmacies may fall in the category of hospital pharmacy, retail pharmacy or mail-order pharmacy. Veterinary pharmacies stock different varieties and different strengths of medications to fullfill the pharmaceutical needs of animals. Because the needs of animals as well as the regulations on veterinary medicine are often very different from those related to people, veterinary pharmacy is often kept separate from regular pharmacies.

Nuclear pharmacy

Main article: Nuclear pharmacy

Nuclear pharmacy focuses on preparing radioactive materials for diagnostic tests and for treating certain diseases. Nuclear pharmacists undergo additional training specific to handling radioactive materials, and unlike in community and hospital pharmacies, nuclear pharmacists typically do not interact directly with patients.

Military pharmacy

Main article: Military pharmacy

Military pharmacy is an entirely different working environment due to the fact that technicians perform most duties that in a civilian sector would be illegal. State laws of Technician patient counseling and medication checking by a pharmacist do not apply.

Pharmacy informatics

Main article: Pharmacy informatics

Pharmacy informatics is the combination of pharmacy practice science and applied information science. Pharmacy informaticsts work in many practice areas of pharmacy, however, they may also work in information technology departments or for healthcare information technology vendor companies. As a practice area and specialist domain, pharmacy informatics is growing quickly to meet the needs of major national and international patient information projects and health system interoperability goals. Pharmacists are well trained to participate in medication management system development, deployment and optimization.

Issues in pharmacy

Separation of prescribing from dispensing

In most jurisdictions (such as the United States), pharmacists are regulated separately from physicians. Specifically, the legislation stipulates that the practice of prescribing must be separate from the practice of dispensing.^{[citation needed]} These jurisdictions also usually specify that only pharmacists may supply scheduled pharmaceuticals to the public, and that pharmacists cannot form business partnerships with physicians or give them "kickback" payments. However, the American Medical Association (AMA) Code of Ethics provides that physicians may dispense drugs within their office practices as long as there is no patient exploitation and patients have the right to a written prescription that can be filled elsewhere. 7 to 10 percent of American physician practices reportedly dispense drugs on their own.^[8]

In other jurisdictions (particularly in Asian countries such as China, Hong Kong, Malaysia, and Singapore), doctors are allowed to dispense drugs themselves and the practice of pharmacy is sometimes integrated with that of the physician, particularly in traditional Chinese medicine.

In Canada it is common for a medical clinic and a pharmacy to be located together and for the ownership in both enterprises to be common, but licensed separately.

The reason for the majority rule is the high risk of a conflict of interest. Otherwise, the physician has a financial self-interest in "diagnosing" as many conditions as possible, and in exaggerating their seriousness, because he or she can then sell more medications to the patient. Such self-interest directly conflicts with the patient's interest in obtaining cost-effective medication and avoiding the unnecessary use of medication that may have side-effects. This system reflects much similarity to the checks and balances system of the U.S. and many other governments.

A campaign for separation has begun in many countries and has already been successful (like in Korea). As many of the remaining nations move towards separation, resistance and lobbying from dispensing doctors who have pecuniary interests may prove a major stumbling block (e.g. in Malaysia).

The future of pharmacy

In the coming decades, pharmacists are expected to become more integral within the health care system. Rather than simply dispensing medication, pharmacists will be paid for their patient care skills.^[9]

This shift has already commenced in some countries; for instance, pharmacists in Australia receive remuneration from the Australian Government for conducting comprehensive Home Medicines Reviews. In the United Kingdom, pharmacists (and nurses) who undertake additional training are obtaining prescribing rights. They are also being paid for by the government for medicine use reviews. In the United States, pharmaceutical care or Clinical pharmacy has had an evolving influence on the practice of pharmacy.^[10] Moreover, the Doctor of Pharmacy (Pharm.D.) degree is now required before entering practice and many pharmacists now complete one or two years of residency or fellowship training following graduation. In addition, consultant pharmacists, who traditionally operated primarily in nursing homes are now expanding into direct consultation with patients, under the banner of "senior care pharmacy."^[11]

See also

Pharmacy and Pharmacology Portal

• Apothecary
• Bachelor of Pharmacy, Master of Pharmacy, Doctor of Pharmacy
• Clinical pharmacy
• Consultant pharmacist
• Doctor of Pharmacy
• Evidence-based pharmacy in developing countries
• Hospital pharmacy
• List of pharmacies
• List of pharmacy associations
• List of pharmacy organizations in the United Kingdom
• List of pharmacy schools
• Nuclear pharmacy
• Online pharmacy
• Pharmaceutical company
• Pharmacogenetics
• Pharmacogenomics
• Pharmacognosy
• Pharmaconomist
• Pharmacy informatics
• Raeapteek (one of the oldest continuously run pharmacies in Europe dating from the 15th century)
• American Society for Pharmacy Law
• pharmacology

Symbols

The two symbols most commonly associated with pharmacy are the mortar and pestle and the ℞ (recipere) character, which is often written as "rx" in typed text. The show globe was also used in English speaking countries until the early 20th century. Pharmacy organizations often use other symbols, such as the Bowl of Hygieia, conical measures, and caduceuses in their logos. Other symbols are common in different countries: the green Greek cross in France, the United Kingdom, Belgium, and Spain, the increasingly-rare Gaper in The Netherlands, and a red stylized letter A in Germany and Austria (from Apotheke, the German word for pharmacy, from the same Greek root as the English word 'apothecary').

Bowl of Hygeia	The green Greek Cross used in Argentina, France and the United Kingdom	Mortar and pestle	Recipe symbol
The red stylized "A" used in Germany and Austria	Caduceus	Rod of Asclepius	Hanging Show Globe

References

• (Japanese) Asai,T. (1985). Nyokan Tūkai. Tokyo: Kōdan-Sha.
• (French) Titsingh, Isaac, ed. (1834). [Siyun-sai Rin-siyo/Hayashi Gahō, 1652], Nipon o daï itsi ran; ou, Annales des empereurs du Japon, tr. par M. Isaac Titsingh avec l'aide de plusieurs interprètes attachés au comptoir hollandais de Nangasaki; ouvrage re., complété et cor. sur l'original japonais-chinois, accompagné de notes et précédé d'un Aperçu d'histoire mythologique du Japon, par M. J. Klaproth. Paris: Oriental Translation Fund of Great Britain and Ireland....Click link for digitized, full-text copy of this book (in French)

External links

Wikimedia Commons has media related to:

Pharmacy

Look up Pharmacy in
Wiktionary, the free dictionary.

• Navigator History of Pharmacy Collection of internet resources related to the history of pharmacy.
• RPSGB Museum Information Sheets Illustrated information sheets on objects in the history of pharmacy.
• History of Pharmacy Web Pages Perbo's History of Pharmacy Web Pages.
• Soderlund Pharmacy Museum - Information about the history of the American Drugstore
• The Lloyd Library Library of botanical, medical, pharmaceutical, and scientific books and periodicals, and works of allied sciences
• American Institute of the History of Pharmacy American Institute of the History of Pharmacy--resources in the history of pharmacy

Other

• Pharmaclips - Medicine Information Gateway with Drug Finder and printable coupons.
• PharmWeb - Pharmaceutical Information Online.
• The Virtual Library of Pharmacy - Extensive index of pharmacy-related resources, including information on careers in pharmacy, pharmacy schools, pharmaceuticaul companies, associations and conferences.
• Pharmacist's Letter - Unbiased, research based resource for pharmacists and pharmacy technicians on new developments in drug therapy

Electric power transmission

A process in the delivery of electricity to consumers, is the bulk transfer of electrical power. Typically, power transmission is between the power plant and a substation near a populated area. Electricity distribution is the delivery from the substation to the consumers. Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers, and may allow exploitation of low-grade fuel resources that would otherwise be too costly to transport to generating facilities.

Due to the large amount of power involved, transmission normally takes place at high voltage (110 kV or above). Electricity is usually transmitted over long distance through overhead power transmission lines. Underground power transmission is used only in densely populated areas due to its high cost of installation and maintenance, and because the high reactive power produces large charging currents and difficulties in voltage management.

A power transmission system is sometimes referred to colloquially as a "grid"; however, for reasons of economy, the network is not a mathematical grid. Redundant paths and lines are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power. Much analysis is done by transmission companies to determine the maximum reliable capacity of each line, which, due to system stability considerations, may be less than the physical or thermal limit of the line. Deregulation of electricity companies in many countries has led to renewed interest in reliable economic design of transmission networks. However, in some places the gaming of a deregulated energy system has led to disaster, such as that which occurred during the California electricity crisis of 2000 and 2001.^{[citation needed]}

AC power transmission

AC power transmission is the transmission of electric power by alternating current. Usually transmission lines use three phase AC current. Single phase AC current is sometimes used in a railway electrification system. In urban areas, trains may be powered by DC at 600 volts or so.

Overhead conductors are not covered by insulation. The conductor material is nearly always an aluminum alloy, made into several strands and possibly reinforced with steel strands. Conductors are a commodity supplied by several companies worldwide. Improved conductor material and shapes are regularly used to allow increased capacity and modernize transmission circuits. Conductor sizes in overhead transmission work range in size from #6 American wire gauge (about 12 square millimetres) to 1,590,000 circular mils area (about 750 square millimetres), with varying resistance and current-carrying capacity. Thicker wires would lead to a relatively small increase in capacity due to the skin effect, that causes most of the current to flow close to the surface of the wire.

Today, transmission-level voltages are usually considered to be 110 kV and above. Lower voltages such as 66 kV and 33 kV are usually considered sub-transmission voltages but are occasionally used on long lines with light loads. Voltages less than 33 kV are usually used for distribution. Voltages above 230 kV are considered extra high voltage and require different designs compared to equipment used at lower voltages.

Overhead transmission lines are uninsulated wire, so design of these lines requires minimum clearances to be observed to maintain safety.

History

In the early days of commercial use of electric power, transmission of electric power at the same voltage as used by lighting and mechanical loads restricted the distance between generating plant and consumers. Originally generation was with direct current, which could not easily be increased in voltage for long-distance transmission. Different classes of loads, for example, lighting, fixed motors, and traction (railway) systems, required different voltages and so used different generators and circuits. ^[1]

At an AIEE meeting on May 16, 1888, Nikola Tesla delivered a lecture entitled A New System of Alternating Current Motors and Transformers, describing the equipment which allowed efficient generation and use of alternating currents. Tesla's disclosures, in the form of patents, lectures and technical articles, are useful for understanding the history of the modern system of power transmission. Ownership of the rights to the Tesla patents was a key commercial advantage to the Westinghouse Company in offering a complete alternating current power system for both lighting and power.

The so-called "universal system" used transformers both to couple generators to high-voltage transmission lines, and to connect transmission to local distribution circuits. By a suitable choice of utility frequency, both lighting and motor loads could be served. Rotary converters and later mercury-arc valves and other rectifier equipment allowed DC load to be served by local conversion where needed. Even generating stations and loads using different frequencies could also be interconnected using rotary converters. By using common generating plants for every type of load, important economies of scale were achieved, lower overall capital investment was required, load factor on each plant was increased allowing for higher efficiency, allowing for a lower cost of energy to the consumer and increased overall use of electric power.

By allowing multiple generating plants to be interconnected over a wide area, electricity production cost was reduced. The most efficient available plants could be used to supply the varying loads during the day. Reliability was improved and capital investment cost was reduced, since stand-by generating capacity could be shared over many more customers and a wider geographic area. Remote and low-cost sources of energy, such as hydroelectric power or mine-mouth coal, could be exploited to lower energy production cost. ^[2]

The first transmission of three-phase alternating current using high voltage took place in 1891 during the international electricity exhibition in Frankfurt. A 25 kV transmission line, approximately 175 kilometers long, connected Lauffen on the Neckar and Frankfurt.

Initially transmission lines were supported by porcelain pin-and-sleeve insulators similar to those used for telegraphs and telephone lines. However, these had a practical limit of 40 kV. In 1907, the invention of the disc insulator by Harold W. Buck of the Niagara Falls Power Corporation and Edward M. Hewlett of General Electric allowed practical insulators of any length to be constructed for higher voltages. The first large scale hydroelectric generators in the USA were installed at Niagara Falls and provided electricity to Buffalo, New York via power transmission lines. A statue of Tesla stands at Niagara Falls today in tribute to his contributions.

Voltages used for electric power transmission increased throughout the 20th century. By 1914 fifty-five transmission systems operating at more than 70,000 V were in service, the highest voltage then used was 150,000 volts. ^[3] The first three-phase alternating current power transmission at 110 kV took place in 1912 between Lauchhammer and Riesa, Germany. On April 17, 1929 the first 220 kV line in Germany was completed, running from Brauweiler near Cologne, over Kelsterbach near Frankfurt, Rheinau near Mannheim, Ludwigsburg-Hoheneck near Austria. The masts of this line were designed for eventual upgrade to 380 kV. However the first transmission at 380 kV in Germany was on October 5, 1957 between the substations in Rommerskirchen and Ludwigsburg-Hoheneck. In 1967 the first extra-high-voltage transmission at 735 kV took place on a Hydro-Québec transmission line. In 1982 the first transmission at 1200 kV was in the Soviet Union.

The rapid industrialization in the 20th century made electrical transmission lines and grids a critical part of the economic infrastructure in most industrialized nations. Interconnection of local generation plants and small distribution networks was greatly spurred by the requirements of World War I, where large electrical generating plants were built by governments to provide power to munitions factories; later these plants were connected to supply civil load through long-distance transmission. ^[4]

Small municipal electrical utilities did not necessarily desire to reduce the cost of each unit of electricity sold; to some extent, especially during the period 1880-1890, electrical lighting was considered a luxury product and electric power was not substituted for steam power. Engineers such as Samuel Insull in the United States and Sebastian Z. De Ferranti in the United Kingdom were instrumental in overcoming technical, economic, regulatory and political difficulties in development of long-distance electric power transmission. By introduction of electric power transmission networks, in the city of London the cost of a kilowatthour was reduced to one-third in a ten-year period. ^[5]

In 1926 electrical networks in the United Kingdom began to be interconnected in the National Grid, initially operating at 132,000 volts.

Bulk power transmission

Engineers design transmission networks to transport the energy as efficiently as feasible, while at the same time taking into account economic factors, network safety and redundancy. These networks use components such as power lines, cables, circuit breakers, switches and transformers.

A transmission substation decreases the voltage of electricity coming in allowing it to connect from long distance, high voltage transmission, to local, lower voltage, distribution. It also reroutes power to other transmission lines that serve local markets. The substation may also "reboost" power allowing it to travel greater distances from the power generation source along the high voltage transmission lines.This is the PacifiCorp Hale Substation, Orem, Utah.

Transmission efficiency is improved by increasing the voltage using a step-up transformer, which reduces the current in the conductors, while keeping the power transmitted nearly equal to the power input. The reduced current flowing through the conductor reduces the losses in the conductor and since, according to Joule's Law, the losses are proportional to the square of the current, halving the current makes the transmission loss one quarter the original value.

A transmission grid is a network of power stations, transmission circuits, and substations. Energy is usually transmitted within the grid with three-phase AC. DC systems require relatively costly conversion equipment which may be economically justified for particular projects. Single phase AC is used only for distribution to end users since it is not usable for large polyphase induction motors. In the 19th century two-phase transmission was used, but required either three wires with unequal currents or four wires. Higher order phase systems require more than three wires, but deliver marginal benefits.

The capital cost of electric power stations is so high, and electric demand is so variable, that it is often cheaper to import some portion of the variable load than to generate it locally. Because nearby loads are often correlated (hot weather in the Southwest portion of the United States might cause many people there to turn on their air conditioners), imported electricity must often come from far away. Because of the economics of load balancing, transmission grids now span across countries and even large portions of continents. The web of interconnections between power producers and consumers ensures that power can flow even if a few links are inoperative.

The unvarying (or slowly varying over many hours) portion of the electric demand is known as the "base load", and is generally served best by large facilities (and therefore efficient due to economies of scale) with low variable costs for fuel and operations, i.e. nuclear, coal, hydro. Renewables such as solar, wind, ocean/tidal, etc. are not considered "base load" but can still add power to the grid. Smaller- and higher-cost sources such as combined cycle or combustion turbine plants that run on natural gas are then added as needed.

Long-distance transmission of electricity (thousands of miles) is cheap and efficient, with costs of US$ 0.005 to 0.02 per kilowatt-hour (compared to annual averaged large producer costs of US$ 0.01 to US$ 0.025 per kilowatt-hour, retail rates upwards of US$ 0.10 per kilowatt-hour, and multiples of retail for instantaneous suppliers at unpredicted highest demand moments).^[6] Thus distant suppliers can be cheaper than local sources (e.g. New York City buys a lot of electricity from Canada). Multiple local sources (even if more expensive and infrequently used) can make the transmission grid more fault tolerant to weather and other disasters that can disconnect distant suppliers.

Long distance transmission allows remote renewable energy resources to be used to displace fossil fuel consumption. Hydro and wind sources can't be moved closer to high population cities, and solar costs are lowest in remote areas where local power needs are the least. Connection costs alone can determine whether any particular renewable alternative is economically sensible. Costs can be prohibitive for transmission lines.

Grid input

At the generating plants the energy is produced at a relatively low voltage of up to 30 kV (Grigsby, 2001, p. 4-4), then stepped up by the power station transformer to a higher voltage (115 kV to 765 kV AC, ± 250-500 kV DC, varying by country) for transmission over long distances to grid exit points (substations).

Power lines near Birmingham, Alabama

Losses

Transmitting electricity at high voltage reduces the fraction of energy lost to Joule heating. For a given amount of power, a higher voltage reduces the current and thus the resistive losses in the conductor. For example, raising the voltage by a factor of 10 reduces the current by a corresponding factor of 10 and therefore the losses by a factor of 100, provided the same sized conductors are used in both cases. Even if the conductor size is reduced x10 to match the lower current the losses are still reduced x10. Long distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. However, at extremely high voltages, more than 2,000 kV between conductor and ground, corona discharge losses are so large that they can offset the lower resistance loss in the line conductors.

Transmission and distribution losses in the USA were estimated at 7.2% in 1995 [2], and in the UK at 7.4% in 1998. [3]

As of 1980, the longest cost-effective distance for electricity was 4,000 miles (7,000 km), although all present transmission lines are considerably shorter. (see Present Limits of High-Voltage Transmission)

In an alternating current transmission line, the inductance and capacitance of the line conductors can be significant. The currents that flow in these components of transmission line impedance constitute reactive power, which transmits no energy to the load. Reactive current flow causes extra losses in the transmission circuit. The ratio of real power (transmitted to the load) to apparent power is the power factor. As reactive current increases, the reactive power increases and the power factor decreases. For systems with low power factors, losses are higher than for systems with high power factors. Utilities add capacitor banks and other components throughout the system — such as phase-shifting transformers, static VAR compensators, and flexible AC transmission systems (FACTS) — to control reactive power flow for reduction of losses and stabilization of system voltage.

Electrical power is always partially lost by transmission. This applies to short distances such as between components on a printed circuit board as well as to cross country high voltage lines. The major component of power loss is due to ohmic losses in the conductors and is equal to the product of the square of the current and the resistance of the wire:

For a system which delivers a power, P, at unity power factor at a particular voltage, V, the current flowing through the cables is given by . Thus, the power lost in the lines,

Therefore, the power lost is proportional to the resistance and inversely proportional to the square of the voltage. A higher transmission voltage reduces the current and thus the power lost during transmission.

In addition, a low resistance is desirable in the cable. While copper cable could be used, aluminium alloy is preferred due to its much better conductivity to weight ratio making it lighter to support, as well as its lower cost. The aluminium is normally mechanically supported on a steel core.

HVDC

Main article: High-voltage direct current

High voltage direct current (HVDC) is used to transmit large amounts of power over long distances or for interconnections between asynchronous grids. When electrical energy is required to be transmitted over very long distances, it can be more economical to transmit using direct current instead of alternating current. For a long transmission line, the value of the smaller losses, and reduced construction cost of a DC line, can offset the additional cost of converter stations at each end of the line. Also, at high AC voltages significant (although economically acceptable) amounts of energy are lost due to corona discharge, the capacitance between phases or, in the case of buried cables, between phases and the soil or water in which the cable is buried.

HVDC links are sometimes used to stabilize against control problems with the AC electricity flow. In other words, to transmit AC power as AC when needed in either direction between Seattle and Boston would require the (highly challenging) continuous real-time adjustment of the relative phase of the two electrical grids. With HVDC instead the interconnection would: (1) Convert AC in Seattle into HVDC. (2) Use HVDC for the three thousand miles of cross country transmission. Then (3) convert the HVDC to locally synchronized AC in Boston, and optionally in other cooperating cities along the transmission route. One prominent example of such a transmission line is the Pacific DC Intertie located in the Western United States.

Grid exit

At the substations, transformers are again used to step the voltage down to a lower voltage for distribution to commercial and residential users. This distribution is accomplished with a combination of sub-transmission (33 kV to 115 kV, varying by country and customer requirements) and distribution (3.3 to 25 kV). Finally, at the point of use, the energy is transformed to low voltage (100 to 600 V, varying by country and customer requirements).

Limitations

The amount of power that can be sent over a transmission line is limited. The origins of the limits vary depending on the length of the line. For a short line, the heating of conductors due to line losses sets a "thermal" limit. If too much current is drawn, conductors may sag too close to the ground, or conductors and equipment may be damaged by overheating. For intermediate-length lines on the order of 100 km (60 miles), the limit is set by the voltage drop in the line. For longer AC lines, system stability sets the limit to the power that can be transferred. Approximately, the power flowing over an AC line is proportional to the sine of the phase angle between the receiving and transmitting ends. Since this angle varies depending on system loading and generation, it is undesirable for the angle to approach 90 degrees. Very approximately, the allowable product of line length and maximum load is proportional to the square of the system voltage. Series capacitors or phase-shifting transformers are used on long lines to improve stability. High-voltage direct current lines are restricted only by thermal and voltage drop limits, since the phase angle is not material to their operation.

Communications

Operators of long transmission lines require reliable communications for control of the power grid and, often, associated generation and distribution facilities. Fault-sensing protection relays at each end of the line must communicate to monitor the flow of power into and out of the protected line section so that faulted conductors or equipment can be quickly de-energized and the balance of the system restored. Protection of the transmission line from short circuits and other faults is usually so critical that common carrier telecommunications are insufficiently reliable. In remote areas a common carrier may not be available at all. Communication systems associated with a transmission project may use:

• Microwaves
• Power line communication
• Optical fibers

Rarely, and for short distances, a utility will use pilot-wires strung along the transmission line path. Leased circuits from common carriers are not preferred since availability is not under control of the electric power transmission organization.

Transmission lines can also be used to carry data: this is called power-line carrier, or PLC. PLC signals can be easily received with a radio for the long wave range.

Optical fibers can be included in the stranded conductors of a transmission line, in the overhead shield wires. These cables are known as OPGW or Optical Ground Wire. Sometimes a standalone cable is used, ADSS or All Dielectric Self Supporting cable, attached to the transmission line cross arms.

110 kV double circuit power line of EnBW AG near Leonberg, Germany with an aerial cable mounted like a garland on the ground conductor

Transmission towers in the New Zealand countryside

Some jurisdictions, such as Minnesota, prohibit energy transmission companies from selling surplus communication bandwidth or acting as a telecommunications common carrier. Where the regulatory structure permits, the utility can sell capacity in extra "dark fibers" to a common carrier, providing another revenue stream for the line.

Electricity market reform

Some regulators, economists, and many power companies regard electric transmission to be a natural monopoly^[7][8] and there are moves in many countries to separately regulate transmission (see Electricity market).

Spain was the first country to establish a Regional Transmission Organization. In that country transmission operations and market operations are controlled by separate companies. The transmission system operator is Red Eléctrica de España (REE) [4] and the wholesale electricity market operator is Operador del Mercado Ibérico de Energía - Polo Español, S.A. (OMEL) [5]. Spain's transmission system is interconnected with those of France, Portugal, and Morocco.

In the United States and parts of Canada, electrical transmission companies operate independently of generation and distribution companies.

Merchant transmission

Merchant transmission is an arrangement where a third party constructs and operates electric transmission lines through the franchise area of an unrelated utility. Advocates of merchant transmission^[who?] claim that this will create competition to construct the most efficient and lowest cost additions to the transmission grid. Merchant transmission projects typically involve DC lines because it is easier to limit flows to paying customers.

The only operating merchant transmission project in the United States is the Cross Sound Cable from Long Island, New York to New Haven, Connecticut, although additional projects have been proposed.

There are five merchant transmission interconnectors between five states in Australia: the DirectLink, QNI, MurrayLink and Southern Link between New South Wales and South Australia and Basslink between Tasmania and Victoria.

A major barrier to wider adoption of merchant transmission is the difficulty in identifying who benefits from the facility so that the beneficiaries will pay the toll. Also, it is difficult for a merchant transmission line to compete when the alternative transmission lines are subsidized by other utility businesses.^[9]

Health concerns

Main article: Electromagnetic radiation and health

Some research has found that exposure to elevated levels of ELF magnetic fields such as those originating from electric power transmission lines may be implicated in a number of adverse health effects. These include, but are not limited to, childhood leukemia ^[10], adult leukemia^[11], breast cancer^[12], neurodegenerative diseases (such as amyotrophic lateral sclerosis)^[13][14][15], Miscarriage^[16][17][18], and clinical depression. Although there seems to be a small statistical correlation between various diseases and living near power lines, the physical mechanism is not clear. One proposed mechanism is that the electric fields around power lines attract aerosol pollutants.^[19][20]

One possible response to the potential dangers of overhead power lines is to place them underground. According to the British Stakeholder Advisory Group on ELF EMFs^[21], the cost of burying cables at transmission voltages is around GBP 10M/km, compared to GBP 0.5-1M/km for overhead lines.

Underground cables eliminate the electric field and reduce the width over which the magnetic field is elevated.^[22] However, in reality, protection from the dangers of electromagnetic (EM) fields is seldom the driving concern when burying power lines.

The strongest evidence linking EMF to cancer was fabricated. Most people, when quizzed, have heard of the link between EMF's and cancer, but relatively few people have heard of the fabricated data leaving a public perception that power lines are far more dangerous than they are.[6] Indeed, the UN World Health Organization has concluded "...a cause-and-effect link between ELF field exposure and cancer has not been confirmed."[7]

Special transmission

Grids for railways

In some countries where electric trains run on low frequency AC (e.g. 16.7 Hz and 25 Hz) power, there are separate single phase traction power networks operated by the railways. These grids are fed by separate generators in some traction powerstations or by traction current converter plants from the public three phase AC network.

Radio frequency power transmission

Main article: radio frequency power transmission

Some radio broadcasters use specialized transmission lines to carry the output of high-power transmitters to the antenna.

Superconducting cables

High-temperature superconductors promise to revolutionize power distribution by providing lossless transmission of electrical power. The development of superconductors with transition temperatures higher than the boiling point of liquid nitrogen has made the concept of superconducting power lines commercially feasible, at least for high-load applications. ^[23] It has been estimated that the waste would be halved using this method, since the necessary refrigeration equipment would consume about half the power saved by the elimination of the majority of resistive losses. Such cables are particularly suited to high load density areas such as the business district of large cities, where purchase of a wayleave for cables would be very costly. [8]

Single wire earth return

Main article: Single wire earth return

Single wire earth return (SWER) or single wire ground return is a single-wire transmission line for supplying single-phase electrical power for a electrical grid to remote areas at low cost. It is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps, and light rail. Single wire earth return is also used for HVDC over submarine power cables.

Wireless power transmission

Main article: Wireless energy transfer

Every radio transmitter emits power wirelessly. Both Nikola Tesla and Hidetsugu Yagi attempted to devise systems for large scale wireless power transmission. Tesla claimed to have succeeded.^{[24][25][26][27][28]} Yagi also proposed a similar concept, but the engineering problems proved to be more onerous than conventional systems. His work, however, led to the invention of the Yagi antenna.

Another form of wireless power transmission has been studied for transmission of power from solar power satellites to the earth. A high power array of microwave transmitters would beam power to a rectenna. Major engineering and economic challenges face any solar power satellite project.

Another form is the operation of a crystal radio is powered by the radio station it is tuned to, however the energetic efficiency is extremely low. Small scale wireless power was demonstrated as early as 1831 by Michael Faraday and by 1888 Heinrich Rudolf Hertz had proven that natural radio waves exist and can be captured.

Records

• Highest transmission voltage (AC): 1,150 kV on Powerline Ekibastuz-Kokshetau (Kazakhstan)
• Highest transmission voltage (DC): +/-600 kV on HVDC Itaipu (Brazil)
• Highest pylons: Yangtze River Crossing (height: 345 m (1,132 ft))
• Longest power line: Inga-Shaba (length: 1,700 kilometres (1,056 mi))
• Longest span of power line: 5,376 m (17,638 ft) at Ameralik Span
• Longest submarine cables:
  • NorNed, North Sea - (length of submarine/underground cable: 580 kilometres (360 mi))
  • Basslink, Bass Strait - (length of submarine/underground cable: 290 kilometres (180 mi), total length: 357.4 kilometres (222 mi))
  • Baltic-Cable, Baltic Sea - (length of submarine/underground cable: 249 kilometres (155 mi), total length: 261 kilometres (162 mi))

See also

Look up grid electricity in
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Notes

Further reading

• Grigsby, L. L., et al. The Electric Power Engineering Handbook. USA: CRC Press. (2001). ISBN 0-8493-8578-4
• Thomas P. Hughes, Networks of Power: Electrification in Western Society 1880-1930, The Johns Hopkins University Press,Baltimore 1983 ISBN 0-8018-2873-2, an excellent overview of development during the first 50 years of commercial electric power

• Westinghouse Electric Corporation, "Electric power transmission patents; Tesla polyphase system". (Transmission of power; polyphase system; Tesla patents)

External links

• Japan: World's First In-Grid High-Temperature Superconducting Power Cable System
• A Power Grid for the Hydrogen Economy: Overview/A Continental SuperGrid
• Global Energy Network Institute (GENI) - The GENI Initiative focuses on linking renewable energy resources around the world using international electricity transmission.
• Union for the Co-ordination of Transmission of Electricity (UCTE), the association of transmission system operators in continental Europe, running one of the two largest power transmission systems in the world
• Non-Ionizing Radiation, Part 1: Static and Extremely Low-Frequency (ELF) Electric and Magnetic Fields (2002) by the IARC -- Link Broken.
• Trustworthy Cyber Infrastructure for the Power Grid (TCIP) - The TCIP group at the University of Illinois at Urbana-Champaign has developed applets to illustrate important concepts in mathematics and the science of electricity and the power grid.