61-515: Koeberg Nuclear Power Station is a nuclear power station in South Africa and the only one on the African continent. It is located 30 km north of Cape Town , near Melkbosstrand on the west coast. It is owned and operated by the country's state-owned electricity public utility , Eskom . Koeberg contains two pressurised water reactors based on a design by Framatome of France. Framatome has
122-639: A flashover and loss of supply. Oscillatory motion of the physical line is termed conductor gallop or flutter depending on the frequency and amplitude of oscillation. Electric power can be transmitted by underground power cables . Underground cables take up no right-of-way, have lower visibility, and are less affected by weather. However, cables must be insulated. Cable and excavation costs are much higher than overhead construction. Faults in buried transmission lines take longer to locate and repair. In some metropolitan areas, cables are enclosed by metal pipe and insulated with dielectric fluid (usually an oil) that
183-534: A transmission network . This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution . The combined transmission and distribution network is part of electricity delivery , known as the electrical grid . Efficient long-distance transmission of electric power requires high voltages . This reduces the losses produced by strong currents . Transmission lines use either alternating current (AC) or direct current (DC). The voltage level
244-404: A 51% shareholding in local South African company Lesedi Nuclear Services which performs upgrade and maintenance projects at Koeberg. Koeberg supplies power to the national grid so that over-capacity can be redistributed to the rest of the country on an as-needed basis. Fuel stock used within the reactor is enriched uranium dioxide pellets containing gadolinium , contained in fuel rods. Koeberg
305-1096: A few centimetres in diameter), much of the current flow is concentrated near the surface due to the skin effect . The center of the conductor carries little current but contributes weight and cost. Thus, multiple parallel cables (called bundle conductors ) are used for higher capacity. Bundle conductors are used at high voltages to reduce energy loss caused by corona discharge . Today, transmission-level voltages are usually 110 kV and above. Lower voltages, such as 66 kV and 33 kV, are usually considered subtransmission voltages, but are occasionally used on long lines with light loads. Voltages less than 33 kV are usually used for distribution . Voltages above 765 kV are considered extra high voltage and require different designs. Overhead transmission wires depend on air for insulation, requiring that lines maintain minimum clearances. Adverse weather conditions, such as high winds and low temperatures, interrupt transmission. Wind speeds as low as 23 knots (43 km/h) can permit conductors to encroach operating clearances, resulting in
366-575: A much smaller benefit than the squared reduction provided by multiplying the voltage. Long-distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. At higher voltages, where more than 2,000 kV exists between conductor and ground, corona discharge losses are so large that they can offset the lower resistive losses in the line conductors. Measures to reduce corona losses include larger conductor diameter, hollow cores or conductor bundles. Factors that affect resistance and thus loss include temperature, spiraling, and
427-426: A practice that later became known as distributed generation using large numbers of small generators. Transmission of alternating current (AC) became possible after Lucien Gaulard and John Dixon Gibbs built what they called the secondary generator, an early transformer provided with 1:1 turn ratio and open magnetic circuit, in 1881. The first long distance AC line was 34 kilometres (21 miles) long, built for
488-537: A transformer and alternating current lighting system led Westinghouse to begin installing AC systems later that year. In 1888 the first designs for an AC motor appeared. These were induction motors running on polyphase current, independently invented by Galileo Ferraris and Nikola Tesla . Westinghouse licensed Tesla's design. Practical three-phase motors were designed by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown . Widespread use of such motors were delayed many years by development problems and
549-591: A wide area reduced costs. The most efficient plants could be used to supply varying loads during the day. Reliability was improved and capital costs were reduced, because stand-by generating capacity could be shared over many more customers and a wider area. Remote and low-cost sources of energy, such as hydroelectric power or mine-mouth coal, could be exploited to further lower costs. The 20th century's rapid industrialization made electrical transmission lines and grids critical infrastructure . Interconnection of local generation plants and small distribution networks
610-490: Is a network of power stations , transmission lines, and substations . Energy is usually transmitted within a grid with three-phase AC . 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 four wires or three wires with unequal currents. Higher order phase systems require more than three wires, but deliver little or no benefit. While
671-416: Is also used in submarine power cables (typically longer than 30 miles (50 km)), and in the interchange of power between grids that are not mutually synchronized. HVDC links stabilize power distribution networks where sudden new loads, or blackouts, in one part of a network might otherwise result in synchronization problems and cascading failures . Electricity is transmitted at high voltages to reduce
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#1732863064997732-564: Is changed with transformers . The voltage is stepped up for transmission, then reduced for local distribution. A wide area synchronous grid , known as an interconnection in North America, directly connects generators delivering AC power with the same relative frequency to many consumers. North America has four major interconnections: Western , Eastern , Quebec and Texas . One grid connects most of continental Europe . Historically, transmission and distribution lines were often owned by
793-522: Is cooled by cold water from the Atlantic Ocean pumped through an isolated circuit at 80 tons a second. Low and intermediate level waste from Koeberg is transported by road in steel and concrete containers to a rural disposal site at Vaalputs , 600 km away in the Kalahari Desert . The power station was originally located outside the metropolitan area, but urban growth has exceeded expectations in
854-668: Is either static or circulated via pumps. If an electric fault damages the pipe and leaks dielectric, liquid nitrogen is used to freeze portions of the pipe to enable draining and repair. This extends the repair period and increases costs. The temperature of the pipe and surroundings are monitored throughout the repair period. Underground lines are limited by their thermal capacity, which permits less overload or re-rating lines. Long underground AC cables have significant capacitance , which reduces their ability to provide useful power beyond 50 miles (80 kilometres). DC cables are not limited in length by their capacitance. Commercial electric power
915-473: Is improved at higher voltage and lower current. The reduced current reduces heating losses. Joule's first law states that energy losses are proportional to the square of the current. Thus, reducing the current by a factor of two lowers the energy lost to conductor resistance by a factor of four for any given size of conductor. The optimum size of a conductor for a given voltage and current can be estimated by Kelvin's law for conductor size, which states that size
976-482: Is known as the base load and is generally served by large facilities with constant operating costs, termed firm power . Such facilities are nuclear, coal or hydroelectric, while other energy sources such as concentrated solar thermal and geothermal power have the potential to provide firm power. Renewable energy sources, such as solar photovoltaics, wind, wave, and tidal, are, due to their intermittency, not considered to be firm. The remaining or peak power demand,
1037-579: Is nearly always an aluminum alloy, formed of several strands and possibly reinforced with steel strands. Copper was sometimes used for overhead transmission, but aluminum is lighter, reduces yields only marginally and costs much less. Overhead conductors are supplied by several companies. Conductor material and shapes are regularly improved to increase capacity. Conductor sizes range from 12 mm (#6 American wire gauge ) to 750 mm (1,590,000 circular mils area), with varying resistance and current-carrying capacity . For large conductors (more than
1098-401: Is optimal when the annual cost of energy wasted in resistance is equal to the annual capital charges of providing the conductor. At times of lower interest rates and low commodity costs, Kelvin's law indicates that thicker wires are optimal. Otherwise, thinner conductors are indicated. Since power lines are designed for long-term use, Kelvin's law is used in conjunction with long-term estimates of
1159-406: Is partially dependent on the physical orientation of the lines with respect to each other. Three-phase lines are conventionally strung with phases separated vertically. The mutual inductance seen by a conductor of the phase in the middle of the other two phases is different from the inductance seen on the top/bottom. Unbalanced inductance among the three conductors is problematic because it may force
1220-991: Is produced at a relatively low voltage between about 2.3 kV and 30 kV, depending on the size of the unit. The voltage is then stepped up by the power station transformer to a higher voltage (115 kV to 765 kV AC) for transmission. In the United States, power transmission is, variously, 230 kV to 500 kV, with less than 230 kV or more than 500 kV as exceptions. The Western Interconnection has two primary interchange voltages: 500 kV AC at 60 Hz, and ±500 kV (1,000 kV net) DC from North to South ( Columbia River to Southern California ) and Northeast to Southwest (Utah to Southern California). The 287.5 kV ( Hoover Dam to Los Angeles line, via Victorville ) and 345 kV ( Arizona Public Service (APS) line) are local standards, both of which were implemented before 500 kV became practical. Transmitting electricity at high voltage reduces
1281-475: Is rated at 1,860 MW, its average annual production is 13,668 GWh and it has two turbine generators.&. Each reactor delivers 970 MW (gross) and is capable of delivering 930 MW (net) to the grid. The power station was constructed near Cape Town to be the sole provider of power in the Western Cape after fossil-fuel power stations were deemed too small and too expensive to be viable. Nuclear power
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#17328630649971342-666: Is supplied by peaking power plants , which are typically smaller, faster-responding, and higher cost sources, such as combined cycle or combustion turbine plants typically fueled by natural gas. Long-distance transmission (hundreds of kilometers) is cheap and efficient, with costs of US$ 0.005–0.02 per kWh, compared to annual averaged large producer costs of US$ 0.01–0.025 per kWh, retail rates upwards of US$ 0.10 per kWh, and multiples of retail for instantaneous suppliers at unpredicted high demand moments. New York often buys over 1000 MW of low-cost hydropower from Canada. Local sources (even if more expensive and infrequently used) can protect
1403-411: Is swapped at specially designed transposition towers at regular intervals along the line using various transposition schemes . Subtransmission runs at relatively lower voltages. It is uneconomical to connect all distribution substations to the high main transmission voltage, because that equipment is larger and more expensive. Typically, only larger substations connect with this high voltage. Voltage
1464-465: The I 2 R {\displaystyle I^{2}R} losses are still reduced ten-fold using the higher voltage. While power loss can also be reduced by increasing the wire's conductance (by increasing its cross-sectional area), larger conductors are heavier and more expensive. And since conductance is proportional to cross-sectional area, resistive power loss is only reduced proportionally with increasing cross-sectional area, providing
1525-568: The Daily Maverick reported that Eskom's then Chief Nuclear Officer, Riedewaan Bakardien had left the utility, also noting an Eskom estimated loss of between 250 and 300 "skilled persons" in 2022, putting at risk the planned R20 billion life extension. Source: After the Fukushima Daiichi nuclear disaster , seismic safety at Koeberg was reevaluated in conjunction with the IAEA . Although Koeberg
1586-519: The international electricity exhibition in Frankfurt . A 15 kV transmission line, approximately 175 km long, connected Lauffen on the Neckar and Frankfurt. Transmission voltages increased throughout the 20th century. By 1914, fifty-five transmission systems operating at more than 70 kV were in service. The highest voltage then used was 150 kV. Interconnecting multiple generating plants over
1647-712: The resistance define the impedance ) constitute reactive power flow, which transmits no power to the load. These reactive currents, however, cause extra heating losses. The ratio of real power transmitted to the load to apparent power (the product of a circuit's voltage and current, without reference to phase angle) is the power factor . As reactive current increases, reactive power increases and power factor decreases. For transmission systems with low power factor, losses are higher than for systems with high power factor. Utilities add capacitor banks, reactors and other components (such as phase-shifters ; static VAR compensators ; and flexible AC transmission systems , FACTS) throughout
1708-399: The resistive losses . For example, raising the voltage by a factor of 10 reduces the current by a corresponding factor of 10 and therefore the I 2 R {\displaystyle I^{2}R} losses by a factor of 100, provided the same sized conductors are used in both cases. Even if the conductor size (cross-sectional area) is decreased ten-fold to match the lower current,
1769-506: The skin effect . Resistance increases with temperature. Spiraling, which refers to the way stranded conductors spiral about the center, also contributes to increases in conductor resistance. The skin effect causes the effective resistance to increase at higher AC frequencies. Corona and resistive losses can be estimated using a mathematical model. US transmission and distribution losses were estimated at 6.6% in 1997, 6.5% in 2007 and 5% from 2013 to 2019. In general, losses are estimated from
1830-524: The 1884 International Exhibition of Electricity in Turin, Italy . It was powered by a 2 kV, 130 Hz Siemens & Halske alternator and featured several Gaulard transformers with primary windings connected in series, which fed incandescent lamps. The system proved the feasibility of AC electric power transmission over long distances. The first commercial AC distribution system entered service in 1885 in via dei Cerchi, Rome, Italy , for public lighting. It
1891-512: The AC grid. These stopgaps were slowly replaced as older systems were retired or upgraded. The first transmission of single-phase alternating current using high voltage came in Oregon in 1890 when power was delivered from a hydroelectric plant at Willamette Falls to the city of Portland 14 miles (23 km) down river. The first three-phase alternating current using high voltage took place in 1891 during
Koeberg Nuclear Power Station - Misplaced Pages Continue
1952-568: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.150 via cp1114 cp1114, Varnish XID 443211364 Upstream caches: cp1114 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 06:51:05 GMT Electric power transmission Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant , to an electrical substation . The interconnected lines that facilitate this movement form
2013-401: The ability to link all the loads. These included single phase AC systems, poly-phase AC systems, low voltage incandescent lighting, high-voltage arc lighting, and existing DC motors in factories and street cars. In what became a universal system, these technological differences were temporarily bridged via the rotary converters and motor-generators that allowed the legacy systems to connect to
2074-405: The backup capacity began running out. At this point, rotational load shedding was employed, with customers being switched off in stages for most of the day. Koeberg was re-synchronised to the national grid on Saturday 26 November. On Sunday 25 December 2005, the generator of Unit 1 was damaged. While the generator was being powered up after scheduled refuelling and maintenance, a loose bolt, which
2135-551: The discrepancy between power produced (as reported by power plants) and power sold; the difference constitutes transmission and distribution losses, assuming no utility theft occurs. As of 1980, the longest cost-effective distance for DC transmission was 7,000 kilometres (4,300 miles). For AC it was 4,000 kilometres (2,500 miles), though US transmission lines are substantially shorter. In any AC line, conductor inductance and capacitance can be significant. Currents that flow solely in reaction to these properties, (which together with
2196-420: The energy loss due to resistance that occurs over long distances. Power is usually transmitted through overhead power lines . Underground power transmission has a significantly higher installation cost and greater operational limitations, but lowers maintenance costs. Underground transmission is more common in urban areas or environmentally sensitive locations. Electrical energy must typically be generated at
2257-569: The first practical series AC transformer in 1885. Working with the support of George Westinghouse , in 1886 he demonstrated a transformer-based AC lighting system in Great Barrington, Massachusetts . It was powered by a steam engine-driven 500 V Siemens generator. Voltage was stepped down to 100 volts using the Stanley transformer to power incandescent lamps at 23 businesses over 4,000 feet (1,200 m). This practical demonstration of
2318-409: The fraction of energy lost to Joule heating , which varies by conductor type, the current, and the transmission distance. For example, a 100 miles (160 km) span at 765 kV carrying 1000 MW of power can have losses of 0.5% to 1.1%. A 345 kV line carrying the same load across the same distance has losses of 4.2%. For a given amount of power, a higher voltage reduces the current and thus
2379-474: The intervening years, so that the power station is now close to suburban housing. The administration enforces maximum housing density regulations in case of evacuation, which precludes the construction of high rise buildings. The buffer zone around the nuclear power station forms the 22 km Koeberg Nature Reserve , open to the public and containing more than 210 species of birds and a number of mammal species including zebra, eland and springbok. Construction of
2440-566: The line to trip, causing severe voltage dips which resulted in Koeberg once again shutting down. Parts of the Cape were left without electricity for hours at a time. On the evening of 23 November, a routine inspection of the backup safety system revealed a below-spec concentration of an important chemical, resulting in a controlled shutdown of the reactor. Due to the sufficiency of backup supply, major power cuts were not experienced until Friday 25 November, when
2501-451: The middle line to carry a disproportionate amount of the total power transmitted. Similarly, an unbalanced load may occur if one line is consistently closest to the ground and operates at a lower impedance. Because of this phenomenon, conductors must be periodically transposed along the line so that each phase sees equal time in each relative position to balance out the mutual inductance seen by all three phases. To accomplish this, line position
Koeberg Nuclear Power Station - Misplaced Pages Continue
2562-597: The power station began in 1976, and Unit 1 was synchronized to the grid on 4 April 1984. Unit 2 followed on 25 July 1985. On 17 December 1982, Umkhonto we Sizwe , the armed wing of the ANC attacked Koeberg while it was still under construction. Damage was estimated at R 500 million and the commissioning of the power station was put back by 18 months. The bomber was Rodney Wilkinson , who had previously represented South Africa in international fencing tournaments. In August 2002 twelve Greenpeace activists obtained access to
2623-528: The power supply from weather and other disasters that can disconnect distant suppliers. Hydro and wind sources cannot be moved closer to big cities, and solar costs are lowest in remote areas where local power needs are nominal. Connection costs can determine whether any particular renewable alternative is economically realistic. Costs can be prohibitive for transmission lines, but high capacity, long distance super grid transmission network costs could be recovered with modest usage fees. At power stations , power
2684-467: The price of copper and aluminum as well as interest rates. Higher voltage is achieved in AC circuits by using a step-up transformer . High-voltage direct current (HVDC) systems require relatively costly conversion equipment that may be economically justified for particular projects such as submarine cables and longer distance high capacity point-to-point transmission. HVDC is necessary for sending energy between unsynchronized grids. A transmission grid
2745-514: The price of generating capacity is high, energy demand is variable, making it often cheaper to import needed power than to generate it locally. Because loads often rise and fall together across large areas, power often comes from distant sources. Because of the economic benefits of load sharing, wide area transmission grids may span countries and even continents. Interconnections between producers and consumers enables power to flow even if some links are inoperative. The slowly varying portion of demand
2806-446: The risk of such a failure by providing multiple redundant , alternative routes for power to flow should such shutdowns occur. Transmission companies determine the maximum reliable capacity of each line (ordinarily less than its physical or thermal limit) to ensure that spare capacity is available in the event of a failure in another part of the network. High-voltage overhead conductors are not covered by insulation. The conductor material
2867-500: The same company, but starting in the 1990s, many countries liberalized the regulation of the electricity market in ways that led to separate companies handling transmission and distribution. Most North American transmission lines are high-voltage three-phase AC, although single phase AC is sometimes used in railway electrification systems . DC technology is used for greater efficiency over longer distances, typically hundreds of miles. High-voltage direct current (HVDC) technology
2928-639: The same rate at which it is consumed. A sophisticated control system is required to ensure that power generation closely matches demand. If demand exceeds supply, the imbalance can cause generation plant(s) and transmission equipment to automatically disconnect or shut down to prevent damage. In the worst case, this may lead to a cascading series of shutdowns and a major regional blackout . The US Northeast faced blackouts in 1965 , 1977 , 2003 , and major blackouts in other US regions in 1996 and 2011 . Electric transmission networks are interconnected into regional, national, and even continent-wide networks to reduce
2989-621: The scarcity of polyphase power systems needed to power them. In the late 1880s and early 1890s smaller electric companies merged into larger corporations such as Ganz and AEG in Europe and General Electric and Westinghouse Electric in the US. These companies developed AC systems, but the technical difference between direct and alternating current systems required a much longer technical merger. Alternating current's economies of scale with large generating plants and long-distance transmission slowly added
3050-481: The station. Six of them scaled the wall to hang up an anti-nuclear protest banner. The twelve were arrested and fined. At the end of 2005, Koeberg started experiencing numerous technical difficulties. On 11 November 2005, a fault on a transmission busbar caused the reactor to go into safe mode, cutting supply to most of the Western Cape for about two hours. On 16 November a fire under a 400 kV transmission line caused
3111-409: The system help to compensate for the reactive power flow, reduce the losses in power transmission and stabilize system voltages. These measures are collectively called 'reactive support'. Current flowing through transmission lines induces a magnetic field that surrounds the lines of each phase and affects the inductance of the surrounding conductors of other phases. The conductors' mutual inductance
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#17328630649973172-538: The unit was brought back into operation in May 2006. On 18 and 19 February 2007 large parts of the Western Cape again experienced blackouts due to a controlled shutdown of Koeberg. According to Eskom and the City of Cape Town, power cuts were to continue until 26 February 2007, however power supply problems continued beyond this date. The estimated economic losses due to the power cuts was over R 500 M as at February 2007, and
3233-477: Was considered because it was more economical than transporting coal to the existing fossil-fuel power stations, and construction of new fossil-fuel power-stations, which would have required 300 m tall chimneys to comply with clean-air legislation. Athlone Power Station in the city was too small to provide Cape Town's needs, and the Paarden Island power station (also too small) has been demolished. Koeberg
3294-803: Was designed for 0.3g zero period ground acceleration (ZPGA), a magnitude 7 earthquake, stress tests evaluated Koeberg against a 0.5g ZPGA. Overall Koeberg was found to be seismically robust and well designed, with some areas for attention and improvement that were highlighted. Duynefontein next door on the northern side of Koeberg is a proposed site for a new nuclear power station. South Africa's nuclear industry has seen opposition, chiefly from environmentalists concerned about safety issues such as radioactive waste , and anti-war activists concerned about nuclear proliferation and use of atomic weapons. Current campaigns against nuclear energy are being run by Earthlife Africa and Koeberg Alert . Nuclear power station Too Many Requests If you report this error to
3355-551: Was estimated to rise to possibly as high as R 2 billion. On 12 September 2010, 91 members of staff were contaminated with cobalt-58 dust in an incident that appeared confined to the station. The government's agreed 2019 Integrated Resource Plan (IRP) plans a 20-year life-extension for Koeberg to 2044, and a delayed nuclear new build programme with a scenario that may build new capacity after 2030. On 10 September 2020, Eskom announced it will replace six steam generators. The design, manufacture and install contract with Areva
3416-518: Was for ZAR 4.4 billion ($ 240 million), with manufacture subcontracted to the Shanghai Electric Power . Installation was delayed to 2023 and 2024 because of concerns about possible power shortages. Koeberg 1's outage began on 10 December 2022 and it came back synchronised with the grid on 18 November 2023, taking much longer than the expected six months. Koeberg 2 will begin its outage once Koeberg 1's recommissioning tests are complete. In 2022,
3477-452: Was initially transmitted at the same voltage used by lighting and mechanical loads. This restricted the distance between generating plant and loads. In 1882, DC voltage could not easily be increased 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. Thus, generators were sited near their loads,
3538-406: Was left inside the generator caused severe damage, forcing it to be shut down. Subsequent to the unexpected unavailability of Unit 1, Unit 2 was also brought down for scheduled refuelling, resulting in a severe shortage of supply to the Western Cape. This resulted in widespread load shedding in order to maintain the stability of the network. A replacement rotor for Unit 1 was shipped in from France and
3599-531: Was one of the first nuclear power stations designed to be resistant to earthquakes . The reactors at the Koeberg nuclear power station are built on an aseismic raft designed – on the basis of a mid-1970s hazard study - to withstand a magnitude 7 earthquake at a focal distance of about 10 km, 0.3g zero period ground acceleration (ZPGA). The largest recorded earthquake in the Cape Town area has been 6.5 magnitude at Jan Biesjes Kraal in 1809. The reactor at Koeberg
3660-648: Was powered by two Siemens & Halske alternators rated 30 hp (22 kW), 2 kV at 120 Hz and used 19 km of cables and 200 parallel-connected 2 kV to 20 V step-down transformers provided with a closed magnetic circuit, one for each lamp. A few months later it was followed by the first British AC system, serving Grosvenor Gallery . It also featured Siemens alternators and 2.4 kV to 100 V step-down transformers – one per user – with shunt-connected primaries. Working to improve what he considered an impractical Gaulard-Gibbs design, electrical engineer William Stanley, Jr. developed
3721-426: Was spurred by World War I , when large electrical generating plants were built by governments to power munitions factories. These networks use components such as power lines, cables, circuit breakers , switches and transformers . The transmission network is usually administered on a regional basis by an entity such as a regional transmission organization or transmission system operator . Transmission efficiency
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