89-911: Download coordinates as: HVDC Vancouver Island is a de-energized high-voltage direct current interconnection owned by BC Hydro that runs between Arnott Substation (ARN) in Delta, British Columbia at 49°5′31″N 123°2′31″W / 49.09194°N 123.04194°W / 49.09194; -123.04194 ( Arnott Substation ) on the Canadian mainland, and the Vancouver Island Terminal (VIT) in Duncan, British Columbia on Vancouver Island at 48°49′39″N 123°42′55″W / 48.82750°N 123.71528°W / 48.82750; -123.71528 ( Vancouver Island Terminal ) . It went into operation in 1968 and
178-497: A vector product , decreases. Since DC power has no phase, the phase shift cannot occur in the DC case. HVDC transmission may also be selected for other technical benefits. HVDC can transfer power between separate AC networks. HVDC power flow between separate AC systems can be automatically controlled to support either network during transient conditions, but without the risk that a major power-system collapse in one network will lead to
267-554: A 12 kV DC transmission line, which also served to convert 40 Hz generation to serve 60 Hz loads, at Mechanicville, New York . In 1941, a 60 MW, ±200 kV, 115 km (71 mi) buried cable link, known as the Elbe-Project , was designed for the city of Berlin using mercury arc valves but, owing to the collapse of the German government in 1945 , the project was never completed. The nominal justification for
356-452: A circuit that is effectively an ultra-high-voltage motor drive. More recent installations, including HVDC PLUS and HVDC MaxSine, are based on variants of a converter called a Modular Multilevel Converter (MMC). Multilevel converters have the advantage that they allow harmonic filtering equipment to be reduced or eliminated altogether. By way of comparison, AC harmonic filters of typical line-commutated converter stations cover nearly half of
445-452: A collapse in the second. The controllability feature is also useful where control of energy trading is needed. Specific applications where HVDC transmission technology provides benefits include: Long undersea or underground high-voltage cables have a high electrical capacitance compared with overhead transmission lines since the live conductors within the cable are surrounded by a relatively thin layer of insulation (the dielectric ), and
534-466: A cost per acre of one dollar after proving they had done so. Before 1871 (when the merged Colony of British Columbia joined Canada), all property acquired on Salt Spring Island was purchased in this way; between 1871 and 1881, it was still by far the primary method of land acquisition, accounting for 96% of purchases. As a result, the history of early settlers on Salt Spring Island is unusually detailed. The method of land purchase helped to ensure that
623-410: A distance of 200 kilometres (120 mi), including 10 kilometres (6.2 mi) of underground cable. This system used eight series-connected generators with dual commutators for a total voltage of 150 kV between the positive and negative poles, and operated from c. 1906 until 1936. Fifteen Thury systems were in operation by 1913. Other Thury systems operating at up to 100 kV DC worked into
712-468: A given transmission line to operate with a constant HVDC voltage that is approximately the same as the peak AC voltage for which it is designed and insulated. The power delivered in an AC system is defined by the root mean square (RMS) of an AC voltage, but RMS is only about 71% of the peak voltage. Therefore, if the HVDC line can operate continuously with an HVDC voltage that is the same as the peak voltage of
801-446: A high resistance when conducting, wasting energy and generating heat in normal operation. The ABB breaker combines semiconductor and mechanical breakers to produce a hybrid breaker with both a fast break time and a low resistance in normal operation. Generally, vendors of HVDC systems, such as GE Vernova , Siemens and ABB , do not specify pricing details of particular projects; such costs are typically proprietary information between
890-460: A metal sheath. The geometry is that of a long coaxial capacitor . The total capacitance increases with the length of the cable. This capacitance is in a parallel circuit with the load. Where alternating current is used for cable transmission, additional current must flow in the cable to charge this cable capacitance. Another way to look at this is to realize, that such capacitance causes a phase shift between voltage and current, and thus decrease of
979-405: A much lesser extent. Nevertheless, for a long AC overhead transmission line, the current flowing just to charge the line capacitance can be significant, and this reduces the capability of the line to carry useful current to the load at the remote end. Another factor that reduces the useful current-carrying ability of AC lines is the skin effect , which causes a nonuniform distribution of current over
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#17327911610641068-482: A result of a civil war in Mozambique . The transmission voltage of ±533 kV was the highest in the world at the time. Line-commutated converters have some limitations in their use for HVDC systems. This results from requiring a period of reverse voltage to affect the turn off. An attempt to address these limitations is the capacitor-commutated converter (CCC). The CCC has series capacitors inserted into
1157-486: A result of lack of civic services on the island or other factors, such as the livestock-killing cold of the winter of 1862. During World War II , 77 Japanese Canadian families living on Salt Spring Island were forcibly relocated away from the coast due to the Internment of Japanese Canadians . Gavin C. Mouat was appointed Custodian of the properties they left behind. Despite evidence of verbal reassurances given to
1246-401: A similar concept HVDC PLUS ( Power Link Universal System ) and Alstom call their product based upon this technology HVDC MaxSine . They have extended the use of HVDC down to blocks as small as a few tens of megawatts and overhead lines as short as a few dozen kilometers. There are several different variants of VSC technology: most installations built until 2012 use pulse-width modulation in
1335-489: A single-circuit three-phase AC line until 49°2′25″N 123°4′32″W / 49.04028°N 123.07556°W / 49.04028; -123.07556 ( Metallic Return Cable Terminal ) . From there it runs as underground cable to Splashdown Park, where it transits at 49°1′58″N 123°5′26″W / 49.03278°N 123.09056°W / 49.03278; -123.09056 ( Metallic Return Cable Terminal ) again into an overhead line, which ends at
1424-413: A three-phase bridge rectifier known as a six-pulse bridge , containing six electronic switches, each connecting one of the three phases to one of the two DC rails. A complete switching element is usually referred to as a valve , irrespective of its construction. However, with a phase change only every 60°, considerable harmonic distortion is produced at both the DC and AC terminals when this arrangement
1513-454: A valve becoming positive (at which point the valve would start to conduct if it were made from diodes) and the thyristors being turned on. The DC output voltage of the converter steadily becomes less positive as the firing angle is increased: firing angles of up to 90° correspond to rectification and result in positive DC voltages, while firing angles above 90° correspond to inversion and result in negative DC voltages. The practical upper limit for
1602-544: A vital role in protecting the unique environment and vibrant community of Salt Spring Island. The Royal Canadian Marine Search and Rescue Station 25 (RCMSAR25) is volunteer organization operated by the Gulf Island Marine Rescue Society (GIMRS) that maintains a permanent 24/7 marine search and rescue capability in the vicinity of Salt Spring Island BC Canada. The organization responds to marine search and rescue emergencies as well as engaging with
1691-450: A weight of 4.5 metric tons. The valves are situated in a hall 26.21 metres (86.0 feet) long, 11.89 metres (39.0 feet) wide and 11.28 metres (37.0 feet) high. The maximum transmission capacity of this pole was 312 megawatts and the transmission voltage was 260 kV. The stations Vancouver Island Terminal and Arnott Substation were designed and delivered by Swedish company ASEA (later ABB ). The Swedish team of some 10 people were headed for
1780-462: A wider power transmission grid to another. Changes in load that would cause portions of an AC network to become unsynchronized and to separate, would not similarly affect a DC link, and the power flow through the DC link would tend to stabilize the AC network. The magnitude and direction of power flow through a DC link can be directly controlled and changed as needed to support the AC networks at either end of
1869-440: Is also known as line-commutated converter (LCC) HVDC. On March 15, 1979, a 1920 MW thyristor based direct current connection between Cabora Bassa and Johannesburg (1,410 km; 880 mi) was energized. The conversion equipment was built in 1974 by Allgemeine Elektricitäts-Gesellschaft AG (AEG) , and Brown, Boveri & Cie (BBC) and Siemens were partners in the project. Service interruptions of several years were
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#17327911610641958-475: Is complex (especially with line commutated converters), as is expanding existing schemes to multi-terminal systems. Controlling power flow in a multi-terminal DC system requires good communication between all the terminals; power flow must be actively regulated by the converter control system instead of relying on the inherent impedance and phase angle properties of an AC transmission line. Multi-terminal systems are therefore rare. As of 2012 only two are in service:
2047-425: Is connected with Arnott Substation by an overhead pole line with two conductors. The electrode on Vancouver Island is a shore electrode in a bay at Sansum Narrows at 48°46′22″N 123°34′24″W / 48.77278°N 123.57333°W / 48.77278; -123.57333 ( Sansum Narrows Ground Electrode ) . It is connected with Vancouver Island Terminal by an overhead line with two conductors, which
2136-513: Is installed on wooden poles. It runs between Vancouver Island Terminal and a point northwest of Maple Bay at 48°49′35″N 123°37′38″W / 48.82639°N 123.62722°W / 48.82639; -123.62722 ( Sansum Narrows Ground Electrode Line Branch ) parallel to other power lines. High-voltage direct current A high-voltage direct current ( HVDC ) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with
2225-467: Is left over from £750M for the installed works. Add another £200–300M for the other works depending on additional onshore works required. An April 2010 announcement for a 2,000 MW, 64 km (40 mi) line between Spain and France is estimated at €700 million. This includes the cost of a tunnel through the Pyrenees. At the heart of an HVDC converter station , the equipment that performs
2314-539: Is lower than 600 A. Otherwise earth return was used. On Vancouver Island the line for metallic return is a monopolar line on wooden poles, which are used in some sections also by AC lines, running parallel to the main line of HVDC Vancouver Island. On the mainland, it uses the poles of the electrode line until a point at 49°3′39″N 123°2′34″W / 49.06083°N 123.04278°W / 49.06083; -123.04278 ( Metallic Return Branch ) . After this point it runs on wooden poles together with
2403-625: Is no potential difference. DC will never cross zero volts and never self-extinguish, so arc distance and duration is far greater with DC than the same voltage AC. This means some mechanism must be included in the circuit breaker to force current to zero and extinguish the arc, otherwise arcing and contact wear would be too great to allow reliable switching. In November 2012, ABB announced the first ultrafast HVDC circuit breaker. Mechanical circuit breakers are too slow for use in HVDC grids, although they have been used for years in other applications. Conversely, semiconductor breakers are fast enough but have
2492-531: Is referred to as the rectifier and the station that is operating with power flow from DC to AC is referred to as the inverter . Early HVDC systems used electromechanical conversion (the Thury system) but all HVDC systems built since the 1940s have used electronic converters. Electronic converters for HVDC are divided into two main categories: Most of the HVDC systems in operation today are based on line-commutated converters (LCCs). The basic LCC configuration uses
2581-640: Is served by the Ganges and Fulford Harbour exchanges. Active Radio Amateurs maintain wireless repeaters located on Mt Bruce. 2 meter band (147.320 MHz). Coverage from Nanaimo, Vancouver and Victoria. Salt Spring Island Fire Rescue (SSIFR) is the primary emergency response agency serving Salt Spring Island,. Established in approximately 1946 to ensure the safety and well-being of the island's residents and visitors, SSIFR provides fire suppression, medical response, technical rescue, and public education services. Responding to approximately 750 calls per year, SSIFR plays
2670-580: Is the largest, most populous, and the most frequently visited of the Southern Gulf Islands . Salt Spring Island, or ĆUÁN ( čuʔén ), was initially inhabited by Salishan peoples of various tribes. Other Saanich placenames on the island include: ȾESNO¸EṈ¸ ( t̕ᶿəsnáʔəŋ̕ ) for Beaver Point, S¸ĆUÁN ( sʔčuʔén ) for Cape Keppel, W̱ENÁ¸NEĆ ( xʷən̕en̕əč ) for Fulford Harbour, SYOW̱T ( syaxʷt ) for Ganges Harbour, and ṮÁȽEṈ ( ƛ̕éɬəŋ ) for Isabella Point. The North side of
2759-648: Is the most frequently visited of the Gulf Islands as well as the most populous, with a 2016 census population of 10,557 inhabitants. The largest village on the island is Ganges . The island is known for its artists. In addition to Canadian dollars, island banks and some island businesses accept Salt Spring's own local currency, the Salt Spring dollar . The island is part of the Southern Gulf Islands , (Salt Spring Island, Galiano Island , Pender Island , Saturna Island , Mayne Island ), which are all part of
HVDC Vancouver Island - Misplaced Pages Continue
2848-542: Is used, the cable capacitance is charged only when the cable is first energized or if the voltage level changes; there is no additional current required. DC powered cables are limited only by their temperature rise and Ohm's law . Although some leakage current flows through the dielectric insulator , this effect is also present in AC systems and is small compared to the cable's rated current. The capacitive effect of long underground or undersea cables in AC transmission applications also applies to AC overhead lines, although to
2937-422: Is used. An enhancement of this arrangement uses 12 valves in a twelve-pulse bridge . The AC is split into two separate three-phase supplies before transformation. One of the sets of supplies is then configured to have a star (wye) secondary, and the other a delta secondary, establishing a 30° phase difference between the two sets of three phases. With twelve valves connecting each of the two sets of three phases to
3026-588: The Capital Regional District , along with the municipalities of Greater Victoria . Salt Spring Island's highest point of elevation is Bruce Peak, which according to topographic data from Natural Resources Canada is just over 700 m (2,300 ft) above sea level. Salt Spring Island has a temperate warm-summer mediterranean climate (Csb) and experiences warm, dry summers and cool winters. Salt Spring Island has many hiking trails. Two of these trails are rough and windy trails that lead to
3115-592: The Quebec – New England Transmission between Radisson, Sandy Pond, and Nicolet and the Sardinia–;mainland Italy link which was modified in 1989 to also provide power to the island of Corsica . HVDC circuit breakers are difficult to build because of arcing : under AC, the voltage inverts and in doing so crosses zero volts dozens of times a second. An AC arc will self-extinguish at one of these zero-crossing points because there cannot be an arc where there
3204-776: The 1930s in Sweden ( ASEA ) and in Germany . Early commercial installations included one in the Soviet Union in 1951 between Moscow and Kashira , and a 100 kV, 20 MW system between Gotland and mainland Sweden in 1954. Before the Chinese project of 2019, the longest HVDC link in the world was the Rio Madeira link in Brazil , which consists of two bipoles of ±600 kV, 3150 MW each, connecting Porto Velho in
3293-516: The 1930s, but the rotating machinery required high maintenance and had high energy loss. Various other electromechanical devices were tested during the first half of the 20th century with little commercial success. One technique attempted for conversion of direct current from a high transmission voltage to lower utilization voltage was to charge series-connected batteries , then reconnect the batteries in parallel to serve distribution loads. While at least two commercial installations were tried around
3382-570: The 1960s, the island became a political refuge for United States citizens, this time for draft evaders during the Vietnam War . The island was known as "Chuan" or "Chouan" Island in 1854, but it was also called "Salt Spring" as early as 1855, because of the island's salt springs . In 1859, it was officially named "Admiralty Island" in honour of Rear-Admiral Robert Lambert Baynes by surveyor Captain Richards, who named various points of
3471-493: The AC equivalent line, then for a given current (where HVDC current is the same as the RMS current in the AC line), the power transmission capability when operating with HVDC is approximately 40% higher than the capability when operating with AC. Because HVDC allows power transmission between unsynchronized AC distribution systems, it can help increase system stability, by preventing cascading failures from propagating from one part of
3560-479: The AC line connections. CCC has remained only a niche application because of the advent of voltage-source converters (VSCs) which more directly address turn-off issues. Widely used in motor drives since the 1980s, voltage-source converters (VSCs) started to appear in HVDC in 1997 with the experimental Hellsjön–Grängesberg project in Sweden. By the end of 2011, this technology had captured a significant proportion of
3649-432: The DC link. The disadvantages of HVDC are in conversion, switching, control, availability, and maintenance. HVDC is less reliable and has lower availability than alternating current (AC) systems, mainly due to the extra conversion equipment. Single-pole systems have availability of about 98.5%, with about a third of the downtime unscheduled due to faults. Fault-tolerant bipole systems provide high availability for 50% of
HVDC Vancouver Island - Misplaced Pages Continue
3738-592: The HVDC market. The development of higher rated insulated-gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), and integrated gate-commutated thyristors (IGCTs), has made HVDC systems more economical and reliable. This is because modern IGBTs incorporate a short-circuit failure mode, wherein should an IGBT fail, it is mechanically shorted. Therefore, modern VSC HVDC converter stations are designed with sufficient redundancy to guarantee operation over their entire service lives. The manufacturer ABB Group calls this concept HVDC Light , while Siemens calls
3827-633: The Integrated Land Management Bureau of British Columbia, locals incline equally to Salt Spring and Saltspring for current use. The official chamber of commerce website for the island, which gives a date of 1906 for the renaming, adopts the two word title, stating that the Geographic Board of Canada, in choosing the one word name, "cared nothing for local opinion or Island tradition." Located between Mainland British Columbia and Vancouver Island, Salt Spring Island
3916-488: The Tsawwassen Beach Terminal at 49°1′40″N 123°6′1″W / 49.02778°N 123.10028°W / 49.02778; -123.10028 ( Mainland Cable Terminal 2 ) , where the first submarine cable section begins. At 48°55′07″N 123°24′15″W / 48.91861°N 123.40417°W / 48.91861; -123.40417 ( Galiano Island Cable Terminal East ) ,
4005-522: The cable reaches Salt Spring Island and the third overhead line section starts. It crosses Salt Spring Island west-south-westerly. North of Maxwell Point at 48°49′54″N 123°33′50″W / 48.83167°N 123.56389°W / 48.83167; -123.56389 ( Sansum Narrows DC Powerline Span East End ) and Arbutus Point at 48°49′40″N 123°35′21″W / 48.82778°N 123.58917°W / 48.82778; -123.58917 ( Sansum Narrows DC Powerline Span West End )
4094-558: The colony to interview Governor James Douglas about what kind of treatment they could expect there. The Governor was a Guyanese man of multi-ethnic birth, and assured them that people of African descent in Canada would be fairly treated and that the colony had abolished slavery more than 20 years before. Throughout the 1800s, Vesuvius and Ganges were predominantly African-American communities. Racial tensions arose between August 1867 and December 1868, when three Black men were murdered in
4183-581: The commissioning of replacement thyristor converters. The development of thyristor valves for HVDC began in the late 1960s. The first complete HVDC scheme based on thyristor was the Eel River scheme in Canada, which was built by General Electric and went into service in 1972. Since 1977, new HVDC systems have used solid-state devices , in most cases thyristors . Like mercury arc valves, thyristors require connection to an external AC circuit in HVDC applications to turn them on and off. HVDC using thyristors
4272-576: The community of Vesuvius Bay. The murderers were largely blamed on the local coastal Indigenous community. Many of the murders remained unsolved by authorities, leading to a hostile environment for Black residents whose population subsequently dwindled. Much of the youth moved away to Victoria, Vancouver, and on occasion to the United States. The island was the first of the Gulf Islands to be settled by non-First Nations people. According to 1988's A Victorian Missionary and Canadian Indian Policy , it
4361-436: The conversion between AC and DC is referred to as the converter . Almost all HVDC converters are inherently capable of converting from AC to DC ( rectification ) and from DC to AC ( inversion ), although in many HVDC systems, the system as a whole is optimized for power flow in only one direction. Irrespective of how the converter itself is designed, the station that is operating (at a given time) with power flow from AC to DC
4450-402: The converter station area. With time, voltage-source converter systems will probably replace all installed simple thyristor-based systems, including the highest DC power transmission applications. A long-distance, point-to-point HVDC transmission scheme generally has lower overall investment cost and lower losses than an equivalent AC transmission scheme. Although HVDC conversion equipment at
4539-428: The cross-sectional area of the conductor. Transmission line conductors operating with direct current suffer from neither constraint. Therefore, for the same conductor losses (or heating effect), a given conductor can carry more power to the load when operating with HVDC than AC. Finally, depending upon the environmental conditions and the performance of overhead line insulation operating with HVDC, it may be possible for
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#17327911610644628-643: The early 1930s, but officially formed the Salt Spring Island Public Library Association in 1960. The demand for books and resources has only grown since then, requiring constant expansions over the years to accommodate the needs of the island residents. In December 2012, the new Salt Spring Island Public Library was opened. The library is staffed by two librarians, among other paid positions and 87 volunteers. Telecommunications service providers include Telus and Shaw, with most wireless carriers providing coverage. The Island
4717-407: The energy lost as heat in the wires is directly proportional to the square of the current ( energy lost as heat = current 2 ⋅ resistance ⋅ time ) , {\textstyle ({\text{energy lost as heat}}={\text{current}}^{2}\cdot {\text{resistance}}\cdot {\text{time}}),} using half the current at double the voltage reduces
4806-403: The existing two HVDC lines and replaces one of two earlier 138 kV lines. In the 2005 hearings for the new 230kV circuit the HVDC systems were reported to be at the end of their service life and are not considered to be reliable. As a result of this, the first pole was shut down in 2014 and the second in 2016. HVDC Vancouver Island used metallic return, during monopolar operation, when current
4895-486: The families in which Mouat said "when you come back, not one chopstick will be missing from your home," Mouat sold the properties below market value using his Custodial rights without the consent of the owners. Salt Spring Lands Ltd., of which Mouat was the president, ended up purchasing some of the properties. Only one of the interned families, the Murakami's, purchased property on the island again and returned. During
4984-427: The firing angle is about 150–160° because above this, the valve would have insufficient turnoff time. Early LCC systems used mercury-arc valves , which were rugged but required high maintenance. Because of this, many mercury-arc HVDC systems were built with bypass switchgear across each six-pulse bridge so that the HVDC scheme could be operated in six-pulse mode for short maintenance periods. The last mercury arc system
5073-583: The first phase by Ivan Hedlund and for the second phase by Gunnar Ahgren. In 1977 the HVDC Vancouver Island link was supplemented by installing a second pole. This pole used thyristor valves for its static inverters and operated at a voltage of 280 kV with a rating of 370 megawatts. A new 230 kV. submarine cable for three-phase alternating current has been constructed between the Canadian mainland and Vancouver Island. This parallels
5162-628: The first submarine cable section ends and a short overhead line section running south-west across Galiano Island starts. The overhead line leaves Galiano Island south of Montague Harbour in an 880-metre-long span, which starts at 48°52′51″N 123°23′21″W / 48.88083°N 123.38917°W / 48.88083; -123.38917 ( Galiano Island-Parker Island Span East End ) and ends on Parker Island at 48°52′48″N 123°24′04″W / 48.88000°N 123.40111°W / 48.88000; -123.40111 ( Galiano Island-Parker Island Span West End ) . A little to
5251-623: The island in honour of the Rear-Admiral and his flagship, HMS Ganges . Even while named "Admiralty Island", it was referred to popularly as Salt Spring, as in James Richardson's report for the Geological Survey of Canada in 1872. According to records of the Geographic Board of Canada, the island was officially retitled Saltspring on March 1, 1910, though the year 1905 is given by unofficial sources. According to
5340-845: The island is provided by BC Transit . BC Ferries operates three routes to Salt Spring: between Tsawwassen (on the BC mainland) and Long Harbour (on the east side of Salt Spring), between Swartz Bay (at the north end of Vancouver Island's Saanich Peninsula) and Fulford Harbour (at the south end of Salt Spring), and between Crofton (on the east side of Vancouver Island) and Vesuvius (on the west side of Salt Spring). Salt Spring Air , Seair Seaplanes and Harbour Air Seaplanes operate floatplane services from Ganges Water Aerodrome to Vancouver Harbour Water Airport and Vancouver International Water Airport . Kenmore Air operates between Ganges and Lake Union , Seattle , United States. Library facilities have existed on Salt Spring in one form or another since
5429-640: The island was originally settled mostly by African Americans from California , while the South side was settled by Native Hawaiians known as ' Kanaka '. Other settlers included those from Portugal and the British Isles, including English, Irish, and Scots. Black settlers left California in 1858 after the state passed discriminatory legislation targeting African-Americans. Before the emigration, Mifflin Wistar Gibbs travelled with two other men up to
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#17327911610645518-537: The land was used for agricultural purposes and that the settlers were mostly families. Ruth Wells Sandwell in Beyond the City Limit indicates that few of the island's early residents were commercial farmers , with most families maintaining subsistence plots and supplementing through other activities, including fishing , logging , and working for the colony's government. Some families later abandoned their land as
5607-745: The last mercury arc HVDC system (the Nelson River Bipole 1 system in Manitoba , Canada) having been put into service in stages between 1972 and 1977. Since then, all mercury arc systems have been either shut down or converted to use solid-state devices. The last HVDC system to use mercury arc valves was the Inter-Island HVDC link between the North and South Islands of New Zealand, which used them on one of its two poles. The mercury arc valves were decommissioned on 1 August 2012, ahead of
5696-678: The line losses by a factor of 4. While energy lost in transmission can also be reduced by decreasing the resistance by increasing the conductor size, larger conductors are heavier and more expensive. High voltage cannot readily be used for lighting or motors, so transmission-level voltages must be reduced for end-use equipment. Transformers are used to change the voltage levels in alternating current (AC) transmission circuits, but cannot pass DC current. Transformers made AC voltage changes practical, and AC generators were more efficient than those using DC. These advantages led to early low-voltage DC transmission systems being supplanted by AC systems around
5785-662: The link capacity, but availability of the full capacity is about 97% to 98%. The required converter stations are expensive and have limited overload capacity. At smaller transmission distances, the losses in the converter stations may be bigger than in an AC transmission line for the same distance. The cost of the converters may not be offset by reductions in line construction cost and power line loss. Operating an HVDC scheme requires many spare parts to be kept, often exclusively for one system, as HVDC systems are less standardized than AC systems and technology changes more quickly. In contrast to AC systems, realizing multi-terminal systems
5874-481: The mainland splits at 49°3′38″N 123°4′30″W / 49.06056°N 123.07500°W / 49.06056; -123.07500 ( Powerline Branch ) into two branches, one running to the Canoe Pass Terminal at 49°3′6″N 123°7′22″W / 49.05167°N 123.12278°W / 49.05167; -123.12278 ( Mainland Cable Terminal 1 ) and the other running to
5963-462: The more common alternating current (AC) transmission systems. Most HVDC links use voltages between 100 kV and 800 kV. HVDC lines are commonly used for long-distance power transmission, since they require fewer conductors and incur less power loss than equivalent AC lines. HVDC also allows power transmission between AC transmission systems that are not synchronized . Since the power flow through an HVDC link can be controlled independently of
6052-496: The overhead line crosses Sansum Narrows , the strait between Salt Spring Island and Vancouver Island, by a 1900-metre-long span. After this span the overhead line runs westward to Vancouver Island Terminal near the town of Duncan . In 1968 the first pole of the HVDC Vancouver Island link went into service. Its static inverters use mercury vapour rectifiers . Each of these rectifiers was 3.35 metres (11.0 feet) long, 1.22 metres (4.0 feet) wide and 6.10 metres (20.0 feet) high and has
6141-450: The phase angle between source and load, it can stabilize a network against disturbances due to rapid changes in power. HVDC also allows the transfer of power between grid systems running at different frequencies, such as 50 and 60 Hz. This improves the stability and economy of each grid, by allowing the exchange of power between previously incompatible networks. The modern form of HVDC transmission uses technology developed extensively in
6230-542: The project was that, during wartime, a buried cable would be less conspicuous as a bombing target. The equipment was moved to the Soviet Union and was put into service there as the Moscow–Kashira HVDC system. The Moscow–Kashira system and the 1954 connection by Uno Lamm 's group at ASEA between the mainland of Sweden and the island of Gotland marked the beginning of the modern era of HVDC transmission. Mercury arc valves were common in systems designed up to 1972,
6319-402: The same voltage. This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power . In other words, transmitting electric AC power over long distances inevitably results in a phase shift between voltage and current. Because of this phase shift the effective Power=Current*Voltage, where * designates
6408-521: The selection. However, some practitioners have provided some information: For an 8 GW 40 km (25 mi) link laid under the English Channel , the following are approximate primary equipment costs for a 2000 MW 500 kV bipolar conventional HVDC link (excluding way-leaving , on-shore reinforcement works, consenting, engineering, insurance, etc.) So for an 8 GW capacity between Britain and France in four links, little
6497-781: The state of Rondônia to the São Paulo area with a length of more than 2,500 km (1,600 mi). High voltage is used for electric power transmission to reduce the energy lost in the resistance of the wires. For a given quantity of power transmitted, doubling the voltage will deliver the same power at only half the current: power = ( voltage ) ⋅ ( current ) = ( 2 ⋅ voltage ) ⋅ ( 1 2 ⋅ current ) {\displaystyle {\text{power}}=({\text{voltage}})\cdot ({\text{current}})=(2\cdot {\text{voltage}})\cdot ({\tfrac {1}{2}}\cdot {\text{current}})} Since
6586-623: The summit regions of both Bruce Peak 709 m (2,326 ft) above sea level, and Mount Tuam 602 meters (1,975 feet) above sea level. These two mountain peaks are the tallest points of land on the Southern Gulf Islands. Short hikes can also be found on the island. One of these is the 2 km (1.2 mi) long trek to the summit of Mount Erskine, which is 436 m (1,430 ft) above sea level. Cycling on Saltspring Island may involve large elevation changes and poor road conditions with limited curb space. Local bus transit on
6675-414: The supplier and the client. Costs vary widely depending on the specifics of the project (such as power rating, circuit length, overhead vs. cabled route, land costs, site seismology, and AC network improvements required at either terminal). A detailed analysis of DC vs. AC transmission costs may be required in situations where there is no obvious technical advantage to DC, and economical reasoning alone drives
6764-513: The terminal of the main line at 49°1′40″N 123°6′1″W / 49.02778°N 123.10028°W / 49.02778; -123.10028 ( Mainland Cable Terminal 2 ) . The electrode on the Canadian Mainland is a land electrode situated at Boundary Bay at 49°03′25″N 123°01′46″W / 49.05694°N 123.02944°W / 49.05694; -123.02944 ( Boundary Bay Ground Electrode ) . It
6853-538: The terminal stations is costly, the total DC transmission-line costs over long distances are lower than for an AC line of the same distance. HVDC requires less conductor per unit distance than an AC line, as there is no need to support three phases and there is no skin effect . AC systems use a higher peak voltage for the same power, increasing insulator costs. Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per 1,000 km (620 mi), about 50% less than AC (6.7%) lines at
6942-435: The transmitted power, which is a vector product of voltage and current. Additional energy losses also occur as a result of dielectric losses in the cable insulation. For a sufficiently long AC cable, the entire current-carrying ability of the conductor would be needed to supply the charging current alone. This cable capacitance issue limits the length and power-carrying ability of AC power cables. However, if direct current
7031-519: The turn of the 20th century, the technique was not generally useful owing to the limited capacity of batteries, difficulties in switching between series and parallel configurations, and the inherent energy inefficiency of a battery charge/discharge cycle. First proposed in 1914, the grid controlled mercury-arc valve became available during the period 1920 to 1940 for the rectifier and inverter functions associated with DC transmission. Starting in 1932, General Electric tested mercury-vapor valves and
7120-452: The turn of the 20th century. Practical conversion of current between AC and DC became possible with the development of power electronics devices such as mercury-arc valves and, starting in the 1970s, power semiconductor devices including thyristors , integrated gate-commutated thyristors (IGCTs), MOS-controlled thyristors (MCTs) and insulated-gate bipolar transistors (IGBT). The first long-distance transmission of electric power
7209-400: The two DC rails, there is a phase change every 30°, and harmonics are considerably reduced. For this reason, the twelve-pulse system has become standard on most line-commutated converter HVDC systems built since the 1970s. With line commutated converters, the converter has only one degree of freedom – the firing angle , which represents the time delay between the voltage across
7298-610: The voltage across the valve is evenly shared between the thyristors. The thyristor plus its grading circuits and other auxiliary equipment is known as a thyristor level . Salt Spring Island Salt Spring Island or Saltspring Island is one of the Gulf Islands in the Strait of Georgia between mainland British Columbia , Canada, and Vancouver Island . The island was initially inhabited by various Salishan peoples before being settled by pioneers in 1859, at which time it
7387-485: The voltage. Each set was insulated from electrical ground and driven by insulated shafts from a prime mover . The transmission line was operated in a constant-current mode, with up to 5,000 volts across each machine, some machines having double commutators to reduce the voltage on each commutator. This system transmitted 630 kW at 14 kV DC over a distance of 120 kilometres (75 mi). The Moutiers–Lyon system transmitted 8,600 kW of hydroelectric power
7476-421: The west, on Parker Island at 48°52′45″N 123°24′9″W / 48.87917°N 123.40250°W / 48.87917; -123.40250 ( Parker Island Cable Terminal ) the overhead line ends and the second submarine cable section begins. At 48°51′2″N 123°25′31″W / 48.85056°N 123.42528°W / 48.85056; -123.42528 ( Salt Spring Island Cable Terminal )
7565-591: Was demonstrated using direct current in 1882 at Miesbach-Munich Power Transmission , but only 1.5 kW was transmitted. An early method of HVDC transmission was developed by the Swiss engineer René Thury and his method, the Thury system, was put into practice by 1889 in Italy by the Acquedotto De Ferrari-Galliera company. This system used series-connected motor-generator sets to increase
7654-409: Was extended in 1977. HVDC Vancouver Island consists of three overhead line sections with a total length of 42 kilometres and two submarine cable sections with a length of 33 kilometres. Pole 1 ceased operation in 2014, and Pole 2 ceased operation in 2016. The infrastructure remains in place and portions may be re-used in the future. After its departure from Arnott Substation the overhead power line on
7743-474: Was renamed Admiral Island . It was the first of the Gulf Islands to be settled and the first agricultural settlement on the islands in the Colony of Vancouver Island , as well as the first island in the region to permit settlers to acquire land through pre-emption . The island was retitled to its current name in 1910. It is named for the salt springs found in the northern part of the island. Salt Spring Island
7832-642: Was shut down in 2012. The thyristor valve was first used in HVDC systems in 1972. The thyristor is a solid-state semiconductor device similar to the diode , but with an extra control terminal that is used to switch the device on at a particular instant during the AC cycle. Because the voltages in HVDC systems, up to 800 kV in some cases, far exceed the breakdown voltages of the thyristors used, HVDC thyristor valves are built using large numbers of thyristors in series. Additional passive components such as grading capacitors and resistors need to be connected in parallel with each thyristor in order to ensure that
7921-629: Was the first agricultural settlement established anywhere in the Colony of Vancouver Island that was not owned by the Hudson's Bay Company or its subsidiary the Pugets Sound Agricultural Company . Salt Spring Island was the first in the Colony of Vancouver Island and British Columbia to allow settlers to acquire land through pre-emption: settlers could occupy and improve the land before purchase, being permitted to buy it at
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