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46-590: Henday Converter Station is an HVDC converter station near Sundance in the Canadian province of Manitoba . The Henday Converter Station is the northern terminus for Manitoba Hydro's Bipole II high voltage direct current (HVDC) transmission system and was built in 1977. It is 42 kilometres northeast of the Radisson Converter Station and is close to the Limestone Generating Station . It

92-410: A large DC potential to earth. Converter transformers can be built as large as 300 Mega volt amperes ( MVA ) as a single unit. It is impractical to transport larger transformers, so when larger ratings are required, several individual transformers are connected together. Either two three-phase units or three single-phase units can be used. With the latter variant only one type of transformer is used, making

138-456: A particular excitation (see graph on right). The variations of I {\displaystyle I} with excitation are known as V {\displaystyle V} curves because of their shape. For the same mechanical load, the armature current varies with field excitation over a wide range and so causes the power factor also to vary accordingly. When over-excited, the motor runs with leading power factor (and supplies vars to

184-403: A result, harmonic filters are generally smaller or may be omitted altogether. Beside the harmonic filters, equipment is also provided to eliminate spurious signals in the frequency range of power-line carrier equipment in the range of 30 kHz to 500 kHz. These filters are usually near the alternating current terminal of the static inverter transformer. They consist of a coil which passes

230-421: A rotating magnetic field within the machine. Likewise, the rotor is excited with a DC current I e {\displaystyle I_{e}} to act as an electromagnet. In normal operation the rotor magnet follows the stator field at synchronous speed. The rotating electromagnet induces a three-phase voltage V g {\displaystyle V_{g}} in the stator windings as if

276-481: A small in-phase component, and will not fall to zero. An over-excited synchronous motor has a leading power factor. This makes it useful for power-factor correction of industrial loads. Both transformers and induction motors draw lagging (magnetising) currents from the line. On light loads, the power drawn by induction motors has a large reactive component and the power factor has a low value. The added current flowing to supply reactive power creates additional losses in

322-405: A spill. Substantial area may be required for overhead transmission lines, but can be reduced if underground cable is used. Synchronous condenser In electrical engineering , a synchronous condenser (sometimes called a syncon , synchronous capacitor or synchronous compensator ) is a DC-excited synchronous motor , whose shaft is not connected to anything but spins freely. Its purpose

368-584: A sufficient range of taps for AC voltage control. Some of the reactive power requirement can be supplied in the harmonic filter components. Voltage sourced converters can generate or absorb reactive as well as real power, and additional reactive power equipment is generally not needed. Harmonic filters are necessary for the elimination of the harmonic waves and for the production of the reactive power at line commutated converter stations. At plants with six pulse line commutated converters, complex harmonic filters are necessary because there are odd numbered harmonics of

414-400: A syncon. In this situation, the turbine can be retrofit with either an auxiliary starting motor, use the existing generator as an electric means of startup, or a synchronous self-shifting (SSS) clutch with the existing turbine/fuel source. Using a separate starter motor is usually recommended instead of the existing generator for startup, as the generator shaft/coupling generally can't withstand

460-527: A system was used on the Baltic Cable HVDC project. The converter transformers step up the voltage of the AC supply network. Using a star-to-delta or " wye-delta " connection of the transformer windings, the converter can operate with 12 pulses for each cycle in the AC supply, which eliminates numerous harmonic current components. The insulation of the transformer windings must be specially designed to withstand

506-559: A transmission voltage of 400 kV is approximately 300 x 300 metres (1000 x 1000 feet). Lower-voltage plants may require somewhat less ground area, since less air space clearance would be required around outdoor high-voltage equipment. Converter stations produce acoustic noise. Converter stations can generate serious levels of radio-frequency interference, so include design features to control these emissions. Walls may provide noise protection. As with all AC substations, oil from equipment must be prevented from contaminating ground water in case of

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552-424: Is adjusted to be less than I e0 {\displaystyle I_{\text{e0}}} , V s {\displaystyle V_{s}} will exceed V g {\displaystyle V_{g}} , and a positive reactive current will flow into the machine. The machine will then appear as an inductor whose reactance falls as I e {\displaystyle I_{e}}

598-663: Is called rectification and conversion from DC to AC is called inversion . The direct current equipment often includes a coil (called a reactor ) that adds inductance in series with the DC line to help smooth the direct current. The inductance typically amounts to between 0.1 H and 1 H. The smoothing reactor can have either an air-core or an iron-core. Iron-core coils look like oil-filled high voltage transformers. Air-core smoothing coils resemble, but are considerably larger than, carrier frequency choke coils in high voltage transmission lines and are supported by insulators . Air coils have

644-520: Is generated to where it is used, as is the case with power wheeling , the transmission of electric power from one geographic region to another within a set of interconnected electric power systems. When compared to an SVC, the synchronous condenser has a few advantages: Synchronous condensers may also be referred to as Dynamic Power Factor Correction systems. These machines can prove very effective when advanced controls are utilized. A PLC based controller with PF controller and regulator will allow

690-606: Is no explosion hazard as long as the hydrogen concentration is maintained above 70%, typically above 91%. A syncon can be 8 metres long and 5 meters tall, weighing 170 tonnes. Synchronous condensers also help stabilize grids. The inertial response of the machine and its inductance can help stabilize a power system during rapid fluctuations of loads such as those created by short circuits or electric arc furnaces . For this reason, large installations of synchronous condensers are sometimes used in association with high-voltage direct current converter stations to supply reactive power to

736-504: Is not affected by system electrical harmonics (some harmonics can even be absorbed by synchronous condensers). They will not produce excessive voltage levels and are not susceptible to electrical resonances . Because of the rotating inertia of the synchronous condenser, it can provide limited voltage support during very short power drops. Rotating synchronous condensers were introduced in 1930s and were common in 1950s, but due to high costs were eventually displaced in new installations by

782-493: Is not to convert electric power to mechanical power or vice versa, but to adjust conditions on the electric power transmission grid . Its field is controlled by a voltage regulator to either generate or absorb reactive power as needed to adjust the grid's voltage , or to improve power factor . The condenser’s installation and operation are identical to large electric motors and generators (some generators are actually designed to be able to operate as synchronous condensers with

828-511: Is reduced further. These conditions correspond to the two rising arms of the V-curves (above). In a practical machine with losses, the equivalent circuit will contain a resistor in parallel with the terminals to represent mechanical and magnetic losses, and another resistor in series with the generator and L, representing copper losses in the stator. Thus in a practical machine I s {\displaystyle I_{s}} will contain

874-621: Is that the amount of reactive power from a synchronous condenser can be continuously adjusted. Reactive power from a capacitor bank decreases when grid voltage decreases while the reactive power from a synchronous condenser inherently increases as voltage decreases. Additionally, synchronous condensers are more tolerant of power fluctuations and severe drops in voltage. However, synchronous machines have higher energy losses than static capacitor banks. Most synchronous condensers connected to electrical grids are rated between 20  MVAR (megavar) and 200 MVAR and many are hydrogen cooled . There

920-550: Is usually installed in a building called the valve hall . Early HVDC systems used mercury-arc valves , but since the mid-1970s, solid state devices such as thyristors have been used. Converters using thyristors or mercury-arc valves are known as line commutated converters . In thyristor-based converters, many thyristors are connected in series to form a thyristor valve, and each converter normally consists of six or twelve thyristor valves. The thyristor valves are usually grouped in pairs or groups of four and can stand on insulators on

966-424: The power factor (p.f.) tends to approach unity with increase in mechanical load. This change in power factor is larger than the change in I a {\displaystyle I_{a}} with increase in load. The phase of armature current varies with field excitation. The current has larger values for lower and higher values of excitation. In between, the current has minimum value corresponding to

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1012-406: The prime mover disconnected ). Increasing the device's field excitation results in its furnishing reactive power (measured in units of var ) to the system. Its principal advantage is the ease with which the amount of correction can be adjusted. Synchronous condensers are an alternative to capacitor banks and static VAR compensators for power-factor correction in power grids. One advantage

1058-436: The static var compensators (SVCs). They remain an alternative (or a supplement) to capacitors for power-factor correction because of problems that have been experienced with harmonics causing capacitor overheating and catastrophic failures. Synchronous condensers are also useful for supporting voltage levels. The reactive power produced by a capacitor bank is in direct proportion to the square of its terminal voltage, and if

1104-426: The advantage of generating less acoustical noise than iron-core coils, they eliminate the potential environmental hazard of spilled oil, and they do not saturate under transient high current fault conditions. This part of the plant will also contain instruments for measurement of direct current and voltage. Special direct current filters are used to eliminate high frequency interference. Such filters are required if

1150-404: The alternating current grid. Synchronous condensers are also finding use in facilitating the switchover between power grids and providing power grid stabilization as turbine-based power generators are replaced with solar and wind energy. A rotating coil in a magnetic field tends to produce a sine-wave voltage. When connected to a circuit some current will flow depending on how the voltage on

1196-412: The converter station will require between 40% and 60% of its power rating as reactive power. This can be provided by banks of switched capacitors or by synchronous condensers , or if a suitable power generating station is located close to the static inverter plant, the generators in the power station. The demand for reactive power can be reduced if the converter transformers have on-load tap changers with

1242-422: The converter transformers, isolating switches, grounding switches, and instrument transformers for control, measurement and protection. The station will also have lightning arresters for protection of the AC equipment from lightning surges on the AC system. The area required for a converter station is much larger than a conventional transformer, for example a site with a transmission rating of 600 megawatts and

1288-473: The current in the stator I s {\displaystyle I_{s}} will be zero. This corresponds to the minimum in the curve shown above. If, however, I e {\displaystyle I_{e}} is increased above I e0 {\displaystyle I_{\text{e0}}} , V g {\displaystyle V_{g}} will exceed V s {\displaystyle V_{s}} , and

1334-408: The difference is accounted for by a voltage V 1 {\displaystyle V_{1}} appearing across the stator inductance L {\displaystyle L} : V L = I s X L {\displaystyle V_{L}=I_{s}X_{L}} where X L {\displaystyle X_{L}} is the stator reactance. Now

1380-513: The floor or hang from insulators from the ceiling. Line commutated converters require voltage from the AC network for commutation, but since the late 1990s, voltage sourced converters have started to be used for HVDC. Voltage sourced converters use insulated-gate bipolar transistors instead of thyristors, and these can provide power to a deenergized AC system. Almost all converters used for HVDC are intrinsically able to operate with power conversion in either direction. Power conversion from AC to DC

1426-448: The grid) and when under-excited with lagging power factor (and absorbs vars from the grid). In between, the power factor is unity. The minimum armature current corresponds to the point of unity power factor (voltage and current in phase). As in a synchronous motor, the stator of the machine is connected to a three-phase supply of voltage V s {\displaystyle V_{s}} (assumed to be constant), and this creates

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1472-457: The grid, which is when the SSS clutch disconnects the turbine and generator. The generator thus uses grid energy to keep spinning, to provide leading or lagging reactive power as needed. Each setup has its own advantages and disadvantages: the electric drive only systems do not require combustion from the old turbines, where an old generation system would generally produce more emissions than a newer one of

1518-455: The load current, with a parallel capacitor to form a resonant circuit. In special cases, it may be possible to use exclusively machines for generating the reactive power. This is realized at the terminal of HVDC Volgograd-Donbass situated on Volga Hydroelectric Station . The three-phase alternating current switch gear of a converter station is similar to that of an AC substation. It will contain circuit breakers for overcurrent protection of

1564-463: The machine were a synchronous generator. If the machine is considered to be ideal, with no mechanical, magnetic, or electrical losses, its equivalent circuit will be an AC generator in series with the winding inductance L {\displaystyle L} of the stator. The magnitude of V g {\displaystyle V_{g}} depends on the excitation current I e {\displaystyle I_{e}} and

1610-514: The orders 6 n + 1 and 6 n - 1 produced on the AC side and even harmonics of order 6 n on the DC side. At 12 pulse converter stations, only harmonic voltages or currents of the order 12 n + 1 and 12 n - 1 (on the AC side) or 12 n (on the DC side) result. Filters are tuned to the expected harmonic frequencies and consist of series combinations of capacitors and inductors. Voltage sourced converters generally produce lower intensity harmonics than line commutated converters. As

1656-415: The power system. In an industrial plant, synchronous motors can be used to supply some of the reactive power required by induction motors. This improves the plant power factor and reduces the reactive current required from the grid. A synchronous condenser provides stepless automatic power-factor correction with the ability to produce up to 150% additional vars. The system produces no switching transients and

1702-527: The speed of rotation, and as the latter is fixed, V g {\displaystyle V_{g}} depends only on I e {\displaystyle I_{e}} . If I e {\displaystyle I_{e}} is critically adjusted to a value I e0 {\displaystyle I_{\text{e0}}} , V g {\displaystyle V_{g}} will be equal and opposite to V s {\displaystyle V_{s}} , and

1748-479: The stator current I s {\displaystyle I_{s}} is no longer zero. Since the machine is ideal, V g {\displaystyle V_{g}} , V L {\displaystyle V_{L}} and V s {\displaystyle V_{s}} will all be in phase, and I s {\displaystyle I_{s}} will be entirely reactive (i.e. in phase quadrature). Viewed from

1794-504: The supply of a spare transformer more economical. Converter transformers operate with high flux Power Steps In the Four Steps of the Converter per cycle, and so produce more acoustic noise than normal three-phase power transformers. This effect should be considered in the siting of an HVDC converter station. Noise-reducing enclosures may be applied. When line commutated converters are used,

1840-414: The supply side of the machine's terminals, a negative reactive current will flow out of the terminals, and the machine will therefore appear as a capacitor, the magnitude of whose reactance will fall as I r {\displaystyle I_{r}} increases above I s0 {\displaystyle I_{\text{s0}}} . If I e {\displaystyle I_{e}}

1886-440: The system is different from this open-circuit voltage. Note that mechanical torque (produced by a motor, required by a generator) corresponds only to the real power. Reactive power does not result in any torque. As the mechanical load on a synchronous motor increases, the stator current I a {\displaystyle I_{a}} increases regardless of the field excitation. For both under- and over-excited motors,

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1932-421: The system to be set to meet a given power factor or can be set to produce a specified amount of reactive power. On electric power systems, synchronous condensers can be used to control the voltage on long transmission lines, especially for lines with a relatively high ratio of inductive reactance to resistance. In addition to purpose-built units, existing steam or combustion turbines can be retrofit for use as

1978-568: The system voltage decreases, the capacitors produce less reactive power, when it is most needed, while if the system voltage increases the capacitors produce more reactive power, which exacerbates the problem. In contrast, with a constant field, a synchronous condenser naturally supplies more reactive power to a low voltage and absorbs more reactive power from a high voltage, plus the field can be controlled. This reactive power improves voltage regulation in situations such as when starting large motors, or where power must travel long distances from where it

2024-418: The torques imposed on them during startup. Using purely electric startup methods, the syncon relies on the starter motor to provide an initial startup, and the generator or auxiliary motor provide the system with the necessary rotational inertia to produce reactive power. With the SSS clutch retrofit, the existing turbine setup is largely reused. Here, the turbine uses its existing fuel source to start and sync to

2070-403: The transmission line will use power-line communication techniques for communication and control, or if the overhead line will run through populated areas. These filters can be passive LC filters or active filters, consisting of an amplifier coupled through transformers and protection capacitors, which gives a signal out of phase to the interference signal on the line, thereby cancelling it. Such

2116-584: Was named after Anthony Henday, an eighteenth-century trader who worked for the Hudson's Bay Company. 56°30′14″N 94°08′24″W  /  56.50389°N 94.14000°W  / 56.50389; -94.14000 This article about a building or structure in Manitoba is a stub . You can help Misplaced Pages by expanding it . This article about a Canadian power station is a stub . You can help Misplaced Pages by expanding it . HVDC converter station The converter

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