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Controllable |
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Controllable |
Adapted from a paper presented
to the IEEE Power Engineering Society Summer Meeting, Seattle, July 20, 2000,
and also published in the Official Proceedings
of the Thirteenth International Power Quality 2000 Conference and Exhibit,
Boston, October 3-5, 2000 (Adams/Intertec, Ventura, CA: 2000), pp. 810-816.
Prof. Alexander M. Bryantsev, Moscow Power Institute, Smolensk; Mark D. Galperin, PhD, Expanding Edge LLC, San Anselmo, California; Prof. George A. Evdokunin, State Technical University of St. Petersburg; Andrei G. Dolgopolov, PhD, VEI Scientific & Engineering Center of Togliatti, Russia
Abstract
In a new, magnetically controlled reactor (MCR), in which DC pulsing through a special winding controls inductive susceptance, high saturation of the magnetic circuit steel with optimal magnetic and electrical circuit parameters ensures less than 2-3% main harmonic distortion even without special filters. Simple, transformer-like construction ensures reliable operation.
MCRs increase power quality through automatic voltage regulation, reduced fluctuation, and smoothing of reactive power surges. Damping of voltage-oscillation increases power stability limits, permitting higher voltage transmission. MCRs support voltage levels at 1/3 the cost of series capacitive compensation.
Technically, economically, and in maintenance terms, MCRs compete most handsomely against thyristor-controlled reactors (TCRs), and together with capacitor banks, against SVC s and synchronous condensers.
A magnetically controlled reactor (MCR) is a device in which DC pulsing through a part of the power winding or through a special control winding changes the duration-to-period ratio (or relative duration) of the magnetic-core saturation, thereby changing the inductance and inductive susceptance of the MCR as a whole. In functional terms, MCRs are powerful low-inertia inductors in which reactive power consumption can be regulated from .01 to 1.0 times rated power, with short-term regulation (up to one minute) up to 2.0 times rated power. Because of this very wide range of control, MCRs significantly reduce idle-mode power losses. They also increase operational reliability of electrical grids, and optimize power-line operating conditions.
MCRs are based on two original principles:
(1) The first principle of the MCR is generation and control of the direct component of the magnetic flux in the MCRs two cores by periodic shorting of some of the reactor winding turns by the use of semiconductor switches [1];
(2) The second principle of the MCR is profound magnetic saturation of the two cores under rated conditions, when the saturation magnetization generated by the direct component of the magnetic flux is achieved over about half or more of the grid-frequency period [2]. The theory and design of such devices are considered in more detail in [3, 4, 5]. The basic electrical circuits of controllable reactors are shown in Fig. 1a-c, and photographs of representative types of MCRs are presented in Fig. 2a-b.
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Figure 1.
Fig 1a.
Fig. 1b.
Fig. 1c. |
On the basis of these principles, a number of electrical engineering companies in the CIS have been developing and producing single-phase arc quenching reactors for 6 to 35 kV grids with insulated neutral, and three-phase shunt reactors for 6 to 35 kV industrial and residential electric grids, for over ten years. Among these, Energiya Electrotechnical Plant of Ramenskoe, Russia ("REZE") has been producing single-phase arc quenching MCRs for grids with isolated neutral since 1995.
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Figure 2. |
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Fig. 2a. |
Fig. 2b |
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Five of the most important of these companiesÅ REZE, Zaporozhtransformator (Ukraine), the All-Russia Electrical Engineering Institute ("VEI"), the VEI Scientific & Engineering Center of Togliatti, and Elektrocenter (Russia)Å have organized themselves as the Controllable Electric Reactor Consortium ("CERC") for the development, production, delivery, debugging, and maintenance of MCRs for larger grids of 110 to 1150 kV.
The consortium has already produced three-phase MCRs for high-voltage 110 to 220 kV distribution grids, as well as three-phase groups of single-phase MCRs for 330 to 500 kV transit and system power lines. On the basis of existing transformers of up to 500 MVA, 1150 kV, it can also produce MCRs with the same rated parameters.
Significantly, as mentioned, CERC MCRs can smoothly control voltage by regulating power consumption from .01 to 1.0 times rated power with an effective time constant of 0.1 sec. They can also provide short-term (up to 1 min) non-inertial boosts in power consumption to 2 times rated value. And finally, they are capable of phase-by-phase control.
The first three-phase shunt reactorÅ the MCR 25/110, produced for a high-voltage 110-kV distribution gridÅ successfully underwent full-scale testing in 1997 and was installed by the Permenergo Joint Stock Company at its Kudymkar, Permskaya Region substation. This reactor now ensures automatic voltage stabilization at substation buses and in the adjacent grid, reduces power loss due to reactive-power transfer decrease between the power-supply center and the substation by as much as 2.5 MW, and has reduced the number of capacitor-bank switching operations required for voltage regulation from 800 per year to an astonishing one per month. The reactor recouped its cost in two years, largely because of reduced power losses in the adjacent grid. Analysis by specialists at the Energosetprojekt Institute shows that the MCR-25/110 is economically most efficient at substations located 80 to 100 km or more from the power supply center.
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Figure 3.
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The MCR-180/500 controllable shunt reactor for extrahigh-voltage lines was developed at the end of the 1980 s for the Unified Electrical System ("OES") of Russia. The prototype successfully underwent grid tests in 1992. Single-line connection of this reactor is illustrated in Fig. 3: in accordance with a mismatch signal generated by a measurement system (4, 5), a control device (3) operates a thyristor converter (2), which in turn generates direct current, magnetizing the phase magnetic system and producing a smooth change in reactive power consumed by the phases of reactor (1). This ensures automatic stabilization of the voltage at the point of reactor connection. With increase in voltage deviation to 2.5% of the specified setting, the power consumed in reactor (1) varies smoothly from idling to rated power in proportion to the mismatch signal.
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Figure 4.
t = 0 to 1.0 sec. with boosted power consumption at t = 0.13 to 0.27 sec. (both modes simulated). Non-inertial boosting is achieved by short-term shorting of the MCR control winding by 35 kV vacuum breaker. |
Fig. 4 illustrates the basic capabilities of the MCR-180/500 by showing phase current and voltage changes that result under smooth regulation and non-inertial boosting conditions.
Analysis of power systems in Russia, Kazakhstan, Brazil, India, and China shows that controllable 500 kV reactors would provide voltage stabilization and control of operating conditions for power systems and long-distance power lines. For example, installing ten three-phase controllable reactors in 500 kV grids together with ordinary shunt reactors would ensure voltage stabilization and operational control for all of Kazakhstan s extra-high-voltage long-distance power lines. Generally, to achieve such system aims, according to OES rough estimates, about 30% of the reactors in 500 kV grids should be controllable. A group of three single-phase MCR 60/500 reactors (i.e., a three-phase MCR 180/500) would cost only 1.7 to 2 times more than a three-phase group of non-controllable reactors of the same parameters, and about 2 times less than a similar three-phase thyristor-controlled reactor ("TCR") installation.
With strong production and operational experience in mid-voltage systems, as well as operational experience and long-term test results with high- and extrahigh-voltage systems, CERC is ready to introduce a wide range of magnetically controlled shunt reactors to the power industry.
In design, operating parameters, reliability, ease of use, and longevity, these reactors are comparable to both ordinary transformers and reactor equipment, but because they are automatically controllable, they significantly simplify grid operation and enhance power quality.
Total Cost of Ownership (TCO) as a percentage of ex-works price is as follows: delivery (brokerage, customs, etc.), 5 to 10%; construction and installation, average 25% (depending on location); operation and maintenance, 4% per annum. In other words, the TCO of an MCR is similar to that of a transformer of the same class.
Mean Time Between Failure (MTBF): The manufacturer guarantees its MCRs for a lifetime of not less than 25 years, with first major maintenance guaranteed not to occur within 12 years. Each phase of the reactor, its grounding filter and current-distortion corrector (an LC filter) are guaranteed for a minimum of 3 years. The power control system, including the transformer with its built-in thyristor subsystem is guaranteed for one year. The average practical time to failure of smaller MCRs is 5 years.
Technically as well as commercially, MCRs compete with striking success against thyristor-controlled reactors (TCR s). MCRs with capacitor banks may also be used with similar effectiveness and economic results in branched electrical grids in place of synchronous condensers and SVC s.
CERC is represented for international marketing purposes by of San Anselmo, California.
Get details on each of the following MCRs:
MCR
180/500:
3-Phase 180 Mvar, 500kV
for grids and substations
MCR
25/110:
3 Phase 25 Mvar, 110kV
for grids and substations
MCR
Single-Phase:
Automatic Ground-Fault Neutralizer
for grids with isolated neutral
1. A.M. Bryantsev, Power Reactor with Magnetization, Russian Patent No. 989597, 1983 (in Russian).
2. A.M. Bryantsev, Electrical Inductor, Author s Certificate No. 1061180 SSSR, 1983 (in Russian).
3. A.M. Bryantsev, "Principal Equations and Characteristics of Magnetic- Rectifier Controlled Reactors with Strong Saturation of the Magnetic Circuit", in Soviet Electrical Engineering, v. 62, No. 2, pp. 37-43, 1991, Allerton Pess Inc. Translated into English from Elektrotekhnika, v. 62, No. 2, pp. 24-28, 1991.
4. M.A. Biki, E.N. Brodovoi, A.M. Bryantsev, Yu. L. Chizhevskii, L.V. Leites and A.I. Lur e: "Electromagnetic Processes in High-Power Controlled Reactors", in Electrical Technologies, No. 2, pp. 127-143, 1994, Pergamon-Elsevier Science Ltd. Translated into English from Elektrichestvo, 1994, No. 6, pp. 1-10.
5. A.M. Bryantsev, B.I. Bazylev, M.A. Biki, S.V. Ukolov, A.G. Dolgopolov, A.I. Lur e, G.A. Yevdokunin, G.A. Slavin: "Magnetically Controlled Shunt Reactors: New Electrical Equipment", Elektrotekhnika, No. 7, pp. 1-8, 1999 (in Russian); translated into English as "A New Electrical Device: The Magnetization-Controlled Shunting Reactor", Russian Electrical Engineering, v. 70, No. 2, Allerton Press Inc. (in publication).
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