MAGNETICALLY CONTROLLED REACTORS TO ENHANCE TRANSMISSION CAPABILITY& SAVE ENERGY full
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.doc   MAGNETICALLY CONTROLLED REACTORS TO ENHANCE TRANSMISSION CAPABILITY AND SAVE ENERGY.doc (Size: 657.5 KB / Downloads: 321)


MAGNETICALLY CONTROLLED REACTORS TO ENHANCE TRANSMISSION CAPABILITY& SAVE ENERGY

ABSTRACT
The reactive power problem will become intensified in the future with the increasing use of EHV overhead lines and high-voltage cable in densely populated areas. Generators alone, with their under excited
limitations during light load periods, may not have sufficient capability to control voltages in some systems in which substantial amounts of high-voltage cable are used. Turbine generators with automatic voltage regulators, however, can be operated successfully in the under excited region to minimize the problem of excessive system capacitive reactive loading.
Although shunt reactors are an effective solution, economics may suggest other methods. Nevertheless, shunt reactors are helpful in controlling voltage during a system start-up.
The proposed technique is to have a glance at the magnetically controlled Reactors. These magnetically controlled reactors (MCRs) are proving to be more efficient and reliable and more cost effective than other reactive power control devices. Magnetically Controlled Reactors Enhance Transmission Capability & Save Energy. Especially in Compact Increased Surge-Impedance-Loading Power Lines

Presented BY:
SMD.SANAULLA
IV B.Tech(EEE)
MADINA ENGINEERING COLLEGE
EMAILConfusedana02eee@yahoo.com


1. Benefits of Controllable Reactors
AC distribution grids usually do not require shunt reactors, but do require capacitor banks (i.e. capacitive shunt compensation). These capacitor banks need to be controlled because of changing load conditions. Yet the manual or thyristor switching operations typically used for capacitor bank control are not really efficient and wear out both switching equipment and power transformers. And they do not actually meet reactive power load and voltage control requirements efficiently, since the step control they provide does not really fit the load smoothly.
Intrinsic line capacitance in long AC grids of 400 kV or higher must be compensated to decrease reactive load losses, which can quickly become unacceptably large because they are proportional to the square of line voltage. Compensation must also ease the Ferranti effect under dynamic load conditions. Usually this is accomplished with shunt reactors, and some of these need to be controlled as well. In 500 kV grids the optimum ratio of controllable to non-controllable shunt reactors in a power transmission grid is about 1:3, in order to dampen all significant voltage surges and to improve power stability limits. With compensation at this level, higher voltage can be transmitted even through extended power lines. This also saves energy. In extreme cases, power transmission losses can be decreased by about 30% in this way. In US grids, where power transmission loss is about 4%, power transmission savings would be 1 to 2 percent.
Flexible control of reactive power and voltage in both lower and higher voltage grids is usually realized by static var compensators (SVCs) or more sophisticated static synchronous compensators (STATCOMs), or by controllable reactors apart from SVCs.
SVCs employ controllable reactors along with capacitor banks to control reactive power load, to dampen voltage surges and to decrease power transmission loss by decreasing reactive current circulation. STATCOMs do not use controllable reactors, but thyristors only. But when controllable shunt reactors are used, whether by themselves or within SVCs, the most common are thyristorcontrolled reactors (TCRs).
2. A New Type of Controlled Reactor
Another type of shunt reactor, however, whose principle of operation is extremely high saturation of the magnetic core. These magnetically controlled reactors (MCRs) are proving to be more efficient and reliable and more cost effective than other reactive power control devices.
As is well known, TCRs require a high-rated thyristor system, and this is the main cause of their unreliability. Magnetic reactor control is based on low-power magnetic biasing, and does not require such high-rated thyristors. Further inefficiencies are eliminated by the fact that, for the same reason, MCRs also do not require step-down transformers to decrease grid voltage to rated thyristor voltage, which must be less than 35 kV.
2.1. Advantages of the MCR
¢ MCRs are as reliable and simple to operate and maintain as ordinary transformers. TCRs, on the other hand, require special handling, specialized personnel, and more electrical filters.
¢ In more than 20 years™ field operation of what is now 40 installations, no MCR has ever needed replacement, because their closed, compensated magnetic systems do not suffer mechanical damage under dynamic regimes. The typical lifetime of a TCR is about 10 years because their open, non-compensated magnetic system suffers such damage.
¢ MCRs can sustain 50% overload for 20 minutes and 100% overload for 20 seconds. Compare TCRs, which can sustain 50% overload for 20 seconds and 100% overload for 3 seconds.
¢ The overvoltage limitation of an MCR is 2.3 times rated voltage. By contrast, TCRs have an overvoltage limitation of 1.8 times rated voltage.
¢ The current-distortion coefficient of the MCR, without filters, is less than 3%. With TCRs, the same coefficient is 5.8%. Thus, fewer filters are required with MCRs.
¢ MCRs require no specialized (chemical) operation and maintenance substation personnel to oversee the thyristor cooling system. TCRs, on the other hand, do require such workers because a sophisticated water cooling system is required.
¢ MCRs require about 10 sq. ft / Mvar of the substation open space. TCRs require about 100 sq. ft / Mvar.
¢ MCRs have a low external magnetic field because of the closed magnetic circuit of the reactor phases, and require no electromagnetic shielding. TCRs require significant shielding because of their open magnetic circuit of the reactor phases.
¢ MCRs experience about half the internal power loss of TCRs: 0.05% kW per kvar of rated reactive power (rkvar) in standby no-load mode, and 0.5% kW per rkvar in rated reactive power load mode. TCRs are about double this.
¢ MCRs can be designed to respond like TCRs, in as little as 0.02 second. But the price of an MCR is related to response time and thus, although MCRs of the shortest response time would cost about the same as equivalent TCRs” approximately $20/kvar” for more typical grid requirements of 1 second, they cost only half as much as TCRs, or about $10-11/kvar (ex works price).
¢ MCRs cost half as much as TCRs to install, operate, and maintain.
¢ More important than this cost differential, though, is the sheer reliability of this new technology.
3. Practical approach of MCRs
In Russia, at Permenergoâ„¢s 80 MVA Kudymkar substation, which was equipped with capacitor banks, power fluctuations required over 800 manual switching events per year, serious capital outlay for labor, and rapid depreciation of attached switching and transformer equipment. An MCR was installed in 1999. The system immediately stabilized, and only twelve manual switching events have been necessary per year since then. The substation saved 7.3 GW-hours over the first year, and construction of a new power line, which had been planned, has become unnecessary for at least 10 more years. The utility has saved well in excess of $25M and in just two short years, has all but recovered the cost of installing the MCR.
3.1. MCRs and Compact High Surge-Impedance-Loading Power Lines
One important application of MCRs is their use with compact high surge-impedance-loading (HSIL) power lines. Transmission capability in AC overhead lines is limited by inductive impedance. Inductive impedance can be compensated with series capacitors, but such compensation is costly and creates difficulties for system operation. Lowering the inductive impedance in HSIL long distance transmission lines decreases the power angle between the line terminals and improves steady state stability limits without series capacitive compensation. When the power load becomes lower than the surge-impedance loading of the line, long-line reactive power and voltage can most efficiently be managed by means of controllable electric shunt reactors, 6] of which the most reliable, cost effective and energy-saving type is the MCR.
4.Transparencies :

1. Steep dependence of differential magnetic permeability of MCR core on
magnetic field strength facilitates very effective control of MCR inductance.
2. Principles of operation, schematic of a shunt MCR, and example of
transient process in an MCR.
3. General schematics of 6-35 kV Arc-Quenching MCRs, MCRs for
Distribution substations, and MCRs for 100-500 kV grids.
4. Field experience with MCR-based SVC: 32c/25i Mvar, 110 kV at
Kudymkar Substation in Northeastern European Russia (PermEnergo).
5. Magnetically Controlled Reactor MCR 25/110, 3-Phase, 110kV,
25MVA.
6. Arc-Quenching Magnetically Controlled Reactor (AQMCR) 190 kvar,
11/33 kV.
4.1. Transparency 1:
Steep dependence of differential magnetic permeability of MCR core on magnetic field strength facilitates very effective control of MCR inductance. In any transformer steel, magnetic-flux density B in teslas (T) is quasi-piecewise-linear dependent on magnetic field strength H, in amperes per meter (A/m). The differential magnetic permeability of the MCR core steel is very steeply dependent on H” µ (H) = B (H) / dH.
An increase of H from 5 A/m to 25 kA/m results in a decrease of µ of about 10,000 times to the constant value µ0, (permeability of vacuum). µ does not change at higher values of H (saturation).
This facilitates very effective control of MCR inductance. Increasing direct current in the MCR control winding increases H. This increase of H decreases µ as described above. Decreasing µdecreases MCR inductance. Decrease of MCR inductance decreases shunt MCR reactance, and decreasing reactance increases the reactive power consumed by shunt MCR. Thus current in the MCR control winding switches the MCR on and off.
4.2.Transparency 2:
Principles of operation, schematic, and example of transient process in an MCR.
1. Principles of Operation
Changes of inductance in magnetically controlled reactors (MCRs) are achieved through controlled changes of magnetic field strength in the magnetic core. Control is realized only by changes in the unidirectional component of the magnetic field strength. Such changes move the magnetic core of the MCR into saturation. The period in which the core is saturated is finally the principal parameter of the control.
The MCRâ„¢s consumed power is regulated within 0.01 to 1.00 of its rated power. For different types of MCR, short-term 40% overloading during periods of up to 20 minutes is allowed. Long term 20% overloading is allowed without time limitations.
2. General schematic of an MCR
1. Reactor phases
2. Thyristor converter with matching transformer
3. Control and safety system
4. CT is current transformer
5. VT is voltage transformer
6. U is network voltage
7. X is load
3.2. Whatâ„¢s the bottom line
Results shows that there is extreme reliability and considerable cost and energy savings with MCRs. Todayâ„¢s energy and energy policies positively demand MCR technology. A pilot installation of an MCR in the US would show that it this technology is the most reliable, direct, efficient, and simple path to enhanced transmission capability and to significant savings in both power and cost.
References
1. Bulk Transmission System Loss Analysis: EPRI Reports EL-6814-V1 & EL-
6814- V2,1990.
2 .A.M. Bryantsev, M.D. Galperin, G.A. Evdokunin, A.G. Dolgopolov,
Magnetically Controlled Reactor Shrinks Power Quality Costs: Official
Proceedings of the Thirteenth International Power Quality 2000 Conference
and Exhibit, Boston, 2000: Adams/Intertec, Ventura, CA (2000), pp. 810-
816.
3. G.N. Alexandrov, C.P.R. Gabaglia, Iu.A. Gerasimov, P.C.V. Esmeraldo, G.N. Evdokunin: A Proposed Design For The New Furnas 500 kV Transmission Lines” The High Surge Impedance Loading Line. Paper PE-288-PWRD-0-11- 1996, IEEE Transactions on Power Delivery, PWRD, Jan/ Feb, vol.14, N1, 1997, p. 278-286.
4. Luiz A.S. Pilotto, High Surge Impedance Loading Lines” Hsil In The Presentation Enhancement Of Transmission Capability. Paper delivered at the NSF/EPRI Workshop on Urgent Opportunities for Transmission System Enhancement, Palo Alto, October 2001.
5. G.N. Alexandrov, G.N. Evdokunin, A.A. Ragozin, Yu.G. Seleznev: Provision Of Parallel Operations Of Power Systems Connected By Extra-Long AC Transmission Lines With Controlled Shunt Reactors. Proceedings of the Fourth International Symposium on the World Energy System, Budapest, Hungary, October 1994, Budapest, Perspectives in Energy,1994-1995,vol.3,p341-345.
6. G.A.Evdokunin, A.A. Ragozin: Steady-State Stability Modes Analysis For Long Distance Transmission Lines With Controlled Shunt Reactors. Electrichestvo, 8,1996, p. 2-10.
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.doc   Magnetically Controlled Reactors Enhance Transmission Capability & Save Energy mcr.doc (Size: 1.14 MB / Downloads: 99)


A SEMINAR REPORT ON Magnetically Controlled Reactors Enhance Transmission Capability & Save Energy


Presented BY
P.vinay Kumar 06M21A0257
Department of Electrical And Electronics Engineering
LORDS INSTITUTE OF ENGINEERING AND TECHNOLOGY
Sy.no.32, Himayathsagar, Hyderabad-500008

ABSTRACT
The reactive power problem will become intensified in the future with the increasing use of EHV overhead lines and high-voltage cable in densely populated areas. Generators alone, with their under excited
limitations during light load periods, may not have sufficient capability to control voltages in some systems in which substantial amounts of high-voltage cable are used. Turbine generators with automatic voltage regulators, however, can be operated successfully in the under excited region to minimize the problem of excessive system capacitive reactive loading.
Although shunt reactors are an effective solution, economics may suggest other methods. Nevertheless, shunt reactors are helpful in controlling voltage during a system start-up.
The proposed technique is to have a glance at the magnetically controlled Reactors. These magnetically controlled reactors (MCRs) are proving to be more efficient and reliable and more cost effective than other reactive power control devices. Magnetically Controlled Reactors Enhance Transmission Capability & Save Energy. Especially in Compact Increased Surge-Impedance-Loading Power Lines
Contents
1 .Introduction:
2. Magnetically Controlled Reactor
2.1 MCRs are based on two original principles:
2.2 Basic Electrical circuit Of Control
2.3 Photographs of shunt MCRs for high-voltage grids
2.4 Single-line connection of three-phase 180 MVA, 500 kV shunt MCR:
2.5 Smooth regulation of single-phase MCR-60/500 phase current and phase
Voltage behavior over time
2.5.1 Total Cost of Ownership (TCO):
2.5.2 Mean Time Between Failure (MTBF):
3. Three-Phase Magnetically Controlled Reactors (MCRs):
4 Single-Phase MCR as Automatic Ground-Fault Neutralizer (Patented):
4.1 Application Field And Purpose:
4.2 Complete Equipment
4.3 Main Technical Data
4 .4 AUTOMATIC ADJUSTMENT & CONTROL SYSTEM
4.5 Efficiency of Use
4.6 Total Cost Ownership (TCO)
4.7 MEAN TIME BETWEEN FAILURE (MTBF)
5. Benefits of Controllable Reactors:
6. A New Type of Controlled Reactor
6.1. Advantages of the MCR
7. Practical approach of MCRs
7.1. MCRs and Compact High Surge-Impedance-Loading Power Lines
8. Transparencies:
8.1. Transparency 1
8.2. Transparency 2:
8.3. Whatâ„¢s the bottom line
9. MCR-25/110: Three-Phase MCR System (Patented) :
9.1 FIELD OF APPLICATION:
9.2 COMPLETE EQUIPMENT
9.3 MAIN TECHNICAL DATA
9.4 WINDING CONNECTIONS
9.5 OPERATING CONDITIONS
9.6 PRINCIPLES OF OPERATION
9.7 EFFICIENCY OF APPLICATION
9.8 TOTAL COST OF OWNERSHIP (TCO)
9.9 MEAN TIME BETWEEN FAILURE (MTBF)
10. CONCLUSION

1. Introduction:
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.
2. Magnetically Controlled Reactor:
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.
2.1 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.
Fig.1
2.2 Basic Electrical circuit Of Controllable Circuit:
6 to 35 kV arc quenching reactor:
3 to 35 kV Shunt Reactor for power-supply facility
:
Shunt Reactor for 110 to 500 kV grid
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.
Figure 2.
2.3 Photographs of shunt MCRs for high-voltage grids
Fig. 2a.
There Phase 25MVA, 110 kV Reactor
Fig.2b:
60MVA,500KV Single phase of MCR 180/500 3- Phase Controllable Reactor
Five of the most important of these companiesÃ… REZE, Zaporozhtransformator (Ukraine), the All-Russia Electrical Engineering Institute ("VEI"), the VEI Scientific & Engineering Center of Togliatti, and Elektrocenter (Russia)Ã… 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 reactorÃ… the MCR 25/110, produced for a high-voltage 110-kV distribution gridÃ… 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.
Figure 3.
2.4 Single-line connection of three-phase 180 MVA, 500 kV shunt MCR:

1. Three-phase group of single-phase 60 MVA, 500 kV MCRs;
2. Three 2.4 MW, 10 kV three-phase transformers with built-in thyristor converters 1 kV, 2 kA;
3. Control, safety, and automation system for MCR-180/500;
4. Voltage transformer;
5. Current transformer;
6. Circuit breaker, 500 kV;
7. Vacuum Breaker, 35 kV.
The MCR-180/500 controllable shunt reactor for extra high-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.
Figure 4.
2.5 Smooth regulation of single-phase MCR-60/500 phase current and phase voltage behavior over time
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 extra high-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.
2.5.1 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.
2.5.2 Mean Time between Failures (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.
3. Three-Phase Magnetically Controlled Reactors (MCRs):
List of Available Reactors
Product No. Phases Mvar kV
MCR 0.1/6 1 0.1 6
MCR 0.1/10 1 0.1 10
MCR 1.5/6 3 1.5 6
MCR 1.5/10 3 1.5 10
MCR 2/6 3 2 6
MCR 2/10 3 2 10
MCR 25/10 3 25 10
MCR 25/35 3 25 35
MCR 25/110 3 25 110
MCR 100/10 3 100 10
MCR 100/20 3 100 20
MCR 100/35 3 100 35
MCR 100/220 3 100 220
MCR 180/20 3 180 20
MCR 180/35 3 180 35
MCR 180/330 3 180 330
MCR 180/500 3 180 500
4 Single-Phase MCR as Automatic Ground-Fault Neutralizer (Patented):
4.1 APPLICATION FIELD AND PURPOSE:
Neutralizes automatic ground-fault capacitive current in electrical networks with isolated neutral.
Prevents transition of single-phase ground faults to multi-phase short circuits.
4.2 COMPLETE EQUIPMENT:
As shown in the diagram below, Electric reactor (2) with built-in thyristor converter, controlled by self-magnetization“ 1 unit;
¢ System for ground fault capacitive current measurement and for automatic adjustment of reactor current (1) “ 1 unit.
¢ Overvoltage limiter (5)“ 1 unit.
¢ Optional 3-phase network connection filter (4)“ 1 unit.
¢ Optional grounding transformer and voltage transformer (3)“ 1 unit.
PRINCIPLES OF OPERATION:
In the figure shown, an automatic adjustment and control system (1) defines the expected value of ground fault capacitive current and sends a control signal to the single-phase MCR converter (2), thus providing reactor control.
When a ground fault occurs, the reactor reduces the resulting current value at the damage point to a negligible value. The reactor switches to compensation mode without requiring intervention by maintenance personnel. The adjustment process is fully automatic.
Under normal operating conditions, the single-phase MCR is not saturated, eliminating resonance over voltages in the neutral line.
This reactor may also be used in 3-phase electric grids and consumers. In this case, a filter (4) for connection of the reactor to the 3-phase network is supplied with the reactor.
4.3 MAIN TECHNICAL DATA:
Rated power: 190 kVA 300 kVA 480 kVA 840 kVA
Rated voltage: 11/ 3 kV;
6.6/ 3 kV
11/ 3 kV;
6.6/ 3 kV
11/ 3 kV;
6.6/ 3 kV
11/ 3 kV Frequency: 50(60) Hz 50(60) Hz 50(60) Hz 50(60) Hz
Compensation current control range (continuous mode): 2.5 to 25,
4.25 to 42.5 4.0 to 40,
6.6 to 60 6.3 to 63,
10.5 to 105 11 to 105
2 hour compensation mode current: 30 A
50 A 48 A
80 A 76 A
126 A 132 A
Residual current, phase-to-ground short circuit: 2.0 A
2.75 A 2.75 A
3.5 A 3.5 A
5.0 A 5.0 A
Dimensions: 1030x1165
x1690 mm 1100x1235
x1710 mm 1130x1410
x1750 mm 1160x1980
x1950 mm
Weight: 1200 kg 1750 kg 2000 kg 3500 kg
Oil weight: 250 kg 350 kg 450 kg 1000 kg
Special orders: Any power up to 2.5 MVA,
Any voltage up to 35 kV.
4.5 AUTOMATIC ADJUSTMENT & CONTROL SYSTEM
Supply voltage: 220 V
Frequency: 50(60) Hz
Consumed power: 300 W
Signal memory time: 20 hrs
Weight: 3.2 kg
Dimensions: 260x270x160 mm
4.6 EFFICIENCY OF USE
Use of the single-phase MCR results in reduction of ground faults by a factor of three and their full containment in over voltage-caused insulation breakdown.
This device provides intact operation and increased lifetime of electric equipment.
Average cost recovery has been achieved in about 2.5 years.
4.7 TOTAL COST OF OWNERSHIP (TCO)
As a percentage of ex-works price TCO 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.
4.8 MEAN TIME BETWEEN FAILURE (MTBF)
CERC guarantees its MCR's 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 MCR's is 5 years.
5. Benefits of Controllable Reactors:
AC distribution grids usually do not require shunt reactors, but do require capacitor banks (i.e. capacitive shunt compensation). These capacitor banks need to be controlled because of changing load conditions. Yet the manual or thyristor switching operations typically used for capacitor bank control are not really efficient and wear out both switching equipment and power transformers. And they do not actually meet reactive power load and voltage control requirements efficiently, since the step control they provide does not really fit the load smoothly.
Intrinsic line capacitance in long AC grids of 400 kV or higher must be compensated to decrease reactive load losses, which can quickly become unacceptably large because they are proportional to the square of line voltage. Compensation must also ease the Ferranti effect under dynamic load conditions. Usually this is accomplished with shunt reactors, and some of these need to be controlled as well. In 500 kV grids the optimum ratio of controllable to non-controllable shunt reactors in a power transmission grid is about 1:3, in order to dampen all significant voltage surges and to improve power stability limits. With compensation at this level, higher voltage can be transmitted even through extended power lines. This also saves energy. In extreme cases, power transmission losses can be decreased by about 30% in this way. In US grids, where power transmission loss is about 4%, power transmission savings would be 1 to 2 percent.
Flexible control of reactive power and voltage in both lower and higher voltage grids is usually realized by static var compensators (SVCs) or more sophisticated static synchronous compensators (STATCOMs), or by controllable reactors apart from SVCs.
SVCs employ controllable reactors along with capacitor banks to control reactive power load, to dampen voltage surges and to decrease power transmission loss by decreasing reactive current circulation. STATCOMs do not use controllable reactors, but thyristors only. But when controllable shunt reactors are used, whether by themselves or within SVCs, the most common are thyristorcontrolled reactors (TCRs).
6. A New Type of Controlled Reactor
Another type of shunt reactor, however, whose principle of operation is extremely high saturation of the magnetic core. These magnetically controlled reactors (MCRs) are proving to be more efficient and reliable and more cost effective than other reactive power control devices.
As is well known, TCRs require a high-rated thyristor system, and this is the main cause of their unreliability. Magnetic reactor control is based on low-power magnetic biasing, and does not require such high-rated thyristors. Further inefficiencies are eliminated by the fact that, for the same reason, MCRs also do not require step-down transformers to decrease grid voltage to rated thyristor voltage, which must be less than 35 kV.
6.1. Advantages of the MCR
¢ MCRs are as reliable and simple to operate and maintain as ordinary transformers. TCRs, on the other hand, require special handling, specialized personnel, and more electrical filters.
¢ In more than 20 years™ field operation of what is now 40 installations, no MCR has ever needed replacement, because their closed, compensated magnetic systems do not suffer mechanical damage under dynamic regimes. The typical lifetime of a TCR is about 10 years because their open, non-compensated magnetic system suffers such damage.
¢ MCRs can sustain 50% overload for 20 minutes and 100% overload for 20 seconds. Compare TCRs, which can sustain 50% overload for 20 seconds and 100% overload for 3 seconds.
¢ The overvoltage limitation of an MCR is 2.3 times rated voltage. By contrast, TCRs have an overvoltage limitation of 1.8 times rated voltage.
¢ The current-distortion coefficient of the MCR, without filters, is less than 3%. With TCRs, the same coefficient is 5.8%. Thus, fewer filters are required with MCRs.
¢ MCRs require no specialized (chemical) operation and maintenance substation personnel to oversee the thyristor cooling system. TCRs, on the other hand, do require such workers because a sophisticated water cooling system is required.
¢ MCRs require about 10 sq. ft / Mvar of the substation open space. TCRs require about 100 sq. ft / Mvar.
¢ MCRs have a low external magnetic field because of the closed magnetic circuit of the reactor phases, and require no electromagnetic shielding. TCRs require significant shielding because of their open magnetic circuit of the reactor phases.
¢ MCRs experience about half the internal power loss of TCRs: 0.05% kW per kvar of rated reactive power (rkvar) in standby no-load mode, and 0.5% kW per rkvar in rated reactive power load mode. TCRs are about double this.
¢ MCRs can be designed to respond like TCRs, in as little as 0.02 second. But the price of an MCR is related to response time and thus, although MCRs of the shortest response time would cost about the same as equivalent TCRs” approximately $20/kvar” for more typical grid requirements of 1 second, they cost only half as much as TCRs, or about $10-11/kvar (ex works price).
¢ MCRs cost half as much as TCRs to install, operate, and maintain.
¢ More important than this cost differential, though, is the sheer reliability of this new technology.
7. Practical approach of MCRs:
In Russia, at Permenergoâ„¢s 80 MVA Kudymkar substation, which was equipped with capacitor banks, power fluctuations required over 800 manual switching events per year, serious capital outlay for labor, and rapid depreciation of attached switching and transformer equipment. An MCR was installed in 1999. The system immediately stabilized, and only twelve manual switching events have been necessary per year since then. The substation saved 7.3 GW-hours over the first year, and construction of a new power line, which had been planned, has become unnecessary for at least 10 more years. The utility has saved well in excess of $25M and in just two short years, has all but recovered the cost of installing the MCR.
7.1. MCRs and Compact High Surge-Impedance-Loading Power Lines
One important application of MCRs is their use with compact high surge-impedance-loading (HSIL) power lines. Transmission capability in AC overhead lines is limited by inductive impedance. Inductive impedance can be compensated with series capacitors, but such compensation is costly and creates difficulties for system operation. Lowering the inductive impedance in HSIL long distance transmission lines decreases the power angle between the line terminals and improves steady state stability limits without series capacitive compensation. When the power load becomes lower than the surge-impedance loading of the line, long-line reactive power and voltage can most efficiently be managed by means of controllable electric shunt reactors, 6] of which the most reliable, cost effective and energy-saving type is the MCR.
8.Transparencies :

1. Steep dependence of differential magnetic permeability of MCR core on
magnetic field strength facilitates very effective control of MCR inductance.
2. Principles of operation, schematic of a shunt MCR, and example of
transient process in an MCR.
3. General schematics of 6-35 kV Arc-Quenching MCRs, MCRs for
Distribution substations, and MCRs for 100-500 kV grids.
4. Field experience with MCR-based SVC: 32c/25i Mvar, 110 kV at
Kudymkar Substation in Northeastern European Russia (PermEnergo).
5. Magnetically Controlled Reactor MCR 25/110, 3-Phase, 110kV,
25MVA.
6. Arc-Quenching Magnetically Controlled Reactor (AQMCR) 190 kvar,
11/33 kV.
8.1. Transparency 1:
Steep dependence of differential magnetic permeability of MCR core on magnetic field strength facilitates very effective control of MCR inductance. In any transformer steel, magnetic-flux density B in teslas (T) is quasi-piecewise-linear dependent on magnetic field strength H, in amperes per meter (A/m). The differential magnetic permeability of the MCR core steel is very steeply dependent on H” µ (H) = B (H) / dH.
An increase of H from 5 A/m to 25 kA/m results in a decrease of µ of about 10,000 times to the constant value µ0, (permeability of vacuum). µ does not change at higher values of H (saturation).
This facilitates very effective control of MCR inductance. Increasing direct current in the MCR control winding increases H. This increase of H decreases µ as described above. Decreasing µdecreases MCR inductance. Decrease of MCR inductance decreases shunt MCR reactance, and decreasing reactance increases the reactive power consumed by shunt MCR. Thus current in the MCR control winding switches the MCR on and off.
8.2.Transparency 2:
Principles of operation, schematic, and example of transient process in an MCR.
1. Principles of Operation
Changes of inductance in magnetically controlled reactors (MCRs) are achieved through controlled changes of magnetic field strength in the magnetic core. Control is realized only by changes in the unidirectional component of the magnetic field strength. Such changes move the magnetic core of the MCR into saturation. The period in which the core is saturated is finally the principal parameter of the control.
The MCRâ„¢s consumed power is regulated within 0.01 to 1.00 of its rated power. For different types of MCR, short-term 40% overloading during periods of up to 20 minutes is allowed. Long term 20% overloading is allowed without time limitations.
2. General schematic of an MCR
1. Reactor phases
2. Thyristor converter with matching transformer
3. Control and safety system
4. CT is current transformer
5. VT is voltage transformer
6. U is network voltage
7. X is load
8.3. Whatâ„¢s the bottom line
Results shows that there is extreme reliability and considerable cost and energy savings with MCRs. Todayâ„¢s energy and energy policies positively demand MCR technology. A pilot installation of an MCR in the US would show that it this technology is the most reliable, direct, efficient, and simple path to enhanced transmission capability and to significant savings in both power and cost.
9. MCR-25/110: Three-Phase MCR System (Patented) :
9.1 FIELD OF APPLICATION:
MCRs of this type are used in electric distribution networks of 6, 10, 35, and 110 kV rating. Connected to busbars of 110 kV substations with circuit breaker and disconnect or Purpose.
To prevent emergency network over-voltage and keep it within 1.0 ú 2.5 percent of rated network voltage at point of connection.
To lower by 15 ú 20 percent power transmission and distribution losses due to minimization of reactive power transfer through the network.
To reduce by dozens of times the intensity of operating the switching equipment in voltage control circuits.
9.2 COMPLETE EQUIPMENT
As shown in the schematic diagram below the MCR 25/110 consists of the following parts:
¢ Electromagnetic portion (1), placed in a tank.
¢ A 160kW/10kV transformer with built-in thyristor 120V/800A AC/DC converter.
¢ MCR 25/110 control, regulation and protection system (3).
9.3 MAIN TECHNICAL DATA
Rated power 25 MVA
Number of phases: 3
Frequency: 50 or 60 Hz
Rated voltage of network winding: 127” kV
Supply voltage of converter: 0.4; 6; 10” kV
Supply voltage of control system: 220 V
Power change range: .25 to 25”MVA
Voltage setting range: 105 to 125 kV”
Current setting range: 1.0 to 114 A
No load losses: 40”kW
Short circuit losses: 200 kW”
9.4 WINDING CONNECTIONS
Phases of network winding of MCR 25/110 reactor are Y-connected and grounded.
MCR 25/110 control windings of phases are delta-connected.
Transformers with built-in thyristor converters are connected to equipotential points of reactor control windings.
MCR 25/110 control systems are connected to control inputs of transformers with built-in thyristor converters, to current transformers (5) at the MCR phases, and to substation voltage transformers (4) at 110 kV busbars.
9.5 OPERATING CONDITIONS
These MCRs are designed for outdoor operation in moderate climate with elevation up to 1000 m above sea level. Each module is placed in an oil-immersion tank with natural cooling. The main parameters of the module are as follows:
Active materials weight: 27 T
Transport weight: 60 T
Tank dimensions: 5765 x 6260 x 5170 mm
The associated transformer with built-in thyristor converter is also designed for outdoor operation. It is placed in an oil-immersion tank for natural cooling.
Main active material weight: 780 kg
Transport weight: 1500 kg
Tank dimensions: 1300 x 990 x 1760 mm
Control, adjustment, and monitoring system for indoor installation on a substation switchboard panel:
Weight: 15 kg
Dimensions: 250 x 450 x 250 mm
9.6 PRINCIPLES OF OPERATION
As shown in the figure above, voltage stabilization at a 110 kV substation is performed in automatic mode by a smooth change of the consumed power of reactor (1) in accordance with a mismatch signal generated by control system (3). The consumed current of reactor (1) is changed as result of direct current produced by a thyristor converter (2) magnetizing its magnetic system.
When the voltage increases to 2.5% above the given pre-set value, the consumed power of reactor (1) is smoothly changed within the range of 0.25 to 25 MVA with an equivalent time constant not exceeding 1 second.
Compensation of excess charge power of transmission lines is carried out automatically according to the pre-set, operator-fixed value of converter (2)'s saturation angle adjustment. The MCR's idle current can be preset from 2.5 to 114 A.
9.7 EFFICIENCY OF APPLICATION
Design, weight, dimension, and maintenance of the MCR 25/110 are similar to general-purpose, two-winding power transformers of the same power and voltage class. This results in device effectiveness and reliability of operation.
Operation of the MCR 25/110 does not require specific training of maintenance personnel.
Time of recovery of outlay for MCR 25/110 is 1.5-2 years.
9.8 TOTAL COST OF OWNERSHIP (TCO)
As a percentage of ex-works price TCO 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.
9.9 MEAN TIME BETWEEN FAILURE (MTBF)
CERC guarantees its MCR's 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 MCR's is 5 years.
10. CONCLUSION:
MCRs are as reliable and simple to operate and maintain as ordinary transformers. TCRs, on the other hand, require special handling, specialized personnel, and more electrical filters. AC distribution grids usually do not require shunt reactors, but do require capacitor banks (i.e. capacitive shunt compensation). These capacitor banks need to be controlled because of changing load conditions. Yet the manual or thyristor switching operations typically used for capacitor bank control are not really efficient and wear out both switching equipment and power transformers. And they do not actually meet reactive power load and voltage control requirements efficiently, since the step control they provide does not really fit the load smoothly.
References
1. Bulk Transmission System Loss Analysis: EPRI Reports EL-6814-V1 & EL-
6814- V2,1990.
2 .A.M. Bryantsev, M.D. Galperin, G.A. Evdokunin, A.G. Dolgopolov,
Magnetically Controlled Reactor Shrinks Power Quality Costs: Official
Proceedings of the Thirteenth International Power Quality 2000 Conference
and Exhibit, Boston, 2000: Adams/Intertec, Ventura, CA (2000), pp. 810-
816.
3. G.N. Alexandrov, C.P.R. Gabaglia, Iu.A. Gerasimov, P.C.V. Esmeraldo, G.N. Evdokunin: A Proposed Design For The New Furnas 500 kV Transmission Lines” The High Surge Impedance Loading Line. Paper PE-288-PWRD-0-11- 1996, IEEE Transactions on Power Delivery, PWRD, Jan/ Feb, vol.14, N1, 1997, p. 278-286.
4. Luiz A.S. Pilotto, High Surge Impedance Loading Lines” Hsil In The Presentation Enhancement Of Transmission Capability. Paper delivered at the NSF/EPRI Workshop on Urgent Opportunities for Transmission System Enhancement, Palo Alto, October 2001.
5. G.N. Alexandrov, G.N. Evdokunin, A.A. Ragozin, Yu.G. Seleznev: Provision Of Parallel Operations Of Power Systems Connected By Extra-Long AC Transmission Lines With Controlled Shunt Reactors. Proceedings of the Fourth International Symposium on the World Energy System, Budapest, Hungary, October 1994, Budapest, Perspectives in Energy,1994-1995,vol.3,p341-345.
6. G.A.Evdokunin, A.A. Ragozin: Steady-State Stability Modes Analysis For Long Distance Transmission Lines With Controlled Shunt Reactors. Electrichestvo, 8,1996, p. 2-10.
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