Reprint From Mining Engineering January 2015 Vol 67 No -Books Download

Reprint from Mining Engineering January 2015 Vol 67 No
03 Dec 2019 | 57 views | 0 downloads | 12 Pages | 1.04 MB

Share Pdf : Reprint From Mining Engineering January 2015 Vol 67 No

Download and Preview : Reprint From Mining Engineering January 2015 Vol 67 No

Report CopyRight/DMCA Form For : Reprint From Mining Engineering January 2015 Vol 67 No


Technical Papers,Impact of using,synchronous condensers for power system. stability and improvement of short circuit,power in mining projects. by M Nambiar and Z Konstantinovic, abstract Due to the remote locations of mining projects and the need for long transmission. lines to provide electrical power mining sites often operate with poor network power quality. and low short circuit capacity To cope with this situation more and more mining operators. are considering the installation of appropriately designed synchronous condensers together. with power factor correction and harmonic filter systems PFC HFS The installation of such. power quality equipment is viewed as a technological advancement in the mining application. an adequate level of short circuit power is essential and has to be ensured for the safe and. reliable operation of especially large cycloconverter driven gearless mill drive systems GMDs. used for grinding This paper explores the impact technical advantage and reasoning for the. selection of this advanced hybrid technology to cope with the power system challenges of. future mining projects It also delves into the potential problems and how to address them. Mining Engineering 2015 Vol 67 no 1 pp 38 44, Official publication of the Society for Mining Metallurgy Exploration Inc. Introduction Effective filtering of harmonics depressed and there is no help or. To ensure the efficient utilization of being produced within the remedy in this regard In contrast to. electrical power for mining operations plant and imported from this a sudden voltage rise due to the. power factor correction and harmonic the supplying high voltage trip of a big load within or outside the. filter systems have become unavoidable network In this way PFC plant can be reduced by a synchronous. electrical subsystems due to their two HFSs protect expensive and condenser A properly designed. major advantages critical plant equipment and synchronous condenser with the. other consumers of electrical support of optimized control logic for. Improvement of the plant power energy supplied by the same the synchronous condenser and PFC. factor by limiting the amount grid HFS can prevent further load trips due. of reactive power supplied by to overvoltage, the utility thereby eliminating Plant operation becomes critical A mining plant typically has.
the payment of penalties to the when a weak network has to supply a a significant amount of electrical. utility and any associated costs big plant where significant harmonic equipment with varying functions. As a result significant cost generating loads are installed In such reacting differently in overvoltage. savings can be achieved cases synchronous condensers could be situations However there are process. a promising solution critical loads that should be kept. M Nambiar and Z Konstantinovic in operation to ensure the whole. are engineering manager and Importance of maintaining plant production operation is not interrupted. senior engineer respectively at voltage An important example of such a critical. ABB Switzerland Zurich The most critical events associated load process is the SAG and ball mills. Switzerland Paper number with voltage level are a short circuit in in the grinding area SAG and ball mills. TP 13 060 Original manuscript the plant causing a voltage collapse driven by cycloconverters have two. submitted November 2013 and a sudden trip of big plant loads overvoltage protection levels that have. Revised manuscript accepted for causing a voltage rise to be generally observed as part of the. publication August 2014 The only supportive action in protection concept For overvoltages. Discussion of this peer reviewed the case of a short circuit is a rapid between 112 and 115 of the. and approved paper is invited disconnection of the plant area where nominal voltage a cycloconverter will. and must be submitted to SME the short circuit occurred However be tripped after 250 milliseconds and. Publications by April 30 2015 until a successful disconnection is for overvoltages above 115 the trip. managed the voltage stays fully will be instantaneous. 38 January 2015 M n ng eng neer ng www miningengineeringmagazine com. Reprint from Mining Engineering January 2015 Vol 67 No 1 Synchronous condensers in mining projects 3. Technical Papers,The primary goal is to not let voltage Figure 1. rise above 115 at any time It is obvious, that the bus voltage level prior to the trip Synchronous condenser current after a short circuit occurs. of a large load will influence the voltage,level after the trip The voltage rise itself. is dictated by the tripping load and the,strength of the supplying network The. absolute value of bus voltage after the,load trip will be.
voltage after trip voltage before trip,voltage rise due to load disconnection. It is noticed that weak networks and,big loads both typical of mining plants. will often result in voltages far above,115 after a load trip This would lead. to the tripping of all other mills driven by,cycloconverters and most probably the. further cascade tripping of other electrical,equipment throughout the plant.
Advantages of using synchronous, condensers In contrast to some other equipment a synchronous. A synchronous condenser is essentially a common condenser does not cause any transients or notching. synchronous motor that runs idle without any connected on the grid Becker 1992 during operation. load at the drive end ABB 2013 Like a generator it can be A synchronous condenser does not produce any. over excited or under excited by varying its field current By notable harmonics Kubota et al 1972 and can. varying the excitation the magnitude of the internal voltage partly absorb harmonics without amplifying any of. source will change Using a synchronous condenser has a them. number of advantages In contrast to capacitors and passive harmonic. filters a synchronous condenser does not cause any. By changing the excitation of the synchronous additional parallel resonance with the supplying. condenser stepless export and import of reactive network. power are possible capacitive and inductive power A synchronous condenser decreases effective. By varying the amount and direction import export network impedance which moves all existing parallel. of reactive power a synchronous condenser provides resonances toward higher frequencies This unique. a stepless and effective control of bus voltage that is feature is often the triggering point influencing the. much faster and finer than with a classical on load decision to install synchronous condensers as there. tap changer OLTC or the switching of a PFC is mostly no other economical means to move the. HFS In contrast to various static equipment for lower frequency parallel resonance away from line. voltage stabilization equipment without moving frequency Parallel resonance which is close to. parts a synchronous condenser can provide line frequency may cause serious problems for the. substantial support with its considerable short stability of the electrical supply for loads driven by. overload capability 150 or even more of its rated rotating machines and for turbine generators shaft. current and for longer with its fully rated capacity blades Moharana 2012 This risk is elevated in. export of reactive power even under serious low plants where in addition to common harmonics the. voltage conditions Equipment such as static var so called inter harmonics are present as well for. compensators SVCs or PFC HFSs lose a lot of example where cycloconverters are used to run the. their capability to deliver reactive power power SAG and ball mills. is proportional to the square of line voltage just. under the critical condition of low voltage when the Some concerns regarding the use of synchronous. maximum possible support is desperately needed by condensers. the network system Teshmont 2005 Teleke et al In spite of their many advantageous features not all. 2008 mining plants have synchronous condensers why As is. A synchronous condenser supports the supply often the case the main reason is cost Aside from capital. network during transient voltage excursions by investment in the synchronous condenser itself there are. reacting within milliseconds with countermeasures maintenance costs and costs related to thermal losses. to the voltage changes by delivering capacitive Maintenance is basically the same as for other large motors. power as voltage drops or delivering inductive in the plant Synchronous condenser losses are generally. power as voltage rise about 1 3 of the rated power Peterson 1993 Power System. www miningengineeringmagazine com M n ng eng neer ng january 2015 39. 4 Synchronous condensers in mining projects Reprint from Mining Engineering January 2015 Vol 67 No 1. Technical Papers, Operation 2012 Being mostly operated at no load realistic the proper operational coordination of big loads the. losses can be estimated at 1 3 1 5 of rated synchronous PFC HFS and the synchronous condenser. condenser power Reduction of switching actions of PFC HFS This. can be achieved by smart control and coordination, The increased short circuit power due to the between the control systems of the PFC HFS and. installation of a synchronous condenser may require the synchronous condenser. additional measures to ensure that the bus system, and the associated switchgears are rated to withstand Maintaining plant voltage within limits and avoiding. the increased short circuit current load trips, A short circuit near the synchronous condenser With a synchronous condenser in operation a voltage.
could lead to the possible missing out of current rise due to a load trip will no longer be a sudden one step. zero crossing right after the short circuit has occurrence Instead it will be gradual reaching the final. occurred The circuit breaker can only break a fault value after several seconds The magnitude of the final value. current when the alternating current crosses the will be lower than what it would be without a synchronous. zero value A synchronous condenser fault current condenser in operation This is typical of synchronous. is composed of a DC offset and an AC symmetrical condensers as a voltage source with variable inner. component if the DC component is sufficiently impedance Teshmont 2005 It occurs when no external. large there will be a long delay before the current control of the synchronous condenser has been applied. crosses the zero value which could therefore lead to With control of the synchronous condenser excitation. a long delay before the circuit breaker can break the voltage the behavior will be modified to actively fulfill the. fault current see Fig 1 goals defined for the control system However the time. constant of the synchronous condenser system is relatively. The time constant of this decay of fault current is long from slightly less than one second to a few seconds. determined by the X R ratio at the fault location In the case compared with the time constant of an SVC or Statcom. of high X R ratio this decay can be extremely large up to system Therefore the synchronous condenser excitation. hundreds of milliseconds which could impose a significant control will not be very effective immediately after the load. problem for synchronous condenser circuit breakers and for trip and only the typical behavior without active control as. the equipment where the short circuit occurred Gallagher described above will determine the initial voltage rise at the. et al 2010 The worst case scenario is when a two phase connected bus. fault develops into a three phase fault while synchronous With the synchronous condenser in operation the final. condensers are operating in an under excited condition bus voltage after the load trip is mainly influenced by the. when the plant load condition is capacitive and there is following factors parameters. negligible resistance in the fault path, Short circuit power of the supplying network lower. Optimizing the utility of synchronous condensers short circuit power leads to higher voltage rise. Once the decision has been made to install one or Characteristics of the synchronous condenser like. more synchronous condensers in a plant the synchronous rated power and subtransient impedance higher. condenser should be fully integrated into the overall electrical rated power and or lower impedance leads to lower. system including its advanced control system in order to voltage rise. maximize its utilization and minimize its disadvantages and Characteristics of the intermediate transformer for. or risks the synchronous condenser like rated power and. Besides increased system short circuit power which short circuit impedance higher transformer power. may be the main criterion for the selection of synchronous and or lower impedance leads to lower voltage rise. condensers the following opportunities should be taken into Amount of capacitive power for the PFC HFS. consideration as well connected to the network during the event of a load. trip higher capacitive power connected leads to, Optimization of PFC HFS design to realize higher voltage rise. significant cost savings By carefully analyzing Rating of the load that is being disconnected from. different plant and network operating and critical the network higher capacity load trip leads to. scenarios it may be sufficient to have a smaller and higher voltage rise. or simpler PFC HFS through the smart usage of a Bus voltage prior to load trip lower bus voltage. synchronous condenser before leads to lower voltage after the trip. Transient support of plant voltage This can be Internal voltage of the synchronous condenser. ensured by choosing appropriate parameters for the lower internal voltage leads to lower voltage after. rated power overload characteristics impedances the trip. and time constants of the synchronous condenser, as well as for the rated power and short circuit From the above it is evident that not only the physical. impedance of the intermediate transformer if any characteristics of hardware supply network load. is needed for the synchronous condenser synchronous condenser intermediate transformer PFC. Smooth voltage control for special situations and HFS determine whether the tripping of one load will lead to. procedures like mill starting This can be realized by subsequent trips of further loads due to voltage rise but also. 40 January 2015 M n ng eng neer ng www miningengineeringmagazine com. Reprint from Mining Engineering January 2015 Vol 67 No 1 Synchronous condensers in mining projects 5. Technical Papers, Single line diagram of the mining project in South America with two synchronous condensers and PFC HFS installed. the control system logic The control system logic determines filter with 3 0 MVAr and 11th filter with 5 8 MVAr. how much capacitive power is to be connected in the plant Group D with total 5 8 MVAr capacitive power. and what bus voltage and internal synchronous condenser only 13th filter with 5 8 MVAr. voltage should be maintained during critical operations. The plant is designed to operate even with only one of. Example of synchronous condensers applied in a the two transformers feeding the complete load having the. large mineral processing plant with weak supply tiebreaker between two main busbars closed. network The simplified single line diagram in Fig 2 shows the. This example is based on an actual synchronous equipment together with the two synchronous condensers. condenser installation for power system improvements in that were introduced at a later stage after a detailed system. a mining project in South America The plant is located at analysis was done using the NEPLAN power system. the end of a long 220 kV 60 Hz overhead transmission line engineering tool The major problem identified was the. with minimum short circuit power of only 220 MVA feeding combination of a weak supply network and the large amount. a 120 MW approximately full load Two main transformers of capacitive power needed to keep the power factor of the. each 75 100 125 MVA with 9 impedance supply loads on plant at its targeted value of 0 95 lagging or higher Due to. two main 23kV busbars One SAG 18 MW and two ball these two physical determinants the existence of one strong. mills 2x15 MW are driven by cycloconverters In order to parallel resonance with frequency close to the line frequency. achieve the target power factor at 220 kV approximately 70 as low as 71 Hz was noticed during the power simulation. MVAr capacitive power is required This capacitive power calculations Together with strong inter harmonics from. has been split into two identical PFC HFSs connected to cycloconverters which may hit this parallel resonance it. each of the two main 23 kV busbars Each 35 MVAr PFC could result in the excitation of mechanical oscillations in. HFS is designed as a group of seven harmonic filter units rotating machines and driven equipment Camay 1983 If. tuned for different harmonic orders 2nd 3rd 4th 5th one of the rotating machines with a driven load has a natural. 7th 11th and 13th These seven harmonic filter units are resonant frequency at or near to 11 Hz 71 60 11 it can. switchable in four steps groups lead to problems and even mechanical damages Moreover if. the affected rotating machine is one of the generators within. Group A with total 11 6 MVAr capacitive power the supply network it can even lead to damage of the shaft. 2nd and 3rd filter each with 5 8 MVAr or turbine blades thus resulting in instability of the power. Group B with total 8 6 MVAr capacitive power 4th network The critical frequency range for electromechanical. filter with 2 8 MVAr and 5th filter with 5 8 MVAr oscillations in big rotating machines mostly range from 14. Group C with total 8 8 MVAr capacitive power 7th to 35 Hz Elfayoumy and Moran 2003 Tsai et al 2006. www miningengineeringmagazine com M n ng eng neer ng january 2015 41. 6 Synchronous condensers in mining projects Reprint from Mining Engineering January 2015 Vol 67 No 1. Technical Papers, Figure 3 above the black line harmonics and inter harmonics will be.
amplified The amplification ratio is given approximately by. Network impedance vs frequency seen from plant medium the ratio of impedance amplitudes red and black lines at. voltage busbar with no synchronous condenser in operation the given frequency. At the frequency of the highest peak 71 Hz the, amplification ratio is above 10 Physically this means that for. each 1 ampere current being produced by any of nonlinear. loads at 71 Hz more than 10 amperes will flow into the. network This leads to, High distortions of 23 kV voltage where some loads. driven by rotating machines may start to oscillate. High current flowing towards the supply network,where mechanical resonances in generators may be. At 60 Hz we see that the impedance with harmonic, filters red line is about three times higher than without. them black line Physically this means that with harmonic. filters in operation the voltage sensitivity of the network. to sudden load changes is about three times higher than. without any harmonic filters, Parallel resonances caused by the interplay of harmonic.
filters and network impedance can usually be flattened. down by the appropriate damping of filter units addition. of damping resistors thereby minimizing the risk of. amplification However this is not practically feasible in the. case of parallel resonances appearing at frequencies very. close to line frequency Hence filter damping is not a cure. for such low frequency parallel resonances There are other. but frequencies lower than 14 Hz or higher than 35 Hz have possible measures to overcome this but they involve higher. also been reported The frequency range of mechanical initial capital cost. oscillations of 14 35 Hz translates into a 74 95 Hz range for. the critical electrical parallel resonance of the 60 Hz supply Strengthen the supply network at the medium. system 64 85 Hz in the case of 50 Hz supply systems voltage level by adding generator units preferably. The mine operators are made aware in cases where the close to or even in the plant itself by having. parallel resonance with lowest frequency slips below 95 Hz additional high voltage overhead line s in parallel. 85 in 50 Hz networks In more serious cases of parallel with the existing one s by selecting high voltage. resonance with lowest frequency below 90 80 Hz it is medium voltage transformers with higher rated. recommended to introduce synchronous condensers power and or lower short circuit impedance. These measures often turn out to be either, Network impedance and parallel resonance The extremely expensive or not sufficiently effective or. following sections describe the results of a simulation study not feasible to be implemented at remote mining. conducted to verify the influence of synchronous condensers locations. on the power system network The study was conducted Introduce one or more synchronous condensers and. using the NEPLAN power system engineering software tool connect them to the main MV busbars in the plant. Figure 3 presents impedance versus frequency seen from This solution is very effective and more feasible. the 23 kV main busbars tied together red line The black. line represents the same network impedance but without Figure 4 shows the impedance chart for the same plant. harmonic filters and without any capacitances within or and conditions under discussion but operating with two. outside the plant In this case synchronous condensers are synchronous condensers each having 15 MVA rated power. not energized Comparing Figs 3 and 4 the most important observation. The following observations can be made from Fig 3 The is that the frequency of the lowest parallel resonance. maximums and minimums visible in the red line are mostly has increased from 71 to 95 Hz The amplitude of the. a result of the interplay of harmonic filters in the plant corresponding impedance peak is reduced by 30 from. and the impedance of the supply network Some of them 41 to 28 5 ohm and the possible voltage distortions caused. however come from the high voltage network itself All but by cycloconverter inter harmonics will also be reduced by. the one maximum close to the line frequency of 60 Hz are 30 The mechanical excitation frequency 95 60 35. below the black line meaning that for these frequencies Hz is now considerably higher It thus reduces the risk of. no amplification of harmonics produced by plant loads mechanical resonance in rotating machines like large motors. will occur However for frequencies where the red line is or generators. 42 January 2015 M n ng eng neer ng www miningengineeringmagazine com. Reprint from Mining Engineering January 2015 Vol 67 No 1 Synchronous condensers in mining projects 7. Technical Papers, Another important point is the change in impedance 115 during the first 250 milliseconds This time is mostly. value at 60 Hz comparing the red and green lines at 60 sufficient to allow the control system to disconnect some. Hz It is lowered from 9 5 ohm in Fig 3 to 2 2 ohm in Fig of the PFC HFS to significantly pull back the rising bus. 4 This means that the voltage sensitivity to sudden load voltage An intelligent control system would calculate and. changes is reduced by four times This is considered a great disconnect the required number of PFC HFS units to. improvement for normal operation of the plant achieve a stable operation of all plant loads. It is also important to realize that during the initial 250. Practical example of how the synchronous condensers milliseconds after the mill trip the synchronous condensers. control system helps to keep voltage within limits even in output cannot be effectively controlled by changing their. the most critical situation such as a sudden trip at a SAG excitation as the time constant involved in this process is too. mill during ramp up One of the most critical situations high Only their internal voltage source and their rising inner. associated with voltage variation in a mineral processing impedance subtransient impedance during first few tens of. plant is a SAG mill ramp up involving up to 150 of its rated milliseconds and the transient impedance thereafter will. power Although the ramp up will cause a considerable drop contribute to the reduction of voltage rise. of the bus voltage the mill acceleration process is gradual Figure 5 provides the results of voltage rise simulations. and takes several tens of seconds which allows for voltage during a mill trip with and without synchronous condensers. support either by synchronous condensers or by switching in in operation under the following plant operating conditions. a PFC HFS or both The OLTC of the main transformer. is usually too slow in its reactions and therefore will not Short circuit at 220 kV is minimal 220 MVA. contribute to voltage stabilization during the SAG mill Only one main transformer supplies both main 23. ramp up kV busbars, Adding more PFC HFS as shown earlier will virtually Before the SAG mill starts to ramp up two ball. lower the available short circuit power at the medium mills are already in operation and both synchronous. voltage bus with a consequence that bus voltage sensitivity condensers and one full PFC HFS of 35 MVAr are. will increase It means a mill trip with an energized PFC in operation as well. HFS will cause a bigger voltage rise than if no PFC HFS The control system regulates the synchronous. is in operation On the other hand running a mill or mills condensers to keep bus voltage at 92 of. without a PFC HFS would cause very high harmonic nominal voltage The controller of PFC HFS is. distortions of the bus voltage probably ending in disturbing able to calculate the number of filter units to be. or even destroying some electrical equipment in the plant disconnected in the case of a mill trip in order to. Therefore the strategy for a PFC HFS during the start up minimize consequent excursions of the bus voltage. of mills is to energize as much as necessary but as little as. possible Figure 4, The synchronous condensers should not attempt to Network impedance vs frequency seen from plant medium. maintain bus voltage close to their nominal values as the. voltage busbar with two 15 MVA synchronous condensers in. internal synchronous condenser voltage would be higher. than the bus voltage In the case of a sudden mill trip this operation. will only worsen the consequent rise of the bus voltage. Therefore during mill acceleration the controller of the. synchronous condensers shall gradually lower bus voltage. to a level that would still not cause any undervoltage trip. of other electrical equipment This means the synchronous. condensers have to maintain the bus voltage at about 92. of the nominal bus voltage The following are arguments to. maintain bus voltage at the lower limits during mill starting. Keeping the bus voltage low would provide more, usable safe space for upward voltage correction if.
the mill trips,When the synchronous condensers force the bus. voltage to stay low by drawing reactive power the,internal voltage of the synchronous condensers. remains low as well Low internal voltage will be, very helpful in the case of a mill trip to counteract. the rise in bus voltage during the trip,At lower bus voltage the cycloconverters consume. less reactive power and in the case of a sudden mill. trip it will result in a lesser rise of the bus voltage. The ultimate task for synchronous condensers after the. mill trip is to prevent the bus voltage from rising beyond. www miningengineeringmagazine com M n ng eng neer ng january 2015 43. 8 Synchronous condensers in mining projects Reprint from Mining Engineering January 2015 Vol 67 No 1. Technical Papers,Figure 5 steady state higher value.
The calculation in Fig 5 is made with synchronous, Voltage excursions caused by SAG mill and PFC system trip condensers acting only with their inherent nature. as voltage sources without any active regulation, through change in excitation This clearly shows how. efficient synchronous condensers are in reducing,rapid voltage changes even without any active. excitation control If excitation control is applied it. would be effective only after approximately 15 5 sec. Conclusion,In mining plants operating on weak networks and. where the parallel resonance of the PFC HFS with lowest. frequency comes too close to line frequency a synchronous. condenser is mostly the ideal solution Once adopted as a. solution for the parallel resonance problem the synchronous. condenser will continue to deliver collateral support and help. for a number of power system challenges that are typical for. mining plants However every mining plant should consider. an in depth professional power system analysis to evaluate. potential problems and determine the right power quality. References, ABB Synchronous Condensers for Voltage Support in AC Systems.
The simulation results shown in Fig 5 are based on a 2013 ABB Product Notes. mill trip after 15 seconds during mill ramp up operation The Becker K D May 1992 Correcting mill power factor with a. bus voltage is increased and stays high for 50 milliseconds synchronous condenser Tappi Journal p 92. until the filter groups B C and D determined by the PFC Canay I M December 1983 Subsynchrone Schwingungen und. HFS controller have tripped leading to a voltage drop The Resonanzen in elektrischen Maschienen unter Ber cksichtigung des Netzes. response curves are significantly different if synchronous und der mechanischen Welle Bulletin SEV VSE 74 Tabelle16 4 2 BBC. condensers are in operation red line or not blue line Aktiengeselschaft Brown Boveri Co Baden Switzerland p 1175. Elfayoumy M and Moran C G 2003 A comprehensive approach. Impact of synchronous condenser operation on voltage for sub synchronous resonance screening analysis using frequency scanning. excursions during a load trip From Fig 5 it can be seen technique IEEE Power Tech Conference Bologna Italy June 2003 pp 1 5. that the synchronous condensers have a major influence on Gallagher J McDonagh N and Phang W 2010 The effect of. voltage variation The impact is explained in detail as follows delayed zero crossings following a short circuit on system stability GCC. Power Conference Qatar 2010 pp 1 6, Without synchronous condensers in operation the Kubota T Takahashi M and Otsuka K 1972 Reducing voltage. voltage rise would be far above the level of 1 15 flicker of steel melting arc furnace by synchronous condenser Fuji Electric. pu which would lead to the tripping of all mills Review Vol 18 No 3. and consequently all plant loads With synchronous Moharana A K 2012 Subsynchronous Resonance in Wind Farms. condensers in operation the voltage stays Ph D Thesis Graduate Program in Engineering Science Department of. comfortably under 1 1 pu which is an acceptable Electrical and Computer Engineering The University of Western Ontario. limit for bus overvoltage and plant operation Canada. The initial voltage peak after the SAG mill has tripped Peterson T December 1993 Reactive Power Compensation ABB. is only about 0 14 pu with synchronous condensers Information Nr 500 028 E ABB Power Systems Sweden. 0 92 pu to a compared with approximately 0 35 Power System Operation Reactive Power Management A Resource. pu for the peak without synchronous condensers Handbook December 2012 Power System Operation Corporation Ltd. 0 92 pu to A which is two and a half times higher India NLDC POSOCO Chapter 9 13. Similarly the drop in voltage after the tripping of Teleke S Abdulahovic T Thiringer T and Svensson J July 2008. three filter groups is much smaller with synchronous Dynamic performance comparison of synchronous condenser and SVC. condensers in operation a to b than without IEEE Transactions on Power Delivery Vol 23 No 3. synchronous condensers A to B Teshmont Consultants Vermont Electric Power Company Granite. The red line sections a a and b b are the result Reactive Power Device January 2005 prepared by Teshmont Consultants. of synchronous condensers acting with their LP Report No 554 04 20000 1. subtransient reactance X The subtransient Tsai J I Zhan T S and Wu R C 2006 A random subsynchronous. reactance goes after approximately 50 milliseconds resonance in a turbine generator set IASTED International Conference. into transient reactance X which is higher than X Energy and Power System Chiang Mai Thailand March 2006 pp 144 147. In Fig 5 its influence is visible from b until a few. seconds beyond when the reactance finally goes into. 44 January 2015 M n ng eng neer ng www miningengineeringmagazine com. Reprint from Mining Engineering January 2015 Vol 67 No 1 Synchronous condensers in mining projects 9. Contact us, Global Competence and Execution Center for grinding solutions. Copyright 2015 ABB All rights reserved 3BH S814141 ZAB E01 03 15 250 K pfli Partner. ABB Switzerland Ltd,Segelhofstrasse 9P,5405 Baden 5 D ttwil. Switzerland,Phone 41 58 586 84 44,E mail minerals ch abb com. ABB s Mining business is represented in the following countries. Australia Brazil Canada Chile China Germany Peru,South Africa Sweden and Switzerland.
For contact details please visit our website,www abb com mining.

Related Books

Forts on the Minnesota Frontier

Forts on the Minnesota Frontier

role in the Dakota Indian War of 1862. Fort Abercrombie, 1857 ... Following a ten year absence, the Third US Infantry returned to Fort Snelling in 1921, and soon gave the post a reputation as the "country club of the Army." Sunday afternoons were filled with . 3 ceremonial parades, baseball, polo matches and recreated battles. It boasted a wild game sanctuary, golf course, tennis courts and ...

Who was Bill Graham? - Illinois Holocaust Museum and ...

Who was Bill Graham Illinois Holocaust Museum and

In Lyon, the International Red Cross Worker told Bill, who was then ten years old, that his sister had to stay behind in the hospital but would join them again once she recovered. Bill never saw Tolla again and she most likely died in the hospital. From Lyon, Bill and the other children walked to Marseilles. They all spent two months in a ...

Requirements of the 2000 International Building Code and ...

Requirements of the 2000 International Building Code and

2000 International Building Code and 2000 International Residential Code on Exterior Insulation and Finish Systems David A. Bowman, P.E. Steven R. Thorsell David Bowman is a managing engineer and Steven Thorsell is a supervising architect with the National Evaluation Service (NES).

Silvia Casari -

Silvia Casari anmar italia it

I mutamenti demografici ai quali stiamo assistendo nel Mondo Occidentale, ovvero il progressivo invecchiamento della popolazione, esercitano pro-

Allgemeine Informationen Regelarmaturen 5000-7010 General ...

Allgemeine Informationen Regelarmaturen 5000 7010 General

80 - 25 80 95 80 - 65 79 100 - 30 100 148 100 - 25 80 120 125 - 35 125 231 125 - 30 100 187 150 - 40 150 333 150 - 35 125 292 200 - 60 200 592 200 - 40 150 420 250 - 80/60* 250 926/847* 250 - 60 200 747 300 - 100 300 1333 300 - - - - 400 - auf Anfrage / on request / sur demande 400 - - - -

Fijian Education, The Community and the Teacher

Fijian Education The Community and the Teacher

Fijian Education, The Community and the Teacher ... In some Fijian junior secondary and secondary schools there ... out of touch with the aesthetic requirements of ...



Branded drugs are t ypically sold at a higher cost than generic drugs. 4 . A drug sold under a brand name and legally protected in the U.S. from being made, used or sold by other manufacturers for a specifc period of time. 5, 6 . BRANDED DRUG . BRANDED PATENT-PROTECTED DRUG BRANDED SPECIALTY DRUG . Prescription Drug Costs Trend Update ( 4 ) BLUE CROSS BLUE SHIELD, THE HEALTH OF AMERICA REPORT ...

Fijian Cup Tournament - Touch Tournament, Rugby ...

Fijian Cup Tournament Touch Tournament Rugby

Flights arrive into Nadi, Fiji Transfers to Sheraton Resort, Port Denarau Bula Buses to tournament brie?ng and welcome function for the Fijian Cup featuring multi ...

Gypsy and traveller caravan count, January 2020

Gypsy and traveller caravan count January 2020

Gypsy and traveller caravan count, January 2020 22 April 2020 SFR 27/2020 Main points On the 23rd January 2020 there were 1,092 Gypsy and Traveller caravans and 136 sites reported in Wales. Between the January 2019 and January 2020 counts, the total number of Gypsy and Traveller caravans has increased by 4% (42 caravans) and the total number of sites (both authorised and unauthorised) has ...



Tenaga kerja wanita sebagai sumber data penelitian. Segala hormat dan terima kasih secara khusus penulis ucapkan kepada Ayahanda M. Syafii Murad Daulay, SE, MSi dan ibunda tercinta Maslurah Darus yang telah membimbing, membesarkan, dan mendoakan serta adik M. Rezeki Maldini Murad Daulay. iv Teman-teman teristimewa (Siswadi Irwanto, Ary Munandar Hasibuan, Muhammad Syahrizal, Saidul Khudri ...