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اقتصاديات الكهرباء |
| NO.9 feb 2002 | العدد التاسع فبراير 2002 |
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Redundancy
PLCs provide the optimum approach For redundancy system Since its introduction over 20 years ago , the Programmable Logic controller ( PLC ) has become as much a part of the manufacturing and Are two PLCs really better than one ? It is generally accepted that two CPUs run in tandem , the system will be more available , since a failureof one Leaves the other in control . But this uses twice as much hardware, so twice as much hardware , so twice as many defects would be expected , even though the system contiou s to function correctly : any reliability amnd availabiolity analysis must take into account the additional complexity , cost and overall reliability effects of the control system and match this to the plant being Controlled . For a single sensor , We need not necessary employ redundant PLC inputs , which monitor that device . if We have co- located sensore , or redundant ( voted ) field device . Availability or predictability ?the most common reason why reason why control system utilize redundant hardware in a production environment is to Increase the availability of the process, or plant , by allowing it to contioue operation in the event of a fault or falure . With the advantage of mininizing downtime , reducing lost production , and increasing time between Repairs . However , in asafety and protecion system environment , redundancy is often used to achive the aim of providing a predictable system response in the event of Aany single failure these two differing requrirments raise the dicholotomy of not wanting to shut the plant down under any circumstances (production )versus the necessity to shut it swon in a controlled manner under any given circumstance ( safty) . to meet these requirments , there are two strategies which offer different features , despite in some cases being designed using similar configurations of commen hardware . Hot standby vs voting - which is best ? there are two fundamentally different ways for systems with redundant CPU s to operate standby systems . Comprise two CPUs , which are connected to dedicated or shared 1/0 structures. One CPU is active or designated the "Duty" processor. The other is in Standby mode. Standby operation is best applied to continuous Process applications , where loss of control or datd needs to minimized or even eliminated. Examples include Monitoring a turbine, mixing ang producing foods, metats and cement, and emissions monitoring. With a Voting system, the hardware configuration may look identical to the Standby confiiguration, but the difference is in the ability of the outputs to interpret commands from two ( or more ) CPUs which are always active. All CPUs read shared or redundant inputs, and process their logic separately. For process industries as the plant it was designed to monitor and control . to address the by duplicating the or even triplicating the input , processor and output elements . Systems Discrete outputs, the CPUs then send their output data output modules, which are configured to vote in a pre- Determind way- In a system with two CPUs there are four possible scenarios the outputs of the system can Experience, as follows: Thise lets the User select " Safe" stat ( normally the steady state ) for a digital out put. Either CPU can set the Output to its " Safe " stat, but both CPUs must be in agreement to switch it to its " Active " In this scenario, there is no changeover between PLCs, and therefore no "bump" In a system with three CPUs , the Processors vot on the input data and the outputs on the processors' instructions, and a majority vot (two out of Three, or 2003) will be undertaken in the event of a discrepancy. Typical applications include semi- static (low demand) systems like Fire and Gas Detection or Emerency Shutdown (safety Systems), which reside in a steady or safe stafe for the majority of their operational lives, and change of stafe is only occasional. A vote or comparison check is always carried out to ensure the plant is being controlled correctly. The type of voting strategy adopted must also depend upon the degree of Self Test available: output devices must automatically select avalid output demand. Flexible solutions PLC provides a configurable unrivalled range of flexible solution from Simplex, through Standby Systems ,to Duplex (1002, 2002) both with diagnostic converage) , and full triplicated (2003) TMR systems with scaleable 1/0 options within the same control scheme. And with the addition of a fully scaleable operatorn interface such as CIMPLICIIu HMI , users can have a completed mission critical redundancy system based on standard products. Redundancy is a vitally important part of the control systems market, but it needs to be fully understood. Over- specification can be as disastrous as under-specification in the elements of a control system, and with so many buzz- the nature and required performance of the plant of equal importance to the control system hardware failure perforamance is the systematic faliure that can occur in design spectifcation, operation, maintenance and modifications. All these aspects can be adversely affected by using the wrong application of redundancy, and must be fully catered for in any control system. At best, production figures , and at worst , liver are at stake , it is simply not acceptable to throw more hardware at a control problem and hope the redundacy will take care of performance criteria. Only the logical and sensible application of the redundant elements of a control system to match the plant under control will provide a reliable and optimized system. So the next tome someone says they need a duplex PLC , or a TMR system , ask them if they really know why! PLC Word Issue 2/1999 Spot Light on the Issue Guter G. Seip President of EIBA scrl Why we did it! Many good reason for the Convergence initiative and involement of EIBA Today. Almost nothing works without electrical energy. Even more so, today's economicand ecological demands require increasigly intelligent systems for the distribution of electrical energy. Our answer to these requirements in the bulding industry lies in the design of Home and Building Electronc System (HBES) technology. With the objective to prepare a common, open HBES standard that applies to systems and building technology. 15 international companies renowned in this field, founded EIBA in 1990 EIBA quickly expanded over the years. Today. The association encompasses more than 110 companies manufacturing more than 5000 different types of certified EIB predicted. Their installation is carried out more than 70000 EIB trained electrical installers who have all received the same type of cetified training And Use the planning and installation tool , the ETS R Swoftware . Yuet market devlopment showed thaT the EIB standerd alone would not copver all fieds of application . to widen the spectrum of application for Existing EIB system and to increas our mmeber market potenial , the coverage of standerds was initiated the coverage intive has the following objective : Open additional markets for the system . such as the heating ventilation and airconditioning arean . Enhance the system by additional transmission media such as standerdized raioferquency bus concept , which will be impportant to adderdd the big refubishment area Add simpler installation mode such as the so-called Esay- mode and /or Automatic mode , requiring less effort by the installer , Although the trade -off is reduced system, flexibility . HBES system supply a fairly suffiicient amount of application for the broad home market . Initiate partnership with services companies sch as the Telecoms and the Energy Distributors as a leverage to substantially enhance our member HBES marketing impact . we quickly realised that we need compeetent partners to successful;ly put our plans into parctice on the Europaean and international level . Asingle European standardinzed common HBES system platform was of particular important .this common standerd should be suitable for All application in the residential and buliding market A second , yet important effecct : it would also alloe us to copete head on against strong forces from other areas of the globle . the Batibus clup international and HBSA wewe quickly identified as natural partners to EIBA . there leading members of eaccch of these associations decided to found the now called " Konnex Association " the konnex technology bulids on the well-estabished EIB principle , and expands the functional range earlir . Powerbar "PB " LOW IMPEDANCE PB busbar trucking system desigened and manufactured to :- comply with BSEN 60439 -1,2: 1990, 1993 Suitable for use on 3-PH 380V , Hz supply insulation voltage rating of 130 c . The dielecttric testing voltage with 3-phase current is 2500 volts . Comes in feeder and plug - in types . Desigened for horizontal and rizer applictions . The plug-in types offer five outlrts every 3- meters untit the tap-off boxes are eguipped with protective device such as a quick- break switch , MCCB , by a full range available thourgh the range of tapping boxes . Feeder and plug-in untis are interchanneable, they can be mixed without any adapter or special part Certified by an independent accredited testing authority ASTA " for phase , natural and proteective conducors . PB busbar trunking system advantages Higher short- circuit rating The assembly feature of duct makes vit possible to obtain llower reactance values and therfore lower voltage drops . An excellent heat Dissipation By a direct conduction of the barrs to the hosing . Special devices make use of the system more efficient, safe and flexible . An air-carit weights two kilograms!! The American Naval Research Center has developed an air- craft that weeights less than two kilo grams and called it " Dragoney" this plane, which will be used for espionage, can evade radars is it could be considered a small bird. It could follow a pre- programmed path and return again to the base. It could also carry compact camera for surveillance. A robot astronaut Sintists of NASA are developing arobot that could walk on the moon and Mars. It will also be able to move towards the sun in a non- stop iourney to get solar energy. Its speed is expected to be 800k.m per hour and the final experrmental launching will be in mext july in avery dry & cold area in the northern pole An Egyptian - Dutch mobile phone It is exected within the follwing few months that Al- ahly company for communications will produce The first Egyptian made mobile phone. This phone will be prodced in cooperation with one of the Dutch companies. Dr. Hossein El- Kholyv, the Board chief of AlAhly co., declared that the Egyptian mobile phone will be for 400-500 L.E it will be tiny . Light and easy to use. Internet econmies will double four times . According to a recent study one by Nortel company in cooperation with IDC foudation, the economy of the internet , the economy of the 3.8 billion SUS on the ierational level by the yerar 2003 the study wasd announced in the annual meeting of the international Economic Fourum . Also , The study mentiand that the infra- structure of the internet Sctor is going duble four timer to be- come 1.5 billion SUS Also, It is expected that the electronic sector will increase to 1.3 billion SU.S by 2003. Aprogram to study the consequences of explosions of buildings. In Sandia ladoratonies ,USA, there is a study developed to check the consequen ces of disaters an buildings called " Rambarat" it gives information on the ability of buildings to stand natural and man- made disasters. It could also provide a data base regarding any expected threatts and its effects on each building. The programme could be used in trade centesr and schools also. U.A.E: Siemens gets the biggest project contract in the Gulf area for one billion Euro . Siemens group fer power stations nave got a billion Euro contact to establish a power stations that ran by tourbins . thistation whichis expected to generate 1500 megawatt will be bulit in Al-shwehat region ( 250 K.m from Abou Dhabi ) this station will be managed by agroup of international companies ( Abou Dhabi ) power Authority , the American SMS company ) Also , the German group for power distribution will be responsible for maintenance . the station is going to genrate power with the capacity of 5000 mega watt and will purify 200 million galoons of water aday , Mr. Heinrrich Piere, the excutive Director of Siemens group said that the biggest cantract for the company in the Gulf area . Iraq : international committee tackles establishing the biggest power station in iraq . According to areliable source in the iraq gorernment , the UN committee had tackled the establishment of the biggest power station there . theis power station capacity would be 1680mega watt . he also added that the Russian company that would be the executive party is trying to pressuize the committee to get per mission to establish the station . the project is going to cost 450million $U.S.and it was supposed to be established in 1988 and delayed 1990 but it is blocked now . Germany: No more nucleare power !! The German parliament finly agreed to dismantle the nuclear activators within the folwing two decades. By this law, 15 nuclear stations will be closed gradually till 2021. for security reasons, the current German gorernment is willing to abolish the use of such power resourece. However, the members of the christian Democratic party promised that they would cancel such low in case they won the election in the fall. U.S.A The effects of ENRONS Bankupcy!! In a uniqu, Catestestrophical and sudden drop, ENRON Co. for energy- which is one of the biggest energy companies world wide has collapsed. That come of campany administration's announcement of ENRON's bankrupcy after its unsuccessful attempt of purchasing it by its competitor "DAINGLL this caused the deterioration of ENRON's shares from s90 to 5.75. This caused canfusion in many energy and electricity markets all over the world. "Business Week" magazine reports that the deterioration will affect the international market, as theye are more than s2 billion as debts for the banks as well as an other billion for commercial contracts. Such disorder U.S markets as ENRON is amaior supplier of energy in European. Sametimes it contributes with 20% of the European market. That was reflected in the rise of prices in Europe which caused more burdens over the shoulder of the Experts say that the prices of electricity and energy are 2.5% more in the British market up till now especially, since ENRON used to supply around 2.2 million consumers with electricity as well as thousands of companies in the Buitish market. One the certain effects of ENRON's collapse is the increase in the number of the opposers of privatization of the power sector in Europe especially in France where the privatization process is still slow. It is asserted no that there was wide-spread corruption in ENRON's former administration. There has been rumours that most of them had fbed the U.S.A. also, according to reliable sources, Mr. Fasto, the company, acquired S 30 million from notorius deals which helped in the down fall of the company . market, as theye are more than s2 billion as debts for the banks as well as an other billion for commercial contracts. Such disorder U.S markets as ENRON is amaior supplier of energy in European. Sametimes it contributes with 20% of the European market. That was reflected in the rise of prices in Europe which caused more burdens over the shoulder of the Experts say that the prices of electricity and energy are 2.5% more in the British market up till now especially, since ENRON used to supply around 2.2 million consumers with electricity as well as thousands of companies in the Buitish market. One the certain effects of ENRON's collapse is the increase in the number of the opposers of privatization of the power sector in Europe especially in France where the privatization process is still slow. It is asserted no that there was wide-spread corruption in ENRON's former administration. There has been rumours that most of them had fbed the U.S.A. also, according to reliable sources, Mr. Fasto, the company, acquired S 30 million from notorius deals which helped in the down fall of the company . Electric Economies A light shed to facliltate decision - malcing Second year 9th issue A non vegular economic directory Editor - in - chief Adly Mohamed Ahmed Diesign & artistic Supervision Mohamed abd El Aziz Hanan Gamal Translation : Ashraf Melad Correspondence: Swiss Area / Nasr City Mobile : 0123601329 Fax : 3931127 email: adlycall @ yahoo.com www. Eekahraba.8k.com price per copy: Egypt,3# L.E. - Lebanon 1000 L.L Syria, 20 S.L Iraq, 1000 I.D- Sudan, 25 S.P- U.A.E, 10 D.- Qatar, 7 R. Bahrain, 1 R. U.K, 1 S.P Greece, 3000 D. Italy, 500 L.L U.S.A, 3 $ 100% is the average of depending on local production in establishing power stations Dr. Hassan Younis, Minister of Electricity & Power, declared that there must be a priority for the local production in establishing power stations. He also added that they will not import any equipment unless it is not available in Egypt. Such rule will be included any further tender done by the ministry. Dr. Hassan confirmed also that the ministry is paying more attention to increase the local production and to minimze the import process. Designs which suits the Egyptian environment will be developed as well. Finally, according to Dr. Hassan, there is a plan of action to export such equipment to Arab and African states. such procedures will help a lot in solving the problem of idleness that a lot of Egyption youth are suffering from. 15 international tenders for USS 400 million The Egyptian Electricity & Power sector, through its companies, is contributing in 15 international tenders for electrical projects. These tenders which cost US$ 400 million will be accomplished till the first half of this year. The projects are establishing high voltage stations in 8 Arab countries (Morocco, Algeria, Libya, Sultanate of Oman, Lebanon, Yemen & Iraq). Addition, there will be a 50 million Euro power station in Syria and cable connection between Syria and Lebanon for US$ 6 million. The Egyption Minister of Electricity & power, Dr. Hassan Younis, declared that priority will be for the project outside Egypt. Also he said that during the following 6 months, there will be new projects in the west African Arab Countries to be connected with the Eastern ones. In addition, this connection will be increased from 400 to 500 volts. Further more, there will be a project to establish an enhanced information net work to provide a better Internet and communication net work. الصفحة الأولى adlycall@yahoo.com |
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