Wawa Free Essays

A single tube of cerebration’s fluid is received In the laboratory and the following tests requested: total protein, albumin, Gig quantization, microbial culture, Gram stain, leukocyte count and differential cell count. The specimen should be sent to the various laboratories in which order? A. Chemistry lab, homology lab, microbiology lab b. We will write a custom essay sample on Wawa or any similar topic only for you Order Now Homology lab, chemistry lab, microbiology lab c. Microbiology lab, homology lab, chemistry lab d. Homology lab, microbiology lab, chemistry lab 3. You need to prepare a 1 TTT (1 :4 or h) dilution off serum specimen using saline before analysis. Which of the following petting steps would result in this dilution? A. Pipette 0. 5 ml serum, then add 1. 0 ml saline b. Pipette 1. 0 ml serum, then add 2. 0 ml saline c. Pipette 1. 5 ml serum, then add 4. 5 ml saline d. Pipette 2. 0 ml serum, then add 5. 0 ml saline 4. The major components of a spectrophotometer are represented in the following diagram. Which component determines the factor â€Å"b† in Beer’s law, A=BBC? A. Component A b. Component B c. Component C d. Component D At pH of 7. 4, which of the enzymes listed catalysts the following reaction? 5. Private + NADIA a. Lactate oxides b. Lactate dehydrogenate . Private kinas lactate * AND pH 8. 6 is used for serum protein electrophoresis so that 6. A. All serum proteins will have a net negative charge b. All serum proteins will have a net positive charge c. Electromagnetisms is avoided d. Heat production is minimized Seasonality measurements determine the 7. A. Activity of ions per kilogram of solvent b. Grams of dissolved solutes per kilogram of solvent c. Moles of dissolved solutes per kilogram of solvent d. Equivalents of dissolved solutes per kilogram of solvent Which of the following formulas can be used to calculate serum seasonality? 8. A. 2. 5 x An+ . An+ +K+ +CIA- +CO content c. (1. 86 x An+) + (1/18 x glucose) + (112. 8 x BUN) +9 (An+ + K+) -? (CLC- + HCI) 11. A serum sample is diluted 1 to 3 (1:3) before analysis and the following results obtained: Total protein – 4. 1 g/del Albumin- 1. 5 g/del Which total protein concentration should be reported? A. 4. 1 g/del b. 8. 2 g/del c. 12. 3 g/del d. 16. 4 g/del 16. Review the following serum test results: Creating 2. 5 MGM/del (0. 75- 1. 5 MGM/del) Cholesterol 220 MGM/del 126 MGM/del b. A serum glucose 200 MGM/del at anytime 38. If OLD receptors are non-functional due to disease, the plasma level of which lipid loud increase the most? . Fatty acids b. Cholesterol c. Cholesterol esters d. Triglycerides 39. Which of the following serum protein electrophoresis patterns is most typical of the nephritic syndrome? Albumin alpha alphas b. Normal d. Normal beta gamma 40. Which analyze is most likely to be elevated in a specimen drawn 2 hours after an uncomplicated myocardial infarction ? A. KC- MBA (KC-2) b. Mycologist c. Titration I d. Titration T 41. Which of the following serum results correlates best with the rapid cell turnover associated with chemotherapy treatment regimens? A. Creating of 2. 5 MGM/del b. Potassium of 5. Mol/L c. Urea nitrogen of 30 MGM/del d. Uric acid of 10. 0 MGM/del 42. Which set of serum electrolyte results (in Mol/L) is most likely obtain from serum with an elevated lactate level? An+ a. 125 4. 5 b. 135 3. 5 c. 1454. 0 HCI 10 95 28 90 15 43. The following arterial blood gas results are obtained: PH 7. 28 APPC 53 meg POP 75 meg 26 Mol/L HCI- These results correlate best with patient experiencing a. Metabolic acidosis b. Metabolic alkaloids c. Respiratory acidosis d. Respiratory alkaloids 44. The patient with intermittent hypertension has an elevated value for urinary catecholamine metabolites (e. G. Malignancies acid [VIM]). This result may indicate a. Hyperventilation’s b. Hyperthyroidism c. Idiopathic hypertension d. Phosphorescently 45. Blood from newborn has low thyroxin (TO) and elevated thyroid – stimulating – hormone (TTS) compared to reference ranges for that age. These results are most consistent with a. Congenital hypothermia’s b. Congenital primary hypothyroidism c. Congenital secondary hypothyroidism d. A normal response to pregnancy – induced changes in maternal thyroid function 47. The following results are obtained from a patient whose admission diagnosis is billiard obstruction Test Result Conjugated blurring increased Serum: Total blurring Blurring Urine: increased positive Which of the results obtained is inconsistent with the admission diagnosis? A. Serum conjugated blurring b. Serum total blurring c. Urinary blurring d. Urinary rebilling 49. Which of the following enzymes provides the best indication of obstructive liver disease, I. E. , schoolmates? A. Amylase b. Alkaline phosphate c. Separate nontransferable d. Lactate dehydrogenate 50. In a cerebration’s fluid (SF) sample, which of the following proteins is quantitative to assess the permeability of the blood/brain barrier . Albumin b. Gig c. Transferring d. Preferable 51. The following urinalysis are obtained: Glucose by reagent strip: negative Stones by reagent strip: positive These results are most consistent with a. Starvation b. Polynesia c. Diabetes mellitus d. Diabetes insipid 52. A patient with Type l, IDEM has the following results VBG Patient 1 50 MGM/del Ref Range 70- 110 MGM/del FSP 2. 6 Mol/L 2 – 2. 9 Mol/L 53. The patient has the following thyroid profile TTT: decreased OFT: decreased Thyroid peroxides anybody: positive TTS: decreased This patient most probably has a. Hyperthyroidism b. Hypothyroidism . A normal thyroid d. Grave’s disease 53. Choose the diagnosis most consistent with the following: Serum total bill: elevated Serum direct bill: O MGM/del Serum indirect bill: elevated Urine blurring: negative Rebilling: decreased a. UDP – GET deficiency b. Posthypnotic bile obstruction c. Dublin Johnson syndrome d. Intramuscular hemolytic 5. When is a blood sample for determination of the trough level off drug proportionately drawn? A. During the absorption phase of the drug b. During the distribution phase of the drug c. Shortly before the drug administration d. Two hours after the administration Which of the following is used in the treatment of manic depression b. Lithium c. Calcium d. Chloride Which of the following is a commonly encountered xanthium that could potentially interfere with the determination of Diophantine? A. Nicotine b. Caffeine c. Amphetamine d. Proclaimed Which of the following drugs is used as an instrumentation in organ transplantation, especially in liver transplants? A. Metamorphose b. Emendation c. Cloistering d. Parenting Free drug levels can generally be determined by analyzing what body fluid? 9. A. Whole blood b. Illiterate of the plasma c. Urine . OFF of plasma 10. For what colorimetric reaction is the Trainer’s reaction widely used? A. Acetaminophen b. Proponent c. Silicates d. Barbiturates 11. Anticoagulants whole blood is the preferred specimen in determining the exposure to what compound? A. Methanol b. Mercury d. Carbon monoxide 12. Free erythrocyte proprietorship (FEE) levels are useful as a screening method to which of the following metals? A. Zinc b. Lead c. Iron d. Mercury 13. Of the following specimens, which would be appropriate for determining the exposure to lead? A. DEED plasma b. Serum c. Whole blood d. SF 14. Identification of the urinary metabolite bioengineering would be useful in determining exposure to which of the following drugs? A. Codeine b. Cocaine c. Amphetamines d. Proponent 15. TECH is the principal active component of what drug? A. Benedictine b. Marijuana c. Morphine d. Codeine 17. When screening urine for toxic substances, which of the following will not be identified be Irenics Test? A. Bismuth b. Arsenic d. Cyanide 18. Which of the following tests would be particularly useful in determining sopranos exposure? A. Serum seasonality and urine acetone b. Urine seasonality and serum seasonality . Urine acetone and urine seasonality d. Serum sodium and serum acetone 19. Which of the following methods would yield reliable quantification of ethanol in the presence of sopranos a. Reaction with permanganate and chronometric acid b. Conway diffusion followed by dichloride c. Alcohol dehydrogenate reaction d. Gas – liquid chromatography 20. Levels of 8 – 9% chronologically saturation of whole blood are commonly found in which of the following situations? A. Fatal carbon monoxide poisoning b. Acute carbon monoxide poisoning c. Non – smoking residents of rural areas d. Cigarette smokers How to cite Wawa, Papers

Fallen by Evanescence free essay sample

Full of mesmerizing vocals and eerily haunting lyrics, Fallen is alternative rock band Evanescences Grammy-winning debut album. Fallen spent 104 weeks on the Billboard 200- with over half of that time period in the top 20. It went platinum seven times, selling more than seven-million copies in the United States and over 15 million copies worldwide. Having five Grammy nominations, Fallen went on to win two. All of these accolades speak of the great talent of the musicians in this amazing band. Maybe all these things came about because Evanescence is not your typical, crude, pop music- it is real, touching on topics other artists seem to avoid, and seamlessly conveying perfectly dark messages that speak of emotions which everyone feels. Fallen features powerful female vocalist Amy Lee, whose voice provides a refreshing change from the male voices presently heard all over the rock genre. Her voice is so emotional that it feels as if she were sitting right in front of you, letting you help her bear her burdens of unrequited love, sorrows, and grief. We will write a custom essay sample on Fallen by Evanescence or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Unlike most mainstream music today, it gives you something to think about and, subsequently, leaves your soul with something that plagues and stays with you throughout the rest of the day. Amy Lee and co-founder Ben Moody gave birth to the group in Little Rock, Arkansas in 1994, where they met at a youth camp. Their big break was in 2002, when the company behind the movie Daredevil asked Evanescence to headline the soundtrack. By the time the film was released in February, â€Å"Bring Me to Life† was being played all over the radio. Evanescence always keeps the listener guessing, using an interesting mix of musical styles- including classical strings (violins) and more modern guitar riffs. For example, the orchestration of â€Å"My Immortal,† written by both Ben Moody and Amy Lee, is almost completely comprised of pianos and violins. In contrast, a significant number of the songs, such as the first song on the album, â€Å"Going Under† have hard rock elements, including heavy drums and the aforementioned guitar riffs. These compositions are a mixture of heaven and hell, with instances of angelic voices in the background of the song â€Å"Everybodys Fool† compared to occasions of screaming men, as heard in one of their hit singles, â€Å"Bring Me to Life.† This unusually beautiful sound lends Evanescence an originality that is unmistakably their own. Many of the songs on Fallen are influenced by the deaths of Lees 3 year old sister and Moodys grandfather. The strong messages about death and depression induce emotions that may be unwanted for some listeners. They often talk about feeling worthless, feelings that, as teenagers, we need to healthily explore and gives you something that makes you feel as though you are not the only one. On many popular albums, the best song is not the most well known. For example, my favorite song on this album is â€Å"Imaginary.† First released in 1998 on Lee and Moodys Evanescence EP, â€Å"Imaginary† forced me to dig deeper within myself. At first I had no idea of what the song was talking about, but on my second listen, the nonsensical chorus which speaks of purple skies, paper flowers, and candy clouds became a reality. I realized that she wanted to get away from this world, leaving her personal troubles behind by creating a perfect fantasy land. By inviting me into her utopia, I saw the possibility of using creativity to make my own fantasy land become real. The flow of the lyrics, the powerful voice and the beautifully arranged songs are all examples of why this album is amazing. But, something deeper than the external speaks to me when I listen to this music; something that lurks behind the words- perhaps a glimpse of myself. As Lee said in â€Å"Hello,† â€Å"Soon, I know Ill wake from this dream,† but while I am still in it, I will love and cherish Evanescence as long as Im asleep.

A Vampire’s Kiss Essays

A Vampire’s Kiss Essays A Vampire’s Kiss Paper A Vampire’s Kiss Paper â€Å"If you could live forever, what do you live for? † This is the tagline of the latest and box-office vampire movie, Twilight. Revolving around the life of an awkward 17-yr old girl, Twilight is a film about the new life and the inconceivable love Bella Swan found. Pressed to live with her father in Forks, Washington after her mother remarried, Bella came to know a secret kept away from humansthe true existence of vampires. In her first day at Forks High School she became an instant celebrity, what with her damsel-in-distress nature and pale yet stunning beauty. Not only had she been the center of attention but Bella had also got contact with the beautiful god-like Cullens. And as she gets to know the Cullens more, especially the irresistible mind-reading Edward Cullen, her life was put more into danger. It seemed it’s not only humans that found her very appealing, but her scent was mouth-watering to vampires too; thus she became the object fought for by the Cullens and the nomads James, Victoria, and Laurent. A classic battle between good and evil, this time portrayed as a clash involving the vampires that vowed to drink only animals’ blood and those who yearn for humans’ blood, Twilight presents heart-pounding scenes as the fight between James and Edward for Bella’s life ensues. In the end, Edward’s love for Bella conquered all and they went to intimately dance at the school ball. A movie that would make you wish you were a teenage girl, Kenneth Turan of the New York Times believes Twilight succeeds in capturing the essence of the book from where it was adapted. Stephenie Meyer, author of the Twilight saga, is not exactly a great literary stylist but she has come up with one heck of a romantic concept. (http://movies. nytimes. com/2008/11/21/movies/21twil. html) And that is exactly what is shown in the motion picture; the scheme of how love could cross the boundaries of life and death just to be with the one you love most. There are several things that made this film a big hit. One, it got a good plot and a problem that matches that of the Oscar-winning â€Å"Ghost. † While there had been more than handful vampire movies from then until now, Twilight had still made its marked, the newest Dracula now known by the name Edward Cullen. Two, it’s brought to life by a playwright, Melissa Rosenberg, and a director, Catherine Hardwicke, with astounding reverence. Hardwicke particularly, as Turan says, â€Å".. whose entire career has been built on the veneration of young adults, Hardwicke has connected so intensely to the Meyer novel that its hard to imagine anyone else making a better version. † (http://movies. nytimes. com/2008/11/21/movies/21twil. html) And lastly it was acted out by actors, Kristen Stewart and Robert Pattinson as Bella and Edward, who put their heart out to their roles. Turan even compared it to Greta Garbo and Robert Taylor when they did Camille for George Cukor. On the whole, the movie had been a watchful. Not only were the scenes gorgeously produced but the casting, as well as how the roles and the lines were delivered was outstanding. The movie review, made by Kenneth Turan, only made me realize more how wonderful Twilight has been made, despite the fact that it was a low-budget film. It’s a great movie, indeed a motion picture to be talked for years to come. I like it not just because Robert Pattinson was a handsome Edward or I wish that I was Kristen Stewart but also because it touched my inner feminine persona. Every woman and every girl wishes for a knight-in-shining-armor to come and sweep them off their feet. Even when a girl or a woman shows a very strong character, deep inside she is wishing for a prince that would show her the true meaning of love, and how it really feels to love and be loved. Twilight is a movie that captures that essence and for that truth, Twilight, for me, gains two thumbs up. Turan, Kenneth. â€Å"Twilight. † The New York Times. 6 April 2009. http://movies. nytimes. com/2008/11/21/movies/21twil. html [Turan, Kenneth. â€Å"The Love That Dare Not Bare Its Fangs. † New York Times. 21 November 2008. ]

ethnic studies essays

ethnic studies essays America is a land often depicted for its freedoms and opportunities that one so hopefully desires to experience but when you take away the sugar coated deceptions of our beautiful America you get a life time of hate, endless sacrifices and many obstacles that minorities had to overcome to be accepted as an American. After the Civil War and during World War II their were many minorities that paved the way for others but in my opinion the two most recognized ethnic groups that were able to improve their political, social and economic positions within the United States history were African Americans and Native American people. In this essay I will discuss the Native Americans, African Americans as well as two articles in which, I gained very insightful knowledge from and show how all these works has made our America the home it has become today. Over the past hundred years are so, America has shown a great deal of discrimination against African American people. It first started when Africans were taken against their will and put on ships to be sent to America to become slaves for rich Caucasian people. Caucasians gave African Americans little or no rights and had many African Americans doing daily task such as, picking cotton, cooking, cleaning, babysitting, sewing and etc. After a while African American people began to realize that the treatment they were receiving was cruel, usual and violated their freedoms of being human beings. When the Civil War first started around 1939, many African Americans took part in the fight; because they wanted to be free from slavery but to get there they had overcome many hardships to accomplish their goals. After the Civil War everything changed politically, socially and economically. African Americans had the opportunity to become self-employed by owning their own land and running the ir own farms, instead of their masters plantation. They were also being paid by wages now. Slavery also became il...

Poverty and Discrimination Research Paper Example | Topics and Well Written Essays - 2500 words

Poverty and Discrimination - Research Paper Example Poverty is not a disease, rather a condition which can be overcome if proper steps are taken by the policy makers of a country. Furthermore, it’s not only even up to the policy makers alone to alienate poverty, it needs the contribution from people of all walks of society including technocrats, rich and the poor alike. People often argue that poverty isn’t really a problem as such and that the poor are poor as they don’t do much effort to get out of the vicious chain of poverty. Just mentioning a few facts and figures at this stage would give an idea of how widespread this cancer actually is. According to a research carried out by an agency of the United Nations, about three million people (or almost half the population of the entire world) thrive on less than $2.50 a day. According to yet another research, if the wealth of seven of the world’s richest men is combined, it would be much greater than the overall gross domestic product or GDP or 41 of the world’s most indebted and poor countries. Just to give a rough estimate, the population of these 41 countries combined stands at around five hundred and sixty seven million people (National Bureau of Economic Research & National Bureau of Economic Research, 2000). Yet another research goes on to say that there are almost a billion people in the current century who are so poor and illiterate, that they’re even unable to cast their signatures or read a book. Poverty is one of the most major economic issues of the current times since it involves so many people. A solution needs to be discovered not only to manage this problem in the short term, but to eventually alienate it in the longer term. Addressing the issue of poverty would mean a lot more people would gain employment, they would be able to live a healthy life style, be able to finance their own day to day expenses, be able to achieve their basic necessities and finally be

Comparative Industrial Relations Essay Example | Topics and Well Written Essays - 3500 words

Comparative Industrial Relations - Essay Example These three concepts actually signify the administration and handling of people. At times ‘industry’ is related to manufacturing only. However, the principle of Industrial relations is not so limited. The principle entails to enclose the associations amid managers and their employees in aspects of trade and industry activity. The main issue under consideration in the industrial relations is employment. Thus, industrial relations cover all the economic activities where a human resource works under the control of an employer and obtains a salary in exchange of his work. Consequently, industrial relations do not take into account domestic labour as well as self-employed individuals (Edward, n.d., p 1). Industrial relations play a vital role from the employers’ point of view. This is mainly because, in the present times, capital as well as technologies have become increasing obtainable for the companies. And hence, the competitive situation of a company relies on the knowledge and expertise of its human resources to a large extent. Furthermore, it should be noted that the human resources are distinct from any other form of resources. This is owing to the fact that human resources cannot be detached from the individuals in whom they are present. As a result, industrial relations are concerned with managing human resources in view of the productive goals of the business as well as the objectives of the workers (Edward, n.d., p 2). The point of view of industrial relation is fundamentally collective as well as pluralist. It involves the associations and dealings which take place at and out of the place of work. Thereby, it comprises of the relationships amid individual employees, the relationships amid the employees and their manager, the associations the companies and their employees have with the institutes created to support and safeguard their individual interests, in addition to the association-ship amongst those institutes among others. In ad dition, industrial relations takes account of the practices by means of which these associations and dealings are expressed, for instance collective bargaining; employee participation in decision-making; and settlement of complaints as well as disagreements. Furthermore, it also includes the handling of disagreements amongst managers, employees and trade unions, as and when it occurs. These associations as well as practices are subjective to the policies, regulations, and programmes formulated by the government and its agencies. Additionally, these practices are also influenced by the overall political, social, cultural, economic and technological attributes of each nation. Consequently, the industrial relation strategy and its framework in a particular nation are built up in the course of bipartite review procedures (to be precise between the company and its employee representatives, and by them, separately, with the government) as well as tripartite discussion and collaboration (c oncerning government and other social associates) (Macdonald, 1997, pp. 3-4). Components of Industrial Relations The employment relationship or industrial relationship consists of two segments, to be precise, managerial relations as well

Load Flow Analysis For Electricity Supply Engineering Essay

Load Flow Analysis For Electricity Supply Engineering Essay Power flow studies, commonly referred to as load flow, are essential of power system analysis and design. Load flow studies are necessary for planning, economic operation, scheduling and exchange of power between utilities. Load flow study is also required for many other analyses such as transient stability, dynamic stability, contingency and state estimation. Network equations can be formulated in a variety of forms. However, node voltage method is commonly used for power system analysis. The network equations which are in the nodal admittance form results in complex linear simultaneous algebraic equations in terms of node currents. The load flow results give the bus voltage magnitude and phase angles and hence the power flow through the transmission lines, line losses and power injection at all the buses. 1.1 BUS Classification Four quantities are associated with each bus. These are voltage magnitude, phase angle ÃŽÂ ´, real power P and reactive power Q. In a load flow study, two out of four quantities are specified and the remaining two quantities are to be obtained through the solutions of equations. The system buses are generally classified into three categories. Slack bus: Also known as swing bus and taken as reference where the magnitude and phase angle of the voltage are specified. This bus provides the additional real and reactive power to supply the transmission losses, since there are unknown until the final solution is obtained. Load buses: Also know as PQ bus. At these buses the real and reactive powers are specified. The magnitude and phase angle of the bus voltage are unknown until the final solution is obtained. Voltage controlled buses: Also known as generator buses or regulated buses or P- buses. At these buses, the real power and voltage magnitude are specified. The phase angles of the voltages and the reactive power are unknown until the final solution is obtained. The limits on the value of reactive power are also specified. The following table summarizes the above discussion: 1.2 BUS Admittance Matrix In order to obtain the bus-voltage equations, consider the sample 4-bus power system as shown in Fig. 1.1 1.1 The impedance diagram of sample 4-bus power system For simplicity resistances of the lines are neglected and the impedances shown in Fig.1.1 are expressed in per-unit on a common MVA base. Now impedances are converted to admittance, i.e, = 1.1 Fig.1.2 shows the admittance diagram and transformation to current sources and injects currents at buses 1 and 2 respectively. Node 0 (normally ground) is taken as reference. 1.2 the admittance diagram of 1.1 Applying KCL to the independent nodes 1,2,3,4 we have Rearranging the above equations, we get Let, The node equations reduce to Note that ,in Fig.1.2, there is no connection between bus 1 and bus 4, so Above equations can be written in matrix form, 1.2 or in general 1.3 Where vevtor of the injected currents (the current is positive when flowing into the bus and negative when flowing out of the bus) admittance matrix. Diagonal element of Y matrix is known as self-admittance or driving point admittance, i.e. 1.4 Off-diagonal element of y matrix is known as transfer admittance or mutual admittance, i.e. 1.5 can be obtained from equation (1.3), i.e. 1.6 From Fig.1.2, elements of Y matrix can be written as: So 1.3 BUS Loading Equations Consider i-th bus of a power system as shown in Fig.7.4. transmission lines are represented by their equivalent à Ã¢â€š ¬ models. is the total charging admittance at bus i. Fig 1.4: i-th bus of a power system Net injected current into the bus I can be written as : 1.7 Let us define 1.8 Or 1.9 The real and reactive power injected at bus is is 1.10 From equations 7.9 and 7.10 we get 1.11 1.12 1.4 BUS Impedance Matrix The bus impedance matrix for en t 1T nodes can be written as Unlike the bus admittance matrix, the bus impedance matrix cannot be formed by simple examination of the network circuit. The bus impedance matrix can be formed by the following methods: à ¢- Inversion of the admittance matrix à ¢- By open circuit testing à ¢- By step-by-step formation à ¢- From graph theory Direct inversion of the Y matrix is rarely implemented in computer applications. Certain assumptions in forming the bus impedance matrix are: 1. The passive network can be shown within a closed perimeter, (Fig.1.3). It includes the impedances of all the circuit components, transmission lines, loads, transformers, cables, and generators. The nodes of interest are brought out of the bounded network, and it is excited by a unit generated voltage Fig.1.3 Representation of a network as passive elements with loads and faults excluded. The nodes of interest are pulled out of the network and unit voltage is applied at the common node. 2. The network is passive in the sense that no circulating currents flow in the network. Also, the load currents are negligible with respect to the fault currents. For any currents to flow an external path (a fault or load) must exist. 3. All terminals marked 0 are at the same potential. All generators have the same voltage magnitude and phase angle and are replaced by one equivalent generator connected between 0 and a node. For fault current calculations a unit voltage is assumed 1.5 POWER IN AC CIRCUITS The concepts of instantaneous power, average power, apparent power, and reactive power are fundamental and are briefly discussed here. Consider lumped impedance Z, excited by a sinusoidal voltage E (1.13) (1.14) The first term is the average time-dependent power, when the voltage and current waveforms consist only of fundamental components. The second term is the magnitude of power swing. Equation (1.2) can be written as (1.15) The first term is the power actually exhausted in the circuit and the second term is power exchanged between the source and circuit, but not exhausted in the circuit. The active power is measured in watts and is defined as (1.16) The reactive power is measured in var and is defined as: (1.17) These relationships are shown in Fig. 1.4; cosÃŽÂ ¸ is called the power factor (PF) of the circuit, and ÃŽÂ ¸ is the power factor angle. The apparent power in VA is given by (1.18) The power factor angle is generally defined as (1.19) If cosÃŽÂ ¸=1, Q=0. Such a load is a unity power factor load. Except for a small percentage of loads, i.e., resistance heating and incandescent lighting, the industrial, commercial, or residential loads operate at lagging power factor. As the electrical equipment is rated on a kVA basis, a lower power factor derates the equipment and limits its capacity to supply active power loads. The reactive power flow and control is one important aspect of power flow. The importance of power factor (reactive power) control can be broadly stated as: à ¢- Improvement in the active power handling capability of transmission lines. à ¢- Improvement in voltage stability limits. à ¢- Increasing capability of existing systems: the improvement in power factor for release of a certain per unit kVA capacity can be calculated from Eq. (10.6): where PFimp is improved power factor, PFext is existing power factor, and kVAava is kVA made available as per unit of existing kVA. à ¢- Reduction in losses: the active power losses are reduced as these are proportional to the square of the current. With PF improvement, the current per unit for the same active power delivery is reduced. The loss reduction is given by the expression: Where Lossred is reduction in losses in per unit with improvement in power factor from PFext to PFimp. An improvement of power factor from 0.7 to 0.9 reduces the losses by 39.5% à ¢- . Improvement of transmission line regulation: the power factor improvement improves the line regulation by reducing the voltage drops on load flow. All these concepts may not be immediately clear and are further developed. Fig 1.4 1.5.1 Complex Power If the voltage vector is expressed as A t jB and the current vector as C t jD, then by convention the volt-ampe`res in ac circuits are vectorially expressed as E= (A +jB) (C- jD) = AC +BD +j(BC-AD) = P+ jQ (1.20) where P = AC t BD is the active power and Q BC _ AD is the reactive power; I_ is the conjugate of I. This convention makes the imaginary part representing reactive power negative for the leading current and positive for the lagging current. This is the convention used by power system engineers. If a conjugate of voltage, instead of current, is used, the reactive power of the leading current becomes positive. The power factor is given by cosÃŽÂ ¸= (1.21) 1.5.2 Conservation of Energy The conservation of energy concept (Tellegens theorem) is based on Kirchoff laws and states that the power generated by the network is equal to the power consumed by the network (inclusive of load demand and losses). If i1; i2; i3; . . . ; in are the currents and v1; v2; v3; . . . ; vn the voltages of n single-port elements connected in any manner: (1.22) This is an obvious conclusion. Also, in a linear system of passive elements, the complex power, active power, and reactive power should summate to zero: (1.23) (1.24) (1.25) 1.6 POWER FLOW IN A NODAL BRANCH The modeling of transmission lines is unique in the sense that capacitance plays a significant role and cannot be ignored, except for short lines of length less than approximately 50 miles (80 km). Let us consider power flow over a short transmission line. As there are no shunt elements, the line can be modeled by its series resistance and reactance, load, and terminal conditions. Such a system may be called a nodal branch in load flow or a two-port network. The sum of the sending end and receiving end active and reactive powers in a nodal branch is not zero, due to losses in the series admittance Ysr (Fig. 1.5). Let us define Ysr, the admittance of the series elements= j or Z= zl= l(+j)= + =1/Ysr, where l is the length of the line. The sending end power is = Where is conjugate.This gives where sending end voltage is Vs and, at the receiving end: If is neglected: where ÃŽÂ ´ in the difference between the sending end and receiving end voltage vector angles= (. For small values of delta, the reactive power equation can be written as Fig1.5 Power flow over a two-port line. where is the voltage drop. For a short line it is Therefore, the transfer of real power depends on the angle ÃŽÂ ´, called the transmission angle, and the relative magnitudes of the sending and receiving end voltages. As these voltages will be maintained close to the rated voltages, it is mainly a function of ÃŽÂ ´. The maximum power transfer occurs at ÃŽÂ ´=90(steady-state stability limit). The reactive power flows is in the direction of lower voltage and it is independent of ÃŽÂ ´. The following conclusions can be drawn: 1. For small resistance of the line, the real power flow is proportional to sin ÃŽÂ ´. It is a maximum at ÃŽÂ ´=90ËÅ ¡. For stability considerations the value is restricted to below ÃŽÂ ´=90ËÅ ¡. The real power transfer rises with the rise in the transmission voltage. 2. The reactive power flow is proportional to the voltage drop in the line, and is independent of ÃŽÂ ´. The receiving end voltage falls with increase in reactive power demand. 2.1 Practical Load Flow The requirements for load flow calculations vary over a wide area, from small industrial systems to large automated systems for planning, security, reactive power compensation, control, and on-line management. The essential requirements are: à ¢- High speed, especially important for large systems à ¢- Convergence characteristics, which are of major consideration for large systems, and the capability to handle ill-conditioned systems. à ¢- Ease of modifications and simplicity. i.e. adding, deleting, and changing system components, generator outputs, loads, and bus types. à ¢- Storage requirement, which becomes of consideration for large systems The size of the program in terms of number of buses and lines is important. Practically, all programs will have data reading and editing libraries, capabilities of manipulating system variables, adding or deleting system components, generation, capacitors, or slack buses. Programs have integrated databases, i.e., the impedance data for short-circuit or load flow calculations need not be entered twice, and graphic user interfaces. Which type of algorithm will give the speediest results and converge easily is difficult to predict precisely. Table.2.1 shows a comparison of earlier Z and Y matrix methods. Most programs will incorporate more than one solution method. While the Gauss-Seidel method with acceleration is still an option for smaller systems, for large systems some form of the NR decoupled method and fast load-flow algorithm are commonly used, especially for optimal power flow studies. Speed can be accelerated by optimal ordering .In fast decoupled load flow the convergence is geometric, and less than five iterations are required for practical accuraci es. If differentials are calculated efficiently the speed of the fast decoupled method can be even five times that of the NR method. Fast decoupled load flow is employed in optimization studies and in contingency evaluation for system security. The preparations of data, load types, extent of system to be modeled and specific problems to be studied are identified as a first step. The data entry can be divided into four main categories: bus data, branch data, transformers and phase shifters, and generation and load data. Shunt admittances, i.e., switched capacitors and reactors in required steps, are represented as fixed admittances. Apart from voltages on the buses, the study will give branch power flows; identify transformer taps, phase-shifter angles, loading of generators and capacitors, power flow from swing buses, load demand, power factors, system losses, and overloaded system components. No. Compared parameter Y matrix Z matrix Remarks 1 Digital computer memory requirements Small Large Sparse matrix techniques easily applied to Y matrix 2 Preliminary calculations Small Large Software programs can basically operate from the same data input 3 Convergence characteristics Slow, may not converge at all Strong Both methods may slow down on large systems 4 System modifications Easy Slightly difficult See text 2.2 Y-Matrix Method The Y-matrix iterative methods were the very first to be applied to load flow calculations on the early generation of digital computers. This required minimum storage, however, may not converge on some load flow problems. This deficiency in Y-matrix methods led to Z-matrix methods, which had a better convergence, but required more storage and slowed down on large systems. Some buses may be designated as PQ buses while the others are designated as PV buses. At a PV bus the generator active power output is known and the voltage regulator controls the voltage to a specified value by varying the reactive power output from the generator. There is an upper and lower bound on the generator reactive power output depending on its rating, and for the specified bus voltage, these bounds should not be violated. If the calculated reactive power exceeds generator Qmax, then Qmax is set equal to Q. If the calculated reactive power is lower than the generator Qmin, then Q is set equal to Qmin. At a PQ bus, neither the current, nor the voltage is known, except that the load demand is known. A mixed bus may have generation and also directly connected loads. The characteristics of these three types of buses are shown in Table 2-1. Bus type Known variable Unknown variable PQ Active and reactive power Current and voltage PV Active power and voltage Current and reactive power Swing Voltage Current, active and reactive power 2.2.1 GAUSS AND GAUSS-SEIDEL Y-MATRIX METHODS The principal of Jacobi iteration is shown in Fig. 2.1. The program starts by setting initial values of voltages, generally equal to the voltage at the swing bus. In a well-designed power system, voltages are close to rated values and in the absence of a better estimate all the voltages can be set equal to 1 per unit. From node power constraint, the currents are known and substituting back into the Y-matrix equations, a better estimate of voltages is obtained. These new values of voltages are used to find new values of currents. The iteration is continued until the required tolerance on power flows is obtained. This is diagrammatically illustrated in Fig. 2.1. Starting from an initial estimate of, the final value of x* is obtained through a number of iterations. The basic flow chart of the iteration process is shown in Fig. 2.2 Fig2.1 Illustration of numerical iterative process for final value of a function Fig. 2.2 Flow chart of basic iterative process of Jacobi-type iterations 2.2.2 Gauss Iterative Technique Consider that n linear equations in n unknowns () are given. The a coefficients and b dependent variables are known: à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These equations can be written as à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. (2.1) An initial value for each of the independent variables is assumed. Let these values be denoted by The initial values are estimated as à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These are substituted into Eq. (2.1), giving à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These new values of are substituted into the next iteration. In general, at the k-th iteration: à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. 2.2.3 Gauss-Seidel Y-Matrix Method In load flow calculations the system equations can be written in terms of current, voltage, or power at the k-th node. We know that the matrix equation in terms of unknown voltages, using the bus admittance matrix for n+ 1 node, is Although the currents entering the nodes from generators and loads are not known, these can be written in terms of P, Q, and V: The convention of the current and power flow is important. Currents entering the nodes are considered positive, and thus the power into the node is also positive. A load draws power out of the node and thus the active power and inductive vars are entered as:-p j (-Q) =-p + j Q. The current is then (-P + j Q)/. The nodal equal of current at the k-th node becomes: In general, for the k-th node: (2.2) The k-th bus voltage at r + 1 iteration can be written as (2.3) The voltage at the k-th node has been written in terms of itself and the other voltages. The first equation involving the swing bus is omitted, as the voltage at the swing bus is already specified in magnitude and phase angle. The Gauss-Seidel procedure can be summarized for PQ buses in the following steps: 1: Initial phasor values of load voltages are assumed, the swing bus voltage is known, and the controlled bus voltage at generator buses can be specified. Though an initial estimate of the phasor angles of the voltages will accelerate the final solution, it is not necessary and the iterations can be started with zero degree phase angles or the same phase angle as the swing bus. A flat voltage start assumes 1 + j0 voltages at all buses, except the voltage at the swing bus, which is fixed. 2: Based on the initial voltages, the voltage at a bus in the first iteration is calculated using Eq. (2.2) 3: The estimate of the voltage at bus 2 is refined by repeatedly finding new values of by substituting the value of into the right-hand side of the equation. 4: The voltages at bus 3 are calculated using the latest value of found in step 3 and similarly for other buses in the system. This completes one iteration. The iteration process is repeated for the entire network till the specified convergence is obtained. A generator bus is treated differently; the voltage to be controlled at the bus is specified and the generator voltage regulator varies the reactive power output of the generator within its reactive power capability limits to regulate the bus voltage: where stands for the imaginary part of the equation. The revised value of is found by substituting the most updated value of voltages: For a PV bus the upper and lower limits of var generation to hold the bus voltage constant are also given. The calculated reactive power is checked for the specified limits: If the calculated reactive power falls within the specified limits, the new value of voltage is calculated using the specified voltage magnitude and. This new value of voltage is made equal to the specified voltage to calculate the new phase angle. If the calculated reactive power is outside the specified limits, then, This means that the specified limits are not exceeded and beyond the reactive power bounds, the PV bus is treated like a PQ bus. A flow chart is shown in Fig. 2.3 2.3 Newton-Rapson Method Newton-Raphson method is an iterative method which approximates the set of non-linear simultaneous equations to a set of linear equations using Taylors series expansion and the terms are restricted to first order approximation. 2.3.1 Simultaneous Equations The Taylor series is applied to n nonlinear equations in n unknowns, à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. As a first approximation, the unknowns represented by the initial values can be substituted into the above equations, where are the first estimates of n unknowns. On transposing Where is abbreviated as The original nonlinear equations have been reduced to linear equations in The subsequent approximations are à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦ Or in matrix form: The matrix of partial derivatives is called a Jacobian matrix. This result is written as This means that determination of unknowns requires inversion of the Jacobian 2.3.2 Rectangular Form of Newton-Rapson Method of Load Flow The power flow equation at a PQ node is Voltage can be written as: Thus, the power is ] ] Equating the real and imaginary parts, the active and reactive power at a PQ node is: where and are functions of and . Starting from the initial values, new values are found which differ from the initial values by and (First iteration) (First iteration) For a PV node (generator bus) voltage and power are specified. The reactive power equation is replaced by a voltage equation: 2.3.3 Polar Form of Jacobian Matrix The voltage equation can be written in polar form: Thus the power is Equating real and imaginary terms: The Jacobian in polar form for the same four-bus system is The slack bus has no equation, because the active and reactive power at this bus is unspecified and the voltage is specified. At PV bus 4, the reactive power is unspecified and there is no corresponding equation for this bus in terms of the variable. The partial derivatives can be calculated as follows: 2.3.4 Calculation Procedure of Newton-Raphson Method The procedure is summarized in the following steps, and flow charts are shown in Figs 2.4 and 2.5 à ¢- Bus admittance matrix is formed. à ¢- Initial values of voltages and phase angles are assumed for the load (PQ) buses. Phase angles are assumed for PV buses. Normally, the bus voltages are set equal to the slack bus voltage, and phase angles are assumed equal to 0ËÅ ¡, i.e., a flat start. à ¢- Active and reactive powers, P and Q, are calculated for each load bus à ¢- P and Q can, therefore, be calculated on the basis of the given power at the buses à ¢- For PV buses, the exact reactive power are not specified, but its limits are known. If the calculated value of the reactive power is within limits, only P is calculated. If the calculated value of reactive power is beyond the specified limits, then an appropriate limit is imposed and Q is also calculated by subtracting the calculated value of the reactive power from the maximum specified limit. The bus under consideration is now treated as a PQ (load) bus. à ¢- The elements of the Jacobian matrix are calculated à ¢- This gives and à ¢- Using the new values ofand, the new values of voltages and phase angles are calculated. à ¢- The next iteration is started with these new values of voltage magnitudes and phase angles. à ¢- The procedure is continued until the required tolerance is achieved. This is generally 0.1kW and 0.1 kvar. Fig 2.4 Flow chart for NR method of load flow for PQ buses. Fig.2.5Flow chart for NR method of load flow for PV buses 2.3.5 Impact Loads and Motor Starting Load flow presents a frozen picture of the distribution system at a given instant, depending on the load demand. While no idea of the transients in the system for a sudden change in load application or rejection or loss of a generator or tie-line can be obtained, a steady-state picture is presented for the specified loading conditions. Each of these transient events can be simulated as the initial starting condition, and the load flow study rerun as for the steady-state case. Suppose a generator is suddenly tripped. Assuming that the system is stable after this occurrence, we can calculate the redistribution of loads and bus voltages by running the load flow calculations afresh, with generator 4 omitted. Similarly, the effect of an outage of a tie-line, transformer, or other system component can be studied. Table 2-2 Representation of Load Models in Load Flow 3. Conclusion Load flow is a solution of the steady-state operating conditions of a power system. It presents a frozen picture of a scenario with a given set of conditions and constraints. This can be a limitation, as the power systems operations are dynamic. In an industrial distribution system the load demand for a specific process can be predicted fairly accurately and a few load flow calculations will adequately describe the system. For bulk power supply, the load demand from hour to hour is uncertain, and winter and summer load flow situations, though typical, are not adequate. A moving picture scenario could be created from static snapshots, but it is rarely adequate in large systems having thousands of controls and constraints. Thus, the spectrum of load flow (power flow) embraces a large area of calculations, from calculating the voltage profiles and power flows in small systems to problems of on-line energy management and optimization strategies in interconnected large power systems. By the load flow studies which performed using digital computer simulations. I have a main idea of how a power networks power flow calculation operation, planning, running, and development of control strategies. Applied to large systems for optimization, security, and stability, the algorithms become complex and involved. While the study I have done above just a small part of the research and I think the treatment of load flow, and finally optimal power flow, will unfold in my following study.