The \ per unit system converting in per unit two magnetically coupled circuits converting in per unit two magnetically coupled circuits fluxcurrent relations. Hi, im struggling with calculating the current from per unit voltage and power values. Provides a more meaningful comparison ofprovides a more meaningful comparison of parameters of machines with different ratings. Metric units the kilogram is the unit of mass in the metric system. The normalization typically follows transformer ratings. Define four quantities in per unit of their respective base values. This makes the per unit value of either voltage or current to be around 1. Per unit calculation per unit system practice problem. Per unit pu is commonly used for the calculation of voltage, current, impedance, and power in power flow and related calculations. The per unit system overview page 1 of 6 overview the per unit system is based on the formula shown in equation 1. In power system calculations a normalization of variables called per unit normalization is almost always used. Bate11 university of michigan a new definition and model of a system is presented utilizing graph theoretic concepts and introducing nested graphs. When a decision is made to unit price in a retail location,every effort should be made to provide unit pricing across the entire store.
On the second day, jim builds upon the per unit system and takes you to the next level with symmetrical components and unbalanced power system calculations. Supplementary units 5 derived units units expressed algebraically with mathematical symbols such as multiplication and division. The international system of units contents the bipm and the metre convention 95 preface to the 8th edition 101 1 introduction 103 1. Per unit and symmetrical components electrical power.
Note that you do not have enough information to actually calculate the values of components in the equivalent circuit. By a comprehensive search of the literature, this abstract formulation of a system is shown to incorporate ex tant theory. Per unit quantities simply theoretical deduction and give them more generalizes forms. A power system is an interconnected network with components converting nonelectrical energy continuously into the electrical form and transporting the electrical energy from generating sources to the loadsusers. Components of the system unit home page university of. Circuits are simplified voltages have same range in per unit in all parts of the system from ehv system to distribution and utilization when expressed in the per unit system, apparatus parameters usually fall in narrow range regardless of apparatus size. The per unit system introducing new units of measurements in order to simplify the analysis of power systems. Pick a voltage base for each different voltage level, vb. The system unit what are common components inside the system unit. Here are the main reasons for using the perunit system. This can be achieved based on the following per unitization system. Treat each load on the systems as a resistance in series with a reactance. Consider a pair of voltage sources sitting side by side with. Vin per unit vin kvv base in kv where the base value is a reference value for magnitude.
In addition, the need to transform from 3phase to 1phase equivalent and vice versa is avoided with the use of per unit quantities. Several examples of working with per unit are demonstrated in this crisp clear presentation. Generally base values of power and voltage are chosen. Power systems basic concepts and applications part i. Vabase kva vaload 750kva voltage base 415v line voltage 415v power.
Advantaggyes of per unit system normally we are dealing with numericsnormally we are dealing with numerics near unity rather than over a wide range. The leakage impedance of this transformer was found in example 64 to be 1. Threephase per unit system the same advantages apply to a threephase system if the following rules are obeyed. It is especially convenient if many transformers and voltage levels are involved. Although powersystem analysis is now done by computer, results are often expressed as perunit values on a convenient systemwide base. The system unit a chip is a small piece of semiconducting material, usually silicon, on which integrated circuits are etched. Per unit notation in per unit notation, the physical quantity isin per unit notation, the physical quantity is expressed as a fraction of the reference vava ue. The per unit system is a method of expressing quantities in an electrical system e. Calculations are simplified because quantities expressed as perunit do not change when they are referred from one side of a transformer to the other. Base units note 1 the elementary particles here must be atoms, molecules, ions, electrons or other particles. The computation effort in power system is very much reduced with thee use of per unit quantities. View notes per unit calculation from electrical keee4269 at university of malaya. Sketch the per phase, per unit equivalent circuit of the power system in figure 102.
Perphase, perunit equivalent circuit pdf to word 2007 of this power system using a base apparent. The per unit system was developed to make manual analysis of power systems easier. Elec0014 introduction to power and energy systems the. Per unit pu system advantages and disadvantages in power system analysis, per unit pu system is used to express a physical variable as a fraction of base or reference value. Per unit system for the analysis of electrical machines or electrical machine system, different values are required, thus, per unit system provides the value for voltage, current, power, impendence, and admittance. Here are the main reasons for using the per unit system. Singlephase per unit system advantages of the per unit system. Per unit system allows the system operator to overlook abnormalities in the system easily. The base power may be the rating of a single piece of. I can do it one way but get a different result when doing it another way. A per phase steadystate equivalent circuit of a synchronous generator and the system. While performing calculations, referring quantities from one side of the transformer to the other side serious errors may be committed. For each system parameter, perunit value is equal to the actual value divided by a base value.
Transformers can be replaced by their equivalent series impedances. Avoirdupois is a system of weight based on the 16 ounces per pound rather than the 12 ounces per pound in the troy system of weight. In many respects the method is similar to the use of percentage values. The \per unit system converting in per unit two magnetically coupled circuits converting in per unit two magnetically coupled circuits fluxcurrent relations. Just imagine you are in the united states and need to compare measurements with someone elsewhere in the world. In this course you will learn exactly what per unit analysis is, the main advantages of using it, how manufacturers of equipment use and rate their products and the technique of converting to and from the per unit system. In per unit notation, the physical quantity isin per unit notation, the physical quantity is expressed as a fraction of the reference vava ue. Per unit system is the ratio between the actual value in any unit and the base or reference value in the same unit. The base voltage varies by the voltage ratio of each transformer in the circuit but the base apparent power stays the same through the circuit. Learn how to more easily use positive, negative and. By definition, the per unit value of a quantity is the ratio of the original quantity to its base value which results in a dimensionless per unit or pu value. When they say 5 meters, you pull out your calculator and convert to feet and inch. The system unit the case of the system unit, or chassis, is made of metal or plastic and protects the electrical components inside.
Similarly, the base quantities on the highvoltage side are 150000 v, 2400 v, 62. Sep 16, 2017 per unit system is the ratio between the actual value in any unit and the base or reference value in the same unit. Per unit calculations a key problem in analyzing power systems is the large number of transformers. Learn how to more easily use positive, negative and zero sequence components and draw zero sequence diagrams. The trend is towards a smaller form factor, or size and shape, of desktop computers. Equipment impedances can be easily estimated since their per unit impedances lie within a relatively narrow range. Or in the other words, per unit is a scaling system to make calculation process in analyzing an electrical network system easier, b. This class is loaded with many in class examples and problems for a hands on. A common threephase voltampere base is used throughout the system, where sbase,3. Circuits are simplified voltages have same range in per unit in all parts of the system from ehv.
The per unit system offers computational simplicity by eliminating units and expressing system quantities as dimensionless ratios. Voltage bases are related by transformer turns ratios. The perunit system offers computational simplicity by eliminating units and expressing system quantities as dimensionless ratios. The primary task for the transmission system is to transmit energy from generation areas to load areas. The idea is to dick base values for quantities such as voltages, currents, impedances, power, and so on, and to define the quantity in per unit as follows. It ends with a short discussion of per unit systems and power system representation. Main circuit board in system unit contains chips, integrated circuits, and transistors also called system board p. The perunit system conventional units of measurement for voltage, current, power and impedance are for instance. Any quantity is converted into per unit quantity by dividing the numeral value by the chosen base value of the same dimension. In power system analysis, per unit pu system is used to express a physical variable as a fraction of base or reference value.
The per unit system also makes the calculation easier as all the values are taken in the same unit. Perunit system the base apparent power and base voltage are specified at a point in the circuit, and the other values are calculated from them. Unit commitment results for these two systems are presented in. Usually, the per unit quantities being of the order of unity or less can easily be handled with a digital computer.
Download as ppt, pdf, txt or read online from scribd. Per unit system calculating i from power and voltage. The avoirdupois pound is the primary unit of mass in the english system. To the conventional power system for which the rms linetoneutral voltage represents. Voltages, currents and impedances expressed in per unit do not change when they are referred from one side of transformer to the. For each system parameter, per unit value is equal to the actual value divided by a base value. Per unit system per unit system is when we normalize the voltage and current at each location. The perunit system was developed to make manual analysis of power systems easier. Browse per unit questions and answers, or ask your own per unit question and receive a knowledgable answer from a topic expert. Per phase, per unit equivalent circuit pdf to word 2007 of this power system using a base apparent.
This can be achieved based on the following perunitization system. Course description in the power systems analysis field of electrical engineering, a perunit system is the expression of system quantities as fractions of a defined base unit quantity. Integrated circuit contains many microscopic pathways capable of carrying electrical current. The system unit system unit is case that has electronic components of the computer used to process data. Advantages and disadvantages of per unit system in power system analysis, per unit pu system is used to express a physical variable as a fraction of base or reference value. Calculate of a new per unit value with changing voltage base andor power base. Per unit and symmetrical components brainfiller, inc. It would be very difficult to continually have to refer impedances to the different sides of the transformers this problem is avoided by a normalization of all variables. The system is represented with an infinite bus, which holds a constant voltage.
To assure realistic results, data for two large systems up to 96 units were used. Select rated values as base values, usually rated power in mva and rated phase voltage in kv. The generators perunit voltage is the transmission lines perunit impedance is the other base quantities are 10 0 41. Jan 15, 2015 the computation effort in power system is very much reduced with thee use of per unit quantities. The perunit value of any quantity is defined as the ratio of actual value in any unit to the base or reference value in the same unit. Unit pricing is helpful i n that it displays the price of all brands and sizes of a product category per unit of measure basis e. A motherboard or also know as system board, is the main circuit board of the system. Per unit analysis the per unit method of power system analysis eliminates the need for conversion of voltages, currents and impedances across every transformer in the circuit. Per unit system practice problem solved for easy understanding.
As the per unit values of parameters of a machi f i d i ll f llhine of a given design normally falls. Introduction to per unit calculations pages 1 11 text. For example, a transient voltage reaching a maximum of 1. The swedish transmission system consists of approximately 15327 km power lines, and there are 16 interconnections to other countries. Then a person who is 40 years old is half of the base unit. Jim phillips teaches you the basics of the per unit system and electric power system analysis during the first day of the two day class. For the analysis of electrical machines or electrical machine system, different values are required, thus, per unit system provides the value for voltage, current, power, impendence and admittance. Most chips are not much bigger than one half inch square. Sketch the perphase, perunit equivalent circuit of the power system in figure 102. Circuits are simplified voltages have same range in per unit in all. When values are expressed in pu, the comparison of electrical quantities with their normal values is straightforward. Apr 28, 2016 in power system analysis, per unit pu system is used to express a physical variable as a fraction of base or reference value.
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