The unit cost method of estimation is used for project design estimates and bid estimates. A key issue in the paper f9 syllabus is that students start. Unit conversion data listed in this report are defined in the inchpound system of units. Let us take the example of company xyz ltd that manufactures clothes for people of the elite. To use the per unit method, we normalise all the system impedances and admittances within the network under. By using per unit calculations that different voltage bases but the same powerbase are used in different transformer sections. 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. Product cost per unit is a figure used by businesses to determine the actual cost of a single unit of product. It is used in those industries or departments where machinery is predominant and there is little or practically no manual labour. This post is a continuation of per unit system practice problem solved for easy understanding in the previous post, we calculated the per unit impedance of each equipment in the power system. Transmission line design information in these notes, i would like to. There are mainly two advantages of using the per unit system. 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. Estimated 2012 cost for solid waste and recycling service per unit.
Also, machine and transformer impedances fall within fairly narrow ranges for each type and construction of device while the perunit system is employed. Per unit quantities simply theoretical deduction and give them more generalizes forms. For example, a motor with a 100 horsepower hp nameplate rating which delivers 90 hp to a dynamic load is said to be 90% loaded or 0. The following calculators compute various base and per unit quantities commonly used in the per unit system of analysis by power system engineers.
The per unit value of any quantity is the ratio of a quantity to its base value, the ratio expressed as a scalar decimal number. It shows managements commitment to process improvements and product innovation to gain competitive advantages. This article, part of a series of articles, will explain step by step how to calculate these parameters for any component anywhere in the power system. For easier calculations of an electrical system, the quantities are represented in their base units or per units.
At least one of the advantages of polyphase power networks is now apparent. Any quantity is converted into per unit quantity by dividing the numeral value by the chosen base value of the same dimension. The per unit system also makes the calculation easier as all the values are taken in the same unit. Per unit and percentage quantities, in this article you will learn what is per unit system. In the previous page, we discussed the physical flow of units step 1 and how to calculate equivalent units of production step 2 under the weighted average method. The normalization typically follows transformer ratings. Absorption costing definition, formula how to calculate. This gives the value in ohms which is to be taken as 1. The product is created from the expectation of the customer and, hence, cost is also based on similar lines. Explain the requirements of planning the operation of a power system. Per unit impedance of transformers is the same referred to either side of it.
It is one of the methods of absorbing factory expenses to production. The economic benefits of recycling and waste reduction. The unit method estimating consists of choosing a standard unit of accommodation and multiplying an approximate cost per unit. By removing the impact of varying voltages, the necessary calculations are simplified. Equivalent unit calculations accounting for managers. It is important, however, to designate either percent % or per unit pu. This tactic makes entry into a market by competitors difficult. Between 1920 and 1955, for instance, the steel industry was able to reduce laborhours per unit to 79% each time cumulative production doubled. There are many advantages to use the perunit system in power network. Learning curves have application in services as well as industry. Tem transmission lines all exhibit axial symmetry from a circuit theory perspective the line is completely described by four distributed parameter quantities. Machine hour rate is the cost of running a machine per hour. Calculate equivalent units of production and cost per equivalent unit using the weighted average and fifo methods. Contribution per unit sales price per unit less variable cost per unit breakeven volume fixed overhead contribution per unit the number of units you would need to sell in order to earn enough contribution to cover the fixed overhead e.
Voltages, currents and impedances expressed in per unit do not change when they are referred from one side of transformer to the. The eqn 1 show that the per unit impedance is directly proportional to base. With transformers, we need to convert the voltage magnitudes,impedances, currents, etc. Pdf the article considers the positive and negative aspects of the use of electric vehicles. Another approach to solve circuits containing transformers is the perunit system. Calculate the capacitance of each line conductor per km.
Per unit pu is commonly used for the calculation of voltage, current, impedance, and power in power flow and related calculations. In this method, the quantity surveyor counts the number of units which are going to be accommodated in a building, for example the number of occupants or main furniture objects used by an individual. Home category electrical engineering mcq questions and answers power system. Calculate per unit values of voltages and impedance in each section and connect them up as per the topology of the oneline diagram. 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. As the per unit values of parameters of a machi f i d i ll f llhine of a given design normally falls. Fundamental to any power system analysis is the knowhow of per unit systems. Per unit calculation per unit system examples electrical academia. Impedance and voltagelevel conversions are avoided. Advantages and disadvantages of per unit system engineering.
The per unit system of calculation is a method whereby system impedances and quantities are normalized across different voltage levels to a common base. This makes the per unit value of either voltage or current to be around 1. The advantages of calculators with the increasing prevalence of calculators in the classroom, a heated debate has developed over the potential benefits and drawbacks resulting from their use by students. Singlephase per unit system advantages of the per unit system. So the ultimate planner goes through three departments on its way to finished goods inventory. Very few universities teach per unit and symmetrical components calculations anymore but it is still a fundamental. Per unit data representation yields valuable relative magnitude information. Goals of material handling in a typical manufacturing facility. Product cost per unit includes all variable and fixed costs. Per unit pu systems are used by engineers to quantify equipment parameters in terms of their nameplate ratings. Calculations are simplified because quantities expressed as perunit do not. For example, in the electronics component industry, the cost of developing an integrated circuit is. The perunit system was developed to make manual analysis of power systems easier.
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. For simulating steady state and transient models in the computer this method is very useful. Advantaggyes of per unit system normally we are dealing with numericsnormally we are dealing with numerics near unity rather than over a wide range. 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. Advantages of per unit and percent calculations ver. 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. It is of interest to calculate the surge impedance for this circuit. Transformers can be replaced by their equivalent series impedances. Universal soil loss equation usle a r x k x ls x c x p.
It ends with a short discussion of perunit systems and power system representation. Advantages and disadvantages of per unit system instrumentation. When compared to the unit and superficial area method, the elemental estimate or elemental method of estimating is a more detailed method of calculating the cost of a construction project. We will continue the discussion under the weighted average method and calculate a cost per equivalent unit. Circuit analysis of systems containing transformers of various transformation ratios is greatly simplified. Calculations are simplified because quantities expressed as perunit do not change when they are referred from one side of a transformer to the other.
Calculate the shortcircuit current in both sides when rated voltage is applied to the. Unit method of estimating advantages and disadvantages. The most important of these methods, both in the real world and in the exam, is npv. The determination of per unit values is not the end objective of a study. While performing calculations, referring quantities from one side of the transformer to the other side. As was noted in the caption for the opening photograph, 1year death rates of heart transplant patients at temple university. When they say 5 meters, you pull out your calculator and convert to feet and inch. Per unit analysis for single and three phase systems udemy.
Per unit system allows the system operator to overlook abnormalities in the system easily. Per unit identities university of minnesota duluth. The result is the singlephase per unit impedance diagram. Rather determined per unit values serve to assist in the calculation of other system values.
Fixed costs include those items that a business must pay no matter how many. In addition, information on the main advantages and disadvantages of electric vehicles is. Singlephase per unit system university of texas at. Estimate the building cost base on the depends on the population unit.
It may represent 15% to 70% of the total cost generated in the. This is the amount, which is compared to the tolerable soil loss limits. It would be very difficult to continually have to refer impedances to the different sides of the transformers thi bl i id d b li i f ll energy systems research laboratory, fiu this problem is avoided by a normalization of all variables. Per unit calculations a key problem in analyzing power systems is the large number of transformers. In many respects the method is similar to the use of percentage values. Therefore the operational benefit to long distance transmission of. The unit method of estimating is the simplest and quickest method of estimating the cost of a proposed construction project. The cost estimate is obtained by multiplying the number. Calculations are simple and so the programming task is lessees.
Target costing key features, advantages and examples. The per unit 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. Per unit fault calculations is a method whereby system impedances and quantities are normalised across different voltage levels to a common base. The perunit system is mainly used in the circuit where. When analyzing a real system, all parameters such as voltage, current, power, and impedance can be converted to per unit.
In each department raw materials, labor and overhead are being added to the planners. 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. Provides a more meaningful comparison ofprovides a more meaningful comparison of parameters of machines with different ratings. Just imagine you are in the united states and need to compare measurements with someone elsewhere in the world. A represents the potential longterm average annual soil loss in tonnes per hectare tons per acre per year. Per unit system is when we normalize the voltage and current at each location. While performing calculations, referring quantities from one side of the transformer to the other side serious errors may be committed. This estimate is easily understood by the client or any party involved in the design consultation because it shows separate elements of the building that have to be priced. Per unit and symmetrical components electrical power. Basic hydraulic principles of openchannel flow by harvey e. Introduction to per unit calculations pages 1 11 text. Finally, the formula for absorption cost is derived by adding up direct labor cost per unit, direct raw material cost per unit, variable manufacturing overhead per unit and fixed manufacturing overhead per unit as shown above. The effective series resistance per unit length in m all conductors that make up the line crosssection are in.
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