Calculate the per unit current and per unit voltage. Return on investment roi is a financial ratio used to calculate the benefit an investor will receive in relation to their investment cost. Electrical calculations should be made for all spu projects. Formulas for calculating medication dosage basic formula d x q x a where d desired is the dosage the physician ordered, a available is the dosage strength as stated on the medication label, and q quantity is the volume in which the dosage strength is available e. To use the per unit method, we normalize all the system impedances and admittances. Per unit calculations a key problem in analyzing power systems is the large number of transformers.
Per unit and symmetrical components electrical power. The per unit system is a method of expressing quantities in an electrical system e. This can be computed by dividing the total cost by the total output. The determination of per unit values is not the end objective of a study. The per unit system overview page 1 of 6 overview the per unit system is based on the formula shown in equation 1. Jun 24, 2019 per unit systems is an important concept in power system analysis. 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. Learn more in cfis guide to the priceearnings ratio price earnings ratio the price earnings ratio pe ratio is the relationship between a companys stock price and earnings per share. This makes the per unit value of either voltage or current to be around 1. As an example of how perunit is used, consider a threephase power transmission. Variable costing formula calculator excel template. To gain a better understanding, it is worth running through the typical steps required to solve a fault calculation problem.
Per unit system allows the system operator to overlook abnormalities in the system easily. The per unit system of calculation is a method whereby system impedances and quantities are normalized across different voltage levels to a common base. In the above steadystate equation, time does not appear explicitly. Jan 18, 2017 the per unit system part 03 three problems in per unit quantities problem 01 a 10mva 33kv 3phase generator has a subtransient reactance of 15%. The system calculates this value when the lead time flag is set to v. Elec0014 introduction to power and energy systems the \ per unit system. A singlephase 20kva, 480120 v, 60 hz transformer has an equivalent leakage impedance referred to 120volt winding of using the transformer rating as base values, find perunit leakage impedance. In per unit, base conversion is a normal part of the calculation method while in ohmic method, complex entities conversion. Hence, average cost equals average fixed cost plus average variable costs. Calculations are simplified because quantities expressed as perunit do not. The below table shows the calculation of the holding cost.
The higher the ratio, the greater the benefit earned. Determine the voltage base for all other areas in the circuit by adjusting by the turns. Here are the main reasons for using the per unit system. Perunit and primarysecondary calculations perunit basics a perunit value is the actual value of some quantity divided by the base value of that quantity. The calculations using the per unit system are simplified. Earnings per share formula examples, how to calculate eps. Generally base values of power and voltage are chosen. Markup percentages are especially useful in calculating how much to charge for the goodsservices that a company provides its. For example, the series resistance is usually from 0. In many respects the method is similar to the use of percentage values. 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. Typically this will be related to the rating of a generator, transformer, or transmission line.
Convert actual values to per unit note, per unit conversion on affects magnitudes, not the angles. Pick a voltage base for each different voltage level, vb. The cost per unit is commonly derived when a company produces a large number of identical products. Per unit calculation per unit system examples electrical. Local regulations require an additional 1 ft of freeboard above the 100year flood. So, the calculation of eoq economic order quantity formula for holding cost is 2002 1. We want to determine the prospective fault current at the main switchboard and.
Introduction to per unit systems in power systems part 1b duration. Per unit system explaination with solved example free download as powerpoint presentation. Defining base quantities, per unit voltage per unite current and per unit impedance, selecting the appropriate mva and kv base, calculating the base current and impedance, changing bases, per unit problem solving worksheets, per unit calculation examples and problems. Also, the perunit impedances of synchronous and induction machines fall within relatively narrow ranges over quite large size ranges. Cost per unit definition, examples how to calculate. In key factor analysis, the contribution per unit is first calculated for each product, then a contribution per unit of scarce resource is calculated by working out how much of the scarce resource each unit requires in its production. Again, notice that both transformer per unit impedances are reactive terms and we had to add the j multiplier.
Lets see an example to understand variable cost per unit better. Defect per unit dpu refers to the average number of defects in a given sample product. Fault current calculations the base current of the generator can be computed as, 0 4 0 e e e s ia v the subtransient, transient, and steadystate currents are per unit and amps 1. Motor steps per revolution 200 step per revolution 1. The normalization typically follows transformer ratings. In this example, there are two transformers that divide the system into three different voltage zones that are created by the stepping. Roi formula, calculation, and examples of return on investment. 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.
Using a 8kv, 100mva base in the transmission lines, draw the positive and negative sequence per unit diagrams. Per unit representation results in a more meaningful and correlated data. The eqn 1 show that the per unit impedance is directly proportional to base megavoltampere and. This formula shows how much each unit sold contributes to fixed costs after variable costs have been paid. In simple terms, breakeven point is where there is neither profit nor loss in a companys operation. Per unit and primarysecondary calculations per unit basics a per unit value is the actual value of some quantity divided by the base value of that quantity.
Per unit system practice problem solved for easy understanding. By removing the impact of varying voltages, the necessary calculations are simplified. Power system analysisper unit reactance diagram duration. Now that we have both per unit impedances lets fill in the remaining values in our per unit impedance diagram. Besides being taught in higher education, it is quite commonly used by engineers in the power industry. Assume that no current is flowing in the network, so that all generator and motor voltages are. Equipment impedances can be easily estimated since their per unit impedances lie within a relatively narrow range. The per unit system also makes the calculation easier as all the values are taken in the same unit. By using per unit calculations that different voltage bases but the same powerbase are used in different transformer sections. The per unit system was developed to make manual analysis of power systems easier.
It uses the time basis code from the routing to calculate lead time per unit and the time basis code from the item master as a common factor to multiply all the lead times per units. Every time you cross the transformers, the currents and voltages change. This requires changes in some per unit values if they are already expressed for example on the name plate using different base values. Vin per unit vin kvv base in kv where the base value is a reference value for magnitude. For example, a transient voltage reaching a maximum of 1.
In the per unit system we express voltage, current, kva and impedance as per. Calculate all per phase circuit values in per unit with respect to the new bases. Cost per unit can be defined as the amount of money spent by the company during a time period for producing single unit of the particular product or the services of the company which considers two factors for its calculation i. The \ per unit system example example it is known that the internal reactance of a synchronous machine lies typically in the range 1. Perunit method allows the same basic arithmetic operation resulting in perphase end values, without having to worry about the factor 100 which occurs in per cent system. Use base value of 30 kva and 240 v in zone 1, draw per unit circuit and find per unit value of source voltage and all impedances. The per unit system allows engineers to analyze a single phase network where. Per unit calculation per unit system examples electrical academia. May 26, 2019 the reason the per unit system is employed is because it simplifies calculation of currents. In the previous video, part 1a, we saw what per unit systems are and where they are used.
Calculate the throughput per unit for each product. Also called the per unit total cost, this refers to the per unit cost incurred in the production. A six storey building for a commercial complex has plan dimensions as shown in figure 1. Then a person who is 40 years old is half of the base unit. As you can see there are a lot of things to factor in. When values are expressed in pu, the comparison of electrical quantities with their normal values is straightforward. 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. In this video, part 1b, we will be discussing the formulas for converting values into their per unit equivalents and we will also have a look at the term base values. Source impedance for fault analysis is furnished in per unit. If we know the power in watts of an appliance and how many seconds it is used we can calculate the number of joules of electrical energy which have been converted to sortie other form. This information is then compared to budgeted or standard cost information to see if the organization is producing goods in a costeffective manner the cost per unit is derived from the variable costs and fixed costs incurred by a production process, divided by the number of units produced. For example, with a 22220kv voltage rating of t1 transformer, the v b a s. Calculation of equivalent dwelling units edus the purpose of this worksheet is to determine edus for rd funding determinations only.
Easy and simple methods for calculating short circuit curr. These concepts will be stated and utilized in a stepbystep development. It is different from the traditional measurement of yield. The easy way to do hand calculation is the mva method. Introduction to per unit calculations pages 1 11 text. Eoq definition, formula calculate economic order quantity.
In breakeven point, it is assumed that all the costs have been paid off including. Per unit example how to, tips, tricks, and what to watch out for. The capacitance c increases linearly with the area a since for a given potential difference. Voltage bases are related by transformer turns ratios. Only those components actually in the system have to be included, each component must have an x and an r value. Transformers can be replaced by their equivalent series impedances. Rather determined per unit values serve to assist in the calculation of other system values. Given the system single line diagram, construct and simplify the per unit impedance diagram. Per unit analysis can be used to calculate system three phase fault levels and the current distributions. Absorption costing formula calculation of absorption costing.
All the fixed and variable costs must be taken into consideration in calculating the average cost. Equations used for finding base quantities of impedance, current, and power are shown in table 1, where. Singlephase per unit system university of texas at. All p and q quantities are three phase voltage magnitudes are represented as a fractional part of their standard or base value all phase angles are represented in the same units as normally used advantages 1. In the fault calculation the impedances in the fault circuit must include all significant components and all of these must have their impedance expressed in per unit terms using the appropriate base value. This is the result when the expenses incurred by the entity is equal to the sales. Calculations are simplified because quantities expressed as perunit do not change when they are referred from one side of a transformer to the other.
Design calculations establish minimum guidelines and requirements for generating electrical calculations on projects. For this purpose, an edu is the level of service in gallons per day for an average residential dwelling. Therefore, a 1 mw power plant will produce kilowatts per hour. So much so, it shows up in all exams pertaining to power. Elec0014 introduction to power and energy systems the. It is a ratio of the number of defects over the number of units tested. Per unit analysis understanding the per unit system and its uses.
Electrical power calculations training jim phillips, p. To obtain the new normalized per unit impedances, first we need to figure out. Per unit pu systems are used by engineers to quantify equipment parameters in terms of their nameplate ratings. Shortcircuit current calculations cooper industries. These loads shall be applicable for the design of buildings. Jul 14, 2016 typical per unit values for transformer impedances. Its reactances per unit to the machines own base are x s 2 and the time constants are s4. A perunit value is the actual value of some quantity divided by the base value of that quantity. Find the per unit impedance on a base offind the per unit impedance on a base of 100 mva and 5 kv. Chapter 259 u charts introduction this procedure generates the u control chart for the number of nonconformities per unit, based on the number of nonconformities per sample. The application of three or four fundamental concepts of circuit analysis will derive the basic nature of short circuit currents. The generators perunit voltage is the transmission lines perunit impedance is the other base quantities are 10 0 41.
It may or may not correlate with existing or proposed billing practices. Example seismic analysis and design of a six storey building problem statement. Selecting the generator rating as the base quantities in the generator circuit determine the bus quantities in. Power system analysis lectures examples on reactance diagram and pu calculation. The basic equation for calculating a perunit value is shown below. These calculations shall govern the structural portion of the working drawings. Although powersystem analysis is now done by computer, results are often expressed as per unit values on a convenient systemwide base. Introduction to perunit systems part 1b per unit system. Markup calculator used in managerial or cost accounting, markup formula is the difference between the selling price and cost divided by cost.
For the u chart, the value for u can be entered directly or u can be. Information for a small power system is shown below. Fortunately, short circuit currents are relatively easy to calculate. Imagine a 3phase system with a generator, a transformer, a tline, another transformer, and a load. So, the calculation of eoq for ordering cost is 1010. This appendix presents standards and guidelines for electrical design calculations for spu projects. In a throughput accounting context, a very similar calculation is. The format of the control charts is fully customizable. The generators per unit voltage is the transmission lines per unit impedance is the other base quantities are 10 0 41. Its also common for management to calculate the contribution margin on a per unit basis. Earnings per share are almost always analyzed relative to a companys share price. Contribution margin ratio formula per unit example.
Neutral size is assumed to be the same size as the phase conductors. Per unit system explaination with solved example electrical. The base power may be the rating of a single piece of. Calculate the per unit impedance for transformer t1.
Examples of absorption costing formula with excel template absorption costing formula. May 24, 20 shaft revs per unit 1tooth pitch ns motor revs per unit shaft revs per unit nsnm. Markup calculator calculate the markup, formula, examples. On the other hand, c is inversely proportional to d, the distance of separation because the smaller the value of d, the smaller the potential difference. These hand calculations are very prone to errors due to so many conversion required.
The building is located in seismic zone iii on a site with medium soil. The per unit and ohmic method are very tedious manual calculation. Per unit system is when we normalize the voltage and current at each location. 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. Per unit identities university of minnesota duluth. Property is located in a femadesignated floodplain zone ae and is subject to a 100year.
With transformers, we need to convert the voltage magnitudes,impedances, currents, etc. In management accounting, absorption costing is a tool which is used to expense all costs which are linked with the manufacturing of any product. Define four quantities in per unit of their respective base values. The basic equation for calculating a per unit value is shown below. In per unit notation, the physical quantity isin per unit notation, the physical quantity is expressed as a fraction of the reference vava ue. Singlephase per unit system advantages of the per unit system. This ratio is known as the price to earnings ratio or pe ratio. Fault calculation methods university of new south wales. This metric is typically used to calculate the break even point of a production process and set the pricing of a product. When all impedances in a multivoltage power system are expressed on a common power base and on the nominal voltages of the different subnetworks, the total impedance in pu seen at one bus is obtained by simply adding all impedances in pu, without taking into consideration the. The unit of energy is the joule, the unit of power is the watt, and the unit of time is the second. Download cfis free earnings per share formula template to fill in your own numbers and calculate the eps formula on your own. The first coil has n1 turns and carries a current i1 which gives rise to a magnetic field b1 g. It is most commonly measured as net income divided by the original capital cost of the investment.
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