The normalization typically follows transformer ratings. These normalized impedances are known as per unit impedances. Production model for bottomup calculation of labor, material. 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. Calculate all per phase circuit values in per unit with respect to the new bases just specified. Well use the metric calculations above as base for this setup so 200 steps per unit it is. 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. So much so, it shows up in all exams pertaining to power. However, the availability of computer programs for system analysis has diminished to some extent the need for the pu system of calculations. Per unit system allows the system operator to overlook abnormalities in the system easily. In the metric system, flow is in liters per second ls or meters cube per hour m3h. Watch this video to see jim phillips explain how to use the positive, negative and zero sequence impedances in a per unit format to calculate the three phase and. Calculation of equivalent dwelling units edus the purpose of this worksheet is to determine edus for rd funding determinations only.
More importantly, while c looks like it is making a loss under traditional costing, abs tells a different story. Introduction to per unit calculations pages 1 11 text. Using a 8kv, 100mva base in the transmission lines, draw the positive and negative sequence per unit diagrams. Latent heat gain is the energy added to the space when moisture is added to the space by means of vapor emitted by the occupants, generated by a process or through air infiltration from outside or adjacent areas. Ee 423 fault analysis notes university of moratuwa. Transformers can be replaced by their equivalent series impedances.
Information for a small power system is shown below. The standard produces fault current results for an unloaded network, that is the results do not include load current and the prefault. Electric utility data is also often provided in terms of per unit and symmetrical components. This data will, of course, be different for each of the different types of calculations. The value of n, called the scaling exponent, depends on the physical result to be scaled. Iyigun an important issue in the construction and maintenance of information systems is the amount of storage required. Predefined, simplified field notation, or custom calculation script.
Here are the main reasons for using the per unit system. Memory storage calculations professor jonathan eckstein adapted from a document due to m. Here are the main reasons for using the perunit system. Pick a voltage base for each different voltage level, vb. Jul 21, 2015 per unit system and symmetrical components are used for many short circuit calculations. The generators perunit voltage is the transmission lines perunit impedance is the other base quantities are 10 0 41. The per unit system was developed to make manual analysis of power systems easier. Total variable costs auto calculated as the sum of all variable costs. When the insulation of the system fails at one or more points or a conducting object comes into contact with a live point, a short circuit or a fault occurs.
Per unit analysis understanding the per unit system and its uses. Per unit system per unit system is when we normalize the voltage and current at each location. Any per unit impedance will have the same value on both the primary and secondary of a transformer and is independent of voltage level. Scaling of unit cost with production volume including automatic recalculation of opex and capex based on production requirements cost breakdown by production step and resource category february 18, 2016 cost modeling. Just imagine you are in the united states and need to compare measurements with someone elsewhere in the world. Training program costing example university of washington. More specifically, the per unit method of calculation is often used in the calculation of short circuit currents. The perunit system was developed to make manual analysis of power systems easier. Equations used for finding base quantities of impedance, current, and power are shown in table 1, where. Auto calculated as cost per unit x quanity since these are variable costs, input the cost required to produce one unit of the productservice. How the table is used in addition to determining pressure temperature relationships, you can compute the amount of steam that will be condensed by any heating unit of known btu output. Singlephase per unit system university of texas at. The base values for each singlephase transformer are first calculated. This class is loaded with many in class examples and problems for a hands on.
Threephase per unit system the same advantages apply to a threephase system if the following rules are obeyed. Although power system analysis is now done by computer, results are often expressed as per unit values on a convenient system wide base. For example, a transient voltage reaching a maximum of 1. Source impedance for fault analysis is furnished in per unit. Equipmentmachinerytooling totals from per item price and number of stations estimated floor space needed from equipment sizes. 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. Consider, for example, a threephase twowinding transformer with these. The bfe is 9 feet and existing ground elevation is approximately 7 feet. The perunit system is a method of expressing quantities in an electrical system e. For example, a 1,000 kva transformer with an 80% power factor. Calculation of system fault levels sp energy networks.
Convert actual values to per unit note, per unit conversion on affects magnitudes, not the angles. 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. For this purpose, an edu is the level of service in gallons per day for an average residential dwelling. Auto calculated as the sum of all the costs per unit. 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. The examples include bathroom fixtures, kitchen sinks, laundry trays and washing machines. Jul 02, 2006 select the desired calculation option.
Generally base values of power and voltage are chosen. Per unit system is the ratio between the actual value in any unit and the base or reference value in the same unit. When values are expressed in pu, the comparison of electrical quantities with their normal values is straightforward. The generators per unit voltage is the transmission lines per unit impedance is the other base quantities are 10 0 41. Marlap not es that such a deviation, even if it is large, may not give a reliable indica. The volume per unit of mass in cubic feet per pound. From now on i will just use gallons per minute or gpm. 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. Design of potable water plumbing systems ced engineering. Define four quantities in per unit of their respective base values. None of these subsystems is of much use as a single, independent unit.
Example calculations design a cmu pier and ground anchor foundation for a manufactured home to be placed in an sfha zone ae having a flood velocity of 2 fps. Although powersystem analysis is now done by computer, results are often expressed as perunit values on a convenient systemwide base. Specify the new voltage base in the region where calculations should begin. Determine the voltage base for all other areas in the circuit by adjusting by the. Then a person who is 40 years old is half of the base unit. The standard produces fault current results for an unloaded network, that is the results do. Matlab simulink student software hardware support file exchange. Per unit system explaination with solved example free download as powerpoint presentation. Similarly, we talk of the business system and of the organization as a system consisting of interrelated departments subsystems such as production, sales, personnel, and an information system.
Per unit quantities, like percentage quantities, are actually fractional quantities of a reference quantity. To use the per unit method, we normalize all the system impedances and admittances within the network under consideration to a common base. Series impedance paramater calculation examples pdf series impedance paramater calculation examples mathcad series impedance paramater calculation examples mathcad prime calculating average height of conductors and representing transposition pdf. Short circuit calculations per unit and symmetrical.
Or in the other words, per unit is a scaling system to make calculation process in analyzing an electrical network system easier, b. The flood depth is 2 feet and the freeboard is 1 foot, which yields a dfe depth of 3 feet. Per unit system and symmetrical components are used for many short circuit calculations. This relatively simple, yet comprehensive format adds greatly to the use of the hand. How to do not so simple form calculations pdf help. Conversion chart from old weight 64ths and old weight carats to new metric on last. Per unit calculations a key problem in analyzing power systems is the large number of transformers. Activity based costing questions and answers prepared by. Perunit and primarysecondary calculations perunit basics a perunit value is the actual value of some quantity divided by the base value of that quantity. Introduction to cost modeling, template overview for. Per unit and symmetrical components electrical power.
The per unit system overview page 1 of 6 overview the per unit system is based on the formula shown in equation 1. Hvac cooling load calculations and principles sensible heat gain is the energy added to the space by conduction, convection andor radiation. Use the perunit pu system to simplify electrical power system simulation calculations and. Then, the real numbers of impedances and voltages can be substituted into the perunit calculation definition to get the answers for the perunit system. By dragging the sliders to the right and below well adjust the speed and the acceleration of the motor. Fault calculation problems typically deal wit power sources. The per unit system is a method of expressing quantities in an electrical system e. The pu system of calculations was more prevalent in the past years. The unit cost for c is 7% lower under abc when compared to traditional costing. Assume that no current is flowing in the network, so that all generator and motor voltages are. The first thing to do is to enter the steps per unit we found in our calculation.
It may or may not correlate with existing or proposed billing practices. Power system analysis lectures examples on reactance diagram and pu calculation. The scope of the analysis is determined by the denominator. Voltage bases are related by transformer turns ratios. Ppt transformers, per unit calculations powerpoint. Only programs with a common denominator can be compared. The per unit system permits multiplication and division in addition to addition. These have a lot of importance as per unit quantities of parameters tend to have similar values even when the system voltage and rating change drastically. The per unit system also makes the calculation easier as all the values are taken in the same unit. Singlephase per unit system advantages of the per unit system.
Dividing a system element by its per unit base value gives the per unit value of the element, for example. Learn how to more easily use positive, negative and zero sequence components and draw zero sequence diagrams. By adding capacitors kvar generators to the system, the power factor is improved and the kw capacity of the system is increased. British thermal unit btu joule j 1 055 british thermal unit per hour btuh watt w 0. The primary task for the transmission system is to transmit energy from generation areas to load areas. A cost per unit of outcome can address differences in effectiveness across programs.
However, due to sudden external or internal changes in the system, this condition is disrupted. In this instance it is possible to convert the unit. 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. In many respects the method is similar to the use of percentage values. Several examples of working with per unit are demonstrated in this crisp clear presentation. Calculation of esdd02006 system fault levels issue no. The indifference point is the level of volume at which total costs, and hence profits, are the same under both cost structures. Follow the above procedure and solve the following problems. 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. The basic equation for calculating a per unit value is shown below. List all cost items that vary with each additional unit soldserved. Each fixture has its own singular loading effect on the system, which is determined by the rate of water supply required, the duration of each use, and the frequency of use.
A common threephase voltampere base is used throughout the system, where sbase,3. Shaft speed scaling is done based on following relation. This makes the per unit value of either voltage or current to be around 1. For example, one of the two definitions of bias stated in ansi n. A calculation can be run to determine when this payoff will be. Introduction to cost modeling, template overview for performers. The base power may be the rating of a single piece of.
The unit of flow in north america, at least in the pump industry, is the us gallon per minute, usgpm. When they say 5 meters, you pull out your calculator and convert to feet and inch. Original circuit 8 per unit example, contd same circuit, with values expressed in per unit. 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. This handout presents basic concepts and calculations pertaining to the most common data types. The basic equation for calculating a perunit value is shown below. Besides being taught in higher education, it is quite commonly used by engineers in the power industry. Per unit system explaination with solved example electrical. The cost per unit of output is valid when the two programs being compared are equally effective.
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