Shaft speed scaling is done based on following relation. 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. The basic equation for calculating a perunit value is shown below. For example, a transient voltage reaching a maximum of 1. In many respects the method is similar to the use of percentage values. To use the per unit method, we normalize all the system impedances and admittances within the network under consideration to a common base. The swedish transmission system consists of approximately 15327 km power lines, and there are 16 interconnections to other countries. 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 and symmetrical components are used for many short circuit calculations. The per unit system also makes the calculation easier as all the values are taken in the same unit. More importantly, while c looks like it is making a loss under traditional costing, abs tells a different story. The base values for each singlephase transformer are first calculated.
Power system analysis lectures examples on reactance diagram and pu calculation. This data will, of course, be different for each of the different types of calculations. Per unit example solve for the current, load voltage and load power in the circuit shown below using per unit analysis with an sb of 100 mva, and voltage bases of 8 kv, 80 kv and 16 kv. For this purpose, an edu is the level of service in gallons per day for an average residential dwelling. Voltage bases are related by transformer turns ratios. Although power system analysis is now done by computer, results are often expressed as per unit values on a convenient system wide base. Training program costing example university of washington. The standard produces fault current results for an unloaded network, that is the results do not include load current and the prefault. Per unit system allows the system operator to overlook abnormalities in the system easily. 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. Here are the main reasons for using the per unit system. Define four quantities in per unit of their respective base values. Follow the above procedure and solve the following problems.
Although powersystem analysis is now done by computer, results are often expressed as perunit values on a convenient systemwide base. 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. From now on i will just use gallons per minute or gpm. Specify the new voltage base in the region where calculations should begin. Then, the real numbers of impedances and voltages can be substituted into the perunit calculation definition to get the answers for the perunit system.
These normalized impedances are known as per unit impedances. Source impedance for fault analysis is furnished in per unit. Predefined, simplified field notation, or custom calculation script. The scope of the analysis is determined by the denominator. Short circuit calculations per unit and symmetrical. Per unit system is the ratio between the actual value in any unit and the base or reference value in the same unit. The generators perunit voltage is the transmission lines perunit impedance is the other base quantities are 10 0 41. In this instance it is possible to convert the unit. For example, a 1,000 kva transformer with an 80% power factor. Equations used for finding base quantities of impedance, current, and power are shown in table 1, where. This class is loaded with many in class examples and problems for a hands on. Use the perunit pu system to simplify electrical power system simulation calculations and.
Memory storage calculations professor jonathan eckstein adapted from a document due to m. Determine the voltage base for all other areas in the circuit by adjusting by the. The per unit system was developed to make manual analysis of power systems easier. By adding capacitors kvar generators to the system, the power factor is improved and the kw capacity of the system is increased. The generators per unit voltage is the transmission lines per unit impedance is the other base quantities are 10 0 41. When they say 5 meters, you pull out your calculator and convert to feet and inch. The examples include bathroom fixtures, kitchen sinks, laundry trays and washing machines.
Calculation of system fault levels sp energy networks. British thermal unit btu joule j 1 055 british thermal unit per hour btuh watt w 0. Consider, for example, a threephase twowinding transformer with these. Using a 8kv, 100mva base in the transmission lines, draw the positive and negative sequence per unit diagrams. Auto calculated as the sum of all the costs per unit. In the metric system, flow is in liters per second ls or meters cube per hour m3h. The bfe is 9 feet and existing ground elevation is approximately 7 feet. The first thing to do is to enter the steps per unit we found in our calculation. Calculation of equivalent dwelling units edus the purpose of this worksheet is to determine edus for rd funding determinations only. 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. A common threephase voltampere base is used throughout the system, where sbase,3. 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. Per unit system explaination with solved example electrical.
None of these subsystems is of much use as a single, independent unit. For example, one of the two definitions of bias stated in ansi n. Ee 423 fault analysis notes university of moratuwa. The cost per unit of output is valid when the two programs being compared are equally effective.
Per unit and symmetrical components electrical power. Per unit systems is an important concept in power system analysis. The value of n, called the scaling exponent, depends on the physical result to be scaled. Production model for bottomup calculation of labor, material. 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. Vin per unit vin kvv base in kv where the base value is a reference value for magnitude. 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. Per unit quantities, like percentage quantities, are actually fractional quantities of a reference quantity. Auto calculated as cost per unit x quanity since these are variable costs, input the cost required to produce one unit of the productservice. The perunit system is a method of expressing quantities in an electrical system e. Well use the metric calculations above as base for this setup so 200 steps per unit it is. Introduction to cost modeling, template overview for. 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.
List all cost items that vary with each additional unit soldserved. Learn how to more easily use positive, negative and zero sequence components and draw zero sequence diagrams. Jul 21, 2015 per unit system and symmetrical components are used for many short circuit calculations. 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. 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. Per unit analysis understanding the per unit system and its uses. Per unit system explaination with solved example free download as powerpoint presentation. The normalization typically follows transformer ratings. When values are expressed in pu, the comparison of electrical quantities with their normal values is straightforward. Equipment impedances can be easily estimated since their per unit impedances lie within a relatively narrow range. So much so, it shows up in all exams pertaining to power. Assume that no current is flowing in the network, so that all generator and motor voltages are. More specifically, the per unit method of calculation is often used in the calculation of short circuit currents. Total variable costs auto calculated as the sum of all variable costs.
Threephase per unit system the same advantages apply to a threephase system if the following rules are obeyed. Introduction to per unit calculations pages 1 11 text. Just imagine you are in the united states and need to compare measurements with someone elsewhere in the world. Perunit and primarysecondary calculations perunit basics a perunit value is the actual value of some quantity divided by the base value of that quantity. Pick a voltage base for each different voltage level, vb. Convert actual values to per unit note, per unit conversion on affects magnitudes, not the angles. Activity based costing questions and answers prepared by. 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. Any per unit impedance will have the same value on both the primary and secondary of a transformer and is independent of voltage level. Besides being taught in higher education, it is quite commonly used by engineers in the power industry. The perunit system was developed to make manual analysis of power systems easier. Singlephase per unit system advantages of the per unit system.
Information for a small power system is shown below. Hvac cooling load calculations and principles sensible heat gain is the energy added to the space by conduction, convection andor radiation. Equipmentmachinerytooling totals from per item price and number of stations estimated floor space needed from equipment sizes. However, the availability of computer programs for system analysis has diminished to some extent the need for the pu system of calculations.
The per unit system overview page 1 of 6 overview the per unit system is based on the formula shown in equation 1. The flood depth is 2 feet and the freeboard is 1 foot, which yields a dfe depth of 3 feet. 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. Design of potable water plumbing systems ced engineering. This relatively simple, yet comprehensive format adds greatly to the use of the hand. It may or may not correlate with existing or proposed billing practices. The pu system of calculations was more prevalent in the past years. The unit of flow in north america, at least in the pump industry, is the us gallon per minute, usgpm. 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. The base power may be the rating of a single piece of. 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. This makes the per unit value of either voltage or current to be around 1.
Or in the other words, per unit is a scaling system to make calculation process in analyzing an electrical network system easier, b. 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. Marlap not es that such a deviation, even if it is large, may not give a reliable indica. The unit cost for c is 7% lower under abc when compared to traditional costing. Per unit system per unit system is when we normalize the voltage and current at each location. Iyigun an important issue in the construction and maintenance of information systems is the amount of storage required. Calculation of esdd02006 system fault levels issue no. 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. Here are the main reasons for using the perunit system. Several examples of working with per unit are demonstrated in this crisp clear presentation. Singlephase per unit system university of texas at.
Transformers can be replaced by their equivalent series impedances. Generally base values of power and voltage are chosen. Per unit calculations a key problem in analyzing power systems is the large number of transformers. This handout presents basic concepts and calculations pertaining to the most common data types. Dividing a system element by its per unit base value gives the per unit value of the element, for example. The standard produces fault current results for an unloaded network, that is the results do. Calculate all per phase circuit values in per unit with respect to the new bases just specified.
A cost per unit of outcome can address differences in effectiveness across programs. The volume per unit of mass in cubic feet per pound. How to do not so simple form calculations pdf help. Electric utility data is also often provided in terms of per unit and symmetrical components. However, due to sudden external or internal changes in the system, this condition is disrupted. Only programs with a common denominator can be compared. Matlab simulink student software hardware support file exchange. 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. Original circuit 8 per unit example, contd same circuit, with values expressed in per unit. A calculation can be run to determine when this payoff will be.
Fault calculation problems typically deal wit power sources. Conversion chart from old weight 64ths and old weight carats to new metric on last. By dragging the sliders to the right and below well adjust the speed and the acceleration of the motor. The basic equation for calculating a per unit value is shown below. Introduction to cost modeling, template overview for performers. Jul 02, 2006 select the desired calculation option. Then a person who is 40 years old is half of the base unit. 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. Some times per unit values are available for a given base kv, but the problem being solved is using a different base.
1019 1417 756 1194 816 552 259 93 1389 851 815 1441 893 950 294 766 830 1216 818 1510 1037 764 817 520 1007 272 1419 1450 830 1111 1165 577