Select rated values as base values, usually rated power in mva and rated phase voltage in kv. The determination of per unit values is not the end objective of a study. If so, share your ppt presentation slides online with. Power factor per unit calculations is the property of its rightful owner. Perunit and primarysecondary calculations perunit basics a perunit value is the actual value of some quantity divided by the base value of that quantity. Agitation scaleup calculation does the scaleup from smaller to larger scale based on criteria like equal tip speed, power per unit volume, equal reynolds number, equal shaft speed. The generators perunit voltage is the transmission lines perunit impedance is the other base quantities are 10 0 41. The basic equation for calculating a per unit value is shown below. The perunit system was developed to make manual analysis of power systems easier.
It is necessary that the proper impedance be used to represent the primary system. The calculations using the perunit system are simplified. Fault calculations are simplified very substantially if they are performed using the perunit system and normalising all electrical quantities relating to the fault in per. Vin per unit vin kvv base in kv where the base value is a reference value for magnitude. Per unit fault calculations is a method whereby system impedances and quantities are normalised across different voltage levels to a common base. By removing the impact of varying voltages, the necessary calculations are simplified. Include base values for all data given in per unit. Table a1 provides definitions of base values for the perunit system, in which the rat ed values of the wind generator or power converter are selected as the base. Per unit system explaination with solved example electrical. 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 such analysis, the power base is often chosen as 100 mva and bases for current and impedance are calculated using the power and voltage base.
Experiment 6 per unit calculations, impedance diagrams. Fundamental to any power system analysis is the knowhow of per unit systems. 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. Energy, power, and photons energy in a light wave why we can often neglect the magnetic field poynting vector and irradiance the quantum nature of light photon energy and photon momentum. Per unit pu systems are used by engineers to quantify equipment parameters in terms of their nameplate ratings. Per unit system explaination with solved example free download as powerpoint. This video explains the complications created by transformers and turns ratios in circuit analysis. 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.
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. Now consider the real power flow equation from eqs. In the most common usage for per unit calculation, the analysis of an entire power system, the nominal or nameplate voltage rating for each voltage level of the system is chosen as base voltage. Per unit analysis for single and three phase systems udemy.
Rather determined per unit values serve to assist in the calculation of other system values. In the above steadystate equation, time does not appear explicitly. V, i, z, and s, and then the base quantities for the other two are computed. Shortcircuit current calculations cooper industries. 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. When only one device transformer or motor is analyzed, its own ratings are used as the basis for perunit system. Calculations are simplified because quantities expressed as perunit do not change when they are referred from one side of a transformer to the other. Handbook of electric power calculations pdf drive electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. Per unit identities university of minnesota duluth. For each system parameter, perunit value is equal to the actual value divided by a base value. Calculations are simplified because quantities expressed as perunit do not. For each system parameter, per unit value is equal to the actual value divided by a base value. The treatment throughout the handbook is practical with very little emphasis on theory. The handbook of electric power calculations provides detailed stepbystep calculation.
The direction of flow will be from the higher voltage bus to the lower voltage bus. The eqn 1 show that the per unit impedance is directly proportional to base. These become useful when performing calculations across a power system where multiple voltage. Calculations are simplified because quantities expressed as perunit do not change when they are referred from one side of.
Similarly for motor3 you calculate same equation using equation 16 you will become. Electrical pe exam perunit an introduction youtube. The situation is the same here, except that we also must deal with speed or. Perunit and primarysecondary calculations power eng. Transformers can be replaced by their equivalent series impedances. The application of the perunit method simplifies these c.
By using per unit calculations that different voltage bases but the same powerbase are used in different transformer sections. Equipment impedances can be easily estimated since their per unit impedances lie within a. Lecture notes on fault detection and location in distribution systems, 2010. A single line diagram is diagrammatic representation of power system in which the components are represented by their. Introduction to per unit calculations pages 1 11 text. 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 per unit system is a method of normalizing system and equipment. With transformers, we need to convert the voltage magnitudes,impedances, currents, etc. So much so, it shows up in all exams pertaining to power. Calculate the per unit impedance for transformer t1. Singlephase per unit system advantages of the per unit system. The handbook of electric power calculationsprovides detailed stepbystep calculation procedures commonly encountered in electrical engineering.
In order to calculate the hydraulic pump flow rate q lmin, you must enter the following figures. Explain the requirements of planning the operation of a power system. To use the per unit method, we normalize all the system impedances and admittances. Therefore, the perunit power on the load is the actual power on the load is d the perunit power lost in the transmission line is the actual power lost in the transmission line. Perunit impedances of transformers are the same whether they are referred to the primary or secondary side, which makes calculations much simpler in multiple voltage level power systems. The motor is to be started by a manual starter, shown in fig. Per unit systems is an important concept in power system analysis. In the per unit representation, the equivalentin the per unit representation, the equivalent circuit of a transformer is a simple winding impedapeda cence z pu ww t e c tat o b a cith excitation branch ignored i i v v 2 pu 1 pu 2 pu z pu 1 pu. Impedance and its expression in perunit pu symmetrical fault current calculation systematic fault calculation with bus matrix asymmetrical. Singlephase per unit system university of texas at.
Power factor 1 for resistive loads such as resistance heaters, incandescant lights, stoves or other nonmotorized equipment. Source impedance for fault analysis is furnished in per unit. Equations used for finding base quantities of impedance, current, and power are shown in table 1, where. The manufacturers usually provide the impedance values in per unit. Then press p to calculate, this will be shown in the result box.
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