Topic 2 Basic Principle EET 305 Power System

Topic 2 Basic Principle EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 1

Introduction • Electricity is a basic part of nature and it is one of our most widely used forms of energy. • Many cities and towns were built alongside waterfalls (a primary source of mechanical energy) that turned water wheels to perform work. • Before electricity generation began over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 2

Introduction • Beginning with Benjamin Franklin's experiment with a kite one stormy night in Philadelphia, the principles of electricity gradually became understood. The greatest experiment’s How the experiment worked ? When a storm cloud passed over Franklin's kite the negative charges in the cloud leaked onto his kite, his kite string, his key, and a Leyden jar attached to the key by a thin metal wire. Franklin however, was unaffected by the negative charges because he was holding a dry silk string which insulated him from the charges on the key. When Franklin reached out his knuckle to touch the key he received a shock, because the negative charges in the key were so strongly attracted to the positive charges in his body that a spark jumped from the key to his hand. Franklin's experiment successfully showed that lightning was actually static electricity. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 3

Introduction • Electricity is always energy produced by converting some other form of energy (heat, mechanical motion, solar light, moving wind, tidal, geothermal, nuclear reaction, etc) into electric power. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 4

Introduction • Electricity has 2 advantages over other forms of energy that have led to its wide popularity. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 5

Introduction • Demand of electric power will every year progressively increase. • For example in Malaysia, The maximum demand of the grid system in Peninsular Malaysia increased by 4. 0% from 12, 493 MW in the year 2005 to 12, 990 MW recorded on 23 August 2006. • The installed generation capacity also increased from 17, 623 MW in the year 2005 to 18, 323 MW, subsequent to the commissioning of Unit 1 coal plant of 700 MW at Tanjung Bin Power Station in Johor in September 2006. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 6

Introduction • Maximum Demands and Installed Generation Capacity in Peninsular Malaysia for the First Half Year of 2007 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 7

Introduction • Maximum Demands and Installed Generation Capacity in Peninsular Malaysia in the Year 2006 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 8

Introduction • Maximum Demands and Installed Generation Capacity in Sarawak in the Year 2006 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 9

Introduction • Maximum Demands and Installed Generation Capacity in Sabah for West Coast Grid and East Coast Grid in the Year 2006 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 10

Review of Electrical System Concepts • Electrical engineers job responsibilities could be divided into four categories: § The production of electrical energy § The transmission of electrical energy § The application of electrical energy § The control of electrical energy EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 11

Review of Electrical System Concepts • Four constituent parts of a basic electrical system 1. The Source ü To provide the energy for the electrical system 2. The Transmission System ü To transfer the energy from the source to the load such as cables or wires as the transmission line 3. The Control Apparatus ü To control the energy that provided by the source ü Simplest example is switch, to permits or interrupts the energy to flow 4. The Load ü To utilize the electrical energy supplied by the source ü Consume energy EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 12

System Voltages • Voltages Level in Electrical Power System Voltage Level 120/240 V up to 1 k. V Low up to 69 k. V Medium up to 230 k. V High up to 765 k. V Extra High EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 13

System Voltages • Supply standards variation between continents by two general standards have emerged as the dominant ones: In Europe In North America IEC governs supply standard IEEE/ANSI governs supply standards The frequency 50 Hz The frequency 60 Hz LV voltage is 230/400 V LV voltage is 110/190 Source: Practical Power Distribution for Industry , De Kock, J. IDC Technologies 2004 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 14

System Voltages • The most-common LV supplies are within the range 120 V single phase to 240/415 V 3 -phase 4 -wires. • Voltage of local LV network an their associated circuit diagrams EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 15

System Voltages • Voltage of local LV network an their associated circuit diagrams EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 16

System Voltages • Circuit Diagrams EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 17

Per-Unit Method • The per-unit system is a widely system of normalization. Being familiar with it is essential to functioning in the world of electric power engineering. • What is per-unit – The per-unit system is a way to transform the numerical quantities (voltages, currents, powers, and impedances) to gain certain advantages while maintaining the basic relations between them (Ohm’s laws). – The per unit system is very similar to the percent system, except that when percentage quantities are to be multiplied or divided additional factors of 100 must be brought in which are not in the original equations. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 18

Per-Unit Method • Some Of Advantages Of Per-unit System – It gives A clear idea of relative magnitudes of various quantities such as voltage, current, power and impedance. – The per unit impedance of equipment of the same general type based on their own rating of the equipment. Whereas their impedance in ohms vary greatly with the rating. – The factors of √ 3 and 3 are eliminated in the per unit system thus the circuit laws are valid in per unit systems. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 19

Per-Unit Method • Some Of Advantages Of Per-unit System – The per unit value of impedance, voltage and current of a transformer are the same regardless of whether they are referred to the primary or the secondary side. This is greatly advantage since the different voltage level disappear and the entire system reduces to a system of simple impedance. – The per unit systems are ideal for the computerized analysis and simulation of complex power system problem. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 20

Per-Unit Method • The basic per-unit scaling equation is • S, V , I and Z are expressed as a fraction of the actual or base value EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 21

Per-Unit Method • Calculation for Single Phase Systems – If SB and VB are the selected base quantities of power (complex, active or reactive) and voltage, then – Base current – Base Impedance EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 22

Per-Unit Method • Calculation for Single Phase Systems – Voltages and power are usually expressed in k. V and MVA, thus it is usual to select a MVAB and k. VB and to express – Base current in k. A – Base Impedance in Ω • In these expressions, all the quantities are single phase quantities. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 23

Per-Unit Method • Calculation for Single Phase Systems – The extension to other related variables is routine. For example, – In case of impedance, EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 24

Per-Unit Method • Calculations for Three Phase Systems – In three phase systems the line voltage and the total power are more important than the per phase quantities. It is thus usual to express base quantities in terms of these. – If S 3φB and VLLB are three phase base power and line to line voltage respectively, – Base current – Base Impedance EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 25

Per-Unit Method • Calculations for Three Phase Systems – In terms of MVA 3φB and k. VLLB – Base current in k. A – Base Impedance in EET 305 Power System Fundamental - Mohd Rafi (So. ESE) Ω 26

Per-Unit Method • Calculations for Three Phase Systems – Thus in three phase, the calculations of per unit quantities becomes EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 27

Per-Unit Method • Calculations for Three Phase Systems – P and Q have the same base as S, so that – Similarly, R and X have the same base as Z, so that – The power factor remains unchanged in per unit. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 28

Per-Unit Method • Conversions From One Base To Another – It is usual to give data in per unit to its own rating. – As different components can have different ratings, it is necessary to convert all quantities to a common base to do arithmetic operations. – Additions, subtractions, multiplications and divisions will give meaningful results only if they are to the same base. This can be done for three phase systems as follows. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 29

Per-Unit Method • Conversions From One Base To Another – The conversion from one base to another can be done for three phase systems as follows EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 30

Per-Unit Method • Per Unit Quantities Across Transformer – Although the power rating on either side of a transformer remains the same, the voltage rating changes, and so does the base voltage across a transformer – This is like saying that full or 100% (or 1 pu) voltage on the primary of a 220/33 k. V transformer corresponds to 220 k. V while on the secondary it corresponds to 33 k. V. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 31

Per-Unit Method • Per Unit Quantities Across Transformer – While a common S 3φB can be selected for a power system, a common VLLB must be chosen corresponding to a particular location and changes in proportion to the nominal voltage ratio whenever a transformer is encountered. – Assuming Ideal transformer, a is define as turns ratio – The current base changes inversely as the ratio. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 32

Per-Unit Method • Per Unit Quantities Across Transformer • For a transformer with turns ratio NP: NS, base quantities change as follows. Primary Base Secondary Base Power (S, P and Q) SB SB Voltage (V) V 1 B∙(NS/NP)=V 2 B Current (I) SB/√ 3 V 1 B∙(NP/NS)=SB/√ 3 V 2 B V 1 B 2/SB∙(NS/NP)2=V 2 B 2/SB Quantity Impedance (Z, R and X) EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 33

Per-Unit Method • Example 1 • Figure 1 (a) Circuit with elements in SI units. • Figure 1 (b) Circuit with elements in per-unit. Figure 1 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 34

Per-Unit Method • Example 1 • (a) Solve for Z, I, and S at Port ab in Figure 1 (a) • (b) Repeat (a) in per-unit on bases of VB=100 V and SB=1000 V. Draw the corresponding per unit circuit. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 35

Per-Unit Method • Example 1 Solution (a) Solution for Z, I, and S at Port ab in Figure 1 (a) EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 36

Per-Unit Method • Example 1 Solution • (b) Answer in per-unit on bases of VB=100 V and SB=1000 V EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 37

Per-Unit Method • Example 1 Solution • (b) Answer in per-unit on bases of VB=100 V and SB=1000 V EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 38

Per-Unit Method • Example 1 Solution • (b) Converting result in (b) into SI unit • It shows that the results of (a) and (b) are identical. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 39

Per-Unit Method • Example 2 • A 200 MVA, 13. 8 k. V generator has a reactance of 0. 85 pu and is generating 1. 15 pu voltage. • Determine: - (a) the actual values of the line voltage, phase voltage and reactance, and (b) the corresponding quantities to a new base of 500 MVA, 13. 5 k. V. EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 40

Per-Unit Method • Example 2 Solution • (a) Line voltage Phase voltage Reactance EET 305 Power System Fundamental - = pu voltage x Base line voltage = 1. 15 x 13. 8 k. V = 15. 87 k. V = pu voltage x Base phase voltage =1. 15 x(13. 8 k. V/√ 3) = 9. 16 k. V = pu reactance x( Base line voltage 2/ MVA) =0. 85 x ( 13. 8 k. V 2/200 MVA ) = 0. 809 Ω Mohd Rafi (So. ESE) 41

Per-Unit Method • Example 2 Solution • (b) Line voltage pu (2) Phase voltage pu (2) Reactance pu (2) = Vpu. LL(1) x (VBLL(1) / VBLL(2)) = 1. 15 x (13. 8 k. V /13. 5 k. V) = 1. 176 pu = Vpu. LL(1) x (VBφ(1) / VBφ(2)) =1. 15 x (13. 8 k. V /√ 3) / (13. 5 k. V/√ 3) = 1. 176 pu = Xpu(1) x (VLLB(1)/VLLB(2))2 x(SB(2)/SB(1)) =0. 85 x (13. 8 k. V/13. 5 k. V)2/(500 MVA/200 MVA) = 0. 355 pu EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 42

Per-Unit Method • Example 3 • Draw an impedance in per unit diagram for the system whose one-line diagram is shown in Figure 2 below EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 43

Per-Unit Method • Example 3 Data for the system is: – – – – – G 1: 50 MVA, 13. 8 k. V, X=0. 15 pu G 2: 20 MVA, 14. 4 k. V, X=0. 15 pu M : 20 MVA, 14. 4 k. V, X=0. 15 pu T 1 : 60 MVA, 13. 2 k. V/161 k. V, X=0. 10 pu T 2 : 25 MVA, 13. 1 k. V/161 k. V, X=0. 10 pu T 3 : 25 MVA, 13. 2 k. V/160 k. V, X=0. 10 pu (I changed voltage rating on LV side of T 2 and HV side of T 3) Line 1: 20+j 80 ohms Line 2: 10+j 40 ohms Line 3: 10+j 40 ohms Load: 20+j 15 MVA at 12. 63 k. V EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 44

Per-Unit Method • Example 3 Solution • We begin by choosing the system power base as S 3φB=100 MVA. • We must also choose the voltage base in one section of the system. We will select 161 k. V in Section D. • Now we compute the voltage bases in the other three sections of the system. – Section A: – Section B: – Section C: EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 45

Per-Unit Method • Example 3 Solution • Next convert the given per-unit impedances for G 1, G 2, M, T 1, T 2, and T 3 into per-unit impedances on new bases. • G 1: • G 2: • M: EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 46

Per-Unit Method • Example 3 Solution • Next convert the given per-unit impedances for G 1, G 2, M, T 1, T 2, and T 3 into per-unit impedances on new bases. • T 1: • T 2: • T 3: EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 47

Per-Unit Method • Example 3 Solution • Note that the last calculation (for T 3) could have been done as follows: • T 3: • Next, let’s per-unitize the lines. The line impedances are all in ohms, we need to find the impedance base for Section D EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 48

Per-Unit Method • Example 3 Solution • Then, per-unitize the lines L 1, L 2 and L 3 EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 49

Per-Unit Method • Example 3 Solution • Finally, we need to compute the load, assume it use a series combination. • Next, compute ZB at section C, EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 50

Per-Unit Method • Example 3 Solution • Compute the per unit impedance as • Per-Unit impedance diagram EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 51

General Layout of the System EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 52

General Layout of the System • One line diagram EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 53

General Layout of the System Large Generation Stations Overview Of The Electricity Infrastructure Bulk Transmission 230 -750 k. V Sub transmission 69 -169 k. V Primary Distribution 4 -36 k. V Secondary Distribution 120/240/415 V EET 305 Power System Fundamental - Mohd Rafi (So. ESE) 54

General Layout of the System • North American versus European distribution layouts. North American Layout EET 305 Power System Fundamental - Mohd Rafi (So. ESE) European Layout 55