EE587_ Ch4_sp10

# EE587_ Ch4_sp10 - EE 587 Electric Power...

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: EE 587 Electric Power Distribution/Utilization Dr. M. Safiuddin, Research Professor Department of Electrical Engineering University at Buffalo [State University of New York] EE 587_Sp 10 1 EE 587 Electric Power Distribution/Utilization TEXT BOOK: ANSI/IEEE -Std. 141-1993 [ The Red Book]; Published by Institute of Electrical & Electronics Engineers, New York. Lecture Topics: 1. 2. 3. System Protection I Sources of fault currents, Fundamentals of fault current calculations, Restraints of simplified calculations, Example case studies. [Ch. 4] EE 587_Sp 10 Introduction, System Planning & Design Course orientation, Overview, Definitions, Planning guide for the supply and distribution system [Ch 2] Voltage Considerations Voltage control, Voltage selection, Effects of voltage variations on low and medium voltage equipment, voltage quality considerations.[Ch. 3] 2 1 System Protection I [Ch. 4] ! " &' # ! \$ \$ \$ % \$ EE 587_Sp 10 3 ( % ) \$ * \$ + 4.5 Detailed procedure Step 1: Step 2: Step 3: Step 4: Prepare system diagrams Collect & convert impedance data Combine impedances Calculate short-circuit currents First-cycle network; Interrupting network Time-delayed relaying devices EE 587_Sp 10 4 2 % /0 10 , - . 2 4 456 34 7 8 - EE 587_Sp 10 5 Background- Circuit Analysis ) + :5 :5 5 ; ::5 :::5 < < EE 587_Sp 10 6 9 ∝∝+ ∝+ , , . . 3 Equivalent circuit > >=" 0 >= = EE 587_Sp 10 7 Electric Machine Fundamentals MAGNETIC FLUX (O) FLUX DENSITY (B) N l S I APPLIED CURRENT N S RESULTANT FORCE EE 587_Sp 10 8 4 Electric Machine Fundamentals FLUX DENSITY (B) A MAGNETIC FLUX (O) TORQUE RESULTANT FORCE N S N S I RESULTANT FORCE EE 587_Sp 10 9 Electric Machine Fundamentals ? 8# : \$ ? # @ \$ ? ! ? ! EE 587_Sp 10 10 # @ @ 5 Sources of Fault Currents 0 A : ) ! & * & ! \$ ! \$ * EE 587_Sp 10 11 Sources of Fault Currents A A &' ! # B EE 587_Sp 10 12 6 Synchronous Machines: ?A ?# ?% + - % , ? ? ? ! : \$ % ! &' ( !* ) " # " # : EE 587_Sp 10 # 13 EE 587_Sp 10 14 7 P. C. Sen, Principles of electric machines and power electronics. EE 587_Sp 10 15 EE 587_Sp 10 16 8 Source: P. C. Sen, Principles of electric machines and power electronics. isc = 2 Ef Xd + Ef ′ Xd − Ef Xd e −t ′ Td 0 + Ef ′ X d′ − Ef ′ Xd e − t ′′ Td 0 sin ωt + I dc 0e −t Ta EE 587_Sp 10 17 Induction Machines ?& ! ?! C ? ! DE ?! ! EE 587_Sp 10 18 9 Electric utility systems F & ! \$ ! ! * ! \$ EE 587_Sp 10 19 Adjustable speed motor drive systems , \$ ! . ! C ! &! - EE 587_Sp 10 20 10 ; * G ( , H 0I> . ! \$ \$ 0 > % J 8 ! \$ EE 587_Sp 10 21 Ch. 4.3- Fundamentals of calculations Maximum values are used for selecting interrupting devices of adequate short-circuit ratings. Minimum values are used to establish sensitivity of protective relays. Minimum values are sometimes estimated as fractions of maximum values Types of short-circuits Three-phase short circuit is frequently the only one considered since it generally results in maximum value and simplifies calculations. Line-to-line short-circuit currents are approximately 87% of three-phase short-circuit currents. EE 587_Sp 10 22 11 Types of short-circuits…cntd. \$ ! \$ \$ ! \$ \$ "L K EE 587_Sp 10 23 Types of short-circuits & \$ ! 9 ! \$ 47 M ! 41 75 4 75 4 4 " "7 45 44 " 7 " 45 44 "5 4 4( " 1 7 15 EE 587_Sp 10 24 12 Basic equivalent circuit ! G * ! ! , =C H 5==I√ (. 5 EE 587_Sp 10 25 Basic equivalent circuit % ' ! \$!\$ ! ! \$ ! ! J \$ , 45 . "7 EE 587_Sp 10 26 \$ \$ !* ! 13 Basic equivalent circuit F , . M 4 ! ! \$ ! \$ EE 587_Sp 10 27 The differential equation: A - = 2 I 6 + 2 H0 N 6 9 ω 2 6 2 H &2 α 6 6 α I = = α H N, = , & 6 .N & 6 2I 2α α α &6 2I &6 2I \$ & 6 +& 6 α . H 0 2N 2 ω ω α N2 N+ & 6 α H0 = 62 2α N +&2 α H 4 = 66 EE 587_Sp 10 28 14 \$ &2 α H 4 6 \$ = 2I=6 + =α N + H 4 , & 6 . H0 2I 2I=6 + + α H 2I=6 ω ω ω & 6 H2 2I 0I=6 \$ &2 H 2 6 0I=6 2I=6 + 8 9 D Hω = EE 587_Sp 10 29 ! E A (t ) = ωL e \$ ( R )t L ( R ωL sin ω t − cos ω t ) 2 R ωL + A1 +1 E i (t ) = ωL 1 R 2 ( +1 R ωL sin ωt − cos ωt ) R 2 + A1 e − ( R / L )t ωL ωL +1 EE 587_Sp 10 30 15 Sin φ = 1 R ωL 2 +1 R L Cos φ = ( R / ωL ) R ωL 2 +1 ø L Sin (A –B) = Sin A Cos B - Sin B Cos A EE 587_Sp 10 31 ! iss = E ωL 1 R ωL 2 Sin (ω t − Tan −1ϕ ) +1 + + * . EE 587_Sp 10 32 16 4.4 Restraints of simplified calculations 4.4.1 Impedance elements– Z = R + j (XL-XC) 4.4.2 Switching transients -- I = 4.4.3 Decrement factor 4.4.4 Multiple switching transients 4.4.5 Practical impedance network synthesis 4.4.6 Other analytical tools 4.4.7 Respecting the imposed restraints 4.4.8 Conclusions EE 587_Sp 10 33 E Sin (ω t ) + I dc e( − Rt ) / L jωL 4.4 Restraints of simplified calculations , "& ( ! & ! * 4( K 44 K EE 587_Sp 10 34 .! , ! . 6! \$ ! 4 4( 7 / \$ < ! 2 ! * 17 4.4 Restraints of simplified calculations /; O \$ ! ! EE 587_Sp 10 35 ! 4.4 Restraints of simplified calculations 7. Analysis based on simplified per-phase line-to-neutral balanced system concepts require that: a) The power system components shall be of symmetrical design pattern b) The electric loading imposed on the system shall be balanced and symmetrical. EE 587_Sp 10 36 18 4.4.8 Conclusions ! \$ !0 ! ! < < ! + ! & ! ' EE 587_Sp 10 37 EE 587_Sp 10 38 19 4.5 – Detailed Procedure C <, \$ & 5& 5&! I# 9% "9 (- ! 9 9B . \$ \$ EE 587_Sp 10 39 4.5 – Detailed Procedure "9 B actual quantity base quantity per − unit quantity (voltage , current , etc .) = base current (amperes) = base kVA(1000) 3 (base V ) base MVA(106 ) 3 (base V ) base V 3 (base A) = = base kVA 3 (base kV ) base MVA (1000) 3 (base kV ) = = base impedance (ohms) = (base V ) 2 base kVA(1000) = (base kV ) 2 (base kV ) 2 = base kVA base MVA EE 587_Sp 10 40 20 4.5 – Detailed Procedure Step 2: Collect & convert impedance data per − unit impedance Zpu = actual impedance in ohms (base MVA) (base kV) 2 = actual impedance in ohms (base kVA) (base kV) 2 (1000) per − unit reactance (base kVA) kVA rating X pu = EE 587_Sp 10 41 4.6 – Example Case Study & & & ! EE 587_Sp 10 42 21 ...
View Full Document

## This note was uploaded on 02/16/2011 for the course EE 587 taught by Professor Dr.mohammedsafiuddin during the Spring '11 term at SUNY Buffalo.

Ask a homework question - tutors are online