ELECTENG 731 Lecture 1 2015 Nirmal

ELECTENG 731 Power Systems Semester 1: 2015

Dr. Nirmal Nair (Course Coordinator) Office Hours: Fridays 2 - 3 pm during teaching weeks or by prior appointment ([email protected])

Power Systems Issues Worldwide Ageing Infrastructure in developed

economies

Emerging electricity reticulation in developing economies

Developing & integrating distributed/renewable energy sources

Changing Nature of load: leading to power quality issues

Skill shortage

Electricity as a commodity- Electricity Market

Security Reliability, blackouts, brownouts, islanding

NZ Power Systems Issues Immediate

Grid Upgrade (220 kV, 400 kV, HVDC) Skill shortage Wind energy Integration issues Electricity Market- Ancillary services market, FTR,

Demand Side Participation Public-Private Partnership of Generation (Now!)

Ongoing/Future

Distribution Power quality issues- Flicker, Voltage sags/dips, etc.

New protection philosophies (Smart Grid) Sustainability Efficiency Integrating non-firm Renewable Wind, Solar, Tidal Demand side Management MARKETS!!!! SECURITY!!!

Source: www. transpower.co.nz

NZ Power Systems Stakeholders

Generation Contact Energy Ltd Genesis Power Ltd Meridian Energy Ltd Mighty River Power

Ltd Todd Energy Ltd TrustPower Ltd

Distribution Line Companies 29 e.g. Vector, Powerco, Unison http://www.electricity.org.nz/

TRANSPOWER Owns & operates HV Grid System Operation (also Market)

Retailers Mercury Energy, Bay of Plenty

Electricity etc.

Bulk Users NZ Aluminium Smelters (NZAS)

13% (decreasing)

Consultants SKM, BECA, AECOM, PSC etc.

ELECTRICITY AUTHORITY

( Employment, Scholarships & Research)

Smart Grids The Technical Roadmap NIST Reference Framework

Todays Electricity

Power park

Hydrogen Storage

Industrial DG

Tomorrows Choices

Combined Heat and Power

Fuel Cell

e -

e -

Wind Farms

Rooftop Photovoltaics

Remote Loads

Load as a resource

SMES

Smart Substation

Fuel Cell

Future- Smart Grids

Consumer Engagement

Does Electricity Market mean anything to customers?

Petrol or electricity, which do customers will care more about in the future?

Who are communicating to customers and who should customers listen to?

UoA Power Systems Track

ELECTENG 309: Power Apparatus & Systems

ELECTENG 731: Power Systems (PS)

ELECTENG 703: Advanced Power Systems

ELECTENG 734: Power Electronics (PE)

ELECTENG 204: Engineering Electromagnetics 1

ELECTENG 202: Circuits & Systems

Overview, basics ELECTENG 101: Electrical & Digital Systems

Circuit laws-KCL, KVL, Thevenin, Norton, Superposition etc Network Analyses- Phasors, Loop, Nodal, Fourier, 3-phase etc

Magnetic material, fields & circuits; Faradays law, Amperes Law, 1ph Transformer

Analysis- Load Flow, Short-circuit, Stability Power quality

Electricity Markets, Protective relaying practices, DG/Renewable integration, PE Applications to PS

Machines- Synchronous, Induction Device- Transformers, Lines, Substation equipment

Relation of other courses to PS MM-1, MM-2,

MM-3 -ODE, DAE,

Matrix, LP etc.

Signal Processing

-PQ

Control -AVR, PSS,

Automation etc

Software -CIM, XML,

Visualization, DMS

Embedded Systems - SCADA

Power Electronics

-HVDC, FACTs, VSD etc.

Communications -GPS, SCADA, LAN, WAN etc.

ELECTENG 731 Semester 1- 2015

Department of Electrical and Computer Engineering University of Auckland

Lecturers Nirmal Nair (Course Coordinator) Patrick Hu TAs Lab: Jake Zhang, Piyush Verma, Yang Liu Assignment: Jake Zhang

Lab experiment compulsory (contents covered in the test or exam Qs) Two tests 15% each, final exam 60% 1 research assignment 6%, Labs 4% Faculty of Engineering Policy on Restricted Calculator apply

Power Systems

DigiSilent PowerFactory (EMS)

Commercial Used by transmission and

distribution companies. e.g. Transpower, Vector

MATPOWER Academic/Research

http://www.pserc.cornell.edu/matpower/

Please go to the website and: 1) Download the MATLAB based package for solving power flow and optimal

power flow problems

2) Read the user-friendly instruction to navigate and use the package for power flow

3) As the load flow/power flow lectures proceed attempt to solve some large-scale network problems using it

2015 Coverage ELECTENG 731

1. Power Systems Fundamentals & Load Flow Analysis (NN) Review of PS fundamentals; SCADA, EMS, DMS and Smart Grids Development of non-linear load flow equations; bus admittance matrix; classification of bus types; solution

techniques; voltage and power flow control; general algorithms for the solution of the load flow equations-the Gauss Seidel and Newton Raphson techniques; Approximations of Load flow

2. Fault Analysis (NN) Types of faults, use of Thevenins and Superposition Theorems for fault analysis; symmetrical faults and fault

levels; matrix methods for the analysis of faults in large order systems; asymmetrical fault conditions and the symmetrical components transformation technique for analysis; sequence networks and the application of the connection methods; matrix methods extended to the analysis of asymmetrical faults in larger order systems.

3. Power Systems Transient Stability Analysis (PH) Basic concepts of power systems stability; the dynamics of the synchronous machine in the network; the

electromechanical equations; coherent machines; a two machine equivalent system and representative swing equations; the swing equation for a single machine on infinite bus-bars; the Equal Area Criterion; critical clearing time and angle calculation.

4. Power Quality Analysis (PH) Power Quality (PQ) terms and definitions; Voltage Sags; Transient over-voltages; Harmonics; PQ

Benchmarking & Measurements.

2015 Schedule

Laboratory: Registration through course enrolment (Teaching Weeks 4/5 and 8/9; Mon & Friday 9-11am) UG4

Month Mon Tues Wed Thu Fri

1 March 2 3 NN 4 5 NN 6

2 March 9 10 NN 11 12 NN 13

3 March 16 17 NN 18 19 NN 20

4 March 23 24 NN 25 26 NN 27

5 Mar/April 30 31 PH 1 2 PH

3

April 6 7 8 9 10

April 13 14 15 16 17

6 April 20 21 PH Test 1 22 23 PH 24

7 April/May

27 Anzac 28 PH 29 30 PH 1

8 May 4 5 PH 6 7 PH 8

9 May 11 12 PH 13 14 PH 15

10 May 18 19 PH 20 21 PH Test 2 22

11 May 25 26 NN 27 28 NN 29

12 June 1 Queens Birthday

2 NN Assignment 3 4 NN 5

Learning Resources Class Handouts Tutorials Texts Review, Load Flow, Fault & Stability

John J Grainger and William D Stevenson Power Systems Analysis, McGraw Hill, 1994.

Power Quality Roger C Dugan, M F McGranaghan, S Santosa, H W Beaty Electrical Power Systems Quality, McGraw-Hill, 2nd Edition, 2002.

Learning Objective Recollect the background needed to facilitate understanding Power System Analysis What you have done before in other courses Course Notes for ELECTENG 101 :Electrical Engineering Systems Introduction to Electric Circuits, Power Systems & Electrical Machines Course Notes for ELECTENG 202: Circuits & Systems Foundations in Electric Circuit Analysis Course Notes for ELECTENG 204: Electromagnetics I 2014 Lecture material & text for ELECTENG 309: Power Apparatus & Systems Fitzgerald, Kingsley & Umans Electrical Machinery 6th Edition, McGraw Hill, 2003

Review

Line Modelling - Review (Not in course notes but from reference text book)

Reference Power System Analysis by Grainger & Stevenson

(Sections 6.7, 6.8 & 6.9) Long transmission line equivalent model Power flow through a transmission line Reactive compensation of transmission line

Quick Background Review of Transmission

line Modelling (ELECTENG 309)

Transmission Lines HVAC HVDC

Distribution Lines Overhead Cable

Transmission/Distribution Lines

(Optical Powerline Ground Wire)

NIMBY ?

BANANA ?

Not In My Back Yard

Build Absolutely Nothing Anywhere Near Anyone

Sub-transmission and Distribution line

Distribution line 13.8 kV

Transformer

240/120V line

Fuse and disconnector

Telephone line

Distribution Cable 13.8 kV

Line

Fuse cutout

Cables

Surgearrester

Fusecutout

Surgearrester

12.47 kVLine

Transformer

Consumer Service Drop Cable and transmission line junction

Electric Transmission Line Parameters

Electric Transmission Line Conductors Early days- Copper Nowadays Aluminum Types of Conductor

AAC AAAC ACSR ACAR

Code names for conductor Hen, Hawk, Pheasant, Bluebird etc.

Resistance Inductance

Capacitance

Conductance

- Where? - Neglected, Why?

Resistance [Section 4.2, Stevenson & Grainger] Most important cause of power loss in transmission line Effective Resistance

Direct current resistance

Resistivity, length and Cross-sectional area

Stranded conductor resistance is greater due to spiralling Increase with temperature (practically linear)

AC resistance

Non-uniformity of current distribution Skin- effect (non-uniform current density) Increase in resistance by skin effect- (Manufacturer tables)

= 2IconductorinlosspowerR

=AlR 0

1

2

1

2

tTtT

RR

++

=

Inductance of Conductor -Due to Internal Flux [Section 4.4]

IL =

== AtIdsHmmf .

= xx IdsH

xx IxH =2

IrxI x 2

2

=

mAtI

rxH x 22

=

222 mWb

rxIHB xx

==

mWbdx

rxId 22

=

mWbtdx

rIxd

rxd 4

3

2

2

2

==

mWbtIdx

rIxr

8204

3

int ==

mHX 7104 =

mWbtXI 7int 102

=

mHXL 7int 102

1 =

Assuming Uniform Current Density

Amperes Law

Flux density x metres From centre of conductor

Flux in tubular element

Flux linkages caused by flux In tubular element

Integrating from centre of Conductor to outside edge

Inductance of Conductor -Due to External Flux Linkages [Section 4.5]

IxH x =2

22 mWb

xIBx

=

mWbdx

xId2

=

mWbt

DDIdx

xID

D 1

212 ln22

2

1

==

mWbt

DDIX

1

2712 ln102

=

mH

DDXL

1ln102 2712

=

MMF around tubular element

Flux in tubular element

Flux linkages between 2 external points

Inductance due only to the flux Between two external points

Inductance of a Single-phase Two-wire line [Section 4.6]

mHX

rDL 7

11 10ln22

1

+=

+=

1

417

1 lnln102 rDXL

41

1

71 ln102

=r

DXL

114

1'1 7788.0 rrr ==

mH

rDXL '1

71 ln102

=

mH

rDXL '2

72 ln102

=

mH

rr

DXLLL'

2'

1

721 ln104

=+=

Inductance due to internal & external flux linkages

Re-arranging the terms

Inductance due to Current in conductor 2

Inductance for the Complete circuit

Geometric Mean Distance (GMD) & Geometric Mean Radius (GMR) [Section 4.8]

( )( ) ( )( )( ) ( )2

''''''

............

...............ln102 7

nnnnbnabnbbbaanabaa

mnnmnbnabmbbbaamabaa

X DDDDDDDDD

DDDDDDDDDXL =

GMDDm = GMRDs =

mH

DDXL

s

mX ln102

7=

Composite Conductor Stranded conductors composed of 2 or more parallel strands

Numerator Geometric Mean Distance or GMD between Conductor X & Y

Denominator Geometric Mean Radius or GMR (self GMD of conductor)

Inductance of 3-phase line with equilateral & unsymmetrical spacing [Section 4.10 & 4.11]

Three-phase line with equilateral spacing Expression similar to single-phase line except for GMR term

Three-phase line with unsymmetrical spacing Flux linkages of each phase not same Different inductance in each phase results in unbalanced circuit Balance restored by exchanging positions of conductors at regular

intervals called as TRANSPOSITION Transposition results in each phase having the same average

inductance over the whole cycle

mH

DDXL

sa ln102

7=

mH

DD

XLs

eqa ln102

7=3

312312 DDDDeq =

Inductance for Bundled Conductors [Section 4.12]

At extra-high voltages (EHV) Corona i.e self discharges around EHV lines Corona causes power losses & communication interference

Alleviated by HV gradient reduction at conductor Achieved by having 2 or more conductors per phase- bundled

conductors

Bundling causes Reduced reactance due to increased GMR of bundle

Reduces effects of Corona

mH

DDXL b

sa ln102

7=

( ) dDdDD ssbs == 4 2For two-strand bundle

Capacitance of 2-wire line [Section 5.1- 5.3]

Electric Flux density

Gausss Law Total electric charge within a closed surface equals total Electric flux emerging from the surface

In other words, total charge within closed surface equals the Integral over the surface of the normal component of electric Flux density

22 mC

xqD f

=

mV

xkqE2

=

VDD

kqdx

kxqEdxv

D

D

D

D 1

212 ln22

2

1

2

1 ===

Electric Field intensity For permittivity k of medium

Capacitance of 2-wire line (contd..) [Section 5.1- 5.3]

mF

vqC =

VDr

kq

rD

kqV bb

a

aab ln2

ln2

+=

ba qq =

VDr

rD

kqV b

a

aab

= lnln

2

Vrr

Dk

qVba

aab

2

ln2

=

mF

rrD

kVqC

ba

ab

aab

==2

ln

2

rrr ba ==

( ) mF

rDkCab ln

= ( ) neutraltom

Fr

Dk

VqCCCab

abnann ln

2

2

====

Capacitance of 3-phase line with equilateral & unsymmetrical spacing [Section 5.4 & 5.5]

Three-phase line with equilateral spacing Assuming that ground is far enough away to have negligible effect

Three-phase line with unsymmetrical spacing Capacitance of each phase to neutral are unequal across lines Balance restored by exchanging positions of conductors at regular

intervals called as TRANSPOSITION Results in same average capacitance to neutral over the transposition

cycle

3312312 DDDDeq =

( ) neutraltomF

rD

kVqC

an

an

ln2

==

mAVCjI annchg /=Charging Current in phase a

neutraltomF

rD

kVqC

eqan

an

==ln

2

Capacitance for Bundled Conductors [Section 5.7]

For two-strand bundle

neutraltomF

DD

kVqC

bsC

eqan

an

==

ln

2

( ) rdrdDbsC == 4 2

fCX c 2

1=

In general, you should be able to evaluate Capacitive reactance using the following formula

rkkk 0=mFxk 120 1085.8

=

1=rk

,

,

for overhead lines

Representation of Transmission Line [Section 6.1]

Line lengths less than about 80 km are classified as short lines Medium lines are between 80 240 kms while greater than 240 kms are long lines Strictly speaking all 4 parameters should be represented as Distributed along the lines Short and medium lines can be modelled using lumped parameters without loss of accuracy Single phase equivalent circuit valid

Normally transmission line are operated with balanced 3-phase load. Though the lines are not space equilaterally and not transposed, dissymmetry is negligible.

.

z = series impedance per unit length per phase y = shunt admittance per unit length per phase to neutral l = length of line Z = zl = total series impedance per phase Y = yl = total shunt admittance per phase to neural

Short Transmission Line Model [Section 6.2]

Equivalent Circuit

RS II =

ZIVV RRS +=100

,

,, xV

VV

FLR

FLRNLR

Phasor Diagrams

Medium-Length Line Model [Section 6.2]

Nominal pie Circuit Voltage-Current Relationship

RRRs VZIYVV +

+=

2

RRs ZIVZYV +

+= 1

2

RRSS IYVYVI ++=22

RRS IZYZYYVI

++

+= 1

241

RRS BIAVV +=

RRS DICVI +=1

2+==

ZYDA ZB =

+=

41 ZYYC

100,

, xV

VAV

FLR

FLRS

Percent regulation =

Long Transmission Line

Parameters are considered to be distributed Voltage/current relationship can be modelled by differential equations Characteristic impedance & propagation constants can be defined

Surge Impedance Loading (SIL) is of practical importance

.

.

Direct-Current Transmission [Section 6.13]

First High Voltage Direct Current (HVDC) transmission began service in 1954 HVDC lines could be monopolar or bipolar Converters needed at line ends for rectification/inversion

Lower cost of DC transmission over long lines

Voltage regulation less problem no effect of series reactance

Underground HVAC transmission limited use because of high charging currents. HVDC only

option for such case e.g. undersea cables

Enables synchronizing between two AC systems with different frequency e.g. Japan

Smaller amount of right-of-way for HVDC line compared with HVAC lines

DC breakers not advanced compared to AC circuit breakers

No simple/robust device like transformer to change the voltage level for DC.

ELECTENG 731Power SystemsSemester 1: 2015Power Systems Issues WorldwideNZ Power Systems IssuesNZ Power Systems StakeholdersSmart GridsSlide Number 6Consumer EngagementUoA Power Systems TrackRelation of other courses to PSPower SystemsSlide Number 11Slide Number 122015 Coverage ELECTENG 7312015 ScheduleLearning ResourcesSlide Number 16Line Modelling - Review (Not in course notes but from reference text book)Slide Number 18Slide Number 19Sub-transmission and Distribution lineSlide Number 21Electric Transmission Line ParametersSlide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39