Ktgrid - Fcl For Bahir Dar University- Rev 1_2.pdf

Fault Current Limiter (FCL) and Power Systems R&D Kasegn Tekletsadik, PhD Chief Technology Officer (CTO) KTGRID [email protected]

+1 978 489 8484

1/3/2019

KTGRID - CONFIDENTIAL

1

Kasegn Tekletsadik, PhD, MIEEE WORK EXPERIENCE ▪ Applied Materials

– Ion Implanter and Fault Current Limiter

▪ Superpower - Superconducting Fault Current Limiter (SCFCL) ▪ General Electric (GE) - X-Ray tubes for Medical equipment ▪ Xerox - Electron Beam Imaging Technology

R&D Interest › New product development › Key Technologies - High Voltage, Electromagnetics, Transients, Power Systems, Power Electronics, Superconductivity, Plasma Technology

▪ Rolls-Royce - Large Power Transformers ▪ University of Strathclyde - Research Fellow − Circuit breakers, Biomedical Plasma Torch

▪ Bahr Dar Polytechnic Inst. - Assistant Lecturer (Dept. Head)

› Multi- disciplinary technologies – Software development, materials, mechanical, thermal and cryogenics technology

▪ Asmara University - Graduate Research/Teaching assistant

Patents

EDUCATION

› Over 30 patents

▪ Ph.D and M.Sc - Electrical Power System Engineering University of Strathclyde, Glasgow, Scotland, UK

▪ B.Sc. - Electrical Engineering Addis Ababa University, Addis Ababa, Ethiopia

Publications › Over 25 publications – presented at IEEE and CIGRE conferences 2

Electricity Generation by Country – Where is Ethiopia?

Ethiopia – Electricity Generation

Ethiopia - Population

▪ 0.033 of world

▪ 1.35% (0.1/7.4B) of world

▪ 0.95% of Africa

▪ 8.22% (0.1/1.216B) of Africa

X41 of World X 9 of Africa

Lots of opportunities for ▪ Power Engineers ▪ Equipment Manufacturers ▪ Electric Utilities 3

Typical Electric Utility Network Generation

Transmission

Distribution

Customers

Grid Traditional or Smart

Substation

Consumers Transmission Line

UTILITY OWNER

Substation Circuit Breakers Transformer

Generation

Protection, Condition monitoring, SCADA, Instrumentation

Power Systems Engineering - Application Generation

Transmission

Distribution

Consumer

Energy Supplier Substation

Substation

Consumers

Generator Transformer

Power Systems ▪ Operation – controlling energy ▪ Planning, Protection ▪ Condition Monitoring (SCADA) ▪ Instrumentation ▪ Communication ▪ Asset Management ▪ Generating, TL, DL and Substation Design

Equipment Selection

Customers

Transmission Line

Distribution Line

Equipment ▪ Generators, Transformers ▪ Circuit Breakers ▪ T&D Lines and Cables ▪ Reactors, Bushings, Insulators, Relays meters, …. ▪ Design and Analysis – ANSYS, ProE, AutoCad, …

Design, Build, Test and Commissioning Equipment

Power Systems Analysis (Simulation) ▪ Load Flow ▪ Short Circuit ▪ Stability, Voltage Regulation ▪ Power quality ▪ Optimization – improve reliability, power quality and Maximize Profit Analysis Software ▪ Steady State (frequency domain) ➢ PSS, DIgSilent, ETAP, CYME, … ASPEN, SKM, PowerWorld ▪ Transient (Time Domain) ➢ EMTP, PSCAD, Simulink, … Free Downloads (demo Versions) ▪ EMTP-RV, ATP-EMTP, PowerWorld

Technology: High Voltage, High Current, Electromagnetics, Circuit Theory, Power Electronics, Protection, Instrumentation, communication, …. 1/3/2019

KTGRID - CONFIDENTIAL

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University as Technology Center of Excellence University Technology Center of Excellence

Industry Uses resources as low cost R&D center

Provides subject matter experts and applied R&D facilities

University

• Provides subject matter experts and applied R&D facilities • Industry appointed professors and graduate students • Facilitates knowledge sharing seminars, training and brain storming meeting • Provides testing and simulation services – broader freedom on what and how to engage with industries • Continuous feedback from industries enriches the centers knowledge base Examples: • Establish “Center of excellence in Power Systems Engineering” – build test facilities, design center and engage with electric utilities and industries in Ethiopia and Africa

Industry

• Identifies technical challenge and asks centers to study the subject in details and provides funding • Expects a professor and gradate student/s to run the R&D activities • Expects experienced graduates to join the company during and after technology transfer

My personal experience • Rolls-Royce – Strathclyde University • Rolls-Royce - Cambridge university • Superpower – RPI, Florida State, Houston University • AMAT – Cambridge, Houston, Chula (Thailand), Taiwan Uni. 6

Center of excellence in Power Systems Engineering Center of Excellence in Power Systems Engineering (CEPSE)

Provides subject matter experts in Power Systems Engineering and applied R&D facilities

Test Labs • High Voltage Test – dielectric tests, AC withstand Voltage, Impulse (BIL), RIV, Partial Discharge (PD), Flashover, condition monitoring and Environmental effects • Short Circuit Test – Short circuit withstand testing on power equipment • Reliability and quality control tests – imported or locally built equipment • Equipment Failure Analysis • Analysis and Design Expertise • Provide power system simulation services to electrical utilities and industrial complexes • Design - generation, T&D networks • Design and study protection systems and SCADA • Opportunities for Testing, Analysis, Design and Consulting

Industry Uses resources as low cost R&D center

Industries • Electric utilities – Generation, Transmission and Distribution • Industrial Complexes – distribution installation • Equipment manufacturers – Transformers, Cables, Circuit Breakers, Capacitors, Bushings, and Insulators

Equipment to be tested – imported or local • • • • • •

Transformers, - HV, SC and Condition Cables, - HV, SC, Loss Capacitors – HV, Loss, Discharge Bushings - HV Insulators – HV Tests include both R&D and Certification 7

Ethiopian National Technology and Testing Lab (Center) - ENTTL ▪ Establish Ethiopian National Technology and Testing Lab (Center) - ENTTL − Learn from American National Labs, Department of Energy (DOE) and Department of Defense (DOD) • How they transform America from natural resources based economy to the leading industrial nation in the world • National labs provide places where the most talented scientists and engineers gather, invent, build prototypes, test their ideas • Sources of technology invention and purposely designed to transfer basic technology to industries

• Sources of technical experts – available to government and private companies • Extensive collaboration with industries, academic institutions and government agencies

− It starts with vision and focus to solve challenges – money comes second − Promote reverse engineering – build prototypes, test and improve product − Establish center of excellences – Power Systems Engineering, Automation, design, simulation, prototyping, testing, new technology and new product development − Establish training centers and consultancy services – bridge technical skill gaps

▪ Initially start with electrical equipment testing and certification Lab − High Voltage, Short Circuit, Equipment failure analysis and diagnostics

− Establish R&D and prototyping center for electrical equipment − Collaborate with Universities, Equipment Manufacturers, government agencies and international testing labs 1/3/2019

KTGRID - CONFIDENTIAL

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National Electrical Equipment Testing Lab Product certification and product type testing ▪ Certification test facilities – Improves quality of imported goods – suppliers take care of their products quality, if they know that their products will be tested on arrival – Improves Ethiopian made products acceptance rate and makes Ethiopian products competitive within Ethiopia – Improves Ethiopian made products acceptance outside Ethiopia – opens Ethiopian export market ▪ Technology transfer and reverse engineering process speeds up with the presence of well established test labs – Collaborate with Universities to build and manage test labs ▪ Test ideas and prototypes – speeds up learning and product turn around time ▪ Improves confidence in building component manufacturing initiative 1/3/2019

KTGRID - CONFIDENTIAL

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KEMA-USA - Test setup for scFCL test KEMA – USA •

•

Test facility with the highest short circuit capacity in USA KEMA – Netherlands Higher capacity than USA

22 kV

44 kV 72 kV

Shunt Reactor

Generator connection

A Fault current

B C 3-Phase Generator

CLR

CB1

3-Phase Transformer

V1

V2

SCFCL

Ish

Isc

▪ KEMA-USA Short Circuit Test Capability

It

– Voltage – single phase up to 72 kV

CB2 – 245 kV SF6 CB

– Short circuit Current – 10 kA at 72 kV up to 63 kA at 10 kV

▪ KEMA-USA High Voltage Test capability – Up to 600 kV AC withstand

▪ Test Data

– Up to 1200 kV Impulse

− Voltages V1 and V2 – Voltage across FCL

▪ Short Circuit tests – Test current limiting performance per design requirements

− Currents – Total limited fault currents (IT), SC Unit Current (Isc) and Shunt Reactor current (Ish)

– Number of short circuits could vary depending on the customer request

− Current limiting performance

– Calibrate system for Prospective Fault Current

How about in Ethiopia? 10

▪ Other test data − On customers request

Fault Current Limiter By

Kasegn Tekletsadik, PhD

1/3/2019

Kasegn Tekletsadik - Confidential

11

Causes of Short Circuit Faults on Power Lines Transformer

CB2

Short Circuit Fault

CB1 Load

Substation ZS = RS + j XS

Generator

Fault current

•

Short circuit faults produce > 10 Times rated current

•

Generates huge amount of Electromagnetic force and induces Mechanical and thermal stresses on equipment

• Q and 𝐹 ∝ ‫ 𝐼 ׬‬2 𝑑𝑡 • Protection system cost and complexity increases as fault current increases 1/3/2019

Kasegn Tekletsadik - Confidential

12

Fault Currents are Destructive ▪ Large fault currents can cause the grid to fail catastrophically

Aug 14, 2003 Blackout

▪ Aug 14, 2003 Blackout in USA and Canada Affected over 50M people

▪ Fault currents can damage capital infrastructure of the grid – Transformers – Transmission lines – Bus bars

– Joints – Circuit breakers Mechanical Stress from Electromagnetic Force σ = 𝑘 𝐼 2 𝑑𝑡

‫׬‬

Thermal Stress

Q= 𝑐 ‫ 𝐼 ׬‬2 𝑑𝑡 Both Equipment manufacturers and Electric utilities need to mitigate the negative impacts of Short circuit faults 1/3/2019

Kasegn Tekletsadik - Confidential

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Drivers of the Fault Current Problem Generation

Transmission

Distribution

Customers

Grid Interconnection

Increased Fault Current Level

Increased demand

New Generation ▪Renewable energy – wind, solar, hydro ▪Micro-Nuclear power ▪Increased grid interconnection

▪ Transportation - Electric cars, Trains ▪ Urbanization ▪ New industries ▪ Population growth

Both new generation and increased demand for energy increase fault current levels 1/3/2019

Kasegn Tekletsadik - Confidential

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How Do Utilities Typically Protect Against FC’s Now? ▪ Over-engineer the system ▪ High impedance transformers ▪ Current Limiting Reactors ▪ Breaker & Busbar Upgrades

▪ Bus Splitting ▪ New Substations

❖ Current Solutions are Expensive, Inefficient and create potential Control and protection problems ❖ No Ideal Solution exist to the Fault Current Problem ❖ No or very little competition for a new technology based FCL product – An excellent opportunity for new business 1/3/2019

Kasegn Tekletsadik - Confidential

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Desired Characteristics of Fault Current Limiter An ideal Fault Current Limiter would – In normal operation, it is virtually "transparent“ (no power loss or voltage drop) to the network – During fault - Increases the impedance on the line and reduces fault current to a desired value – After fault is cleared - returns to low impedance status fast

Normal operation: ZFCL = ~ 0

FCL

During Fault: After Fault Clears:

ZFCL = ~ 0 Recovery time

Typical current waveforms due to fault Normal Operation

Fault

Recovery

Fault Clearing

Fault Inception

Without FCL (Prospective Fault Current)

– Superconductor – inherent property – Solid State Switch – Passive Fault Current Limiter (pFCL)

td (Fault duration time)

Normal Load Current

1/3/2019

ZFCL = j XFCL + RFCL

Current Limiting Impedance

Current

› An ideal FCL would require a fast switch capable of handling high power

FCL Impedance variation

FCL

Kasegn Tekletsadik - Confidential

Prospective Fault Current

tr (recovery time)

Limited Fault Current

16

1/3/2019

Kasegn Tekletsadik - Confidential

17

Benefits of Fault Current Limiters ▪ Enhances interconnection of the grid − Increased substation capacity

− Easier addition of new generation

▪ Increased asset utilization − Deferral of capital equipment upgrade − Equipment life extension

▪ Minimizes (Eliminates) Equipment Failure − Reduction in fault current – reduces electromagnetic force generated mechanical stresses − Reduces thermal stresses

▪ Improves system performance − Safety - Arc Flash Reduction and Brush Fire Suppression − Transient stability – by introducing low X/R reactor − Voltage stability – isolating faulty section with FCL − Operational flexibility

1/3/2019

Kasegn Tekletsadik - Confidential

Impacts on Utility performance, customer perception, and cost of Business • Less complex system design with lower fault current rating equipment • More reliable and resilient grid • Less frequent and shorter duration power outage • Safe operation • Less expensive equipment – cost reduction 18

Principles of Fault Current Limiter operation Shunt Reactor ZSH = RSH + j XSH

Transformer CB2

ISH IT

CB1

CB3 IFCL

Substation ZS = RS + j XS

Generator

Short Circuit Fault

ZFCL

Load

FCL Unit = RFCL + j XFCL Fault current

▪ Normal operation – Load current flows through the FCL unit - ZFCL << ZSH and IFCL > 90%IT – FCL introduces nearly zero impedance, zero voltage drop and zero active and reactive power loss ▪ Fault Condition – FCL unit senses fault current, and inserts high impedance, with in ~ 2 ms – Current transfers to shunt reactor and limits fault current - ZFCL >> ZSH and ISH > 90%IT ▪ Recovery – FCL unit recovers to its low impedance state quickly – Instant (SSFCL) and within 3.5 seconds for SCFCL 1/3/2019

Kasegn Tekletsadik - Confidential

19

Application of Superconductors as Fault Current Limiters Current

T

Temperature

Resistivity, ρ [Ω.m]

Voltage

Current

T ≥ Tc Normal state, Resistance > 0

T < Tc Superconducting state, Resistance = 0

Tc Temperature [K]

B

Magnetic Field

Resistivity, ρ [Ω.m]

Voltage B < Bc Superconducting state, Resistance = 0

B ≥ Bc Normal state, Resistance > 0

Bc Magnetic Field, B [T]

Current

J

Current Density

Resistivity, ρ [Ω.m]

Voltage

J < Jc Superconducting state, Resistance = 0

J ≥ Jc Normal state, Jc Resistance > 0 Current Density, J [A/cm2]

Superconducting Materials are Ideal for Fault Current Limiters Fast Switching Enables First Peak Reduction 1/3/2019

Kasegn Tekletsadik - Confidential

➢ Fast transition from Superconducting to Normal (resistive) state ➢ Zero resistance during normal operation, J < Jc, B < Bc and T < Tc ➢ Limiting impedance during fault condition, J ≥ Jc, or B > Bc or T > Tc ➢ Ideal characteristics for fast switch application ➢ Uses inherent material properties

➢Ideal for Fault current limiter ➢Passive – does not need active control system

Superconducting Magnets for Maglev Trains - Is it in Arrivo’s future?? 20

Current Limiting Performance SCFCL - Current Limiting Performance

1.0 0.8

2.4

0.5

2

Current

1.6

0.0

1.2

-0.3

0.8

-0.5

0.4

Voltage

-0.8

Voltage [pu]

0.3

Current [pu]

2.8

0

-1.0

-0.4

-1.3

-0.8 0

10

20

30

40

50

60 70 80 Time [ms]

Prospective Fault Current [kA] Superconductor Current [kA]

90

100

110

120

130

140

Limited Current [kA] Shunt Current [kA]

▪ Fault current limitation including the 1st peak is achieved when SC unit inserts high resistance in the circuit and most fault current transfers from SC unit to the Shunt Reactor ▪ Due to a smooth impedance change there is no transient overvoltage across the FCL 21

ssFCL – Principles of Operation Transformer

Shunt Reactor CB2

Short Circuit Fault

CB3

Zsh = Rsh + j Xsh

IGBT Module

CB1 Substation

1

2

m

Load

ZS = RS + j XS Fault current

Generator

▪ Normal operation – Load current flows through Solid State unit

25

– SSFCL introduces nearly zero impedance, zero voltage drop and negligible active and reactive power loss

20 15

▪ Fault Condition

– Fast response time - < 2 ms – Current transfers to shunt and limits fault current – Fast Acting Fuse protects the system incase of SS Unit failure to open

▪ Recovery – SSFCL can be designed to recover instantly or within few cycles after the fault is cleared

10 Current [kA]

– Solid State trigger circuit senses fault current, opens SS circuit, inserts high impedance

SSFCL Current Limiting Performance - 10 kA rms fault limited to 5 kA rms fault (50% Current Reduction)

5 0 -5 -10 -15 0

20

40

60

80 100 120 Time [ms] Prospective Fault Current [kA] Limited Current [kA] Superconductor Current [kA]

Shunt Current [kA]

22

140

160

Fast Switch Fault Current Limiter (FSFCL) Transforme CB2 r

IVCR

Fast Switch FCL - Current Limiting performance 1 0.8

CB3

0.6

Substation

ZS = RS + j XS

Generator

IFS

Loa d

Current [pu]

CB1

IT

Short Circuit Fault

Voltage Control Reactor (VCR)

0.4 0.2

Fast Switch (FS)

0

-0.2

Fast switch Fault Current Limiter (FSFCL) Circuit

-0.4 0

Current, I

F

›

Uses EM Force to Open

›

Uses

Closed

Open

mechanism to close ›

I

As a recovery breaker closes – after ~ 3 – 5

Coil

seconds Air cylinder Open – during fault Restricted – during recovery 1/3/2019

›

As a backup breaker – closes instantly

30

40

50 60 70 80 Time [ms] Prospective Fault Current [pu] Limited Fault Current [pu]

100

90

100

0.6 0.4 0.2 0 0

10

20

30

40

50 Time [ms]

Prospective ∫i2dt [kA-s]

KTGRID - CONFIDENTIAL

90

0.8 ∫i2dt [pu-sec]

EM, F = k I

20

Fast Switch FCL - The effect of current limitation on ∫i2dt energy factor

1

mechanical/pneumatic 2

10

60

70

Limited ∫i2dt [kA-s]

23

80

Substation

Generator

Transformer

pFCL Unit

Fault

pFCL Impedance

Principles of Passive Fault Current Limiter operation Load

ZFCL = RFCL + j XFCL

ZS = RS + j XS

Z_ins

Normal operation

▪

▪

pFCL inserts high impedance instantly when fault current exceeds let through fault current – passive fault current sensing, it does not use current or voltage or any other internal or external sensors to trigger pFCL – ZFCL = RFCL + jXFCL

During Recovery ▪

Fault

Recovery

1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 20

pFCL recovers instantly – no need for special recovery under load protection - ZFCL ≈ 0 1/3/2019

Recovery time instant

Fault Current Limiting performance

pFCL introduces nearly zero impedance, zero voltage drop – ZFCL ≈ 0

During Fault Condition

Normal

Z_Fault

Time

Load current flows through the pFCL unit - all components designed to handle continuous and short term over load requirements

Current [pu]

▪

Response time 2-4 ms

40

60

80

Prospective Fault Current KTGRID - CONFIDENTIAL

100 120 Time [ms]

140

160

Limited Fault Current 24

180

200

Potential FCL Applications Generator Generator

Generator FCL

Transformer

Transmission Network 400 kV, 500 kV, 765 kV, >765 kV

FCL

FCL

FCL

Transmission 220, 230, 287, 345 kV

Generator

FCL

FCL

FCL

Generator

FCL

FCL

Network coupling

FCL FCL

Sub - Transmission 115, 138, 145, 161 kV

Generator

FCL FCL

Busbar coupling

Distribution Network 10, 12, 15, 22, 35, 45, 66, 69 kV

FCL

FCL

FCL

FCL

1/3/2019

Kasegn Tekletsadik - Confidential

25

Fault Current Limiter (FCL) - Transmission System CB

Circuit Breaker

Transmission line

SCFCL

SCFCL

Short circuit Fault

Impedance on Demand

Transmission line

Fault Current Limitation ▪ Enables Independent Power producers (IPP) to connect to main grid – eliminates fault current constraint ▪ Protects expensive equipment from damages caused by excessive short circuit currents – extends life

▪ Enables utilities to defer or avoid equipment upgrades ▪ Enables existing assets optimal utilization 1/3/2019

• • • • •

Kasegn Tekletsadik - Confidential

115 kV SCFCL – Glow Energy in Thailand Improved Interconnection Improves Power Quality Reduce Voltage Sag and losses Increases Power Capacity Life Extension of expensive equipment 26

Fault Current Limiter Platforms pFCL Unit

Shunt Reactor, ZSH

= RSH + j XSH

ISH

Shunt Reactor, ZSH

ISH SC unit

ISC

pFCL

ZFCL = RFCL + j XFCL

scFCL

Superconductor Unit ZSC = RSC + j XSC

Transmission System FCL

Distribution System FCL

▪ 66 kV to 500 kV transmission voltage levels

▪ Up to 66 kV distribution voltage levels

▪ Passive Fault Current Limiter (pFCL)

▪ Solid State Fault Current Limiter (ssFCL)

▪ Superconducting Fault Current Limiter (scFCL)

▪ Fast Switch Fault Current Limiter (fsFCL)

▪ Passive Fault Current Limiter (pFCL)

▪ Fast Switch Fault Current Limiter (fsFCL)

▪ Superconducting Fault Current Limiter – If required

▪ Flexible load current specs.

▪ Flexible load current specs.

−

Up to 50 % or higher fault current reduction 1/3/2019

= RSH + j XSH

SS unit

ISS

Solid State Unit ZSS = RSS + j XSS

ssFCL

Shunt ISH

IT

IFCL

fsFCL

FCL

▪ Up to 50 % or higher fault current reduction Kasegn Tekletsadik - Confidential

27

Fast Switch (FS)

Typical FCL Applications In-Line FCL Application Section 1

Bus-Tie FCL Application

Section 2

Section 2

Section 1

Zs1

I2

I1

Zs2

I1

FCL

Bus1

Bus1

Bus2

V2

V1

Fault ILIm

Zs2

I2

Zs1

Bus2

V2

V1

Fault ILIm

FCL Bus Tie FCL

Bus Tie Breaker

Fault Current Limitation ▪ FCL Fault Current Reduction, 𝑐𝑟

Fault Current Limitation ▪ FCL Fault Current Reduction, 𝑐𝑟

=

𝐼𝑃 −𝐼𝐿𝑖𝑚 , 𝐼𝑃

▪ where IP = prospective fault current and ILim = limited fault current ▪ Limited Fault Current , ILim = (1 - cr).I1 + I2

=

𝐼𝑃 −𝐼𝐿𝑖𝑚 , 𝐼𝑃

▪ where IP = prospective fault current and ILim = limited fault current ▪ Limited Fault Current , ILim = (1 - cr).I1 + I2 Voltage Sag Improvement ▪ V1 = cr.Vs, for example a system with an FCL of cr = 0.8, the voltage at the un-faulted Bus1 can be kept to 80% of the system voltage (Vs) 28

Cost-effective Location for FCL Applications Bus-Tie FCL Application Section 1

Section 2

Fault at section 1 (F1), 𝐼𝐹𝐶𝐿 = 𝐼1 + 𝐼𝐹21 𝐼𝐹𝐶𝐿 = 𝐼1 +

I1 Bus1

Zs1

𝐼𝐹2 ∗ 𝑍𝑠2 𝑍𝑠2 + 𝑍𝐹𝐶𝐿

Zs2

F1 IF1

I2 V2

V1

F2 IF2 Bus2

IF12

IF21

Fault at section 2 (F2), 𝐼𝐹𝐶𝐿 = 𝐼1 + 𝐼𝐹12

FCL Bus Tie FCL

ZFCL

𝐼𝐹𝐶𝐿 = 𝐼2 +

𝐼𝐹1 ∗ 𝑍𝑠1 𝑍𝑠1 + 𝑍𝐹𝐶𝐿

Cost-effective Location for FCL Application ▪ In a complex system a Bus-Tie application offers most cost-effective FCL application

▪ Best location for FCL is where fault contributions from both sides of the FCL are close to each other, IF1 ≈ IF2 ▪ In case some of the generations are disconnected, the FCL can be by-passed to allow higher current through the bus-tie ▪ Voltage sag improvement is an additional benefit with this arrangement 29

System Requirements, FCL Rating and Cost Drivers ▪ Major cost drivers

System Parameters - Provided by Utility System Voltage - Line-to-Line, Vs Maximum Load Current, IL Prospective Fault Current, Ip Limited Fault Current, Ilim Calculated System Parameters System Short Circuit Impedance, Current Reduction,

𝐶𝑅 =

Shunt Reactor Impedance,

𝑍𝑠 =

𝑉𝑠 𝐼𝑝. 3

𝐼𝑝−𝐼𝐿𝑖𝑚 𝐼𝑝

𝑍𝑠ℎ = 𝑍𝑠

𝐶𝑅 1−𝐶𝑅

Voltage Drop Across FCL, 𝑉𝐹𝐶𝐿 = 𝑍𝑠ℎ. 𝐼𝐿𝑖𝑚 Recovery time after Fault is cleared Fault Current Limiter Rating System Voltage = 220 kV Load Current = 1500 A Voltage Drop during fault = 65 kV Shunt Reactor impedance = 5.08 Ω Prospective Fault Current = 25 kA rms Limited Fault Current = 12.5 kA rms Current Reduction = 50% Recovery time = Instant for pFCL and 3.5 sec for SCFCL

220 1500 25 12.5

KV rms A rms kA rms kA rms

5.08

Ω

50

%

5.08

Ω

63.5 2.0 - 3.5

kV rms sec

– Load current (IL) – Fault current reduction (CR) – Voltage drop across the FCL during fault (VFCL)

▪ Cost factor (CF) related to FCL rating

CF = k1. IL.CR = k2.IL.VFCL = k2.IL.ILim.ZFCL ▪ Size and weight of the FCL is also linearly proportional to the cost factor ▪ Use these factors - to optimize the FCL application and location for a cost-effective solution 30

Case Study - Ethiopian Electric Power Authority

Short Circuit Challenges Equipment Failures, Causes and Solutions Kasegn Tekletsadik, PhD Chief Technology Officer (CTO) KTGRID [email protected]

+1 978 489 8484

1/3/2019

KTGRID - CONFIDENTIAL

31

Short Circuit Challenges and Equipment Failures Substation

▪ Ethiopian Electric Power (EEP) Information

Fault

Load

− Short circuit faults cause significant amount of power outages and equipment failures Generator (Grid)

▪ System parameters

Transformer 63MVA, 132/33kV

− System Voltage – 33 kV distribution system − Transformer rating – 63 MVA, 132kV/33 kV, 276A/1100 A − Network connection – radial

▪ Impact on operation and equipment life − Frequent Transformer failure − Circuit breaker, cables/wires and connector failures − Frequent and extended power outage − Loss of revenue, transformer replacement cost

▪ Short Circuit Fault Information

− Angry customers – poor customer perception

− Occurrence (frequency) – In some areas up to 480 faults per month were recorded – this number is too frequent and needs validation from EEP − Short circuit current – up to 12 kA at 33 kV line − Short Circuit Impedance at 12 kA fault = 1.6 Ω

1/3/2019

▪ Existing Equipment Failure Solutions –

Replace failed equipment

–

Attempt to reduce short circuit faults – cutting trees and clearing lines from other structures

–

Improve equipment selection process – quality and reliability control

Kasegn Tekletsadik - Confidential

32

Short Circuit Challenges and Equipment Failures Equipment design guidelines •

Transformers are expected to work for around 40 years – at normal operating conditions

•

Some operating conditions such as overloads, overvoltages and too frequent short circuits shorten life expectancy

•

The common understanding in transformer manufacturers is there will be a maximum of around 10 short circuit faults per year – 400 faults per transformers life time

•

In Ethiopian case, 480 faults per month means the transformer has already served its 40 years life in less than a month

•

In addition to the number of faults, the magnitude of the fault current is another life determining – reducing fault current increases life expectancy

•

Reputable and known transformer companies would not sell transformers with such excessive number of faults – they may recommend specially designed short circuit transformers that are very expensive and larger sizes

1/3/2019

Transformer Life expectancy – related to short circuit fault occurrence frequency, magnitude and duration •

Life expectancy (L) is strongly affected by; – Short circuit occurrence or the number of faults (N) – Magnitude fault current (I) – 1st peak and rms depending which one is used – Duration fault (Δt) – usually defined as number of cycles or actually time in seconds

𝐿=

𝐿0 𝑥 𝑦 1+σ𝑁 1 (𝑘𝑖 .𝐼 . ∆𝑡 )

Where L = Remaining life in years Lo = maximum life expectancy with natural aging of materials like insulation paper, example Lo = 30 and 40 years is common Ki = empirical constant for ith fault x and y = are exponents that determines how the short circuit fault current magnitude and duration affect life expectancy Since most of the failure causing stresses, mechanical and thermal, are proportional to I2 in most cases x could be ≥ 2. As an example: a 50% reduction in fault current could extend transformer life by 4 times.

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Short Circuit Challenges and Equipment Failures • Existing Equipment Failure Solutions

Substation

pFCL Unit

Fault

Load

– Replace failed equipment – Improve equipment selection process – quality and reliability control: Challenge – No testing laboratory – Pre-screening testing – routine testing of all transformers and use only those passed the quality and reliability standards: Challenge – No testing laboratory

Transformer

ZFCL = RFCL + j XFCL

– Cost Benefit Analysis – At a 50% fault current reduction – 1 pFCL could worth more than 3 transformers, if we consider direct replacement equipment cost – Loss of revenue, power outage impact on customers business and life standard - Waiting time to order and receive equipment

– Improve protection, control and condition monitoring systems – use performance and operational prediction and early warning tools

– Labor and transport cost to replace failed transformers

• New and Cost Effective Solution – Use Fault Current Limiters to reduce the fault current level and extend transformer and other equipment life – a 50% reduction in fault level could extend transformer life by more than 4 times (400%). 1/3/2019

Generator (Grid)

– Cost of Cascaded failures - Transformer failure could also cause failures of other equipment, such as bus-bars, connectors, circuit breakers, current and voltage transformers, protection systems – If all related costs, both tangible and intangible, are added the value of a single Fault Current Limiter could easily exceed the value of more than 6 transformers – Using Fault Current Limiter makes sense and is cost-effective

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Bahir Dar University and Fault Current Limiter (FCL) Technology Kasegn Tekletsadik, PhD Chief Technology Officer (CTO) KTGRID [email protected]

+1 978 489 8484

1/3/2019

KTGRID - CONFIDENTIAL

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Bahir Dar University – How to benefit from Fault Current Limiter (FCL) technology Post Graduate Projects

Possible Projects

▪ Start with few MSc and PhD programs related to the Technology, design, testing, application and implementation of fault current limiters

• Short Circuit Analysis – using EEP/EEU network

▪ Collaborate with the electric utilities and industrial companies to analyze the impacts of fault currents on equipment failure and impacts ▪ Develop related design skills, prototyping and testing laboratories ▪ Use reverse engineering methods ▪ Develop power systems analysis expertise 1/3/2019

• Impact analysis/study of short circuit faults on – Operation – Equipment failure – Power outage and – System upgrades • Fault current limiter technology development

• Fault Current Limiter design, prototyping, testing and product development – Solid State FCL – Fast switch FCL – Passive FCL • Protection coordination with FCL in the system • Integrate FCL with reactive Power compensation – Long distance transmission lines KTGRID - CONFIDENTIAL

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Discussion ▪ How can I help?

1/3/2019

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