Nihar S Raj, Business Head – Power Consulting (Asia) , …file/Short+circuit.pdf · ·...

© ABB| Slide 1September 21, 2016

Short Circuit in Power SystemTechnical Colloquium Indonesia PLN - ABB

Nihar S Raj, Business Head – Power Consulting (Asia) , Presentation, Intercontinental, 22nd Sep 2016

© ABB| Slide 2

Important notices

September 21, 2016

1. Please be aware of Safety requirements & Emergency Exit2. Kindly keep your mobile phones in “SILENT MODE”.3. More discussions / interactions on the topic.

Power ConsultingGlobal network of industry recognized subject matter experts…

Sri P.Trans. Planning& Operations

John D.Subsynch.Phenomenon

Dave D.HVDC/FACTS

Rodolfo K.System Stability& Dynamics

Albert K.System Studies

Sal G.Digital Grid /Distr. Planning

Lan T.Gen./Renewables Planning

Jin Z.PowerEconomics

Carlos H.SubstationAutomation

Ricardo G.Power SystemAnalysis

Bandaru KFailure AnalysisPower Products

Manoj KArc FlashMitigation

Julia S.Industrial PowerSystems

Arefeh S.InsulationCoordination

Andreas U.Distribution Sys.Modeling

Fahd H.WAMS

Ramana B.AC/DCInteraction

Alireza M.HarmonicsAnalysis

Ines RomeroRenewables /Supergrids

Joaquin M.Microgrids

Paula F.ProtectionCoordination

Nihar R.RenewablesIntegration

© ABBAugust 3, 2016

Ron WilloughbyT&D PlanningOptimization

Khoi V.Energy Storage

A team of 125 technical experts with deep know-how, located worldwide to support you on extensive mattersrelated to electrical power systems


Short CircuitAgenda

1. What is Short Circuit2. Some Basics3. Why does this occur in Power System4. Effects of Short Circuit5. Some solutions…6. Case Studies

© ABB| Slide 5

• Accidental or intentional conductive path between two or more conductive parts forcingthe electric potential differences between these conductive parts to be equal or close tozero.

– IEC 60909-0 (ed1.0) 2001• Different Definitions….

• An unwanted low-resistance connection between two points in an electric circuit.

• An abnormal electric path

• The condition that occurs when a circuit path is created between the positive and negativepoles of a battery, power supply, or circuit.

• A situation that occurs when hot and neutral wires come in contact with each other.

• An accidentally established connection between two points in an electric circuit, such as when atree limb, or an animal bridges the gap between two conductors.

September 21, 2016

Short CircuitWhat is it ??.

One of the most critical aspect in Power System affecting economics & availabilityOne of the most critical aspect in Power System affecting economics & availability


Short CircuitBasic – Simlpe Electric Circuit

E

R

L C

EiR jX

=+

urr

-150

-100

-50

0

50

100

150

0 0.05 0.1 0.15 0.2

EI

§ Normal Power flow in the network

§ The current flow in the network depends onthe network elements R, L and C

1Ei

R j LC

ww

=æ ö+ -ç ÷è ø

urr

EiR jX

=+

urr

2 2Emagnitude

R Xi æ ö

ç ÷= ç ÷+è ø( )1tanangle Xi R

-=


Short CircuitBasic – Simlpe Electric Circuit

§ A constant AC power source

§ A switch

§ Impedance Zsc

- Zsc represents all impedancesupstream to the switch

§ Load impedance ZL

§ Upstream of switch includes variousnetworks with different voltage levels ,transmission lines, cables, generators,transformers etc

E

R

L

switch

E

Zsc

switchZL


Short CircuitBasic – Mathematical Solution

Applying kirchoff’s voltage law (KVL)

There are two solution part of thisequation

§ Natural response

§ Particular solution

E

R

L

switch

max sin( ) . diE wt R i Ldt

f+ = +

(0,2 )radf pÎ

( ) ( ) ( )n pi t i t i t= +

( ) 1max1 2 2 2

( ) . .sin tanR tL

pE Li t C e wt

RR Lw

fw

- -æ öæ ö= + + - ç ÷ç ÷è øè ø+


Short CircuitBasic – Expression for Short Circuit Current

( ) 1max2 2 2

1max2 2 2

( ) . .sin tan

.sin tan

R tL E Li t e

RR LE Lwt

RR L

wfw

wfw

- -

-

é ùæ öæ ö= - - +ê úç ÷ç ÷è ø+ è øë ûæ öæ ö+ - ç ÷ç ÷è ø+ è ø

Alternating and sinusoidal component

Aperiodic component

DC component

§ Initial value depend upon f i.e. the point on wave when switching is done

§ Decay rate is depend upon the ratio of R/X ( R/(wL) )

Sinusoidal component

§ Magnitude independent of ratio R/X


Short CircuitBasic –Short Circuit Current Wave Form

1. Sub transient period : 10 – 20 ms

2. Transient period : 20ms – 100 ms

3. Steady State : 100 – 300 ms


Short CircuitBasic – Symmetrical Short Circuit Current Wave Form

Machine is Unloaded

Xl = Leakage Reactance

Xa = Armature Reactance

Xf = Field Reactance

XD = Damper winding Reactance

© ABB| Slide 12

Peak current is deduced from the RMS value of the symmetrical short circuit current usingequation

Where, k depends on the R/X or X/R ratio

Peak current are calculated to determineMaking capacity of the Circuit breakerElectro-dynamic force that installation must withstand

September 21, 2016

Short CircuitBasic – Peak Current

Machine is Unloaded


Short CircuitBasic – Magnitude of short circuit current

© ABB| Slide 14

Power & AutomationPower & Automation

September 21, 2016

Short CircuitBasic – Effect of X/R ratio on Fault current

High X/R ratio increases the decay, Iinst & the peak currentHigh X/R ratio increases the decay, Iinst & the peak current


Short CircuitBasic – Instant of Fault

What happens at 90 deg ??What happens at 90 deg ??


Short CircuitBasic – Instant of Fault

1. With the increase in the value of q, the DC component comes down for a fixed value of X/R

2. It is max at 0 deg and min at 90 deg again the value will increase but in the opposite direction

3. The switching instant is equally important.

4. Incase of normal switching this aspect is controlled by controlled switching.


Short CircuitBasic – Type of Faults in Power System

SymmetricalLine to line to line (L-L-L) fault,Also known as three phase fault

AsymmetricalLine to ground (L-G) faultLine to line (L-L) faultLine to line to ground (L-L-G) fault

75 – 80% is LG Fault

7 – 8% is LL Fault

10-12% is LLG Fault

8 – 10% is LLLG Fault


Short CircuitBasic – Boundary Condition

• The nature of each type of short circuit creates certain mathematical boundaryconditions

• These conditions are useful to model a faulted system with sequence impedancenetwork

Type of fault Boundary conditions

Single phase Ib = Ic = 0 and V a = 0

2 Phase to ground Ia = 0 and V b = V c = 0

2 Phase Ib = - Ic and V b = V c

3 Phase Ia + Ib + Ic = 0 and V a = V b = V c

3 P h ase


Short CircuitBasic – Standards

• The available software packages for fault analysis are• NEPLAN• ETAP• PSS/E• and many more….

141-1993 IEEE Red Book

399-1997 IEEE Brown Book

242-2001 IEEE Protection and Coordination of Industrial and Commercial Power System


Short CircuitDifferent Cause....

Lightning strike on the transmission lines

Travelling wave phenomenon

High tower footing resistance can also lead tohigh stress on the insulators

Can lead to Insulator flashover

Lightning Phenomenon Switching Phenomenon

Switching phenomenon is critical at EHV andUHV levels

Switching of CB’s can produce high stress oninsulation within system leading to dielectricfailures

This may cause faults within system.


Short CircuitDifferent Cause...

Contamination of insulators, deposition of salts

Stringent environmental issues near industry &

Sea coast / saline areas

There is also an increase PD activity

Insulator contamination Equipment failure

Undesired voltage and currents within thesystem can stress insulation and accelerate theequipment aging.

Inadequate rating, increase in fault levels,incorrect erection, problems in protection arefew of the trigger for equipment failure.



With increase in load & generation, grid becomesmore complex.

With growth in the AC systems there is increasein the fault levels within the Power System

This increases the short circuit levels withinsystem.

Growing Power System Nature

Increased snow condition can increase the lineloading leading to Transmission line failure

High storm condition can also lead totransmission line failure leading to short circuitwithin Power System.

Load-1

Load-2

Load-3Vac



Trees near the transmission line are one of thebig contributors to faults.

Increased load can also increase sag, therebyreduce clearance

Vegetation Improper Maintenance

Improper maintenance and higher loading ofequipments can reduce the equipment life

Earthing, erection, testing & maintenance arecritical aspects

Any small negligence can lead to failure thusfaults


Short CircuitEffect of Short Circuit Current

High Electrodynamic Forces – Can lead to massive “DAMAGE”High Electrodynamic Forces – Can lead to massive “DAMAGE”


Short CircuitEffects of Short Circuit Current.

NEPLAN®

Very High Arc Energy – Safety Issues Switchgear Adequacy

© ABB| Slide 26

High thermal energy leadsto insulation damage.

It can also lead to fusing ormelting of conductors

Fire and Damage toequipments and persons

September 21, 2016

Short CircuitEffects of Short Circuit Current

Damage to Insulation Welding conductor Fire and Danger to life

High Fault currents needs to be AVOIDED & In-depth System Study is REQUIREDHigh Fault currents needs to be AVOIDED & In-depth System Study is REQUIRED

© ABB| Slide 27

1. Voltage dip till the fault is cleared – till few milli seconds (Depends on Protection setting)

2. Shutdown of the part of network – Area depends on the protection philosophy design and operationof protective relays

3. Dynamic instability and loss of synchronism

4. Disturbance in control / monitoring system

5. The high induced current may also cause disturbance in the nearby circuits.

September 21, 2016

Short CircuitEffect of Short Circuit Current

Short Circuit Currents can have multiple effects.Short Circuit Currents can have multiple effects.


Short CircuitEffect of Short Circuit Current - EDF

Ref : Parametric Analysis of Electrodynamic forces in Power System based on IEC 60865 by Nihar Raj

© ABB| Slide 29

1. Maximum Short Circuit Current

1. Breaking capacity of circuit breaker

2. Making capacity of circuit breaker

3. Electrodynamic withstand capacity of the switchgear and different elements of Power System

4. Thermal capacity of Switchgear

5. Insulation degradation

2. Minimum Short Circuit Current (Sensitivity of Protection System)

3. Sizing of equipments (CT, Transformer, Isolator, Busbars etc..)

4. Network Stability

5. Voltage stability and Reactive Power compensation

6. Decides the strength of network to absorb Renewable Power.

September 21, 2016

Short CircuitSignificance of Short Circuit Current

Both values : “Maximum” & “Minimum” is ImportantBoth values : “Maximum” & “Minimum” is Important


Short CircuitSignificance of Short Circuit Current – Deicing & Arc Furnace

Both values : “Maximum” & “Minimum” is ImportantBoth values : “Maximum” & “Minimum” is Important

Short circuit current can create heat due to Joule’s effect

This can help in de-icing

Requirement is also to know the right amount of current to be passed without damagingthe conductor.

Arc furnace – Aluminum Smelter : High heat is produced by the electric arc


Short CircuitSignificance of Short Circuit Current - Earthing

Very Critical for Earthing Design impacting SAFETY of Human & EquipmentVery Critical for Earthing Design impacting SAFETY of Human & Equipment

Equipotential Surface Self Impedance Considered Self & Mutual ImpedanceConsidered

1. Fundamental input for Earthing Designs

2. With increase in the value of currents safety is a concern

3. Earthing design to be done as per FEM solutions

4. Site measurements are very important to ensure safety of design

© ABB| Slide 32

• There are several methods that can be used to reduce fault level in the network.• Current limiting reactors• Is-limiter• Superconducting fault current limiter• Solid-state fault current limiter• Network splitting

September 21, 2016

Short CircuitFault Current Reduction - Methods


Short CircuitFault Current Reduction – Is Limiters

t

i

T2T0 T1 T3

T1 : Operating time of the protection relay: 30 - 40 ms

T2 : Operating time of the circuit-breaker: 40 - 80 ms

T3 : Arc duration: 10 - 20 ms

T0 : Response time of the protection relay: 10 - 20 ms

90 - 160 ms

Total time ofcurrent flow throughIs-limiter: T = 5 - 10 ms

T



125 kA50kA x χ x 2

i1

50 kA

50 kA

Current curve at the short-circuit location

u

t

i

50 kA

i = i1 + i2without IS-limiter

250 kA

i2

i = i1 + i2with Is-limiter50 kA


Short CircuitCase Study 01 : High Reliability High Short Circuit

Reference : Technical Paper distributed.

22kA35kA

33kV Switchgear Short Circuit Withstand capability is 25kA/1sec




• To mitigate the adverse effects of increased short circuit levels, analysis done toprovide optimal current limiting device.

• Comparative analysis between current limiting reactor & Is limiter were made.

• As technically Is limiter provides more benefits to the refinery system, 5 Nos. of Islimiters were proposed to installed in 33kV Ties

Current Limiting reactor Is LimiterAdds voltage drops No voltage dropReactive power loss No reactive power lossSpace required is more Less Space required




System studiesHigh ReliabilityOptimize on Generator costTransient stability of the system

power study to improve power factor

Detail system study and close coordination withcustomer.Introduction of Fault current limiter and Reactivepower study to improve power factor

Improved Active Power within systemLimitation of short circuit currents with Is limitersImproved system stability.

Customer Need

ABB Response

Customer Benefit


Short CircuitCase Study 02 : High EDF for 400kV Substation

Reference : ABB Executed Project

High Electrodynamic ForcesSubstation in polluted areaHigh short circuit levelRequirement of design as per standards

Detail design and calculationsSolution to overcome the effect of highElectrodynamic forces

design.

Safe Engineered solution running for more than12 years.High reliability. Safe Gantry and Structuredesign.

Customer Need

ABB Response

Customer Benefit


Short CircuitCase Study 03 : Safe Solution for High Short Circuit Current

Reference : ABB Executed Project

Safe Earthing SolutionIdentify unsafe areas within InstallationCheck the health of existing earthing systemUpgrade the earth installation from 40kA to 63KA

Detail site measurements as per latest standardsSimulation on FEM software to identify areas to bestrengthened.

Plant

Safe solution to the customer for increased faultlevel of 63KAEarthing Health assessment for the entire PowerPlant

Customer Need

ABB Response

Customer Benefit

© ABB| Slide 41

Power & AutomationPower & Automation

September 21, 2016

Short CircuitSummary

ABB Power Consulting

One of the most vital element in Power System Planning – “Short Circuit Current”One of the most vital element in Power System Planning – “Short Circuit Current”

• Short Circuit Studies are MUST on regular basis.

• Maximum and Minimum short circuit currents; both are equally important

• Short circuit currents are formed up on AC and DC components which have different decay.

• Different network parameters decide the value of the short circuit currents in system.

• There are different challenges for high & low value of the short circuit currents in system which affectthe safety of person and equipments

• ABB has an rich experience of dealing with different issues and providing different solutions whichhave added value to customer requirements.

Short Circuit Currents decide the system economy, availability & safetyShort Circuit Currents decide the system economy, availability & safety


Short CircuitSpeaker Introduction

Nihar S Raj, Business Head – Power Consulting (Asia) , …file/Short+circuit.pdf · ·...

Documents

Transcript of Nihar S Raj, Business Head – Power Consulting (Asia) , …file/Short+circuit.pdf · ·...