Day 1 Part 3 Power Swing

Energy Automation

treatment of power swing to reduce the risk of Blackouts Gustav Steynberg © Siemens AG AG 2008 Energy Sector

Basics

P

I *X

=

V G ⋅ V M X G

+ X L + X M

sin(ϑ )

I*X

I*X

P Pmax VA

VB

VG

VM

ϑ

0°

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Jörg Blumschein

90°

180° ϑ

© Siemens AG 2008 Energy Sector

Influence of voltage angle I*XG

P

I*XL

I*XM

Pmax PM=PG

ϑ=120°

I*XG

ϑ=60°

I*XG V

VG

VB VM I V I*XL I*XM A I I*XVM V I*XL V I

VG

VB

VM

=60° =120° ϑϑ=180°

VA=0

ϑ=180°

0°

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90°

Nov-09

180°

ϑ

Jörg Blumschein


Typical impedance trajectory Z(ϑ = 0°)

= 60° normal load condition

ϑ

X

= 120° dan erous for distance protection

ϑ

= 180° unstable power swing out of step tripping

ϑ

Z(ϑ = 60°)

φ

Z(ϑ = 180°)

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Z(ϑ = 120°)

Jörg Blumschein

R


Required characteristics for power swing detection 

No settings are required, thus no complex calculation is needed.



Detection of power swing with frequencies up to 7Hz. 7Hz .



Detection of power swings that occur during single-pole open cond condit itio ion n and and dur durin in faul faults ts..



Immediate unblocking of distance protection on all kind of faults occurring during power swing.



Quick detection of reappeared power swing after fault clearance.



Out-of-step tripping in case of unstable power swing

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Principle of power swing sw ing detection X

R

Zone



Continuous calculation and monitoring of Impedances



First impedance in power swing area: algorithm starts to analyze the impedance trajectory

automatically sized power swing area

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Main criteria for power swing sw ing detection

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monotony criterion



X ∆X1 ∆X2 2

11

∆R2 ∆R2 ∆R2

2

∆R1

∆R1

power swing if ∆R1 and ∆R22 and or ∆X1 and ∆X22 have same directions direction ∆R1 and ∆R2 and ∆X1 and ∆X2 have different directions

R

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Jörg Blumschein


continuity criterion



X ∆X

power swing if ∆R or ∆X exceed a threshold



if ∆R and ∆X are below the threshold

∆R

R

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Jörg Blumschein


smoothness criterion



X ∆X1 2

1

∆R2 ∆R2

∆R1∆X2

∆R1

power swing if ∆R1 nearly ∆R2 and ∆X1 nearly ∆X2



∆R1 strong vary from ∆R2 or ∆X1 strong vary from ∆X2

R

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If three machines oscillating against each other

X

R

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Jörg Blumschein



Impedance trajectory will not follow a perfect elliptical path



difficult to manage with blinders



easy to detect with criteria monotony, continuity and smoothness


Quick redetection of power swing sw ing after fault inception

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Secure power swing detection during open pole condition

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Necessity of power power swing detection, example D1

G

Trip

Trip D2



3-phase-fault initiates a power swing in the transmission network



Power swing blocking function prevents the distance relays D1 .. D4 from unselective tripping

Busbar 2

Busbar 1 Transmission network netw ork

D3

Trip

3-phase fault

Trip

Relay 5

D4

Distribution network

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Jörg Blumschein


Impedance Vector for Distance Relay D4 X

3-phase reverse fault:  Impedance vector jumps to Z Fault

Zone Z2 Zone Z1

Z Load

R

Z Fault

power swing is initiated by the reverse fault:  The impedance moves on a circular trajectory The power swing blocking function prevents an unselective trip, before the impedance vector enters the tripping zone Z1

Zone Zone Z3

Power Swing Detection Page 15

Nov-09

Jörg Blumschein


Day 1 Part 3 Power Swing

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