Energy Automation
Proper detection and
treatment of power swing
to reduce the risk of
Blackouts
Siemens AG 2008
Energy Sector
Basics
I*XG
I*XL
I*XM
VG VM
sin( )
XG XL XM
P
Pmax
VA
VB
VG
VM
Page 2
20.01.16
Jrg Blumschein
90
180
Siemens AG 2008
Energy Sector
Influence of voltage angle
I*XG
P
Pmax
PM=PG
=120
I*XG
=60
I*XG
V
G
VG
=180
0
Page 3
90
20.01.16
VG
I*XL
I*XM
VB VM
I V I*XL
I*XM
A
I
I*XVM
VA I*XL VB
M
I
=60
=120
=180
VB
VM
VA=0
180
Jrg Blumschein
Siemens AG 2008
Energy Sector
Typical impedance trajectory
Z( = 0)
= 60
normal load condition
= 120
dangerous for
distance protection
Z( = 60)
Z( = 180)
Page 4
= 180
unstable power swing
out of step tripping
Z( = 120)
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Required characteristics for power swing detection
No settings are required, thus no complex calculation is needed.
Detection of power swing with frequencies up to 10Hz.
Detection of power swings that occur during single-pole open
condition and during faults.
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
Page 5
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Principle of power swing detection
X
Continuous
calculation and
monitoring of
Impedances
Zone
First impedance in
power swing area:
algorithm starts to
analyze the
impedance trajectory
automatically sized
power swing area
Page 6
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Main criteria for power swing detection
Page 7
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
monotony criterion
X
X1
X2
X11
X2
X2
R2
R2
R2
R1
R1
power swing if
R1 and
and R
R22 and
or
X1 and
and X
X22
have
have same
same directions
direction
no power swing if
R1 and R2 and
X1 and X2 have
different directions
Page 8
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
continuity criterion
power swing
if R or X
exceed a threshold
X
X
no power swing
if R and X are
below the threshold
R
R
Page 9
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
smoothness criterion
X
X1
X1
R2
R2
R1X2
R1
power swing if
R1 nearly R2
and X1 nearly X2
X2 no power swing if
R1 strong vary from R2
or
X1 strong vary from X2
Page 10
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
If three machines oscillating against each other
Impedance trajectory
will not follow a
perfect elliptical path
difficult to manage
with blinders
Page 11
20.01.16
Jrg Blumschein
easy to detect with
criteria monotony,
continuity and
smoothness
Siemens AG 2008
Energy Sector
Quick redetection of power swing after fault inception
Page 12
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Secure power swing detection during open pole condition
Page 13
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Necessity of power swing detection, example
D1
Trip
Trip
D2
Busbar
2
Busbar
1
3-phase-fault initiates
a power swing in the
transmission network
Transmission network
D3
Trip
3-phase
fault
Trip
Relay 5
D4
Power swing blocking
function prevents the
distance relays D1 ..
D4 from unselective
tripping
Distribution network
Page 14
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Impedance Vector for Distance Relay D4
X
3-phase reverse fault:
Impedance vector
jumps to ZFault
Zone Z2
Zone Z1
ZLoad
R
ZFault
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
20.01.16
power swing is initiated by
the reverse fault:
The impedance moves
on a circular trajectory
Jrg Blumschein
Siemens AG 2008
Energy Sector
Page 16
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Rotor angle and impedance trajectories for stable
and unstable power swing
distinguish between
stable and unstable
power swing
Trip only for
unstable out of step
condition
strong network: trip
as fast as possible
weak network: keep
the line in service
as long as possible
Page 17
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
Basic signals for out of step detection
1. power swing detected
2. impedance in out of
step area detected
3. impedance crosses
the line angle from
the right side
4. impedance leaves
power swing area
at opposite side after
complete crossing
5. impedance crosses
the line angle from
the left side
Page 18
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
special out of step tripping logic
Individual out of step trip by logical combination of basic signals
Trip, if the impedance crosses the line angle 3 times inside the
predefined area
Page 19
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
special out of step tripping scheme
6. Trip, if the impedance
crosses the line angle
3 times inside the
predefined area
Out of step area
Trip
6
No Trip
Page 20
out of step protection
becomes a selective
function
20.01.16
7. no trip, if the
impedance crosses
the line angle outside
the predefined
out of step area
Jrg Blumschein
Siemens AG 2008
Energy Sector
conclusion
For the protection of the transmission systems of the future we
recommend a strong coordination of power swing detection, distance
protection and out of step protection.
This method, successfully used in Kazakhstan and Romania has the
following advantages:
distance protection for selective clearing of faults in the protected
zone
block distance protection in case of power swing
flexible out of step protection to split the grid selectively according
grid study
optimal coordination of distance protection and out of step protection
by using the same algorithm for power swing detection
Page 21
20.01.16
Jrg Blumschein
Siemens AG 2008
Energy Sector
