Day 2 Part 3 Special Cases
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Transcript of Day 2 Part 3 Special Cases
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HV Power Seminar Nov 2009 1
Part 2
Energy Sector© Siemens AG 2008
Distance ProtectionSpecial Cases
Gustav Steynberg
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HV Power Seminar Nov 2009 2
For the application of distance protection
Special Conditions:
1. Short lines/cables
2. Parallel lines
3. Fault resistance
Energy SectorEnergy Automation© Siemens AG 2008
Page 2 November 09
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HV Power Seminar Nov 2009 3
G VF
ZL
E
If
SIR (Source Impedance Ratio) describes the ratio between the source impedance and the line impedance!
L
S
Z
ZSIR =
Short Lines: SIR - Definition
Energy SectorEnergy Automation© Siemens AG 2008
Page 3 November 09
distance relay
High SIR = Small loop voltage V Fin case of a fault at the end of the line
SIR
EV f +
=1
Note: SIR trip time curves are mostly related to zone 1, i.e. ZL = Z1
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HV Power Seminar Nov 2009 4
The SIR gives some information about the power of infeed and the line length!
SIR > 4 short line*SIR < 4 and >0.5 medium line*SIR < 0.5 long line*
SIR - Considerations about line length and infeed
Energy SectorEnergy Automation© Siemens AG 2008
Page 4 November 09
SIR < 0.5 long line*
For a distance relay the short line (large SIR) is more critical than on a long line (small SIR)!
*Classification according IEEE-Guide
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HV Power Seminar Nov 2009 5
The smallest reach setting of the underreaching Zone 1 will be determined with the minimum voltage measured for a fault at this zone boundary!
L
S
Z
ZSIR =
SIR
EV f +
=1
Short Lines: Definition of the shortest zone 1 setti ng
Z source
G
Z line
Vf
If
Energy SectorEnergy Automation© Siemens AG 2008
Page 5 November 09
To ensure sufficient measuring accuracy a minimum voltage must be available for a fault at the boundary of the zone 1 setting. By definition of the loop impedances a 3ph fault will result in the smallest voltage:
Vmin=minimum voltage for measured accuracy in stated tolerance (e.g. 5%)
The shortest line length (zone 1 setting) is therefore defined by Vmin and the SIR.
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HV Power Seminar Nov 2009 6
With minimum short circuit level on the busbar = 4 GVA, what is the smallest possible zone 1 setting is Vmin = 0.5V secondary?
L
S
Z
ZSIR =
SIR
EV f +
=1
Short Lines: Example - shortest zone 1 setting
Z source
400kV
Z line
Vf
If
Energy SectorEnergy Automation© Siemens AG 2008
Page 6 November 09
Ω=== 404000
4002
3
2
sourceph
N
S
UZ kVkVV 2400
100
5.0min_prim =⋅=
114123
4001
minmax =−
⋅=−=
V
ESIR
The shortest line length (zone 1 setting) is 0.35 Ohm primary. For a typical line reactance of 0.3 Ohm/km this corresponds to a line length of just over 1km.
Ω=== 35.0114
401
maxmin SIR
ZZ source
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HV Power Seminar Nov 2009 7
Parallel lines: Influence on distance measurement
G
Z line
IA
I
Z0 mutual 3.5
3.0
2.5
3.5
3.0
2.5
18.0
7
dResultant positive and negative sequence current enclosed = ZERO
Energy SectorEnergy Automation© Siemens AG 2008
Page 7 November 09
Z lineIB
Coupling of the parallel feeders for zero sequence current influences the measured fault impedance with ground loops.
15.0
7
10.6
7
12.8
7
18.0
7
Resultant coupling between two lines is only with zero sequence
Resultant zero sequence current enclosed = 3I0
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HV Power Seminar Nov 2009 8
Parallel lines: Influence on distance measurement
Z line
G
Z line
IA
IB
Z0 mutual
Z1
Z line
100%
100%
Influence of parallel line
Energy SectorEnergy Automation© Siemens AG 2008
Page 8 November 09
The loop voltage measured by Z1 for a single phase to ground fault as shown:
3
0__
MBEEAELineLGL
ZIZIZIU ⋅−⋅−⋅=−
The measured loop impedance:
AEL
MBE
LineGL IKI
ZI
ZZ_
_
030
⋅−
⋅−=−
distance 100%
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HV Power Seminar Nov 2009 9
Parallel lines: Compensation with modified XE/XL
Z line
G
Z line
IA
IB
Z0 mutual
Z1
Energy SectorEnergy Automation© Siemens AG 2008
Page 9 November 09
3
0__
MBEEAELLGL
XIXIXIU ⋅−⋅−⋅=−
XL
XEK X =0 XL
XK M
MX 3
00 =
For compensation, influence of the parallel by X0Mis considered:
The measured loop reactance with modified XE/XL=KX0’: Line
AEL
MBEEAELL
GL XIKI
XIXIXI
X =⋅−
⋅−⋅−⋅=−
_'
__
030
0000 ' IMXXX rKKK ⋅+=AE
BEI I
Ir
_
_0 =
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HV Power Seminar Nov 2009 10
Parallel lines: Compensation with measured IE of parallel line
Z line
G
Z line
IA
IB
Z0 mutual
Z1
Energy SectorEnergy Automation© Siemens AG 2008
Page 10 November 09
The loop voltage measured by Z1 for a single phase to ground fault as shown:
The measure loop impedance with modified parallel line compensation:
LineBEAEL
MBEEAELineL
GL ZIMKIKI
ZIZIZI
Z =⋅−⋅−
⋅−⋅−⋅=−
__
__
0030
3
0__
MBEEAELineLGL
ZIZIZIU ⋅−⋅−⋅=−
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HV Power Seminar Nov 2009 11
Phase-to-Earth loop:
Distance measurement Fault loop formulas
RL + j XLIL1
RE + j XE
VL1 VL2 VL3
IL2IL3
IE
Relay location
( ) ( )+⋅−+⋅= EEELLLL jXRIjXRIV 11
Energy SectorEnergy Automation© Siemens AG 2008
Page 11 November 09
Phase-to-Phase loop: ( ) ( )2121 LLLLLL IIjXRV −⋅+=−
Line and earth impedance are measured
Only the Line impedance is measured
( ) ( )
⋅−+
⋅−⋅=
⋅−⋅+⋅−⋅=+⋅−+⋅=
EL
ELLE
L
ELLL
EELLEELLL
EEELLLL
IX
XIjXI
R
RIRV
XIXIjRIRIV
jXRIjXRIV
111
111
11
)()(
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HV Power Seminar Nov 2009 12
(Ph-E-loop) - influence of fault resistance with set ting RE/RL and XE/XL - Siemens method
UPh-E
XL
ΙL RL
RF
XE
ΙE RE
ΙKX
ZL
Z
RF
1+kE,R
( ) ( ) LFEEELLLE-Ph III R +X j + R - X j + R = U ⋅U
Energy SectorEnergy Automation© Siemens AG 2008
Page 12 November 09
R
ZPh-E
with I E = - IL
RE
FL
L
E
L
EPh
Ph-E + k
RR
R
R +
I
U
R,11
Re
+
−
=
=
L
L
E
L
EPh
Ph-E X
X
X +
I
U
X =
=
−
1
Im
No measuring errorin the X-direction
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HV Power Seminar Nov 2009 13
(Ph-E-loop) - influence of fault resistance with sep aration of fault and line resistance - Not Siemens method
UPh-E
XL
ΙL RL
RF
XE
ΙE RE
ΙK
( ) ( ) LFEEELLLE-Ph III R +X j + R - X j + R = U ⋅
X
ZL
Z
RF
Energy SectorEnergy Automation© Siemens AG 2008
Page 13 November 09
with I E = - ILL
xTypeC X
K
IUX =
+=
1
Im
FLTypeC
rLTypeCTypeC
RRR
KXIUR
+=
⋅−= )tan(//Re ϕNote difference in fault resitance coverage with same zone setting!
R
ZPh-E
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HV Power Seminar Nov 2009 14
UPh-E
XL
ΙL RL
RF
XE
ΙE RE
ΙK
( ) E-L assume LFELLE-Ph IIII =⋅ R + Z + Z = U
This method is not used by SIEMENS
(Ph-E-loop) - influence of fault resistance with com plex KO setting - Not Siemens method
X
∆X
ZL ZPh-E
RF
1+k0
Energy SectorEnergy Automation© Siemens AG 2008
Page 14 November 09
k0R
k0ZZ
Zk0
UZ
+ 1 +
+ 1
+ 1 =
FL
E
LEL
E-PhE-Ph ⋅=
⋅− II
)-Ej(
L
E
FL
L
E
FLE-Ph
L
E
Le1
R
1
R then , to adapted setting If
ϕϕ⋅++=
++=
ZZ
Z
ZZ
ZZZZ
k0
Also an additional measuring error in the X-direction
R