earth fault protection_new
TRANSCRIPT
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Siemens AG 2006
Earth Fault protection
Power Transmissionand Distribution
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Page 2 TLQ 2004 Distance Protection -Earth Fault Protection
Siemens AG 2006
Power Transmission and Distribution
7SA522
High Resistance Earth Fault Protection: Features
Earth (zero sequence) current protection, 4 stages 1 and 3 pole tripping with special phase selectors
3 definite-time stages
1 inverse-time stage: IEC, logarithmic inverse or ANSI characteristic
this stage can also be used as a 4th definite-time stage
Directional determination with 3V0 and/or Ipol of an earthed powertransformer
Directional determination with V2 and I2 (negative sequence)
Sensitive 3I0-measurement with a pick-up range: 0.005 A to 100 x In
Elimination of higher harmonics with special digital filters
Inrush-stabilisation with I0/100Hz
Teleprotection: Directional comparison, Blocking or Unblocking
Operation with weak infeed trip and echo
Instantaneous trip after switch-onto-fault
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Power Transmission and Distribution
Example: Single phase fault with infeed from 2 sides
IL1
IL2
IL3
IEZf
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Siemens AG 2006
Power Transmission and Distribution
Symmetrical Component representation: L1-E Fault
B
Pos.Seq.
I1A
Neg.Seq.
ZeroSeq.
I1BA
I2A
I2B
I0A
I0B
3 xR
Fault
U0A
U2A
U2B
U0B
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Power Transmission and Distribution
*)
I0P U0P U2P
I0L,
I2L
*) not needed for numerical relays,
U0P may also be internally calculated
Polarizing Options for Directional Earth Fault
Relays
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Siemens AG 2006
Power Transmission and Distribution
Directional Characteristic (U0 and IY)
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Siemens AG 2006
Power Transmission and Distribution
7SA522
High Resistance Earth Fault Protection: functional
diagram
Earth fault
direction
=
EF IE> Echo
3I0>>>EF>>> Trip
P
EFp Trip
Inrush-stabilisation
T(3I0/IN)
T
Tele-protection
T
SOTF
= &
&
3I0>>> Def. Time Stage
Inverse Time Stage
&
&
P
>EF>>> block
Direc. 3I0>>>
P Direc. 3I0p
>EFp block
P 3I0p
EF Fault Det.
>EF Trip rel.
3I0>> Def. Time Stage
3I0> Def. Time Stage
= Input signal(binary input)
P = Parameter = Output Signal(alarm, command)
P3146 AddTdelay
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Power Transmission and Distribution
7SA522 - Directional earth fault protection: Settings
Settings of the stages:
Settings for direction:
General settings:
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Power Transmission and Distribution
Principle of phase selection logic with U and I - Example
L1-E
UL1E < 0.6 UNOM
UL2E > 0.7 UNOM
UL3E > 0.7 UNOM
IL1E > 2 INOM
IL2E < 1.2 INOM
IL3E < 1.2 INOM
&
&
OR
Select
L1-E
with U / I
If selection with U / I is not successful (U too large or I too small)
then symmetrical component method is used
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Power Transmission and Distribution
Phase Selection Logic - Sequence Components
L2-E
L3-E
L1-E
I2 = I0
I2 = a2*I0
I2 = a*I0
Angle differenceI2/I0
Faulty Phase
-60 .. 60 L1-E
60 .. 180 L3-E
180 .. 300 L2-E
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U0P or U2P may fall below critical value (approx. 1 V secondary) and limit
relay high resistance earth fault sensitivity
Zero or negative sequence sources to be available behind relay location
Minimum settings at least > 3 times VT and CT inaccuracies
Current setting above line unsymmetry (M0 = Z01/Z0 or M2 = Z21/Z1)
(series compensated lines require higher current setting due to
possibility of unsymmetrical gap flashover)
Separate current threshold setting for tele-protection : 3I0 to avoid false operation with CT
saturation
DEF protection, Critical application issues
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7SA522 - Earth fault protection
Directional comparison teleprotection scheme
rec.
transm.
A B
E/F.
frwd. TS
& trip
rec.
&1
E/F.
frwd.TS
&trip
transm&
1
*Three-terminal schemes are supported as well
TS