01-Dist Part 1_new
Transcript of 01-Dist Part 1_new
-
8/7/2019 01-Dist Part 1_new
1/22
Siemens AG 2006
Distance Protection for transmissionlines: part 1
Power Transmissionand Distribution
-
8/7/2019 01-Dist Part 1_new
2/22
Page 2 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Why impedance protection?
Situation: Meshed network and two infeedsDirectional overcurrent time relays
0,6s
0,6s
0,3s
0,3s
0,6s
0,6s
0,3s
0,3s
non-selective trip
-
8/7/2019 01-Dist Part 1_new
3/22
Page 3 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Localization of short-circuits by means of an impedance measurement:
- fault on the protected line
- fault outside the protected line
Z1
relay A
selectivity
relay A
Z2
Basic principle of impedance protection
-
8/7/2019 01-Dist Part 1_new
4/22
Page 4 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Distance measurement (principle)
6 loops: 3 phase- phase loops and 3 phase- ground loops
phase- phase -loop:
The same applies to the remaining loops
U L1-L2 = Z L ( I L1 - I L2 )
Measured current measured voltage
Z L = R L + j XL
Z E = R E +j X E
IL1
IL2
IL3
IE
ZL
ZE
UL1 UL2 UL3
-
8/7/2019 01-Dist Part 1_new
5/22
Page 5 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
phase-ground-loop: U L1 = - L1 ( R L + j XL )- - E ( R E +j X E)
- L1, - E measured current U L1 measured voltage
The same applies to the remaining loops
Distance measurement (principle)
IL1
IL2
IL3
IE
ZL
ZE
UL1 UL2 UL3
Z L = R L + j XL
Z E = R E +j X E
-
8/7/2019 01-Dist Part 1_new
6/22
Page 6 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Load and short-circuit impedances
ZLZLF1ZLF2
R F R FZLoadD
F1 F2X
R
ZL
ZLF2
NSC 1NSC 2
NL
RR
ZF1
ZF2
RR
ZLoad
ZLF1
Fault area
distance relayoperatingcharacteristic
Fault inreverse
direction Load area
Minimum Load Impedance:M inimum voltage 0,9 UnM aximum current 1,1 InM aximum angle s 30
Phase - Phase Fault
RR } RF / 2
Phase - Earth Fault
RR } RF /(1 + R E/R L)
-
8/7/2019 01-Dist Part 1_new
7/22
Page 7 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Principle of ( analog ) distance relayingISC
E
comparator
ZL
ZSC
ZReplica (line replica impedance)(corresponds to the set zone reach)
U1= k 1 USC = k 1 ISC ZSC.
U2=k 2 ISC ZReplica
ZS
R elay design:operation if
U1< U2i.e . ZSC < ZReplica
ZReplicaX
R
Ext . fault
Internal fault
A B
-
8/7/2019 01-Dist Part 1_new
8/22
Page 8 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Typical distance zone-characteristic
MHO-circle shifted circle
polarisedMHO-circle quadrilateral
ZR
ZSC
ZSC '
externalfault
internalfault
X
RN5
X
R
ZS = 0
ZS small
ZS high ZS
RF
ZL
X
R
centre
ZSC '
ZSC
setta le arccom ensati on
X
X
ZSC -L Rarc
RR
-
8/7/2019 01-Dist Part 1_new
9/22
Page 9 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Graded distance zones
time
D1 D2 D3
t1
t2
t3
Z1
Z2
Z3
distance
( t = grading time
A CB D
Z1 = 0,85 Z ABZ2 = 0,85 (Z AB + 0,85 Z BC )Z3 = 0,85 (Z AB + 0,85 (Z BC + 0,85 Z C D))
Safety margin is 15 %:- line error - C T, VT error - measuring error
Grading rules :
-
8/7/2019 01-Dist Part 1_new
10/22
Page 10 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
2nd Zone: It must initially allow the 1st zone on the neighbouring feeder(s) to clear the fault .The grading time therefore results from the addition of the following times:
operating time of the neighbouring feeder mechanical 25 - 80 msstatic: 15 - 40digital: 15 - 30
+ circuit breaker operating time HV / EHV: 60 ms (3 cycles) / 40 ms (2 cycles)M V up to about 80 ms (4 cycles)
+ distance relay reset time mechanical: approx . 60-100 msstatic: approx . 30 msdigital: approx . 20 ms .
+ errors of the distance relay internal timers mechanical: 5% of the set time, minimum 60-100 msstatic: 3% of the set time, minimum 10 msdigital: 1% of the set time, minimum 10 ms
+ distance protection starting time *) mechanical: O/ C starter: 10 ms, impedance starter: 25 ms
static: O/ C stater: 5 ms, impedance starter: 25 msdigital: generally 15 ms
+ safety margin (ca.) grading; mechanical-mechanical: 100 msstatic/digital-mechanical or vice versa: 75 msdigital-digital or static-static 50 ms
*) only relevant if the set relay times relate to the instant of fault detection / zone pick-up . This is the case with all S iemens relays . There areother relays where the time is adapted by software to relate to the instant of fault inception . In the latter case the starting time has to bedropped .
Determination of grading times(With numerical relays 250 ms is possible)
-
8/7/2019 01-Dist Part 1_new
11/22
Page 11 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
NSC
Cu rr t a r a f or f or a r d f a u lts
- SCCu rr t a r a f or r rs f a u lts
- SC
USC
R
ZSC
Z 'SC
I dan c a r a f o r f o r a r d f a u lts
I dan c a r a f o r r rs f a u lts
NSC
D t r i na tion of f a u lt d ir ction
cu rr n t / o lta g dia gr am impedan ce d ia gr am
Fa u lt loca tion Wh e r e is th e f a u lt ?
Th e impedan ce a lso sh ow s th e d ir e ction , b u t ....
-
8/7/2019 01-Dist Part 1_new
12/22
Page 12 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
direction may be determined together with the impedance measurementbut: problems may arise in certain cases (e .g . close-in faults)
separate directional determination required!
Why impedance measurement and directional determination separately ?
line characteristic
fault with arc resistancein forward direction
fault in forward direction
fault in reversedirection
close-in fault
X
R
A B
Impedance measurement and directional determination
-
8/7/2019 01-Dist Part 1_new
13/22
Page 13 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Alternatives for the directional measurement
faulty phase voltage
V f
I f
V L2
V L3
voltage memory(pre-fault voltage )
I f
V L2V L3
V L1
healthy-phase voltage(phase to phase voltage )
I f
V f
V L2-L3 V L2V L3
~
~
~
~
~
~
~
~
~
Z lineZ grid relay
fault L1-E
Method 1 Method 2
V L1
V L1 V f
-
8/7/2019 01-Dist Part 1_new
14/22
Page 14 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Directional measurementSummery of all 3 methods
uRI = uL2-L3
u f = uL1
Distance measurement
Direction measurementwith voltage memory
Direction measurementwith unfaulted voltage
i f (t)uL1
if
if
if
uL2-L3
uL1Measuringwindow
-
8/7/2019 01-Dist Part 1_new
15/22
Page 15 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Fault detection techniques
Over-current fault detectionVoltage dependantover-current fault detection
Voltage andangle dependantover-currentfault detection
I
U
I >>I > I N >
R
X
Impedancefaultdetection
Not in 7SA522
-
8/7/2019 01-Dist Part 1_new
16/22
Page 16 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
110 knet SCC ( )" 1 00 M
40 MuSC 120 k
400/1
l
I >st a rt 1 , I ND
OH -line95 /15 l/S tZ 'L , ; /km
' l)
10 20 30 40 50 60
I > start = 600 A
0,5
1,0
1,5
2,0
2,5
I SC (2) [kA]
l [km]
I SC(2) =U
N 1,1
2 ( Z S + Z S + Z L
reach of O C starter approx . 32 km
N T
Reach of over-current fault detection
ph-ph fault as an example
There is a limitationto the reach
-
8/7/2019 01-Dist Part 1_new
17/22
Page 17 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
I I >>I >
UI >>
UI >
U
Udigital
electro-mechanical
Power system
Relay
line
E
E
ZSUSC
ZSCI SC
USC
- SC
USC
G
G
Voltage controlled overcurrent fault detection
-
8/7/2019 01-Dist Part 1_new
18/22
Page 18 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Voltage and angle controlled overcurrent fault detection(U-I-N-starting)
50 %
100 %
U/U N
I /I 1 2 3
I > I N > I >>
U( I N >) U( I >>)
X X
R R
N2
N1N1
N2
This method is used in Germany
-
8/7/2019 01-Dist Part 1_new
19/22
Page 19 TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
X
R
N LoadLoad
Z1
Z2
Z4
Z3
Z1B
Z5
Line
E
Impedance zones of digital relays (7 S A6 and 7 S A52)
Distance zones
Inclined with line angle NAngle E prevents overreach of Z1
on faults with fault resistancethat are fed from both line ends
Fault detection
no fault detection polygon: thelargest zone determines thefault detection characteristic
simple setting of loadencroachment area withRmin and NLoad
-
8/7/2019 01-Dist Part 1_new
20/22
-
8/7/2019 01-Dist Part 1_new
21/22
Page 21TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Ring feeder: with grading against opposite end
0.6
0.3
grading time(s)
The same grading from both sides
-
8/7/2019 01-Dist Part 1_new
22/22
Page 22TLQ 2004 Distance Protection Part1
Siemens AG 2006
Power Transmission and Distribution
Grading in a branched radial system
L2
L3
L4
L1Z2
Z1
Z3
The impedances of the Z2 and Z3 must be grading with the shortest impedance