8.Line Distance Protection

Module 10B: Line Distance Protection The year of Profitable Growth

Global network of innovation

Power Transmission and Distribution

Why impedance protection? Power Automation Progress. It‘s that simple.

Earth FaultEarth Fault Protection in Systems with Earthed Neutral

Situation:

Meshed network and two infeeds Directional overcurrent time relays

0,6s

0,3s

0,6s

0,3s

0,6s

0,3s

0,6s

0,3s

non-selective trip

Power Automation

2


Basic principle of impedance protection Power Automation Progress. It‘s that simple.

Localization of short-circuits by means of an impedance measurement: - fault on the protected line


Z1

relay A

- fault outside the protected line Z2 relay A

selectivity

Power Automation

3


Distance measurement (principle) Power Automation Progress. It‘s that simple.

IL1 ZL ZL = RL + j XL

IL2 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

IL3 IE

ZE = RE +j XE

ZE

UL1 UL2 UL3 6 loops:

3 phase- phase loops and 3 phase- ground loops

phase- phase -loop:

UL1-L2 = ZL ( IL1 - IL2) Measured current measured voltage

The same applies to the remaining loops 06.08.97 dtgerdis3

Power Automation

4


Distance measurement (principle) Power Automation Progress. It‘s that simple.

IL1 ZL IL2


ZL = RL + j XL

IL3 IE

ZE = RE +j XE

ZE

UL1 UL2 UL3 phase-ground-loop:

UL1 = L1 · ( RL + j XL )- E · ( RE +j XE)

L1, E measured current UL1

measured voltage

The same applies to the remaining loops

06.08.97 dtgerdis3

Power Automation

5


Load and short-circuit impedances Power Automation Progress. It‘s that simple.

ZL

distance relay operating characteristic

ZLF1 ZLF2

Fault area

X


ZL

D

ZLF2

RR

RF F1

RF F2

ZLoad

Phase - Phase Fault

ZF2

RR  RF / 2

ZLoad RR

ZLF1

ZF1

as Incre

L SC2

Fault in reverse direction

SC1

oad ing l

Phase - Earth Fault RR  RF /(1 + RE/RL) Maximum Load: Minimum voltage 0,9 Un Maximum current 1,1 In Nominal angle  30°

R Load area

Power Automation

6


Graded distance zones Power Automation Progress. It‘s that simple.

Z3

t = grading time Z2

time Earth FaultEarth Fault Protection in Systems with Earthed Neutral

Z1

t3 t2

t1

A

B D1

C D2

D D3 distance

Grading rules:

Z1 = 0,85 ZAB Z2 = 0,85 (ZAB + 0,85 ZBC) Z3 = 0,85 (ZAB + 0,85 (ZBC + 0,85 ZCD))

Safety margin is 15 %: - line error - CT, VT error - measuring error

Power Automation

7


Determination of grading times (With numerical relays 250 ms is possible) Power Automation Progress. It‘s that simple.

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 ms static: 15 - 40 digital: 15 - 30


+ circuit breaker operating time

HV / EHV: MV

60 ms (3 cycles) / 40 ms (2 cycles) up to about 80 ms (4 cycles)

+ distance relay reset time

mechanical: approx. 60-100 ms static: approx. 30 ms digital: approx. 20 ms.

+ errors of the distance relay internal timers mechanical: 5% of the set time, minimum 60-100 ms static: 3% of the set time, minimum 10 ms digital: 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 ms digital: generally 15 ms

+ safety margin (ca.)

grading;

mechanical-mechanical: static/digital-mechanical or vice versa: digital-digital or static-static

100 ms 75 ms 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 Siemens relays. There are other 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 be dropped.

Power Automation

8


Determination of fault direction Power Automation Progress. It‘s that simple.

Fault location


Where is the fault ? Current area for forward faults

USC

SC

X

Impedance area for forward faults

SC

ZSC

SC R

SC Current area for reverse faults

current / voltage diagram

Z'SC Impedance area for reverse faults

impedance diagram

The impedance also shows the direction, but .... Power Automation

9


Alternatives for the directional measurement Power Automation Progress. It‘s that simple.


~

~

~

~

~

~

~

~

~

Zgrid

relay

fault L1-E

Zline

Method 1

Method 2 Vf

VL1 Vf

VL1

VL1

If

VL3

Vf

VL2

If

VL3

VL2-L3

VL2

healthy-phase voltage (phase to phase voltage)

faulty phase voltage

If VL3

VL2

voltage memory (pre-fault voltage)

Power Automation

10


Voltage controlled overcurrent fault detection Power Automation Progress. It‘s that simple.

SC

G

line

Power system


USC

G

Relay

ZS E

USC

ISC

digital

U

electro-mechanical

UN

ZSC

UI> UI>>

E

I>

I>>

I

USC

Power Automation

11


Voltage and angle controlled overcurrent fault detection (U-I--starting) Power Automation

X

Progress. It‘s that simple.

X 2

2 1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

1

R

R

U /U N 100 %

U (I > > )

U (I  > )

50 %

I>

I> 1

I> > 2

3

I/I N

This method is used in Germany Power Automation

12


Impedance zones of digital relays (7SA6 and 7SA52) w for

Power Automation Progress. It‘s that simple.

ard

X

s

Line

Distance zones Inclined with line angle  Angle  prevents overreach of Z1 on faults with fault resistance that are fed from both line ends

Z5 Z4


Z2 Z1B  rev e

Z1 rse



Load

Load

R

forw

Z3

ard

s

Fault detection

ers rev e

no fault detection polygon: the largest zone determines the fault detection characteristic simple setting of load encroachment area with Rmin and Load

Power Automation

13


Conventional relays: limiting of the starting characteristic area for phase-selective fault detection Power Automation

UL1 - UL2


IL1 IL2

L1 L2

IL3

L3

IE


UL1 UL2 UL3

UL1 K

Z L 1 -E

UL3

UL2 UL3 - UL1

quadrilateral

ZL3-L1

=

IL1

IE

X

ZL1-E

IL1

E

distance relay

ZL1-L2

im p e d a n c e o f fa u lte d lo o p :

im p e d a n c e o f h e a lth y lo o p s : U L2 Z L 2 -E = IL2 - K E · IE Z L 3 -E

=

IL3

=

U L1 - U L2 IL1 - IL2

Z L 2 -L 3

=

U L2 - U L3 IL2 - IL3

Z L 3 -L 1

=

U L3 - U L1 IL3 - IL1

R ZL2-E

U L3 - K E · IE

Z L 1 -L 2

MHO

ZL3-E

U L1 - K E · IE

Power Automation

14


Distance protection Modern methods of phase selection Power Automation Progress. It‘s that simple.

X Z

 Intelligent phase selection: quadrilateral

L1-L2 Z


Z

 Impedance comparison

L3 - L1

 Symmetrical component analysis  Load compensation

MHO

L1-E

 Pattern recognition

R Z

G

G

L3-E Z

L1 I2

L2-E

I0 G

I1

G

I2 L3

L2

IF/3

I0

Power Automation

15


Distance protection Stepped process of phase selection Power Automation Progress. It‘s that simple.

fault

n = number of detected fault loops Impedance comparison N of fault loop impedances


Comparison of I2 and I0 components comparison of Load compensated currents

N

N

n=1

Y

Y n=1

Y n=1

Y n=1 N Trip three-phase

Trip single-phase

Power Automation

16


Phase selection Differenciating between single and double Ph-E fault Power Automation Progress. It‘s that simple.

Sector A


I 0  1 I L1 I L2  I L3 3 I 2  1  I L1a2 I L2 a I L3  3 I0  I2 I 0  a2 I 2 I 0 a I 2

: L -E or L -L -E fault : L -E or L -L -E fault : L -E or L -L -E fault 1

2

3

2

3

1

3

1

2

gin r ma

I2

Sector C

a  I2

a2  I2

Sector B

1-Ph-E fault: After load compensation: Currents in the healthy phases are zero or have opposite phase position Ph-Ph-E fault: After load compensation: Currents in faulted phases have same amplitude and show a phase difference of 120 to 180 degree dependent on earthing conditions Power Automation

17


Method used in 7SA52 and 7SA6 to measure I and V Using a signal model (Kalman-Filter) Power Automation Progress. It‘s that simple.

I Earth FaultEarth Fault Protection in Systems with Earthed Neutral V = I

R

L

V

Phasors

Z = R + jL

 Z

Estimate the phasors V and I using the least squares method (minimised errors) t    y k  A  sin  0 k  T A   B   cos  0 k  T A   e 

   C  cos  0 k  T A   

yk is the sampled value (v or i) - by assuming  = 60 ms the following simplification results

y k  a  sin  0 k  T A   b  cos  0 k  T A 

Im

current a

voltage a b

b

Power Automation

Re

18


Fast adaptive impedance measurement Filters with different lengths Power Automation Progress. It‘s that simple.

E. g. Zone Z1

Earth FaultEarth Fault Protection in Systems with Earthed Neutral Estimate 1 (n=5) Estimate 2 (n=6) Estimate 3 (n=8) Estimate 4 (n=10) Estimate 5 (n=13) Estimate 6 (n=15) Normal 1 (n = 21) Normal 2 (n = 26) Normal 3 0 Jump detected

10

20

30

40

50

60

70

80 ms

Least Square Estimate with quality control Adaptive Zone restriction Power Automation

19


Conclusion Power Automation Progress. It‘s that simple.

X Earth FaultEarth Fault Protection in Systems with Earthed Neutral

R

1. Fast operation  Use short data window 2. High accuracy 

High selectivity

3. Signal distortion do not cause delay or maloperation

Power Automation

20


SIR - Definition Power Automation Progress. It‘s that simple.


SIR (Source Impedance Ratio) describes the ratio between the source impedance and the line impedance!

If ZL

G

E

VF

distance relay

SIR 

ZS ZL

E Vf  1  SIR

High SIR = Small loop voltage V F in case of a fault at the end of the line Note: SIR trip time curves are mostly related to zone 1, i.e. ZL = Z1

Power Automation

21


SIR - Considerations about line length and infeed Power Automation Progress. It‘s that simple.

The SIR gives some information about the power of infeed and the line length! Earth FaultEarth Fault Protection in Systems with Earthed Neutral

SIR > 4 SIR < 4 and >0.5 SIR < 0.5

short line* medium line* long line*

For a distance relay it is more hard to operate on a short line (large SIR) than on a long line (small SIR)! *Classification according IEEE-Guide

Power Automation

22


Trip time curves at SIR = 1 Power Automation Progress. It‘s that simple. I R =11 (A (A -GG) ) SIRS = 50

45

40

Other relays

35

t rip p in g t im e ( m s )


30

25

20

7SA522

15

10

5

0 0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

% o f z o n e s e t t in g

Power Automation

23


Trip time curves at SIR = 30 Power Automation Progress. It‘s that simple.

S IR = 3 0 ( A - G )

SIR = 30 (A G) 50

45

40

Other relays 35

t rip p in g t im e ( m s )


30

25

20

7SA522

15

10

5

0 0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

% o f z o n e s e t t in g

High SIR (low voltage) doesn’t effect the tripping time in numerical relays

Power Automation

24


Zone grading chart, radial feeder Power Automation Progress. It‘s that simple.

Z3 Z2 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

Z1

A

D

B

C

D

D

D

>> ZT >t



Z1 = 0.85 ZA-B

Z2 = 0.85 (ZA-B + 0.85 ZB-C) Z3 = 0.85 [ ZA-B + 0.85 (ZB-C+ 0.85 ZC-D) ]

Grading according the recommendation with the safety margin of 15%.

Power Automation

25


Ring feeder: with grading against opposite end Power Automation Progress. It‘s that simple.

gradingtime (s) 0.6 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

0.3

The same grading from both sides

Power Automation

26


Grading in a branched radial system Power Automation Progress. It‘s that simple.

Z3

L2


Z1

L1

L3

Z2

L4 The impedances of the Z2 and Z3 must be grading with the shortest impedance Power Automation

27


Distance protection: Earth fault in system with solid, isolated or compensated system neutral earthing Power Automation Progress. It‘s that simple.

D

A ZT Z1


C

B

Z2...

G D

Neutral Earthing with Peterson Coil or Isolated or Solid

During single phase earth fault: The short circuit current magnitude depends on the neutral earthing method. Power Automation

28


Earth Fault Current - Pick-Up Characteristic Power Automation Progress. It‘s that simple.


Measuring errors and non-symmetry may not cause incorrect pick-up by earth fault current threshold Power Automation

29


Earth Fault Detection Logic Power Automation Progress. It‘s that simple.


Normal pick-up:

3I0

Heavy load on long line:

3I2

For very small earth current: compensated system)

3U0 (isolated or

Power Automation

30


Earth fault detection during one pole open condition Power Automation Progress. It‘s that simple.


During the 1 pole open condition, load current flows in the earth path. Magnitude comparison of the remaining 2 phases prevents incorrect pick-up Power Automation

31


Distance measurement Fault loop formulas Power Automation Progress. It‘s that simple.

IL1

Relay location

RL + j XL

IL2 IL3 VL1 VL2 VL3


IE

Phase-to-Earth loop:

RE + j XE

VL1  I L1  RL  jX L   I E  RE  jX E      R X VL1  RL   I L1  E  I E   jX L  I L1  E  I E  RL XL     Line and earth impedance are measured

Phase-to-Phase loop:

VL1 L 2  RL  jX L   I L1  I L 2  Only the Line impedance is measured

Power Automation

32


Numeric impedance calculation, ph-ph-loop Power Automation

relay location


fault location

L1


fwd

L2

ret Infeed

L3

Rfwd

Xfwd(Lfwd)

Rret

Xret(Lret)

to remote line end

Ufwd Uret

E

ZL2 - L3 =

U L2 - U L3 IL2 - IL3

U L2 - U L3  RL2 - L3 = Re    IL2 - IL3 

U L2 - U L3  XL2 - L3 = Im    IL2 - IL3 

With the measurement of phase to phase voltages and currents the fault impedance (impedance to fault location) is correct calculated

Power Automation

33


Estimation of arc resistance Power Automation Progress. It‘s that simple.

Worrington formula:


Rough estimation: UARC = 2500 V/m

X

Variable R/X-setting

R ARC 

R ARC 

28700 IA 

1,4

 lm Ohm

2500 V/m   dm  Ohm I F A 

Phase-to-phase distances d= 3,5 m (110 kV) d= 7 m (220 kV) d= 11 m (380 kV) Insulator lengths (long-rod insulator)

R

l= l= l=

1x1,3 = 1,3 m (110 kV 2x1,3 = 2,6 m (220 kV) 3x1,3 = 3,9 m (380 kV)

Power Automation

34

Earth Fault Protection in Systems with Earthed Neutral The year of Profitable Growth



7SA522 High Resistance Earth Fault Protection: Features Power Automation Progress. It‘s that simple.

3 definite-time stages Earth (zero sequence) current protection, 4 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 power trafo Directional determination with V2 and I2 (negative sequence) Sensitive 3I0-measurement with a dynamic from 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 Power Automation

36


Example: Single phase fault with infeed from 2 sides Power Automation Progress. It‘s that simple.

IL1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

IL2 IL3

Zf IE

Power Automation

37


Symmetrical Component representation: L1-E Fault Power Automation Progress. It‘s that simple.

A


I1A

I1B

I2A

I2B

B

Pos. Seq.

Neg. Seq.

U 2A

U 2B

I0A Zero Seq.

U 0A

3x R Fault

I0B U 0B

Power Automation

38


Polarizing Options for Directional Earth Fault Relays Power Automation Progress. It‘s that simple.

Earth FaultEarth Fault Protection in Systems with Earthed Neutral *)

I0P *)

U0P U2P

I0L, I2L

not needed for numerical relays, U0P may also be internally calculated

Power Automation

39


Directional Characteristic (U0 and IY) Power Automation Progress. It‘s that simple.


Power Automation

40


7SA522 High Resistance Earth Fault Protection: functional diagram Power Automation Progress. It‘s that simple.

Earth fault direction Inrushstabilisation


EF IE> Echo EF Fault Det.

SOTF

Teleprotection

>EF Trip rel.

P

Direc. 3I0>>>

P

3I0>>>

= & EF>>> Trip

T

&

3I0>>> Def. Time Stage

>EF>>> block

3I0>> Def. Time Stage 3I0> Def. Time Stage P Direc. 3I0p P 3I0p

&

= &

EFp Trip

P3146 AddTdelay T(3I0/IN)

T

Inverse Time Stage

>EFp block

= Input signal (binary input)

P

= Parameter

= Output Signal (alarm, command)

Power Automation

41


7SA522 - Directional earth fault protection: Settings Power Automation Progress. It‘s that simple.

General settings: Earth FaultEarth Fault Protection in Systems with Earthed Neutral

Settings for direction: Settings of the stages:

Power Automation

42


Principle of phase selection logic with U and I Example L1-E Power Automation Progress. It‘s that simple.

UL1E < 0.6 UNOM Earth FaultEarth Fault Protection in Systems with Earthed Neutral

&

UL2E > 0.7 UNOM UL3E > 0.7 UNOM OR

Select L1-E with U / I

IL1E > 2 INOM IL2E < 1.2 INOM

&

IL3E < 1.2 INOM If selection with U / I is not successful (U too large or I too small) then symmetrical component method is used Power Automation

43


Phase Selection Logic - Sequence Components Power Automation Progress. It‘s that simple.


Angle difference I2/I0 -60° .. 60° 60° .. 180° 180° .. 300°

Faulty Phase L1-E L3-E L2-E

I2 = a*I0 L3-E

L1-E I2 = I0 L2-E

I2 = a2*I0

Power Automation

44


DEF protection, Critical application issues Power Automation Progress. It‘s that simple.

 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) compensated lines require higher current setting due to possibility of unsymmetrical gap flashover)

(series

 Separate current threshold setting for tele-protection : 3I0 to avoid false operation with CT saturation

Power Automation

45


7SA522 - Earth fault protection Directional comparison teleprotection scheme Power Automation Progress. It‘s that simple.

A Earth FaultEarth Fault Protection in Systems with Earthed Neutral

E/F. frwd.

&

&

B

TS

1

transm.

transm

trip

1

trip

rec.

TS

&

E/F. frwd.

&

rec.

TS

*Three-terminal schemes are supported as well Power Automation

46

Tele Protection The year of Profitable Growth


Selectivity in distance protection, Teleprotection is the solution Power Automation Progress. It‘s that simple.


Normal setting: X1 = 0.85 XL

2

1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

15% Faults in this area are tripped from side 2 in t2

70% Faults in this area are tripped from both sides in first-zone time

15% Faults in this area are tripped from side 2 in t2

Faults on approximately 70% of the line length are cleared without delay at both line ends Faults in the remaining 30% of the line length are cleared with a time delay. Remedy:

Exchange of information between the two line ends

Required:

Communication channel (PLC, microwave radio, fibre optic, etc.) Teleprotection logic (dedicated device or internal function in numerical protection devices) Power Automation

48


Teleprotection Schemes Power Automation Progress. It‘s that simple.


Permissive Underreach PUTT Permissive Overreach POTT Blocking Unblocking

Power Automation

49


Application of Teleprotection Schemes Power Automation Progress. It‘s that simple.

PUTT


POTT

Blocking

Unblocking

Middle + long lines with FS-Carrier or FO

Pref. short lines with FS-Carrier (2-Ph coupling) FO or MW

All lines with AM-Carrier (less reliable channel)

EHV-lines with FS-Carrier. Continuous signal sending necessary (must be admissible)

If second zone tripping for near end faults not allowed. Not applicable to lines with weak in feed.

Only forward overreaching zone necessary

Reverse looking blocking zone (fast) additionally necessary

No reverse looking blocking zone necessary

Simple logic! Complex logic! Current reversal guide ECHO-logic (W I-logic)

PUTT - Permissive Under-reach Transfer Trip

No monitoring of the AM-channel!

POTT - Permissive Overreach Transfer Trip

Power Automation

50


7SA522 - Permissive underreach transfer trip (PUTT) Power Automation Progress. It‘s that simple.

Z1(A)

A


Z 1B(B)

Z1 (A) Z1B T1B (A)

Z 1B(A)

Z 1(B)

TS T1

& Further zones

B

OR

transmit

Trip receive

transmit

Trip receive

TS T1

OR

Z1 (B) Z1B T1B (A)

& Further zones

TS

Power Automation

51


7SA522 - Permissive overreach transfer trip (POTT) Power Automation Progress. It‘s that simple.

Z1(A)

A

Z 1B(B)


Z1B T1B (A)

Z 1B(A)

Z 1(B)

& TS

& Z1 or further zones

B

OR

OR

transmit

Trip receive

transmit

Trip

OR

TS

OR

receive

&

Z1B T1B (B)


TS

Power Automation

52


7SA522 - Blocking Power Automation

FD (B)


Z1 (A)

A

FD (A)


Z1B (B)

Z1B(A) FD (A)

B

FD (B)

Z1 (B)

d dt

(u,i) (A)

d dt 40 ms

40 ms

Forw. (A) FD (A)

Forw. (B) &

1

TS

transm.

1

transm.

TS

TV

Z1B T1B (A) Z1 or further zones

(u,i) (B)

&

FD (B)

TV

&

1

trip

rec.

1

trip

Z1B T1B (B)

&

Z1 or further zones

rec.

TV

TS

Power Automation

53


7SA522 - Unblocking Power Automation Progress. It‘s that simple.

Z1 (A)

A

Z1B (B)


Z1B T1B (A)

Z1B (A)

Z1(B)

&


B

fU

1

TS

1

Unblocklogic

fU

transm. f 0

trip

U rec.

rec.

f0 – Off frequency (monitoring frequency) fU – Unblock frequency (send frequency)

TS

1

trip

U B

1

f0 transm.

B

&

Z1B T1B (B)

&

Unblocklogic

Z1 or further zones

U – Unblocking signal B – Blocking signal

TS

Power Automation

54


7SA522 - Phase segregated Teleprotection Power Automation Progress. It‘s that simple.

2

Z1

Z1B A Earth FaultEarth Fault Protection in Systems with Earthed Neutral

2

1

L1-E

Z1

1

B

L2-E

Z1B

A1 trips single-phase in L1 with a phase-segregated L1-receive-signal  Maximum of Selectivity Note: 3 binary channels for both directions are required or one serial link

Power Automation

55


7SA522 - Teleprotection with three-terminal lines Power Automation Progress. It‘s that simple.


Software provides teleprotection of threeterminal lines without additional logic

Power Automation

56


7SA522 and 7SA6 Teleprotection via serial remote relay interface Power Automation Progress. It‘s that simple.


PUTT and POTT schemes available: “plug and protect” Echo, weak infeed trip and direct trip Phase segregated Communication prepared for 2 or 3 terminal lines Transmission of operational measured values from the remote end(s) 28 remote signals can be configured in addition to the teleprotection scheme Number of remote relay interfaces: 7SA522 -> 2 7SA6 -> 1

> Power Automation

57


SIPROTEC 4 Communication topology: Ring and Chain Power Automation Progress. It‘s that simple.

side 2

side 2


Automatic change from closed ring to chain, if one connection is lost or not available

side 2

side 3 side 3

side 1

side 1

2 terminal line 3 terminals: Closed ring

side 1

3 terminals: Chain

Power Automation

58


SIPROTEC 4: Familiar with digital communication networks Features of the relay to relay communication Power Automation Progress. It‘s that simple.


Synchronous data transmission by HDLC- protocol Permanent supervision of the data transmission Measurement and display of signal transmission time Relay counts number of invalid telegrams: If transmission failure rate is too high the teleprotection scheme will be blocked -> switching to normal zone grading Settings for the data transmission: 64 kBit/s, 128 kBit/s or 512 kBit/s Communication device addresses -> Protection devices are clearly assigned to a defined protection section Detection of unwanted reflected data in the loops in communication network Data reflection for test purposes settable

Power Automation

59


Communication Options Power Automation Progress. It‘s that simple.

O

820 nm 1,5 km / 3 km

internal Earth FaultEarth Fault Protection in Systems with Earthed Neutral

O

FO5: FO6 :

distance 1.5 km (with clock feed-back) distance 3.5 km

1300 nm 10 km

FO7 :

distance 10 km

1300 nm 35 km

FO8:

distance 35 km

internal

O internal

O

E

external

X21 G703

KU : hook-up to communication network Note: km data are valid for worst-case conditions

Power Automation

60


Transient Blocking for Permissive Schemes Power Automation Progress. It‘s that simple.


Power Automation

61


Weak Infeed Echo Logic Power Automation Progress. It‘s that simple.


Receive Signal

No Distance Pickup Power Automation

62


7SA522 - Echo and Tripping in case of no-infeed or weak-infeed Power Automation Progress. It‘s that simple.

Configuration Settings


Matrix The receive signal is derived from : and *Three-terminal schemes are supported as well

Phase segregated weak-infeed tripping Note: The echo signal must be routed in addition to the send signal on the transmission signal contact

!

17.10.97 en513ase2

Power Automation

63


Overreach zone setting for POTT and Unblocking Power Automation Progress. It‘s that simple.


incorrect!

Reverse looking zone (A)

Z1B(B)

Z1B(A)

A

B

Reverse looking zone (B)

correct

Power Automation

64

Power Swing

The year of Profitable Growth



Power swing: Voltage diagram Power Automation

LZS1


Two Machine Problem E1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

E2 ZL

ZS1

UA

LZL

LZS2 E2 = E'2

E1

UA

ZS2

UB U'B

UB

U'A E'1



'

'L

L

If the angle becomes too large, the system stability can be lost

Power Automation

66


Power swing locus and relay characteristic in the impedance diagram Power Automation Progress. It‘s that simple.

E1 > E2


X

ZS2

B

E1 = E2

ZL

'



A

load point R

ZLoad

E1 < E2 ZS1

Power Automation

67


Dynamic system stability, equal area criterion Power Automation

U1


E1

ZS2

ZS1 D


U2

ZL

1

E2

E1 · E2 PTP =

ZL

· sin

XT

5

P 3 3 4 B

0 PT

A

C

1

6

D 2

2 2

D

1 0

0

1

90°

2

3

180° 

D

Power Automation

68


Power swing locus in the impedance plane Power Automation Progress. It‘s that simple.

X ZS1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

1

2 ZL 2

6

4 5

3 0 0

ZS1

Zload

R

Power Automation

69


Power swing detection: Classic Method (Not used in 7SA52 and 7SA6) Power Automation Progress. It‘s that simple.

Classic power swing detection is restricted to slow swings Earth FaultEarth Fault Protection in Systems with Earthed Neutral

The setting of Z may not be too large to avoid load encroachment (typ. 5 )

Z

During fast swings the time available (t) for detection of impedance vector in the power swing zone is too short.

t = time for transition of Z from outer to inner zone

Power Automation

70


Advanced Power swing blocking techniques (7SA513, 7SA522, 7SA6) Power Automation Progress. It‘s that simple.

•Novel space vector based principle Unstable swing Earth FaultEarth Fault Protection in Systems with Earthed Neutral

X

•Self-setting •Small Z (1 Ohm at In=5 A)

Z

•Blocking up to high slip frequencies (7 Hz) •Recognition of all fault types during swing

R

•Remains effective during single pole ARC open time (3-phase set-up)  dZ/dt measurement

Stable swing

 Calculation of swing centre and plausibility check (+90O<  <-90O)

Power Automation

71


Power Swing detection: New method Power Automation Progress. It‘s that simple.

X

Power swing

Fault impedance

Transition from load to fault is fast

dR(k-n) Fault entry


dX (k-n) dX (k)

dR(k)

Power swing transition is slow

Load impedance R



Continuos monitoring of the impedance trajectory



Monitoring of trajectory continuity



Monitoring of trajectory velocity



Evaluation of trajectory ellipse

Power Automation

72


Evaluation of the power swing process Power Automation

A


EA

~

ZA ~

a

Zl ~

b

ZB ~

B

~

EB

0O

Relay Earth FaultEarth Fault Protection in Systems with Earthed Neutral

Power swing locus(EA>EB) Slip frequency

Example: i/kA

-90O

6 3 -3

500

90O

Xm t/ms

u/kV 200

500

t/ms

180O

Relay

R

Power Automation

73


Novel power swing detection provides secure operation with swing frequencies of up to 7 Hz Power Automation Progress. It‘s that simple.


Example: 400 kV 400 km fPS  2 Hz 3-pole fault

iL1/A 0 -2

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

t/s

-4

iL2/A 0 -2

t/s

iL3/A 2

t/s

0 -2

uL1/V 0 -50

t/s

uL2/V 50 0 -50

t/s

uL3/V 50 0 -50

t/s

Power Swing >DisTel Rec.Ch1 Dis.T.SEND Dis. forward Dis. reverse Relay PICKUP Relay TRIP DisTRIP3p Z1Bmf 0,2

0,3

Power Automation

t/s

74


Fault detection during power swing Power Automation Progress. It‘s that simple.

I1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

I2

V1 The Power swing passes through the trip characteristic several times. Trip Single phase fault is detected and cleared.

Power Automation

75


Three phase fault during Power Swing Power Automation Progress. It‘s that simple.

I1 Earth FaultEarth Fault Protection in Systems with Earthed Neutral

V1

V2

V3 Trip

Three phase fault during power swing is detected and cleared Fault inception while swing is inside trip characteristic

Power Automation

76

8.Line Distance Protection

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