8.Line Distance Protection

(1)

The year of Profitable Growth

Module 10B:

(2)

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 0,6s 0,3s 0,3s 0,6s 0,6s 0,3s 0,3s

(3)

Earth FaultEarth

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

(4)

Earth FaultEarth

6 loops:

3 phase- phase loops and

3 phase- ground loops

phase- phase -loop:

_U

_L1-L2

_{= Z}

_L

_{( I}

_L1

_{- I}

_L2

₎

Measured current measured voltage

Z

_L

= R

_L

+ j X

_L

Z

_E

= R

_E

+j X

_E

I

_L1

I

_L2

I

_L3

I

_E

Z

_L

Z

_E

U

_L1

U

_L2

U

_L3

(5)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral

phase-ground-loop:

_U L1 =



L1 · ( RL+ j XL )-



E · ( RE +j XE)



_L1,



_E measured current U_L1 measured voltage

The same applies to the remaining loops

I

_L1

I

_L2

I

_L3

I

_E

Z

_L

Z

_E

U

_L1

U

_L2

U

_L3

Z

_L

= R

_L

+ j X

_L

Z

_E

= R

_E

+j X

_E

(6)

Z

_L Z_LF1 Z_LF2

R

_F

R

_F

Z

_Load

D

F1

F2

X

R

Z

L ZLF2



_SC1



SC2



_L RR

Z

F1

Z

F2 RR

Z

Load ZLF1 Fault area distance relay operating characteristic Increasin g load Fault in reverse Maximum Load: Minimum voltage 0,9 Un Maximum current 1,1 In  Phase - Phase Fault R_R R_F / 2

Phase - Earth Fault R_R R_F /(1 + R_E/R_L)

(7)

time

D1

D2

D3

t

₁

t

₂

t

₃

Z

₁

Z

₂

Z

₃

distance



t = grading time

A

_B

_C

_D

Z

₁

= 0,85 Z

_AB

Z

₂

= 0,85 (Z

_AB

+ 0,85 Z

_BC

)

Z

₃

= 0,85 (Z

_AB

+ 0,85 (Z

_BC

+ 0,85 Z

_CD

))

Safety margin is 15 %:

- line error

- CT, VT error

- measuring error

Grading rules

:

(8)

Earth FaultEarth

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: 60 ms (3 cycles) / 40 ms (2 cycles) MV 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: 100 ms

static/digital-mechanical or vice versa: 75 ms digital-digital or static-static 50 ms

(9)



SC

Current area for forward faults



_SC

Current area for reverse faults



_SC

U

_SC R

Z

_SC

Z'

_SC

Impedance area for forward faults

Impedance area for reverse faults

X



_SC

current / voltage diagram

impedance diagram

Fault location

Where is the fault ?

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

(10)

Earth FaultEarth

faulty phase voltage

V_f I_f V_L2 V_L3

I

_f

V

_L2

V

_L3

V

_L1

I

_f

V

_f

V

~

Z_line Z_grid relay fault L1-E

Method 1

_{Method 2}

V

_L1

V

_L1

V

_f

(11)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral I I>> I> U_I>> U_I> U_N U digital electro-mechanical Power system

Relay

line E E Z_S U_SC Z_SC I_SC U_SC _SC U_SC

G

(12)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral 5 0 % 1 0 0 %

U /U

_N

I>

_I

_

_>

_{I > >}

U (I

_

> )

U (I > > )

X X R R ₂ ₁ ₁ ₂

detection (U-I--starting)

(13)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral X R forw_ards for w a rds re v_e rs_e reve_rse  Load Load Z1 Z2 Z4 Z3 Z1B Z5 Line  Distance zones

Inclined with line angle 

Angle  prevents overreach of Z1 on faults with fault resistance that are fed from both line ends

Fault detection

no fault detection polygon: the

largest zone determines the

fault detection characteristic simple setting of load

encroachment area with R_min and _Load

(14)

Z

_L1-L2

Z

_L3-L1

Z

_L1-E

X

R

quadrilateral

MHO

U_L1 - U_L2 U_L3 - U_L1 U_L3 I_E U_L2 IL1 U_L1 _K I_L1 IL2 I_L3 I_E L1 L2 L3 E U_L1U_L2U_L3 distance relay

im p e d a n c e o f

h e a lth y lo o p s :

Z

_{L 2 -E =}

U

L 2

I

L 2

- K

E

· I

E

Z

_{L 3 -E =}

U

L 3

I

_{L 3}

- K

_E

· I

_E

U

_{L 1}

- U

_{L 2}

Z

_{L 1 -L 2 =}

I

_{L 1}

- I

_{L 2}

Z

_{L 2 -L 3 =}

U

L 2

- U

L 3

I

_{L 2}

- I

_{L 3}

im p e d a n c e o f

fa u lte d lo o p :

Z

_{L 1 - E =}

U

L 1

I

_{L 1}

- K

_E

· I

_E

(15)

Earth FaultEarth

 Intelligent phase selection:

 Impedance comparison

 Symmetrical component analysis

 Load compensation

 Pattern recognition

I₁ I₂ I₀ G G G G I_F/3 Z L3-E Z L1-L2 Z L3 - L1 Z L1-E X R quadrilateral MHO L₂ L₁ L₃ I₂ I0 Z L2-E

Distance protection Modern methods of phase

selection

(16)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral fault Impedance comparison of fault loop impedances

Comparison of I₂ and I₀components comparison of Load compensated currents n=1 n=1 n=1 n=1 n = number of detected fault loops

N Y

(17)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral Sector A Sector C Sector B mar gin I₂ aI₂ a2_I 2 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





2 0 2 2 0 L3 L2 2 L1 L3 L2 L1

a

3

1

3

1 I

I























2 0 2 0

:

L₁-E or L₂-L₃-E fault

:

L₂-E or L₃-L₁-E fault

:

L₃-E or L₁-L₂-E fault

Phase selection Differenciating between single and

double Ph-E fault

(18)

Earth FaultEarth

Using a signal model (Kalman-Filter)

R

V

I

L

Z = R + j

 L

Phasors

V = I



Z

Estimate the phasors V and I using the least squares method (minimised errors)











A



t A A k

A

k

T

B

k

T

e

C

k

T

y

_

























sin



₀

cos



₀ 

cos



₀

y

_k

is the sampled value (v or i) - by assuming

 = 60 ms the following simplification results

Im

a

current

(19)

Earth FaultEarth

Fast adaptive impedance measurement

Filters with different lengths

0 10 20 30 40 50 60 70 80 ms Estimate 1 (n=5) Estimate 2 (n=6) Estimate 3 (n=8) Estimate 4 (n=10) Normal 1 (n = 21) Normal 2 (n = 26) Normal 3 Jump detected Estimate 5 (n=13) Estimate 6 (n=15)

Least Square Estimate with quality control

Adaptive Zone restriction

(20)

Earth FaultEarth

1. Fast operation

 Use short data window

2. High accuracy

 High selectivity

3. Signal distortion do not cause delay or maloperation

X

R

(21)

G

V

F

Z

_L

E

If

distance relay

SIR (Source Impedance Ratio) describes the ratio

between the source impedance and the line impedance!

L S

Z

SIR



High SIR = Small loop voltage V

_F

in case of a fault at the end of the line

SIR

E

V

_f





1 SIR - Definition

(22)

Earth FaultEarth

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*

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

(23)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral S I R = 1 (A -G ) 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 % o f z o n e s e t t in g t r ip p in g t im e ( m s )

Trip time curves at SIR = 1

7SA522

Other relays

(24)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral S IR = 3 0 ( A - G ) 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 % o f z o n e s e t t in g t r ip p in g t im e ( m s )

Trip time curves at SIR = 30

7SA522

Other relays

(25)

D

A

D

B

D

C



>>

D



_>t





Z

_T

Z

₁

Z

₂

Z

₃

Z

₁

= 0.85 Z

_A-B

Z

₃

= 0.85 [ Z

_A-B

+ 0.85 (Z

_B-C

+ 0.85 Z

_C-D

) ]

Z

₂

= 0.85 (Z

_A-B

+ 0.85 Z

_B-C

)

Grading according_{the recommendation}

with the safety margin of 15%.

(26)

0.6

0.3 grading time

(s)

(27)

L2

L3

L4

L1

Z2

Z1

Z3

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

(28)

Earth FaultEarth

compensated system neutral earthing

G

B A C D Z₁ Z2... D Z_T

Neutral Earthing with

Peterson Coil or Isolated or Solid

During single phase earth fault:

(29)

Earth FaultEarth

Earth Fault Current - Pick-Up Characteristic

Measuring errors and non-symmetry may not cause

incorrect pick-up by earth fault current threshold

(30)

Earth FaultEarth

Earth Fault Detection Logic

Normal pick-up:

3I0

(31)

Earth FaultEarth

Earth fault detection during one pole open condition

During the 1 pole open condition, load current flows

in the earth path.

Magnitude comparison of the remaining 2 phases

prevents incorrect pick-up

(32)

Phase-to-Earth loop:

Phase-to-Phase loop:

Fault loop formulas



R

jX

 

I



V

_









R_L + j X_L I_L1 R_E + j X_E V_L1 V_L2 V_L3 I_L2 I_L3 I_E

Relay

location

Line and earth impedance are measured



























































E L E L L E L E L L L E E E L L L L

I

X

I

jX

I

R

I

R

V

jX

R

I

jX

R

I

V

1 1 1 1 1

(33)

Earth FaultEarth

Numeric impedance calculation, ph-ph-loop

Infeed L1 L2 L3 E R_fwd X_fwd(L_fwd)

R_ret X_ret(L_ret)

to remote line end



_fwd



ret U_fwdU_ret relay

location fault_location

U

=

X













L3 L2 L3 L2 m L3 -L2

-I

I













L3 L2 L3 L2 L3 -L2

-e

=

I

U

R

L3 L2 L3 L2 L3 -L2

-I

I

-U

U

=

Z

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

(34)

Earth FaultEarth

Estimation of arc resistance

X

Variable

R/X-setting

R

Worrington formula:

 

A

l

 

m

Ohm

I

28700

R

1,4 ARC





Rough

estimation:

U

_ARC

= 2500 V/m



  

 

A

Ohm

I

m

d

V/m

2500

ARC

R

F





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)

l=

1x1,3 = 1,3 m (110 kV

(35)

The year of Profitable Growth

Earth Fault Protection

(36)

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

(37)

Earth FaultEarth

Example: Single phase fault with infeed from 2 sides

IL1

IL2

IL3

IE

(38)

Earth FaultEarth

Symmetrical Component representation: L1-E Fault

B

Pos.

Seq.

I

_1A

Neg.

Seq.

Zero

Seq.

I

_1B

A

I

_2A

I

_2B

I

_0A

I

_0B

3 x

R

_Fault

U

_0A

U

_2A

U

_2B

U

_0B

(39)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral *)

I

_0P

U

_0P

U

_2P

I

0L,

I

2L

*) not needed for numerical relays,

U0Pmay also be internally calculated

(40)

Earth FaultEarth

(41)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral 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

7SA522 High Resistance Earth Fault Protection:

functional diagram

(42)

Earth FaultEarth

7SA522 - Directional earth fault protection: Settings

Settings of the stages:

Settings for direction: General settings:

(43)

Earth FaultEarth

Principle of phase selection logic with U and I

-Example L1-E

U

_L1E

< 0.6 U

_NOM

U

_L2E

> 0.7 U

_NOM

U

_L3E

> 0.7 U

_NOM

I

_L1E

> 2 I

_NOM

I

_L2E

< 1.2 I

_NOM

I

_L3E

< 1.2 I

_NOM

&

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

(44)

Earth FaultEarth

Phase Selection Logic - Sequence Components

L2-E L3-E L1-E I2 = I0 I2 = a*I0

Angle difference

I2/I0

Faulty Phase

-60° .. 60°

L1-E

60° .. 180°

L3-E

180° .. 300°

L2-E

(45)

Earth FaultEarth

 U_0P or U_2P 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<Min Teleprot

Inhibits echo send / releases block signal send Must be set to consider capacitive charging currents

 Teed load on line may reduce I₂ at relay location

 Teed earthed transformer may reduce I₀ at relay location

 DEF should be blocked during 1-pole ARC dead time

 Pick-up threshold biasing by I_ph > to avoid false operation with CT saturation

(46)

Earth FaultEarth

Directional comparison teleprotection scheme

rec. transm.

A

B

E/F. frwd. T_S & trip rec. & 1 E/F. frwd. T_S & trip transm & 1

T

_S

(47)

The year of Profitable Growth

(48)

Earth FaultEarth

Fault Protection in Systems with

Earthed Neutral Faults in this area are_{tripped from side 2 in}

t₂

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

Faults in this area are tripped from side 2 in

t₂ Normal setting: X₁= 0.85 X_L

1 2

Teleprotection is the solution

15% 70% 15%

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.

(49)

Teleprotection Schemes

Permissive Underreach PUTT

Permissive Overreach POTT

Blocking

(50)

Earth FaultEarth

PUTT

POTT

Blocking

Unblocking

Middle + long lines with FS-Carrier or FO

If second zone

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

Simple logic!

Pref. short lines with FS-Carrier (2-Ph coupling) FO or MW Only forward overreaching zone necessary Complex logic! Current reversal guide ECHO-logic (W I-logic)

All lines with AM-Carrier (less reliable channel)

Reverse looking blocking zone (fast) additionally necessary No monitoring of the AM-channel! EHV-lines with FS-Carrier. Continuous signal sending necessary (must be admissible) No reverse looking blocking zone necessary

(51)

Earth FaultEarth

7SA522 - Permissive underreach transfer trip (PUTT)

Z1(A) Z1 A B Z 1(B) Z 1B(A) Z 1B(B) & & (A) Z1 (B) OR T_S Trip Trip Further zones T1 Z1B T1B (A) trans-mit re-ceive Further zones trans-mit re-ceive T_S OR Z1B T1B (A) T1

T

_S

(52)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral Z1(A) T1B Z1B A B Z 1(B) Z 1B(A) Z 1B(B) & & & & (A) T1B Z1B (B) OR OR OR OR T_S Z1 or further zones trans-mit re-ceive Trip Trip re-ceive trans-mit Z1 or further zones T_S

(53)

7SA522 - Blocking

A

Z1 (A)

B

Z1 (B) Z1B (A) Z1B (B) Z1B T1B 1 trip rec. & d dt 40 ms Forw. (A) T_S & 1 (u,i) FD (A) (A) T_V 1 trip rec. further zones & Z1 or d dt 40 ms Forw. (B) T_S & 1 (u,i) FD (B) (B) T_V FD (A) FD (B) FD (A) FD (B) (A) Z1B T1B (B) transm. transm. further zones Z1 or

T

_S

T

_V

(54)

7SA522 - Unblocking

A Z1 (A) B Z1 (B) Z1B (A) Z1B (B) Z1B T1B TS & _1 trip transm. rec. further zones & Z1 or 1 TS & 1 trip transm. rec. & 1 f_U f_U f₀ f₀ Unblock-logic Unblock-logic U U B B

f₀ –Off frequency (monitoring frequency)

f_U –Unblock frequency (send frequency)

U –Unblocking signal B –Blocking signal (A) Z1B T1B (B) further zones Z1 or

(55)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral Z1 Z1B L1-E L2-E A 1 1 B 2 ₂ Z1 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

(56)

Earth FaultEarth

7SA522 - Teleprotection with three-terminal lines

Software provides

teleprotection of

three-terminal lines without

additional logic

(57)

Earth FaultEarth

7SA522 and 7SA6

Teleprotection via serial remote relay interface

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

(58)

Earth FaultEarth

Communication topology: Ring and Chain

side 1

side 2 side 2

side 1

side 3 Automatic change from

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

side 1 side 2

(59)

Earth FaultEarth

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

SIPROTEC 4: Familiar with digital communication networks

Features of the relay to relay communication

(60)

Earth FaultEarth

FO5: distance 1.5 km (with clock feed

-

back)

FO6 : distance 3.5 km

O

1300 nm1300 nm 10 km 10 km

O

1300 nm1300 nm 35 km 35 km

O

E

X21X21G703G703 internal internal internal external 820 nm 820 nm 1,5 km / 3 km 1,5 km / 3 km

FO7 : distance 10 km

FO8: distance 35 km

KU : hook

-

up to communication network

Note: km data are valid for worst

(61)

Earth FaultEarth

(62)

Earth FaultEarth

Weak Infeed Echo Logic

Receive

Signal

(63)

Earth FaultEarth

7SA522 - Echo and Tripping in case of no-infeed or

weak-infeed

Configuration

Settings

Note: The echo signal must be routed in

addition to the send signal on the transmission signal contact

Matrix

The receive signal is derived from : and

Phase segregated weak-infeed tripping

*Three-terminal schemes are supported as well

(64)

Earth FaultEarth

Overreach zone setting for POTT and Unblocking

Reverse looking zone (B)

A

B

Z1B(A) Z1B(B) correct

incorrect!

Reverse looking zone (A)

(65)

(66)



_L



_Z

S1



L



Z

L



L



Z

S2

E

₂

= E'

₂

E

₁

U

_A

_U

B

U'

_B

U'

_A



'

_L



_L



_'



E'

₁

E1

E2

ZS1 ZL _ZS2 U_A UB

Two Machine Problem

(67)

E

₁

= E

₂

E

₁

> E

₂

E

₁

< E

₂

X

R

Z

_S2

B

Z

_L

A

Z

_S1

Z

_Load



_'

load point

Power swing locus and relay characteristic in the

impedance diagram

(68)

Z

_S1

U

₁

E

₁

U

2

E

₂

Z

_S2

Z

_L

Z

_L

D

P

TP

= · sin



E

₁

· E

₂

X

_T 1 D 2 D 3

A

C

1

3

2

1

2

3

0

4

5

6 



P

_T

P

B

(69)

5

6

1

3

4 X

R

Z

_load

Z

_S1

Z

_S1

ZL

2

0 

₀

Power swing locus in the impedance plane

(70)

Earth FaultEarth

(Not used in 7SA52 and 7SA6)

Classic power swing detection

is restricted to slow swings

The setting of



Z may not be too large

to avoid load encroachment (typ. 5



)

During fast swings the time available

(



t) for detection of impedance vector

in the power swing zone is too short.

Z

(71)

Earth FaultEarth

•Novel space vector based principle

•Self-setting

•Small



Z (1 Ohm at In=5 A)

•Blocking up to high slip frequencies (7 Hz)

•Recognition of all fault types during swing

•Remains effective during single pole ARC

open time (3-phase set-up)



dZ/dt measurement

 Calculation of swing centre

and plausibility check

(+90

O

_<



_<-90

O)

Stable swing

Unstable swing

Z

X R

Advanced Power swing blocking techniques

(7SA513, 7SA522, 7SA6)

(72)

Earth FaultEarth

Power Swing detection: New method

dR

dX

(k-n) (k-n)

dR

_(k)

dX

_(k)

Power swing

X

R

Fault entry

Fault

impedance

Load

impedance

Transition from load to fault is fast

Power swing transition is slow



Continuos monitoring of the impedance trajectory

(73)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral Example: i/kA t/ms 500 u/kV t/ms 500 200 -3 6 3 R

Power swing

locus(E

_A

>E

_B

)

-90

O

180

O

0

O

90

O

X

_m

Slip

frequency

E

_B

A

Z

_A

a

Z

_l

b

Z

_B

B

~

E

_A Relay

Relay

(74)

Earth FaultEarth Fault Protection in Systems with Earthed Neutral t/s 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 iL1/A -4 -2 0 t/s 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 iL2/A -2 0 t/s 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 iL3/A -2 0 2 t/s 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 uL1/V -50 0 t/s 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 uL2/V -50 0 50 t/s 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 uL3/V -50 0 50 Dis. forward Dis.T.SEND >DisTel Rec.Ch1 Power Swing Example: 400 kV 400 km f_PS 2 Hz 3-pole fault