G. Ziegler. Digital Differential Protection

G. Ziegler, 10/2005 page38

Differential Protection Symposium

Belo HorizonteNovember 2005

C

Ij

S

II ⋅+=

Φ

01

0

⋅+= j

I

O

2

1

2

3

30

⋅+= j

I

O

1

0

90

⋅+= j

I

O

2

3

2

1

60

⋅+= j

I

O

()

dtttII

O

C

⋅⋅⋅⋅=

∫

Φ

−

Φ

ωω

π

cos

2

1

360

()

dtttII

O

S

⋅⋅⋅⋅=

∫

Φ

−

Φ

ωω

π

sin

2

1

360

ωt

t=0

I

S

jI

C

I

t

ω

=

Φ

Orthogonal components of a current phasor

dependent on the position of the data window

Data window

G. Ziegler, 10/2005 page39

Differential Protection Symposium

Belo HorizonteNovember 2005

0123456

0

0,25

0,5

0,75

1,0

H

rel

f/f

n

Transfer function of a one cycle Fourier-filter

G. Ziegler, 10/2005 page40

Differential Protection Symposium

Belo HorizonteNovember 2005

Digital protection

Fast current phasorestimation

)ωt)t)ωt

)t(

i cos( C

t

e - cos( B sin( A

⋅+

τ

−

ω⋅+⋅=













Task: Estimation of the coefficients A, B, C on basis of

measured currents and voltages

Method: Gauß‘s Minimization of error squares:

(

)

2

(n)T)(n

k

N-kn

f - i Delta

∆⋅

=

∑

=

MIN

Delta = quality value

k = sampling number

N = length of data window

n = variable

∆T= sampling interval

k-N

k

N

i(t)

Data window

sampled values

G. Ziegler, 10/2005 page41

Differential Protection Symposium

Belo HorizonteNovember 2005

trip

restraint

B

I

A

II

B

I

A

II

+=Σ

+=∆

:quantity gRestrainin

:quantity Operating

I

AC

∆I

I

AC

, I

AS

j·I

BS

I

BC

∆I

I

BC

, I

BS

j·I

AS

∆I>

Differential protection with phasors(principle)

A

B

ΣI

G. Ziegler, 10/2005 page42

Differential Protection Symposium

Belo HorizonteNovember 2005

()

DARA1PT2PT1

t - t - t

2

1

t t ==

Signal transmission time:

t- t t

PT2A3B3

=

I

B( t

A3

)

I

B( t

B3

)

α

°⋅=α 360

T

t - t

P

A3B3

AB

∆I

c

u

r

e

n

t

p

h

a

s

o

r

s

.

t

A

1

c

u

r

e

n

t

p

h

a

s

o

r

s

.

t

B

3

t

A1

t

V

t

PT2

t

PT1

t

A1

t

A2

t

A3

t

A4

t

A5

t

AR

t

B1

t

B2

t

B3

t

B4

t

BR

t

D

Digital line differential protection

Synchronisation of phasors (ping-pong time alignment)

Sampling instant:

G. Ziegler, 10/2005 page43

Differential Protection Symposium

Belo HorizonteNovember 2005

Split path data transmission

Impact of unsymmetrical propagation time

α

I

1

I

2

α/2

I

1

I

2

∆I

[]

2

ms10

180

msT

sinI

2

sinII

o

⋅∆

⋅=

α

⋅=∆

Example:

Transmit channel time 3 ms

Receive channel time 4.2 ms

→ time difference ∆ = 1.2 ms

19.0I

2

ms10

180

ms2.1

sinII

o

⋅=

⋅

⋅=∆

∆I = 19%!

To keep the false differential current below about 2 to 5%, the

propagation time difference should not exceed about 0.1 to 0.25 ms!

Otherwise:

→ more insensitive relay setting

→ or GPS synchronisation

∆I ∆I

G. Ziegler, 10/2005 page44

Differential Protection Symposium

Belo HorizonteNovember 2005

Synchronisation of Differential relays via GPS

GPS

GPS-Empfänger Hopf

SIPROTECSIEMENS

L1 402,1A Max450.1A

L2 402,1A Max450.1A

L3 402,1A Max450.1A

E 00.0A

Anr. L1

Anr. L2

Anr. L3

Anr. Erde

Automat

RUNERROR

V4

SIPROTECSIEMENS

L1 402,1A Max450.1A

L2 402,1A Max450.1A

L3 402,1A Max450.1A

E 00.0A

Anr. L1

Anr. L2

Anr. L3

Anr. Erde

Automat

RUNERROR

V4

LWL

A

DCF-SIM

BE2

24V

7XV5654 Sync-Trans.

LWL

K2

K1

LWL

K1

K2

LWL

B

IRIG-B

RS232

16

GPS-Antenna

Y-cable 7XV5105

7SD52

IRIG-B Telegram

Line end 2

1

-

84

K2

+

3

-

+

DC

supply

24V

H

U

t0 max.

13841384

X1

Sec. impulse (highly accurate)

GPS

GPS-Empfänger

SIPROTECSIEMENS

L1 402,1A Max450.1A

L2 402,1A Max450.1A

L3 402,1A Max450.1A

E 00.0A

Anr. L1

Anr. L2

Anr. L3

Anr. Erde

Automat

RUNERROR

V4

SIPROTECSIEMENS

L1 402,1A Max450.1A

L2 402,1A Max450.1A

L3 402,1A Max450.1A

E 00.0A

Anr. L1

Anr. L2

Anr. L3

Anr. Erde

Automat

RUNERROR

V4

LWL

A

DCF-SIM

LWL

B

IRIG-B

RS232

16

GPS-Antenna

Y-cable 7XV5105

7SD52

IRIG-B Telegram

Line end 1

1843

DC

supply

24V

H

U

to max.

13841384

BE2

24V

7XV5654 Sync-Trans.

LWL

K2

K1

LWL

K1

K2

-

K2

+

-

+

X1

Sec. impulse (highly accurate)

G. Ziegler, 10/2005 page45

Differential Protection Symposium

Belo HorizonteNovember 2005

nGPS receiver with 2 optical outputs

(7XV5664-0AA00).

Output for IRIB-B telegram

and output for second/

minute pulse

n Galvanic separation between the

receiver and the tranceiver

7XV5654

n Optic/electric signal

conversion in the tranceiver

n Distribution of the electrical

signals via Y-bus cable to

port A of the relays (telegram)

n Electronic contact for the

minute pulse in case of

synchronisation through binary

input with battery voltage

Devices for GPS time synchronisation

Outdoor antenna

FG4490G10 for GPS

GPS receiver

7XV5664

Tranceiver

7XV5654

G. Ziegler, 10/2005 page46

Differential Protection Symposium

Belo HorizonteNovember 2005

Additional components for SICAM SAS

GPS-System

•24 satellites move in a height of

20 000km on 6 different paths

•Transmission frequency 1,57542GHz

•For a continuous time reception min. 4

satellites is necessary

•High accuracy : 1 usec

G. Ziegler, 10/2005 page47

Differential Protection Symposium

Belo HorizonteNovember 2005

I

∆

=|I

1

+ I

2

|

∆I

I

1

I

2

I

∑

= |I

1

|+ |I

2

|

a %

b %

I

∆

>

I

∑ b

Operating characteristic of digital differential relays

G. Ziegler. Digital Differential Protection

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