G. Ziegler. Digital Differential Protection

Подождите немного. Документ загружается.

G. Ziegler, 10/2005 page 130

Differential Protection Symposium

Belo HorizonteNovember 2005

N

Rush

I

ˆ

I

ˆ

Rated transformer power in MVA

Transformer Inrush current:

Amplitude and time constant

Rated powertime constant

in MVAin seconds

0,5....1,00,16....0,2

1,0 100,2 .....1,2

>101,2 ....720

51050100 500

6

10

2

4

8

12

G. Ziegler, 10/2005 page 131

Differential Protection Symposium

Belo HorizonteNovember 2005

Sympathetic Inrush

Wave form:

Transient currents:

1

I

2

I

Current circulating

between transformers

T

I

t

I

G

S

R

S

X

1

I

2

I

T

I

Transformer

being closed

T1

T2

Transformer

already closed

G

1

I

2

I

T

I

resistance

2

I

1

I

T

I

T1

T2

G. Ziegler, 10/2005 page 132

Differential Protection Symposium

Belo HorizonteNovember 2005

Transformer overfluxing

Deduction of wave form

Harmonic content

U/U

n

0,5

1,5

1,0

B

U

Gauß

4

10×

15

105

A

I

m

I

m

t

0

1020

ms

100120

140

160%

20

40

60

80

100

0

I

150

/I

50

I

250

/I

50

I

350

/I

50

I

50

/I

nTr

%

G. Ziegler, 10/2005 page 133

Differential Protection Symposium

Belo HorizonteNovember 2005

IR

Ir

Vector group adaptation with matching CTs

Current distribution with external ph-ph fault

87T

87T

87T

1/3

IS

IT

I1

I2

I3

R

S

r

s

t

Is

It

1

3

G

T

G. Ziegler, 10/2005 page 134

Differential Protection Symposium

Belo HorizonteNovember 2005

1/3

87T87T

87T

B

n

C

n

A

0

B

0

C

0

A

p

C

p

B

p

A

n

b

p

I

T

=3

30

O

30

O

a

p

c

p

c

n

b

n

a

n

3

I

c

=

c

p

c

n

a

n

a

p

3

I

a

=

IA

IB

IC

A

B

C

r

s

t

Ia

Ib

Ic

G

Yd1

Vector group adaptation and I

0

-elimination with matching CTs

Current distribution with external ph-E fault

G. Ziegler, 10/2005 page 135

Differential Protection Symposium

Belo HorizonteNovember 2005

A

B

C

a

b

c

G

87T

87T

87T

Traditional I

0

-elimination with matching CTs

Current distribution in case of an external earth fault

G. Ziegler, 10/2005 page 136

Differential Protection Symposium

Belo HorizonteNovember 2005

A

B

C

a

b

c

G

87T

87T

87T

Traditional I

0

-elimination with matching CTs

Current distribution in case of an internal earth fault

Ø Sensitivity only 2/3 I

F

!

Ø Non-selective fault

indication!

!

G. Ziegler, 10/2005 page 137

Differential Protection Symposium

Belo HorizonteNovember 2005

Traditional I

0

-correction with matching CTs

Current distribution with external ph-E fault

A

B

C

a

b

c

G

87T

87T

87T

3/1

G. Ziegler, 10/2005 page 138

Differential Protection Symposium

Belo HorizonteNovember 2005

A

B

C

a

b

c

G

87T

87T

87T

3/1

Traditional I

0

-correction with matching CTs

Current distribution with internal ph-E fault

G. Ziegler, 10/2005 page 139

Differential Protection Symposium

Belo HorizonteNovember 2005

Digital protection

contains:

Adaptation to

•Ratio U

A

/ U

B

•Vector group

IB1

IB2

IB3L3

IA1

IA2

IA3

∆I

∆I

∆I

L2

L1

U

A

(110 kV)

U

B

(20 kV)

7UT6

Transformer differential protection, connection

Software replica of matching transformers