03 SEP-602A_ Distance Protection Basics

REL 670 Line Distance Protection IED

Substation Automation and Protection Training

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ABB AB, 2007

Distance protection basics

2007-10-03

Substation Automation and Protection Training

1

The principle of distance protection

ZK=Uk/ Ik Uk

Uk=0

Zk

metallic fault B

A

Ik

Z<

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ABB AB, 2007

The impedance is proportional to the distance!

2007-10-03 2

Substation Automation and Protection Training

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ABB AB, 2007

The principle of distance protection

2007-10-03

Substation Automation and Protection Training

3

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ABB AB, 2007

The principle of distance protection

2007-10-03 4

Substation Automation and Protection Training

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ABB AB, 2007

The principle of distance protection

2007-10-03

Substation Automation and Protection Training

5

The principle of distance protection

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ABB AB, 2007

Reach (measurement) independent of fault current level

Local current and voltage measurement. 2007-10-03 6

Substation Automation and Protection Training

Combination of reach and timers: selectivity

I can measure the fault distance…. I can put some timers…..

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ABB AB, 2007

What can I do?

2007-10-03

Substation Automation and Protection Training

7

Combination of reach and timers: selectivity t3 t2 t1

A

B

Z<

C

Z<

Distance protection has different functional zones with different impedance reaches

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ABB AB, 2007

With a combination of distance reach setting and functional delay for each zone selectivity is relatively easy to achieve.

2007-10-03 8

Substation Automation and Protection Training

Combination of reach and timers: selectivity

t3 t2 t1

A

B

Z<

C

Z<

Z<

Z< t3 t2

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ABB AB, 2007

t1

2007-10-03

Substation Automation and Protection Training

9

Combination of reach and timers: selectivity

t3 t2 t1

A

B f1

Z<

C

f2

Z< t3 t2

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ABB AB, 2007

t1

2007-10-03 10

Substation Automation and Protection Training

Combination of reach and timers: selectivity

t3 t2 t1

A

B

C f3

Z<

Z<

Z<

Z< t3 t2

©

ABB AB, 2007

t1

2007-10-03

Substation Automation and Protection Training

11

Which characteristic area? – Metallic fault The relay measures one impedance The impedance is a vector in the impedance plane (phasor).

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ABB AB, 2007

For a metallic fault (fault resistance = 0), the distance is proportional to the line impedance ZL.

2007-10-03 12

Substation Automation and Protection Training

Which characteristic area? – Resistive fault The relay measures the sum between line impedance (if fault at 100% of the line) and the fault resistance

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ABB AB, 2007

The impedance is a vector in the impedance plane (phasor).

2007-10-03

Substation Automation and Protection Training

13

Radial feeder – mapping of faults in Z plane How will a resistive fault look like in the impedance plane? Z1

I L1

Z1 L2

Tower Footing Resistance R5

R4

R3

R2

R1

Z1 L3

R1 ZN

N I

ZN

Z1

R2

R3

R4

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ABB AB, 2007

R5

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Substation Automation and Protection Training

Radial feeder – Quadrilateral characteristic The white region is the impedance locus we want to cover with the distance protection characteristic. R1 ZN Z1 R2

R3

R4

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ABB AB, 2007

R5

2007-10-03

Substation Automation and Protection Training

15

Quadrilateral vs. MHO characteristics Short line

Long line X

X RF Quad Rf Mho

ZL

ZL

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ABB AB, 2007

LOAD

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Substation Automation and Protection Training

LOAD

Power mapped in the Impedance Plane

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ABB AB, 2007

From Power data to PHS load data:

2007-10-03

Substation Automation and Protection Training

17

Power mapped in the Impedance Plane

jX

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ABB AB, 2007

R

2007-10-03 18

Substation Automation and Protection Training

Resistive fault, double infeed

VA = Z A ⋅ I A + (I A + I B ) ⋅ RF

Zm =

I +I VA = Z A + A B ⋅ RF IA IA

The fault has more or less fault resistance. If the fault is an arcing fault the fault resistance is normally very small.

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ABB AB, 2007

The influence of the fault resistance depends on the fault current infeed from the remote line end.

2007-10-03

Substation Automation and Protection Training

19

Resistive fault, double infeed UNDERREACH!

The fault resistance seen by the distance protection can be increased compared to its real value.

Zm = Z A +

ZA

Fault resistance settings according to “radial feeder” settings may not be enough. SOLUTION IS IN SETTINGS.

ABB AB, 2007

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I A + IB ⋅ RF IA

RF

I A + IB ⋅ RF IA

2007-10-03 20

Substation Automation and Protection Training

Resistive fault, double infeed – load export The apparent fault resistance can also get a phase shift, depending on the load conditions before the load. There is a risk that zone 1 will trip for faults outside its border on the reactive direction!.

Zm = Z A +

OVERREACH!

RF

I A + IB ⋅ RF IA

I A + IB ⋅ RF IA

ZA

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ABB AB, 2007

SOLUTION IS IN THE DISTANCE PROTECTION ALGORITHM

2007-10-03

Substation Automation and Protection Training

21

Resistive fault, double infeed – load export and import A

B

Import

Export ZL

No compensation

Um

Um

Z<

Z<

Dynamic X

Export

compensation

Import X

ZL

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ABB AB, 2007

R R 2007-10-03 22

Substation Automation and Protection Training

Export of load – compensation for ZM01

Automatic dynamic compensation: ZM01

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ABB AB, 2007

No compensation: ZM02, ZM03, …, ZM05

2007-10-03

Substation Automation and Protection Training

23

Remote faults and remote back-up „

Due to fault current contribution substation B (not ”seen” by relay in ”A), the distance protection in station A will measure a higher impedance than the "true" impedance to the fault.

„

The relay will underreach and this means in practice it can be diffcult to get a remote back-up. A

ZL UA

IA

B IB2

IB1

ZF

If=IA+IB1+IB2

Z<

VA = Z L ⋅ I A + (I A + I B1 + I B 2 ) ⋅ Z F

VA I +I +I = Z L + A B1 B 2 ⋅ Z F IA IA

SOLUTION IS IN LARGER SETTINGS and in the use of DIFFERENT SETTING GROUPS

ABB AB, 2007

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Zm =

2007-10-03 24

Substation Automation and Protection Training

Remote faults and remote back-up X

ZM04 Remote back-up

Remote fault I want to see

ZM03 Remote back-up

ZM02 LOAD

ZM01

R

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ABB AB, 2007

ZM05

2007-10-03

Substation Automation and Protection Training

25

Remote faults and remote back-up X

ZM04 Remote back-up

Remote fault I want to see BUT I CAN’T SEE BECAUSE I HAVE REDUCED THE RESISTIVE REACH!

ZM03 Remote back-up

ZM02 LOAD

ZM01

R

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ABB AB, 2007

ZM05

2007-10-03 26

Substation Automation and Protection Training

Remote faults and remote back-up X

ZM04 Remote back-up

Remote fault I want to see

ZM03 Remote back-up L

O CR EN D OA

A RE TA N E HM AC

ZM02 LOAD

ZM01

R

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ABB AB, 2007

ZM05

2007-10-03

Substation Automation and Protection Training

27

Additional applications Isolated or High Impedance Grounded Networks

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ABB AB, 2007

Series Compensated Lines

2007-10-03 28

Substation Automation and Protection Training

Isolated Networks First ground fault (A): Distance protections (Z