traveling wave differential relaying presented by jinqian yu

Traveling Wave Differential Relaying

Presented by Jinqian Yu

Table of Contents

1. Introduction

2. Line model for traveling waves

3. Traveling waves’ propagation & measurement

4. Differential algorithm based on traveling waves

5. Feasibility of implementation

Introduction

Basic idea The occurrence of a fault can trigger a series of traveling

waves which contain the earliest available evidence to a relay that the fault has taken place. It is possible to design a differential relay scheme based on traveling waves.

Advantages • Ultra-high speed • Less susceptible by system transient phenomenon

Line model for traveling waves

Distributed parameter model

→

Solution

u iri lx ti ugu cx t

u ilx ti ucx t

(lossless line)

( ) ( )

1 [ ( ) ( )]

x xu F t f tv vx xi F t f t

z v v

Where v is surge velocity

z is surge impedance

1vlc

lzc

l

c

l

c

ui

Traveling waves propagation & measurement

2 1

2 1

f s r

r r f

e k e

e k e

k is reflection coefficients, such that

Fer ef

ir if

er1

ef2

er3

ef4

ef1

er2

ef3

x

t

T

3T

5T

S R

The reflection coefficient at fault location is -1

Measurement

Sending end

→

Receiving end

→

( ) ( )

1( ) [ ( ) ( )]

s

s

u t F vt f vt

i t F vt f vtz

2 ( ) ( ) ( )2 ( ) ( ) ( )

s s

s s

F vt u t zi tf vt u t zi t

( ) ( ) ( )1( ) [ ( ) ( )]

r

r

u t F d vt f d vt

i t F d vt f d vtz

2 ( ) ( ) ( )2 ( ) ( ) ( )

r r

r r

F d vt u t zi tf d vt u t zi t

F and f denote forward wave and backward wave respectively

Differential algorithm based on traveling waves

S RFs

fs

fr

Frus(t) ur(t)

( ) ( ) ( )( ) ( ) ( )( ) ( ) ( )( ) ( ) ( )

s s s

r r r

sr s s

rs r r

u t F t f tu t F t f tzi t F t f tzi t F t f t

→( ) ( ) 2 ( )( ) ( ) 2 ( )( ) ( ) 2 ( )( ) ( ) 2 ( )

s sr s

r rs r

s sr s

r rs r

u t zi t F tu t zi t F tu t zi t f tu t zi t f t

Derive the Bergeron’s equations

In a healthy line, it takes time T= d/v that a forward wave from terminal S travel to terminal R where the wave is regarded as backward wave.

Use these equations and take t = t – T in equations in last slide, we get the Bergeron’s equation:

( ) ( )( ) ( )

r s

s r

f t F t Tf t F t T

( ) ( ) ( ) ( )( ) ( ) ( ) ( )

s sr r rs

r rs s sr

u t zi t u t T zi t Tu t zi t u t T zi t T

Feasibility issuesThough Bergeron’s equations always hold if there is no internal fault

between two terminals of a line and this differential relaying scheme seems foolproof, some problems still remain unsolved.

1. The relay has to rely on a narrow window of available data to make a decision.

2. It is difficult to recognize and capture the data carried by wavefront as it travels at such a high speed.

3. Data acquisition system must be high bandwidth to obtain the high-frequency content of traveling waves.

Conclusion

• Differential relaying based only traveling waves is just one of those relatively new scheme using traveling waves. In theory, it has demonstrated the possibility of ultra-high speed for a relay. However, some technical issues need to be solved before implementation. Traveling wave differential relaying is still an interesting technique and worth our attention.

Reference[1] Tagaki, T., Baba, J.I., Uemura, K. and Sakaguchi, T. Fault protection based on

traveling wave theory, Part 1–Theory. Electrical Engineering in Japan, Vol. 98, No. 1, 1978.

[2] Tagaki, T., Baba, J.I., Uemura, K. and Sakaguchi, T. Fault protection based on traveling wave theory, Part 2–Sensitivity analysis and laboratory test, IEEE paper No. A 78, pp. 220-226, 1978.

[3] Dommel, H.W. and Michels, J.M., High speed relaying using traveling waves transient analysis, IEEE paper No. A78, pp 214-219, 1978.

[4] Bewley, L.V., Traveling Waves on Transmission Systems, John Wiley & Sons, Inc. New York, 1963.

[5] Chamia, M. and Liberman, S. Ultra high speed relay for EHV/UHV transmission lines – development, design and application, IEEE Trans, on PAS, vol. PAS-97, No. 6, pp. 2104-2116, 1978.

[6] Mansour, M.M and Swift, G.W., A multi-microprocessor based traveling wave relay – Theory and realization, IEEE Trans. Vol. PWRD-1, No. 1, 1986.

[7] Bollen, M.H.J. and Kerston, W.F.J., Traveling-wave-based protection: directional, differential or distance? Proc 10th Power Systems Computation Conf., 1990.

[8] Bollen, M.H.J. Traveling-wave-based protection of double-circuit lines. IEE Proceedings-C, Vol. 140, No. 1, 1993.

[9] Arun G. Phadke, James S. Thorp. Computer relaying for power systems, John Wiley & Sons, Inc, New York, pp 254-280, 2009.

[10] Zecun Zhou. High voltage technology, China electric power press, pp. 141-166. 2003.

Thank you!

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