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!

Q&A