498 IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 1, FEBRUARY 2007

Transmission Line Fault Location Using Two-TerminalData Without Time Synchronization

Eduardo G. Silveira and Clever Pereira

Abstract—This letter presents a new transmission line fault lo-cation method that uses current and voltage sinusoidal phasors atboth ends, without necessity of data synchronization. The main dif-ference among the classical Johns method resides in the fact thatthe proposed method is based on magnitude of fault point voltageand does not demand exact phase angles of the acquired signals.Simulated and real case results are presented, showing that the pro-posed algorithm is robust, accurate, and provides adequate perfor-mance. Practical applications confirm that the synchronization isnot really necessary, making the method faster and easier to applythan classical methods in many real situations.

Index Terms—Digital protection, extra high voltage (EHV)transmission line, fault location.

I. INTRODUCTION

TRANSMISSION line fault locators have one main objec-tive: to estimate the distance between the fault point and

one of the terminals of a monitored transmission line. To do thisjob, they have routines that process input data, since they areacquired by digital recorders at substations, until their applica-tion in the fault location-specific algorithm [1]. Many factorscan contribute to reduce the precision of the results like errorsin CTs and CVTs, in transmission line parameter values andin steady-state voltage and current phasor estimation [2], [3].Classical algorithms that use quantities of both sides of trans-mission line usually lead to more accurate results, but they needtime synchronization by GPS systems or computational routines[3], [4]. This letter brings up a new method of transmission linefault location, using data from both terminals of transmissionline, without time synchronization [2]. Application of the pro-posed method leads to robustness and accuracy of the results,mainly in case of failures in data synchronization procedures.Additional gains like smaller maintenance costs and transmis-sion line out-of-step times increase the overall reliability of theelectric power system.

II. DESCRIPTION OF THE METHOD

The new method is based on voltage magnitude profiles alongthe monitored transmission line, calculated from both local andremote terminals. At fault point, the voltage magnitude is thesame, independent of its phase angle, and so, independent oftime synchronization of the input data. Fig. 1 shows the locationof a fault occurred at 40 km from local terminal of a 400-km,345-kV transmission line, corresponding to the intersection of

Manuscript received March 28, 2006; revised July 19, 2006. This work wassupported by CEMIG. Paper no. PESL-00020-2006.

The authors are with Electrical Engineering Department, Federal Universityof Minas Gerais, Belo Horizonte, Brazil (e-mail: gonzaga@cpdee.ufmg.br).

Digital Object Identifier 10.1109/TPWRS.2006.887952

Fig. 1. Voltage magnitude profiles showing the intersection fault point.

Fig. 2. Faulted transmission line.

the voltage magnitude profiles, calculated from both local (VS)and remote (VR) terminals.

This letter presents two algorithms based on voltage magni-tude profiles. The first uses the short line model, with a simplesolution and less computational effort. The second, which ismore complex, takes into account hyperbolic functions, relatedto the long transmission line model.

A. Algorithm 1—Short Transmission Line Model

Fig. 2 shows the positive sequence diagram of a faulted trans-mission line of length , represented by its short line model.

Voltage magnitude at point F obtained from quantities of ter-minal or are equal, so

(1)

Replacing and in (1) and developingthe expression results in the following equation:

(2)

where

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IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 1, FEBRUARY 2007 499

Fig. 3. Location errors with simulated data.

Second degree (2) has two roots, one positive and inside thetransmission line. This root is the desired fault point.

B. Algorithm 2—Long Transmission Line Model

Considering again the circuit of Fig. 2 and the long transmis-sion line model, the voltage along the transmission line, calcu-lated from both terminals and , respectively, are

(3)

where and are, respectively, the characteristic impedanceand propagation constant of the monitored transmission line.The fault location is obtained by determining the value of ,which leads (4) to a minimum

(4)

Equations (3) and (4) contain the desired fault point ,positive sequence superimposed voltage and current estimatedphasors, and transmission line constants and . Since thesolution is determined from voltage magnitudes, the locationprocess can be done without time synchronization of localand remote digital recorder signals, which can occur duringsituations where the GPS synchronization signal gets lost.

III. RESULTS

In order to test the proposed method, phase-ground faults,with substantial value of fault resistance of 100 ohms, at dif-ferent points of a 138-kV, 200-km transmission line were sim-ulated, using the software PSCAD—Power Systems ComputerAided Design. A second classical method [3], which requirestime synchronization, was also used, in order to compare theobtained results. The results presented in Fig. 3 were obtainedconsidering a deliberate error of 20 in the phase of the inputdata acquired from remote terminal.

This figure shows that the proposed method presented lowererrors, generally less than 1.5%, despite the 20 phase angle

TABLE IREAL FAULT LOCATION WITH NONSYNCHRONIZED DATA

error. It also shows that the long line model algorithm presentedbetter performance than the short line model algorithm and thatthe method that requires time synchronization presented theworst results.

Table I presents some results of real short-circuit cases, fromdigital event recorders installed at CEMIG (Energetic Companyof Minas Gerais—Brazil) transmission lines, where the pro-posed method has been used to locate transmission line faults,when recorded data are not synchronized. The proposed methodhad an adequate performance in all studied cases.

IV. CONCLUSIONS

This letter shows that it is possible to execute transmissionline fault location using two-terminal data without equipmentsor routines for time synchronization purposes. The proposedmethod had good performance both in simulated and in realshort-circuit cases, even when fault resistance assumed highvalues. Additional tests verified a little increase in fault locationerrors of 0.3% when the method was applied to a double-circuittransmission line, but the errors remain satisfactory for practicalapplications. The method can be implemented both for shorttransmission lines, with reduced computational effort, and forlong lines, with more complex algorithm and better results. Dueto its simplicity, the method could even be used as part of areal-time transmission line digital protection scheme.

ACKNOWLEDGMENT

The authors would like to thank CEMIG for the real short-circuit data presented in this letter.

REFERENCES

[1] IEEE Guide Determining Fault Location on AC Transmission and Dis-tribution Lines, IEEE Std. C57.19.100, Jun. 2005.

[2] D. Novosel, D. G. Hart, and E. Udren, “Unsynchronized two terminalfault location estimation,” IEEE Trans. Power Del., vol. 11, no. 4, pp.130–138, Oct. 1996.

[3] A. T. Johns and S. Jamali, “Accurate fault location technique for powertransmission line,” Proc. Inst. Elect. Eng., Gen., Transm., Distrib., vol.137, no. 6, pp. 395–402, Nov. 1990.

[4] E. O. Schweitzer, III, “Evaluation and development of transmissionline fault-locating techniques which use sinusoidal steady-state infor-mation,” in Proc. 9th Annu. Western Protective Relay Conf., Spokane,WA, Oct. 1982.