Review of Fault Location Methods for Distribution Power System

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Email: [email protected]. 2670. Review of Fault ... Key words: Fault location method, Distribution power system, System restoration. INTRODUCTION.
A us tralian Journal of Bas ic and A pplied Sciences , 3(3): 2670-2676, 2009 ISSN 1991-8178 © 2009, INSInet Publication

Review of Fault Location Methods for Distribution Power System M. Mirzaei, M.Z. A Ab Kadir, E. Moazami, H. Hizam Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia. Abs tract: For the pas t fifty y e a rs , electric power s ys tems have rapidly grown. This has res ulted in a large increas e of the number of lines in op e ra t io n a n d their total length. Thes e lines experience faults which are caus ed by s torms , lightning, s now, freezing rain, in s u la t io n breakdown and s hort circuits caus ed by birds and other external objects . In mos t cas es , electrical fault s manifes t in me chanical damage, which mus t be repaired before returning the line to s ervice. The res tora t io n c a n be expedited if the location of the fault is either known or can be es timated with reas ona ble accuracy. Speedy a n d precis e fault location plays an important role in accelerating s ys tem res toration, reducing outage time and s ignificantly improving s ys tem reliabilit y . T h is p aper provides a comprehens ive review of the conceptual as pects as well as recent algorithmic d e v e lo p me n t s for fault location on dis tribution s ys tem. Several fundamentally different approaches are dis cus s ed in the paper together with the factors affecting the as s umptions of the underlying concepts and the various criteria us ed in the different approaches are reviewed. Key words : Fault location method, Dis tribution power s ys tem, Sys tem res toration INTRODUCTION P ower quality requirements res ulting from the deregulated electrical markets have motivated t h e improvement of fault loc a tion methods in dis tribution s ys tems to s peed up the res toration proces s . Faults and outages affect power q uality in terms of s ervice continuity and dis turbance propagation. Utilities are forced to improve quality indexes as s ociated to thes e phenomena in order to be competitive in the current electric open market (M ora-Fl’orez et al., 2008). Faults in power distribution s ys tems caus e s upply interru p t io n s being res pons ible of proces s dis turbances , information and economic los s and equipment damage among others . Fault location includes the determination of the phys ical location of the fault. Nowadays , about 80% of interruptions are caus ed by fa u lts in dis tribution networks and the application of fault location algorithms developed for trans mis s ion s ys tem is not an eas y tas k due to the topology and operating principles of the firs t (i.e., nonhomogeneous feeders , load taps , laterals , radial operation and the available meas uring equipment) (Short, 2003; M ora-Flürez et al., 2009). The pres ence of laterals imp lie s that the dis tance obtained match to s everal fault locations in the power dis tribution s ys tem and caus es the multiple es timat io n p roblem. This caus e problem to the ma in t e n a n c e t e a m becaus e it is not eas y to determine the real fault location in a high s pread s ys tem, delaying the res toration of the power s ervice (M ora et al., 2006). To the aforementioned, s ome s trategies for fault location in d is tribution s ys tems have been developed. There exis t a variety of ap p ro a c h e s for locating faults in power dis tribution s ys tems . M os t of thes e methods es timate the relative dis tance to the fault from data acquis ition p ro v id e d by the protection devices . The performance of thos e techniques can be affected due to some particular characteris tics of the res pective s ys tem, s uch as unbalanced s ys tem, non-homogeneous conductors , s ys tems w it h h ig h ramification degree, etc (Ziolkows ki et al., 2007). This paper rev ie ws s elected fault location techniques propos ed for dis tribution s ys tems . In general, thes e methods can be clas s ified in three broad catego rie s , w h ich are Impedance and Other Fundamental Frequency Componen t Bas ed M ethods , High frequency components and travelling wave bas ed methods and knowledgebas ed method. Knowledge-bas ed method may be divided into three groups : A rtificial intelligence and s tatis tical analys is bas ed methods , Dis tributed device bas ed methods and Hybrid methods . Corresponding Author: M . M irzaei, Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra M alaysia, 43400 Serdang, Selangor, M alaysia. Email: [email protected] 2670

Aust. J. Basic & Appl. Sci., 3(3): 2670-2676, 2009 Distribution System Topology: The mos t important as pects cons idered by fault location methods are directly related to the characteris tics of dis tribution s ys tems : (a)Heterogeneity of feeders given by different s ize and length of cables , pres ence of overhead and underground lines , etc. (b)Unbalances due to the untrans pos ed lines and by the pres ence of s ingle, double and three phas e loads . (c)Pres ence of laterals along the main feeder. (d)Pres ence of load taps along the main feeder and laterals . Thes e as pects introduce errors in the e s t imation of the fault locations performed by means of a s implified model (M ora-Fl’orez et al., 2008). The us ual dis tribut io n lin e model (s hort lines ) is the lumped-parameter model, applying s ymmetrical components on phas or-bas ed algorithms (Zhu et al., 1997). T h e mos t common type of faults in dis tribution s ys tems are s hort circuits . Thes e fa u lt s in c lu ding s uch as s ingle line-to-ground, line-to line, double line-toground, three phas e and three phas e-to-ground faults with d iffe re n t values of fault res is tance between 0 and 50. Type of Fault Location M ethods: Res earchers have done cons iderable work in the area of fault dia g n o s is particular to radial dis tribution s ys tems . Traditional outage handling methods were bas ed on the cus tome r t ro uble calls . Here the geographic location of the caller and the connectivity of the dis tribution network ha ve to be overlapped exactly for the exact location of fault. A ls o, there might not be any calls during night-time, which pos es a p ro b lem for the operator in locating the fault. In recent years , s ome techniques have been dis cus s ed for the loc a t io n of faults partic u la rly in radial dis tribution s ys tems . Thes e methods us e various algorithmic approaches , where the fault location is it e ratively calculated by updating the fault current. A brief overview of the algorithmic approaches has been pres ented in the following s ection. Impedance and Other Fundamental Frequency Component Based M ethods: The dis t a n ce of fault from the primary dis tribution bus to the fault location is es timated by impedancebas ed method. Volt age and current values meas ured at one end or two ends of the line are required in this method. This method us ed mathemat ic a l e q uation to es timate the fault location. M os t of the method employs for radial s ys tem only a n d require other information s uch as circuit breaker s tatus , fault current waveforms , and fault indicator s tatus for non-radial s ys tem (Zhu et al., 1997; Senger et al., 2007). In thes e approaches , the firs t, the fault types and faulted phas es are identified. Next, the apparent impedance is calculated bas ed on the s elected voltage and s elect e d c u rrent. If Load currents at different taps are not cons idered s o they are s ources of error. Girgis (1993) pres ented equations to calcu la t e a ll kinds of fault s o c c u rrin g at the main feeder and a s ingle-phas e lateral. Loads were cons idered as cons tant impedance loads . It did not cons ider dynamic nature of the loads . Performance of the technique in s ituations where cables were us ed could als o be an is s ue. Sa h a e t a l .,(2007) propos ed method is devoted for es timating the location of fault s o n radial M V s ys tem, which could include many intermediate load taps . In this method nonhomogeneity of the feeder s ections was als o taken into account. A dis tribution utility M V networks were us ed as an example, but he s uppos ed the s ys tem was balanced. Santos o et al.,(2000) gave equations to calculate all kinds of faults occurring at the main feeder and a s ingle-phas e la t e ra l. H e u s ed a different method to take a c c o u n t of the fault res is tance. Das et al.,(2000) s ugges ted a technique that us ed the fundamental freque n c y voltages and currents meas ured at a line terminal before and during the fault. The fault location technique was des cribed by cons idering a s ingle-phas e-to-ground fault on a radial s ys tem. Nevertheles s , he s t ill cons idered the line were fully trans pos ed, and was only good for line-to-ground faults . Choi et al.,(2004) locating faults by s olving a qu a d ra t ic e q u a tion res ulting from the direct circuit analys is . It as s umed all load impedance was accurately known. Senger et al.,(2005) propos e d method that it was bas ed on meas u rements provided by intelligent electronics Devices (IEDs ) with built-in os cillography function, ins talled only at the s ubs tation level and on a databas e that s tores information about the net work topology and its electrical parameters . In particular on 11kV networks , applying this method is v e ry d iffic u lt, if not impos s ible, to establis h reliable s tatis tical es timates . Some of this method als o time cons uming due to iterative proces s and need to know the fault type before s pecific equation cou ld b e applied. Liao (2007) pres ented a fault location algorithm by utilizing s ynchronized or uns ynchronized pre-fault and fault voltage and c u rre n t meas urements from both ends of the line without requiring line parameters . this method applie d t o power line parameter es timation rely on s ynchronize d p h a s o r meas urements and require different s ys tem operating conditions from which to es timate the parameters .

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Aust. J. Basic & Appl. Sci., 3(3): 2670-2676, 2009 Generally, according to above mentio n e d s e ction, the main drawback of impedance-bas ed methods is the multi-es timation due to the exis te n c e o f multiple pos s ible faulty points at the s ame dis tance. Cons equently, thes e methods provide precis e but uncertain fault locations . High Frequency Components and Traveling W ave Based M ethods: The v ie w of this method was bas ed on the reflection and trans mis s ion of the fault generated travelling waves on th e faulted power network. A lthough in this technique fault can be located with a high accuracy, the implementation is complex and more expens ive than the implementation of impedance bas ed techniques . Becaus e it needs too many added equipment, s uch as the GPS s ys tem, fault trans ient detectors and diagnos tic s oftware. Furthermore, due to the complex configurations of dis tribution s ys tems , the configuration or the s ites to ins tall the fault trans ient detectors become very d iffic ult. Thomas et al.,(2003) us ed the cros s -correlation function between the incident wave and the reflected wave to locate faults in dis t rib u t io n s y s t e ms . He us ed both the double-ended meth o d a n d t h e s ingle-ended method. The double-ended method could provide an accurate res ult if the fault happened at the line where the fault recorders were ins talled, o r a t the main feeder. The s ingle-ended meth o d did not work well. One of the negative as pects of thes e methods is the neces s ity of meas uring devices with a very high s ampling rate (M Hz) and the author did not pres ent any idea to overcome the problem caus ed by multiple dis continuities in dis tribution s ys tems . Bo et al.,(1999) pres ented another method to locate faults . For dis tin g u is h ing the reflected wave from the fault point and that from the remote bus bar, a new fault locator unit was developed, whic h c a p t u red high frequ e n c y voltage s ignals between 1 and 10 M Hz. In this method the effects of tapped-off loads are found s ig n ificant, and caus ed problems in identifying the fault location. He did not s olve the problem completely. Tang et al.,(2000) s ugges ted a technique b a s e d o n the voltage magnitude difference between the device’s terminal voltages . This method n e e d e d t o in s ert s ome equipment into to dis tribution feeders . It could not be done only us ing the terminal meas urements . M agnago et al.,(1999) offered method bas ed on the high frequency s ignals meas ured at the s ubs tation. Bas ed on the us e of t h e wavelet trans form, us ually adopting the dis cretew a v e let trans form (DW T), due to its s traightforward implementation and the reduced computational t ime it re q u ire s c o rrelation analys is between trans mited and reflected waveform is performed. To us e this method, s imulation need to be done performed for each dis tribution s ys tem s o that us ers know the wavelet coefficients of different fault laterals , and can identify the faulted lateral bas ed on thes e coefficients . Utilities cannot afford to implement a s olution on a dis trib u t io n feeder if there has to be s ignificant configuration and modelling of each s pecific fe e d e r. It never would be able to keep it up-to-date, even if a utility could enter feeder-s pecific topology information during initial s etup. Borgheti et al.,(2006) propos ed me t hod bas ed on the continuous -wavelet trans form (CW T) for the analys is of voltage trans ients d u e t o lin e faults . Correlation exis ts between typical frequencies of the CW T-trans formed s ignals and s pecific paths in the netwo rk c o v e re d by the travelling waves originated by the fault. Shown uncertainty levels lower than 200 Hz on the es timate of the frequency as s ociated to the paths covered by the travelling waves . This value provides an indication of the uncertainty of the es timated fault location. The s ys tem that implemented was balanced and A ccuracy of this approach is low too. A ccording to aforementioned s e c tion, in general, the mos t important drawback of thes e methods is the neces s ity of meas uring devices with a very high s ampling rate (M Hz) Knowledge-Based M ethod: The third category is knowledge-bas ed method. This method can be divided into three groups : A . A rtificial intelligence and s tatis tical analys is bas ed methods B. Dis tributed device bas ed methods C. Hybrid methods A. Artificial Inteligence (AI) and Statistical Analysis Based M ethods: There a re s e veral artificial intelligent methods s uch as A rtificial Neural network (A NN), Fuzzy Logic (FL), Expert Sys tem (ES) and Genetic A lgorithm (GA ), etc., with the development of computers emerged. Thes e methods can help operators or engineers to do mu c h laborious work. By us ing thes e methods , the time factor is s ubs tantially reduced and human mis takes are avoided. Therefore, many res earchers us ed A I bas ed methods in dis tribution s ys tem fault locations . A multi-w a y g ra p h p a rtitioning method is employed by Bi et al.,(2002a;2002b) bas ed on weighted minimum degree reordering to partition a large -s c a le p o wer network into s ome s ub-networks . The s peed of the dis tributed fault section es timation s ys tem ma d e it pos s ible to us e it as an on-line s ys tem. A l-Shaher et al., (2003) developed a fault location method for multi-ring dis tribution s ys tems

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Aust. J. Basic & Appl. Sci., 3(3): 2670-2676, 2009 us ing neura l n etwork. He us ed the feeder fault voltage, circuit breaker s tatus , real power of feeders during the normal condition, and real pow e r o f fe e d e rs during s hort circuit, etc, to train the neural network. W en (1997) propos ed a method that cons tructed a probab ilis t ic caus ality matrix to repres ent the probabilis tic relations hip between faulted s ections and protective device action. He applied the pars imonious s et covering theory to make the faulted s ection es timation as an integer-programming problem. Finally, a refine d g e n e tic algorithm (RGA ) was adopted to s olve the problem, Bas ed on the “natural s election, b e s t s urvival” theory, the RGA found the mos t reas onable hypothes is or hypothes es bas ed on the evaluation res ult o f e a ch hypothes is evaluated by s et covering theory. Thukaram et al.,(2002) offered method es timated the voltage magnitude and p h a s e angle at all load bus es through s tate es timation. A thres hold was us ed to detect the fault path. Chen et al.,(2002) us ed a caus e-effect network to repres ent caus ality between faults and the actions of protective devices . The caus e-effe c t n e t w ork’s features of high-s peed inference and eas e of implementation made it feas ible to implement an on-line fault s ectio n e s t imation s ys tem. Bas ed on the actions of protective devices , the network could quickly find faulted s ection candidates . M ora e t a l .,(2009) p re s ented an alternative s olution to the problem of power s ervice continuity as s ociated to fault location. A methodology o f s t a t is tical nature bas ed on finite mixtures is propos ed. A s tatis tical model was obtained from the extraction of the magnitude of the v o lt a g e s a g regis tered during a fault event, along with the network parameters and topology. The approach is bas ed in the statis tical modelling and extraction of the s ag magnitude from voltage meas urements s tored in fault data bas es . The determination of groups of well-defined c h a ra c t e ris tics which was allows an optimization in the clas s ification of data thus ens uring good mo d e l accuracy. A s ignificant feature is the low inves tment cos t for the implementation o f the fault detection s ys tem bas ed in the propos ed method. M artinas et al.,(2003) propos ed an approach us ed the Eigenvalue and an artificial neural network bas ed learning algorithm. The neural n e twork was trained to map the non-linear relations hip exis ting between fault location and characteris tic Eigenvalu e . T h is approach us ed the eigenvalue/eigenvector and an artificial neural bas ed learning algorithm. The main characteris tics and particularit ie s o f t h e propos ed method were: Reduced number of input s ignals (this was an importance as pect due to the non-us e of v oltage detectors ); Recognition of the faults type and identification of faulty line or lines ; Loca t io n o f t h e fault, independent of his pres ence at th e moment of the analys is ; almos t independent on harmonics influence. Simulation res ults pres ented s how that the propos ed algorithm was a promis ing technique for fault location on dis tribution power s ys tems . He a ls o p ropos ed a method for locating faults for parallel double-circuit dis tribution lines (Sous a et al., 2005). It bas ed on impedance calculations or on travelling-wave analys is . The Clarke-Concordia trans formation was us ed to trans form line currents into current components . Bas ed on thes e components , a dat a s a mp le correlation matrix was cons tructed. The eigenvalues of the correlation matrix h a d a n o n -linear relations hip with the fault dis tance. A neural network was us ed to extract the unknown relations hip. B. Distributed Device Based M ethods: A nother type of knowledge-bas ed technique is dis tributed device bas ed methods for locating fault. W ang et al.,(2000) pres ented a mathematical approach that located faults bas ed on in s t a lled voltage s ens ors ’ information and the network’s topological s tructure. The relation of the v o lt a g e s ens ors with s ections was formulated as a matrix. The other matrix was cons tructed bas ed on the topological re la t io n b e t w een s ections and nodes in an electric network. Through s ome matrix operations , all faulted s ections could be found. M okhlis (2007) offere d t h e me t hod that it worked by matching the actual voltage magnitude and phas e angle with the s imulated ones from fault analys is that s tored in a databas e. The method was s imple and inexpens ive for implementation s ince its only requires s ingle meas urement at the monitored bus . A ny changes s uch as load variations or network reconfiguration could be adapted by this method by updating the databas e. But it could n o t imp ro ve well to cons ider the effect of fault res is tance. Kezunovic, (2001) propos ed another ty p e o f knowledge-bas ed technique is by matching meas ured data with his torical fault data. W h enever fault occurs in the dis tribution network, the waveform of voltage s ags meas ured at the s ubs tation is recorded into the databas e together with the known fault type and location. This databas e is updated whenever fault occurs in the s ys tem. W hen actual fault occurs , the meas ured voltage s ags wave fo rms a t the s ubs tation are compared to all the voltage s ags waveforms in the databas e. The mos t matching wavefo rm in t h e d a t a bas e will give the type of fault and the location. T h e d ra w b a c k o f this method is that it will not work if the actual fault never happens at particular location, or not recorded in the databas e. C. Hybrid M ethods: A lmos t all of the a b ove methods locate faults bas ed on one algorithm, s uch as the fault dis tance

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Aust. J. Basic & Appl. Sci., 3(3): 2670-2676, 2009 calculation or operated protective device’s s tatus analys is , to locate faults . Some have inves tigated the us e of hybrid methods that locate faults ba s e d o n more than one algorithm to achieve a more accurate es timation of the faulted s ection. Zhu et al.,(1997) propos ed a hybrid metho d t h a t c o mp uted the fault dis tance us ing meas urements available at the s ubs tation. He us ed pos t-fault values of current or voltage to reduce the multiple es timation problems induced by the exis tence of multiple fault points in the ne t work with the s ame impedance. To identify the actual fault location, a fault diagnos is procedure was applied to rank the lis t of mu lt ip le potential fault locations . By doing a circuit s imulation, the operation of a particular combination of p ro t e c t ive devices and the load ch a n g e p atern during different fault s cenarios could be obtained. Then by matching the fault s ituation to thes e s cenarios , the a c t u a l fa u lted s ection could be determined. However, this diagnos is procedure modelled the circuit and s imulated differe n t fa u lt s cenarios , which were time-cons uming tas ks , and the modelling proces s needed to be done again for another s ys tem. Järventaus ta et al.,(1994) us ed the fault dis tance calculation, fault detector information, and geographical information of the dis tribution s ys tem to locate faults . Zhong et al.,(1996) pres ented a method to locate faults bas ed on fault current meas urements , fault currents calculated from s hort circuit analys is , and s ys tem operators ’ experience. Lee et al.,(2004) calculated the fault dis tance firs t to provide s ome fault location candidates . Then, by current patern matching and interrupted load analys is , the candidate pool was reduced. Khos ravi (2007) developed a frame w ork for fault detection and modelling when uncertainty in the plant was pres ent. In the propos ed method, a fa u lt alarm was fired when an incons is tency between the behaviours of the s ys tem and the model emerges . A fterwards , the beha v io ur of the faulty s ys tem is modelled us ing an A daptive Neuro Fuzzy Inference Sys tem (A NFIS). The identified model can be us ed for the fault accommodation tas k. M ora et al.,(2006) propos ed a fault location approach bas ed on t h e current waveforms meas ured at the power s ubs tation and the knowledge of protective device s eting and A NFIS nets . The A NFIS nets proved the capability to locate the fault in a s pecific zone of power dis tribution s ys tem and s howed validation errors lower than 1% to locate faulted zones . This approach did not us e the ele c t ric al model of the network and the s ignal treatment to obtain des criptors is s imple. The fact of not us ing the ele c t ric al network model was an additional advantage becaus e it was not always eas y t o h a v e t h e electrical power s ys tem parameter values . Fuzzy inference is us ed in b o t h me t h o d s (Khos ravi, 2007; Mora et al., 2006) to deal with uncertainty inherent in thes e methods . Fan (Chunju et al., 2007) propos ed a fa u lt location method employing wavelet fuzzy neural network to us e pos t-fault trans ient and s teady-s tate me a s u rements . However, this method was not influenced by the fault res is tance and load current but he as s umed the s ys t e m w a s b a la n ced and it tacked a lot of time in off line mode the training and calculation for the fault location in indus trial dis tribution lines . Conclusions: This paper has pres ented an overview of fault location on dis tribution power s ys te m a n d s u mmaris ed various locating fault s trategies . Fault locating s trategies us ing impedance bas ed methods , travelling wave bas ed methods and knowledge-bas ed methods have been reviewed. M os t of the fault loca t ion techniques dis cus s ed have s ome limitations . Some of them are as follows : a) The it e ra tive fault location algorithm are generally time cons uming and always has the cons tant ris k of running into a diverging s olution. b) Heuris tic procedure may take large number o f trials and als o time in practical dis tribution s ys tems before identifying the fault location and res toring the power s upply to healthy part of s ys tem. c) A lmos t it requires voltage and current meas urements from all the nodes and branches in order to detect the fault location. A ccording to the advantages and dis advantages des cribed for each metho d we can conclude that in comparis on between all methods , knowledge bas ed method s eemed to have more accuracy and s peed and les s cos t. A mong the different knowledge bas ed algorithms , artificial intelligence method s uch as A NN algorithm are more us ed with accordance to the s ucces s progres s in A I in recent years . REFERENCES A l-Shaher, M ., M .M . Sabra and A .S. Saleh, 2003. Fault Location In M u lt i-Ring Dis tribution Network Us ing A rtificial Neural Network,” Electric Power Sys tems Res earch, 64(2): 87-92. Bi, T., Y. Ni, C.M . Shen and F.F. W u. 2002. Efficient M ultiway Graph Partitioning M eth o d F o r Fault Section Es timation In Large-Scale Power Networks . IEE Proc. Gen. Trans . and Dis t., 149(3): 289-294. 2674

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