MODIFIED SWARM FIREFLY ALGORITHM METHOD FOR DIRECTIONAL OVERCURRENT RELAY COORDINATION PROBLEM

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1 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: MODIFIED SWARM FIREFLY ALGORITHM METHOD FOR DIRECTIONAL OVERCURRENT RELAY COORDINATION PROBLEM M.H. HUSSAIN, I. MUSIRIN, 3 A.F. ABIDIN, 4 S.R.A. RAHIM,,4 School of Electrcal System Engneerng, Unverst Malaysa Perls,3 Faculty of Electrcal Engneerng, Unverst Teknolog MARA E-mal: muhdhatta@unmap.edu.my, smalbm@salam.utm.edu.my ABSTRACT Computatonal ntellgence method such as Nature Inspred Algorthms (NIA) or meta-heurstc algorthms based optmzaton methods known to be successful n coordnaton of drectonal overcurrent relay. It has also been reported that t outperformed the conventonal approach. Due to ts advantages, t has ganed more popularty among the researchers. Some of the conventonal optmzaton technques such as lnear programmng method and non-lnear programmng method were proposed but these methods s tme consumng and complex to acheve optmal soluton. Thus, a search for better optmzaton technque to reduce computaton burden has become urgency. Ths paper presents the mplementaton of Modfed Swarm Frefly Algorthm (MSFA) n solvng drectonal overcurrent relay coordnaton problem. The effect of populaton szes were consdered to nvestgate the performance of MSFA technque. The coordnaton of drectonal overcurrent relays s formulated as lnear programmng problem and the objectve functon s ntroduced to mnmze the operatng tme of the prmary relay. Operatng tme of the relay depends on tme settng multpler (TSM) whch leads to no mscoordnaton between relay pars. The proposed method have been appled and tested successfully on 8-Bus test system and 9-Bus test system. The results revealed that MSFA outperformed Partcle Swarm Optmzaton (PSO) n terms of computaton tme. Keywords: Drectonal Overcurrent Relay (DOCR) Coordnaton, Modfed Swarm Frefly Algorthm (MSFA), Partcle Swarm Optmzaton (PSO), Tme Settng Multpler, Computaton Tme. INTRODUCTION Undesrable condtons such as faults, overvoltage, overcurrent, over frequency and under frequency condtons can occur frequently and leads to damagng equpment, nterruptng power supply connected to the power system. When these stuatons occurred, the faulted components should be ready to solated and mantan system stablty. Ths s known as power system protecton. Protecton power system normally comprses of fve components. There are current transformers, voltage transformers, protectve relays, crcut breakers, batteres and fuses n a dstrbuton system. By takng consderaton of ths undesrable condton, a relable protectve power system s requred. The protectve relay plays the most sgnfcant part n power system protecton whch senses the undesrable condtons wth the ad of current transformers and crcut breaker. For protecton system, Current Transformer (CT) usually desgned to reproduce the largest current fault whle the relay carres out the nformaton provded by the CT n accordance wth some predetermne logc and compares t wth relay settngs to take a trp or notrp decson []. If fault happens, the relay ntates the operaton of the Crcut Breaker (CB) by ssues trppng sgnals to open the CB. Ths s to ensure the defected element wll be solate from the rest of the system. Nowadays, transmsson system and dstrbuton system are very complcated. Due to ths, a large number of protectve relays are requred to cooperate wth each other to ensure relable and secure operaton of a whole system. Protecton system s organzed accordngly whch can be dvded nto several zone. Each of the zones may be mplemented usng dfferent relayng prncple []-[]. In typcal power system, there are many zones to be protected such as generator zone, bus zone, transformer zone, transmsson lne zone, etc. Ths system s called as man protecton system. In order for the relable protectve relay to act accordngly f the man protecton system faled, the 74

2 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: backup protecton system should operate to ensure relablty. Tme gradng margn or commonly known as tme delay s the crtera to be consdered for coordnaton when prmary relays and backup relays coordnated together. It means that the operatng tme of backup relay must be delay by an approprate tme over that of the prmary relay. When fault started to strke, both prmary relay and backup relay start operatng smultaneously. In case the man protecton system operates successfully, the backup protecton system resets wthout ssung a trp command. If man protecton system fals to operate, the backup protecton system wats untl the man protecton cleared the fault and then ssues the trp command to ts crcut breakers. Accordng to [3]-[4], protectve relays comprses of fve types whch are overcurrent relays, drectonal relays, dfferental relays, dstance relays and plot relays. The most common relay used n power system s the overcurrent relay. Ths relay has two settngs whch are plug settng and tme settng. The functon of plug settng s to determne the current requred for the relay to pck up whle tme settng s to decde the operatng tme of the relay [], [3]- [4]. The overcurrent relay normally used for overcurrent protecton and must de-energzed the undesrable condtons as quckly as possble to protect the system. Bascally, overcurrent relays have Current Settng Multpler (CSM) startng from 50% untl 00% n steps of 5% [4]. Ths s commonly known as Plug Settng (PS) whch the value s determned by maxmum load current and mnmum fault current. Several methods have been proposed and appled by the researchers for the last four decades. These methods can be categorzed nto tral and error, curve fttng, graph theoretcal and optmzaton method []-[6]. In classcal approach, fault analyss s conducted, after that rng network are break nto radal type, relay whch at far-end s set frst and then backup relays are set. Ths process s repeated contnuously untl all the relays are taken nto consderaton. Due to the complexty of the power system, both tral and error approach, graph theoretcal technque and topologcal technque s tme consumng []-[3]. The optmzaton technques outperformed the classcal approach whch one of ts advantages s fast convergence rate to acheve a sutable relay settng and elmnate a breakpont technque. Urdaneta et. al n 988 [7] dd state that the proposed new methodology based optmzaton theory determnes the optmal soluton to the coordnaton problem n effcent way. Indeed, optmzaton technques are more effcent for the network wth multsource and mult looped system. In the last ffteen years, computatonal ntellgence methods such as Evolutonary Computaton (EC) are appled to solve overcurrent relays coordnaton problem. In [8]-[9], C.W. Soo et al. proposed Genetc Algorthm (GA) and Evolutonary Programmng (EP). GA was mplemented to overcome non-lnear programmng problem and EP produces two problems whch are mscoordnaton occurred between prmary/backup relays and dscrete TSM relays changed to contnuous. Thus, to overcome ths problems, Razav et al. n 008 [0] ntroduced a new comprehensve GA to solve two man problems occurred by C.W. Soo et al. Although GA was mplemented n ths paper but for bnary-coded GA, t needs to change to bnary encodng, requred longer tme to converge and sometmes struck to local mnmum soluton []. Other category s Swarm Intellgence Algorthms whch has becomng the most popular nature nspred optmzaton technques used to solve engneerng problems. In [], algorthms based on nature have been sad effectve and effcent n order to solve dffcult optmzaton problems. Modfed Partcle Swarm Optmzaton (MPSO) was proposed by H.H. Zeneldn et al. n 006 [3] to compare wth Partcle Swarm Optmzaton (PSO). M.M. Mohamed et al. and M.H. Hussan et al. also were proposed the same method n [4]- [5]. Accordng to [6], PSO have two major drawbacks whch are suffers from premature convergence when problems wth multple optma are beng optmzed. The second drawback s the performance of PSO s very senstve to parameter settngs. Artfcal Bees Colony was also reported n [7]-[8] and sometmes good at exploraton (global search) but poor explotaton (local search) where t suffers to look for better soluton. In [9], Honey Bee Algorthm (HBA) was proposed by V. Ratsch et al. but t has several parameters need to be tuned properly. Lately, Frefly Algorthm (FA) have been wdely used n structural optmzaton and numercal optmzaton problems [0]-[]. Although FA to seems to be better n speed of convergence but FA has some of dsadvantage such as gettng trapped nto several local optma []. In [3], H. Zhang et al. stressed that Nature Inspred Algorthm (NIA) can be hybrdzed together wth other algorthms to enhance tself to be more effcent, faster, robust and can reach global optma. 74

3 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Ths paper presents Modfed Swarm Frefly Algorthm (MSFA) method n solvng Drectonal Overcurrent Relay Coordnaton problem. The study dscovered that the new algorthm known as MSFA whch ntegrates both PSO and a part of Frefly Algorthm (FA) can mprove the performance of PSO. In order to verfy ts performance, MSFA s appled to mnmze relay operatng tme accordngly wth an optmal TSM and wth a gven pckup current settngs. The results from the study revealed that the proposed technque outperformed the PSO technque n terms of computaton tme.. PROBLEM FORMULATION Drectonal overcurrent relay coordnaton problem can be stated as a constrant optmzaton problem. Drectonal overcurrent relay coordnaton settng becomes more dffcult when there are many overcurrent relays to be coordnated n a system. Ths s where optmzaton method s requred to search an optmal settng for the overcurrent relays. A. Mahar and H. Seyed n [4] stated that n lnear model programmng problem, only TDS or TSM are optmzed whle I ps are fxed at values between mnmum fault current and maxmum load current. In non-lnear programmng problem, TDS or TSM and Ips are optmzed smultaneously. Therefore, the man objectve of the drectonal overcurrent relay coordnaton n ths paper s to fnd optmal TSM or TDS, objectve functon, relay characterstc, prmary/backup relay pars constrants, coordnaton constrants, type of relay that had been consdered, boundary lmts of the relays and dscrete or contnuous TSM or TDS relays. All of these requrements should be satsfed. In [4], M.M. Mohamed et al. dd mentoned that drectonal overcurrent relay coordnaton allow for contnuous TSM or TDS but dscrete pckup current settng.. Objectve Functon Accordng to F. Razav et al. n [0], the GA method cannot solve two major problems whch are mscoordnaton problem between prmary and backup relay pars and dscrete or contnuous TSM of the relays. Thus, a new objectve functon and a new comprehensve GA are ntroduced to rectfy the problems. In order to solve heurstc optmzaton problem, a penalty method s used. Ths penalty method s ntroduced by addng penalty constrants such as t of prmary and backup relay pars to the orgnal objectve functon. The penalty method s set carefully wth hgh of order, 0 5. The objectve functon used n ths paper s gven below [0, 5]: N P OF = mn α + t α ( t pb β( t pb tpb )) = j= t where t pb N P α α β the th relay operatng tme for a fault near to the Crcut Breaker (CB) of the th relay the operaton tme dfference for relay pars the number of relays the number of prmary/backup relay pars represents each relay and vares to N N control the weght of t control the weght of ( t the parameter to consder mscoordnaton () In ths study, the value of β s determned by usng the heurstc technque. The convenence value of β s ft to the equaton whch mscoordnaton can be avoded. It should be noted that the objectve of the drectonal overcurrent relay coordnaton problem s to mnmze the summaton operatng tmes of prmary relays, mnmze the objectve functon and to avod mscoordnaton problems occur between prmary/backup relays.. Relay Characterstc In ths paper, the followng equaton () s used to approxmately represent the nverse overcurrent relay characterstcs and t s called the Sachdev model. It s assumed that all overcurrent relays have normally nverse overcurrent type and more commonly formulated by the followng equaton accordng to relay characterstcs whch are lnearly proportonal to TSM or TDS [0, 5, 5, 6]. a a a a M ( M ) ( M ) ( M ) t = a () 3 4 TSM where M or Plug Settng Multpler (PSM) s the rato of relay short crcut current to the actual pckup current I sc M =. I pckup = P j= pb β ( t pb t pb )) 743

4 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: a, a, a 3, a 4 and a 5 are the scalar quanttes whch characterzed the partcular devce beng smulated whle t s the relay operatng tme. Although today, dgtal relays or mcroprocessor relays wth ANSI and IEC standard curves are used, however for statc and electromechancal relays ether ANSI or IEC standard formula or the equaton can be appled [0, 5, 6, 7]..3 Prmary/Backup Relay Pars and Coordnaton Constrants Coordnaton constrants are assocated to prmary and backup relays. It s a common thng that every prmary relay has ts own backup relay to ensure dependable protecton system. The prmary relay operatng tme should be less than the backup relay to assure the protecton system [5, 6]. Ths ndcates that prmary protecton must clear fault as fast as possble n order to dsconnect the part of the network system. Tme gradng margn called the Coordnaton Tme Interval (CTI) must be ncluded between the prmary and backup relays operatng tme. Consder fault occurrng s symmetrcal balanced three phase fault. The relay s phase relay type. Relay p and b are the prmary relay and backup relay, respectvely. Fgure dsplay where the fault occurred. When fault occurs, both relays detect fault sgnal and start to operate smultaneously. These relays carry out the processng nformaton provded by the Current Transformer (CT) and then ssues trp sgnal to the Crcut Breaker (CB) so as the fault does not affect the whole system [5, 6]. Consder the fault happens near Relay R A. Relay R A s the prmary relay whle Relay R B s the backup relay. If Relay R A fals to operate, Relay R B wll take acton to operate. An approprate tme delay of the backup relay s set; R B s done n order to allow R B operates accordngly once the prmary relay fals to operate. It should be noted that the coordnaton constrant should be expressed n equaton below. where t = t t CTI (3) pb b p t b s the operatng tme of the backup relay due to fault t p s the operatng tme of the prmary relay due to fault CTI s the coordnaton tme nterval vares from s under dfferent condton To explan the role of coordnaton constrant, t pb, consder the value s postve, the t β ( t t )) wll be equal to t pb. However ( pb pb pb f t pb s negatve value, the expresson wll becomes:- ( t pb pb pb pb β ( t t )) = ( + β )( t ) (4) Normally, the CTI used for mcroprocessor relays around 0. to 0.s whle CTI for electromechancal relays s 0.3 to 0.4s. CTI usually depends on type of relays, relay tmng errors, CT error, speed of the crcut breaker and the overshoot tme of the relay..4 Bounds on Relay Operaton Tmes and Bounds on TSM and PSM Relay constrants covers the lmts or ranges of relay operatng tme and settngs. Based on the relay type, the operatng tme of relay s determned accordng to nverse curves. The bound s denoted as follows: t mn t t max, =,... m (5) where t mn and t max are the mnmum and maxmum operatng tmes of the th relay at the prmary fault locaton. The boundary constrants of TSM and I p whch s due to the lmts n the value of relay settngs are denoted as follows: Fgure : Example applcaton of drectonal overcurrent relay for feeder protecton TSM mn TSM TSM max, =,... m (6) I p mn I I max, p p =,... m (7) 744

5 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: The load currents should be less than pckup current and the pckup current should be lower than the mnmum fault current wth a reasonable securty margn [8]..5 Contnuous or Dscrete TSM or TDS Relays In [0], the author stressed that n order to fnd optmal coordnaton for relays settng, the TSM s or TDS s are based on contnuous form for contnuous TSM or TDS method. If TSM s or TDS s of the relays are n dscrete form, the output programmng results for each relay s rounded to the next upper allowable dscrete value of the relevant relay [0]. Moreover, ths method may affect coordnaton between prmary/backup relays and may produce naccuraces value. However, for dscrete TSM or TDS method, the output programmng results are dscrete drectly [0]. The TSM s or TDS s are to be sad dscrete nherently. Ths means that for each relay, the TSM or TDS s n bnary code. Therefore, there s no soluton for relays nherently f TSM or TDS are n contnuous form [0]. 3. MODIFIED SWARM FIREFLY ALGORITHM (MSFA) PSO was developed by Eberhart and Kennedy based on the analogy of swarm brds and schoolng fsh [9] but t suffers from a major drawback whch s convergence to a local optmum and not to the global optmum. The premature convergence sometmes happened n a case of hgh dmenson. The man reason why premature convergence happened s because the nformaton flow between partcles durng optmzaton process can lead to ncreasng of beng trapped n one of the local optmums [30]. In PSO, for the ntal phase smulaton, exploraton s needed due to hgh veloctes but after suffcent tme, the veloctes becomes smaller and even the nearest soluton to the space s almost mpossble to approach [3]. Many efforts have been made to address these ssues. Wth the ssues of havng multple local optma, t s proposed here that ths problem can be addressed by modfed the velocty equaton so that the partcles explore nto regon contanng global best and converge to the best poston. In ths paper, MSFA s developed and ntroduced to mprove the search capablty of PSO. The part of Frefly Algorthm (FA) whch s the cartesan dstance between two swarm frefles s used n the PSO algorthm to accelerate convergence speed. In addton, MSFA s developed to solve optmzaton problems and slow convergence occurred by PSO. Generally, MSFA s ncorporated nto drectonal overcurrent relay coordnaton problem. Frstly, the prmary/backup relay pars are dentfed. Then, for each prmary/backup relay pars, the short crcut currents are calculated. The followngs are the parameters that had been used durng ntalzaton. Step : Intalzaton In the frst step of MSFA process, the parameters are assgned wthn a certan lmts to ensure the partcles cannot overfly the regon. The followngs are some of the parameters durng ntalzaton: ω max ω mn c c α maxmum nerta weght mnmum nerta weght weght learnng factor weght learnng factor control parameter P a mutaton probablty, (0<P a <) Both maxmum and mnmum nerta weght wll be explaned n Step 3 whle two postve constant, c and c are the learnng factors. In MSFA algorthm, c s a cogntve parameter whch expresses the partcle towards ts own experence whle c, a socal parameter reflects the partcle s confdence towards ts neghbor. Accordng to Z. Wen and L. Yutan n [3], the settng wth c = c ndcates n both the pbest and gbest of the partcles populaton are consdered equally durng the searchng process. Ths condton s the best opton n order to obtan the best soluton. J. Kennedy and R. Eberhart n [8] defned that value of s the most sutable value for the partcles exploraton n the search space. The control parameter, α value s selected carefully to ensure the partcles explore of the search space wthn regon whle the mutaton probablty, P a, s selected as 0.9 [33]. The mutaton probablty task s to control the behavor of the algorthm and mprove the performance of PSO. Furthermore, P a s requred to prevent the premature convergence of the PSO to suboptmal solutons. 745

6 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: The MSFA generate varable x. Ths x depends on the number of populaton sze, number of dmensons and other varables. The value of N populaton szes or partcles vares from 50 to 50. Ths s to seek whch populaton szes n MSFA method produces better results for drectonal overcurrent relay coordnaton. Moreover, t s mportant that ths parameter need to be addressed properly so as t can mprove convergence speed. The dmenson of the partcles s referred to number of relays. The TSM s sets,.e. (TSM, TSM, TSM 4 ) whch belong to relay R, R, R 4 are ntally randomly selected. These TSM s sets of relays are rounded. Step : Generate maxmum velocty In the basc PSO, veloctes of partcles on each dmenson are clamped to a maxmum velocty, V max. The value of velocty s clamped between the range of V max and V max to ensure the partcles don t fly out of the search space. Accordng to [34], f the search space s defned by the bounds X max and X max, the value of V max s set as follows: where 0. k Step 3: Generate an nerta weght v max = kx max (8) An nerta weght s assgned to enable the populaton of the partcles to have a hgh chance n obtanng global optmum results [5, 35]. Ths parameter plays an mportant task to determne the probablty of the partcles to search for global optmum search. Ths nerta weght s determned usng lnearly decayng proposed by author n [36]. It can be calculated by usng eq. (9) below: ωmax ωmn ω = ωmax k (9) k max where ω max and ω mn are the maxmum and mnmum nerta weght, whle k and k max are the current and maxmum teraton respectvely. In [36], the nerta weght value for maxmum s specfed as 0.9 whle the mnmum nerta weght ends at 0.4. Ths nerta weght value s selected properly to ensure the partcles of the MSFA tend to have more global search ablty n the begnnng of ntal searchng. Step 4: Ftness functon evaluaton Each partcle or populaton szes n MSFA moves around n a mult-dmensonal search space n order to look for the best soluton. The swarm frefly memorzes ts current poston by evaluatng the ftness functon, the best poston and the velocty durng ts searchng space. Ths s referred as personal best or known as pbest. The pbest ndcates the hghest ftness value for that partcle. The best poston among all the pbest postons s commonly known as global best or gbest. M.M. Mohamed et al. n [4] explaned that for mnmzng a functon, the poston of havng a smaller value s regarded as hgher ftness. Step 5: Update dstance In the FA, the dstance between two frefles ncreases when the brghtness of one frefly s decreases compared to the other one. The parameters r j as the dstance between the th and j th frefly can be evaluated n the Cartesan framework. However, n the MSFA, the dstance between poston, x and pbest (n PSO algorthm) respectvely s consdered n the Cartesan framework: r = px = D k = pbest x ( pbest, x, ) k ( t) k (0) where r px s the dstance between two swarm frefles, p best and x As n PSO algorthm, gbest s also taken nto account. The dstance between poston, x and gbest can be evaluated n the Cartesan framework as follows: r = gx = D k = gbest x ( gbest, k x, k ) ( t) () where r gx s the dstance between two swarm frefles, g best and x 746

7 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Step 6: Partcle velocty calculaton When the value of pbest and gbest are determned, the velocty of partcle s randomly mutated usng MSFA equaton (): k k k+ ωv + crand ( pbest x ) v =, rand P k a + crand ( gbest x ) else () k+ v k ωv + rand e = ( r gx + rand e ( rpx ) ) ( pbest x ) k ( gbest x ) + α( rand 0.5) k where v k s the earler velocty of partcle, rand s the random numbers n the range of 0 and, c, c are two postve constants, ω s the nerta weght, α s the control parameter. Step 7: Update partcle poston The new poston of the partcle can be calculated usng equaton (3) below: x = x + v k + k k + (3) k where x s the old poston of the partcle, s the new updated velocty of partcle. Step 8: End condton k + v When the maxmum number of teraton has been reached, MSFA wll stop ts processes. The complete algorthm of the MSFA nto drectonal overcurrent relay coordnaton problem can be summarzed n Fg.. Fgure : Complete Algorthm for MSFA 4. RESULTS AND DISCUSSION The development of the MSFA method was smulated usng MATLAB and executed on Intel Core 5.53 GHz wth 4 GB RAM. The effectveness of the proposed method was tested nvolvng 8-Bus system and 9-Bus system. The effect of populaton or partcle szes to MSFA method s also nvestgated for both cases. In each case, the acheved results are compared wth PSO algorthm. To prove the effectveness of MSFA technque, determnaton of α, α and β are mportant factor n order to evaluate the objectve functon. The varatons of α, α and β are lsted n Table. Table : Parameter Varatons. Case Number α α β Case 00 Case 0 747

8 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: It s assumed that the TSM s of the relays vares from 0 to. The nformaton of data network can be found n [0]. The characterstc coeffcents; a, a, a 3, a 4 and a 5 for the drectonal overcurrent whch are dependent on the type of relay are gven n Table. Table : Characterstc Coeffcents. a a a 3 a 4 a Case : Eght-Bus Test System Ths case consders 8-Bus System whch conssts of 8 buses, 7 lnes, generators, transformers and 4 overcurrent relays. The sngle lne dagram of the test system s shown n Fgure 3. The short crcut current calculaton for prmary relay and backup relay s based on 00 MVA and 50 kv. The short crcut current of prmary and backup relay s calculated for the fault near to the CB of the prmary relay for each prmary/backup relay. The unts for prmary relays and backup relays current are n Amperes. The nformaton on pckup current settngs for the 4 relays can be found n [7]. For phase protecton, the pckup current s set. tmes maxmum load current. Table 3, Table 4 and Table 5 depcts the results of comparatve studes between MSFA and PSO for Case, 8-Bus test system. These tables are consdered as the best results among 30 runs for each populaton szes and two cases of parameter varatons wth 500 teratons. Table 5 ndcates the results for TSM values between dfferent number of populaton sze usng MSFA and PSO technques. For Case, when β s 00, both MSFA and PSO contrbutes total TSM s wth.63s. It can be observed that, the sutable populaton sze s 00 compare to 50 and 50. Ths s due to lesser total TSM s compare to 50 but for 50, t took more computaton tme to produce.63s. For Case, when β s not consdered, the total TSM s for PSO technque seems to be much lesser than MSFA when number of populaton s 50 and 00 but MSFA exhbts much lesser total TSM s compare to PSO for 50 populaton sze. By sutable selecton of parameters values, Case s consdered the best choce n ths study. Ths ndcates that the selecton of α, α and β for Case s correct n ensurng mscoordnaton s avoded. Fgure 3:8-Bus test system 748

9 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Cases Table 3: Tme Settng Multpler Value of 8-Bus system No. of Populaton Sze Tme Settng Multpler (TSM) Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Technques MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO TSM No TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM Iteraton 500 total tme settng multpler (s) Cases Case [weght: β =00 ] Table 4: Relay Operatng Tme of 8-Bus system No. of Populaton Sze Relay Operatng Tme for a fault near to Crcut Breaker (CB) (t ) Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Technques MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO t t t t t t t t t t t t t t t Iteraton 500 total operatng tme of prmary relays (s)

10 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: From Table 4, there are fourteen relays operatng tme, t to t 4. It s dscovered that n Case for 00 and 50 populaton szes, both MSFA and PSO consumes same total operatng tme of prmary relays,.e s whereas MSFA and PSO consumes 6.57s and 6.904s for 50 populaton sze. Both total operatng tme of prmary relay usng MSFA and PSO technque for populaton sze 00 and 50 have been reduced to 4.79% and 5.34% compare to 50 populaton szes respectvely. Ths mples that both MSFA and PSO consume lesser tme for 00 and 50 populaton szes. However, t can be observed that the sutable populaton sze s 00 compare to 50 due to executon tme. It s also dscovered that for Case, both MSFA and PSO consumes lesser tme for 50, 00 and 50 populaton szes. For 50 populaton sze, MSFA consumes.407s and PSO consumes.34s. It can be seen also that there s slghtly dfference tme for both technques n 00 and 50 populaton szes. The range of tme s between 0.5s to 0.6s. The results obtaned ndcate that for 50 populaton sze, MSFA consumes lesser tme compare to PSO. Cases Case [weght: α =, α =, β =00 ] Table 5: Relay Coordnaton Tme for each Relay Pars of 8-Bus system No. of Populaton Sze Relay Coordnaton Tme for each relay pars, t pb Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Technques MSF t pb A PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO ** t t t t t t t ** t t 6, t 4, ** t 4, t t 9, t 0, t, t, t, t 3, ** t t 7, Iteraton 500 Computat on tme (s) Objectve Functon (s) Table 5 ndcates 0 relay pars for 50, 00 and 50 populaton szes wth computaton tme and objectve functon for both MSFA and PSO technques as well as two cases. For Case, the objectve functon for both MSFA and PSO wth 00 populaton sze s consdered as the best results,.e. 4.7s compare to 50 and 50 populaton szes. Ths s because 00 populaton szes contrbute less executon tme. MSFA technque reaches global optmum after 75 teratons whle PSO reach global optmum after 33 teratons. Ths shows that results by PSO technque reveal poor convergence compare to MSFA. In terms of computaton tme, MSFA exhbts s whch s 3% faster than PSO. 750

11 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: The convergence curves for each method wth 00 populaton sze can be llustrated n Fg. 4. It can also be seen that from Table 5, some values of t pb are zero. For nstance, the coordnaton tme between relays 6 and 5 does not requre coordnaton tme as marked (**) n the table. Ths s due to relay 6 whch s assocated to a generator-transformer bus. In such case, coordnaton study s unnecessary [0]. Other prmary relays wth t pb equal to zero are also lnked to generator-transformer buses such as relays 8 and 9, relays 4 and 9 and relays 7 and 5. 3 x 05.5 MSFA PSO Fgure 5:9-Bus test system O b je c tv e F u n c to n, O f Iteraton Fgure 4: Convergence of MSFA and PSO for Case wth 00 populaton sze 8-Bus test system Case : Nne-Bus Test System Ths case consders 9-Bus System whch conssts of 9 buses, 6 lnes, 3 generators, 3 transformers and overcurrent relays. The sngle lne dagram of the test system s shown n Fgure 5. The nformaton on pckup current settngs for the relays can be found n [37]. For phase protecton, the pckup current s set.5 tmes maxmum load current. Table 6, Table 7 and Table 8 depcts the results of comparatve studes between MSFA and PSO for Case, 9-Bus test system. These tables are consdered as the best results among 30 runs for each populaton szes and two cases of parameter varatons wth 500 teratons. Table 6 ndcates the results for TSM values between dfferent number of populaton sze usng MSFA and PSO technques. For Case, β s 00, MSFA contrbutes total TSM s wth 3.73s compare to PSO wth 3.77s. It can be observed that, the sutable populaton sze s 00 compare to 50 and 50. Ths s due to lesser total TSM s compare to 50 but for 50, t took more computaton tme to produce 3.73s. For Case, when β s not consdered, the total TSM s for PSO technque seems to be lesser when number of populaton s ncreased from 50 to 50 but MSFA exhbts same total TSM s whch s 0.85s. From Table 7, there are twelve relays operatng tme, t to t. It s dscovered that n Case for 50 populaton sze, both MSFA and PSO consumes same total operatng tme of prmary relays,.e..34s whle PSO consumes.374s and MSFA consumes.34s for 00 populaton sze. As for 50 populaton sze, both MSFA and PSO consume.696s and.4439s. Ths mples that both MSFA and PSO consume lesser tme for 00 and 50 populaton szes. It s also dscovered that for Case, MSFA consumes more total operatng tme of relays for 50, 00 and 50 populaton szes compare to PSO technque. 75

12 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Cases Table 6: Tme Settng Multpler Value of 9-Bus system No. of Populaton Sze Tme Settng Multpler (TSM) Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Case [weght: α =, α =, β =00 ] Case [weght: α =, α =, β =0] Technques MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO TSM No TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM TSM Iteraton 500 total tme settng multpler (s) Cases Technque Case [weght: β =00 ] Table 7: Relay Operatng Tme of 9-Bus system No. of Populaton Sze Relay Operatng Tme for a fault near to Crcut Breaker (CB) (t ) Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO t t t t t t t t t t t t t Iteraton 500 total operatng tme of prmary relays (s)

13 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Cases Case [weght: β =00 ] Table 8: Relay Coordnaton Tme for each Relay Pars of 9-Bus system No. of Populaton Sze Relay Coordnaton Tme for each relay pars, t pb Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Case [weght: β =00 ] Case [weght: β =0] Technque s MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO MSFA PSO t pb t t t t t t t t t 9, t 0, t, t, t Iteraton 500 Computa ton tme (s) Objectve Functon (s) Table 8 ndcates relay pars for 50, 00 and 50 populaton szes wth computaton tme and objectve functon for both MSFA and PSO technques as well as two cases. For Case, the objectve functon for both MSFA and PSO wth 00 populaton sze s consdered as the best results,.e..5740s compare to 50 and 50 populaton szes. Ths s because 00 populaton szes contrbute less executon tme. MSFA technque reaches global optmum after 65 teratons whle PSO reach global optmum after 44 teratons. Although MSFA technque slghtly reveals poor convergence compare to PSO, MSFA stll contrbutes mnmum ftness functon compare to PSO. In terms of computaton tme, MSFA exhbts s whch s s faster than PSO. The convergence curves for each method wth 00 populaton sze can be llustrated n Fg. 6. O b je c tv e F u n c to n, O f 3.5 x Iteraton Fgure 6: Convergence of MSFA and PSO for Case wth 00 populaton sze 9-Bus test system MSFA PSO 753

14 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: CONCLUSION Ths paper has presented the new method called as MSFA n solvng drectonal overcurrent relay coordnaton problem. The effectveness of MSFA was successfully mplemented and tested on the 8- Bus test system and 9-Bus test system. From the results, t can be revealed that the proposed MSFA technque demonstrates sgnfcant results n 50, 00 and 50 populaton szes for two cases to avod mscoordnaton n relay operaton as compared to PSO. As concluson, the sutable populaton sze for the two cases s 00 based on the less computaton tme and mnmum ftness value for every smulaton. In terms of computaton tme, MSFA s faster than PSO whch s feasble to be mplemented n a larger system. ACKNOWLEDGEMENT The authors would lke to acknowledge The Research Management Insttute (RMI) UTM, Shah Alam and Mnstry of Hgher Educaton Malaysa (MOHE) for the fnancal support of ths research. Ths research s supported by MOHE under the Exploratory Research Grant Scheme (ERGS) wth project code: (Fle No: 600-RMI/ERGS 5/3(/03). REFRENCES: [] Y. G. Panthakar and Bhde, S.R., "Fundamentals of Power System Protecton," 5th ed: Prentce-Hall of Inda Prvate Lmted, New Delh, 007. [] P.M. Anderson, Power System Protecton, McGraw-Hll, New York, 999. [3] M.H. Hussan, I. Musrn, S.R.A. Rahm, and A.F. Abdn, Computatonal Intellgence Based Technque n Optmal Overcurrent Relay Coordnaton: A Revew, The Internatonal Journal of Engneerng And Scence (IJES), Vol., Issue, Jan 03, pp [4] M.H. Hussan, S.R.A. Rahm, I. Musrn, Optmal Overcurrent Relay Coordnaton: A Revew, Proceda Engneerng 53, 03, pp [5] S.A. Raza, T. Mahmood, S.B.A. Bukhar, M.K. Nawaz, Applcaton of Optmzaton Technques n Overcurrent Relay Coordnaton A Revew, World Appled Scences Journal, vol 8, ssue, 03, pp [6] V. S. Chaudhar, V.J. Upadhyay, "Coordnaton of overcurrent relay n nterconnected power system protecton," n Natonal Conference on Recent Trends n Engneerng & Technology, 0. [7] A. J. Urdaneta, Nadra, R. and Perez, L., "Optmal coordnaton of drectonal overcurrent relay n nterconnected power systems," IEEE Transactons on Power Delvery, vol. 3, 988, pp [8] C. W. So, K.K. L, K.T. La, K.Y. Fung, "Applcaton of genetc algorthm for overcurrent relay coordnaton," n IEEE Conference Developments n Power System Protecton, 997, pp [9] C. W. So, K.K. L, "Overcurrent relay coordnaton by evolutonary programmng," Electrc Power Systems Research, vol. 53, 000, pp [0] F. Razav, Abyaneh, H.A., Al-Dabbagh, M., Mohammad, R., Torkaman, H., "A new comprehensve genetc algorthm method for optmal overcurrent relays coordnaton " Electrc Power Systems Research, vol. 78, 008, pp [] D.P. Kothar, Power System Optmzaton, nd Natonal Conference on Computatonal Intellgence and Sgnal Processng (CISP), 0, pp. 8-. [] J. Senthlnath, S.N. Omkar and V. Man, Clusterng usng Frefly Algorthm: Performance Study, Swarm and Evolutonary Computaton, vol., 0, pp [3] H. H. Zeneldn, E.F. El-Saadany, M.M.A. Salama, "Optmal coordnaton of overcurrent relays usng a modfed partcle swarm optmzaton," Electrc Power Systems Research, vol. 76, pp , 006. [4] M. M. Mohamed, Sad, F.M., Nehad, E.E., "A modfed partcle swarm optmzer for the coordnaton of drectonal overcurrent relays," IEEE Transactons on Power Delvery, vol., 007, pp [5] M.H. Hussan, I. Musrn, S.R.A. Rahm, A.F. Abdn, A. Azm, Optmal Overcurrent Relay Coordnaton Usng Partcle Swarm Optmzaton, 03 Internatonal Conference on Electrcal, Control and Computer Engneerng, (InECCE 03), 03, pp [6] A. Kordon and A.K. Kordon, Swarm Intellgence: The Benefts of Swarms, Sprnger-Verlag Berln Hedelberg, Applyng Computatonal Intellgence, pp , 00. [7] D. Uthtsunthorn, Pao-La-Or, P., Kulworawanchpong, T., "Optmal overcurrent relay coordnaton usng artfcal bees colony algorthm " n ECTI-CON 0-8th Electrcal 754

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