Electrical Performance of Polymer-Insulated Rail Brackets of DC Transit Subjected to Lightning Induced Overvoltage

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Article Electrical Performance of Polymer-Insulated Rail Brackets of DC Transit Subjected to Lightning Induced Overvoltage

Farah Asyikin Abd Rahman 1,* , Mohd Zainal Abidin Ab Kadir 2 , Ungku Anisa Ungku Amirulddin 1 and Miszaina Osman 1

1 Institute of Power Engineering (IPE), Universiti Tenaga Nasional (UNITEN), Kajang 43000, Selangor, Malaysia; [email protected] (U.A.U.A.); [email protected] (M.O.) 2 Centre for Electromagnetic and Lightning Protection Research (CELP), Advanced Lightning, Power and Energy Research Centre (ALPER), Universiti Putra Malaysia (UPM), Serdang 43400, Selangor, Malaysia; [email protected] * Correspondence: [email protected]

Abstract: The fourth rail transit is an interesting topic to be shared and accessed by the community within that area of expertise. Several ongoing works are currently being conducted especially in the aspects of system technical performances including the rail bracket component and the sensitivity analyses on the various rail designs. Furthermore, the lightning surge study on railway electrification is significant due to the fact that only a handful of publications are available in this regard, especially on the fourth rail transit. For this reason, this paper presents a study on the electrical performance of a fourth rail Direct Current (DC) urban transit affected by an indirect lightning strike. The indirect lightning strike was modelled by means of the Rusck model and the sum of two Heidler functions. The simulations were carried out using the EMTP-RV software which included the performance comparison of polymer-insulated rail brackets, namely the Cast Epoxy (CE), the Cycloaliphatic Epoxy Citation: Abd Rahman, F.A.; Ab Kadir, M.Z.A.; Ungku Amirulddin, A (CEA), and the Glass Reinforced Plastic (GRP) together with the station arresters when subjected U.A.; Osman, M. Electrical by 30 kA (5/80 µs) and 90 kA (9/200 µs) lightning currents. The results obtained demonstrated Performance of Polymer-Insulated that the GRP material has been able to slightly lower its induced overvoltage as compared to other Rail Brackets of DC Transit Subjected materials, especially for the case of 90 kA (9/200 µs), and thus serves better coordination with the to Lightning Induced Overvoltage. station arresters. This improvement has also reflected on the recorded residual voltage and energy Materials 2021, 14, 1684. https://doi. absorption capacity of the arrester, respectively. org/10.3390/ma14071684 Keywords: DC transit; EMTP-RV; fourth rail; indirect lightning; lightning induced overvoltage; Academic Editor: Tomasz Sterzynski surge arrester

Received: 22 January 2021 Accepted: 16 March 2021 Published: 29 March 2021 1. Introduction

Publisher’s Note: MDPI stays neutral A fourth rail traction technology came into the picture as a post development of the with regard to jurisdictional claims in third rail traction technology. The main advantage of the fourth rail traction is that the published maps and institutional afﬁl- running rails would not have to carry either polarity of current, thus avoiding the stray iations. current issue which can lead to corrosion and even arcing, especially if the tunnel segments are not electrically bonded [1]. For instance, in the case of London Underground, which runs through Victorian mains that predated the railway section, where the pipe segments were never constructed to serve that purpose [2]. London Underground is one of the three urban transits in the world that employs the fourth rail traction technology. The other Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. two are Milan Metro Line 1 and the Light Rail Transit (LRT) Kelana Jaya Line in Italy This article is an open access article and Malaysia, respectively [1,2]. The LRT Kelana Jaya line is distinguished by not only distributed under the terms and running underground but being the only one that partially runs on the elevated track. This conditions of the Creative Commons track is 42.1 km long and 17 m above the ground. Whilst the underground route is 4.3 km Attribution (CC BY) license (https:// stretching as far as ﬁve consecutive stations running underneath the Kuala Lumpur Central creativecommons.org/licenses/by/ Business District en route to Gombak from Putra Heights [3]. However, running on the 4.0/). elevated track has given the stress on the operation of direct current (DC) urban transit and

Materials 2021, 14, 1684. https://doi.org/10.3390/ma14071684 https://www.mdpi.com/journal/materials Materials 2021, 14, 1684 2 of 17

its maintenance credibility, i.e., lightning protection, especially when the track is built and operated in a city that is ranked at the fifth-highest lightning activity in the world [4]. The LRT Kelana Jaya line has been in operation for the last 21 years and throughout its two decades of service, the line has experienced a number of technical disturbances and traction power loss due to lightning. The first incident was reported on 15 November 2010 when the line was struck by lightning and caused the train to fail to stop at its four out of five subway stations namely Kuala Lumpur City Centre (KLCC), Kampung Baru, Dang Wangi, and Masjid Jamek [5]. Three years later, another lightning strike has caused the traction power loss in some areas, which consequently caused delays and left the commuters stranded at the stations [6]. The probable cause of these incidents was reported due to the health and insulation strength of the electrical equipment. Typically, an overhead line running transit runs in an open area and thus, is highly susceptible to lightning. Hence, the overwhelming lightning protection studies and research development were dedicated to this type of transit. This is in contrast to the third rail transit studies which are normally underground and thus, protected from the lightning. In this case, the issue seemed to be highly attentive to the stray current. On another note, if the third rail system runs on the elevated track, that particular section may be shielded by neighbouring buildings [7]. However, this study focuses on an elevated fourth rail transit which consists of civil and electrical structures that is distinguished from other systems. With the limitation of the available references, this study intends to fill in the research gap pertinent to the lightning surge analyses of an urban transit on the fourth rail traction, with particular interest in the insulated rail bracket and station lightning arrester.

2. Case Study and Methods 2.1. The Kelana Jaya Line Boasted as the busiest light rail transit in Malaysia with 46.4 km line length, the LRT Kelana Jaya line runs seamlessly between the north eastern suburbs of Kuala Lumpur to Petaling Jaya and west of Kuala Lumpur with 37 stations [1]. This electric transit train runs on a 750 VDC fourth rail system and has been operating for two decades. The LRT Kelana Jaya line is unique in its own way due to its elevated fourth rail traction and distinct power rail arrangement, as compared to the ones in Milan and London. The power rails of the LRT Kelana Jaya line are mounted parallel with each other, with an insulator in place to isolate the positive rail (third rail) and the negative rail (fourth rail). This insulator is known as the insulated rail bracket, which is the primary subject for this study. In this study, a section of Setiawangsa Station to Damai Station was chosen due to its elevated routes which are located between Sri Rampai Station and Ampang Park Station. To the best of the author’s knowledge, there is no surge arrester installed along the 3 km power rails, which are considered in this study. Generally, the arresters are installed in the vicinity of the electrical equipment to be protected, for the purpose of minimizing the risk of equipment failure due to high surges.

2.2. Power Rails The limited references of the fourth rail transient study has provided the idea of conceptualization of the tower surge impedance model to portray the power rail representation. These two structures are more or less similar in terms of the conductor physical structure. Although the power rails serve the same purpose as any transmission line, they do not share the same conductor structure. Unlike transmission lines whose cross sections are circular and constructed from more than one conductor wire, power rails are made up from a solid conductor with an irregular cross section [8], and therefore sharing more of a resemblance with the structure of a transmission tower. Furthermore, even though the lightning response of a transmission tower is an electromagnetic phenomenon, yet researchers and physicists are able to represent the tower structure by means of line sections and circuit elements (e.g., resistors, inductors, and capacitors) [9]. This makes the power rail impedance adaptation of the tower surge impedance easier to be simulated in the Materials 2021, 14, x FOR PEER REVIEW 3 of 18

Materials 2021, 14, 1684 3 of 17 lightning response of a transmission tower is an electromagnetic phenomenon, yet researchers and physicists are able to represent the tower structure by means of line sections Electromagneticand circuit elements Transients (e.g., resistors, Program—Restructured inductors, and capacitors) Version (EMTP-RV) [9]. This makes software. the power There arerail manyimpedance styles adaptation and perspectives of the concerningtower surge the impedance tower surge easier impedance. to be simulated However, in thethe followingElectromagnetic Equations Transients (1)–(3) [ 9Program—Restru], appear to be morectured appropriate Version (EMTP-RV) for representing software. the rail There con- ﬁgurationare many styles (Figure and1a) withperspectives the equivalent concerning shape the of transmissiontower surge impedance. line tower (Figure However,1b) [ the9], knownfollowing as theEquations H-frame (1)–(3) tower. [9], As appear for the to ground, be more the appropriate cemented guideway for representing demonstrates the rail a perfectconfiguration conducting (Figure ground 1a) with [10]. the equivalent shape of transmission line tower (Figure 1b) [9], known as the H-frame tower. As for theZ +ground,Z the cemented guideway demon- Z = s m (1) strates a perfect conducting ground [10].t 2

FigureFigure 1.1. ((aa)) TheThe orientationorientation ofof thethe powerpower rails.rails. ((bb)) TheThe H-frameH-frame towertower model.model.

With Zt = − Zs = 60ln(L/r) + 90(r/L) 60 (2)(1) With Zm = 60ln(L/b) + 90(b/L) − 60 (3)

where L is the length of the powerZs = rail 60ln(L/r) (m), r is+ the90(r/L) radius − 60 of the power rail (m), b is the(2) distance between the rails (m), Zs is self-impedance (Ω), and Zm is mutual impedance (Ω). Zm = 60ln(L/b) + 90(b/L) − 60 (3) 2.3. Insulated Rail Bracket where L is the length of the power rail (m), r is the radius of the power rail (m), b is the distanceThe between LRT Kelana the Jayarails line(m), has Zs is a distinctself-impedance power rail (Ω arrangement,), and Zm is mutual i.e., mounted impedance parallel (Ω). to each other. For this reason, an insulator is essential to isolate the positive rail (third rail) from2.3. Insulated the negative Rail Bracket rail (fourth rail), on top of acting as the rail support. The conceptualization of the respective power rail insulated rail brackets is realized in the same manner as The LRT Kelana Jaya line has a distinct power rail arrangement, i.e., mounted parallel per the power line insulator which embodies a capacitor, apart from different dielectric to each other. For this reason, an insulator is essential to isolate the positive rail (third rail) insulations to be used to represent the Cast Epoxy (CE), the Cycloaliphatic Epoxy A (CEA), from the negative rail (fourth rail), on top of acting as the rail support. The conceptualiza- and the Glass Reinforced Plastic (GRP), with the CE bracket set as the LRT line rail bracket. tion of the respective power rail insulated rail brackets is realized in the same manner as Equation (4) quantiﬁes an appropriate adaptation of capacitance to be used in this study. per the power line insulator which embodies a capacitor, apart from different dielectric insulations to be used to represent the CaAstε Epoxyε (CE), the Cycloaliphatic Epoxy A C = 0 r (4) (CEA), and the Glass Reinforced Plastic (GRP),d with the CE bracket set as the LRT line rail

where C is capacitance, A is the area between the plates (m2), 0.006764 m2, d is the distance −12 between the plates (m), 0.083 m, ε0 is the permittivity of free space, 8.85 × 10 F/m, εr is

Materials 2021, 14, 1684 4 of 17

the permittivity of GRP dielectric, 5 [11], εr is the permittivity of CE dielectric, 4 [12], and εr is the permittivity of CEA dielectric, 3.5 [13]. In the presence of high-voltage stress on the power rails, where the structures are separated only by air and insulated rail brackets every 5 m, the flashover is always expected to occur across the insulated rail brackets, unless surge arresters are installed along the power rails. This is due to the fact that as the stress increases to a point that exceeds the electric strength of the air (3 × 106 V/m) [14,15], and the bracket material, a spark travels from one conductor rail to the other and if the stress is sustained, this may also be followed by a continuous arc, hence, a flashover. In modelling this occurrence, a flashover switch was connected across the insulated rail brackets that closed accordingly when the presence of the high-voltage stress exceeds the calculated flashover voltage (FOV) of the bracket material. The bracket FOV was calculated by Equation (5). The flashover voltage of the insulated rail bracket was calculated through this calculation [16,17]: 710 V = 400 + × ` (5) t0.75 where V is the flashover voltage (kV), t is the time to flashover (range 0.5 to 16 µs) and in this study it is 2 µs [17], and ` is the insulated rail brackets length (m), 0.076 m. According to IEEE STD 1410-2010, to obtain an estimated value for the critical flashover (CFO) for wet conditions, the dry CFO values were multiplied by 0.8 ± 0.1 [18]. On the other hand, the IEEE Standard 1410 defines the basic insulation level (BIL) as the crest value of a standard lightning impulse, in which the insulation exhibits a 90% probability of withstands (or a 10% probability of failures) under specified conditions [18] and can be expressed as in Equation (6) [19,20]: σ BIL = CFO (1 − 1.28 f ) (6) CFO

with σf as the coefﬁcient of the variation, known as sigma. For lightning, the sigma is between 2% to 3%.

2.4. Traction Substation Surge Arrester The location of the arresters for this study were assumed to be at the entrance of the DC side of the traction substation. The arrester was modelled based on the Institute of Electrical and Electronics Engineers (IEEE) model where it takes into account both the electrical data (residual voltages), and the physical parameters (overall height, block diameter, number of columns) [14], as well as it works splendidly with the impulse current ﬂow with a wave front between 0.5 to 45 µs [21,22]. The respective designed IEEE model is shown in Figure2 with its parameters established through Equations (7)–(11):

15d L = µH (7) 1 n 65d R = Ω (8) 1 n 0.2d L = µH (9) 0 n 100d R = Ω (10) 0 n 100n C = pF (11) d where d is the estimated height of the arrester (m) and n is the number of arrester columns in parallel [23]. Materials 2021, 14, x FOR PEER REVIEW 5 of 18

100d R = Ω (10) n 100n C = pF (11) d Materials 2021, 14, 1684 where d is the estimated height of the arrester (m) and n is the number of arrester col-5 of 17 umns in parallel [23].

FigureFigure 2. 2. TheThe Institute Institute of ofElectrical Electrical and and Electronics Electronics Engineers Engineers (IEEE)model (IEEE)model as the as thesurge surge arrester arrester representationrepresentation [24]. [24]. 2.5. Indirect Lightning and LIOV Modelling 2.5. Indirect Lightning and LIOV Modelling Indirect lightning occurs when a strike from lightning hits the ground or an object Indirect lightning occurs when a strike from lightning hits the ground or an object is is in the vicinity of the DC transit track. This event subsequently initiates a travelling in the vicinity of the DC transit track. This event subsequently initiates a travelling tran- transient voltage via conductors and inductively induces a few hundred of kilovolts that sient voltage via conductors and inductively induces a few hundred of kilovolts that can can damage or destroy any unprotected electronic components [25]. The indirect lightning damage or destroy any unprotected electronic components [25]. The indirect lightning was modelled using the Heidler channel base current model or known as the Heidler was modelled using the Heidler channel base current model or known as the Heidler function. Whilst the lightning induced overvoltage (LIOV) was modelled based on the function. Whilst the lightning induced overvoltage (LIOV) was modelled based on the Rusck model. Rusck model. The proposed Heidler function is shown in the following Equations (12) and (13) [26]: The proposed Heidler function is shown in the following Equations (12) and (13) [26]: t n ( ) t I0 τ1t (− τ ) I(0, t) = × ( ) n × e 2 (12) η I τt ( ) ( ) 1 + ( τ ) I 0, t = × 1t × e (12) η 1+( ) where τ ( ) τ1 nτ2 1/n where η = exp [−( ) × ( ) ] (13) τ2 τ1 τ I0 is the channel base current peak value of the Heidler function, 1 is the time constant 𝞰 = exp [-( ) × ( )(1/n)] (13) of the wave front of the Heidler function, τ2 is the time constant of the wave decay of the Heidler function, n is the exponent of the Heidler function (usually holds a value between 2 and 10), and η is the amplitude correction factor of the Heidler function. I0 is the channel base current peak value of the Heidler function, τ1 is the time constant of In reproducing the lightning current waveshape with a concave rising portion, Equation (12) the wave front of the Heidler function, τ2 is the time constant of the wave decay of the Heidlerwas repeated function, twice n is and the resultedexponent in of Equations the Heidler (14) function and (15) (usually [27–29]: holds a value between

2 and 10), and 𝞰 is the amplitudet ncorrection1 factor of the Heidlert nfunction.2 ( ) t ( ) t I1 τ (− ) I2 τ (− ) In reproducingI(0, t) = the× lightning11 current× e waveshapeτ12 + with× a concave21 rising× e portion,τ22 Equa-(14) t n1 t n2 η1 1 + ( ) η2 1 + ( ) tion (12) was repeated twice andτ11 resulted in Equations (14) andτ 21(15) [27–29]:

t t where ( ) I τ I τ ( ) I(0, t) = × × e + × × e (14) τ η n τ t(1/n1) η τ t n τ (1/n2) η = exp [−( 11 ) × ( 1+(1 12 ) ) ] and η = exp [−1+(( 21 ))× ( 2 22 ) ] (15) 1 τ 2 τ τ12 τ11 τ22 τ21 While the Rusck model can be obtained from Equation (16):      2 2 ζ0I0h ct − x x + β (ct − x) ct + x x + β (ct + x) v (x, t) = β 1 +  + 1 +  (16) 2 2 2 q 2 2 2 2 2 q 2 2 4π d + β (ct − x) β 2 + x +d d + β (ct + x) β 2 + x +d ( ct) γ2 ( ct) γ2 Materials 2021, 14, x FOR PEER REVIEW 6 of 18

where

𝞰1 = exp [−( ) × ( )(1/n1)] and 𝞰2 = exp [−( ) × ( )(1/n2)] (15)

While the Rusck model can be obtained from Equation (16):

⎛ ⎛ ⎞ ⎛ ⎞⎞ ζ I h ct − x x+β(ct − x) ct + x x+β(ct + x) ⎜ ⎜ ⎟ ⎜ ⎟⎟ v (x, t) = β ⎜ 1+ + 1+ ⎟ (16) 4π d +β (ct − x) ⎜ ⎟ d +β (ct + x) ⎜ ⎟ ⎜ x +d x +d ⎟ (βct) + (βct) + γ γ ⎝ ⎝ ⎠ ⎝ ⎠⎠ Materials 2021, 14, 1684 6 of 17 where β is the (v is the return stroke velocity and c is the speed of light), ζ0 represents 376.730313 Ω (free space characteristic impedance), I0 is the channel base current peak, d is the horizontalv distance, x is the vertical distance from a lightning stroke, h is the guide- where β is the c (v is the return stroke velocity and c is the speed of light), ζ0 represents way376.730313 height, andΩ (free γ is space 1/ characteristic1−β . impedance), I0 is the channel base current peak, d is the horizontal distance, x is the vertical distance from a lightning stroke, h is the guideway p 2.6.height, EMTP-RV and γ Modellingis 1/ 1 − β2.

2.6.As EMTP-RV highlighted Modelling in Figure 3, a complete system was modelled as per the Single Line Drawing (SLD) provided. Any feature of the LRT line power system that exhibits a low or As highlighted in Figure3, a complete system was modelled as per the Single Line zeroDrawing reaction (SLD) towards provided. the intended Any feature study of thewas LRT omitted line power in order system to simplify that exhibits the model a low and to notor zero be a reaction hindrance towards in terms the intended of the studycomput wasational omitted speed. in order The to salient simplify features the model such as transformers,and to not be rectifiers, a hindrance filter in termss, power of the rails, computational insulated speed. rail Thebrackets, salient and features surge such arresters as weretransformers, also considered. rectifiers, The filters, system power was rails, mode insulatedlled railand brackets, simulated and surgein the arresters electromagnetic were specialistalso considered. software The named system El wasectromagnetic modelled and Transients simulated in Pr theogram electromagnetic Restructured specialist Version (EMTP-RV).software named The EMTP-RV Electromagnetic is a software Transients suited Program for the Restructured transient study Version specifically (EMTP-RV). in han- dlingThe an EMTP-RV electromagnetic is a software time suited constant for thewhich transient is significantly study specifically smaller in (faster handling transient), an electromagnetic time constant which is significantly smaller (faster transient), ranging in ranging in duration from microseconds to seconds [30]. It is considered as having the most duration from microseconds to seconds [30]. It is considered as having the most advanced advanceduser-defined user-defined modelling modelling capabilities andcapabilities the most numericallyand the most stable numerically time-domain stable software. time-do- mainIn lieusoftware. of the In unavailability lieu of the unavailability of data related of to data the LRT related Kelana to the Jaya LRT line, Kelana the parameters Jaya line, the parametersconsidered considered in designing in the designing user-defined the user-defined devices modelled devices for this modelled study were for adoptedthis study as were adoptedin [31] as and in as [31] exemplified and as exemplified in Figure3. in Figure 3.

Figure 3. Block diagram of the LRT Kelana Jaya system. Figure 3. Block diagram of the LRT Kelana Jaya system. 3. Results and Discussion Due to the unavailability of the lightning current parameters for the LRT Kelana Jaya line, the parameters considered in computing the I0 followed the established values from the measurements of Berger et al. with probabilities of 50% and 5% occurrence, as shown in Table1. The resultant lightning current based on the parameters in Table1 is shown in Figures4 and5, i.e., 30 kA (5/80 µs) and 90 kA (9/200 µs), respectively. Materials 2021, 14, x FOR PEER REVIEW 7 of 18 Materials 2021, 14, x FOR PEER REVIEW 7 of 18

3. Results and Discussion 3. Results and Discussion Due to the unavailability of the lightning current parameters for the LRT Kelana Jaya Due to the unavailability of the lightning current parameters for the LRT Kelana Jaya line, the parameters considered in computing the I0 followed the established values from line, the parameters considered in computing the I0 followed the established values from Materials 2021, 14, 1684 the measurements of Berger et al. with probabilities of 50% and 5% occurrence, as shown7 of 17 the measurements of Berger et al. with probabilities of 50% and 5% occurrence, as shown in Table 1. The resultant lightning current based on the parameters in Table 1 is shown in in Table 1. The resultant lightning current based on the parameters in Table 1 is shown in Figures 4 and 5, i.e., 30 kA (5/80 µs) and 90 kA (9/200 µs), respectively. Figures 4 and 5, i.e., 30 kA (5/80 µs) and 90 kA (9/200 µs), respectively. Table 1. Parameters of Heidler Function for I0 Peak. Table 1. Parameters of Heidler Function for I0 Peak. Table 1. Parameters of Heidler Function for I0 Peak. Occurrence Heidler Function Setting I0 (kA) Occurrence Heidler Function Setting I0 (kA) Occurrence Heidler Function Setting I0 (kA) %I1 (kA) τ11 (µs) τ21 (µs) n1 I0 % I1 (kA) τ11 (µs) τ21 (µs) n1 I0 % 9.075I1 (kA) 3.42τ11 (µs) 40.24τ21 (µs) n 21 I0 9.075 3.42 40.24 2 50 [32] I2 (kA) 9.075 τ12 (µs)3.42 τ22 (µs)40.24 n22 30 (5/80 µs) 50 [32] I2 (kA) τ12 (µs) τ22 (µs) n2 30 (5/80 µs) 50 [32] 20.515I2 (kA) 4.793τ12 (µs) 153.46τ22 (µs) n 102 30 (5/80 µs) 20.515 4.793 153.46 10 I1 (kA)20.515 τ11 (µs)4.793 τ21 (µs)153.46 10 n1 I1 (kA) τ11 (µs) τ21 (µs) n1 5 [32] 46.49I1 (kA) 5.86τ11 (µs) 143.997τ21 (µs) n 21 90 (9/200 µs) 5 [32] 46.49 5.86 143.997 2 90 (9/200 µs) 5 [32] I2 (kA) 46.49 τ12 (µs)5.86 τ22 (µ143.997s) n22 90 (9/200 µs) I2 (kA) τ12 (µs) τ22 (µs) n2 41.548I2 (kA) 41.759τ12 (µs) 592.86τ22 (µs) n 102 41.548 41.759 592.86 10 41.548 41.759 592.86 10

Figure 4. Lightning current 30 kA (5/80 µs) waveshape. Figure 4. Lightning current 30 kA (5/80 µs)µs) waveshape. waveshape.

Figure 5. Lightning current 90 kA (9/200 µs) waveshape. Figure 5. Lightning current 90 kA (9/200 µs)µs) waveshape. waveshape. As for the LRT Kelana Jaya line, the simulation model was based on the parameters As for the LRT KelanaKelana Jaya line,line, thethe simulationsimulation modelmodel waswas basedbased onon thethe parametersparameters depicted in Table 2. The justification of the selected Table 2 parameters is tabulated in depicted in Table2 2.. TheThe justiﬁcationjustification ofof thethe selectedselected TableTable2 2parameters parameters is is tabulated tabulated in in Table 3. Table3 3.. Table 2. The relative simulation variations.

Operating Strike Point System Insulated Arrester(Residual Velocity (v) System Height (m) I (kA) Length (m) Rail Bracket Voltage (kV)) 0 (108 m/s) Horizontal(d) Vertical (x) Voltage (V) (m) (m) CE 750 3000 17 CEA 3EB4-010 (2.4) 30 and 90 1.2 25 2000 GRP Materials 2021, 14, 1684 8 of 17

Table 3. Justiﬁcation of the parameters determination.

Parameter Value Justiﬁcation The proposed height follows the equation of span-to-height ratio of 3 as to create an aesthetical Guideway Height (m) 17 appearance. Furthermore, a higher elevation creates a more open and lighter area underneath the guideway [33]. The selected magnitude is the typical magnitude of the negative ﬁrst return stroke with 50% and 5% occurrences Current Peak (kA) 30 and 90 worldwide. The replication of the magnitude and its waveshape follows the assumption made towards the Lightning Heidler function parameters in the IEC 62305-1 [32]. The selected velocity is the commonly accepted value as it lies in between c/3 and 2c/3, the typical velocities range Velocity (×108 m/s) 1.2 of a return stroke lightning current, with c as the speed of light in free space; 2.99792458 × 108 m/s [26,34]. The short distance is considered based on the fact that the LRT Kelana Jaya line runs through the heart of Greater Kuala Lumpur, a city that housed the majority of the Malaysia government administration buildings, Horizontal (m) 25 businesses, entertainments, and leisure landmarks where Strike Distance void spaces between the guideway and the buildings are limited. In addition, 25 m is within the range of Protection Zone Law [34]; 2.5 to 80 m. The distances were selected for assessing the impact of Vertical (m) 2000 induced overvoltages on the insulated rail bracket (2000 m). The rail bracket is made from polymer-based materials, CE, Bracket Material i.e., CE, CEA, and GRP which have a different CEA, GRP permittivity value. The selected surge arrester was based on its rated voltage 3EB4-010 (1.0 kV), MCOV (1.0 kV), and most importantly based on Surge Arrester 10 kA at 8/20 µs and its residual voltage (2.4 kV) at a nominal discharge current 2.4 kV (10 kA at 8/20 µs), the arrester energy limit is 10 kJ.

Referring to Figure6, the distance is essentially limited to 2000 m as to highlight the impact of the induced effects on different bracket materials, namely the Cycloaliphatic Epoxy A (CEA) and the Glass Reinforced Plastic (GRP). The performances of these two materials were superimposed and compared with the Cast Epoxy (CE) bracket, which is currently being used in the LRT Kelana Jaya line. The induced overvoltage proﬁles for the CE, CEA, and GRP brackets are shown in Figure7. There were only four brackets needed in the rail model portraying the 3 km distance from Setiawangsa Station to Damai Station, where one bracket is installed for every 1-km distance. Materials 2021, 14, x FOR PEER REVIEW 9 of 18

Materials 2021, 14, x FOR PEER REVIEW 9 of 18

The selected surge arrester was based on its 3EB4-010 rated voltage (1.0 kV), MCOV (1.0 kV), and most 10 kA atThe selected surge arrester was based on its Surge Arrester 3EB4-010 importantly based on its residual voltage (2.4 kV) 8/20 ratedµs voltage (1.0 kV), MCOV (1.0 kV), and most 10 kA at at a nominal discharge current (10 kA at 8/20 µs), Surge Arrester and 2.4importantly kV based on its residual voltage (2.4 kV) 8/20 µs the arrester energy limit is 10 kJ. at a nominal discharge current (10 kA at 8/20 µs), and 2.4 kV Referring to Figure 6, the distance is essentthe arresterially limited energy to 2000 limit m is as 10 to kJ. highlight the impact of the induced effects on different bracket materials, namely the Cycloaliphatic ReferringEpoxy A to (CEA) Figure and 6, thethe distanceGlass Reinforced is essent Plasticially limited (GRP). to The 2000 performances m as to highlight of these the two impact materialsof the induced were superimposed effects on different and compared bracket with materials, the Cast namely Epoxy (CE)the Cycloaliphaticbracket, which is Materials 2021, 14, 1684 Epoxy Acurrently (CEA) beingand the used Glass in the Reinforced LRT Kelana Plastic Jaya line. (GRP). The performances of these two 9 of 17 materials were superimposed and compared with the Cast Epoxy (CE) bracket, which is currently being used in the LRT Kelana Jaya line.

Figure 6. Illustration of the simulation configuration.

The induced overvoltage profiles for the CE, CEA, and GRP brackets are shown in

Figure 7. There were only four brackets needed in the rail model portraying the 3 km Figure 6. Illustration of the simulation conﬁguration. Figure 6.distance Illustration from of Setiawangsathe simulation Station configuration. to Damai Station, where one bracket is installed for every 1-km distance. The induced overvoltage profiles for the CE, CEA, and GRP brackets are shown in Figure 7. There were only four brackets needed in the rail model portraying the 3 km distance from Setiawangsa Station to Damai Station, where one bracket is installed for every 1-km distance.

Materials 2021, 14, x FOR PEER REVIEW 10 of 18

(a)

(b)

(c)

(d)

Figure 7. InducedFigure 7. overvoltage Induced overvoltage waveforms waveforms on theon th insulatede insulated rail brackets, brackets, i.e., i.e.,(a) first (a) bracket, ﬁrst bracket, (b) second (b bracket,) second (c) bracket,third (c) third bracket, and (d) fourth bracket, for both 30 kA (left) and 90 kA (right). bracket, and (d) fourth bracket, for both 30 kA (left) and 90 kA (right). It was observed that the induced voltages on the brackets due to 30 kA were not much different from one another as compared with the ones caused by the 90 kA, in particular on the third bracket (Bracket #3). Figure 8 shows the magnified peak induced overvoltage, with the solid red, blue, and green lines representing the CEA, CE, and GRP materials, respectively. Whilst Figure 9 shows the corresponding magnitudes obtained based on Figure 8. Note that the solid green waveform in Figures 7 and 8c represents the superimposed waveforms for other materials and this applies to all the solid green waveform results obtained in this study. Since the impact of transient induced overvoltage has no influence on the performance of the fourth rail, further analysis of the fourth rail will not be discussed in this paper. The credible explanation that can be inferred is that the return stroke current model and the model function parameters as tabulated in Table 1 are the representation of a negative first return stroke current, hence explaining the dismissive reaction of the fourth rail towards the induced overvoltage. Figure 8 shows the distinction between the bracket material performances when imposed with 30 kA (5/80 µs) and 90 kA (9/200 µs) waveforms, where different magnitudes of the induced overvoltage were observed. Note that the CE bracket was made as the reference case when comparing its performance with the CEA and GRP brackets. For example, all the three materials show the same magnitude of induced overvoltages recorded at the third bracket, due to their close distances to the lightning strike location and consequently experienced the highest induced overvoltage of 35.62 kV, before parting ways

Materials 2021, 14, 1684 10 of 17

It was observed that the induced voltages on the brackets due to 30 kA were not much different from one another as compared with the ones caused by the 90 kA, in Materials 2021, 14, x FOR PEER REVIEWparticular on the third bracket (Bracket #3). Figure8 shows the magniﬁed peak induced11 of 18

overvoltage, with the solid red, blue, and green lines representing the CEA, CE, and GRP materials, respectively. Whilst Figure9 shows the corresponding magnitudes obtained based on Figure8. Note that the solid green waveform in Figures7 and8c represents either bound to the Setiawangsa Station or to the Damai Station. This was then followed the superimposed waveforms for other materials and this applies to all the solid green by the magnitudes recorded at the second, fourth, and first bracket. This description ap- waveform results obtained in this study. plied to both the 30 and 90 kA cases.

(a)

(b)

(c)

(d)

FigureFigure 8. MagniﬁedMagnified Figure7 7 for for aa clearerclearer view.view. ((a)) First bracket, (b)) second bracket, ((cc)) third bracket,bracket, andand ((d)) fourth bracketbracket for both 30 kA (left) and 90 kA (right). for both 30 kA (left) and 90 kA (right). Overall, when comparing the induced magnitude of CE from the 30 kA case, the GRP was recorded to have a lower induced magnitude, while the CEA recorded a higher magnitude, taken at the same brackets as shown in Figure 9, indicating the difference of 0.58% for the second bracket, 0.18% for the fourth bracket, and 0.66% for the first bracket. On the other hand, the percentage increase of induced overvoltage due to the usage of CEA material as the insulated rail bracket were 0.27%, 0.04%, and 0.3%, for the second, fourth, and first CE brackets, respectively. It would be safe to say that the recorded induced magnitudes are lower than the BIL of 46.16 kV, except for the case of 90 kA for bracket #3, which

Materials 2021, 14, x FOR PEER REVIEW 12 of 18

Materials 2021, 14, 1684 11 of 17 exceeds the BIL. The GRP material was found to perform slightly better in the case of 90 kA with almost 1–2 kV voltage differences compared to CE and CEA.

Magnitude of the Induced Overvoltage Magnitude of the Induced Overvoltage 60 50 48.12 45 46.16 48.12 48.12 35.62 50 40 35.62 35.62 46.16 35 25.99 40 30 26.06 25.84 22.76 20.21 22.77 22.72 30 19.86 25 16.71 20.96 21.14 18.12 18.67 20 16.76 16.6 20 8.78 9.58 15 10 7.52 10 (kV) Overvoltage Induced 5 0 Induced Overvoltage (kV) Overvoltage Induced #1 #2 #3 #4 0 #1 #2 #3 #4 Brackets sequences Brackets sequences CEA CE GRP BIL(wet) CEA CE GRP BIL(wet)

FigureFigure 9. 9.Induced Induced overvoltage overvoltage magnitude magnitude on on the the insulated insulated rail rail brackets brackets for for both both 30 30 kA kA (left (left) and) and 90 90 kA kA (right (right). ).

SinceOn another the impact perspective, of transient GRP induced has the overvoltage highest reduction has no influence with 53.4%, on the followed performance by CE ofwith the fourth53.09% rail, and further CEA at analysis 52.95% when of the comparing fourth rail willwith not the be BIL discussed in the case in thisof 30 paper. kA. Whilst The crediblefor the 90 explanation kA case, the that GRP can bracket be inferred shows is th thate highest the return reduction stroke with current 84.37%, model followed and the by modelCE with function 81.75% parameters and CEA asat tabulated80.09%. This in Table is acknowledged1 are the representation by the fact of that a negative GRP has first the returnhighest stroke permittivity current, constant hence explaining among these the dismissivethree materials reaction and ofthus, the provides fourth rail an towards excellent theelectric induced stress overvoltage. controller, which is capable of reducing the stress to an acceptable desired valueFigure [35,36].8 shows the distinction between the bracket material performances when imposedFigure with 10 30 shows kA (5/80 the residualµs) and voltages 90 kA (9/200recordedµs) by waveforms, the station surge where arresters different for mag- both nitudescases. It of was the observed induced that overvoltage the waveshapes were observed. of the arrester Note residual that the CEvoltages bracket were was not made much asdifferent the reference from the case reference when comparing case. As described its performance in Figure with 6, thethe CEAlightning and GRPorigin brackets. location Forwas example, much closer all the to three the Damai materials Station show and the thus, same explained magnitude the of higher induced clamped overvoltages voltage recordedmagnitude at the at that third station bracket, arrester due to (Figure their close 10b). distances Nonetheless, to the the lightning high voltage strike location current andman- consequentlyaged to be redirected experienced to the the ground highest within induced 40.1 overvoltage µs, diminishing of 35.62 nearly kV, before 11% from parting the ways initial eithervoltage bound magnitude to the Setiawangsa as analyzed Station through or toFigure the Damai 10b for Station. the 30 ThiskA case. was thenTo be followed precise, bythe the magnitudes recorded at the second, fourth, and first bracket. This description applied GRP bracket was able to redirect its high voltage current into 40.2 µs, diminishing 11.06% to both the 30 and 90 kA cases. from its initial voltage. Similarly for the case of the CEA bracket where the same time lapse Overall, when comparing the induced magnitude of CE from the 30 kA case, the as per the GRP was obtained but only to diminish 0.05% more of the residual voltage than GRP was recorded to have a lower induced magnitude, while the CEA recorded a higher the reference case. However, in the case of 90 kA, the maximum peak has reached within magnitude, taken at the same brackets as shown in Figure9, indicating the difference of 11.8 µs, regardless of the bracket-type materials, before receding to a lower magnitude of 0.58% for the second bracket, 0.18% for the fourth bracket, and 0.66% for the first bracket. 0.3 µs later. On the other hand, the percentage increase of induced overvoltage due to the usage of CEA material as the insulated rail bracket were 0.27%, 0.04%, and 0.3%, for the second, fourth, and first CE brackets, respectively. It would be safe to say that the recorded induced magnitudes are lower than the BIL of 46.16 kV, except for the case of 90 kA for bracket #3, which exceeds the BIL. The GRP material was found to perform slightly better in the case of 90 kA with almost 1–2 kV voltage differences compared to CE and CEA. On another perspective, GRP has the highest reduction with 53.4%, followed by CE with 53.09% and CEA at 52.95% when comparing with the BIL in the case of 30 kA. Whilst for the 90 kA case, the GRP bracket shows the highest reduction with 84.37%, followed by CE with 81.75% and CEA at 80.09%. This is acknowledged by the fact that GRP has the highest permittivity constant among these three materials and thus, provides an excellent electric stress controller, which is capable of reducing the stress to an acceptable desired value [35,36]. Figure 10 shows the residual voltages recorded by the station surge arresters for both

cases. It was observed that the waveshapes of the arrester residual voltages were not much different from the reference case.(a) As described in Figure6, the lightning origin location was much closer to the Damai Station and thus, explained the higher clamped voltage magnitude at that station arrester (Figure 10b). Nonetheless, the high voltage current

Materials 2021, 14, x FOR PEER REVIEW 12 of 18

exceeds the BIL. The GRP material was found to perform slightly better in the case of 90 kA with almost 1–2 kV voltage differences compared to CE and CEA.

Figure 9. Induced overvoltage magnitude on the insulated rail brackets for both 30 kA (left) and 90 kA (right).

On another perspective, GRP has the highest reduction with 53.4%, followed by CE with 53.09% and CEA at 52.95% when comparing with the BIL in the case of 30 kA. Whilst for the 90 kA case, the GRP bracket shows the highest reduction with 84.37%, followed by CE with 81.75% and CEA at 80.09%. This is acknowledged by the fact that GRP has the highest permittivity constant among these three materials and thus, provides an excellent electric stress controller, which is capable of reducing the stress to an acceptable desired value [35,36]. Figure 10 shows the residual voltages recorded by the station surge arresters for both Materials 2021, 14, 1684 cases. It was observed that the waveshapes of the arrester residual voltages were not much12 of 17 different from the reference case. As described in Figure 6, the lightning origin location was much closer to the Damai Station and thus, explained the higher clamped voltage magnitude at that station arrester (Figure 10b). Nonetheless, the high voltage current man- agedmanaged to be toredirected be redirected to the toground the ground within within 40.1 µs, 40.1 diminishingµs, diminishing nearly nearly11% from 11% the from initial the voltageinitial voltage magnitude magnitude as analyzed as analyzed through through Figure Figure 10b for 10 theb for 30 the kA 30 case. kA case.To be To precise, be precise, the GRPthe GRPbracket bracket was able was to able redirect to redirect its high its voltage high voltage current current into 40.2 into µs, 40.2diminishingµs, diminishing 11.06% from11.06% its initial from its voltage. initial Similarly voltage. Similarlyfor the case for of the the case CEA of bracket the CEA where bracket the same where time the lapse same astime per lapsethe GRP as per was the obtained GRP was but obtained only to diminish but only 0.05% to diminish more of 0.05% the residual more of voltage the residual than thevoltage reference than case. the reference However, case. in the However, case of 90 in kA, the the case maximum of 90 kA, peak the maximumhas reached peak within has 11.8reached µs, regardless within 11.8 ofµ thes, regardless bracket-type of the materi bracket-typeals, before materials, receding before to a lower receding magnitude to a lower of 0.3magnitude µs later. of 0.3 µs later.

Materials 2021, 14, x FOR PEER REVIEW 13 of 18

(a)

(b)

FigureFigure 10.10.Residual Residual voltage voltage waveforms waveforms of of the the (a )(a Setiawangsa) Setiawangsa Station Station and and (b )( Damaib) Damai Station Station surge surge arresters arresters for bothfor both 30 kA 30 (leftkA )(left and) 90and kA 90 ( rightkA (right). ).

ReferringReferring toto FigureFigure 1111b,b, thethe GRPGRP bracketbracket recordedrecorded thethe lowestlowest initialinitial magnitudemagnitude atat 1683.221683.22 V, V, which which is is 0.43% 0.43% lower lower from from the the CE CE bracket. bracket. The The arrester arrester also also managed managed to diminishto dimin- µ 10%ish 10% of its of initial its initial residual residual voltage voltage to the to ground the ground within within 0.3 s,0.3 which µs, which is similar is similar to the to CEA the bracket.CEA bracket. Having Having the station the station surge arrestersurge arrester installed installed at the Setiawangsa at the Setiawangsa Station hasStation helped has easehelped the ease high the energy high causedenergy bycaused the 30 by and the 9030 kAand lightning 90 kA lightning surge current, surge current, which can which be seen in Figure 10a. can be seen in Figure 10a.

Magnitude of the Residual Voltage Magnitude of the Residual Voltage 1750 1750 1691.51 1692.06 1690.31 1690.48 1694.52 1683.22 1700 1700 1650 1650 1600 1600 1539.88 1520.07 1550 1503.19 1502.81 1503.39 1550 1514.11 1500 1500 1450 1450 Residual Voltgae (V) Residual Voltage (V) 1400 1400 CE CEA GRP CE CEA GRP Residual Voltage Residual Voltage Residual Voltage Residual Voltage Residual Voltage Residual Voltage (V) (V) (V) (V) (V) (V)

Damai Station Damai Station Initial Final Initial Final

(a)

Materials 2021, 14, x FOR PEER REVIEW 13 of 18

(b) Figure 10. Residual voltage waveforms of the (a) Setiawangsa Station and (b) Damai Station surge arresters for both 30 kA (left) and 90 kA (right).

Referring to Figure 11b, the GRP bracket recorded the lowest initial magnitude at 1683.22 V, which is 0.43% lower from the CE bracket. The arrester also managed to diminish 10% of its initial residual voltage to the ground within 0.3 µs, which is similar to the Materials 2021, 14, 1684 CEA bracket. Having the station surge arrester installed at the Setiawangsa Station has13 of 17 helped ease the high energy caused by the 30 and 90 kA lightning surge current, which can be seen in Figure 10a.

Materials 2021, 14, x FOR PEER REVIEWDamai Station Damai Station 14 of 18

Initial Final Initial Final

(a) Magnitude of the Residual Voltage Magnitude of the Residual Voltage 1631.49 1700 1671.35 1671.94 1669.83 1650 1600.83 1586.71 1650 1600 1600 1550 1500.48 1488.19 1550 1500 1504.65 1504.23 1505.34 1463.04 1500 1450 1450 1400 Residual Voltage (V) Residual voltage (V) Residual voltage 1400 1350 CE CEA GRP CE CEA GRP Residual Voltage Residual Voltage Residual Voltage Residual Voltage Residual Voltage Residual Voltage (V) (V) (V) (V) (V) (V)

Setiawangsa Station Setiawangsa Station Initial Final Initial Final

(b)

FigureFigure 11. 11.Residual Residual voltage voltage magnitudes magnitudes of of the the (a ()a) Setiawangsa Setiawangsa Station Station and and ( b(b)) DamaiDamai StationStation surgesurge arrestersarresters forfor both 30 kA kA (left) and 90 kA (right). (left) and 90 kA (right). AlthoughAlthough there is no no significant significant difference difference recorded recorded for for the the case case of 30 of 30kA, kA, a slightly a slightly improvedimproved performanceperformance can can be be observed observed in in the the case case of of 90 90 kA. kA. The The reduction reduction of the of theinitial initial residualresidual voltagesvoltages between the the two two stations stations was was 5.3% 5.3% for for the the CE CE bracket, bracket, with with the themost most reductionreduction obtained obtained forfor thethe GRPGRP bracketbracket atat 5.73%.5.73%. Figure 11a11a shows the the induced induced overvolt- overvoltage clampedage clamped by the by arrester the arrester at a lower at a lower magnitude, magnitude, which which signified signified the quick the quick speed-of-response speed-of- ofresponse the arrester of the as opposedarrester as to opposed when the to arrester when clampedthe arrester a little clamped later, whicha little wouldlater, which make the arresterwould make clamp the at aarrester higher magnitudeclamp at a higher and thus, magnitude jeopardize and the thus, downstream jeopardize equipment the down- [37]. streamAlthough equipment no significant[37]. differences were observed for the case of 30 kA, the GRP bracketAlthough has recorded no significant a lower clampingdifferences voltage were observed and therefore for the it iscase reasonable of 30 kA, to the say GRP that its thermalbracket energyhas recorded absorption a lower was clamping lower among voltage the and three therefore materials, it is reasonable as discussed to say earlier that and shownits thermal in Figures energy 12 absorption and 13. Having was lower said amon that,g itthe is notthree to materials, judge the as arrester discussed performance earlier basedand shown on the in low Figures thermal 12 and energy, 13. Having instead said it is that, just it to is show not to that judge a comparison the arrester wasperfor- made betweenmance based the computed on the low energy thermal absorption energy, instead and the it arrester’s is just to show own thermal that a comparison energy absorption was limit.made Anbetween excellent the computed example wasenergy in absorption the case of and 90 kA,the arrester’s depicted own in Figure thermal 12 energy(with the magnifiedabsorption versionlimit. An as excellent in Figure example 13) where was for in the Setiawangsacase of 90 kA, Station depicted arrester, in Figure the 12 GRP bracket(with the contributed magnified theversion lowest as in energy Figure absorption 13) where offor 7.28 the kJ,Setiawangsa followed Station by CE witharrester, 8.67 kJ andthe GRP CEA bracket at 9.71 contributed kJ. Whilst for thethe lowest Damai energy Station absorption arrester, of 7.28 the GRPkJ, followed bracket by recorded CE with the lowest8.67 kJ energyand CEA absorption, at 9.71 kJ. Whilst with 115% for the more Damai than Station the limit arrester, allowed, the GRP i.e., bracket 10 kJ, compared recorded to the lowest energy absorption, with 115% more than the limit allowed, i.e., 10 kJ, compared 135.4% from the CE bracket and 147.8% from the CEA bracket, as shown in Figure 14. to 135.4% from the CE bracket and 147.8% from the CEA bracket, as shown in Figure 14. Should the energy handling capacity of the line arrester be exceeded, this would eventually lead to an internal arc and equipment breakdown. In the case of 90 kA, the high energies were dissipated within less than 1 µs and if they were able to remain cool against the system’s continuous operating voltage, then it is said to be able to thermally withstand the high energy.

Materials 2021, 14, 1684 14 of 17 MaterialsMaterials 20212021,, 1414,, xx FORFOR PEERPEER REVIEWREVIEW 1515 ofof 1818

((aa))

((bb)) Figure 12. Energy absorption waveforms of the (a) Setiawangsa Station and (b) Damai Station surge arresters for both 30 FigureFigure 12. Energy 12. Energy absorption absorption waveforms waveforms of theof the (a )(a Setiawangsa) Setiawangsa Station Station andand (b) Damai Station Station surge surge arresters arresters for for both both 30 30 kA kAkA ((leftleft)) andand 9090 kAkA ((rightright).). (left) and 90 kA (right).

((aa))

((bb))

Figure 13. Magniﬁed version of Figure 10.(a) Setiawangsa Station and (b) Damai Station surge arresters for both 30 kA (left ) and 90 kA (right). Materials 2021, 14, x FOR PEER REVIEW 16 of 18

Figure 13. Magnified version of Figure 10. (a) Setiawangsa Station and (b) Damai Station surge arresters for both 30 kA (left) and 90 kA (right).

Thus, by referring to Figure 14, it can be understood that the arrester of the Damai Station absorbed more energy as compared to the arrester at the Setiawangsa Station, considering the lightning strike point is much closer to the Damai Station. The GRP bracket was found to coordinate better with the station arrester, where it absorbed more than the limit permitted, i.e., 10 kJ, with 87.6% more at the Setiawangsa Station and 168.4% more Materials 2021, 14, 1684 15 of 17 at the Damai Station for the case of 30 kA.

Thermal Energy Absorption Comparison Thermal Energy Absorption Comparison 30 30 26.89 26.91 26.84 24.78 25 25 23.54 21.5 18.98 20 18.91 18.76 20

15 15 9.71 8.69 10 10 7.28 Energy Absorption (kJ) Absorption Energy Energy Absorption (kJ) Absorption Energy 5 5

0 0 Computed SA - CE Computed SA - Computed SA - Computed SA - CE Computed SA - Computed SA - CEA GRP CEA GRP

Setiawangsa Station Damai Station Setiawangsa Station Damai Station

Figure 14. Comparison of the arrester thermal energy absorption between the computed bracket material cases for both Figure30 kA (14.left Comparison) and 90 kA (ofright the). arrester thermal energy absorption between the computed bracket material cases for both 30 kA (left) and 90 kA (right). Should the energy handling capacity of the line arrester be exceeded, this would eventuallyThe better lead energy to an internal absorption arc and of equipmentGRP as compared breakdown. to others In the has case provided of 90 kA, a the better high marginenergies of were protection dissipated for the within 12-pulse less thanrectifier 1 µs circuit. and if theyThe weremargin able of toprotection remain cool of the against rec- tifierthe system’s was calculated continuous by operatingthe expression voltage, of thenUpl, 10 itis kA, said 8/20 to be µs able < BIL tothermally (device to withstand be protected)/1.4,the high energy. considering the BIL of the 12-pulse rectifier is 3600 V [38]. This has resulted in 2.5 kV,Thus, which by puts referring the arrester to Figure residual 14, it voltag can bee understood barely less than that the margin arrester of of the the protec- Damai tionStation voltage. absorbed Rest assured, more energy the arresters as compared may still to work the arrester reliably atand the safely Setiawangsa even though Station, the energyconsidering absorption the lightning exceeded strike their point standard is much allowable closer to limit, the Damai given Station. that the The arresters GRP bracket have thewas time found to cool to coordinate down. The better necessary with the cool-d stationown arrester, time for where the arresters it absorbed depends more on than their the construction,limit permitted, the i.e.,ambient 10 kJ, temperature, with 87.6% more and atth thee applied Setiawangsa voltage. Station However, and 168.4% normally more the at cool-downthe Damai time Station typically for the lies case between of 30 kA. 45 and 60 min [39]. It is also worth noting that the changesThe and better variations energy in absorption results could of GRP be significant as compared when to a others higher has magnitude provided of a light- better ningmargin stroke of protection (with different for the waveshapes) 12-pulse rectifier is inje circuit.cted on The the margin system, of protectionand in this of case, the rectifier it was µ thewas 90 calculated kA (9/200 by µs). the expression of Upl, 10 kA, 8/20 s < BIL (device to be protected)/1.4, consideringIn short, the all BILthese of analyses the 12-pulse with rectifier 30 kA (5/8 is 36000 µs) V and [38]. 90 This kA has(9/200 resulted µs) lightning in 2.5 kV, current which puts the arrester residual voltage barely less than the margin of the protection voltage. Rest on the LRT Kelana Jaya line have demonstrated the effect of insulation coordination be- assured, the arresters may still work reliably and safely even though the energy absorption tween the CE, CEA, and GRP brackets with the station arrester. exceeded their standard allowable limit, given that the arresters have the time to cool down. 4.The Conclusions necessary cool-down time for the arresters depends on their construction, the ambient temperature, and the applied voltage. However, normally the cool-down time typically lies betweenThis study 45 has and provided 60 min [39 a useful]. It is alsoinsight worth obtained noting through that the the changes simulation and variations carried out in onresults the performances could be significant of the in whensulated a higherrail brackets magnitude and the of station lightning surge stroke arresters (with subjected different towaveshapes) an indirect lightning is injected stroke on the nearby. system, The and lightning in this case, current it was was the modelled 90 kA (9/200 by theµs). sum of two HeidlerIn short, functions all these representing analyses with the 30current kA (5/80 at theµ s)channel and 90 base kA and (9/200 the µlightnings) lightning in- ducedcurrent overvoltage on the LRT was Kelana modelled Jaya line using have the demonstrated Rusck equation. the effect of insulation coordination between the CE, CEA, and GRP brackets with the station arrester.

4. Conclusions This study has provided a useful insight obtained through the simulation carried out on the performances of the insulated rail brackets and the station surge arresters subjected to an indirect lightning stroke nearby. The lightning current was modelled by the sum of two Heidler functions representing the current at the channel base and the lightning induced overvoltage was modelled using the Rusck equation. It is perhaps premature to conclude which type of rail bracket is superior when only a single stroke of 30 kA (5/80 µs) is considered. As such, results from the 90 kA (9/200 µs) Materials 2021, 14, 1684 16 of 17

were also included to support and highlight the influence of the bracket material. The preliminary analyses came to a conclusion that the escalation of the magnitude of the lightning induced overvoltage on the brackets was influenced by the bracket materials, which depends on the properties of the material itself, i.e., permittivity. A material with better permittivity such as the GRP material is known to be an excellent electric stress controller and hence, capable of reducing the stress to an acceptable desired value. Therefore, it results in better insulation coordination with the station surge arrester in terms of residual voltage and energy absorption capacity of the station arrester. In short, these simulations were carried out to ensure the reliable operation of the fourth rail transit. Considering that Malaysia is known for having one of the highest lightning flash densities in the world, this work is considered to be critical to the railway operator and owner. Moreover, it is worth noting that these findings were based on the initial lightning current injected onto the system, i.e., 30 kA (5/80 µs) and 90 kA (9/200 µs) and therefore, the results would likely be different should other lightning currents with different magnitudes and waveshapes be considered.

Author Contributions: Conceptualization, M.Z.A.A.K., U.A.U.A., and M.O.; methodology, F.A.A.R.; validation M.Z.A.A.K.; formal analysis, F.A.A.R.; investigation, F.A.A.R.; writing—original draft preparation, F.A.A.R.; writing—review and editing, F.A.A.R.; supervision M.Z.A.A.K., U.A.U.A., and M.O.; project administration, M.Z.A.A.K., U.A.U.A., and M.O.; funding acquisition, M.Z.A.A.K., U.A.U.A., and M.O. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Universiti Tenaga Nasional through UNITEN Bold Postgraduates Strategic Hires Grant. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: The authors thank the Strategic Hired Research team Institute of Power Engi- neering (IPE) for their support either academically or professionally in this work. Conﬂicts of Interest: The authors declare no conﬂict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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