Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4, 290-308 2024 Publisher: Learning Gate DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate © 2024 by the authors; licensee Learning Gate History: Received: 26 January 2024; Revised: 22 March 2024; Accepted: 8 April 2024; Published: 17 May 2024 * Correspondence: agustinoalhakim@gmail.com An analysis of circuit breaker capacity according to IEC 60909 and IEC 60059 standards at the PT Borneo Alumina Indonesia electrical system Agustino Al Hakim1*, Rudy Gianto1, Purwoharjono1, Rudi Kurnianto1, Ismail Yusuf1 1Faculty of Engineering, Universitas Tanjungpura, Pontianak, Indonesia; agustinoalhakim@gmail.com (A.A.H.); rudy.gianto@ee.untan.ac.id (R.G.); purwo.harjono@ee.untan.ac.id (P.); rudi.kurnianto@ee.untan.ac.id (R.K.); ismail.yusuf@ee.untan.ac.id (I.Y.). Abstract: At PT Borneo Alumina Indonesia (PT BAI), the D01 Power Distribution System uses circuit breakers (CB) with a current rating capacity of 1250A for both incoming and outgoing 10kV busbars. Replacing outgoing CBs with the same capacity during maintenance leads to unnecessary waste. This study was conducted to examine the appropriate CB capacity as a substitute for the old CBs in the outgoing 10 kV busbars for loads of 10 kV induction motors and transformers so that recommendations can be made to improve efficiency during maintenance on the D01 Power Distribution System. The Electronic Transient Analyzer Program (ETAP) 19.0.1 software was used to perform short circuit simulations based on IEC 60909 and load flow simulations, which were then adjusted to IEC 60059 and CB products from Siemens. The results show that we can replace the current Siemens CB, which has a rated breaking current specification of 31.5kA, with 25kA during the maintenance period. We can also replace the rated peak value of 80kA with 63kA, and the rated current of 1250A with 630A. Replacement of CB specifications does not change/modify the switchgear panel because the replacement CB matches the brand, dimensions, and size of the currently installed CB. These findings would also help increase efficiency during maintenance on the D01 Power Distribution System. The discussion includes limitations and recommendations for future research. Keywords: Circuit breaker, ETAP 19.0.1, IEC 60909, IEC 60059, Peak value, Rated breaking current, Rated current, Siemens, Switchgear. 1. Introduction PT BAI's bauxite processing industry is powered by electricity . Interruptions or power outages can reduce alumina production, making it hard to meet targets and causing financial losses. A reliable electrical system is crucial for alumina production. PT BAI operates a 3x25 Mega Watt (MW) steam power plant for self-use and supplies power to the alumina and coal gasification plants at 10kV. Within this system, CB ensures equipment safety by managing excess currents and short circuits. At PT BAI, the D01 Power Distribution System for the alumina plant's medium-voltage network uses a 1250A CB on the incoming bus bar from the main 10 kV power distribution. However, the CB on the outgoing bus bars for 10kV induction motors and transformers also has the same 1250A capacity. If, during future maintenance, the outgoing bus bar CB needs replacement with a similar 1250A capacity CB for induction motors and transformers, it will result in waste. An evaluation is required to select the appropriate CB for these loads, enhancing maintenance efficiency in the D01 Power Distribution System's medium-voltage network at PT BAI. As per Kong and Nian [1] their study explores methods to select CB and fault current limiter (FCL) capacities for a reliable and cost-effective configuration in a mesh-type DC microgrid. They optimize CB breaking time, CB nominal breaking current, and FCL inductance. They use the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to quickly configure CB and FCL mailto:agustinoalhakim@gmail.com mailto:rudy.gianto@ee.untan.ac.id mailto:purwo.harjono@ee.untan.ac.id mailto:rudi.kurnianto@ee.untan.ac.id mailto:ismail.yusuf@ee.untan.ac.id 291 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate capacities. The case study on a six-terminal DC microgrid confirms the method's accuracy in determining post-fault line currents and making cost-effective CB and FCL capacity choices. In Gugale and Palazzo [2] the research aimed to accurately calculate short-circuit current disturbances for sizing generator circuit breakers (GCBs), using standards IEC 60909, IEEE C37.010, and IEC/IEEE 62271-37-013. Two key factors were computed: generator source short-circuit current and out-of-phase current disturbances. The ATP-EMTP software was used for simulations, concluding that the IEC/IEEE 62271-37-013 standard is recommended for precise GCB design and selection. In Khattijit, et al. [3] the research evaluated and analyzed short-circuit faults in renewable energy- based (solar) electrical distribution networks. It used IEC 60909 calculations and IEEE 242 design standards for relay protection. ETAP software simulates short-circuit faults for optimal network design and reliable protection using relay systems. The findings highlighted that increased power from renewables could lead to higher short-circuit currents. Closed-loop configurations were more prone to faults than open-loop ones. The design should ensure power elements (Switchgear and CBs) can handle short-circuits under all conditions. Relay protection settings must be coordinated to safeguard the network effectively, activating backup protection if primary relays fail. According to Makani and Daniel Chowdhury [4] their study focused on designing a stable electrical system for the Transnet Pipeline Terminal 2 (TM2) petroleum refinery in Heidelberg. They considered a variety of factors, including load lists, reliable protection, proper cable sizing, and equipment selection in hazardous areas. They used ETAP software for power flow studies, short-circuit analysis, and motor starting simulations. The study resulted in a well-designed electrical system that accounted for normal, emergency, and vital loads, ensured protection and efficiency, and included capacitor banks to improve power factor. In Pramudya, et al. [5] a study focused on modeling methods for selecting the right high- voltage AC circuit breaker capacity in circuits with varying voltage levels and capacities for commercial purposes. They used the Schwarz Black Box arc model (Schwarz-BB) for modeling and compared its performance to real CBs during fault events. The results showed a close match between actual and simulated conditions, indicating an accurate CB model. This modeling can be employed to analyze suitable circuit breaker choices in specific electrical circuits. The research aimed to determine the appropriate capacity of CBs by using IEC 60909 and aligning it with IEC 60059 standards and Siemens CB products. This would improve maintenance efficiency at PT BAI. 2. Theoretical Basis 2.1. Short-Circuit Simulation with ETAP As per Prabhu, et al. [6] calculating short-circuit currents is vital for system analysis, given the inevitability of short-circuit incidents in electrical systems. It guarantees that the system's selected electrical equipment can manage the potential maximum short-circuit currents. Short-circuit calculations (SCC) determine both maximum and minimum fault currents. Maximum short-circuit currents help size electrical equipment withstand capacity, especially for Line to Ground (LG) faults used in grounding system design. Minimum short-circuit currents are used to guide instantaneous overcurrent relay settings. ETAP software streamlines short-circuit simulations, significantly reducing calculation time in large electrical systems. ETAP's accuracy relies on precise input data. In ETAP, accurately modeling the electrical system is critical for calculating maximum short-circuit currents. This involves creating the appropriate configuration. For short-circuit calculations, common electrical equipment parameters used in ETAP modeling include: 2.1.1. Grid Input Source impedance and network voltage values are necessary for short-circuit current calculations [7]. Network voltage values, three-phase short-circuit apparent power, and the X/R ratio are required for modeling the electrical network using ETAP. This information is extracted from the detailed engineering design documents [8, 9]. 292 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 2.1.2. Transformer Data Input Operating voltage, apparent power, positive and zero sequence impedances (in %) with X/R ratio, vector group, and grounding system type values are needed for modeling transformers in ETAP. 2.1.3. Motor Data Input To model motors in ETAP, essential input parameters include motor power values, operating voltage values, power factor, efficiency, Locked Rotor Current (LRC), and starting power factor. The motor power value is contingent upon the load connected to the motor. It is recommended to assume LRC to be between 600% to 700%. 2.1.4. Busbar Data Input The nominal busbar voltage stands as a crucial input for short-circuit current calculations. ETAP generates short-circuit currents based on the nominal busbar voltage. In projects adhering to IEC standards, the busbar voltage differs from the transformer secondary voltage. ETAP treats the busbar voltage (connected to the secondary transformer) as equivalent to the transformer secondary voltage. Thus, providing an accurate nominal busbar voltage is imperative. Short circuit calculations (SCC) can be performed in ETAP by clicking the "Run LG, LL, and LLG 3-phase Faults" icon. ETAP calculates the initial symmetrical RMS current (I"k), steady-state RMS current (Ik), peak short-circuit current (ip), and the angle between current and voltage for 3-phase faults, Line to Ground (LG) faults, Line to Line (LL) faults, and Line to Line to Ground (LLG) faults. ETAP's output report displays the SCC results. To perform maximum short-circuit current calculations, select the specific case study and model the configuration status for maximum fault current, following the detailed engineering design documents [8, 9]. 2.2. Circuit Breaker (CB) A CB, as per International Electrotechnical Vocabulary 441-14-20, is a mechanical switch that can close, carry, and interrupt current flow under normal and abnormal conditions, including short-circuit faults. It functions as a switch for electrical networks under load and can open or close in response to current faults (short circuits) in the network or electrical equipment [10]. Continuous Rated Current is the maximum current allowed to flow continuously through a CB. Pick-up current is the minimum current that activates a protection relay, typically ranging from 1.05 to 1.5 times its current settings, according to British Standard [11]. The CB's breaking capacity is defined as its ability to withstand short-circuit fault currents without damaging the breaker or connected electrical equipment. The balanced three-phase short-circuit current, determines its capacity [12]. 2.3. IEC Standard Current Rating The standard current values are based on IEC 60059 (IEC Standard Current Ratings) [13]. Electrical system design must apply this standard, which specifies the standard current values for electrical equipment. For any type of equipment, the standard current values should be selected from among the following options Table 1: Table 1. Standard current ratings. Standard current ratings A 1 1,25 1,6 2 2,5 3,15 4 5 6,3 8 10 12,5 16 20 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 25000 31500 40000 50000 63000 80000 100000 125000 160000 200000 - - - - - - Source: International Standard [13]. 293 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate The choice of values to be used should be considered in each case based on their purpose, and it may be found that there are good reasons to select values such as 1.5 - 3 - 6 - 7.5 rather than choosing 1.6 - 3.15 - 6.3 - 8, and their multiples of 10n (where n is a positive integer) [13]. 2.4. Power Flow Analysis with ETAP In ETAP, all electrical equipment is represented in a single line diagram (SLD). This equipment requires specific input values for power flow calculations. ETAP identifies buses connected to loads as load buses and those connected to power sources as swing buses. Transformers, generators, and bus switchgear operate within their rated capacity. Parameters such as voltage, current, and power should not exceed the rated capacity. Power flow analysis helps determine the ratings of transformers, generators, and busbar switchgear [6]. 3. Research Methodology 3.1. Research Location The research was conducted at PT Borneo Alumina Indonesia, located at Jl. Poros Bukit Batu, RT. 009/RW. 003, Dusun. Kembang Lada, Desa Bukit Batu, Kec. Sungai Kunyit, Mempawah district, West Kalimantan, Indonesia, 78971. 3.2. Tools A laptop was used for writing scientific papers and running ETAP 19.0.1 simulations. ETAP 19.0.1 software was used to create circuit simulations according to the single line diagram. 3.3. Research Materials Detailed engineering design documents obtained from PT BAI were used as references for simulations in modelling the system with ETAP 19.0.1. 3.4. Research Variables In this study, the 10kV induction motor and transformer loads at the D01 Power Distribution System's incoming 10kV busbar were looked at, along with the CB capacity, both when the system is working normally and when there is a fault. 3.5. Research Plan 3.5.1. Literature Review This research will start by gathering as many references as possible from books, journals, previous studies, and literature reviews. These references will serve as guidelines to support the theoretical framework used to address the research problem. 3.5.2. Data Collection In this study, we will collect data by getting a single line diagram of the 10 kV medium-voltage D01 Power Distribution System, three-phase short-circuit current data for the 10 kV main bus, data on the capacity and reactance of the power transformer, data on the length and impedance of the cables, and data on the installed capacity. 3.5.3. ETAP 19.0.1 System Modelling Using ETAP 19.0.1 and the data available from PT BAI, we will simulate the SLD of the electrical system based on the IEC 60909 standard. 3.5.4. Analysis of ETAP Simulation Results The results of the ETAP simulation will be analysed in accordance with IEC 60059 standards and Siemens circuit breaker products. 294 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 3.6. Research Procedure The following flowchart illustrates the research procedure: Figure 1 illustrates the research flowchart. Figure 1. Research flowchart. According to the research flowchart: 1. Begin with a literature review. 2. Collect the necessary data. 3. ETAP 19.0.1 allows you to design and input data into the SLD. 4. To obtain results, perform simulations with ETAP 19.0.1. 5. Analyzing ETAP 19.0.1 simulation results based on IEC 60909, IEC 60059, and Siemens CB products. 295 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 4. Results and Discussion 4.1. System Data The collected data consists of component information within the SLD D01 based on the documents "Single Line Diagram Power Distribution System of Alumina Plant (D01 Power Distribution System)," "Electrical Calculation Report," and "Solitary Network System Steady-state & Transient Calculation and Analysis Report (Part I: Steady-state Analysis Report)" [8, 9, 14]. The single-line diagram of the system is shown in Figure 2. Figure 2. Single line diagram of D01. Source: Chao [9]. As for the system data, it can be observed in Table 2 to Table 3: 296 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Table 2. Current limiting reactor as follows. No ID CLR Rated current Z X/R Phase Rated voltage 1 D01 CLR A 800A 0.577Ω 61 3 10kV 2 D01 CLR B 800A 0.577Ω 61 3 10kV Table 3. Motor induction. No ID motor V Rated FLA PF (%) EFF (%) 1 2#WCP 10kV 400kW 31A 80 93 2 1#WCP 10kV 400kW 31A 80 93 3 Standby WCP 10kV 400kW 28.9A 80 100 4 5#WUP A 10kV 355kW 27.5A 80 93 5 5#WCP 10kV 400kW 31A 80 93 6 4#WCP 10kV 400kW 31A 80 93 7 3#WCP 10kV 400kW 31A 80 93 8 5#WUP B 10kV 355kW 27.5A 80 93 9 BALL MILL A 10kV 3800kW 277.5A 85 93 10 BALL MILL B 10kV 3800kW 277.5A 85 93 Note: Source: FLA = Full load ampere; PF = Power factor; EFF = Efficiency; WCP = Washer circulation pump; WUP = Washer underflow pump. Xun and Wanya [8]. The weight coefficient of the lumped load is considered to be 80% for the motor load and 20% for the static load Jian, et al. [14]. Table 4 Presents system data of lumped load. Table 4. Lumped load. ID Lumped load Rated kVA Rated kVA PF (%) Motor load (%) Static load (%) D01-2E01-3101-01 250 0.380 80 80 20 D01-2E01-3101-02 250 0.380 80 80 20 D01-2P16-3101-01 1000 0.380 80 80 20 D01-2P16-3101-02 1000 0.380 80 80 20 D01-2P16-3106-01 1000 0.380 80 80 20 D01-2P16-3106-02 1000 0.380 80 80 20 D01-2P16-3108-01 625 0.380 80 80 20 D01-2P16-3108-02 625 0.380 80 80 20 D01-2T08-31-01 800 0.380 80 80 20 D01-2T08-31-02 800 0.380 80 80 20 Note: Source: PF = Power factor. Xun and Wanya [8] and Jian, et al. [14]. Table 5 Presents system data of capacitor. Table 5. Capacitor. Capacitor ID Rated capacity (kvar) Power factor Rated current (A) SVC D01A 1000 0.85 57.74 SVC D01B 1000 0.85 57.74 Source: Jian, et al. [14]. Note: Source: X = Reactance; R = Resistance; Z = Impedance. Xun and Wanya [8]. 297 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Table 6 presents system data of distribution transformer. Table 6. Distribution transformer. Transformer ID Cap. (kVA) Group con. Rated voltage (kV) Rated current (A) Z (%) Prim Sec Prim Sec TR.2P16-3101-PT-0001 2000 Dyn11 10 0.4 110 2886.8 6.25 TR.2T08-31-PT-0001 1600 Dyn11 10 0.4 88 2309.4 6.25 TR.2E01-3101-PT-0001 500 Dyn11 10 0.4 27.5 721.7 4 TR.2P16-3108-PT-0001 1250 Dyn11 10 0.4 68.7 1804.2 5 TR.2P16-3106-PT-0001 2000 Dyn11 10 0.4 110 2886.8 6.25 TR.2P16-3101-PT-0002 2000 Dyn11 10 0.4 110 2886.8 6.25 TR.2T08-31-PT-0002 1600 Dyn11 10 0.4 88 2309.4 6.25 TR.2E01-3101-PT-0002 500 Dyn11 10 0.4 27.5 721.7 4 TR.2P16-3108-PT-0002 1250 Dyn11 10 0.4 68.7 1804.2 5 TR.2P16-3106-PT-0002 2000 Dyn11 10 0.4 110 2886.8 6.25 Note: Source: Cap. = Capacity; Group con. = Group connection; Prim = Primary; Sec = Secondary ; PT = Power transformer. Xun and Wanya [8] and Jian, et al. [14]. Table 7 Presents variable frequency drive (VFD). Table 7. Variable frequency drive (VFD). ID VFD Rated AC Output kVA kV FLA Input Output Input Output Input Output %EFF %PF Hz 2P15-3102-MVVFD-0001 440 10 10 25.4 25.4 98 82.3 50 2P15-3102-MVVFD-0002 442 10 10 25.98 25.52 98 80.5 50 2P15-3102-MVVFD-0003 500 10 10 29.44 28.87 98 80.03 50 2P15-3102-MVVFD-0004 500 10 10 29.44 28.87 98 80.03 50 2P15-3102-MVVFD-0005 536.94 10 10 29.44 31 98 80.03 50 2P15-3102-MVVFD-0006 500 10 10 29.44 28.87 98 80.03 50 2P15-3102-MVVFD-0007 500 10 10 29.44 28.87 98 80.03 50 2P15-3102-MVVFD-0008 500 10 10 29.44 28.87 98 80.03 50 Note: Source: FLA = Full load ampere; PF = Power factor; eff = Efficiency; MVVFD= Medium voltage variable frequency device. Xun and Wanya [8] and Jian, et al. [14]. Table 8 Presents system data of cable. Table 8. Cable. ID Type kV Cond. /Phase Cond./ Cable Size (mm2) Length (m) Insulation type Cable81 CU 10 1 3/C 95 100.0 CLP 90℃ Cable82 CU 10 1 3/C 95 100.0 CLP 90℃ Cable83 CU 10 1 3/C 95 100.0 CLP 90℃ Cable84 CU 10 1 3/C 95 100.0 CLP 90℃ Cable85 CU 10 1 3/C 95 100.0 CLP 90℃ Cable91 CU 10 1 3/C 95 100.0 CLP 90℃ Cable92 CU 10 1 3/C 95 100.0 CLP 90℃ Cable93 CU 10 1 3/C 95 100.0 CLP 90℃ Cable94 CU 10 1 3/C 120 100.0 CLP 90℃ Cable95 CU 10 1 3/C 95 100.0 CLP 90℃ Cable97 CU 10 1 3/C 95 50.0 CLP 90℃ 298 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate ID Type kV Cond. /Phase Cond./ Cable Size (mm2) Length (m) Insulation type Cable98 CU 10 1 3/C 95 50.0 CLP 90℃ Cable99 CU 10 1 3/C 95 50.0 CLP 90℃ Cable100 CU 10 1 3/C 95 50.0 CLP 90℃ Cable101 CU 10 1 3/C 95 50.0 CLP 90℃ Cable102 CU 10 1 3/C 95 50.0 CLP 90℃ Cable103 CU 10 1 3/C 95 50.0 CLP 90℃ Cable109 CU 10 1 3/C 95 50.0 CLP 90℃ Cable110 CU 10 1 3/C 95 50.0 CLP 90℃ Cable111 CU 10 1 3/C 95 50.0 CLP 90℃ Cable112 CU 10 1 3/C 95 50.0 CLP 90℃ Cable113 CU 10 1 3/C 95 50.0 CLP 90℃ Note Source: CLP = Cross-linked polyethylene. Xun and Wanya [8]. 4.2. Modeling Single Line Diagram (SLD) D01 in ETAP Modeling SLD D01 using the ETAP 19.0.1 by inputting collected data. Based on the Electrical Calculation Report [8] short-circuit current data (I"k) for the 10kV main bus was obtained at 38.647kA with a voltage rating of 10kV. Therefore, by utilizing Equation 1 [15] the following results were obtained: 𝑆 = √3.𝑉. 𝐼 (1) 𝑆𝑠𝑐 = √3.𝑉. 𝐼𝑘 " 𝑆𝑠𝑐 = √3. 10𝑘𝑉.38,647𝑘𝐴 = 669,39𝑀𝑉𝐴𝑠𝑐 The result, Power Grid 1 (U1) and Power Grid 2 (U2) has a value of 669.39 MVAsc. Therefore, the modeling of the SLD D01 is illustrated in Figure 3. Figure 3. D01 single line diagram modeling on ETAP. 299 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 4.3. Short-Circuit Simulation in ETAP After the completion of creating the SLD D01 in ETAP, the next step is to perform a short-circuit simulation within the ETAP 19.0.1 software, following the steps below: a. Display the SLD D01. b. Click on the “Short-Circuit Analysis Mode”. c. Click on “Run 3-Phase Device Duty” (IEC 60909). d. ETAP will display the results of the short-circuit simulation as shown in Figure 4. Figure 4. Short-circuit simulation results in ETAP 19.0.1. The results of the short-circuit simulation can also be found in Table 9 of The Short Circuit Summary. 300 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Table 9. Short circuit summary report in ETAP 19.0.1. Bus Device Device capacity (kA) Short-circuit current (kA) Making ID kV ID Type Peak Ib Sym Ib asym Idc I”k ip Ib sym Ib asym Idc Ik Bus28 10.000 Bus28 Bus - - - - 11.289 27.365 - - - 8.636 Bus29 0.380 Bus29 Bus - - - - 48.356 98.650 - - - 39.207 Bus31 10.000 Bus31 Bus - - - - 11.289 27.365 - - - 8.636 Bus38 10.000 Bus38 Bus - - - - 11.289 27.365 - - - 8.636 Bus45 0.380 Bus45 Bus - - - - 19.247 32.209 - - - 17.093 Bus47 0.380 Bus47 Bus - - - - 37.489 76.420 - - - 31.704 Bus48 0.380 Bus48 Bus - - - - 48.222 107.666 - - - 39.155 Bus50 0.380 Bus50 Bus - - - - 39.702 80.748 - - - 32.544 Bus53 10.000 Bus53 Bus - - - - 11.289 27.365 - - - 8.636 Bus58 0.380 Bus58 Bus - - - - 48.475 98.868 - - - 39.207 Bus59 0.380 Bus59 Bus - - - - 37.565 76.557 - - - 31.704 Bus60 0.380 Bus60 Bus - - - - 48.341 107.936 - - - 39.155 Bus61 0.380 Bus61 Bus - - - - 19.267 32.234 - - - 17.093 Bus62 0.380 Bus62 Bus - - - - 39.783 80.894 - - - 32.544 Bus92 10.000 Bus92 Bus - - - - 11.289 27.365 - - - 8.636 Bus93 10.000 Bus93 Bus - - - - 11.289 27.365 - - - 8.636 Bus95 10.000 Bus95 Bus - - - - 11.289 27.365 - - - 8.636 Bus97 10.000 Bus97 Bus - - - - 11.289 27.365 - - - 8.636 Bus104 10.000 Bus104 Bus - - - - 11.289 27.365 - - - 8.636 Bus105 10.000 Bus105 Bus - - - - 11.511 27.929 - - - 8.636 Bus106 10.000 Bus106 Bus - - - - 11.511 27.929 - - - 8.636 Bus107 10.000 Bus107 Bus - - - - 11.511 27.929 - - - 8.636 Bus129 10.000 Bus129 Bus - - - - 11.511 27.929 - - - 8.636 Bus133 10.000 Bus133 Bus - - - - 11.511 27.929 - - - 8.636 Bus136 10.000 Bus136 Bus - - - - 11.511 27.929 - - - 8.636 Bus224 10.000 Bus224 Bus - - - - 11.511 27.929 - - - 8.636 Bus225 10.000 Bus225 Bus - - - - 11.511 27.929 - - - 8.636 Bus226 10.000 Bus226 Bus - - - - 11.511 27.929 - - - 8.636 D01 10kV I 10.000 D01 10kV I Bus - - - - 11.289 27.365 - - - 8.636 D01 10kV I 10.000 CB-D01-01 CB 100.000 40.000 42.167 13.343 11.289 27.365 101.161 10.407 2.245 - D01 10kV II 10.000 D01 10kV II Bus - - - - 11.511 27.929 - - - 8.636 D01 10kV II 10.000 CB-D01-02 CB 100.000 40.000 42.167 13.343 11.511 27.929 10.270 10.517 2.270 301 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 4.4. Load Flow Simulation in ETAP The steps to perform a load flow simulation in ETAP 19.0.1 are as follows: a. Display SLD D01. b. Click on the “load flow analysis mode”. c. Click “Run load flow calculation”. d. ETAP will display the results of the load flow simulation as shown in Figure 5, and Table 10 is the bus loading summary. Figure 5. Load flow analysis simulation results in ETAP 19.0.1. 302 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Table 10. Bus loading summary report in ETAP 19.0.1. Bus Directly connected load Total bus load Constant kVA Constant Z Constant I Generic ID kV Rated amp MW Mvar MW Mvar MW Mvar MW Mvar MVA %PF Amp Bus11 10.000 - - - - - - - - - 0.425 80.0 24.5 Bus54 10.000 - - - - - - - - - 0.425 80.0 24.5 Bus55 10.000 - - - - - - - - - 0.415 80.0 24.0 Bus56 10.000 - - - - - - - - - 0.377 80.0 21.8 Bus57 10.000 - - - - - - - - - 0.425 80.0 24.5 Bus64 10.000 - - - - - - - - - 0.425 80.0 24.5 Bus65 10.000 - - - - - - - - - 0.425 80.0 24.5 Bus66 10.000 - - - - - - - - - 0.377 80.0 21.8 Bus24 10.000 - - - - - - - - - 6.842 92.1 395.0 Bus27 10.000 - - - - - - - - - 6.933 87.4 400.3 Bus29 0.380 - 0.211 0.158 0.050 0.038 - - - - 0.327 80.0 508.3 Bus45 0.380 - 0.053 0.040 0.013 0.010 - - - - 0.082 80.0 126.9 Bus47 0.380 - 0.132 0.099 0.032 0.024 - - - - 0.205 80.0 317.3 Bus48 0.380 - 0.211 0.158 0.051 0.038 - - - - 0.327 80.0 508.0 Bus50 0.380 - 0.169 0.127 0.040 0.030 - - - - 0.262 80.0 406.6 Bus51 10.000 - - - - - - - - - 0.347 79.6 20.3 Bus58 0.380 - 0.211 0.158 0.050 0.038 - - - - 0.327 80.0 509.6 Bus59 0.380 - 0.132 0.099 0.031 0.024 - - - - 0.204 80.0 318.1 Bus60 0.380 - 0.211 0.158 0.050 0.038 - - - - 0.327 80.0 509.3 Bus61 0.380 - 0.053 0.040 0.013 0.009 - - - - 0.082 80.0 127.2 Bus62 0.380 - 0.169 0.127 0.040 0.030 - - - - 0.261 80.0 407.7 Bus63 10.000 - - - - - - - - - 0.346 79.6 20.4 Bus184 10.000 - 3.984 1.648 - - - - - - 4.312 92.4 253.1 Bus185 10.000 - 3.737 2.316 - - - - - - 4.396 85.0 259.1 Bus186 10.500 - - - - - - - - - 0.264 79.6 15.5 Bus187 10.500 - - - - - - - - - 0.082 79.8 4.8 Bus188 10.000 - - - - - - - - - 0.330 79.6 19.4 Bus189 10.000 - - - - - - - - - 0.330 79.5 19.4 Bus190 10.500 - - - - - - - - - 0.206 79.7 12.1 303 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Bus Directly connected load Total bus load Constant kVA Constant Z Constant I Generic ID kV Rated amp MW Mvar MW Mvar MW Mvar MW Mvar MVA %PF Amp Bus191 10.000 - - - - -0.970 - - - - 0.970 - 56.9 Bus192 10.000 - - - - -0.962 - - - - 0.962 - 56.6 Bus193 10.500 - - - - - - - - - 0.330 79.6 19.4 Bus194 10.500 - - - - - - - - - 0.264 79.6 15.5 Bus195 10.500 - - - - - - - - - 0.082 79.8 4.8 Bus196 10.500 - - - - - - - - - 0.206 79.7 12.1 Bus197 10.500 - - - - - - - - - 0.330 79.5 19.4 D01 10kV I 10.000 - - - - - - - - - 7.141 88.2 418.7 D01 10kV II 10.000 - - - - - - - - - 7.287 83.1 429.0 Note: MVA = Mega volt ampere. 304 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 4.5. Analysis of the Load Flow Simulation Results in ETAP 19.0.1 Based on Figure 5 and Table 10, the rating current passing through the CB is as follows: Table 11. The rating current passing through the CB at the outgoing 10kV Busbar that was analyzed. No ID CB From ID To ID Rated current (A) 1 CB168 Bus D01 10kV I Cable84 254.1 2 CB167 Cable85 25.5 3 CB169 Cable81 25.5 4 CB170 Cable82 24.9 5 CB180 Cable83 22 6 CB159 Cable99 19.4 7 CB163 Bus51 20.4 8 CB166 Cable100 12.1 9 CB173 Cable101 19.4 10 CB209 Bus D01 10kV II Cable94 259.1 11 CB208 Cable95 25.5 12 CB210 Cable91 25.5 13 CB211 Cable92 25.5 14 CB215 Cable93 22.5 15 CB204 Cable111 19.4 16 CB216 Bus63 20.4 17 CB207 Cable112 12.1 18 CB214 Cable113 19.4 According to Table 11, the highest current ratings are CB168 = 254.1A and CB209 = 259.1A. According to document [16] the voltage rating is 10kV with a normal voltage variation range of ±5%. The maximum normal voltage is 10.5kV (105%), and the minimum normal voltage is 9.5kV (95%). The voltage at Bus D01 10kV I is 9.818kV (98.18%) and the voltage at Bus D01 10kV II is 9.806kV (98.06%), therefore, the voltages at Bus D01 10kV I and Bus D01 10kV II still drop within the normal voltage variation range. 4.6. Analysis of ETAP 19.0.1's Short-Circuit Simulation Results The CBs that have been evaluated are only on the outgoing 10kV busbar D01 for 10kV induction motors and transformers. For faults on the 380V side, calculations are performed to obtain the short- circuit current values on the 10kV side by multiplying the short-circuit current values at 380V by the transformer ratio. Therefore, based on Figure 3, Figure 4, and Table 9, the CBs that have been analyzed are as shown in Table 12. Table 12. The CBs analyzed are those located on the outgoing 10kV busbar. No. ID CB From ID To ID Short-circuit current (kA) Peak current (kA) Fault on outgoing CB Fault on the 380v side 1 CB168 Bus D01 10kV I Bus28 11.289 - 27.365 2 CB167 Bus31 3 CB169 Bus38 4 CB170 Bus53 5 CB180 Bus92 6 CB159 Bus93 Bus188 Bus29 - 40.762*0.38/10=1.549 98.65*0.38/10=3.749 7 CB163 Bus D01 10kV I Bus104 11.289 - 27.365 Bus186 Bus50 - (33.624*0.38/10) + (17.356*0.38/10) =1.278+0.66=1.938 (80.748*0.38/10) + (32.209*0.38/10) =3.068+1.224=4.292 Bus187 Bus45 305 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate No. ID CB From ID To ID Short-circuit current (kA) Peak current (kA) Fault on outgoing CB Fault on the 380v side 8 CB166 Bus D01 10kV I Bus95 11.289 - 27.365 Bus190 Bus47 - 32.742*0.38/10=1.244 76.42*0.38/10=2.904 9 CB173 Bus D01 10kV I Bus97 11.289 - 27.365 Bus189 Bus48 - 40.744*0.38/10=1.548 107.666*0.38/10=4.091 10 CB209 Bus D01 10kV II Bus226 11.511 - 27.929 11 CB208 Bus225 12 CB210 Bus224 13 CB211 Bus136 14 CB215 Bus133 15 CB204 Bus129 Bus193 Bus58 - 40.881*0.38/10=1.553 98.868*0.38/10=3.757 16 CB216 Bus D01 10kV II Bus107 11.511 - 27.929 Bus194 Bus62 - (33.705*0.38/10) + (17.376*0.38/10) =1.281+0.66=1.941 (80.894*0.38/10) + (32.234*0.38/10) =3,074+1,225=4,299 Bus195 Bus61 17 CB207 Bus D01 10kV II Bus106 11.511 - 27.929 Bus196 Bus59 - 32.817*0.38/10=1.247 76.557*0.38/10=2.909 18 CB214 Bus D01 10kV II Bus105 11.511 - 27.929 Bus197 Bus60 - 40.863*0.38/10=1.553 107.936*0.38/10=4.102 Note: “*” is the multiplication sign. In document Agreement on 10kV [17] there is a technical data sheet for the CBs used in the Power Distribution System of the Alumina Plant (D01 Power Distribution System), as shown in Table 13: Table 13. The technical data sheet of CBs in the D01 power distribution system. No. Specification Information 1 Type Vacuum circuit breaker 2 Model 3AE8-12kV 3 Rated voltage (kV) 10 4 Maximum working voltage (kV) 12 5 Rated current (A) 1250 6 Rated frequency (Hz) 50 7 Rated breaking current (kA) 31.5 8 Full capacity breaking times Not less than 20000 9 Peak value (kA) 80 10 Rated short circuit duration (s) 4 11 Rated withstand voltage 1 min power-frequency (kV) 42 12 Rated withstand lightning impulse (kV) 75 13 Opening time (ms) ≤ 60 14 Closing time (ms) ≤ 75 15 Mechanical life Not less than 20000 If the specifications of the CBs in Table 13 are analyzed using IEC 60909, IEC 60059, and Siemens products [18], the results can be seen in Table 14. 306 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate Table 14. The selection of circuit breakers based on IEC 60909, IEC 60059, and siemens products. No ID CB Rated breaking current Rated peak value Rated current Data sheet (kA) ETAP IEC 60909 (kA) IEC 60059 (kA) Siemens (kA) Data sheet (kA) ETAP IEC 60909 (kA) IEC 60059 (kA) Siemens (kA) Data sheet (A) ETAP (A) IEC 60059 (A) Siemens (A) 1 CB168 31.5 11.289 12.5 25 80 27.365 31.5 63 1250 254.1 315 630 2 CB167 25.5 31.5 3 CB169 25.5 31.5 4 CB170 24.9 25 5 CB180 22 25 6 CB159 19.4 20 1.549 1.6 3.749 4 7 CB163 11.289 12.5 27.365 31.5 20.4 25 1.938 2 4.292 5 8 CB166 11.289 12.5 27.365 31.5 12.1 12.5 1.244 1.25 2.904 3.15 9 CB173 11.289 12.5 27.365 31.5 19.4 20 1.548 1.6 4.091 5 10 CB209 11.511 12.5 27.929 31.5 259.1 315 11 CB208 25.5 31.5 12 CB210 25.5 31.5 13 CB211 25.5 31.5 14 CB215 22.5 25 15 CB204 19.4 20 1.553 1.6 3.757 4 16 CB216 11.511 12.5 27.929 31.5 20.4 25 1.941 2 4.299 5 17 CB207 11.511 12.5 27.929 31.5 12.1 12.5 1.247 1.25 2.909 3.15 18 CB214 11.511 12.5 27.929 31.5 19.4 20 1.553 1.6 4.102 5 According to Table 14, the appropriate specification selection for Siemens CB products is as follows: • The rated breaking current of 31.5kA can be replaced with 25kA. • The rated peak value of 80kA can be replaced with 63kA. • The rated current of 1250A can be replaced with 630A. Based on the 3AE8 Vacuum Circuit Breaker [18] the replacement of the CB specifications does not affect D01 Power Distribution System switchgear panel because the recommended specifications of CB match the brand, model, dimensions, and size of the original. 5. Conclusion We can draw the following conclusions from simulations and analyses of the CBs in the D01 Power Distribution System for 10kV induction motor loads and transformers: To improve maintenance efficiency in the medium-voltage network system, the current CBs can be replaced with Siemens Model 3AE8-12kV with these specifications: a rated breaking current of 25 kA, a rated peak value of 63 kA, and a rated current of 630 kA. 307 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 8, No. 4: 290-308, 2024 DOI: 10.55214/25768484.v8i4.969 © 2024 by the authors; licensee Learning Gate 6. Recommendations Based on this research, the following recommendations are provided: • During maintenance periods, PT BAI may consider replacing the CBs in the D01 Power Distribution System for 10kV induction motor loads and transformers with Siemens circuit breakers, Model 3AE8-12kV, which have the following specifications: a rated breaking current of 25kA, a rated peak current of 63kA, and a rated current of 630A. • The focus of this research is on selecting the appropriate specifications for the CBs on the outgoing busbar of the D01 Power Distribution System. Further research can be undertaken to calculate the economic value of replacing the CBs with the recommended capacity. Funding: This study received no specific financial support. Institutional Review Board Statement: Not applicable. Transparency: The authors confirm that the manuscript is an honest, accurate and transparent account of the study that no vital features of the study have been omitted and that any discrepancies from the study as planned have been explained. This study followed all ethical practices during writing. Competing Interests: The authors declare that they have no competing interests. Authors’ Contributions: All authors contributed equally to the conception and design of the study. All authors have read and agreed to the published version of the manuscript. Copyright: © 2024 by the authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). References [1] L. Kong and H. 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