Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 60 Operation of Circuit Breakers: Data and Analysis V.C. Maduemea , M. J. Mbunwea*, T. C. Maduemea , M. Ayaz Ahmadb , C. V. Anghel Drugarinc aDepartment of Electrical Engineering, University of Nigeria Nsukka, 410001, Nigeria bPhysics Department, Faculty of Science, P.O.Box 741, University of Tabuk, 71491, Saudi Arabia cDepartment of Electronics and Informatics Engineering, “Eftimie Murgu”, University of Resita, Resita, Romania *Corresponding author: muncho.mbunwe@unn.edu.ng & mayaz.alig@gmail.com Received: 16 January 2021; Accepted: 12 June 2021; Published: October 2021 Abstract An attempt has been made for the analysis on Circuit breakers (CBs) this paper. First, the types and arcing phenomenon of Oil and SF6 Circuit breakers were briefly discussed. However, various CBs were analyzed in terms of certain outage frequencies and reliability indices to ascertain the most reliable CB. This was possible using data collected from the 33kV Transmission Company of Nigeria (TCN) New Haven, Enugu. After the analysis, Emene Industrial CB had the highest value of availability of 0.9999 and the lowest tripping report while Ezillo had the highest failure rate of 0.1032. Keywords: Circuit breaker; Outage; Failure rate; Availability; Reliability To cite this article: Madueme, V.C., Mbunwe, M.J., Madueme, T.C., Ayaz Ahmad, M., Anghel Drugarin, C.V. (2021). Operation of Circuit Breakers: Data and Analysis. Multidisciplinary Journal for Education, Social and Technological Sciences, 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ https://orcid.org/0000-0002-8963-0126 https://orcid.org/0000-0003-0432-4574 https://orcid.org/0000-0002-5731-5439 https://orcid.org/0000-0002-1906-0623 https://doi.org/10.4995/muse.2021.12406 Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 61 1. Introduction Once a power system is established it is necessary to protect it from internal and external faults. So we use some protecting and sensing device like circuit breakers, Relays, Fuses etc (Saxena, Singh, Ali, Gandhi, 2012). Power circuit breaker is one of the most important protection and control apparatus in the power system (Suwanasri, Hlaing and Suwanasri, 2014). A circuit breaker is a switching device that interrupts the abnormal or fault current. It is a mechanical device that disturbs the flow of high magnitude (fault) current and in addition, performs the function of a switch. The circuit breaker is mainly designed for closing or opening of an electrical circuit, thus protects the electrical system from damage. Circuit Breakers represent one of the most critical power apparatus in the power system. They are used to change topology of the power system to accommodate various configurations in routing the load. CBs are also used to isolate faulted parts of the system as a part of the protective relaying operation (Kezunovic, Ren, Latisko, Sevcik, Lucey, Cook, and Koch, 2005). Circuit breaker essentially consists of fixed and moving contacts. These contacts are touching each other and carrying the current under normal conditions when the circuit is closed. When the circuit breaker is closed, the current carrying contacts, called the electrodes, engaged each other under the pressure of a spring. During the normal operating condition, the arms of the circuit breaker can be opened or closed for a switching and maintenance of the system. To open the circuit breaker, only a pressure is required to be applied to a trigger (Circuit globe, 2017). Figure 1: Diagram of an Oil Circuit Breaker (Circuit globe, 2017) Whenever a fault occurs on any part of the system, the trip coil of the breaker gets energized and the moving contacts are getting apart from each other by some mechanism, thus opening the circuit. According to Pinnekamp (2007), Several GVA of power can be tamed by a circuit breaker within fractions of a second. Such is the importance of this single device that tens of billions of dollars have been spent on its development over the last 100 years. https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 62 2. Types of Circuit Breaker Circuit breakers are mainly classified on the basis of rated voltages. Circuit breakers below rated voltage of 1000V are known as the low voltage circuit breakers and above 1000V are called the high voltage circuit breakers. The most general way of the classification of the circuit breaker is on the basis of the medium of arc extinction. Such types of circuit breakers are as follows :- [1] Oil Circuit Breaker a. Bulk Oil Circuit Breaker b. Minimum Oil Circuit Breaker [2] Minimum Circuit Breaker [3] Air Blast Circuit Breaker [4] Sulphur Hexafluoride Circuit Breaker [5] Vacuum Circuit Breaker [6] Air Break Circuit Breaker All high-voltage circuit breakers may be classified under two main categories i.e oil circuit breakers and oil-less circuit breaker (Electrical concepts, Circuit breaker and Arc Phenomenon, 2017). 3. Arc Phenomenon in Circuit Breaker When a short-circuit occurs, a heavy current flows through the contacts of the circuit breaker before they are opened by the protective system. At the instant when the contacts begin to separate the contact area decreases rapidly and large fault current causes increased current density and hence rise in temperature. The heat produced in the medium between contacts (usually the medium is oil or air) is sufficient to ionize the air or vaporize and ionize the oil. The ionized air or vapour, acts as conductor and an arc is struck between the contacts. The potential difference between the contacts is quite small and is just sufficient to maintain the arc. The arc provides a low resistance path and consequently the current in the circuit remains uninterrupted so long as the arc persists. During the arcing period, the current flowing between the contacts depends upon the arc resistance. The greater arc resistance will represent to the smaller the current flow between the contacts. The arc resistance depends upon the following factors: • Degree of ionization - the arc resistance increases with the decrease in the number of ionized particles between the contacts. • Length of the arc - the arc resistance increases with the length of the arc i.e. separation of contacts. https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ http://circuitglobe.com/arc-extinction.html http://circuitglobe.com/arc-extinction.html http://circuitglobe.com/oil-circuit-breaker.html http://circuitglobe.com/bulk-and-minimum-oil-circuit-breaker.html http://circuitglobe.com/bulk-and-minimum-oil-circuit-breaker.html http://circuitglobe.com/sf6-sulphur-hexaflouride-circuit-breaker.html http://circuitglobe.com/vacuum-circuit-breaker.html http://circuitglobe.com/air-break-circuit-breaker.html http://www.studyelectrical.com/2014/05/classification-types-of-circuit-breakers.html Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 63 • Cross section of arc - the arc resistance increase with the decrease in the area of cross section of the arc (Electrical Systems, 2017). Figure 2: Diagram of the SF6 Circuit breaker (Electrical Systems, 2017) When the contacts of a circuit breaker are separated under fault conditions, an arc is struck between them. The current is thus able to continue until the discharge ceases. The production of arc not only delays the current interruption process but it also generates enormous heat which may cause damage to the system or to the breaker itself. Therefore, the main problem in a circuit breaker is to extinguish the arc within the shortest possible time so that heat generated by it may not reach a dangerous value (Electrical Systems, 2017). 4. Data and Analysis The data for our analysis was collected from the 33kV Transmission Company of Nigeria (TCN) located in New Haven, Enugu (TCN, Tripping reports, 2016). It contained data of up to 59 feeders/CBs in Enugu region for the period of three (3) months (April – June 2016). The data contained the outage (tripping) report for the feeders together with the tripping time, restoration time, type of fault, time duration before restoration. As a result of enormity of the data, we tried to group the number of outages per feeder in terms of their outage frequencies such as: i. Most Frequent Outages: for outages greater than 100 times. ii. Very Frequent Outages: Outages between 31-99 iii. Less frequent Outages: between 10 -30 iv. Occasional: between 3 -9 v. Rare: between 1-2 https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ http://www.studyelectrical.com/2014/05/principles-and-methods-of-arc.html Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 64 The tables and their corresponding chart representations are given to further illustrate the frequency of outages of each feeder between April and June 2016. Table 1: Most Frequent Outages (>100) Feeder Outages Ezillo 152 Yahe 140 Itigidi 133 Nnewi 131 Agulu 127 Ehamufu 116 Obosi 115 Barracks Rd. 104 North Bank 104 Umunya 102 Table 2: Very Frequent Outages (31-99) Feeder Outages Achi 76 Nnpc 76 Nicuss 74 Neni 73 Neni 33 70 Atani 70 Amechi 69 Isieke 67 Ankpa 63 New Nnpc 62 Udi 62 Army Barracks 59 Oju 47 Govt House 42 Wukari 40 Katsina-Ala 39 Taraku 36 Emene Ind. Layout 33 Table 3: Less Frequent Outages (10-30) Feeder Outages Enugu-Ukwu 27 Ind.Layout 26 Ituku/Ozalla 25 Yandev 22 Kingsway Line2/9th Mile 20 Asaba 18 Awada Ii 18 Emene 17 Feeder 1 17 Makurdi 16 Water Works 16 Feeder 2 13 Feeder 4 12 Mobtr 10 Table 4: Occasional Outages (3-9) Feeder Outages Afikpo 9 Golden Oil 9 Thinkers Corner 8 Aguleri 7 Unn 7 Feeder 3 6 Kingsway Line 1 5 Ibagwa 4 Nsukka 3 Table 5: Rare Outages (1-2) Feeder Outages Feeder 5 2 Mobtr 2 2 Mob 45 2 Oji 2 Agbor 1 Bcc 1&Ii 1 Emene Industrial 1 Oji Local 1 https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 65 (a) (c) (b) (d) (e) 0 5 10 15 20 25 30 EN U G U -U KW U IN D . L A YO U T IT U KU /O ZA LL A YA N D EV A W A D A II FE ED ER 1 EM EN E M A KU RD I W A TE R W O RK S FE ED ER 2 FE ED ER 4 M O BS TR Less frequent outages (10-30) 0 2 4 6 8 10 Occasional outages (3-9) 0 0,5 1 1,5 2 2,5 Rare outages (1-2) 0 20 40 60 80 100 120 140 160 EZ IL LO YA H E IT IG ID I N N EW I A G U LU EH A M U … O BO SI BA RR A … N O RT H … U M U N YA Most frequent outages ( >100) 0 10 20 30 40 50 60 70 80 Very frequent outages (31-99) https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 66 Figure 3: Charts showing the various frequency of outage of the CBs (a) most frequent outages (b) very frequent outages (c) less frequent outages (d) occasional outages (e) rare outages 5. Reliability Analysis According to Anyaka B.O. (2012), Some reliability indices were calculated from the data obtained such as: • Mean Time to Repair (MTTR) 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂 𝐷𝐷𝑂𝑂𝐷𝐷𝑇𝑇𝑇𝑇𝐷𝐷𝑇𝑇𝐷𝐷 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂𝑂𝑂 (1) • Mean Time between Failures (MTBF) 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑃𝑃𝑂𝑂𝐷𝐷𝐷𝐷𝑇𝑇𝑃𝑃− 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂 𝐷𝐷𝑂𝑂𝐷𝐷𝑇𝑇𝑇𝑇𝐷𝐷𝑇𝑇𝐷𝐷 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂𝑂𝑂 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑂𝑂𝐷𝐷𝑇𝑇𝑇𝑇𝐷𝐷𝐷𝐷𝑂𝑂 𝑇𝑇𝐷𝐷𝑇𝑇𝑂𝑂 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂𝑂𝑂 (2) • Failure Rate, λ λ = 1 𝑀𝑀𝑇𝑇𝑀𝑀𝑀𝑀 (3) • Availability, A A = 𝑀𝑀𝑇𝑇𝑀𝑀𝑀𝑀 𝑀𝑀𝑇𝑇𝑀𝑀𝑀𝑀+𝑀𝑀𝑇𝑇𝑇𝑇𝑀𝑀 (4) It should be noted that the total period stands for the total time in consideration (i.e. 3 months = 2184 hours). After calculations, the results are shown in Tables and graphs. Table 6 and Figure 4 shows Most Frequent Outages Reliability results. Table 6. Most Frequent Outage Reliability results FEEDER Outages Duration MTTR MTBF Failure rate Availability EZILLO 152 711 4.68 9.69 0.1032 0.6743 YAHE 140 544.43 3.89 11.71 0.0854 0.7506 ITIGIDI 133 863.12 6.49 9.93 0.101 0.6048 NNEWI 131 672.55 5.13 11.88 0.0842 0.6984 AGULU 127 487.97 3.84 13.35 0.075 0.7766 EHAMUFU 116 357.3 3.08 15.75 0.0635 0.8364 OBOSI 115 621.29 5.4 13.59 0.0736 0.7156 BARRACKS RD. 104 314.48 3.02 17.98 0.0556 0.8562 NORTH BANK 104 374.64 3.6 17.4 0.0575 0.8286 UMUNYA 102 564.83 5.54 15.87 0.063 0.7412 https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 67 Figure 4: Availability and failure rate characteristic for most frequent outages. Table 7 and Figure 5 show very Frequent Outage Reliability results. Table 7: Very frequent Outage reliability results FEEDER Outages Duration MTTR MTBF Failure rate Availability ACHI 76 534.68 7.04 21.7 0.0461 0.755 NNPC 76 170.85 2.25 26.49 0.0378 0.9217 NICUSS 74 328.73 4.44 25.07 0.0399 0.8495 NENI 73 408.04 5.59 24.33 0.0411 0.8132 33 70 571.7 8.17 23.03 0.0434 0.7381 ATANI 70 207.03 2.96 28.24 0.0354 0.9051 AMECHI 69 435.48 6.31 25.34 0.0395 0.8006 ISIEKE 67 475.55 7.1 25.5 0.0392 0.7822 ANKPA 63 175.12 2.78 31.89 0.0314 0.9198 NEW NNPC 62 89.29 1.44 33.79 0.0296 0.9591 UDI 62 677.78 10.93 24.29 0.0412 0.6897 ARMY BARRACKS 59 194.7 3.3 33.72 0.0297 0.9109 OJU 47 247.58 5.27 41.2 0.0243 0.8866 GOVT HOUSE 42 61.33 1.46 50.54 0.0198 0.9719 WUKARI 40 232.01 5.8 48.8 0.0205 0.8938 KATSINA- ALA 39 399.93 10.25 45.75 0.0219 0.817 TARAKU 36 254.88 7.08 53.59 0.0187 0.8833 EMENE IND. LAY. 33 77.9 2.36 63.82 0.0157 0.9604 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Availability Failure rate https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 68 Figure 5: Availability and failure rate characteristic for very frequent outages Table 8 and Figure 6 show the most Frequent Outages Reliability results. Table 8: Less frequent outage reliability results FEEDER Outages Duration MTTR MTBF Failure rate Availability ENUGU-UKWU 27 425.42 15.76 65.13 0.0154 0.8052 IND.LAYOUT 26 44.85 1.73 82.28 0.0122 0.9794 ITUKU/OZALLA 25 106.53 4.26 83.1 0.012 0.9512 YANDEV 22 151.62 6.89 92.38 0.0108 0.9306 KINGSWAY LINE2/9TH MILE 20 38.3 1.92 107.29 0.00932 0.9824 ASABA 18 133.1 7.39 113.94 0.00878 0.9391 AWADA II 18 21.17 1.18 120.16 0.00832 0.9903 EMENE 17 67.85 3.99 124.48 0.00803 0.9689 FEEDER 1 17 57.1 3.36 125.11 0.00799 0.9738 MAKURDI 16 44.8 2.8 133.7 0.00748 0.9795 WATER WORKS 16 187.33 11.71 124.79 0.00801 0.9142 FEEDER 2 13 50.9 3.92 164.08 0.00609 0.9767 FEEDER 4 12 45.3 3.78 178.23 0.00561 0.9792 MOBTR 10 6.63 0.66 217.74 0.00459 0.997 0 0,2 0,4 0,6 0,8 1 1,2 A CH I N N PC N IC U SS N EN I 33 A TA N I A M EC H I IS IE KE A N KP A N EW N N PC U D I A RM Y BA RR A CK S O JU G O V T H O U SE W U KA RI KA TS IN A -A LA TA RA KU EM EN E IN D .… Availability Failure rate https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 69 Figure 6: Availability and failure rate characteristic for less frequent outages Table 9 and Figure 7 show the most Frequent Outages Reliability results. Table 9: Occasional outage reliability results FEEDER Outages Duration MTTR MTBF Failure rate Availability AFIKPO 9 193.2 21.47 221.2 0.00452 0.9115 GOLDEN OIL 9 45.75 5.08 237.58 0.00421 0.9791 THINKERS CORNER 8 18.15 2.27 270.73 0.00369 0.9917 AGULERI 7 357.95 51.13 260.86 0.0038 0.8361 UNN 7 56.95 8.14 303.86 0.00329 0.9739 FEEDER 3 6 16.68 2.78 361.22 0.00277 0.9924 KINGSWAY LINE 1 5 3.83 0.766 436.03 0.00229 0.9982 IBAGWA 4 26.2 6.55 539.45 0.00185 0.988 NSUKKA 3 91.72 30.57 697.43 0.00143 0.958 0 0,2 0,4 0,6 0,8 1 1,2 Failure rate Availability https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 70 Figure 7: Availability and failure rate characteristic for Occasional outages Table 10 and Figure 8 show the most Frequent Outages Reliability results. Table 10: Rare outage reliability results FEEDER Outages Duration MTTR MTBF Failure rate Availability FEEDER 5 2 100.11 50.06 1041.95 0.00096 0.9542 MOBTR 2 2 1.07 0.54 1091.47 0.000916 0.9995 MOB 45 2 1.67 0.84 1091.17 0.000916 0.9992 OJI 2 3.35 1.68 1090.33 0.000917 0.9985 AGBOR 1 4.75 4.75 2179.25 0.00046 0.9978 BCC 1&II 1 37.73 37.73 2146.27 0.00047 0.9827 EMENE INDUSTRIAL 1 0.12 0.12 2183.88 0.000458 0.9999 OJI LOCAL 1 1.93 1.93 2182.07 0.000458 0.9991 0 0,2 0,4 0,6 0,8 1 1,2 Availability Failure rate https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 71 Figure 8: Availability and failure rate characteristic for rare outages. 6. Observations and Conclusion From the reliability analysis carried out, the following observations are made: • In the most frequent outage result, we can observe low availabilities at Itigidi and Obosi Feeders with corresponding high failure rates. • The very frequent outage result showed low availability values and high failure rates at Achi, 33kV Onitsha and Udi feeders. • The Feeder at Enugu-Ukwu has the lowest availability in the less frequent outage results. • Aguleri CB has the highest failure rate in the occasional outage results • Feeder 5 in Asaba station has the lowest availability in the rare outage results. The availability of a system shows how reliable the system is. From our analysis, the high outages as a result of over-current and earth faults imply that the particular feeder is less reliable. By calculation, Ezillo CB has the lowest availability value (0.6743) and Emene Industrial CB has the highest availability value (0.9999). Hence, Emene Industrial CB has the highest reliability. However, this does not necessary mean that this feeder is the most reliable one because any CB can fail at any time due to some factors such as overloading, malfunction, weather conditions, human errors and so on. The earth-fault and over-current directional and inverse time relays should be employed in the power system to reduce the high outages due to faults on the system. 0 0,2 0,4 0,6 0,8 1 1,2 Availability Failure rate https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 72 Compensation should also be done on areas with high loading to improve voltage profile and reactive power and hence increase transmission line load ability. Acknowledgement: The authors are immensely grateful for the financial support from “African Centre of Excellence (ACE-SPED) University of Nigeria, Nsukka” to enable us to achieve the research (Muncho J. Mbunwe et al., 2019-2021). Conflicts of Interest: The authors declare no conflict of interest. References Anyaka, B.O. (2012). Reliability and Maintainability of Power System [Lecture Note]. http://engineering.unn.edu.ng Circuit globe, (n.d.). Circuit breaker, Retrieved June 10, 2017, from open source:- http://circuitglobe.com/circuit-breaker.html Electrical concepts, Circuit breaker and Arc Phenomenon, (n.d.). Retrieved June 10, 2017, from open source: http://electricalbaba.com/circuit-breaker-and-arc-phenomenon/ Electrical Systems, (n.d.). Retrieved June 10, 2017, from open source: http://skm-eleksys.com/2012/02/sf6- circuit-breaker-working.html Kezunovic, M. Ren, Z. Latisko, G. Sevcik, D.R. Lucey, J.S. Cook, W.E. and Koch, E.A. (2005). Automated Monitoring and Analysis of Circuit Breaker Operation, IEEE Transactions on Power Delivery, 20(3), p. 1910. https://doi.org/10.1109/TPWRD.2005.848466 Pinnekamp, F. (2007). The circuit breaker: a showcase of industrial product development, Transmission group R&D and technology, ABB, Switzerland, p.31. https://new.abb.com/docs/default- source/technology/brosch%C3%BCre-chchrc2017final-einseitig-(002).pdf?sfvrsn=e3f37d14_2 Saxena, S. Singh, A. Ali, M. Gandhi, K. (2012). Various Types of Circuit Breakers used in Power System for Smooth Working of the Transmission Line, MIT International Journal of Electrical and Instrumentation Engineering, 2(2), p. 106. https://www.semanticscholar.org/paper/06918326da2b2ac6fd80620d88961b68554b72ed Suwanasri, T. Hlaing, M.T. and Suwanasri, C. (2014). Failure Rate Analysis of Power Circuit Breaker in High Voltage Substation, GMSARN International Journal, 8(1), 1-6. http://gmsarnjournal.com/home/journal-vol/journal-vol-8-no-1/ https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ http://engineering.unn.edu.ng/ http://circuitglobe.com/circuit-breaker.html http://electricalbaba.com/circuit-breaker-and-arc-phenomenon/ http://skm-eleksys.com/2012/02/sf6-circuit-breaker-working.html http://skm-eleksys.com/2012/02/sf6-circuit-breaker-working.html https://doi.org/10.1109/TPWRD.2005.848466 https://new.abb.com/docs/default-source/technology/brosch%C3%BCre-chchrc2017final-einseitig-(002).pdf?sfvrsn=e3f37d14_2 https://new.abb.com/docs/default-source/technology/brosch%C3%BCre-chchrc2017final-einseitig-(002).pdf?sfvrsn=e3f37d14_2 https://www.semanticscholar.org/paper/06918326da2b2ac6fd80620d88961b68554b72ed http://gmsarnjournal.com/home/journal-vol/journal-vol-8-no-1/ Multidisciplinary Journal for Education http://polipapers.upv.es/index.php/MUSE/ Social and Technological Sciences e-ISSN: 2341-2593 Madueme et al. (2021) Mult. J. Edu. Soc & Tec. Sci. (2021), 8(2), 60-73. https://doi.org/10.4995/muse.2021.12406 73 Transmission Company of Nigeria. (2016). Tripping reports April – June 2016 [Unpublished Raw data]. New Haven, Enugu, Nigeria. https://www.tcn.org.ng/page_history.php Muncho J. Mbunwe, M. Ayaz Ahmad, Syed Khalid Mustafa. (2020). An effective energy saving design strategy to maximize the use of electricity, J. Math. Comput. Sci., 10(5), 1808-1833, https://doi.org/10.28919/jmcs/4775 Mbunwe Muncho J., Ezema Ejiofor E., Ngwu Anene A., C V Anghel Drugarin, M. Rehan Ajmal, M Ayaz Ahmad. (2021). Characterization of three phase solid state VAR compensation scheme in three phase pulse width modulation voltage source inverter, Journal of Physics: Conference Series, Vol. 1781, 012034, https://doi.org/10.1088/1742-6596/1781/1/012034 M. Ayaz Ahmad, Irina Tvoroshenko, Jalal Hasan Baker, Vyacheslav Lyashenko. (2019). Modeling the Structure of Intellectual Means of Decision-Making Using a System Oriented NFO Approach, International Journal of Emerging Trends in Engineering Research , Vol. 7(11), 460-465. https://doi.org/10.30534/ijeter/2019/107112019 Mykhailo Kopot, M. Ayaz Ahmad, Vyacheslav Lyashenko, Syed Khalid Mustafa. (2020). Prospects for Creating Sub-Millimeter Magnetrons, International Journal of Advanced Trends in Computer Science and Engineering, Vol. 9(4), 6184-6188. https://doi.org/10.30534/ijatcse/2020/294942020 M. Ayaz Ahmad, Irina Tvoroshenko, Jalal Hasan Baker, Vyacheslav Lyashenko. (2019). Computational Complexity of the Accessory Function Setting Mechanism in Fuzzy Intellectual Systems, International Journal of Advanced Trends in Computer Science and Engineering, Vol. 8(5), 2370- 2377. https://doi.org/10.30534/ijatcse/2019/77852019 Muncho J. Mbunwe, Udochukwu B. Akuru, Hilary U. Ezea, Ogbonnaya I. Okoro, M. Ayaz Ahmad. (2020). Some Aspects of Future Energy Generation in Using of Solar Power Satellites, Int. J. Anal. Appl., 18 (1), 117-128. https://doi.org/10.28924/2291-8639-18-2020-117 https://doi.org/10.4995/muse.2021.XXX http://polipapers.upv.es/index.php/MUSE/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://www.crossref.org/ https://www.tcn.org.ng/page_history.php https://doi.org/10.1088/1742-6596/1781/1/012034 https://doi.org/10.30534/ijeter/2019/107112019 https://doi.org/10.30534/ijatcse/2020/294942020 https://doi.org/10.30534/ijatcse/2019/77852019 https://doi.org/10.28924/2291-8639-18-2020-117 1. Introduction 2. Types of Circuit Breaker 3. Arc Phenomenon in Circuit Breaker