Sebuah Kajian Pustaka: JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 43 Thermal Characteristic of Fire Resistance Electrical Cable for Residential Wiring Installation Yunita Saria and Mochammad Syamsul Ma'arifb a Department of Mechanical Engineering, Faculty of Engineering, State University of Jakarta Kampus A, Jl. Rawamangun Muka, Gedung L, Jakarta, Indonesia Telephone +62-21-4751523, 4786480 e-mail: yunitasari@unj.ac.id b Department of Mechanical Engineering, Faculty of Engineering, Brawijaya University Jl. MT Haryono 167, Malang, Indonesia Telephone +62-341-554291 e-mail: syamsulm@ub.ac.id Abstract The objective of the research was to investigate thermal characteristic of electrical cable for residential wiring installation in order to acquire the initial data for fire protection study especially connected to short circuit. The research methods were testing the characteristic of cable by differential scanning calorimetry (DSC), fire resistant test, and current injection test according to International Standard IEC 60332-1-1. The results of the test were: differential scanning calorimetry gave the flame temperature of the cable was 3100C, fire resistant test shown the length of charred/melted cable was 65 mm and fire was extinguished in 10 s after the source of flame was cut, the current injection test showed that for current of 60 A, the cable started to melted and produce smoke after 270 s. The result showed that the cable complies with the specification, i.e. flame retardant cable or fire resistance cable as proved by test results and can be concluded that the cable gives adequate protection to the fire. Also, it can be concluded that whenever short circuits occur, the cable able to withstand the high current and temperature for prolonged time and may only resulted in charred or melted only and doesn't make the cable came into flame/fire. Even if the fire is occurred in the cable as results of short circuit, the propagation is relatively not existed. Keywords: thermal characteristics; electric; cable; residential 1. INTRODUCTION The research was initiated by several residential fires incident which caused by short circuit. The main trigger of the incidents was the use of non-standard cable in residential electrical wiring which can't withstand the high current and also high temperature which leads to the short circuit. As efforts to improve fire safety standard for residential electric wiring installation, the thermal characteristic of electric cable was need to be investigated since it provides the initial data to protect the electric wiring installation from the danger of fire caused by short circuit. This effort was in line with the development of Undergraduate Program of Fire Protection Engineering, Department of Mechanical Engineering, State University of Jakarta, the only one of such undergraduate program in Indonesia, which focused on the research of flame retardant or fire resistance material especially in Research Laboratory of Fire, Material and Safety Engineering. Also, the research has another objective in giving contribution in developing fire protection technology especially for residential electrical wiring installation. As commonly known, fire is not occurring by itself but rather as product of chemical process which involved fuel with oxygen and helped by heat. The theory is known as fire triangle as shown in Figure 1.1. mailto:yunitasari@unj.ac.id mailto:xxxx@xxxx.xxx JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 44 Figure 1.1 Triangle of Fire Fire is triggered by source of fire such as cigarette, matches, or short circuit; and because of the presence of flammable substance like the things made of paper, wood, or cloth will make the fire propagate and spread then make the surrounding area become hotter. When the material in surrounding area is converted into flammable gas and the temperature is high enough, flashover wills occurs and makes all the area consumed by fire in which temperature may rise to 12000C. Electrical cable is consisted of two components, i.e. conductor and isolator, with the conductor mays takes form of copper and aluminum. Copper for electrical cable has, at least, purity of 99.9%. The conductivity of copper is much depending on its impurity and for example alloying with 2% of Fe can increase the intrinsic resistance of copper up to 10%. The hardness of copper also has influence on the conductivity. The soft copper with 100% IACS (International Annealed Cooper Standard) conductivity has tensile strength of 195- 245 N/mm2 while hard copper with tensile strength of 390-440 N/mm2 has only 97% IACS or roughly 3% lower than conductivity of soft copper. Aluminum as conductor also need to be in pure condition, commonly as high as 99.5%. The conductivity of aluminum also is influenced by its hardness by is not prominent as in copper. Soft aluminum with conductivity of 61% IACS has tensile strength of 60-70 N/mm2 while conductivity of hard aluminum with tensile strength of 60-70 N/mm2 has only 1% lower than the soft one. As material for isolator in electric cable usually take form of thermoplastic and thermoset. There are several thermoplastic polymers which usually used as isolator material for electric cable such as polyvinylchloride (PVC) and polyethylene (PE). The electrical property of PE is considered better than PVC but it has drawback in its tendency to burn. When it is caught in fire, the flame will propagate even though the source of flame already cut off. Therefore, is almost rarely used in high current electric cable. Test conducted in the research was Test on Electric and Optical Fiber Cable under Fire Conditions according to IEC (International Electrotechnical Commission) Test Standard Number IEC 60331: Tests for Electric Cables under Fire Conditions – Circuit Integrity. The test is intended to be standard for fire resistance cable. The cable is tested under fire condition with temperature reach minimum 7500C and is expected to keep its integrity during the test. The test is commonly used as standard in testing of flame propagation in cable, especially for flame retardant cable. Flame retardant cable is the fire resistant cable designed to resist flame propagation along cable route in fire situation. JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 45 Figure 1.2 Curve of DSC Figure 1.2 depicts the curve characteristic of typical DSC test while Figure 1.3 shows the structure of PVC polymer. Figure 1.3 gives electrical data on the cable used in test. Figure 1.2 Structure of PVC polymer Electrical Data Conductor Inductance (mH/km) Current-Carrying Capacity at 30o C Short circuit current at 1 sec Max, (A) Nom. Cross. Sec. (mm2) DC Resistance at 20o C (Ω/km) AC Resistance at 70o C (Ω/km) in air Max, (A) in ground Max, (A) 1.5 12.1 14.478 0.328 20 23 0.17 2.5 7.41 8.866 0.304 26 31 0.29 4 4.61 5.516 0.303 34 40 0.46 6 3.08 3.685 0.288 44 50 0.69 10 1.83 2.190 0.269 60 68 1.15 16 1.15 1.376 0.255 79 88 1.84 25 0.727 0.87 0.255 105 114 2.88 35 0.524 0.627 0.246 129 137 4.03 50 0.387 0.464 0.247 162 168 5.75 70 0.268 0.321 0.238 203 206 8.05 95 0.193 0.232 0.238 250 247 10.93 120 0.153 0.184 0.233 289 281 13.8 150 0.124 0.150 0.233 330 315 17.25 185 0.0991 0.121 0.233 381 356 21.28 240 0.0754 0.093 0.232 451 412 27.60 300 0.0601 0.075 0.231 517 464 34.50 400 0.0470 0.060 0.229 594 524 41.20 * For further information about rating factor for certain cable arrangement can be found on supplementary technical information www.kmi.co.id PT KMI Wire and Cable Tbk reserves the rights to change the data content without prior notification Figure 1.3 Data of Electric Cable 1 4 2 3 3 -0 3 R e v . 2 .0 / 2 0 0 9 http://www.kmi.co.id/ JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 46 2. METHODS The method in determining thermal characteristic of flame retardant and fire resistance of residential electrical wire was given in Figure 1. It consisted of DSC test, flame test, and current injection test. Figure 2.1 Flowchart of the research The tests were conducted according to International Standard IEC 60332-1-1 Test on Electric and Optical Fiber Cable under Fire Conditions. The specimen for the test was electrical cable for residential use with compliance to IEC standard (Figure 2.2). The DSC test was conducted with heating rate of 200C per minutes for 20 minutes (Figure 2.3). Flame test was using flame temperature of 12850C with flame length of 125 mm and current injection test was conducted using current of 5A, 10A, 20, A, 40A, and 60A for 300 seconds (5 minutes). Figure 3.2 NYY 3x (1.5-400) mm2 0.6/ 1kV cables (Source: KMI Wire and Cable) Fire Resistance Wire for Residential Installation Preparation of Specimens and Testing Apparatus Data Treatment Conclusion DSC test 20 0C per minutes for 20 minutes Flame test Flame temperature = 1285 0C Flame length = 12 cm Current injection test 5A, 10A, 20A, 40A, and 60A Time = 5 minutes JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 47 Figure 3.3 Current Injection Apparatus 3. RESULT AND DISCUSSION 3.1 DSC test result The Differential Scanning Calorimetry test used 10 mg weight specimen. The test gave the result for cable's melting point of 3100C. 3.2 Flame test The flame test was conducted on 600 mm vertical cable by propane torch for 60 seconds and shown that propagation of fire was 65 mm. The fire was shut off after 10 second of fire source's cut off. The fire consumed lower section of the cable along 125 mm of length. The test was shown in Figure 3.1. a. b. c. Figure 3.1 Flame test a. Length of flame, b. temperature of flame, c. flame test 3.3 Current injection test Current injection test was conducted by recording the temperature rise for every 30 seconds and shown that for current of 60 A in 270 seconds the cable started to charred and produced smoke. The specimen of current injection test was given in Figure 3.2. JEMMME, Vol.3, No. 1, May 2018 ISSN 2541-6332 e-ISSN 2548-4281 JEMMME | Journal of Energy, Mechanical, Material, and Manufacturing Engineering 48 Figure 3.2 Specimen of current injection test 4. CONCLUSION In accordance with its specification, i.e. flame retardant wire or fire resistance wire, and from the test results which consisted of measurement of melting temperature, fire propagation, and current injection tests, the conclusion was the wire in the residential wiring installation gives good degree of protection against the fire especially caused by short circuit. In the event of short circuit when the wire receives huge amount of current and high temperature produced, it most likely that the wire only experience charring or melting and the fire will not occurred. In the worst case when the fire may exist, the propagation of fire can be considered not exist. In the future, the research on the analysis of wire material difference claimed to be flame retardant or fire resistance with common wire generally used in residential electricity installation need to be conducted. It is important to do so because the fire in residential area is commonly initiated by short circuit. 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