Laser based sensor for determination of outages causes of electrical cables

Abstract

Saudi Electric Company (SEC) is working to improve its underground transmission cable system for electric supply services to its customers. In spite of these efforts, power outages are still happening. These power outages cost huge loss in terms of materials costs, time and labor charges. During this study the causes of underground power cables failures in the western region of Saudi Arabia have been investigated. The major cause for these outages has been identified as the quality of cable, play major role in these outages. Cable industry is trying to improve the quality of cables but still there are many factors affecting the quality such as manufacturing processes, and quality of materials used, weather, and soil environment of the Kingdom. Due to moisture in the soil across red sea and Arabian Gulf coastal region, the outages problem is aggravated. This is due to water penetration into the plastic insulated multi-conductor cables which can seriously effect the electrical properties of such devices/or conductors. The problem of water penetration is amplified when the electrical cable is positioned underground or in a high humidity environment. The water penetration could cause the so called water tree formations due to ionic species present in the cable insulating material under salty moisturized environment. The impurities of ionic species like Na, Mg, K in the insulating layer of cables under moisturized soil could enhance the tree formation process and could cause breakdown between conducting part and the earth. A laser senor based on laser-induced breakdown spectroscopy (LIBS) principle was developed for the measurement of sodium and chlorine which exist in cables and those responsible for absorption of water and water tree formation. For quality testing of different kinds of cables manufactured in the Kingdom of Saudi Arabia various samples such as faulted cables, new manufactured and even the raw materials like PVC used for insulation were analyzed by using laser based technique called LIBS. For spectroscopic analysis of cables the plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm (1 J, 8 ns, 10 Hz) on the polymer cable samples. The laser-induced breakdown spectroscopy (LIBS) results were compared with the results obtained using standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP). The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.03 - 0.6 at 2.5% error confidence.