Life Science Journal 2013;10(4) http://www.lifesciencesite.com http://www.lifesciencesite.com lifesciencej@gmail.com 369 Comparison Study of Sensitivity Between Three Sensors to Detect Partial Discharge on Natural Palm Oil M.A. Alsaidi*, MM Yaacob, Ahmed Resan, Abdullah J. H. Al Gizi, N. Kamaruddin and S. Hadji Institute of High Voltage and High Current, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia. maliksaady@yahoo.com. Abstract: High-voltage transformer is the most critical and expensive component in a power system network in order to ensure the stability of the system. Partial discharge (PD) detection is a technique widely used for high voltage equipment insulation condition monitoring and assessment. Many researchers have used acoustic emissions (AE) at the vicinity of the discharge zones to detect PD. This paper compares the sensitivity of multimode fiber optical sensor step-index (MMF-SI)and multimode fiber optical sensor graded-index (MMF-GI) with piezoelectric film sensor (PZT). The fiber optical sensor (FOS) and PZT sensors were immersed in an oil tank fitted with two steel electrodes which were connected to different values of high voltage source. The experimental results show that three sensors have peculiar characteristics for the detection of AE and could be used as alternative detection devices. [Kharkwal G, Mehrotra P, Rawat YS. Taxonomic Diversity of Understorey Vegetation in Kumaun Himalayan Forests. Life Sci J 2013;10(4):369-372] (ISSN:1097-8135). http://www.lifesciencesite.com . 48 Keywords: optical fiber sensor, acoustic emission, piezoelectric sensor, partial discharge, natural palm oil. 1. Introduction PD has attracted much attention due to the high financial outlay needed to repair the damage it causes. A high voltage network system (HVNS) has a number of heavy transformer installations which continuously work to distribute electricity to substations. Stability of any power system network determines the life time of the high voltage equipment installed in the network. The expensive components of the high voltage equipment are the power transformers which are expensive and can incur high repair costs. Each fault on a single unit of the heavy transformer installations has a huge financial impact on the maintenance cost of the installations. Hence, continuous operational monitoring is very important. Failures due to PD cause deterioration of the HVNS performance and result in breakdown, fires and damage to the system. PD detection technique is widely used for high voltage equipment protection, insulation condition monitoring and general high voltage network assessment. Hence, a good understanding of PD mechanisms, its characteristics and development processes are important. Insulation of the HVNS has a high risk for dielectric stability when PD occurs. Therefore, continuous measurement and monitoring of PD is important so that preventive actions can be taken to avoid equipment damage. At the present moment, modern testing procedures are available to monitor high voltage insulation in the HVNS. There is now a new trend to monitor high voltage insulation using sensitive predictive diagnostic tools. PD results in many different physical phenomena such as electromagnetic emission (in the form of radio wave, light or heat), acoustic emission (in the audible and ultra-sonic ranges), ozone formation and nitrous oxide gas discharges. PD occurs when the insulation of HVNS deteriorates or degrades. For this reason, it has been used as a tool to predict and detect possible insulation failure of the system (Tenbohlen, 2008). The frequency and intensity of PD are the main quality criteria to estimate the life span of the HVNS. In this paper comparison study of sensitivity between three sensor have been described. 2. Acoustic and optical methods for PD detection 2.1 The Acoustic Method Acoustic method takes advantage of the fact that all PDs result in localized and nearly instantaneous release of energy, appearing as a small ‘explosions’, which are point sources of acoustic waves. When the wave propagates in all directions, it can be detected and analyzed by a suitable sensor with the help of data acquisition equipment. One of the most obvious advantages of acoustic PD detection is that it is a real-time and on-line method. In the acoustic method, the detector locates the site of PD by studying the amplitude attenuation or phase delay of the acoustic waves. PD generates mechanical wave (acoustic wave) which is propagated in a radial manner along the medium from the site of discharge. The acoustic wave is produced by the explosion of mechanical energy due to the vaporization of material inside the transformer tank forming a pressure field (Smith, 2004), (Lundgaard, 1993), (Tilman, 2000), (Harrold,1979), (L. M.,1992). The acoustic wave which travels in the transformer oil can be detected using acoustic sensors. For the acoustic method the acoustic wave is capture and detected using piezoelectric (PZT)