MONITORING UNDERGROUND CABLE CONDITION UTILIZING THIRD HARMONIC CURRENT

Power failure in a power system caused by unscheduled cable failure may give significant problem to the utility company and to the consumers. This unscheduled cable failure can be overcame by periodically monitor the cable condition. There are many ways to monitor cable condition such as visual inspection, infrared thermography, ultrasound, insulation resistance and others. Third harmonic in triplen harmonics may also be used to monitor cable condition. Lab experiments have been conducted to investigate the relationship of third harmonic voltage and current passing various cable conditions that specifically affected by their insulation. The objective of this research is to study the applicability of using third harmonic to monitor cable condition. Preliminary research is done to collect necessity information and vigorous lab with different loads is initiated to achieve the objective. Further discussion is made to come out with a conclusion of the project and recommended steps are listed for future development. The results show a significant existence of third harmonic voltage and current at the phase line and the value at the neutral line is three times from the phase line. Connection of transformer (delta-wye) will only circulate the third harmonic current at delta connection from flowing continuously into the wye connection and the load. The third harmonic flows through a capacitor significantly at a range value of 1uF to 2uF.