Lightning Breakdown Voltage Evaluation of Palm Oil and Coconut Oil as Transformer Oil under Quasi-Uniform Field Conditions

Nurul Katim,Nur Mohamad Amin,Mohd Ishak,Khairol Amali Ahmad,Norhafiz Azis,Mardhiah Abdul Hamid

doi:10.3390/en11102676

Abstract

This paper presents lightning (1.2/50 µs) breakdown voltages of palm oil (PO), coconut oil (CO) and mineral oil (MO) in a quasi-uniform sphere to sphere electric field at two gap distances. The type of PO used in this study is Refined Bleached Deodorized Palm Oil (RBDPO) Olein type. The effect of voltage polarities (positive and negative) and testing methods (rising voltage, up and down and multiple level) on the lightning breakdown performance were investigated. The results indicated that lightning breakdown voltages of CO and RBDPO are comparable to those of MO under various test conditions. The results indicated that there is no polarity effect for lightning impulse breakdown tests in a quasi-uniform field. The testing methods, including rising voltage method, up and down method and multiple level method have a notable influence on the breakdown voltages. The effect of the 50% breakdown voltage on rising voltage method, up and down method and multiple level method for RBDPO and CO is comparable to MO. The withstand voltage at 1% and 50% breakdown probabilities were obtained using the Normal distribution fitting on the cumulative probability plot of impulse shots. Based on a normal distribution fitting, withstand voltages 1% breakdown probability of POA were close to the MO. Finally, based on statistical studies and simulation using ANSYS software, the prediction formulas for breakdown voltage for larger gap distances for all samples were derived.

Highlights

Application of vegetable oils in power transformers has been investigated intensively in the past few decades [1,2,3,4,5,6,7,8]
Impulse breakdown voltages of three types of palm oil (PO), coconut oil (CO) and mineral oil (MO) for transformer insulation liquid in a quasi-uniform electric field were investigated by considering the influences of voltage polarity and in a quasi-uniform electric field were investigated by considering the influences of voltage polarity testing method
The results indicated that there is no polarity effect for lightning impulse breakdown and testing method

Summary

Introduction

Application of vegetable oils in power transformers has been investigated intensively in the past few decades [1,2,3,4,5,6,7,8]. Vegetable oils produced from palm oil (PO) and coconut oil (CO) are being considered as dielectric liquids in transformers. Both these oils are biodegradable and non-toxic, which makes them desirable for transformer applications. A number of studies had been carried out on PO and CO covering different aspects such as their dielectric, chemical and physical properties and ageing characteristics [8,9,10,11,12,13,14]. There are different types of PO that can be obtained from palm nuts. These are Crude Palm Oil (CPO), Palm

Methods

Results

Conclusion