Under high impulse currents, an earthing system exhibits different impulse characteristics depending on the shape and/or design configuration of the earthing system. These characteristics have been seen to be different with respect to its steady-state as highlighted in many studies. Furthermore, in order to ascertain that a correct design of an electrical system is achieved, it is important to evaluate the impulse characteristics of the earthing system under high impulse conditions. So far little emphasis has been given in previous publications to investigate the characteristics of earthing systems under high impulse conditions by field measurements. For this reason, a rather efficient and reliable technique to solve this problem is by conducting a practical analysis (field experiment). This paper investigates the characteristics of a single rod electrode under high impulse conditions by field measurements under different polarities. The single rod is selected in this paper for its simple configuration and installation. It was observed in this study that the resistance of the single rod earthing system was seen to reduce with increasing current magnitudes for both polarities and negative polarity has higher impulse resitance than that of positive polarity.

Maintaining a safe food supply has become an ever-changing endeavour as some emerging pathogens are discovered. Relying on traditional methods of thermal processing to create microbiologically safe foods is not sufficient. Research on finding other methods of controlling the growth and multiplication of pathogenic and spoilage bacteria needs to be explored. The use of crude bacteriocin produced by lactic acid bacteria may be one promising solution of controlling microbial growth in ready-to-eat (RTE) foods. The ability of lactic acid bacteria (LAB) to produce metabolites with broad-spectrum inhibitory activity that are heat stable is an important criterion for the application of LAB as preservative in food. 'Satar' was used as a model for this study because it is highly perishable and has a short shelf life (<12 h) at ambient temperature and, therefore, is unable to be stored for a long period of time. This chapter briefly describes the background of 'Satar' and its relations to microbiological safety. The study focused on choosing the suitable strains of LAB, identifying the isolates phenotypically using biochemical tests and VITEK 2 Compact System. The isolates were tested on their ability to inhibit LAB microflora, ability to inhibit a broad spectrum of Gram-negative and Gram-positive bacteria and ability to exhibit the antimicrobial activity after being subjected to heating temperatures. Among nine isolates of LAB from fermented fish, supernatants of four isolates were studied extensively for their heat stability at different heating temperatures (70, 80, 90, 100 and 121 degrees C) and heating times (5 and 20 min). Two strains, Lb. acidophilus and Lb. plantarum, were chosen for the incorporation of their crude bacteriocin in raw ' Satar', and their characteristics and microbiological shelf life were evaluated. Incorporation of crude bacteriocin of Lb. acidophilus and Lb. plantarum at 3 % and 6 % did not significantly affect (P>0.05) the water activity and pH, but significantly increased the moisture content when Satar was stored more than 20 h at ambient temperature. There was no significant difference (P>0.05) for a* value and b* value of 'Satar' among all samples at 0 h of storage time, except after 3 h of storage at ambient temperature. The colour analysis of samples showed a range of colour between grey and light grey. The incorporation of 3 % and 6 % crude bacteriocin of Lb. acidophilus and Lb. plantarum in raw ' Satar' could extend the shelf life from 8 h to 20 h and 17 h, respectively. This study has proven that LAB can be used to extend the shelf life of ready-to-eat food.

This paper investigates the effects of current magnitudes, steady-stage earth resistances, R-DC, and threshold electric field, E-c on the characteristics of earthing systems under impulse conditions by using Finite Element Method (FEM). It has been reported in literature that there are three scenarios that can occur when the earthing systems are subjected under high impulse conditions as compared to its steady-state conditions, namely; (i) no difference in its resistance values between steady-state and impulse conditions, (ii) earth resistances under impulse were found to be lower than that at steady-state, and (iii) earth resistances were found to be higher under impulse than that at steady-state. It was found that the largest reduction in impulse resistance occurred for the earth resistance with the highest values for different factors; current magnitudes and Ec. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.

There has been a vast vacuum in the literature on the importance of the location of remote earth carried out during impulse test on grounding systems using field measurements. Some published work show that the remote earth is installed surrounding the electrode under tests, whilst some have used separate remote earth, away from it. This work studies the impact of return electrode location on transient behaviour of the earthing electrode. The electrode under test is a single rod. Two types of remote earth configurations are used, a circular electrode with multiple rods surrounding the single rod, and one that is 80m away from it. Impulse tests are conducted under both impulse polarities. Voltage and current traces are captured for a single rod, using two different types of remote earth configurations, with the impulse resistance measured as well. It has been established that the arrangement of the remote earth poses no influence on the test results. That said, higher oscillations of current traces and higher resistance values have been observed in negative impulse in comparison with positive impulse polarities.

Nowadays, with a good design and available facilities of high impulse generators that can be taken to field sites for measurements, much research work can be found on the field measurement on the study of the grounding under fast transients. Moreover, field tests on earthing systems have become interesting since it can provide the closest scenario of the characteristics of grounding system when fast transient current discharged to the earthing systems. However, the field measurements have some limitations on the standard methodologies that should be adopted during the field measurements. There is also very little being mentioned on the arrangements/values of the remote earth. As generally known, the remote/auxillary earth is important not only for the purpose of discharging any high fault current during the tests on the electrode under tests, but also to ensure that the remote earth is not being included in the measurements, hence affect the accuracy of the measurements. Due to these factors, this paper is to aimed to study how different configurations and resistance values of remote earth on the characteristics of main earthing systems. It was found that different results were obtained when higher earth resistance values of remote earth were used for impulse tests on main earthing systems.