Papers by Keyword: Earth Resistance

Abstract: In high voltage substation, earthing system is an essential part not only for providing the protection to people who are working or walking in the vicinity of earthed facilities and equipment against the danger of electric shock, but also for maintaining the proper function of the entire electrical system. By selecting a proper conductor and electrode size based on standard criteria, the existence of large potential differences during fault or lightning conditions will able to be avoided. Standard equations for earthing are used in the design to obtain the desired parameters such as tolerable touch and step voltage, earth resistance, grid resistance, minimum size of earthing conductor and electrode, as well as resistivity of soil. Therefore, it would enable the establishment of the safe limits of potential differences under both normal and fault conditions. The main objective of this research work is to perform a necessary background information pertinent step by step approach for safe and reliable earthing system design for high voltage distribution substation in Malaysia. It including a set of applicable standard to be used as well as demonstrate an earthing design simulation developed using Microsoft Excel auto mathematical functions. The case study for high voltage substation design and simulation at two locations with different soil resistivity and properties is also performed in this research work. The results revealed that the design of high voltage substation earting system is much dependent on the property and resistivity of soil where the substation will be constructed.

Abstract: The double-circuit transmission lines have already been the significant component of power system. Because of the symmetric insulation of the two circuits, the case that both circuits trip out often happens when the tower suffer lightning strike. And it harms the stability of power system and causes serious impacts to power equipments. In this paper, an electric-magnetic transient simulation model was established. Using this model, combining the analysis of physical mechanism of back striking trip-out, the influences of earth resistance, height of tower and length of insulator on the lightning withstand level of back striking (LWLBS) were clarified. The LWLBS of high tower is much low, therefore the relative high tower should be paid more attention to defense the back striking. Reducing the earth resistance and increasing the length of insulator can both upgrade the LWLBS observably. Especially, reducing the earth resistance can enhance the effect of upgrading the LWLBS by increasing the length of insulator.

Abstract: As the number of delicate semiconductor devices in the electric equipment increases, it is also getting more important to prohibit the surge wave from intruding the equipment. The better surge-wave protection can be achieved when we reduce the earth resistance further in the earthing system. It is practically best, however, to set an appropriate value of earth resistance if we consider the cost and effort required to install the earthing system. In this work, we demonstrated an example of extracting an optimized earth resistance by using a simulator that theoretically predicts the evolution of discharge current of the earthing system. The measure discharge currents of the real earthing system with the optimum earth resistance has confirmed that our method was efficient and useful.