Abstract: The performance of an embedded grounding system is very important for the safe operation of electrical appliances and human beings. In principle, a safe grounding system has two objectives, which are to dissipate fault current without exceeding any operating and equipment limits and to ensure there is no risk of electric shock to humans in the vicinity of earthed facilities. The case studies in this paper present the calculating grounding resistance for multiple configurations of vertical and horizontally by using a simple and accurate formula. From the analytic calculated results, observed good/empirical relationship between the grounding resistance and length of the embedded grounding configurations. Moreover, the configurations of vertical and horizontal observed effectiveness of grounding resistance and good agreement on the reduction of grounding resistance values especially for vertical configuration.
Abstract: A multiphase harmonic load flow algorithm is developed based on backward/forward sweep to examine the effects of various factors on the neutral to earth voltage (NEV), including unsymmetrical system configuration, load unbalance and harmonic injection. The proposed algorithm composes fundamental frequency and harmonic frequencies power flows. The algorithm and the associated models are tested on IEEE 13 bus system. The magnitude of NEV is investigated under various conditions of the number of grounding rods per feeder lengths, the grounding rods resistance and the grounding resistance of the in feeding source. Additionally, the harmonic injection of nonlinear loads has been considered and its influences on NEV under different conditions are shown.
Abstract: This study describes analysis of tower grounding
resistance effected the back flashover voltage across insulator string
in a transmission system. This paper studies the 500 kV transmission
lines from Mae Moh, Lampang to Nong Chok, Bangkok, Thailand,
which is double circuit in the same steel tower with two overhead
ground wires. The factor of this study includes magnitude of
lightning stroke, and front time of lightning stroke. Steel tower uses
multistory tower model. The assumption of studies based on the
return stroke current ranged 1-200 kA, front time of lightning stroke
between 1 μs to 3 μs. The simulations study the effect of varying
tower grounding resistance that affect the lightning current.
Simulation results are analyzed lightning over voltage that causes
back flashover at insulator strings. This study helps to know causes
of problems of back flashover the transmission line system, and also
be as a guideline solving the problem for 500 kV transmission line
systems, as well.