Showing 3 results for Voltage Distribution
E. Akbari, M. Mirzaie, M. B. Asadpoor, A. Rahimnejad,
Volume 9, Issue 1 (3-2013)
Abstract
Insulator strings with several material and profiles are very common in overhead transmission lines. However, the electric field and voltage distribution of insulator string is uneven which may easily lead to corona, insulators’ surface deterioration and even flashover. So the calculation of the electric field and voltage distribution along them is a very important factor in the operation time. Besides, no remarkable endeavor regarding insulator material and profile and their impacts upon the electric field and voltage distribution has been made so far. In this paper several 230-kV insulator strings with different porcelain and glass units were simulated using 3-D FEM based software, and their electric fields and voltage distributions were calculated and compared together, to investigate the effect of insulator types on these quantities. Tower and conductors were included in all simulations and also the effect of corona ring on voltage and electric field distribution over insulator strings with different insulator types was investigated. Reported results show the dependency of voltage distribution to insulator material and profile.
M. Khodsuz, M. Mirzaie,
Volume 10, Issue 2 (6-2014)
Abstract
Metal oxide surge arresters (ZNO) are used widely in power system to protect equipments from over voltages. Non uniform potential distribution leads to the depressed service life and low safe reliability, so grading ring is applied on HV surge arrester order to uniform the electric field distribution. One of the problems of arresters is leakage current in power frequency that different parameters such as internal structure of varistors, heat sinks, grading ring can be influence on leakage current.
In this paper Maxwell and EMTP/ATP software has been applied to calculate the electric field, voltage distribution and leakage current in a high voltage surge arrester. First Maxwell is used to calculate the electric field and voltage distribution of a 230kV surge arrester with and without grading ring. Then equivalent circuit of surge arrester has been achieved by applying Maxwell software for 230kV surge arrester and extracting stray capacitances. The derived equivalent circuit has been simulated in EMTP/ATP software for evaluation of leakage current. Also in this work, the effect of grading ring dimensions and number of heat sinks on leakage current variation has been investigated. Results show grading ring dimension and heat sinks number impact on arrester leakage current.
M. Heidarzadeh, M. R. Besmi,
Volume 10, Issue 2 (6-2014)
Abstract
Overvoltage distribution along the transformer winding must be uniform to certify the safety of the operation of the power transformer. Influence of the parameters variation on the impulse voltage distribution (IVD) in disk winding transformer is going to be analyzed which hasn’t been analyzed on this type of winding in the previous papers. In this research, a transformer with disk winding and rectangular cross-section is analyzed. Equations for capacitances between winding turns and also equations for capacitances between turns and core are deduced. Noting that the relationships presented are dependent on the parameters of the transformer winding, so with changing these parameters, the capacitances of turn –turn and turn – core and finally the capacitances of total series and parallel of the winding will be changed. The purpose of this paper is to show the effect of the variations of these parameters on the IVD in disk winding of transformer. This paper, will assess how to change the parameters of disk winding in order to achieve a uniform initial IVD along the winding and to reduce the amplitude of impulse voltage fluctuations (AIVF) in winding and which parameters have more effect in making uniform the IVD on the disk winding.
