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In this article, a new electro-thermal optimization algorithm is proposed to determine the parallel power cables arrangement to obtain the maximum ampacity. The optimization procedure is based on the imperialist competitive algorithm (ICA). Electrical calculations are performed using the sub-conductors method and consideration of the skin and proximity effects. FEM thermal model and electrical calculations are coupled with optimization procedure to determine the ampacity in the optimization algorithm. Optimized arrangements are determined under sinusoidal and harmonic load currents conditions. Furthermore, the effects of different boundary conditions of the ground surface such as isothermal and convective heat flux are evaluated. The underground single conductor cables with solid bonded metallic sheaths and existing of circulating currents are considered. Cables are considered to be installed adjacent to each other in different rows above each other in flat formations. Also, the artificial bee colony (ABC) optimization algorithm is performed to validate the ICA procedure. Experimental measurement of a case study is carried out for simulation confirmation and the results show good agreement. [ABSTRACT FROM AUTHOR]

This article presents an online diagnostics method to predict critical conditions in ceramic insulators. For this purpose, a variety of experimental tests have been conducted on different kinds of ceramic insulators under different environmental conditions in order to analyze their leakage current. Fast Fourier transform analysis of leakage currents shows a strong correlation between the ratio of the third to fifth harmonic amplitude regarding occurrence of critical conditions and degree of insulator ageing. Therefore, the index of the third to fifth harmonic amplitude is utilized as the detection indicator of critical conditions in ceramic insulators. An increase in the index of the third to fifth harmonic amplitude to more than one represents a critical condition in the insulators and estimates a high probability of flashover occurrence. The obtained results have also shown the viability of the index in insulators monitoring procedures. Training the proposed index to a microprocessor powered device gives ability to the system for online diagnosis of ceramic insulator qualifications, detecting critical conditions, and predicting flashover occurrence. [ABSTRACT FROM AUTHOR]

Porcelain string insulators are widely used in high-voltage transmission lines. Calculation of potential distribution is extensively performed in the design and development of high-voltage insulators. This article applies a three-dimensional electromagnetic analysis program to calculate the potential distribution of 230-kV porcelain suspension insulators under clean and dry conditions. The effects of cross-arm length, number of units, corona ring parameters, and also effects of wind force on the potential distribution along the porcelain suspension insulators are investigated and discussed. The results are useful for analyzing the potential distribution for porcelain suspension insulators. [ABSTRACT FROM AUTHOR]