This paper studies effect of new suggested ferroresonance limiter on controlling ferroresonance oscillation in the power transformer including METAL OXIDE SURGE ARRESTER (MOSA). A simple case of ferroresonance circuit in a three phase transformer is used to show this phenomenon and three-phase transformer core structures including nonlinear core losses are discussed. The effect of MOSA and ferroresonance limiter on the onset of chaotic ferroresonance and controlling chaotic transient in a power transformer including nonlinear core losses has been studied. It is expected that these ferroresonance Limiter generally cause into ferroresonance control. Simulation is done on a power transformer rated 50 MVA, 635.1 kV with one open phase. The magnetization characteristic of the transformer is modelled by a single-value two-term polynomial with q=7, 11. The core losses are modelled by third order in terms of voltage. The simulation results reveal that connecting the MOSA and ferroresonance limiter to the transformer, exhibits a great impact on ferroresonance overvoltages. Significant effect on occurring chaotic ferroresonance, the range of parameter values that may lead to overvoltage and magnitude of ferroresonance overvoltage is obtained and showed.

The essential role of SURGE ARRESTERs is equipment protection against overvoltages to increase system reliability. Different monitoring techniques have been used to diagnose SURGE ARRESTER condition. Leakage current analysis methods by the extraction resistive and capacitive components of leakage current are a conventional method for SURGE ARRESTER monitoring. Insufficient appropriate thresholds are most important restriction of these kinds of methods. In this paper, the impact of pollution, ultraviolet aging and varistors fault on harmonic spectrum of leakage current have been evaluated experimentally. Real tests and examinations have been done on different METAL OXIDE SURGE ARRESTERs to investigate effects of mentioned factors on leakage current harmonics. To show results performance, bees-adaptive network based fuzzy inference system has been applied.

in this paper the optimal placement of spacers in SURGE ARRESTER column is presented in order to achieve temperature reduction and SURGE ARRESTER thermal stability against power losses due to the overvoltage in power system. The simulation is done by using genetic algorithm in MATLAB software that it is linked by numerical analysis, i.e., Finite Element Method (FEM). First, electro thermal analysis is performed according to the IEC60099-4 standard on selected population in certain interval and, then the required data is applied to the genetic algorithm for the optimal placement of spacers. Simulation results show that the placement of spacers has great influence on SURGE ARRESTER temperature variations. Finally, the optimal model of SURGE ARRESTER is simulated in COMSOL software and the results of this model are compared with conventional model results.

Insufficient electrical endurance of equipment and insulation failure against overvoltage are one of the most effective reasons for the failure of the power lines. Lightening, switching, or other disruptive parameters can cause line outage or distribution substation failure. There are different devices used to improve the safety, reliability, and power quality of the system. SURGE ARRESTERs are one of the insulation protection subsystems used against SURGE and switching overvoltages. In this paper, the effects of SURGE ARRESTER performance have been investigated on the insulation system of distribution substation. The study has been done under normal and also transient conditions due to lightning overvoltage. The effects of failure rate, production quality, voltage stress, temperature and SURGE ARRESTER permutation have been evaluated on SURGE ARRESTER performances. The influence of SURGE ARRESTER aging, as the most influential factor on the SURGE ARRESTER performance, has been investigated as one of the factors involved in the present study. Obtained results have verified the great impact of SURGE ARRESTER aging effect on the reliability of protection system.

Due to the ever-increasing use of Distributed Generations (DGs), and special attentions toward wind power plants in recent years, this research investigates the wind plants from the viewpoint of lightning protection. In comparison to all other type of generators connected to the electric power systems, wind turbine generators are placed in areas which are more likely to be stricken by lightning. Lightning damages are divided into two major categories: direct and indirect damages. This paper studies the strategies to reduce the indirect damages o the wind turbine. Modeling of wind turbine components, i.e., blades, towers and connected cables, are frequency-dependent. Lightening ARRESTERs are used to reduce over-voltages caused by lightning currents in wind farms. Lightning ARRESTER placement in wind farm is performed based on the objective function composed of insulation risk constraint and lightning failure and weighting coefficients are considered for the stress-exposed insulation devices. Optimization process is performed using Genetic Algorithm (GA), and finally the simulation results are analyzed.