Search

Increased ratio error of capacitor voltage transformers (CVTs) has been recently encountered in several substations in Iran. The results of the performed diagnostic tests indicate that short-circuited capacitor elements, especially in the low-voltage capacitor, have increased the CVT error. In this paper, some simple and effective techniques are suggested to solve this problem. One of the proposed methods to compensate the increased error is utilization of an auxiliary voltage transformer (AVT), which does not require disassembling the CVT. The practical aspects of this method, its effects on the CVT transient response, and the influence of the AVT improper design on the performance of distance relay are scrutinized in this paper. Furthermore, the design requirements of the AVT to avoid distance relay malfunctions due to the AVT ferroresonance are discussed. [ABSTRACT FROM AUTHOR]

With the increased demand for electrical power, power systems currently need to be operated close to their stability limits, increasing the transient instability probability at power plants. In this situation, FACTS devices can be used effectively because of their capability to improve transient stability. Several studies have been made to assess the effect of FACTS on transient stability. However, these studies have not considered this effect from the economic point of view. Therefore, the aim of this paper is to analyze the economic effects of FACTS on the transient stability of power plants. This will be done by evaluating the effect of the FACTS on the transient instability risk of the power plant. A generic procedure is proposed for this evaluation in this paper. The procedure is then applied to a real case study, Tehran transmission system and the economic effect of a TCSC on the transient stability of a power plant in this system is investigated. [ABSTRACT FROM AUTHOR]

In this paper, a multi-objective function is proposed for optimal placement of the capacitors in radial distribution networks considering the effect of harmonics. In addition to the voltage profile, active losses and installation cost, the resonant phenomenon caused by the harmonics is also included in proposed objective function. The PSO meta-initiative method has been employed in order to optimize the function. A novel approach has been introduced to analyze the harmonic load flow in distribution networks. The proposed method is based on four matrices that are constant during the load flow. Therefore, in this method, the repeater counters and the harmonic frequencies are the only variables. Due to the elimination of backward-forward sweeps in this approach, the calculations are fast and accurate. This method has been implemented on a standard 14-bus system and a real power distribution network in Lorestan province, Iran. Simulation results confirm the accuracy and speed of the proposed load flow method as well as the effectiveness of the proposed method for optimal placement of the capacitors in the harmonic polluted networks. [ABSTRACT FROM AUTHOR]

In this paper, the stationary super-capacitors are used to store a metro network regenerative braking energy. In order to estimate the required energy storage systems (ESSs), line 3 of Tehran metro network is modeled through a novel approach, in peak and off-peak conditions based on the real data obtained from Tehran metro office. A useful method is proposed to predict the maximum instantaneous regenerative energy which is delivered to each station before applying ESS and based on that the ESS configuration for each station is determined. Finally, the effectiveness of the proposed ESS is confirmed by economic evaluations and benefit/cost analyses on line 3 of Tehran metro network. [Copyright &y& Elsevier]