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Power transformers are of the most critical and expensive equipment in the power system industry. Meanwhile, they are exposed to a variety of faulty and abnormal operating conditions. Therefore, to prevent extension of these events they are protected by different protective schemes. Among the various types of the transformer faults, detecting turn-to-turn faults is the most challenging one for the protection systems. Industrial experiences and standard documents reveal that the existing protection systems include severe shortcomings, and still more efforts are required to offer a reliable method for detecting such faults. To this end, this article puts forward the proposal of a novel turn-to-turn fault detection method to satisfy the basic protection requirements of dependability, security, and speed. This method properly detects the low-level turn-to-turn faults while is stable during system transients and external faults. Performance of the proposed method is evaluated through various experimental and simulation studies. The obtained results verify superior operation of the proposed method under different faults and conditions. [ABSTRACT FROM AUTHOR]

Frequency-response analysis (FRA) is an efficient method to examine the mechanical integrity of a power transformer. Different connection schemes can be implemented for measuring frequency responses. Moreover, the use of different terminating resistors and measurement impedances is possible. This paper investigates the influence of the measuring technique on the sensitivity of FRA traces. Consequently, different FRA traces are measured using two experimental windings, while specific mechanical changes, axial displacement, disc space variation, and radial deformation are applied to the windings. Six different resistors are utilized for termination and as the measurement impedance in the experimental setup. Two numerical indices are also employed to compare the sensitivity of the traces. The results of the sensitivity analysis are also validated with a circuit model of the windings. The points concluded can play a valuable role in defining the best FRA configuration for the detection of mechanical deformations. [ABSTRACT FROM AUTHOR]

The frequency response analysis (FRA) is an effective method to detect the existing mechanical faults inside transformers. Some mechanical failures are due to the loss of press ring pressure and, therefore, detection of pressure loss can save the transformer from subsequent damage. This letter proposes a novel idea to evaluate the pressure of the press ring using the FRA. In this idea, after temperature stimulation, the FRA traces of different temperatures are compared without any need of a fingerprint from the past. The experimental results also support the functionality of the idea and show its early potential. [ABSTRACT FROM PUBLISHER]

This letter deals with decreasing the impact of the measurement uncertainty in the frequency response analysis (FRA) interpretation. The experimental data are employed to first select the best indices and connections from the aspect of uncertainty susceptibility. In addition to implementing preferable indices and connections, comparing the FRA traces of two configurations with each other is proposed as an extra criterion to strengthen the FRA interpretation against uncertainties. [ABSTRACT FROM PUBLISHER]

The Rogowski coil is an old device for current measurement. It has been modified and improved over a century and is still being studied for new applications. The Rogowski coil has various advantages over conventional magnetic current transformers (CTs). Not only can it be used instead of CT, but also it has various utilizations in other fields. This paper provides a brief review on different aspects of the Rogowski coil and its advancement procedure, during last decades. In this paper, the history of the coil is brifely reviewed and its bases and applications are discussed. The Rogowski coil is analyzed from different points of view, including different integration techniques in the output stage, models for the Rogowski coil, experimental methods for parameter measurement in models, and method for determining the damping resistor. Finally, a brief review over different applications of the coil ends this paper. [ABSTRACT FROM PUBLISHER]