Abstract
Conventional second harmonic current restriction approach is an adopted method which has been implemented to transformer differential protection schemes. Because of unreliable nature of this approach in discrimination between inrush current, internal faults and external faults and due to the saturation of current transformers, we present new features of the differential protection scheme. This helps to determine the feasibility and applicability of the proposed approach in differential protective scheme for power transformer. The Current Transformer Saturation (CTS) phenomenon issue and its revelation is one of the most significant problems in power system protection particularly in the differential protection. In this paper, the saturation phenomenon and its effects on the differential protection are analyzed. Prevalent algorithms in digital signal processing which are implemented in power system cannot correctly recognize this phenomenon. Mal-operation of differential protection relay takes place when saturation in CT is appeared. This paper presents a Third-Difference Algorithm (TDA) for CTS recognition. In order to make comparison between the presented approach and prevalent digital protective algorithm, an identical case study is simulated. Simulation results also show that the TDA is both satisfactory and consistent with expectation. Keywords: Current transformer, Saturation phenomenon, Third-difference Algorithm, Internal and external faults.
Highlights
Introduction collapse to a low value and the first difference has a Current transformer is a prevalent phenomenon small value at the start of saturation
An algorithm for calculating the core flux using the arrangement which occurred in core design. This secondary current was suggested by Kang et al (1997)
But relied on the During a fault, the secondary current signals may be assumption that the residual flux was zero when the fault distorted by CST which could result in the mal-operation occurred (Kang et al, 2004)
Summary
Discrimination between internal faults and inrush current phenomena in power transformers Bahram Noshad1*, Mohammad Sadegh Javadi[2] and Ali Esmaeelnejad3 1*Department of Electrical Engineering, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran 2Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Fars, Iran 3Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Fars, Iran
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