Abstract
In power systems, the programmable numerical differential relays are widely used for the protection of generators, bus bars, transformers, shunt reactors, and transmission lines. Retrofitting of relays is the need of the hour because lack of proper testing techniques and misunderstanding of vital procedures may result in under performance of the overall protection system. Lack of relay’s proper testing provokes an unpredictability in its behavior, that may prompt tripping of a healthy power system. Therefore, the main contribution of the paper is to prepare a step-by-step comprehensive procedural guideline for practical implementation of relay testing procedures and a detailed insight analysis of relay’s settings for the protection of an Extra High Voltage (EHV) auto transformer. The experimental results are scrutinized to document a detailed theoretical and technical analysis. Moreover, the paper also covers shortcomings of existing literature by documenting specialized literature that covers all aspects of protection relays, i.e., from basics of electromechanical domain to the technicalities of the numerical differential relay covering its detailed testing from different reputed manufacturers. A secondary injection relay test set is used for detailed testing of differential relay under test, and the S1 Agile software is used for protection relay settings, configuration modification, and detailed analysis.
Highlights
In modern Extra High Voltage (EHV) power networks, the protection of the power system is continuously being upgraded by the replacement of old electromechanical protection relays with the new microprocessor based numerical protection relays known as Intelligent Electronic Devices (IEDs)
To the best of the author’s knowledge, there is no formal guideline and detailed study available to the research community and power system protection experts that thoroughly discusses the testing procedures for numerical differential relays as a single document. To fill this literature gap, the main purpose of this research work is to prepare and compose a step-by-step detailed manual that can provide a complete guideline for the practical implementation of relay testing procedures and thorough numerical analysis that one can follow to check the health and functionality of a differential protection relay installed at EHV auto transformer
When no fault occurs in the differential protection zone during normal operation of a transformer, the current in differential coils of the differential relay should be equal in magnitude but with 180-degree phase shift
Summary
Umer Ehsan 1,2 , Muhammad Jawad 1, * , Umar Javed 1,3 , Khurram Shabih Zaidi 1 , Ateeq Ur Rehman 4 , Anton Rassõlkin 5 , Maha M. Althobaiti 6 , Habib Hamam 7,8,9 and Muhammad Shafiq 10, *. Riphah College of Science and Technology, Lahore Campus, Riphah International University, Islamabad 54000, Pakistan.
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