Effect of power system dynamics on transformer differential protection

Helal, Khaled Arafa; Mansour, Diaa-Eldin Ahmed; Hassan, Abdel Moneim M; Ahmed, Ramadan Aly

doi:10.21608/pserj.2025.366110.1397

Effect of power system dynamics on transformer differential protection

Document Type : Original Article

Authors

¹ Electrical Engineering Department, Faculty of Engineering, Port-Said University, Egypt.

² Electrical Power and Machines Engineering Department, Faculty of Engineering, Tanta University, Egypt.

³ Abo-Sultan Steam Power Plant head sector former, Ismailia, Egypt.

⁴ Department of Electrical Engineering Faculty of Engineering, Port-Said University, Port-said, Egypt.

10.21608/pserj.2025.366110.1397

Abstract

Differential protection is a type of protection scheme used in power system to protect generators, transformers and feeders. the protection principle is based on the comparison of the current entering and leaving the protected equipment. Differential relays are used to protect the equipment against internal faults, the relay give a signal to the circuit breakers to isolate the equipment, and its disadvantages in transformer protection are errors malfunction due to current transformer saturation, ratio mismatch, phase displacement, tap changer changes stray losses, dielectric losses due to stray capacitors, inrush current etc. or external faults with current transformer failure due to saturation or incorrect polarity. the relay does not operate incorrectly as a result of these currents. This paper demonstrates the effect of the power system dynamics voltage and frequency, transformer load, step of tap changer,the excitation current in the transformer. stray losses and temperature on changing the sensitivity of transformer differential relay operating.

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