Naslov
Fault Diagnostic and Protection of Power Transformers Grounded with a Common Grounding Resistor

Autori
Šarić, Marko ; Marić, Predrag ; Masle, Dino ; Fekete, Krešimir

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
Proceedings of 30th International Conference on Organization and Technology of Maintenance (OTO 2021) / Glavaš, Hrvoje ; Hadzima-Nyarko, Marijana ; Karakašić, Mirko ; Ademović, Naida ; Avdaković, Samir, Avdaković, S. - : Springer, 2022, 172-187

ISBN
978-3-030-92850-6

Skup
30th International Conference on Organization and Technology of Maintenance (OTO 2021)

Mjesto i datum
Osijek, Hrvatska, 10.12.2021. - 11.12.2021

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Power transformer protection ; Inrush current ; Circulating currents ; Common grounding resistor ; Single-phase to ground fault

Sažetak
The power transformer is the main and the most expensive component of the power substation, so successful fault diagnostic and protection is an essential part of its maintenance. Protection engineers doing the scheduled maintenance and protection testing need to be familiarized with transient phenomena that can occur in normal operation. Substations with two parallel transformers sharing a common grounding resistor are very frequent in high-voltage networks since a common grounding resistor limits the single-phase to ground-fault current. However, the unfavorable aspect of this type of transformer grounding system is the increased probability of unwanted trips of the transformer protection during the transient operational states, which has the consequence of a supplied low-voltage network outage. Under transformer energization, an appearance of the inrush current can trigger the transformer differential protection as well as circulating current between transformers in parallel operation caused by sympathetic inrush. A single-phase to ground fault in a high-voltage network can cause circulating currents between neutrals of transformers and trip the differential protection too. The paper presents a simulation model of two transformers grounded with a common grounding resistor adequate for transformer transient operational states analysis. Performed simulations of the inrush and sympathetic currents emphasized the diagnosing of the second harmonic distortion dominance in the current spectrum as an efficient tool in the prevention of unwanted trips of differential protection. The analysis of the simulated circulating currents between transformer neutrals in the paper has examined and discussed the proposed solutions for avoidance of unnecessary transformer outage caused by the single-phase to ground fault in a high-voltage network.

Izvorni jezik
Engleski

Znanstvena područja
Elektrotehnika

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