Can the Exploitation Short Circuit Current of the Transformer be More Dangerous than the Standardized one?

Abstract

This article presents the standarised short-circuit test current compared with the accidentally occuring one during expoloitation of a 3-phase transformer. The methodology of performing this test for a new transformer is described in the Polish standard PN-EN 60076-5. Taking the example of distribution transformer 16 MVA, 115/20kV, which malfunctioned, emergency exploitation short circuit and a standardized short circuit have been compared. Emergency 2-phase short circuit current occurred on the discharge cable, broken by an excavator at a distance of 0.78 km from the transformer. Based on the equivalent circuit of the transformer together with the cable, the article presents calculations of the surge currents and the level of overvoltage induced in the winding during arc suppression.

Keywords

3-phase transformer, standardized short circuit, emergency short circuit test

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Bilbiography

[1] T. Glinka: "Maszyny elektryczne i transformatory. Podstawy teoretyczne, eksploatacja i diagnostyka". Wyd. INiME Komel. 2015. ISBN 978-83-931909-1-1

[2] PN-69/E-06040. Transformatory. Wymagania ogólne.

[3] PN-83/E-06040. Transformatory. Wymagania ogólne.

[4] PN-EN 60076-5 z 2006 roku. Transformatory. Wytrzymałość zwarciowa.

[5] PN-EN 60076-5 z 2009 roku. Transformatory. Wytrzymałość zwarciowa.