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Lightning caused overvoltages on power transformers recorded by on-line transient overvoltage monitoring system

Samir Keitoue ; Končar - Electrical Engineering Institute Inc., Zagreb, Croatia
Ivan Murat ; Končar - Electrical Engineering Institute Inc., Zagreb, Croatia
Božidar Filipović-Grčić ; University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia
Alan Župan ; Croatian Transmission System Operator Ltd., Kupska 4, 10000 Zagreb, Croatia
Ivana Damjanović ; University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia
Ivica Pavić ; University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia

Sažetak

Transient overvoltages generated by lightning strikes or switching operations represent
a significant risk to bushings and windings of power transformers. They cause stress on the
insulation system and can, over time, cause dielectric failure and damage to power transformers.
Many transformer failures are reported as dielectric failures and they are not necessarily linked
to any particular event when they occur but may be the result of prior damage from transient
overvoltage events. Lightning and switching overvoltage waveforms appearing at transformer
terminals in real operating conditions may significantly differ from standard impulse voltage
waveforms used during laboratory testing. The number and amplitudes of overvoltages which
stress the insulation depend on various parameters such as the lightning strike density in the
considered area, since it determines how often the transformer is stressed by lightning
overvoltages. Since the overvoltage amplitudes at transformer terminals are usually unknown,
an on-line overvoltage transient recorder can be used with the ability to sample, analyse and
store transients in real-time.
In this paper, an on-line transient overvoltage monitoring system (TOMS) for power
transformers is presented that is capable to continuously record in real-time various kinds of
transient overvoltages such as lightning or switching overvoltages. Special attention is paid to
lightning caused transient overvoltages recorded at the terminals of 150 MVA power
transformer. Recorded waveforms originating from lightning strikes to overhead lines are
correlated with data from the lightning location system (LLS) and supervisory control and data
acquisition (SCADA) system. Collected data about overvoltage stresses can be used as the basis
for the assessment of the transformer insulation condition, estimation of health index and for
analysis of various kinds of events such as faults or equipment failures.

Ključne riječi

On-line transient overvoltage monitoring system; power transformers; lightning overvoltages; lightning location system

Hrčak ID:

213483

URI

https://hrcak.srce.hr/213483

Datum izdavanja:

1.8.2018.

Posjeta: 1.566 *