DocumentCode :
1612838
Title :
Study of transformer resonant overvoltages caused by cable-transformer high-frequency interaction
Author :
Gustavsen, Bjørn
Author_Institution :
SINTEF Energy Research
fYear :
2011
Firstpage :
1
Lastpage :
1
Abstract :
Summary form only given. Power transformers can fail from dielectric stresses caused by electromagnetic transients. In this paper we focus on a special phenomenon where excessive overvoltages arise due to resonance. This situation can take place when a transformer on the high-voltage side is connected to a cable and the low-voltage side is unloaded. Very high overvoltages can then result on the low-voltage side from transient events that cause a weakly attenuated overvoltage on the cable with a dominant frequency matching a resonance peak in the transformer voltage ratio. Laboratory tests on a 11 kV/230 V distribution transformer show that a step voltage excitation on a 27-m cable produces a 24 p.u. overvoltage on the open low-voltage side. The voltage waveforms are accurately reproduced by a black-box model obtained from frequency sweep measurements. Simulations show that overvoltages as high as 43 p.u. could occur with the most unfavorable cable length. It is further shown that the following situations can lead to high overvoltages on an unloaded transformer low-voltage side: 1) ground fault initiation at the far cable end, 2) cable energization from a busbar with several other cables connected, and 3) cable energization from another cable of same length.
Keywords :
busbars; dielectric properties; earthing; frequency measurement; overvoltage; power cables; power system transients; power transformer testing; black-box model; busbar; cable energization; cable-transformer high-frequency interaction; dielectric stress; distribution transformer; electromagnetic transient; frequency matching; frequency sweep measurement; ground fault; laboratory tests; power transformer; size 27 m; step voltage excitation; transformer high-voltage side; transformer resonant overvoltages; transformer voltage ratio; unloaded transformer low-voltage side; voltage 11 kV; voltage 230 V; voltage waveforms; weakly attenuated overvoltage; Frequency measurement; Laboratories; Power cables; Power transformers; Resonant frequency; Surges; Voltage measurement;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Power and Energy Society General Meeting, 2011 IEEE
Conference_Location :
San Diego, CA
ISSN :
1944-9925
Print_ISBN :
978-1-4577-1000-1
Electronic_ISBN :
1944-9925
Type :
conf
DOI :
10.1109/PES.2011.6038890
Filename :
6038890
Link To Document :
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