In English

Elkvalitet på Ringhals

Olof Carlund ; Johannes Johansson
Göteborg : Chalmers tekniska högskola, 2015. 41 s.
[Examensarbete på grundnivå]

Due to upcoming modernization projects, Ringhals desires an estimation of the current power quality in their local power supply. The purpose of this thesis is to initially, clearly describe, the meaning of the term power quality and what it is that might affect it. As part of the basis for the analysis part of this project lays existing measurement data from an earlier project within Ringhals. There is also an additional measurement carried out within this project of a potential source of harmonics, the thyristor rectifier. This project focuses on phenomena in form of voltage dips, transients and harmonics. When analyzed during normal operation there is no sign of notable levels of either of these phenomena with one exception for the measurement at the 21.5 kV-level, where there is a clearly visible third harmonic, approximately 3.65 %. However, it is isolated to this level in the plant due to the delta coupling of the transformers and the source is probably the main generator. In addition, the loads are connected between phases, so this means they are unaffected by the 3rd harmonic. When measuring the thyristor rectifier the magnitude of the fifth harmonic increased with the load, but due to limited loading options it was not possible to investigate it further. When analyzing data from triggered events, there was a distinct voltage dip at all measured levels in the plant due to a lightning event in the national 400 kV transmission grid at some distance from the plant. At the lowest mark the remaining phase voltage was approximately 67 %, this at the 400 kV-level, which is just under the limit that the plant shall be able to handle momentarily (70 %). The voltage dip is reduced a bit when propagating downwards in the plant and at the lowest point of measuring; the remaining phase voltage is about 76 %. The measurements also showed a heavy motor start and compared to the calculations done in the hypothesis, the voltage dip obtained through theory matches the measured values, 15.7 % respectively 15 %. The main conclusion of this thesis is that Ringhals local power supply is very solid and the only time during this project that there was anything close to a problem, was the voltage dip due to the lightning event.



Publikationen registrerades 2015-08-14. Den ändrades senast 2015-08-14

CPL ID: 220624

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