OMICRON Magazine

Magazine | Issue 1 2019 exciting unit measurement In order to illustrate the PSTs ability to regulate the mag- nitude of the quadrature voltage we measured the volt- age ratio of all the exciting unit’s tap positions. Figure 3 shows the ratio changing between approximately 4.5 to 54 for positions 1 through 12 and vice versa for positions 12 through 25. Positions 13A through 13B are the change-over selector’s positions for switching the regulating winding’s polarity and therefore the direction of the phase shift between the source and load side. Conclusion Phase-shifting transformers (PSTs) are an important part of today’s synchronous power networks. Due to the changing infrastructure of power generation, they are likely to play a key role in ensuring the reliability of power grids in the future. As PSTs are usually installed at critical nodes in the network, the time for off-line main- tenance should be kept as short as possible. The results have shown that using a three-phase transformer test system is a very fast and efficient way of verifying the operation parameters of a PST during commissioning and maintenance in the field. By looking at the example of a symmetrical PST, we have shown that the described methods are suited to verify the operational principles of series and exciting units during factory acceptance testing. The same approach can also be used for an asymmetrical PST. «As PSTs are usually installed at critical nodes in the network, the time for off-line maintenance should be kept as short as possible.» 33

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