Canadian transformer manufacturer PSI Transformers received the order to replace a transformer for a hydropower station. The new transformer had to be able to switch between one transmission line at 250 kV and another at 143 kV. The test voltage required was a massive 1,000 kV. "To build a tap-changer for such extreme requirements, from our point of view, there was only one supplier we wanted to work with – and that was Reinhausen," states George Partyka Jr., Vice President of PTI Transformers.
Oversized de-energized tap-changers
If a de-energized tap-changer has to maintain a huge test voltage of 1,000 kV and switch 112 kV in a single step, you need real experts. That is why Canadian transformer manufacturer PTI came to Reinhausen.
Oversized de-energized tap-changers
If a de-energized tap-changer has to maintain a huge test voltage of 1,000 kV and switch 112 kV in a single step, you need real experts. That is why Canadian transformer manufacturer PTI came to Reinhausen.
The power of the transformer depends on the tap changer. Therefore, we needed to work closely with our developers.
There was no doubt at all in the mind of the Canadian manager that Reinhausen could bring its technical know-how and expertise to bear in building a de-energized tap-changer to this specification. The largest de-energized tap-changers in Reinhausen's portfolio measure three meters in length and one meter in diameter. Producing equipment on this scale has put the experts from Regensburg on the world map. No other supplier includes tap changers of this size as standard in its portfolio. But it was obvious that it wouldn't be easy. Karl-Heinz Sperger, who led the project on the Reinhausen side, was also aware of this. "While our de-energized tap-changers are huge, there are still certain restrictions on the space we have to work with, and we can't just increase the distance between the contacts as much as we'd like. That made the physics of this project and what was technically feasible a real test."
Switching step of 112 kV at 1,000 kV test voltage
Another significant factor contributing to the complexity of the project was the transmission ratio of 1:1.78. Switching 143 kV to 250 kV in a single step requires six high-voltage winding strands – for each phase. For PTI Transformers, this meant housing 18 windings and three of the massive tap changers within the transformer, something which, as PTI Transformers Manager Partyka explained, was only possible with Reinhausen's support. "The transformer power is highly dependent on the tap-changer capacity, so the development departments working on the tap-changer design and the transformer design had to work together very closely. Only as a team was it possible for us to coordinate the winding configuration with the special design of the tap-changer."
The physical limits
3000
millimeters long
1000
millimeters in diameter
1:1.78
transmission ratio
1,000
kV test voltage
112
kV in one switching step
Check in the test lab
The PTI Transformers and Reinhausen experts completed this complex development task in a mere three months, meaning that the order was placed and the de-energized tap-changers could go into production in February of 2019. The technicians were then able to construct the three special pieces of equipment in just five days. "Because we insist on delivering 100% quality, the tap changers were then sent to our test laboratory," says Sperger, an electrical engineer himself. There, it was found that the engineers had delivered on their promises.
